Patent Grant
11541654
The present invention relates to an inkjet recording device and a method for controlling an inkjet recording device.
In an inkjet recording device used for industrial purposes, an ink continuously ejected is changed into ink particles by a nozzle body, an electric charge corresponding to printing characters is then applied to the ink particles by a charging electrode, the ink particles charged with the electric charge are changed by a deflection electrode to fly, and the ink lands on a printing object to print the characters. In the printing, the homogeneity of the ink particles ejected from the nozzle body greatly affects the printing quality. In order to maintain the homogeneity of the ink particles, it is necessary to regulate the ink viscosity in a range in which characters can be normally printed.
JP S58-16851 A (Patent Document 1) discloses the background art related to the technical field. In this publication, a preheating device is provided in an ink tube at the previous stage of a print head, and control is performed such that an ink which flows into the print head at an ink temperature is preheated (heated) to cause the ink temperature to reach a set value (for example, 15° C.)
Various types of inks are used in the inkjet recording device, and in the case of an ink having a large gradient in relationship between ink temperature and ink viscosity, the temperature range is narrow in which the ink viscosity can be controlled to an ink viscosity which enables normal printing. When an ink is used of which the temperature range is narrow in which the ink viscosity that enables normal printing can be reached, the range of ink temperature control by a heating device also is narrow. In addition, in a case where ambient temperature exceeds the set temperature, even when the ink viscosity changes due to the ambient temperature, the ink viscosity cannot be controlled by temperature. Namely, in the technique of Patent Document 1, there is no means for lowering the ink temperature when ambient temperature exceeds a set temperature value, and the ink temperature rises with a rise in ambient temperature, so that the temperature cannot be controlled. When due to a decrease in ink viscosity by the temperature rise, the ink viscosity exceeds the range in which normal printing can be performed, due to the exceedance, both the ejection speed of the ink ejected from a nozzle and the character size change, so that normal printing cannot be performed.
Meanwhile, it is known that the regulation (control) of the ink viscosity is performed by adjusting the amount of a solvent included in the ink. The viscosity of the ink stored in an ink container is detected by a viscometer, and when the detection value is out of the range of ink viscosity (normal range) in which normal printing can be performed, the solvent is supplied to control the ink viscosity of the ink. However, since the ink viscosity control depends on the supply of the solvent which is an intensifying liquid, a large amount of the solvent (intensifying liquid) is used. In addition, in the viscosity control by the supply of the solvent, it takes a lot of time for the ink viscosity to reach a normal value, which is a problem.
Therefore, an object of the present invention is to provide an inkjet recording device and a method for controlling an inkjet recording device, which are capable of reducing the amount of use of a solvent and controlling the ink viscosity in a normal range.
In order to solve the above problem, according to one example of the present invention, there is provided an inkjet recording device including: a nozzle that atomizes an ink to eject ink particles; a charging electrode that charges the ink particles, which have been ejected from the nozzle, to correspond to a printing character; a deflection electrode that deflects the charged ink particles which have passed through the charging electrode; a gutter that captures a non-charged ink; an ink supply path that supplies the ink in a main ink container to the nozzle; an ink recovery path that recovers the non-charged ink, which has been captured by the gutter, to the main ink container; a solvent replenishment unit that supplies a solvent to the main ink container; and a control unit that controls an entirety of the device. A heating device that is installed between the ink supply path and the nozzle to heat the ink, a thermometer that detects an ink temperature of the ink heated by the heating device, and a viscometer that detects a viscosity of the ink in the main ink container are provided. The control unit controls the heating device based on the temperature detected by the thermometer such that the temperature reaches a set temperature set in a range of an ink viscosity which enables printing, and controls an amount of supply of the solvent based on a detection value of the viscometer to regulate the viscosity of the ink in the main ink container to a predetermined ink viscosity.
According to the present invention, temperature control can be performed by the heating device to suppress the amount of use of the solvent and control the ink viscosity in the range which enables normal printing.
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Incidentally, the present invention is not limited to the embodiments to be described below. In addition, incidentally, in the drawings referenced in the following description, the same reference signs (numerals) are used for common devices and components, and the description of each device and component which have already been described may be omitted.
Next, a first embodiment of the present invention will be described with reference to the drawings.
(Description of Entire Configuration)
First, a configuration of the inkjet recording device in the first embodiment of the present invention will be described.
In
The ink 2a is changed into ink particles by the nozzle 9, and the ink particles flow to a printing object 26 via a charging electrode 23 and a deflection electrode 24, and printing is performed. In the charging electrode 23, the amount of electric charge corresponding to printing characters is applied to the ink particles. The ink particles are deflected according to the amount of electric charge by the deflection electrode 24 to fly and land on the printing object 26.
