JP2018144419A - Inkjet recording device and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device which stabilizes a temperature of an ink flowing into an inkjet head to achieve improvement of injection characteristics, and to provide a control method of the inkjet recording device.SOLUTION: An inkjet recording device includes: a main tank; and a sub tank which stores an ink supplied from the main tank and heats the stored ink to a predetermined temperature. The inkjet recording device has: an inkjet head which discharges the ink heated by the sub tank from a nozzle to form images on each recording medium; and a passage formation part having a passage for supplying the ink from the sub tank to the inkjet head and serially having a cooling section where the ink passing from the sub tank to the inkjet head is cooled and a heating section where the passing ink is heated. Further, the inkjet recording device includes a pre-head heating part which is provided near the heating section of the passage formation part and heats the ink flowing through the heating section; and a control part which controls the pre-head heating part according to a flow rate of the ink flowing into the inkjet head.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an inkjet recording apparatus that performs image formation by ejecting heated ink onto a recording medium, and a control method for the inkjet recording apparatus.

  2. Description of the Related Art Conventionally, when an ink whose viscosity changes according to a temperature change is used in an ink jet recording apparatus, a method of heating ink stored in a main tank to lower the viscosity and supplying the ink to an ink jet head has been adopted. Since the viscosity of the ink supplied to the ink jet head affects the ejection characteristics when ink is ejected from the ink jet head, it is desired that the temperature of the ink be appropriately controlled.

  In Patent Document 1, the ink tank heating means is controlled in accordance with the amount of ink ejected from the inkjet head, so that the viscosity of the ink in the ink tank is optimized and the back pressure optimum for ink ejection is maintained. A configuration is disclosed.

JP 2003-145789 A

  However, even if the temperature of the ink is appropriately maintained in the ink tank, the temperature of the ink changes before reaching the ink jet head from the ink tank via the flow path. For this reason, it is difficult to keep the temperature constant when it is supplied to the inkjet head. Then, the ink viscosity in the ink jet head varies, and the ejection speed varies. Variations in the ejection speed cause density differences and gloss differences in the formed image.

  On the other hand, even when a heater for reheating the supplied ink is provided in the ink jet head, if the ink flow rate is low, the temperature of the ink reaching the ink jet head decreases in the ink supply path. In some cases, the heating in the inkjet head cannot catch up. If the heating in the ink jet head is not sufficiently performed and the ink viscosity becomes high, it causes a discharge failure. Therefore, there is a demand for a configuration that can maintain the temperature of the ink immediately before flowing into the inkjet head at a predetermined temperature even if the ink flow rate changes.

  Accordingly, an object of the present invention is to provide an ink jet recording apparatus and an ink jet recording apparatus control method in which the ejection characteristics are improved by stabilizing the temperature of the ink flowing into the ink jet head.

  In order to solve the above problems and achieve the object of the present invention, an ink jet recording apparatus according to the present invention stores a main tank in which ink is stored, ink stored in the main tank, and stored ink. And a sub-tank for heating to a predetermined temperature. In addition, an ink jet head that forms an image on a recording medium by discharging ink heated in the sub tank from the nozzle, and a flow path for supplying ink from the sub tank to the ink jet head, from the sub tank toward the ink jet head, It has a flow path formation part which has in order a cooling section which cools the ink which passes, and a heating section where the ink which passes passes is heated. Furthermore, a head preheating unit that is provided near the heating section of the flow path forming unit and heats the ink flowing through the heating section, and a control unit that controls the head preheating unit according to the flow rate of the ink flowing into the inkjet head, Is provided.

  In the inkjet recording apparatus of the present invention, the control unit sets the heating temperature of the head preheating unit according to the flow rate of the ink flowing into the inkjet head.

  According to the present invention, the temperature of the ink flowing into the ink jet head can be stabilized, and the ejection characteristics can be improved.

1 is an overall configuration diagram of an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2A is a schematic diagram of an internal configuration when the head unit is viewed from the side. FIG. 2B is a schematic diagram of an internal configuration when the head unit is viewed from the recording medium side. FIG. 3 is a configuration diagram illustrating an ink discharge mechanism including an ink supply unit and a head unit. It is the figure which expanded and showed the inkjet head and the head inflow vicinity. 1 is a block diagram of a control system of an ink jet recording apparatus according to a first embodiment of the present invention. It is the figure which showed the temperature conditions of the ink in a 1st subtank and an inkjet head. 3 is a flowchart illustrating a method for controlling the ink jet recording apparatus according to the first embodiment of the present invention. It is a figure which shows an example of the temperature control table of a head preheating part. 6 is a flowchart illustrating a method for controlling an ink jet recording apparatus according to a second embodiment of the present invention. 6 is a flowchart illustrating a method for controlling an ink jet recording apparatus according to a third embodiment of the present invention.

Hereinafter, an example of an inkjet recording apparatus and an inkjet recording apparatus control method according to an embodiment of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following examples. In each drawing described below, common members are denoted by the same reference numerals. The description will be given in the following order.
1. 1. First embodiment 1-1. Overall configuration of inkjet recording apparatus 1-2. Ink ejection mechanism 1-3. Configuration of control system 1-4. Temperature management in ink ejection mechanism 1-5. Inkjet recording device control method (example of calculating printing rate from image data and calculating ink flow rate)
2. Second Embodiment (Example of calculating a printing rate from an actual image and calculating an ink flow rate)
3. Third Embodiment (Example of calculating the ink flow rate from the amount of ink supplied to the tank per unit time)

1. First embodiment 1-1. Overall Configuration of Inkjet Recording Apparatus FIG. 1 is an overall configuration diagram of an inkjet recording apparatus 1 according to a first embodiment (hereinafter, this embodiment) of the present invention. As shown in FIG. 1, the ink jet recording apparatus 1 according to the present embodiment includes a paper feeding unit 10, an image forming unit 20, a paper discharge unit 30, an ink supply unit 40, and a control unit 100 (see FIG. 5). Have The ink jet recording apparatus 1 conveys the recording medium P stored in the paper feeding unit 10 to the image forming unit 20 under the control of the control unit 100, and forms an image on the recording medium P with the image forming unit 20. The formed recording medium P is discharged to the paper discharge unit 30.

