JP2009241316A - Liquid droplet delivering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a liquid droplet delivering device capable of efficiently cooling a head driver. <P>SOLUTION: A circulation flow path 116 connecting an discharging outlet of a head 88 with a recovering tank 104 is laid on a driver board 110. In the driver board 110, by driving an actuator for delivering ink, temperature of electronic components such as the head driver 112 is elevated. By laying the circulation flow path 116 on the driver board 110, a part where the circulation flow path 116 is laid becomes a driver cooling part 118, and the driver board 110 can be cooled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a droplet discharge device that discharges droplets such as ink.

  In recent years, the waste heat problem of the head driver has become a big issue due to the high density of the recording head. As a method of cooling the head driver, a method of attaching a heat sink and cooling with a fan is well known.

  In addition, in order to increase the droplet ejection accuracy, it is also well known in the art to perform ink temperature control to make the ink viscosity constant and to perform ink circulation to give a constant back pressure to the recording head. In this ink circulation system, in order to lower the ink temperature during circulation, a high output heater is mounted, or the entire system is heated by circulating hot water.

  That is, in the recording head, the head driver side is very inefficient in cooling and the ink circulation system is in heating.

  For example, in Patent Document 1, an ink tank is disposed at a position away from the print head, and ink is supplied from the ink tank to the print head. Each ink jet is controlled by an ink temperature control means having a temperature sensor. The temperature of the ink supplied to the nozzle is kept within the set temperature range.

  Further, in Patent Document 2, an ink supply channel for supplying ink from an ink tank to a droplet discharge head is mounted on a drive substrate and heat generated during operation of a drive circuit that drives the droplet discharge head is dissipated. It is provided so as to penetrate the heat sink.

Further, Patent Document 3 has a configuration in which waste ink discharged from a capping device is sent to an ink absorbing material via a waste ink tube, and a part of the waste ink tube is in contact with a heat sink. By disposing the head driver, the head driver whose temperature has increased due to heat generated by the waste ink flowing through the waste ink tube is cooled.
JP-A-10-175315 JP 2006-62125 A JP 2006-192577 A

  However, in Patent Document 1, a heater is provided in an ink tank, the temperature of the ink is increased, a temperature sensor is provided in the pressure chamber of the recording head, and the temperature of the ink is adjusted by the temperature sensor.

  Further, Patent Document 2 directly heats the ink supply path on the upstream side of the recording head. The temperature of the heat sink fluctuates depending on the driving state of the head driver, and high-precision ink temperature control cannot be performed. Further, since Patent Document 3 cools the head driver using the waste ink accumulated on the cap constituting the capping device, the head driver cannot be cooled if the waste ink does not have a sufficient flow rate. There are problems such as clogging.

  In view of the above facts, an object of the present invention is to provide a droplet discharge device that can efficiently cool a head driver.

  According to the first aspect of the present invention, in the droplet discharge device, the droplet discharge head that discharges the droplet from the nozzle, and the pressure in the pressure chamber that is provided in the droplet discharge head and is connected to the nozzle are changed. Droplet discharge means for discharging droplets from a nozzle, a driver substrate for driving the droplet discharge means, a supply tank for storing liquid, and the droplet discharge head and the supply drawn by the driver substrate A circulation channel for circulating the liquid between the tanks.

  In the first aspect of the invention, the droplet discharge head that discharges droplets from the nozzle is provided with droplet discharge means, and the droplet is discharged from the nozzle by changing the pressure in the pressure chamber connected to the nozzle. Let The droplet discharge means is driven by a driver substrate (a substrate on which a head driver for driving the droplet discharge means is disposed).

  The droplet discharge head discharges droplets from the nozzles, but excess liquid is discharged from the droplet discharge head. This liquid is returned to the supply tank and circulates. However, a circulation channel for circulating the liquid between the droplet discharge head and the supply tank is routed around the driver substrate.

  The temperature of the driver substrate rises by driving the droplet discharge means. Therefore, the driver substrate (by driving the circulation passage through which the liquid circulating between the droplet discharge head and the supply tank flows to the driver substrate ( The head driver can be cooled. Further, the liquid flowing through the circulation channel is heated by drawing the circulation channel around the driver substrate. That is, it has the effect of delaying the temperature drop of the liquid.

