JP2020023126A - Ink jet recording device and control method of ink jet recording device - Google Patents

Abstract

To provide an ink jet recording device capable of performing back pressure control of an ink tank suppressing lowering of a degree of deaeration of ink.SOLUTION: An ink jet recording device includes: an ink deaerator which degasifies ink; a head section for injecting ink; an ink tank which is provided on a downstream side of the ink deaerator, stores supplied ink, and becomes B≤0.5A when ink amount within a specified range is A cmand contact area between ink and the atmosphere in the ink amount A is B cm; an ink tank heating section for heating ink within the ink tank; and a back pressure adjustment section which adjusts back pressure of ink within the ink tank.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an inkjet recording device and a control method of the inkjet recording device.

  In the inkjet recording apparatus, when bubbles are present in the ink when the ink is ejected from the head section, an ejection failure or the like occurs. For this reason, an ink jet recording apparatus has been proposed in which ink is degassed by an ink degassing device before the ink is sent to a head unit (for example, see Patent Document 1). Further, in order to suppress the contact between the ink and the atmosphere in the ink tank, an ink supply device of an ink jet recording apparatus in which a lid is provided on an ink liquid surface has been proposed (for example, see Patent Document 2).

JP 2017-24217 A JP-A-08-216422

  In the ink jet recording apparatus, it is necessary to apply a negative pressure to the head to control meniscus in the head. For this reason, in the ink jet recording apparatus, it is required not only to degas the ink but also to control the back pressure in the head by bringing the ink into contact with the atmosphere in the vicinity of the head. In the ink tank that performs such back pressure control, the ink comes into contact with the atmosphere, so that the degree of deaeration of the ink in the ink tank decreases.

  In order to solve the above-described problems, the present invention provides an inkjet recording apparatus capable of controlling the back pressure of an ink tank while suppressing a decrease in the degree of degassing of ink, and a method of controlling the inkjet recording apparatus.

An ink jet recording apparatus according to the present invention includes an ink degassing device for degassing ink, a head unit for ejecting the ink, and a specified range that accommodates ink that is provided and supplied downstream of the ink degassing device. When the ink amount in the ink tank is Acm ³ , and the contact area between the ink and the atmosphere at the ink amount A is Bcm ² , an ink tank satisfying B ≦ 0.5 A, and an ink tank for heating the ink in the ink tank A heating unit; and a back pressure adjusting unit for adjusting a back pressure of the ink in the ink tank.

Also, the control method of the ink jet recording apparatus of the present invention includes an ink degassing device for degassing the ink, a head unit for ejecting the ink, and an ink that is provided downstream of the ink degassing device and contains the ink. A tank, an ink tank heating unit for heating the ink in the ink tank, and a back pressure adjusting unit for adjusting the back pressure of the ink in the ink tank; Is Acm ³ , and when the contact area between the ink and the atmosphere in the ink amount A is Bcm ² , the ink amount in the ink tank is controlled so that B ≦ 0.5A.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording device which can control the back pressure of the ink tank which suppressed the fall of the deaeration of ink, and the control method of an inkjet recording device can be provided.

FIG. 2 is a diagram illustrating a schematic configuration of an inkjet recording apparatus. It is a bottom view of the nozzle surface of a head part. FIG. 3 is a block diagram of an ink supply system for supplying ink from an ink storage unit to a head unit in the inkjet recording apparatus. FIG. 3 is a diagram illustrating a configuration of an ink tank and its periphery. FIG. 2 is a block diagram illustrating a functional configuration of the inkjet recording apparatus. FIG. 3 is a diagram illustrating a configuration of an ink tank and its periphery. FIG. 7 is a top view of the ink tank shown in FIG. 6. 6 is a graph showing the measurement results of the degree of deaeration of the ink in Example 1. 9 is a table showing conditions of an ink volume A (cm ³ ) and a contact area B (cm ² ) between the ink and the atmosphere in Example 2. 9 is a table showing the measurement results of the ink deaeration degree in Example 2. 9 is a graph showing the measurement results of the degree of deaeration of the ink in Example 2. 11 is a graph showing the measurement results of the ink deaeration degree in Example 3. 14 is a graph showing a measurement result of an ink deaeration degree in Example 4.

Hereinafter, examples of embodiments for carrying out the present invention will be described, but the present invention is not limited to the following examples.
The description will be made in the following order.
1. Embodiment of an inkjet recording apparatus (first embodiment)
2. Embodiment of an inkjet recording apparatus (second embodiment)

<1. Embodiment of inkjet recording apparatus>
Hereinafter, a first embodiment of the inkjet recording apparatus of the present invention will be described.
FIG. 1 shows a schematic configuration of an ink jet recording apparatus.

[Configuration of inkjet recording apparatus]
The inkjet recording apparatus 100 shown in FIG. 1 has a line head, and discharges a plurality of colors, here, four colors of ink at appropriate timing while moving a recording medium with respect to the line head, thereby forming a color image. This is a one-pass type recording apparatus to be formed.

  The ink jet recording apparatus 100 includes a medium supply unit 10, an image forming main unit 20, a medium discharge unit 30, an ink storage unit 50, and a control unit 40 (see FIG. 5). In the inkjet recording apparatus 100, the recording medium P stored in the medium supply unit 10 is conveyed to the image forming main unit 20 under the control of the control unit 40, and is discharged to the medium discharge unit 30 after an image is formed. You.

(Medium supply unit)
The medium supply unit 10 sends the recording medium P stored therein to the image forming main unit 20 one by one. As the recording medium P, in addition to printing paper, various types of cells, such as cells, films, and cloths, which can be curvedly supported on the outer peripheral surface of the image forming drum 22 are used.