[Paper Feeder]
The paper feed unit 10 includes a paper feed tray 11 that stores a recording medium P made of paper or the like, and a transport unit 12 that transports the recording medium P from the paper feed tray 11 to the image forming unit 20.

  The paper feed tray 11 is a plate-like member provided so that one or a plurality of recording media P can be placed thereon. The paper feed tray 11 is provided so as to move up and down in accordance with the amount of the recording medium P placed on the paper feed tray 11, and the uppermost recording medium P is transported by the transport unit 12 in the vertical movement direction. Held at the position.

  The conveyance unit 12 drives a ring-shaped belt 123 supported by a plurality of (for example, two) rollers 121 and 122 on the inside to convey the recording medium P on the belt 123, or on the paper feed tray 11. A supply unit (not shown) is provided for transferring the uppermost recording medium P placed thereon onto the belt 123. The transport unit 12 transports the recording medium P transferred from the supply unit onto the belt 123 so as to follow the belt 123.

[Image forming unit]
The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25, a delivery unit 26, and an image reading sensor 27.

  The image forming drum 21 is composed of a cylindrical member and is rotated counterclockwise by a drive motor (not shown). The image forming drum 21 carries the recording medium P along a cylindrical outer peripheral surface, and conveys the recording medium P along with its rotation. The conveyance surface of the image forming drum 21 faces the paper heating unit 23, the head unit 24, and the irradiation unit 25. The paper heating unit 23, the head unit 24, and the irradiation unit 25 are recorded by the image forming drum 21. Processing relating to image formation is performed on the medium P.

  As shown in FIG. 1, the delivery unit 22 is provided at a position interposed between the transport unit 12 of the paper feeding unit 10 and the image forming drum 21. The delivery unit 22 includes a claw part 221 that supports one end of the recording medium P conveyed by the conveyance part 12, a cylindrical delivery drum 222 that guides the recording medium P carried by the claw part 221, and the like. The recording medium P on the portion 12 is picked up by the claw portion 221 and is moved along the outer peripheral surface of the transfer drum 222 to guide the recording medium P in the direction along the outer peripheral surface of the image forming drum 21 and transfer it to the image forming drum 21. .

  The paper heating unit 23 includes, for example, a heating wire and generates heat in response to energization. The sheet heating unit 23 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and positioned upstream of the head unit 24 in the conveyance direction of the recording medium P by the rotation of the image forming drum 21. Under the control of the control unit 100, the paper heating unit 23 generates heat so that the recording medium P carried on the image forming drum 21 and passing through the vicinity of the paper heating unit 23 has a predetermined temperature.

  Further, a temperature sensor (not shown) is provided in the vicinity of the paper heating unit 23. Based on the temperature in the vicinity of the paper heating unit 23 detected by the temperature sensor, the control unit 100 causes the recording medium P carried on the image forming drum 21 and passing through the vicinity of the paper heating unit 23 to have a predetermined temperature. The operation of the paper heating unit 23 is controlled.

  The head unit 24 discharges ink to the recording medium P carried on the image forming drum 21 to form an image. The head unit 24 is individually provided for each color of C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, head units 24 are sequentially provided corresponding to the respective colors Y, M, C, and K from the upstream with respect to the conveyance direction of the recording medium P that is conveyed along with the rotation of the image forming drum 21.

  The head unit 24 of this embodiment is provided with a length (width) that covers the entire recording medium P in a direction perpendicular to the conveyance direction of the recording medium P (width direction of the recording medium P). That is, the ink jet recording apparatus 1 is a one-pass line head type ink jet recording apparatus. The head unit 24 can constitute a line head by arranging a plurality of inkjet heads 50 (see FIG. 2A).

  2A and 2B are diagrams showing an internal configuration of the head unit 24. FIG. FIG. 2A is a schematic diagram of the internal configuration when the head unit 24 is viewed from the side. FIG. 2B is a schematic diagram of an internal configuration when the head unit 24 is viewed from the recording medium P side. In addition, the figure which looked at the head unit 24 from the side is the case where the head unit 24 is seen from the surface along the vertical direction (X direction) of the paper surface of FIG. Show.

  As shown in FIGS. 2A and 2B, the head unit 24 includes a plurality of inkjet heads 50. 2A and 2B show an example in which 16 inkjet heads 50 are provided in two head units 24. The 16 ink jet heads 50 each constitute two ink jet heads 50 to form a set of eight ink jet modules 51.

  Each inkjet head 50 has a plurality of nozzles 52. The ink jet head 50 ejects ink from a plurality of nozzles 52 to form an image on the recording medium P carried on the image forming drum 21. That is, the inkjet head 50 is provided such that the plurality of nozzles 52 are exposed on the lower surface side of the head unit 24. As shown in FIG. 2B, each of the inkjet modules 51 including the two inkjet heads 50 includes nozzles 52 arranged in two rows along the X direction.

  The eight inkjet modules 51 form, for example, two rows along the X direction as shown in FIG. 2B. The two rows are arranged so that the inkjet modules 51 are staggered with respect to each other in a direction orthogonal to the X direction.

  The head unit 24 is individually provided for each color (CMYK) used for image formation. The inkjet recording apparatus 1 shown in FIG. 1 corresponds to each color in the order of colors Y, M, C, and K from the upstream along the conveyance direction of the recording medium P that is conveyed as the image forming drum 21 rotates. A head unit 24 is provided. The configuration of the inkjet head 50 in the head unit 24 and the ink ejection mechanism will be described in detail later.