  Therefore, the output and quantity of the cooling device for cooling the driver substrate (head driver) can be reduced, and the output and quantity of the heater for heating the liquid can be reduced.

  According to a second aspect of the present invention, in the droplet discharge device according to the first aspect of the present invention, a bypass flow path that branches off from the circulation flow path and avoids the driver substrate is provided.

  In the invention described in claim 2, when the temperature of the driver substrate (head driver) is low by branching the bypass flow path for avoiding the driver substrate from the circulation flow path, the liquid is circulated using the bypass flow path. By cooling the liquid, it is possible to prevent cooling of the liquid.

  According to a third aspect of the present invention, in the liquid droplet ejection device according to the first or second aspect, the driver substrate has a driving waveform at a level at which no liquid droplet is ejected from the nozzle or a driving waveform at a level at which the liquid droplet is ejected. Is output.

  According to the third aspect of the present invention, in addition to the drive waveform at which the droplet discharge means discharges the droplet, a drive waveform at a level at which the droplet is not discharged from the nozzle is output, so that the droplet by the droplet discharge head is output. Even when there is no discharge, since the droplet discharge means can be driven, the liquid around the nozzle can be prevented from solidifying.

  According to a fourth aspect of the present invention, in the droplet discharge device according to any one of the first to third aspects, a cooling unit that cools the driver substrate, and a temperature measuring unit that measures a temperature of the driver substrate; The cooling means is operated when the temperature measured by the temperature measuring unit is equal to or higher than a predetermined temperature.

  In the invention according to claim 4, when the temperature measured by the temperature measuring unit is equal to or higher than a predetermined temperature, it is possible to control the driver substrate (head driver) so as not to exceed the predetermined temperature by operating the cooling means. it can.

  Since the present invention has the above configuration, the head driver can be efficiently cooled.

  Hereinafter, an image forming apparatus provided with a conveyance body according to an embodiment of the present invention will be described.

First, the overall configuration of the image forming apparatus 10 will be described.
[Image forming apparatus]
As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment feeds and feeds paper to the upstream side in the transport direction of a sheet as a recording medium (hereinafter referred to as “paper”). A portion 12 is provided. On the downstream side of the paper feeding / conveying unit 12, a processing liquid applying unit 14 for applying a processing liquid to the recording surface of the paper along the paper conveying direction, an image forming unit 16 for forming an image on the recording surface of the paper, An ink drying unit 18 that dries an image formed on the recording surface, an image fixing unit 20 that fixes the dried image on a sheet, and a discharge unit 21 that discharges the sheet on which the image is fixed are provided.

Hereinafter, each processing unit will be described.
(Paper feed section)
The paper feeding / conveying unit 12 is provided with a stacking unit 22 on which sheets are stacked, and downstream of the stacking unit 22 in the sheet conveying direction (hereinafter, the “sheet conveying direction” may be omitted). A paper feeding unit 24 is provided for feeding the paper stacked on the stacking unit 22 one by one.The paper fed by the paper feeding unit 24 is transported by a plurality of pairs of rollers 26. After passing through the part 28, it is conveyed to the treatment liquid application part 14.
(Processing liquid application part)
In the treatment liquid application unit 14, a treatment liquid application drum 30 is rotatably disposed. The processing liquid coating drum 30 is provided with a holding member 32 that holds the paper by sandwiching the leading end of the paper, and the paper is held on the surface of the processing liquid coating drum 30 via the holding member 32. In this state, the sheet is conveyed downstream by the rotation of the treatment liquid coating drum 30.

  Note that an intermediate conveying drum 34, an image forming drum 36, an ink drying drum 38, and an image fixing drum 40, which will be described later, are also provided with a holding member 32 in the same manner as the processing liquid coating drum 30. The holding member 32 transfers the paper from the upstream drum to the downstream drum.

  A processing liquid coating device 42 and a processing liquid drying device 44 are disposed above the processing liquid coating drum 30 along the circumferential direction of the processing liquid coating drum 30. The treatment liquid is applied to the surface, and the treatment liquid is dried by the treatment liquid drying device 44.