  The medium supply unit 10 includes a supply tray 11 that stores the recording medium P, and a feeder board 12 that conveys the recording medium P from the supply tray 11 to the image forming main unit 20. Further, the medium supply unit 10 includes a supply unit (not shown) that transfers the uppermost recording medium P placed on the supply tray 11 onto the belt 123.

The supply tray 11 is a plate-shaped member on which one or a plurality of recording media P can be placed. The supply tray 11 is provided to move up and down according to the amount of the recording medium P placed on the supply tray 11.
The feeder board 12 includes a roller 121 and a roller 122 provided inside, and a ring-shaped belt 123 suspended by the rollers 121 and 122. By driving the rollers 121 and 122, the feeder board 12 conveys the recording medium P transferred from the supply unit onto the belt 123 along the belt 123.

(Image forming body)
The image forming main unit 20 includes a delivery unit 21, an image forming drum 22, a head unit 23, an irradiation unit 24, and a delivery unit 25.

  The transfer unit 21 transfers the recording medium P transferred from the medium supply unit 10 to the image forming drum 22. The transfer unit 21 has a swing arm 211 and a transfer drum 212. The swing arm 211 carries one end of the recording medium P conveyed from the feeder board 12. Then, the transfer drum 212 transfers the recording medium P carried on the swing arm 211 to the image forming drum 22.

  The image forming drum 22 has a cylindrical outer shape, carries the recording medium P on the outer peripheral surface of the cylindrical portion, and conveys the recording medium P in accordance with a rotation operation about the central axis of the cylinder. A drum heater 221 for heating the outer peripheral surface and the recording medium P is provided near the outer peripheral surface of the image forming drum 22. The drum heater 221 is, for example, in a rotation direction of the image forming drum 22, between a position at which the transfer unit 21 transfers the recording medium P to the image forming drum 22 and a position at which the head unit 23 records the image on the recording medium P. Provided. The heating operation time and intensity of the drum heater 221 are controlled based on the measured temperature of the outer peripheral surface of the image forming drum 22 by a temperature measuring unit (not shown) or the like so that the temperature of the recording medium P to be carried becomes an appropriate temperature. Thereby, the curing speed of the recording medium P when the ink lands on the recording medium P is appropriately maintained, and a high-quality image is stably formed. As the drum heater 221, for example, an infrared heater or a heating wire that generates heat when energized is used. The drum heater 221 may be provided inside the image forming drum 22 and heat the outer peripheral surface by heat conduction.

  The head section 23 has a plurality of nozzle openings provided on a surface (nozzle surface) of the recording medium P facing the recording target surface. The head unit 23 ejects ink droplets from the nozzle openings at appropriate timing to the recording surface of the recording medium P that moves in accordance with the rotation of the image forming drum 22, and discharges the ink droplets onto the recording target surface of the recording medium P An image is formed by landing.

  FIG. 2 is a bottom view of the nozzle surface of the head unit 23. The head section 23 shows an example in which eight inkjet heads 230 are arranged in a staggered pattern. The ink jet heads 230 are arranged so as to overlap in the width direction perpendicular to the transport direction of the recording medium P. Accordingly, by moving the recording medium P in the transport direction while the head unit 23 is fixed, an image can be recorded in a one-pass system in which an image is recorded in the entire area of the recording medium P in the width direction.

  The inkjet recording apparatus 100 shown in FIG. 1 includes a plurality of head units 23 at predetermined intervals in the transport direction of the recording medium P. FIG. 1 shows an example in which four head units 23 are provided according to the four color inks. The four head units 23 output, for example, Y (yellow), M (magenta), C (cyan), and K (black) inks, respectively. As these inks, for example, various known inks that change from a gel state to a sol state when heated from normal temperature and are cured by irradiating ultraviolet rays are used. Further, the ink supplied to the image forming main unit 20 is maintained at an appropriate temperature by a heating unit (not shown).

  The irradiating section 24 irradiates an energy ray having a predetermined wavelength, for example, an ultraviolet ray in a near ultraviolet region (wavelength is about 400 nm), and cures the ink discharged from the head section 23 and landed on the recording medium P. The formed image is fixed. The irradiation unit 24 includes, for example, a light emitting diode (LED) that emits ultraviolet light, a mercury lamp, or the like as an irradiation source. The irradiation unit 24 is applied with a voltage by driving the irradiation driving unit 74 (see FIG. 5), and irradiates the ink on the recording medium P with ultraviolet rays. The irradiation unit 24 is provided at a position downstream of the head unit 23 in the rotation direction of the image forming drum 22 and at a position upstream of the upstream side where the recording medium P is delivered to the delivery unit 25. Further, in the irradiation unit 24, a light shielding plate 241 is provided at a position covering the irradiation source and the set range of the ultraviolet light in order to reduce the amount of ultraviolet light leaking out of the set range in which the recording medium P is irradiated with the ultraviolet light. I have.

  The configuration of the irradiation source that emits ultraviolet light in the irradiation unit 24 is not particularly limited. When the ink has a property of being cured by receiving energy rays other than ultraviolet rays, a well-known irradiation source that emits energy rays of a wavelength that cures the ink is provided instead of the above-described configuration that emits ultraviolet rays.

  The delivery unit 25 conveys the recording medium P after the landed ink is cured and the image formation is completed to the medium discharge unit 30. The delivery unit 25 includes a cylindrical delivery roller 251, a plurality (for example, two) of rollers 252 and 253, and a ring-shaped belt 254 carried by the rollers 252 and 253. The transfer roller 251 receives the recording medium P from the image forming drum 22 and guides the recording medium P onto the belt 254. The delivery unit 25 moves and conveys the recording medium P transferred from the transfer roller 251 onto the belt 254 along with the belt 254 circulating with the rotation of the rollers 252 and 253, and sends out the recording medium P to the medium discharge unit 30. .