  The irradiation unit 25 irradiates an energy beam for curing the ink after the ink used in the inkjet recording apparatus 1 of the present embodiment is ejected onto the recording medium P. The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp, and emits the fluorescent tube to emit energy rays such as ultraviolet rays. The irradiation unit 25 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and downstream of the head unit 24 in the conveyance direction of the recording medium P by the rotation of the image forming drum 21. The irradiation unit 25 irradiates the recording medium P carried on the image forming drum 21 and ejects the ink with energy rays, and cures the ink ejected onto the recording medium P by the action of the energy rays.

  As a fluorescent tube emitting ultraviolet rays, in addition to a low-pressure mercury lamp, a mercury lamp having an operating pressure of about several hundred Pa to 1 MPa, a light source usable as a germicidal lamp, a cold cathode tube, an ultraviolet laser light source, a metal halide lamp, a light emitting diode, etc. Is mentioned. Among these, a light source (for example, a light emitting diode) that can irradiate ultraviolet rays with higher illuminance and consumes less power is more desirable. The energy rays are not limited to ultraviolet rays, and may be any energy rays having a property of curing ink according to the properties of the ink, and the light source is replaced according to the wavelength of the energy rays.

  The delivery unit 26 conveys the recording medium P irradiated with energy rays from the irradiation unit 25 from the image forming drum 21 to the paper discharge unit 30. The delivery unit 26 rotates the annular belt 263 by a plurality of (for example, two) rollers 261 and 262 and conveys the recording medium P on the belt 263, and the recording medium P from the image forming drum 21. A cylindrical delivery drum 264 and the like are delivered to the transport mechanism. The delivery unit 26 conveys the recording medium P transferred to the belt 263 by the transfer drum 264 by the belt 263 and sends it to the paper discharge unit 30.

  The image reading sensor 27 is composed of an inline sensor or the like, and reads an image formed on the recording medium P discharged to the delivery unit 26. The read image data is sent to the control unit 100.

[Output section]
The paper discharge unit 30 stores the recording medium P sent out from the image forming unit 20 by the delivery unit 26. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31 and the like, and the recording medium P after image formation is placed on the paper discharge tray 31.

[Ink supply unit]
The ink supply unit 40 includes a main tank 41 (see FIG. 4) that stores ink, and supplies each color ink to the head unit 24 of the image forming unit 20. The ink supplied to the head unit 24 of the image forming unit 20 is ejected from each nozzle 52 of the inkjet head 50.

  The ink used in the inkjet recording apparatus 1 in the present embodiment is, for example, an ultraviolet (UV) curable ink. This UV curable ink changes phase between a gel state and a liquid (sol) state according to temperature in a state where UV is not irradiated. This ink has a phase change temperature of about 40 ° C. to 100 ° C., for example, and is uniformly liquefied (solified) by being heated and raised above the phase change temperature. On the other hand, the ink gels at a predetermined temperature or lower including a normal room temperature (0 ° C. to 30 ° C.).

1-2. Ink Ejection Mechanism Next, an ink ejection mechanism that is supplied from the ink supply unit 40 to the head unit 24 and is ejected from the inkjet head 50 will be described. Here, the ink discharge mechanism refers to a mechanism related to an operation of supplying ink from the ink supply unit 40 to the head unit 24 and discharging the ink from the plurality of nozzles 52 of the inkjet head 50. FIG. 3 is a configuration diagram illustrating an ink discharge mechanism including the ink supply unit 40 and the head unit 24. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The ink discharge mechanism includes a main tank 41, a first sub tank 64, a second sub tank 65, and an inkjet head 50. Further, the ink ejection mechanism includes a first piping unit 69 that connects the main tank 41 and the first sub tank 64, a second piping unit 70 that connects the first sub tank 64 and the second sub tank 65, and a second sub tank 65. And a flow path forming portion 43 that connects the inkjet head 50. The flow path forming unit 43 includes a third piping part 63 serving as a cooling section and a head inlet 61 serving as a heating section. Further, the ink ejection mechanism includes a fourth piping part 72 that connects the inkjet head 50 and the first sub tank 64, and a head preheating part 62. The ink jet recording apparatus 1 of the present embodiment is characterized in that the head pre-heating unit 62 is controlled according to the ink flow rate.

[Inkjet head]
First, the configuration of the inkjet head 50 that constitutes the ink ejection mechanism will be described. FIG. 4 is an enlarged view showing the vicinity of the inkjet head 50 and the head inlet 61. As shown in FIG. 4, the inkjet head 50 includes an inlet 53 connected to the head inlet 61, an upper channel portion 44 and a lower channel portion 57 that function as a channel for ink ejected from the inkjet head 50, It has an outlet 55 communicating with the four piping parts 72, a head control part 54, an in-head heater 58, and an in-head temperature detection part 60.

  The inlet 53 is formed of a cylindrical member, and one end is connected to the head inlet 61 and the other end is connected to the upper flow path portion 44. Both ends of the inlet 53 are opened, and communicate with the head inlet 61 and the upper flow path 44. As a result, the ink flowing from the head inlet 61 flows to the upper flow path portion 44 side via the inlet 53.

  The upper flow path portion 44 and the lower flow path portion 57 each have a flow path that guides the ink supplied to each of the plurality of nozzles 52 of the inkjet head 50 to the nozzle 52. The flow path is a common flow path shared by the plurality of nozzles 52 and guides the ink flowing through the inlet 53. That is, the ink supplied from the inlet 53 flows through the upper flow path portion 44 and the lower flow path portion 57 and reaches the plurality of nozzles 52.

  A filter 56 is provided between the upper flow path portion 44 and the lower flow path portion 57. Thereby, the ink flowing from the upper flow path portion 44 to the lower flow path portion 57 is filtered by the filter 56, and the ink in a state where impurities are removed can be supplied to the nozzle 52 side.

  A pressure chamber 59 is provided near the surface of the nozzle 52 below the lower flow path portion 57. The pressure chamber 59 applies pressure to the nozzles 52 corresponding to the ink ejected according to the image formed on the recording medium P under the control of the control unit 100 to eject the ink.