  Here, the treatment liquid reacts with the ink to aggregate the color material (pigment) and has an effect of promoting separation of the color material (pigment) and the solvent. The treatment liquid application device 42 is provided with a storage portion 46 for storing the treatment liquid, and a part of the gravure roller 48 is immersed in the treatment liquid.

  A rubber roller 50 is disposed in pressure contact with the gravure roller 48, and the rubber roller 50 contacts the recording surface (front surface) side of the paper to apply the processing liquid. Further, a squeegee (not shown) is in contact with the gravure roller 48 to control the amount of treatment liquid applied to the recording surface of the paper.

  Ideally, the treatment liquid film thickness is sufficiently smaller than the droplets of the head droplets. For example, when the droplet volume is 2 pl, the average diameter of the droplets of the head droplet is 15.6 μm, and when the treatment liquid film thickness is thick, the ink dots float in the treatment liquid without contacting the recording surface of the paper. To do. In order to obtain a landing dot diameter of 30 μm or more with a droplet ejection amount of 2 pl, it is preferable to set the treatment liquid film thickness to 3 μm or less.

  On the other hand, in the treatment liquid drying device 44, a hot air nozzle 54 and an infrared heater 56 (hereinafter referred to as “IR heater 56”) are disposed close to the surface of the treatment liquid application drum 30. The hot air nozzle 54 and the IR heater 56 evaporate a solvent such as water in the processing liquid to form a solid or thin film processing liquid layer on the recording surface side of the paper. By thinning the treatment liquid in the treatment liquid drying step, the dots deposited by ink in the image forming unit 16 come into contact with the surface of the paper to obtain the required dot diameter, and react with the thinned treatment liquid. It is easy to obtain an action of agglomerating color materials and fixing to the paper surface.

In this way, the paper on which the processing liquid has been applied and dried on the recording surface by the processing liquid application unit 14 is conveyed to an intermediate conveyance unit 58 provided between the processing liquid application unit 14 and the image forming unit 16.
(Intermediate transport section)
An intermediate transport drum 58 is rotatably provided in the intermediate transport unit 58, and a sheet is held on the surface of the intermediate transport drum 34 via a holding member 32 provided in the intermediate transport drum 34. The sheet is conveyed downstream by the rotation of 34.
(Image forming part)
An image forming drum 36 is rotatably provided in the image forming unit 16, and a sheet is held on the surface of the image forming drum 36 via a holding member 32 provided on the image forming drum 36. The sheet is conveyed downstream by the rotation of 36.

  A head unit 66 composed of a single-pass ink-jet line head (droplet discharge device) 64 is disposed near the surface of the image forming drum 36 (described later). ). In this head unit 66, at least YMCK inkjet line heads 64Y, 64M, 64C, and 64K, which are basic colors, are arranged along the circumferential direction of the image forming drum 36, and are formed on the recording surface of the paper by the processing liquid application unit 14. An image of each color is formed on the treated liquid layer.

  The treatment liquid has the effect of aggregating the color material (pigment) and latex particles dispersed in the ink into the treatment liquid, and forms an aggregate that does not generate color material flow on the paper. As an example of the reaction between the ink and the treatment liquid, acid is contained in the treatment liquid, pigment dispersion is destroyed by PH down, and the color material bleeds using a mechanism of aggregation, color mixing between each color ink, liquid mixture at the time of ink droplet landing Avoids droplet-interference caused by

  The ink jet line head 64 performs droplet ejection in synchronization with an encoder (not shown) that detects the rotational speed disposed on the image forming drum 36, thereby determining the landing position with high accuracy and at the same time. Irregular droplet ejection can be reduced without depending on the shake, the accuracy of the rotary shaft 68, and the drum surface speed.

  The head unit 66 can be retracted from the upper part of the image forming drum 36, and maintenance operations such as cleaning the nozzle surface of the inkjet line head 64 and discharging the thickened ink, the head unit 66 is moved to the upper part of the image forming drum 36. It is carried out by evacuating from.