  The medium discharge unit 30 stores the recording medium P sent from the image forming main unit 20 by the delivery unit 25 until the recording medium P is taken out by the user. The medium discharge unit 30 has a plate-shaped discharge tray 31 on which the recording medium P after image formation is placed.

  The control unit 40 (see FIG. 5) controls the operations of the medium supply unit 10, the image forming main unit 20, the ink storage unit 50, and the medium discharge unit 30. An image is formed on the recording medium P according to the setting related to the formation.

  The ink storage unit 50 stores ink of each color used for recording an image, and supplies the ink to the head unit 23 (the inkjet head 230) of the image forming main unit 20. Although each configuration of the ink storage unit 50 is not particularly limited, for example, the configuration is arranged in a dedicated rack or the like, and is connected to the image forming main unit 20 via a tube such as a tube.

[Ink supply system of inkjet recording apparatus]
In the ink jet recording apparatus 100, ink is supplied from the ink storage unit 50 to the head unit 23 via an ink flow path. FIG. 3 is a block diagram of an ink supply system for supplying ink from the ink storage unit 50 to the head unit 23 in the inkjet recording apparatus 100.

  As shown in FIG. 3, the ink supply system of the inkjet recording apparatus 100 includes an ink storage unit 50, an ink deaerator 29, an ink tank 26, and a head unit 23. Further, in the ink jet recording apparatus 100, a plurality of head units 23 are provided for each of the plurality of ink types described above, and each of the head units 23 is provided with an ink corresponding to each ink type via an independent ink supply system. The ink is supplied from the storage unit 50.

  Further, the ink jet recording apparatus 100 includes a first ink supply section 51 including a pump or the like for supplying ink from the ink storage section 50 to the ink deaeration apparatus 29, and ink from the ink deaeration apparatus 29 to the ink tank 26. And a second ink supply unit 52 composed of a pump or the like for sending the liquid. In the inkjet recording apparatus 100, a gas flow path for adjusting the pressure of ink or air (air) in the ink flow path is provided. The ink flow path and the gas flow path form a first ink supply unit 51 and a second ink supply unit 52 for supplying ink to the head unit 23.

The ink tank 26 is a tank having a smaller capacity than the ink storage unit 50, and is configured by a closed container that appropriately stores the ink stored in the ink storage unit 50.
An ink deaerator 29 is provided between the ink reservoir 50 and the ink tank 26, and the ink deaerator 29 removes bubbles and dissolved gas from the ink sent from the ink reservoir 50 to the ink tank 26. Perform deaeration. The ink deaerator 29 has, for example, a large number of hollow fiber membranes, and contacts the ink with the outer surface of the hollow fiber membrane while evacuating the inside of the hollow fiber membrane by a vacuum pump, thereby removing air in the ink. Aspirate inside the hollow fiber membrane.

  The ink jet recording apparatus 100 includes a back pressure adjusting unit 27 connected to the ink tank 26, and the back pressure in the ink tank 26 is controlled by the back pressure adjusting unit 27. The back pressure adjusting unit 27 includes a back pressure valve (not shown) connected to the ink tank 26 via a gas flow path, an air tank, a back pressure pump connected to the air tank, and the like. The back pressure adjusting unit 27 opens the back pressure valve, for example, so that the ink tank 26 and the air tank communicate with each other through a gas flow path. Then, the pressure (air pressure) in the ink tank 26 is adjusted by driving the back pressure pump to reduce the pressure (air pressure) in the air tank (negative pressure).

  Further, the inkjet recording apparatus 100 includes a deaerator heating unit 53, an ink tank heating unit 54, and a head heating unit 55, and the ink deaerator 29, the ink tank 26, and the head unit 23 deaerate, respectively. The heating is performed by the device heating unit 53, the ink tank heating unit 54, and the head heating unit 55, and the temperature is controlled to be a predetermined temperature.

[Structure of ink tank]
FIG. 4 shows the configuration of the ink tank 26 and its surroundings. The ink sent from the ink deaerator 29 via the second ink supply unit 52 is stored in the ink tank 26. The ink stored in the ink tank 26 is maintained at a predetermined temperature by the ink tank heating unit 54. The ink stored in the ink tank 26 is transported to the head unit 23 and is discharged from the head unit 23 according to a print job.

  A liquid level sensor 56 is provided on an upper surface (an interface between ink and air) of the ink contained in the ink tank 26 as an ink amount detecting unit for detecting the amount of ink in the ink tank 26. . As the liquid level sensor 56, a known sensor can be used. For example, a configuration in which a level switch for detecting the presence or absence of ink is disposed at a position where the ink has an upper limit value and a lower limit value in the ink tank 26, or a liquid for measuring the amount of ink in the ink tank 26 as a continuous value The structure which arranges a surface meter may be sufficient. These liquid level sensors 56 include a float sensor that detects the liquid level based on the position of the float, an ultrasonic sensor that measures the reflection of ultrasonic waves on the liquid level, and a liquid level sensor based on the dielectric constant difference between gas and liquid. And a pressure sensor for detecting the weight and pressure of the liquid at the lower part of the tank.

  A back pressure adjusting unit 27 is connected to the ink tank 26 via a gas flow passage in a cavity above the stored ink. In the ink tank 26, the pressure in the cavity above the ink is controlled by the operation of the back pressure adjusting unit 27. Thereby, back pressure control in the head section 23 can be performed. For example, on the nozzle surface of the head unit 23, a pressure difference is generated between the ink pressure in a normal state (that is, a state in which the pressure for ejecting ink is not applied) and the atmospheric pressure, so that the ink from the nozzle becomes unnecessary. Leakage can be suppressed. In addition, the back pressure in the head unit 23 can be adjusted so that the ink is appropriately ejected in accordance with the pressure pattern applied when the ink is ejected.