  The outlet 55 is provided on the opposite side of the position where the inlet 53 is provided across the region where the nozzle 52 is provided. Similarly to the inlet 53, the outlet 55 is configured by a cylindrical member, and has one end connected to the fourth piping part 72 and the other end connected to the upper flow path part 44. Both ends of the outlet 55 are opened, and communicate with the fourth piping part 72 and the upper flow path part 44. As a result, the ink that flows from the upper flow path portion 44 and is not ejected from the nozzle 52 is discharged to the fourth piping portion 72 side via the outlet 55. The outlet 55 may be connected to the fourth piping part 72 through a member having the same structure as the head inlet 61 connected to the inlet 53.

  The head control unit 54 is provided, for example, in the upper part of the upper flow path unit 44, and controls the operation of the pressure chamber 59 under the control of the control unit 100.

  The in-head temperature detection units 60 are provided at six locations in the upper flow path portion 44 and the lower flow path portion 57, and are arranged with predetermined intervals. The in-head temperature detection unit 60 detects the temperature of ink flowing in the upper flow path unit 44 and the lower flow path unit 57 under the control of the control unit 100.

  The in-head heater 58 is provided on the side surfaces of the upper flow path portion 44 and the lower flow path portion 57, and is composed of, for example, a heat transfer wire that generates heat in response to energization. The in-head heater 58 heats the ink flowing in the upper flow path portion 44 and the lower flow path portion 57 to a predetermined temperature under the control of the control unit 100. For example, the control unit 100 controls the operation of the in-head heater 58 based on the average value of the temperatures detected by the in-head temperature detection unit 60.

  Next, the main tank 41, the first sub tank 64, the second sub tank 65, the first piping part 69, the second piping part 70, the third piping part 63, and the head inlet 61 constituting the ink discharge mechanism are configured. The flow path forming unit 43, the head pre-heating unit 62, and the fourth piping unit 72 will be described.

[Main tank]
The main tank 41 stores ink circulated to each part of the ink discharge mechanism, and supplies the stored ink to the first sub tank 64. In the main tank 41, the ink is maintained at substantially normal temperature (room temperature), and the gel-like ink is supplied to the first sub tank 64.

[First sub tank]
The first sub tank 64 stores the ink supplied from the main tank 41 and heats the stored ink to a liquefaction temperature by a heating unit (not shown) provided in the first sub tank 64. The heating unit includes a heater and a heat transfer member that transmits heat from the heater, and heats and keeps the temperature of the ink in the first sub tank 64 at a predetermined temperature. For example, a heating wire that generates Joule heat when energized is used as the heater. In addition, as the heat transfer member, a member having high thermal conductivity, for example, a heat conduction plate formed of various metals (alloys) is used. The first sub-tank 64 is a container opened to the outside, and is maintained at substantially atmospheric pressure regardless of the increase or decrease in the amount of ink. Further, the first sub tank 64 is provided with a first liquid level sensor 64a, and the amount of ink stored in the tank can always be detected.

[Second sub tank]
The second sub tank 65 has a heating unit (not shown) for storing the ink supplied from the first sub tank 64 and holding the stored ink at the liquefaction temperature. About the structure of the heating part in the 2nd sub tank 65, it can be set as the structure similar to the heating part for heating the ink in the 1st sub tank 64. FIG. The second sub tank 65 is a sealed tank-like container except for various connection points.

  In addition, the second sub tank 65 is connected to the pressure control unit through an air passage, although not shown. The pressure control unit adjusts the pressure in the second sub tank 65 under the control of the control unit 100. For this reason, the pressure in the second sub tank 65 changes depending on the degree of negative pressure applied by a pressure control unit (not shown), whether ink is supplied from the first sub tank 64, and the like. The second sub tank 65 is provided with a second liquid level sensor 65a, and the amount of ink stored in the tank can always be detected.

  Since the pressure from the second sub-tank 65 to the inside of the inkjet head 50 is set to a negative pressure state by the pressure control unit, the ink is prevented from leaking from the nozzles 52 when image formation and various maintenance are not performed.

  In the ink jet recording apparatus 1 of the present embodiment, ink is supplied from one first sub tank 64 to a plurality of four second sub tanks 65 in the head unit 24, and each second sub tank is further configured. 65 is configured to supply ink to two inkjet heads 50.

[First piping section]
The first piping unit 69 is formed of a tube-shaped member that serves as an ink flow path, and connects the main tank 41 and the first sub tank 64 and communicates the inside of the main tank 41 and the inside of the first sub tank 64. As the 1st piping part 69, the tube formed with the resin material with favorable heat conductivity is used, for example. A first pump 66 is provided on the flow path of the first piping unit 69. The first pump 66 supplies ink from the main tank 41 to the first sub tank 64 under the control of the control unit 100. As the first pump 66, a positive displacement pump such as a diaphragm pump or a tube pump is used.

[Second piping section]
The second piping unit 70 is configured by a tube-shaped member that serves as an ink flow path, and connects the first sub tank 64 and the second sub tank 65, and the inside of the first sub tank 64 and the inside of the second sub tank 65. Communicate. As the 2nd piping part 70, the tube formed with the resin material with favorable heat conductivity is used, for example. On the flow path of the 2nd piping part 70, the 1st solenoid valve 67 and the 2nd pump 68 are provided in this order from the 1st sub tank 64 side. The first electromagnetic valve 67 opens and closes the flow path of the second piping unit 70 between the first sub tank 64 and the second pump 68 under the control of the control unit 100. The second pump 68 supplies ink from the first sub tank 64 to the second sub tank 65 under the control of the control unit 100. As the second pump 68, a positive displacement pump such as a diaphragm pump or a tube pump is used.