The sheet on which the image is formed on the recording surface is conveyed to an intermediate conveyance unit 70 provided between the image forming unit 16 and the ink drying unit 18 by the rotation of the image forming drum 36. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof is omitted.
(Ink drying section)
An ink drying drum 38 is rotatably provided in the ink drying unit 18, and a plurality of hot air nozzles 72 and IR heaters 74 are arranged above the ink drying drum 38 in the vicinity of the surface of the ink drying unit 18. It is installed.

  Here, as an example, the pair of IR heaters 74 arranged in parallel with the hot air nozzles 72 are alternately arranged so that the hot air nozzles 72 are arranged on the upstream side and the downstream side. In addition to this, a large number of IR heaters 74 are arranged on the upstream side to irradiate a large amount of thermal energy on the upstream side to increase the temperature of moisture, and a large number of hot air nozzles 72 are arranged on the downstream side to blow off saturated water vapor. Also good.

  Here, the hot air nozzle 72 is arranged so that the blowing angle of the hot air is inclined toward the rear end side of the paper. Accordingly, the flow of hot air from the hot air nozzle 72 can be collected in one direction, and the paper is pressed against the ink drying drum 38 side, and the state where the paper is held on the surface of the ink drying drum 38 can be maintained. it can.

  The hot air generated by the hot air nozzle 72 and the IR heater 74 dries the solvent separated by the color material aggregating action in the paper image forming unit, thereby forming a thin image layer.

  The hot air is usually set to 50 ° C. to 70 ° C., although it varies depending on the sheet conveyance speed. The evaporated solvent is discharged together with air to the outside of the image forming apparatus 10, but the air is recovered. This air may be cooled by a cooler / radiator or the like and recovered as a liquid.

The sheet on which the image on the recording surface is dried is conveyed to an intermediate conveyance unit 76 provided between the ink drying unit 18 and the image fixing unit 20 by the rotation of the ink drying drum 38. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof is omitted.
(Image fixing part)
An image fixing drum 40 is rotatably provided in the image fixing unit 20. In the image fixing unit 20, latex particles in a thin image layer formed on the ink drying drum 38 are heated / pressurized. And has a function of fixing and fixing on the paper.

  A heating roller 78 is disposed above the image fixing drum 40 in the vicinity of the surface of the image fixing drum 40. The heating roller 78 has a halogen lamp incorporated in a metal pipe made of aluminum or the like having a good thermal conductivity. The heating roller 78 applies heat energy equal to or higher than the Tg temperature of the latex. As a result, the latex particles are melted and pressed into the irregularities on the paper for fixing, and the irregularities on the image surface are leveled to obtain glossiness.

  A fixing roller 80 is provided on the downstream side of the heating roller 78. The fixing roller 80 is disposed in pressure contact with the surface of the image fixing drum 40 so as to obtain a nip force with the image fixing drum 40. I have to. Therefore, at least one of the fixing roller 80 and the image fixing drum 40 has an elastic layer on the surface and a uniform nip width with respect to the paper.

  The sheet on which the image on the recording surface is fixed by the above-described process is conveyed to the discharge unit 21 side provided on the downstream side of the image fixing unit 20 by the rotation of the image fixing drum 40.

  In this embodiment, the image fixing unit 20 has been described. However, the image fixing unit 20 is not necessarily required because it is sufficient that the image formed on the recording surface can be dried and fixed by the ink drying unit 18.

  Next, a droplet discharge device according to an embodiment of the present invention will be described.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the head unit 66 as the droplet discharge device includes a plurality of inks provided corresponding to yellow (Y), magenta (M), cyan (C), and black (K) inks. Ink jet line heads 64Y, 64M, 64C, and 64K are provided, and are arranged in order from the upstream side along the transport direction of the paper P.

  Each inkjet line head 64K, 64C, 64M, 64Y has an ink tank 67 in which the corresponding color ink is stored, and each ink tank 67 is connected to each inkjet line head 64K, 64C via a required pipe line. , 64M, 64Y communicates with a supply tank 94 (see FIG. 5) described later. When the remaining amount of ink in each supply tank 94 decreases, ink is supplied from the corresponding ink tank 67.