When the ink amount (volume) within the specified range held in the ink tank 26 is Acm ³ and the contact area between the ink and the atmosphere at the ink amount A is Bcm ² , B ≦ 0.5A is satisfied. It is formed to satisfy. When the ink jet recording apparatus is driven, the ink is sent from the ink tank 26 to the head unit 23, and the ink is sent from the ink storage unit 50 to the ink tank 26. Is stored in the ink tank 26 in the range from the lower limit to the lower limit. Therefore, the ink amount (volume) Acm ³ within the specified range in the ink tank 26 can be an ink amount between the upper limit and the lower limit of the ink tank 26.

  In the ink tank 26 provided on the downstream side of the ink deaerator 29, the degree of deaeration of the ink decreases due to the contact between the ink and the atmosphere. In particular, when the ink jet recording apparatus 100 has a configuration such as the ink tank heating unit 54 that promotes the convection of the ink in the ink tank 26, the atmosphere is easily dissolved in the ink, and the degree of deaeration of the ink is reduced. Easy to fall. In order to suppress a decrease in the degree of deaeration of the ink in the ink tank 26, the ink must not be brought into contact with the atmosphere in the ink tank 26, or the contact area between the ink and the atmosphere must be reduced. Is preferred.

  On the other hand, in the ink jet recording apparatus 100, it is necessary to connect the back pressure adjusting unit 27 to the cavity above the ink tank 26 and adjust the pressure in the cavity to perform meniscus control of the ink in the head unit 23. . That is, in order to control the back pressure in the ink tank 26, it is necessary to bring the ink into contact with the atmosphere in the ink tank 26. For this reason, in the ink jet recording apparatus 100, it is necessary to control the decrease in the degree of deaeration and to control the back pressure by limiting the contact area between the ink and the atmosphere in the ink tank 26 and bringing the ink into contact with the atmosphere.

[Functional configuration of inkjet recording apparatus]
FIG. 5 is a block diagram illustrating a functional configuration of the inkjet recording apparatus 100 according to the present embodiment. In the following description, the configurations and reference numerals shown in FIGS. 1 to 4 will be used together with the configuration and reference numerals shown in FIG. 5 as necessary.

  As described above, the inkjet recording apparatus 100 includes the first ink supply unit 51, the second ink supply unit 52, the ink deaerator 29, the back pressure adjustment unit 27, the liquid level sensor 56, The heating unit 53 includes a heating unit 53, an ink tank heating unit 54, and a head heating unit 55. Further, the inkjet recording apparatus 100 includes a control unit 40, a transport driving unit 71, a head driving unit 731, an irradiation driving unit 74, a communication unit 61, an operation display unit 62, and a bus 69. The bus 69 is a path for electrically connecting the components and exchanging signals.

The control unit 40 controls the overall operation of the inkjet recording apparatus 100. The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a memory 44.
The CPU 41 performs various arithmetic processes according to a program read from the ROM 43, and performs operations such as transport of a recording medium, opening and closing operations of each valve, operations of sending ink by each pump, and operations of ejecting ink in the inkjet recording apparatus 100. Perform control. Further, the CPU 41 performs various processes related to image recording based on image data, status signals of each unit, clock signals, and the like according to the program read from the ROM 43. The RAM 42 provides a working memory space to the CPU 41 and stores temporary data. The ROM 43 stores a control program, initial setting data, and the like. The ROM 43 includes a non-volatile memory that can be overwritten and updated, and can store setting data that is set and maintained as needed. The memory 44 is an image memory for temporarily storing image data to be recorded.

  The transport drive unit 71 generates a drive signal for rotating each of the rollers for driving the rotation motor of the image forming drum 22 and the feeder board 12 and the delivery unit 25 in appropriate directions and speeds. Then, the transport driving unit 71 outputs a driving signal corresponding to the rotation direction and the rotation speed of each of these motors based on the control signal from the control unit 40.

  The first ink supply unit 51 and the second ink supply unit 52 are provided on the basis of a control signal from the control unit 40, based on a control signal from the control unit 40, with a pump disposed in an ink conveyance path between the ink storage unit 50 and the ink tank 26. , The ink is sent from the ink storage unit 50 to the ink tank 26 via the ink deaerator 29. When the ink is sent from the ink storage unit 50 to the ink tank 26, the ink passes through the ink deaerator 29 so that the ink is degassed before the ink reaches the ink tank 26. For this reason, the degassed ink is stored in the ink tank 26.

  The head driving unit 731 generates and outputs a driving voltage signal for causing the pressure chamber (piezoelectric element) to perform a deforming operation (perform a driving operation) in order to appropriately eject ink from each nozzle of the inkjet head 230. . The head driving unit 731 selects a pre-stored voltage waveform pattern to generate a power-amplified driving voltage signal based on a control signal from the control unit 40, and responds to image data input from the memory 44. Whether to output a drive voltage signal to each piezoelectric element is switched.

  The ink tank heating unit 54 maintains the ink in the ink tank 26 in a sol state by heating and maintaining the ink in the ink tank 26 at an appropriate temperature. Further, the head heating unit 55 maintains the ink viscosity at the time of ejection in an appropriate state by heating and maintaining the ink at an appropriate temperature in the head unit 23 of the image forming main body unit 20 or the like. The deaerator heating unit 53 maintains the ink at an appropriate temperature in the ink deaerator 29 by heating the ink to an appropriate temperature and maintaining the viscosity, temperature, saturated dissolved oxygen concentration, and the like of the ink at the time of deaeration. . The temperature of the ink in the ink deaerator 29, the head unit 23, and the ink tank 26 is measured by a temperature measurement unit or the like arranged in each component and output to the control unit 40. The control unit 40 controls the operation states of the ink tank heating unit 54, the head heating unit 55, and the deaerator heating unit 53, and the temperature of the ink in the ink deaerator 29, the head unit 23, and the ink tank 26 is reduced. Adjusted.