[Third piping section]
The third piping part 63 is formed of a tube-shaped member that serves as an ink flow path, and connects the second sub tank 65 and the head inlet 61 and communicates the inside of the second sub tank 65 and the head inlet 61. To do. As the 3rd piping part 63, it is comprised by the member which can cool the ink which flows through an inside by natural heat dissipation, for example, the tube formed with metal members, such as iron, is used. That is, the third piping part 63 becomes a cooling section in the flow path forming part 43, and the ink heated in the first sub tank 64 and the second sub tank 65 flows through the third piping part 63, and thus is cooled to some extent by natural heat dissipation. Then, the cooled ink is supplied to the head inlet 61.

[Head inlet]
The head inflow port 61 is formed of a metal member such as aluminum, and has a flow path through which ink flows. As shown in FIG. 4, the head inflow port 61 is a member disposed immediately before the inlet 53 of the inkjet head 50, a tube-like third piping part 63 is connected to one end, and the inlet of the inkjet head 50 is connected to the other end. 53 is connected. That is, the head inflow port 61 is a connecting portion between a third piping part 63 and an ink jet head 50 described later, and is incorporated in a casing constituting the head unit 24. At the time of assembling the head unit 24, when the ink jet head 50 is attached to the casing constituting the head unit 24, the inlet 53 of the ink jet head 50 is inserted into the head inlet 61, so that the flow path in the ink jet head 50 The third piping part 63 communicates with the head inlet 61.

  Furthermore, at the head inlet 61, the ink flowing inside can be heated by a head pre-heating unit 62 described later. That is, the head inlet 61 becomes a heating section in the flow path forming unit 43, and the ink flowing through the head inlet 61 is heated under the control of the control unit 100.

[Head preheating section]
The head pre-heating unit 62 is provided so as to contact the side wall surface of the head inlet 61. The head pre-heating unit 62 includes a heater and a heat transfer member that transmits heat from the heater, and heats and keeps the ink flowing in the head inlet 61 under the control of the control unit 100. For example, a heating wire that generates Joule heat when energized is used as the heater. In addition, as the heat transfer member, a member having high thermal conductivity, for example, a heat conduction plate formed of various metals (alloys) is used. A method for controlling the head pre-heating unit 62 will be described in detail later.

  The fourth piping section 72 is formed of a tube-shaped member that serves as an ink flow path, and connects the outlet 55 of the inkjet head 50 and the first sub tank 64 and communicates the inkjet head 50 and the inside of the first sub tank 64. . As the 4th piping part 72, the tube formed with the resin material with favorable heat conductivity is used, for example. A second electromagnetic valve 71 is provided on the flow path of the fourth piping part 72. The second electromagnetic valve 71 opens and closes the flow path of the fourth piping unit 72 between the outlet 55 and the first sub tank 64 under the control of the control unit 100. The ink remaining without being ejected from the inkjet head 50 can be collected in the first sub tank 64 by the fourth piping section 72.

  In the ink jet recording apparatus 1 having the above ink ejection mechanism, the ink heated to the predetermined temperature in the first sub tank 64 and the second sub tank 65 is once cooled by natural heat radiation in the third piping section 63. Thereafter, ink heated to a predetermined temperature by the head pre-heating unit 62 at the head inlet 61 is supplied into the inkjet head 50. The ink supplied to the inkjet head 50 is ejected from the nozzle 52 onto the recording medium in accordance with the input image signal.

1-3. Configuration of Control System Next, an internal configuration constituting the ink jet recording apparatus of the present embodiment will be described. FIG. 5 is a block diagram of a control system of the inkjet recording apparatus 1. As shown in FIG. 5, the control unit 100 of the inkjet recording apparatus 1 includes a paper supply unit 10, a paper discharge unit 30, an image forming drum 21, a delivery unit 22, a paper heating unit 23, and an irradiation unit. 25, the delivery unit 26, the image processing unit 28, and the image reading sensor 27 are connected to each other via the system bus 120. Furthermore, the control unit 100 includes a head preheating unit 62, a head heater 58, a head temperature detection unit 60, a head control unit 54, a first electromagnetic valve 67, a second electromagnetic valve 71, and a first electromagnetic valve. The liquid level sensor 64a, the second liquid level sensor 65a, the first pump 66, and the second pump 68 are connected to each other via the system bus 120. The control unit 100 controls the entire system that constitutes the inkjet recording apparatus 1.

  The control unit 100 includes, for example, a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 103 for storing a program executed by the CPU 101, and a RAM (Random Access Memory) 102 used as a work area of the CPU 101. And have. As the ROM 103, an electrically erasable programmable ROM is usually used.

  Image data transmitted from, for example, a personal computer (not shown), which is an external device connected to the image forming unit 20, is sent to the image processing unit 28, and image processing is performed in the image processing unit 28. Under the control of the control unit 100, the image processing unit 28 performs image processing such as shading correction, image density adjustment, and image compression on the received image data as necessary. Each unit of the image forming unit 20 forms an image on the recording medium P sent from the paper feeding unit 10 based on the image data processed by the image processing unit 28 under the control of the control unit 100. .

  Further, the image of the recording medium P discharged to the delivery unit 26 of the image forming unit 20 is detected by the image reading sensor 27, and the image data is sent to the control unit 100.

1-4. Here, temperature management of ink in the first sub tank 64, the second sub tank 65, and the inkjet head 50 will be described. FIG. 6 is a diagram showing the temperature conditions of the ink in the first sub tank 64 and the inkjet head 50.

  When the normal temperature gel-like ink stored in the main tank 41 is supplied to the first sub tank 64, the supplied gel-like ink needs to be heated and melted as needed in the first sub tank 64 to make it liquid. is there. Therefore, in the first sub tank 64, even when the maximum amount of gel-like ink is supplied from the main tank 41 when the amount of ink discharged from the nozzle 52 is maximum, that is, at the maximum discharge flow rate, the first sub tank 64 is melted at any time. The ink capacity and the ink temperature must be set to values that can be obtained.