  Further, as shown in FIG. 2, each of the inkjet line heads 64Y, 64M, 64C, and 64K has a length corresponding to the maximum paper width of the paper P conveyed by the image forming drum 36. This is a full-line head in which a plurality of ink ejection nozzles 82 are arranged over the entire width of the maximum size paper P that can be drawn.

  As described above, according to the configuration in which the full line type inkjet line heads 64Y, 64M, 64C, and 64K having nozzle rows covering the entire width of the paper are provided for each color, the transport direction of the paper P (arrow A direction; sub-scanning direction) ), The image can be recorded on the entire surface of the sheet P only by performing the operation of relatively moving the sheet P and the printing unit once (that is, by one sub-scan). Thereby, high-speed printing is possible and productivity can be improved as compared with a shuttle type head in which the head reciprocates in a direction (arrow B direction; main scanning direction) orthogonal to the paper transport direction.

  In this example, the configuration of the standard colors (4 colors) of YMCK is exemplified, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add an inkjet line head that discharges light-colored ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited.

  Here, the structure of the inkjet line heads 64Y, 64M, 64C, and 64K will be described. Since the structures of the inkjet line heads 64Y, 64M, 64C, and 64K for each color are the same, they are denoted by reference numeral 64 below.

  FIG. 3 is a plan perspective view showing a structural example of the inkjet line head 64, and FIG. 4 is an enlarged view of a part thereof. FIG. 5 is a cross-sectional view (a cross-sectional view taken along line 5-5 in FIG. 4) showing a three-dimensional configuration of one droplet discharge element (an ink chamber unit 86 corresponding to one nozzle 82).

  In order to increase the dot pitch printed on the paper P, it is necessary to increase the nozzle pitch in the inkjet line head 64. As shown in FIG. 3, the inkjet line head 64 of this example includes a plurality of ink chamber units (droplet discharge elements) 86 including nozzles 82 serving as ink discharge ports and pressure chambers 84 corresponding to the nozzles 82. The nozzles are arranged in a zigzag matrix (two-dimensionally), so that a substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the longitudinal direction of the head (main scanning direction). High density is achieved.

  As shown in FIG. 6, the inkjet line head 64 includes a plurality of heads 88, and these heads 88 are integrally connected to each other so as to be substantially orthogonal to the transport direction of the paper P (main scanning direction). In addition, one or more nozzle rows are formed over a length corresponding to the entire width of the paper P.

  As shown in FIG. 3, the pressure chamber 84 provided corresponding to each nozzle 82 has a substantially square planar shape, and has an outlet 83 to the nozzle 82 at one of the diagonal corners. The other side is provided with a supply ink inlet (supply port) 90. The shape of the pressure chamber 84 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse.

  As shown in FIGS. 2 and 5, each pressure chamber 84 communicates with the individual inflow channel 91 via the ink inlet 90. This individual inflow channel 91 is provided for each nozzle 82, and each individual inflow channel 91 communicates with a common channel 92. The common flow path 92 communicates with a supply tank 94 serving as an ink supply source, and ink supplied from the supply tank 94 passes through the supply port 96 and the common flow path 92, and passes through the individual inflow flow path 91 and the ink inflow port 90. Via the pressure chamber 84.

  In addition, the individual outflow passage 100 communicates with the outlet 83 to the nozzle 82. Each individual outflow channel 100 communicates with the circulation common channel 101, and excess ink is guided to the circulation common channel 101. The circulation common flow path 101 is connected to the recovery tank 104 via the discharge port 102, and the ink guided to the discharge port 102 is recovered by the recovery tank 104, and a pump 106 that connects between the recovery tank 104 and the supply tank 94. Is circulated to the supply tank 94 (described later).

  Furthermore, an actuator (droplet discharge means) 108 provided with individual electrodes is joined to a diaphragm 105 that also serves as a common electrode constituting a part of the pressure chamber 84 (the top surface in FIG. 5). Yes. The actuator 108 is deformed by applying a driving voltage between the individual electrode 107 and the common electrode by a head driver 112 (see FIG. 6) such as a driving IC disposed on the driver substrate 110 (see FIG. 6). As a result, the volume of the pressure chamber 84 changes, and ink is ejected from the nozzles 82 due to the pressure change accompanying this.