The liquid level sensor 56 detects the amount of ink in the ink tank 26 and outputs a detection signal to the control unit 40. The liquid level sensor 56 detects the amount of ink in the ink tank 26 by, for example, measuring the height of the liquid level of the ink in the ink tank 26. In accordance with the amount of ink in the ink tank 26 detected by the liquid level sensor 56, ink is supplied from the ink storage unit 50 to the ink tank 26, and an appropriate amount of ink is maintained in the ink tank 26. Accordingly, when the ink amount (volume) within the specified range of the ink tank 26 is Acm ³ , and the contact area between the ink and the atmosphere at the ink amount A is Bcm ² , the ink satisfies B ≦ 0.5A. An appropriate amount of ink is maintained in the tank 26.

Further, the liquid level sensor 56 outputs the measurement result of the ink amount in the ink tank 26 to the control unit 40. The control unit 40 acquires the amount of ink in the ink tank 26 based on the output from the liquid level sensor 56. The control unit 40 adjusts the amount of ink supplied from the ink storage unit 50 to the ink tank 26 based on the acquired amount of ink in the ink tank 26. Accordingly, when the ink amount (volume) within the specified range in the ink tank 26 is Acm ³ and the contact area between the ink and the atmosphere at the ink amount A is Bcm ² , B ≦ 0.5A is satisfied. Control for maintaining the amount of ink in the ink tank 26 can also be performed.

  In the back pressure adjuster 27, the opening and closing of the back pressure valve is controlled by a control signal from the controller 40. Further, the drive of the back pressure pump is controlled by a control signal of the control unit 40, and the pressure (air pressure) in the air tank is controlled to a predetermined pressure (negative pressure).

The irradiation drive unit 74 applies a predetermined voltage to the irradiation source of the irradiation unit 24 according to a control signal from the control unit 40 to cause a current to flow, and causes the irradiation source to emit an energy ray having a predetermined wavelength.
The communication unit 61 is a communication interface that controls a communication operation with an external device. The communication interface includes, for example, a plurality of interfaces that support various communication protocols, such as a LAN board and a LAN card. The communication unit 61 acquires image data to be recorded and setting data (job data) related to image recording from an external device under the control of the control unit 40, and transmits status information and the like to the external device.

  The operation display unit 62 displays the status of the inkjet recording apparatus 100 and an operation menu according to a control signal from the control unit 40, and receives an input operation from the outside such as a user and outputs it to the control unit 40. The operation display unit 62 includes, for example, a liquid crystal display unit in which a touch sensor as operation reception means is provided so as to overlap a display screen as display means. The control unit 40 displays on the liquid crystal display unit various menus and the like for receiving a status and a command from the touch sensor, and performs information on the content and position of the displayed menu and the user's touch operation detected by the touch sensor. A control operation for causing each unit of the inkjet recording apparatus 100 to perform a corresponding process is performed.

<2. Embodiment of inkjet recording apparatus (second embodiment)>
Next, a second embodiment of the ink jet recording apparatus will be described. Note that the same configuration as that of the above-described first embodiment can be applied to the ink jet recording apparatus of the second embodiment except for the configuration of the liquid level sensor disposed in the ink tank. For this reason, in the following description, the description overlapping with the above-described first embodiment will be omitted, and the configuration of the ink tank in which the liquid level sensor is disposed will be mainly described.

[Structure of ink tank]
FIG. 6 shows the configuration of the ink tank 26 and its surroundings of the ink jet recording apparatus according to the second embodiment. FIG. 7 is a top view of the ink tank 26 shown in FIG. Note that the same configuration as that of FIGS. 1 to 3 described above can be applied to the overall configuration of the inkjet recording apparatus and the ink supply system in the inkjet recording apparatus.

  In the ink jet recording apparatus having the configuration shown in FIG. 6, as in the ink jet recording apparatus according to the first embodiment, ink is sent from the ink storage unit 50 into the ink tank 26 via the ink deaerator 29. The ink stored in the ink tank 26 is maintained at a predetermined temperature by the ink tank heating unit 54. The ink contained in the ink tank 26 is sent to the head unit 23 and is discharged from the head unit 23 according to a print job.

  The ink tank 26 shown in FIGS. 6 and 7 includes an air shutoff unit for partially shutting off contact between the ink and the atmosphere. FIGS. 6 and 7 show an example in which a lid member 58 that covers the upper surface (the interface between ink and air) of the ink contained in the ink tank 26 is provided as an example of the air blocking unit. The lid member 58 preferably includes a float that floats on the upper surface of the ink by buoyancy. Note that the air blocking section is not limited to the lid member 58, and the configuration such as the shape and material is not limited as long as the contact between the ink 57 and the air in the ink tank 26 can be inhibited. Further, the configuration such as the shape and material of the lid member 58 can be appropriately selected according to the shape of the ink tank 26, the physical properties of the ink, and the like. The configuration of the float and the like is not limited as long as the float can float on the ink in the ink tank 26 and can prevent contact between the ink 57 and the atmosphere.

As shown in FIG. 7, in the portion of the ink tank 26 where the lid member 58 (float) floats, the contact between the ink 57 and the atmosphere is largely blocked by the lid member 58. For this reason, a portion where the ink 57 mainly contacts the atmosphere is limited to a portion where the upper surface of the ink 57 is exposed between the lid member 58 and the wall surface of the ink tank 26.
As described above, in the ink tank 26, the presence of the lid member 58 on the ink 57 prevents the lid member 58 from contacting the ink 57 and the atmosphere. The contact area is limited.