  The appropriate values of the ink capacity and the ink temperature in the first sub tank 64 vary depending on the heat capacity of the ink, and the appropriate value of the temperature is defined as temperature A. If the temperature at which the ink gels is temperature D, then temperature A> temperature D.

  The second sub tank 65 has a role of supplying liquid ink to the inkjet head 50 side while generating back pressure, and the ink temperature of the second sub tank 65 is substantially the same as that of the first sub tank 64. Is set to When the ink temperature in the first sub-tank 64 and the second sub-tank 65 is lower than a predetermined temperature, the ink can be completely melted when the gel-like ink is supplied from the main tank 41 at the maximum discharge flow rate. Therefore, there arises a problem that ink having an appropriate viscosity cannot be supplied.

  On the other hand, the nozzle 52 constituting the inkjet head 50 is formed by bonding a plurality of substrates with an adhesive, and has a limit in heat resistance. That is, if ink of a certain temperature or higher is continuously supplied to the inkjet head 50, the substrate constituting the nozzle portion is heated too much, and there is a possibility that the adhesive breaks or the substrate is broken. If the heat resistant temperature of the ink jet head 50 that is generally used is temperature B, then temperature A> temperature B.

  Thus, there is a gap between the appropriate value of the ink temperature in the first sub tank 64 and the second sub tank 65 and the appropriate value of the ink temperature in the inkjet head 50. Therefore, it is necessary to cool the ink by the third piping part 63 before reaching the inkjet head 50 from the second sub tank 65. In the present embodiment, the third piping part 63 is configured by a metal member, and is naturally radiated. The ink is cooled. That is, it is necessary for the third piping part 63 that becomes a cooling section in the flow path forming part 43 to be configured to be able to lower the ink supplied at the temperature A to the temperature B or lower.

  By the way, in the configuration in which the ink in the flow path is cooled and supplied to the inkjet head 50 by natural heat dissipation, the temperature of the ink in the cooling section varies depending on the flow rate of the ink. For example, when the flow rate of the ink is large, hot ink constantly flows in the third piping part 63 that is the cooling section, so that the ink reaches the inkjet head 50 without being cooled much in the third piping part 63. On the other hand, when the ink flow rate is small, the heat of the ink is excessively dissipated in the third piping section, and the ink may be cooled too much. If the temperature of the ink reaching the ink-jet head 50 is too low, the clay of the ink becomes high and there is a risk of causing ejection failure.

  As shown in FIG. 4, an in-head heater 58 is also provided inside the inkjet head 50, but if the ink is cooled to a temperature below a certain temperature in the third piping section 63, this in-head heater The problem that the heating of the flowing ink cannot catch up with 58 alone occurs. Therefore, in the inkjet head 50, when the temperature of the ink at the time of ejection can be heated again to an appropriate value (that is, the heating catches up) is the lower limit temperature, the temperature of the ink reaching the inkjet head 50 is the temperature. It is necessary to keep it at C or higher.

  On the other hand, if the temperature A is increased so that the ink reaching the ink jet head 50 does not become the temperature C or lower when the ink flow rate is low, the ink reaching the ink jet head reaches the temperature B or lower when the flow rate is high. There is a case where the third piping part 63 cannot be cooled. In this case, the substrate constituting the nozzle portion may be damaged. For this reason, there is also an upper limit to the temperature setting value of the ink in the first sub tank 64 and the second sub tank 65, and the ink that reaches the ink jet head 50 when the temperature A setting value is increased and the ink flow rate is small. It cannot be prevented from being cooled below the temperature C.

  Due to such circumstances, in this embodiment, even when the ink flow rate is small and the temperature of the ink is cooled to the temperature C or less in the third pipe portion 63, the ink temperature E reaching the inkjet head 50 is set. The head preheating unit 62 performs control so that temperature C <temperature E <temperature B.

  Therefore, in the present embodiment, the head pre-heating unit 62 is controlled by the control unit 100 according to the ink flow rate, thereby appropriately controlling the ink temperature immediately before flowing into the inkjet head 50 and improving the ejection characteristics. Plan.

1-5. Inkjet recording device control method (example of calculating printing rate from image data and calculating ink flow rate)
A control method of the inkjet recording apparatus 1 of the present embodiment will be described. In the present embodiment, a configuration in which a print rate is calculated from image data, an ink flow rate is calculated from the print rate, and the head preheating unit 62 is controlled will be described. FIG. 7 is a flowchart showing a control method of the inkjet recording apparatus 1 of the present embodiment.

  First, the image processing unit 28 sends image data to be printed to the control unit 100 (step S1). The control unit 100 calculates the printing rate from the sent image data (step S2). When the printing rate is calculated, the control unit 100 calculates the flow rate of the ink reaching the inkjet head 50 per unit time from the printing rate (step S3).

  When the ink flow rate is calculated, the control unit 100 refers to the temperature control table of the head preheating unit 62 stored in advance in the ROM 103 (step S4). FIG. 8 shows an example of the temperature control table of the head preheating unit 62. The horizontal axis in FIG. 8 is the ink flow rate per unit time, and the vertical axis is the temperature setting value of the head preheating unit 62, which indicates the temperature setting value of the head preheating unit 62 with respect to the ink flow rate value. . Further, the temperature control table of the head pre-heating unit 62 shown in FIG. 8 is a control table when the head pre-heating unit 62 heats the ink reaching the inkjet head 50 so that the temperature reaches the temperature E shown in FIG. It is.

  The control unit 100 refers to the temperature control table based on the calculated ink flow rate, and the head preheating unit 62 in which the temperature of the ink reaching the inkjet head 50 becomes a predetermined temperature (temperature E in the present embodiment). Get the heating temperature. And the control part 100 changes the setting value of the head pre-heating part 62 according to the value of the heating temperature of the acquired head pre-heating part 62 (step S5). As shown in FIG. 8, for example, when the ink flow rate is X1, the temperature setting of the head pre-heating unit 62 is Y1. When the ink flow rate is X3, which is larger than X1, the temperature setting of the head preheating unit 62 is set to Y3. Further, when the ink flow rate is X2 larger than X1 and smaller than X3, the temperature setting of the head pre-heating unit 62 is set to Y2 lower than Y1 and higher than Y3. As a result, the temperature at which the ink reaches the inkjet head 50 can be maintained near the target temperature E.