  For the actuator 108, a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate is preferably used. After the ink is ejected, when the displacement of the actuator 108 is restored, new ink is refilled into the pressure chamber 84 from the common flow path 92 through the ink inlet 90.

  By controlling the driving of the actuator 108 corresponding to each nozzle 82 according to the dot arrangement data generated from the image information, ink droplets can be ejected from the nozzle 82. As described with reference to FIG. 1, a desired image can be recorded on a sheet by conveying the sheet at a constant speed and controlling the ink discharge timing of each nozzle 82 in accordance with the conveyance speed.

  As shown in FIG. 3, the ink chamber unit 86 having the above-described structure is constant along the row direction along the main scanning direction (arrow direction) and the oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number of lattice patterns in an array pattern.

  That is, with a structure in which a plurality of ink chamber units 86 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles 82 projected in the main scanning direction is d ×. cos θ, and in the main scanning direction, each nozzle 82 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which the number of nozzle rows projected so as to be aligned in the main scanning direction is 2400 per inch (2400 nozzles / inch).

  In carrying out the present invention, the nozzle arrangement structure is not limited to the illustrated example. In this embodiment, a method of ejecting ink droplets by deformation of the actuator 108 typified by a piezo element (piezoelectric element) is employed. However, the method of ejecting ink is not particularly limited in the implementation of the present invention. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

  Further, when printing is not performed for a long time, the actuator 108 is driven to drive at a level that does not cause ink to be ejected from the nozzles 82 (repeated movement of the ink surface between the solid and virtual lines) as shown in FIG. Like that. Thereby, even when ink is not ejected by the inkjet line head 64, the liquid around the nozzle 82 can be prevented from solidifying.

  Incidentally, as shown in FIGS. 5 and 8, the ink stored in the supply tank 94 is supplied to the head 88 constituting the inkjet line head 64, but if the temperature of the ink is too low, the ink is stored in the ink. Will increase the viscosity and affect the image quality.

  For this reason, a heater 114 is provided in the inkjet line head 64 to heat the ink supplied from the supply tank 94 to the common flow path 92. Thus, the ink is accurately temperature-controlled and supplied to the common flow path 92 with an appropriate viscosity.

  On the other hand, in the inkjet line head 64, the excess ink flows into the individual outflow channel 100 and is guided to the recovery tank 104 via the discharge port 102. In the present embodiment, FIG. As shown in FIGS. 6 and 8, a circulation channel 116 connecting the discharge port 102 and the recovery tank 104 is routed around the driver substrate 110. Since the inkjet line head 64 is configured by integrally connecting a plurality of heads 88, the circulation flow path 116 is drawn around the plurality of driver substrates 110.

  Each head 88 includes a driver board 110 and a control board 111, and a head driver 112 such as a driving IC provided on the driver board 110 is controlled by a controller (not shown) provided on the control board 111. The The actuator 108 is driven by the head driver 112, but when the actuator 108 is driven, the temperature of the head driver 112 rises.

  On the other hand, when the circulation flow path 116 is routed around the driver substrate 110 (particularly near the head driver 112), the portion where the circulation flow path 116 is routed becomes the driver cooling unit 118, and the head driver 112 can be cooled. . Further, by drawing the circulation channel 116 around the driver substrate 110, the ink flowing through the circulation channel 116 is heated. That is, it has the effect of delaying the temperature drop of the ink.

  Accordingly, the output and quantity of the cooling fan for cooling the head driver 112 can be reduced, and the output and quantity of the heater 114 provided in the inkjet line head 64 for heating the ink can be reduced. it can.

  From the simulation results of the present embodiment, the ink circulation amount necessary for cooling the head driver 112 was 200 to 300 ml / min. Since the actual ink circulation rate is 5.4 ml / sec = 324 ml / min, it is almost equivalent.

  Further, in the present invention, the head driver 112 is efficiently cooled by drawing the circulation flow path 116 around the driver substrate 110, and the present invention is not limited to this embodiment.