In the ink jet recording apparatus according to the second embodiment, the portion where the upper surface of the ink 57 is exposed can be limited by adjusting the size of the air blocking portion such as the lid member 58. For this reason, the size of the air blocking portion is adjusted, and the area B (cm ² ) of the contact surface between the ink 57 exposed from the air blocking portion and the atmosphere is limited, so that the ink is accommodated in the ink tank 26. The ink tank 26 satisfying B ≦ 0.5 A with respect to the volume A (cm ³ ) of the ink 57 can be easily realized irrespective of the shape and the volume.

  Further, in the ink jet recording apparatus according to the second embodiment, it is preferable that the lid member 58 constituting the air blocking unit is a part of the liquid level sensor 56. For example, it is preferable that the liquid level sensor 56 is a float sensor, and the float of the float sensor is the lid member 58. Since the lid member 58 constitutes the liquid level sensor 56, the contact between the ink 57 and the atmosphere can be limited by the liquid level sensor 56, so that an additional configuration in the ink tank 26 becomes unnecessary. The float sensor may be any type of sensor as long as it has a float that floats on the ink contained in the ink tank 26 by buoyancy.

  Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

[Example 1: Reduction of ink degassing degree due to contact area]
As described in each of the above embodiments, when ink is stored in the ink tank for a long time in contact with the atmosphere, the degree of deaeration of the ink decreases. This decrease in the degree of degassing of the ink is affected by the ratio between the volume A (cm ³ ) of the ink in the ink tank and the contact area B (cm ² ) between the ink and the atmosphere. Further, as the ink residence time in the ink tank increases, the degree of deaeration of the ink decreases. Therefore, an ink tank containing ink is prepared so that the ratio between the ink volume A (cm ³ ) and the contact area B (cm ² ) is different from each other, and the degree of deaeration of the ink in the ink tank decreases with time. Was measured.

The measurement of the degree of deaeration of the ink was performed under the following conditions.
Piezo head as a head portion 23, the pump and the first ink feeding portion 51 as a second ink feeding section 52, the ink capacity is 25000 cm ³ of ink reservoir 50, ink ink capacity of the deaeration apparatus 29 is 300 cm ^3, an ink tank 26, an ink jet recording apparatus 100 (see FIG. 3) having an ink capacity of 60 cm ³ was prepared. Further, a vacuum pump and a deaerator using a hollow fiber membrane were used as the ink deaerator, and the ink was deaerated by controlling the vacuum pump to about -98 kPa. A back pressure pump having a pressure sensor was used as the back pressure adjusting unit 27, and the back pressure in the ink tank was controlled at -2 kPa according to the pressure value of the pressure sensor. As the ink, a gel ink (a phase change ink that changes from a gel to a sol at a predetermined temperature) was used.

In the apparatus having the above configuration, the ratio of the contact area B (cm ² ) between the ink and the atmosphere in the ink amount A (cm ³ ) in the ink tank is B = 0.2 Acm ² , B = 0.3 Acm ² , B = The ink amount in the ink tank was adjusted so that 0.5 Acm ² , B = 0.7 Acm ² and B = 0.9 Acm ² .

Further, in the above-described ink jet recording apparatus, assuming a state where the power is continuously turned on for one week without consuming the ink, under the condition that the ink in the ink deaerator 29, the ink tank and the head unit is heated at 80 ° C. Hold for 7 days. Then, the degree of degassing of the ink in the ink tank was measured every day. Generally, if the degree of deaeration can be maintained at 80% or more, it is considered that there is no practical problem.
The degree of deaeration of the ink was calculated using the following equation.
Deaeration (%) = [1− (dissolved oxygen content in ink / saturated dissolved oxygen content at measurement temperature)] × 100

  The degree of degassing was measured by the dissolved oxygen concentration. The dissolved oxygen concentration can be measured by, for example, the Ostwald method (Experimental Chemistry Lecture 1, Basic Operation [I], p. 241, 1975, see Maruzen), a method of measuring by mass spectrometry, or a simple method such as galvanic cell type or polarographic type. It can be measured using an oximeter or a colorimetric analysis method. The dissolved oxygen concentration may be measured using a commercially available dissolved oxygen concentration meter (DO-30A type manufactured by Toa Denpa Kogyo KK).

FIG. 8 shows the measurement results of the ink deaeration degree.
As shown in FIG. 8, the degassing degree of the ink decreases with time under any conditions in which the ratio of the contact area B (cm ² ) between the ink and the atmosphere in the ink amount A (cm ³ ) is changed. Further, as the contact area between the ink and the atmosphere in the ink tank increases, the rate of decrease in the degree of deaeration in the ink increases.

Under the above-described conditions, by setting the contact area B (cm ² ) between the ink and the atmosphere to 0.5 Acm ² or less, the degree of deaeration of the ink after holding for 7 days is considered to be in a range where there is no practical problem. The above has been maintained. That is, by setting the ratio of the contact area B (cm ² ) between the ink and the atmosphere in the ink amount A (cm ³ ) in the ink tank to B ≦ 0.5 Acm ² , the degassing degree can be set to a practically acceptable range. Can be suppressed.

  By stopping the heating of the ink tank, the gel ink (phase change ink) is turned into a solid (gel) by suppressing the temperature of the ink and the convection is suppressed, so that the dissolution of the atmosphere is suppressed. Usually, when the ink jet recording apparatus is stopped, the heating of the ink tank is also stopped, so that the gel ink is solidified and the decrease in the degree of degassing is suppressed. For this reason, if the degree of deaeration of 80% or more can be maintained under the condition that the sol-state ink is convected for 7 days by heating as in the above measurement conditions, the deaeration in the ink tank is within the practical range. It is possible to sufficiently suppress the generation of bubbles in the head due to the decrease in the degree.