  After the controller 100 changes the set value of the heating temperature of the head pre-heating unit 62, the image forming unit 20 starts printing.

  In the present embodiment, since the flow rate of the ink reaching the inkjet head 50 can be acquired in advance from the image data to be printed, the temperature of the ink reaching the inkjet head 50 can be appropriately controlled. Thereby, the stable injection characteristic can always be acquired.

  By the way, the structure which provides a temperature detection sensor in the head inflow port 61, and controls the head preheating part 62 based on the temperature detected with the temperature detection sensor is also considered. However, since the ink passing through the head inlet 61 is continuously supplied to the inkjet head 50 at the time of image formation, in the configuration in which the temperature detected by the temperature detection sensor is fed back to control the head preheating unit 62, the heat capacity of the ink Therefore, the control of the head pre-heating unit 62 cannot catch up with the temperature change of the ink.

  On the other hand, in the present embodiment, by calculating the ink flow rate from the image data in advance, it is possible to control the head pre-heating unit 62 by predicting the temperature of the ink flowing into the head inlet 61 in advance. The temperature of the ink flowing into the inkjet head 50 can be further stabilized.

  Further, in the present embodiment, by calculating the ink flow rate from the image data, the amount of ink scheduled to be discharged from each inkjet head 50 can be calculated. Therefore, the ink temperature can be adjusted for each inkjet head 50 by determining the set value of the head pre-heating unit 62 for each inkjet head 50. Thereby, the ejection characteristics can be improved for each inkjet head 50.

2. Second Embodiment (Example of calculating a printing rate from an actual image and calculating an ink flow rate)
Next, a control method of the ink jet recording apparatus 1 according to the second embodiment of the present invention will be described. In this embodiment, the configuration of the inkjet recording apparatus 1 is the same as that of the first embodiment, and only the control method is an example. In the present embodiment, a configuration in which a printing rate is calculated from an image printed on a recording medium P, an ink flow rate is calculated from the printing rate, and the head preheating unit 62 is controlled will be described. FIG. 9 is a flowchart showing a control method of the ink jet recording apparatus 1 of the present embodiment.

  In the present embodiment, first, the time point at which image formation on the recording medium is started in the image forming unit 20 is started (printing start). When printing is started and the recording medium P on which an image is formed is discharged to the delivery unit 26, the recording medium P is formed on the recording medium P by the image reading sensor 27 disposed in the vicinity of the delivery unit 26 under the control of the control unit 100. The processed image is read (step S21). The image read by the image reading sensor 27 is sent to the control unit 100, and the control unit 100 calculates the printing rate of the image (step S22).

  When the printing rate is calculated, the controller 100 calculates the flow rate of ink that reaches the inkjet head 50 per unit time from the printing rate (step S23).

  When the ink flow rate is calculated, the control unit 100 refers to the temperature control table of the head pre-heating unit 62 stored in advance in the ROM 103 (step S24). Thereafter, in the same procedure as steps S4 and S5 (see FIG. 7) in the first embodiment, the control unit 100 refers to the temperature control table, and the temperature of the ink reaching the inkjet head 50 is a predetermined temperature. The heating temperature value of the head preheating unit 62 is acquired. And the control part 100 changes the setting value of the head preheating part 62 corresponding to the heating temperature value of the acquired head preheating part 62 (step S25).

  In the present embodiment, it is possible to calculate the printing rate from the image formed on the first sheet, calculate the ink flow rate, and change the set value of the head preheating unit 62. For this reason, when the same image is formed on a plurality of recording media P, the ink flow rate does not change, so that it is possible to continue supplying ink with a stable temperature to the inkjet head 50 during subsequent image formation. . Thereby, the injection characteristic can be stabilized.

  In the present embodiment, the amount of ink discharged from each inkjet head 50 can be calculated by calculating the ink flow rate from the actual image. Therefore, the ink temperature can be adjusted for each inkjet head 50 by determining the set value of the head pre-heating unit 62 for each inkjet head 50. Thereby, the ejection characteristics can be improved for each inkjet head 50.

3. Third Embodiment (Example of calculating ink flow rate from pump driving time)
Next, a control method of the ink jet recording apparatus 1 according to the third embodiment of the present invention will be described. In this embodiment, the configuration of the inkjet recording apparatus 1 is the same as that of the first embodiment, and only the control method is an example. In the present embodiment, a configuration for controlling the head pre-heating unit 62 by calculating the ink flow rate from the pump drive time will be described. FIG. 10 is a flowchart showing a control method of the inkjet recording apparatus 1 of the present embodiment.

  In the present embodiment, as in the second embodiment, the start of image formation on the recording medium P in the image forming unit 20 is started (printing start). Next, the control unit 100 measures the drive time of the first pump 66 and the second pump 68 during image formation (step S31). The control unit 100 calculates the flow rate of ink reaching the inkjet head 50 per unit time from the drive time of the first pump 66 and the second pump 68 (step S32).

  When the ink flow rate is calculated, the control unit 100 refers to the temperature control table of the head preheating unit 62 stored in advance in the ROM 103 (step S33). Thereafter, in the same procedure as steps S4 and S5 (see the drawing) in the first embodiment, the control unit 100 refers to the temperature control table, and the temperature of the ink reaching the inkjet head 50 becomes a predetermined temperature. The heating temperature value of the head pre-heating unit 62 is acquired. And the control part 100 changes the setting value of the head preheating part 62 corresponding to the heating temperature value of the acquired head preheating part 62 (step S34).