On the other hand, non-charged ink particles (ink particles to which electric charge is not applied by the charging electrode 23) which are not used for printing travel straight and are captured by a gutter 11. The ink captured by the gutter 11 is recovered to the main ink container 1 via an ink recovery path to be reused. Namely, the gutter 11, a recovery pump 29, and the main ink container 1 are connected to each other by an ink recovery pipe 13. Accordingly, the ink captured by the gutter 11 can be recovered to the main ink container 1.
The viscosity of the ink 2a (ink viscosity) in the main ink container 1 is measured (detected) by a viscometer 14 that measures (detects) the viscosity of the ink. The viscometer 14 in this embodiment is provided in the middle of an ink path that starts from the main ink container 1 to return to the main ink container 1 via a diffusion valve 12 and a circulation pump 28. Incidentally, the viscometer 14 may be provided in the middle of the ink supply path that supplies the ink to the nozzle.
A sub-ink container 25 is filled with a replenishment ink 2b, and the replenishment ink 2b is connected to a replenishment valve 15, the supply valve 3, and the supply pump 4 by an ink replenishment pipe 16. Such a configuration forms an auxiliary ink supply unit. Incidentally, the auxiliary ink supply unit is not limited to the configuration described in this embodiment, and may have any configuration as long as the configuration enables the supply of an auxiliary ink to the main ink container 1. For example, an ink cartridge may be provided in an upper portion of the main ink container, and the auxiliary ink may be supplied from the ink cartridge. When the liquid level detected by a level gauge not illustrated which detects the ink level in the main ink container 1 is lower than a predetermined liquid level, the replenishment ink 2b is supplied to the main ink container 1. In addition, when the ink viscosity (detection value of the viscometer 14) is out of the range of ink viscosity required to perform normal printing, the replenishment ink 2b is supplied to the main ink container 1. This control will be described later.
An intensifying liquid container 17 is filled with an intensifying liquid 18. A solvent is used as the intensifying liquid. The intensifying liquid container 17, an intensifying liquid pump 19, an intensifying valve 20, and the main ink container 1 are connected to each by an intensifying liquid replenishment pipe 21 to communicate with each other. Accordingly, a solvent replenishment unit is formed to be able to supply the intensifying liquid (solvent) 18 to the main ink container 1. Incidentally, the solvent replenishment unit is not limited to the configuration described in this embodiment, and may have any configuration as long as the configuration enables the supply of the solvent to the main ink container. In addition, the main ink container 1 is connected to a discharge pipe 22. When the ink viscosity detected by the viscometer 14 is different from a value determined in advance (set), the intensifying liquid 18 is supplied to the main ink container 1 to regulate (control) the viscosity. Incidentally, this control is executed by the control unit to be described later. The supply of the intensifying liquid is performed by a path in which the intensifying liquid container 17, the intensifying liquid pump 19, the intensifying valve 20, and the main ink container 1 are connected to each other by the intensifying liquid replenishment pipe 21.
(Description of Heating Device)
Next, a specific configuration of the heating device 8 in this embodiment will be described with reference to
In
(Description of Control Unit)
Next, a configuration of the control unit which controls the entirety of the device will be described with reference to
The heating device control circuit 46 controls the ink temperature of the ink, which flows into the heating device 8, based on an instruction (command) of the MPU 40. The ink viscosity control circuit 48 performs control such that the solvent (intensifying liquid) and the replenishment ink are supplied to the main ink container 1 based on the detection value of the viscometer 14 to adjust the ink viscosity at a predetermined value or in a predetermined range. Each of the components is connected to the MPU 40 by a bus, and is controlled according to an instruction of the MPU 31. Incidentally, since the other components in
(Description of Ink Viscosity Control Operation)
Next, an ink viscosity control operation in one embodiment of the present invention will be described with reference to
In
Then, pressure pulsation is applied to the ink inside the nozzle 9 by a nozzle drive voltage (excitation voltage), and the ejected ink is atomized by the surface tension of the ink. The state of the ink particles (particle size or speed of the ink particles) is greatly affected by the ink viscosity in addition to the drive voltage and the surface tension of the ink, and affects printing characters.