Accordingly, by providing an ink tank in which the contact area Bcm ² between the ink and the atmosphere satisfies B ≦ 0.5 A in the ink amount (volume) Acm ³ within the specified range of the ink tank, a reduction in the degassing degree of the ink is suppressed. Thus, an ink jet recording apparatus capable of controlling back pressure can be realized. Further, in the ink tank, by controlling the contact area Bcm ² between the ink and the atmosphere in the ink amount (volume) Acm ³ within the specified range to B, ≦ 0.5 A, it is possible to suppress the decrease in the degree of degassing of the ink. In addition, an ink jet recording apparatus capable of controlling the back pressure can be realized.

[Example 2: Reduction of ink degassing degree due to ink volume]
Then, under the condition that the ratio of the contact area B (cm ²⁾ in the ink volume A (cm ³⁾ is constant at B = 0.5A, the ink volume A (cm ³⁾ and the contact area B (cm ²⁾ and is Ink tanks containing ink were prepared so as to be different from each other, and how the degree of deaeration of the ink in the ink tank decreased with time was measured.

FIG. 9 shows conditions (conditions 1 to 4) of the ink volume A (cm ³ ) of the ink tank and the contact area B (cm ² ) between the ink and the atmosphere. Except for the ink volume A (cm ³ ) and the contact area B (cm ² ) between the ink and the atmosphere, the same apparatus and method as in the measurement of the degree of degassing in Example 1 described above were used.

FIG. 10 shows a table of the measurement results of the ink deaeration degree. FIG. 11 shows a graph.
As shown in FIGS. 10 and 11, the ink volume A at a ratio same conditions of the contact area B (cm ²⁾ of the ink and the atmosphere in (cm ^3), the ink volume A (cm ³⁾ and the contact area B (cm ² ), the degree of degassing similarly decreases.
Further, even if the ink volume A (cm ³ ) and the contact area B (cm ² ) change, the ratio of the contact area B (cm ² ) between the ink and the atmosphere in the ink volume A (cm ³ ) is B = 0. At 0.5 A, the degree of deaeration of the ink after holding at 80 ° C. for 7 days can be maintained at 80% or more.

From this result, the ink volume A (cm ³⁾ of and the ink tank, regardless of the contact area B (cm ²⁾ of the ink and the atmosphere, the contact area between the ink and the atmosphere in the ink volume A (cm ³⁾ B ( When the ratio of (cm ² ) is B ≦ 0.5A, the degree of deaeration after 7 days can be maintained at 80% or more. As described above, in the ink tank for bringing the ink into contact with the atmosphere for controlling the back pressure, the contact area B (cm ² ) between the ink and the atmosphere is set to 0.5 A or less with respect to the ink volume A (cm ³ ). As a result, a decrease in the degree of deaeration of the ink can be sufficiently suppressed to a practical range. As a result, it is possible to realize an ink jet recording apparatus capable of suppressing the decrease in the degree of deaeration of the ink and controlling the back pressure.

Example 3 Reduction of Deaeration of Ink by Deaeration Temperature
Next, under the condition that the temperature of the ink in the ink tank is different from the temperature of the ink degassing device arranged on the upstream side of the ink tank, the state of a decrease in the degree of deaeration of the ink in the ink tank with time is measured. did.

The ink amount A (cm ³ ) in the ink tank is 30 (cm ³ ), the contact area B (cm ² ) between the ink and the atmosphere is 15 (cm ² ), and the contact area B (cm ³ ) in the ink amount A (cm ³ ) ² ) An ink tank having a ratio of B = 0.5 Acm ² was prepared. Then, the ink jet recording apparatus was set such that the ink temperature in the ink deaerator was 80 ° C. or 95 ° C., and the ink temperature in the ink tank was 80 ° C.
Except for the above conditions, the same apparatus and method as in the measurement of the degree of deaeration in Example 1 were used.

FIG. 12 shows the measurement results of the ink deaeration degree.
As shown in FIG. 12, the condition under which the ink temperature in the ink deaerator is 95 ° C. (dashed line in FIG. 12) is lower than the condition under which the ink temperature in the ink deaerator is 80 ° C. (solid line in FIG. 12). However, the decrease in the degree of degassing with the lapse of time became gentle.
Since the dissolved oxygen amount of the ink tends to decrease as the ink temperature increases, the ink is more easily degassed by increasing the temperature of the ink deaerator. Therefore, increasing the degassing temperature of the ink reduces the amount of oxygen contained in the ink supplied to the ink tank. As described above, by reducing the amount of dissolved oxygen in the ink supplied to the ink tank in advance, the amount of dissolved oxygen in the ink can be reduced even after the ink is held in the ink tank for a certain period of time under the condition of contact with the atmosphere. .

  As described above, as the temperature of the liquid increases, the amount of saturated dissolved oxygen decreases, and therefore, by increasing the temperature in the deaerator, the amount of saturated dissolved oxygen in the ink decreases. At this time, the gas that has become supersaturated due to a decrease in the amount of saturated dissolved oxygen due to a rise in temperature becomes bubbles in the ink. Bubbles generated in the ink cause cavitation immediately when the ink is ejected from the head portion, which is a problem. In particular, in the ink chamber of the head unit including the piezo element, continuous pressurization and depressurization of the ink are repeated. At this time, if minute bubbles are present in the ink, the dissolved gas moves into the bubbles when the ink is depressurized, and the gas is redissolved from the bubbles into the ink when the ink is pressurized. When such pressurization and depressurization are repeated, the flow of the dissolved gas into the bubble is superior due to the surface area of the bubble, and the bubble grows. When the bubbles grow to a certain size, cavitation occurs in the head portion. The flow of the dissolved gas into the bubbles is proportional to the partial pressure of the dissolved gas in the ink (concentration of dissolved gas / concentration of saturated dissolved gas).