  Also in the present embodiment, it is possible to calculate the ink flow rate from the driving time of the first pump 66 and the second pump 68, and to control the head pre-heating unit 62 accordingly. Therefore, the ink flowing into the head inlet 61 can be heated to a predetermined temperature as needed, and the ink heated to the optimum temperature can be supplied to the inkjet head 50.

  In the present embodiment, the ink flow rate is calculated from the driving time of the first pump 66 and the second pump 68. However, the ink flow rate is used per unit time by the first liquid level sensor 64a and the second liquid level sensor 65a. The ink flow rate may be calculated by detecting the amount of ink. In this case, the same effect as that of the third embodiment can be obtained.

  As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the configuration described in the above-described embodiment, and the configuration can be appropriately changed without departing from the gist thereof. Is.

  For example, in the present embodiment, the ink is cooled in the third pipe 63 and heated in the head inlet 61. However, when the third pipe 63 is directly connected to the inlet 53, the inlet 53 is used. It is good also as a structure which heats a part of 3rd piping part 63 in the vicinity. That is, any configuration may be used as long as a cooling section capable of cooling the ink is provided in the flow path from the second sub tank 65 to the inkjet head 50 and a heating section capable of heating the ink is provided immediately before the inlet 53.

  In the present embodiment, in the flow path forming unit 43, the cooling section is disposed on the upstream side with respect to the ink supply direction, and the heating section is disposed on the downstream side. . In addition, since the ink temperature immediately before flowing into the inkjet head 50 can be controlled by arranging the heating section just before the inlet 53 of the inkjet head 50 as in the present embodiment, the ink at a more appropriate temperature. Can be supplied to the inkjet head 50.

  Further, the above-described exemplary embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. For example, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Moreover, it is possible to add / delete / replace other configurations for a part of the configurations of the embodiments.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus, 10 ... Paper feed part, 20 ... Image formation part, 27 ... Image reading sensor, 28 ... Image processing part, 30 ... Paper discharge part, 40 ... Ink supply part, 41 ... Main tank, 43 ... Flow Path forming section, 44 ... upper flow path section, 50 ... inkjet head, 51 ... inkjet module, 52 ... nozzle, 53 ... inlet, 55 ... outlet, 58 ... heater in head, 60 ... temperature sensor in head, 61 ... head Inlet 62, head preheating unit, 63 ... third piping unit, 64 ... first sub tank, 65 ... second sub tank, 66 ... first pump, 68 ... second pump, 69 ... first piping unit, 70 ... 2nd piping part, 72 ... 4th piping part, 100 ... control part

Claims (11)

A main tank in which ink is stored;
A sub tank for storing the ink supplied from the main tank and heating the stored ink to a predetermined temperature;
An ink jet head that forms an image on a recording medium by ejecting ink heated in the sub tank from a nozzle;
A flow path for supplying ink from the sub tank to the inkjet head, and a cooling section for cooling the ink passing from the sub tank toward the ink jet head and a heating section for heating the ink passing therethrough. A flow path forming section;
A head pre-heating unit that is provided in the vicinity of the heating section of the flow path forming unit and heats the ink flowing in the heating section;
An ink jet recording apparatus comprising: a control unit that controls the head preheating unit in accordance with a flow rate of ink flowing into the ink jet head. The control unit calculates a flow rate of ink flowing into the inkjet head from a printing rate of an image formed on a recording medium, and controls a heating temperature in the head preheating unit according to the calculated flow rate of ink. The ink jet recording apparatus according to claim 1. The control unit calculates a print rate of the image from data of an image formed on a recording medium and calculates a flow rate of ink flowing into the inkjet head, and the head according to the calculated flow rate of ink. The inkjet recording apparatus according to claim 1, wherein the heating temperature in the preheating unit is controlled. The control unit calculates a flow rate of ink flowing into the inkjet head by detecting a flow rate of ink flowing into the sub-tank per unit time, and the head preheating is performed according to the calculated flow rate of ink. The inkjet recording apparatus according to claim 1, wherein the heating temperature in the section is controlled. The inkjet recording apparatus according to any one of claims 1 to 4, wherein the cooling section is configured by a tubular member that can cool the ink passing therethrough by natural heat dissipation. The inkjet recording apparatus according to claim 1, wherein the flow path forming unit has a cooling section on the upstream side in the ink supply direction and a heating section on the downstream side. The ink jet recording according to any one of claims 1 to 6, wherein the ink supplied to the ink jet head is a gel-like ink that liquefies at a temperature equal to or higher than a liquefaction temperature and gels at a temperature lower than the liquefaction temperature. apparatus. The sub tank is a tank capable of continuously supplying ink heated to a predetermined temperature or more to the inkjet head when the amount of ink discharged from the inkjet head per unit time is a maximum value. It has a capacity | capacitance. The inkjet recording device as described in any one of Claims 1-7. A plurality of inkjet heads are connected to the sub tank via the flow path forming unit,
The ink jet recording apparatus according to claim 1, wherein ink is supplied from the sub tank to the plurality of ink jet heads. A plurality of inkjet heads are connected to the sub tank via the flow path forming unit,
The ink jet recording apparatus according to claim 2, wherein ink is supplied from the sub tank to the plurality of ink jet heads. The heating temperature in the head preheating unit is controlled for each ink jet head. A main tank in which ink is stored;
A sub tank for storing the ink supplied from the main tank and heating the stored ink to a predetermined temperature;
An ink jet head that forms an image on a recording medium by ejecting ink heated in the sub tank from a nozzle;
A flow path for supplying ink from the sub tank to the inkjet head, and a cooling section for cooling the ink passing from the sub tank toward the ink jet head and a heating section for heating the ink passing therethrough. A flow path forming section;
A method for controlling an inkjet recording apparatus, comprising: a head pre-heating unit that is provided in the vicinity of a heating section of the flow path forming unit and that heats ink flowing in the heating section; and a control unit that controls the head pre-heating unit.
The said control part sets the heating temperature of the said head preheating part according to the flow volume of the ink which flows in into the said inkjet head. The control method of the inkjet recording device.

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