Next, in
Subsequently, in step S03, it is determined whether or not the ink temperature inside the nozzle 9 is a temperature close to the maximum value of a temperature range corresponding to the range of ink viscosity in which normal printing can be executed. In this embodiment, a value slightly smaller than the maximum value of the amount of use of the ink (hereinafter, referred to as a maximum proximity value) is selected as a set value. In this example, the temperature set value will be described as 45° C. Incidentally, temperature control can be performed as long as a set temperature when the heating device 8 performs heating is in the temperature range (in a usable temperature range) corresponding to the ink viscosity at which normal printing can be executed. However, when the set temperature is set too low, the range of temperature control becomes narrow, which is not preferable. When the set temperature is set between the median value and the maximum value of the range, the range in which temperature control is executed can be expanded, and the amount of use of the solvent can be reduced, which is preferable. When the ink temperature inside the nozzle 9 estimated based on the measurement (estimated from the relationship of
In step S04, heating control is executed such that the ink temperature reaches the set temperature. Namely, the heating device control circuit 46 performs control to heat the PTC heater 33 of the heating device 8 such that the temperature of the ink ejected from the nozzle 9 reaches 45° C. Specifically, control is performed as shown in
However, when ambient temperature is 45° C. or higher which is the set value, the ink viscosity cannot be controlled to be further lowered by temperature control. This embodiment is configured such that even in such a case, the ink viscosity can be controlled to be in the range of ink viscosity which enables normal printing. For this reason, steps S05 to S07 are executed. The ink viscosity can be controlled to be in the range, which enables normal printing, by steps S05 to S07.
Namely, even when the ink temperature exceeds 45° C. in step S04, the process proceeds to step S05, and the control of the ink viscosity is executed. First, in step S05, the ink viscosity is detected by the viscometer 14. As a result of the detection, when the ink viscosity is determined to be a viscosity out of the range in which normal printing is performed, the process proceeds to step S07.
In step S07, control is performed such that the intensifying liquid (solvent) in the intensifying liquid container 17 or the replenishment ink in the sub-ink container 25 is supplied to the main ink container 1 to adjust the ink viscosity at the predetermined value or in the predetermined range (range of ink viscosity in which normal printing can be executed). When the ink viscosity is higher than the predetermined value or a normal range, basically, the solvent is supplied. Then, when the ink viscosity is lower than the normal range, control is performed to supply the replenishment ink to adjust the ink viscosity of the ink 2a in the main ink container 1. This control can be performed without problem as long as the ink viscosity is in the range of ink viscosity in which normal printing can be executed, but in this embodiment, the control is performed until the ink viscosity reaches the median value of the range.
Namely, when the detection value of the viscometer 14 is lower than a viscosity value which is the median value of the normal printing range of the relationship between ambient temperature and ink viscosity as shown in
In step S08, characters are printed after such a process is performed. Namely, printing is performed in such a manner that the ink of which the ink viscosity is regulated is supplied to the nozzle 9, and the ink particles charged by the charging electrode 23 are deflected by the deflection electrode 24 to land on a printing object. In addition, non-charged ink particles among the ejected ink particles travel straight and are captured by the gutter 11 to return to the main ink container 1 via the recovery pump 29. This control is executed by the control unit illustrated in
Next, in step S09, it is determined whether or not the scheduled printing is completed and stopped. If the scheduled printing work is not completed (when printing is desired to be continued), the process proceeds to step S02. When the scheduled printing work is completed, the operation is stopped.
(Regarding Reason for Setting Set Temperature High)
Here, in the above embodiment, the reason for setting the set value of temperature control high will be described in more detail.
On the other hand, when the set temperature is set to a high set value so as to be in a range from the median value to the median value of a usage temperature range (in the above-described embodiment, 45° C. is selected as the set value as shown in
As described above, in the first embodiment of the present invention described above, since control is performed in which the priority is given to ink temperature control by heating performed by the heating device, and the control of supplying the solvent and the replenishment ink to the main ink container is also used, the amount of use of the solvent can be reduced and normal printing can be performed. Namely, since ink viscosity control by temperature control is performed, the dependence of the ink viscosity control on the solvent can be reduced, and the ink temperature can be instantly raised to regulate the ink viscosity to an optimum level. Further, when the ink viscosity detected by the viscometer is out of the range of ink viscosity which enables normal printing, control is performed to supply the solvent and the replenishment ink to the main ink container according to the situation, so that normal printing can be always stably executed.
Incidentally, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical concept of the present invention.