  As described above, from the viewpoint of the degree of deaeration, as the ink temperature decreases, the amount of saturated dissolved oxygen increases. (Temperature of the deaerator). Alternatively, in the ink deaerator, it is preferable to perform the deaeration of the ink at a temperature higher than the temperature in the ink flow path after the deaeration of the ink tank and the head. In addition, the control unit controls the ink deaeration temperature in the ink deaerator and the temperature of the ink flow path after deaeration of the ink tank and the head unit so that the ink temperature has the above relationship. Is also good.

[Example 4: Reduction in the degree of deaeration of the ink due to the temperature difference between the ink and the atmosphere]
Next, under a condition where the ink temperature in the ink tank and the atmospheric temperature are different, the state of a decrease in the degree of deaeration of the ink in the ink tank over time was measured. The air temperature was changed to 40 ° C., 50 ° C., 60 ° C., and 70 ° C. with the ink temperature in the ink tank set at 80 ° C. or 90 ° C. Thereby, the temperature difference between the ink and the atmosphere in the ink tank was set at 20 ° C., 30 ° C., or 40 ° C., and the degree of deaeration of the ink was measured.
Except for the above conditions, the same apparatus and method as in the measurement of the degree of deaeration in Example 1 were used.

FIG. 13 shows the measurement results of the ink deaeration degree.
As shown in FIG. 13, regardless of whether the ink temperature is 80.degree. C. or 90.degree. On the other hand, even when the ink temperature is 80 ° C. or 90 ° C., the condition where the temperature difference between the ink and the atmosphere is 40 ° C. has the largest decrease in the degree of deaeration. That is, although there is a slight difference in the degree of decrease in the degree of degassing depending on the ink temperature (80 ° C., 90 ° C.), a result is obtained in which the degree of deaeration of the ink tends to decrease as the temperature difference between the ink and the atmosphere increases. Was. From the above measurement, in order to maintain the degree of deaeration after 7 days at 80% or more, it is preferable that the temperature difference between the ink in the ink tank and the atmosphere be 30 ° C. or less.

  Even under the condition that the ink temperature in the ink tank is different, if the temperature in the ink tank is maintained at a constant temperature, the influence of the difference in the ink temperature on the convection is small. On the other hand, the temperature difference between the ink temperature and the atmosphere greatly affects the convection of the ink in the ink tank regardless of the ink temperature. When the temperature difference between the ink and the atmosphere increases, the temperature of the ink tends to change depending on the air temperature, so that the temperature of the ink in the ink tank between the portion in contact with the atmosphere and other portions is likely to be generated. Therefore, as the temperature difference between the ink and the atmosphere increases, convection tends to occur in the ink tank, and the degree of degassing of the ink tends to decrease.

  It should be noted that the present invention is not limited to the configuration described in the above embodiment, and various modifications and changes can be made without departing from the configuration of the present invention.

  Reference Signs List 10 medium supply unit, 11 supply tray, 12 feeder board, 20 image forming main unit, 21 transfer unit, 22 image forming drum, 23 head unit, 24 irradiation unit, 25 delivery unit, 26 ink tank, 27 back pressure adjustment unit, 29 ink deaerator, 30 medium discharge unit, 31 discharge tray, 40 control unit, 41 CPU, 42 RAM, 43 ROM, 44 memory, 50 ink storage unit, 51 first ink supply unit, 52 second ink supply Section, 53 degasifier heating section, 54 ink tank heating section, 55 head heating section, 56 liquid level sensor, 57 ink, 58 lid member, 61 communication section, 62 operation display section, 69 bus, 71 transport drive section, 74 Irradiation drive unit, 100 inkjet recording device, 121, 122, 252, 253 roller, 123, 2 54 belt, 211 swing arm unit, 212 transfer drum, 221 drum heater, 230 inkjet head, 241 light shielding plate, 251 transfer roller, 731 head drive unit

Claims (9)

An ink degassing device for degassing ink,
A head unit for ejecting the ink,
When the amount of ink within a specified range for containing the ink provided and supplied at the downstream side of the ink deaerator is Acm ³ , and the contact area between the ink and the atmosphere at the ink amount A is Bcm ² An ink tank satisfying B ≦ 0.5A;
An ink tank heating unit for heating the ink in the ink tank,
A back pressure adjusting unit that adjusts a back pressure of the ink in the ink tank. The inkjet recording apparatus according to claim 1, further comprising a head heating unit configured to heat the head unit. An ink storage unit for storing the ink disposed upstream of the ink deaerator,
The ink jet recording apparatus according to claim 1, further comprising: an ink supply unit configured to supply the ink from the ink storage unit to the ink deaerator. The inkjet recording apparatus according to claim 1, further comprising an ink amount detection unit configured to detect an amount of the ink stored in the ink tank. The inkjet recording apparatus according to claim 4, further comprising a control unit that controls the amount of the ink in the ink tank so that B ≦ 0.5A. The ink jet recording apparatus according to any one of claims 1 to 5, further comprising an air blocking unit for partially blocking the contact between the ink and the atmosphere in the ink tank. The ink jet recording apparatus according to claim 6, wherein the air blocking unit is a lid member that covers the ink. The ink jet recording apparatus according to claim 7, wherein the lid member constitutes an ink amount detection unit for detecting the amount of the ink contained in the ink tank. An ink degassing device for degassing ink, a head unit for ejecting the ink, an ink tank provided downstream of the ink degassing device for containing the ink, and an ink in the ink tank. An ink tank heating unit for heating, a back pressure adjusting unit that adjusts the back pressure of the ink in the ink tank, a control method of an inkjet recording apparatus comprising:
When the volume of the ink in the ink tank is Acm ³ , and the contact area between the ink and the atmosphere in the ink amount A is Bcm ² , the ink in the ink tank is set so that B ≦ 0.5A. A method for controlling an ink jet recording apparatus for controlling an amount.

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