Next, a second embodiment of the present invention will be described. In the second embodiment, the state of ink particles (particle size or speed of ink particles) ejected at the nozzle 9 is regulated to coincide with an ideal state, which is assumed in advance, by the control of the heating device 9. The entire configuration of an inkjet recording device in the second embodiment is the configuration of
First, before an operation of the second embodiment is described, the configuration of the nozzle 9 and the control of optimizing the state of ink particles ejected from the nozzle will be described with reference to
In light of such a situation, in the second embodiment of the present invention, in taking advantage of the fact that the state of ink particles ejected from the nozzle 9 varies depending on ink viscosity and the ink viscosity can change depending on ink temperature, the excitation voltage is set to a constant voltage determined by the type of an ink to be used, and the ink temperature is regulated by the heating device to regulate the ink viscosity during operation to an optimum level to optimize the state of the ink particles.
Next, a control operation in the second embodiment of the present invention will be described in detail with reference to
In
In step S01, the ink is supplied to the nozzle 9, and ink particles are ejected from the nozzle. The operation of step S01 is the same operations as step S01 of
In step S11, it is determined whether or not the ink has a high viscosity specification, based on a determination criterion determined in advance as to whether or not the ink viscosity is a high viscosity. Regarding the determination criterion, a reference viscosity is determined which is a determination criterion, and when the viscosity is the reference viscosity or higher, the viscosity is determined to be a high viscosity. As a result of the determination, when the ink is determined to have a high viscosity specification (the case of YES in step S11), the process proceeds to step S12. In the determination, when the ink is determined not to have a high viscosity specification (the case of NO in step S11), the process proceeds to step S13. Here, the reason for distinguishing between a high viscosity ink and a non-high viscosity ink is that in the case of a high-viscosity ink, in order to reduce the use of the solvent as much as possible, the control of setting temperature in the vicinity of the maximum usage temperature of the ink is performed. In the case of a relatively low viscosity, in order to relax the limitation, the excitation curve of the ink is used which is obtained in advance and represents a relationship between temperature and excitation voltage.
In step S12, the excitation voltage is set such that an excitation voltage at temperature in the vicinity of the maximum usage temperature of the ink (45° C.) is applied to the nozzle. Namely, the excitation voltage at which the ink particles are in an appropriate state in the vicinity of the maximum value (45° C. in this example) of the usage temperature of the ink having a high viscosity specification is set to be supplied to the piezoelectric element 50 of the nozzle 9. After this process, the process proceeds to step S02.
In step S13, the excitation curve (relationship between temperature and excitation voltage) of the ink used which is obtained in advance is selected, and the process proceeds to step S14. In step S14, the ink temperature inside the heating device is measured. In step S15, the measured ink temperature is used to set the excitation voltage such that an excitation voltage corresponding to the measured temperature of the ink used is applied to the nozzle. Namely, the excitation voltage at which the ink particles of the ink used are in an appropriate state is set to be supplied to the piezoelectric element 50 of the nozzle 9. After this process, the process proceeds to step S16.
Since the operation processes of steps S02 to S09 have been described in
In step S16, similar to step S05, the ink viscosity is measured. In step S17, similar to step S06, it is determined whether or not the ink is in the viscosity range which enables printing, and when the ink viscosity is not in the range which enables printing (case of NO), the process proceeds to step S18, and the control of regulating the ink viscosity is executed.
When the ink viscosity is in the range which enables printing in step S17 (case of YES), the process proceeds to step S19, and printing is executed. Then, when predetermined printing work is completed (case of YES in step S20), the operation of the device ends.
According to the second embodiment, the same effects as in the first embodiment can be obtained, and ink heating control can be performed by the heating device to control the state of the ink particles at the nozzle to an optimum state for printing. Accordingly, even when the excitation voltage is not regulated, ink particles with which optimum printing can be performed can be ejected from the nozzle 9.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-012986 | Jan 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/003046 | 1/28/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/158759 | 8/6/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20040070651 | Usui et al. | Apr 2004 | A1 |
| 20170274667 | Pagnon et al. | Sep 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 333 325 | Sep 1989 | EP |
| 2 695 654 | Feb 2014 | EP |
| 58-016851 | Jan 1983 | JP |
| 2002-59563 | Feb 2002 | JP |
| 2004-66499 | Mar 2004 | JP |
| 2008-137198 | Jun 2008 | JP |
| 2009-179023 | Aug 2009 | JP |
| 2015-85513 | May 2015 | JP |
| Entry |
|---|
| International Search Report of PCT/JP2020/003046 dated Apr. 14, 2020. |
| Extended European Search Report received in corresponding European Application No. 20748716.6 dated Sep. 26, 2022. |
| Number | Date | Country | |
|---|---|---|---|
| 20220072847 A1 | Mar 2022 | US |