  For example, as shown in FIG. 9, a bypass channel 120 is provided separately from the circulation channel 116 that connects the discharge port 102 (see FIG. 5) of the head 88 and the recovery tank 104, and the bypass channel 120 is provided in the driver substrate 110. It is made to collect | recover directly to the collection | recovery tank 104 from the discharge port 102 without drawing around. When the temperature of the head driver 112 is low, cooling of the ink can be prevented by flowing the ink to be circulated using the bypass flow path 120.

  Further, by routing the circulation flow path 116 to the driver substrate 110, the portion where the circulation flow path 116 is routed becomes the driver cooling unit 118, and the head driver 112 can be cooled, but as shown in FIG. A cooling fan (cooling means) 122 that cools the head driver 112 and a temperature sensor (temperature measurement unit) 124 that measures the temperature of the head driver 112 may be disposed on the driver board 110. When the temperature measured by the temperature sensor 124 is equal to or higher than the predetermined temperature, the head driver 112 can be controlled not to exceed the predetermined temperature by operating the cooling fan 122.

  Further, in FIG. 11, heaters 126 and 128 may be disposed in the supply tank 94 and the recovery tank 104, respectively. Thereby, the temperature adjustment accuracy of the ink circulating through the supply tank 94, the inkjet line head 64, the circulation flow path 116, and the recovery tank 104 can be increased.

  In the above embodiment, the recovery tank 104 is provided. However, as shown in FIG. 12, the supply tank 130 may also have a recovery tank. In this case, a recovery tank is substantially unnecessary, and the inkjet line head 64 and the supply tank 94 are connected by the circulation channel 116.

  In the above embodiment, an image forming apparatus that discharges ink and forms an image on a sheet has been described. However, the liquid to be discharged is not limited to ink. For example, drying for various industrial applications, such as forming bumps for component mounting by discharging molten solder onto the substrate, and forming EL display panels by discharging organic EL solution onto the substrate The present invention can be applied to all devices.

1 is an overall configuration diagram illustrating a configuration of an image forming apparatus. It is a plane perspective view which shows the structural example of the inkjet line head which concerns on this Embodiment. It is a plane perspective view which shows the structural example of the inkjet line head which concerns on this Embodiment. FIG. 4 is a partially enlarged view of FIG. 3. FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4 illustrating an example of the structure of the inkjet line head according to the present embodiment. It is a perspective view which shows the inkjet line head which concerns on this Embodiment. FIG. 6 is a partially enlarged view of FIG. 5. It is a schematic diagram which shows the structure of the inkjet line head which concerns on this Embodiment. It is the 1st modification of the mimetic diagram showing the composition of the ink jet line head concerning this embodiment. It is the 2nd modification of the schematic diagram which shows the structure of the inkjet line head which concerns on this Embodiment. It is the 3rd modification of the schematic diagram which shows the structure of the inkjet line head which concerns on this Embodiment. It is a 4th modification of the schematic diagram which shows the structure of the inkjet line head which concerns on this Embodiment.

Explanation of symbols

10 Image forming apparatus 64 Inkjet line head (droplet discharge head, droplet discharge apparatus)
66 Head unit (Droplet ejection device)
82 Nozzle 84 Pressure chamber 86 Ink chamber unit 88 Head (droplet discharge head)
104 Recovery tank 108 Actuator (Droplet discharge means)
DESCRIPTION OF SYMBOLS 110 Driver board | substrate 112 Head driver 116 Circulation flow path 120 Bypass flow path 122 Cooling fan (cooling means)
124 Temperature sensor (temperature measurement unit)
130 Supply tank (recovery tank)

Claims (4)

A droplet discharge head for discharging droplets from a nozzle;
A droplet discharge means provided in the droplet discharge head, for changing the pressure in the pressure chamber connected to the nozzle and discharging the droplet from the nozzle;
A driver substrate for driving the droplet discharge means;
A supply tank in which liquid is stored;
A circulation channel that is drawn around the driver substrate and circulates a liquid between the droplet discharge head and the supply tank;
A droplet discharge device having   The droplet discharge device according to claim 1, further comprising a bypass channel that branches off from the circulation channel and avoids the driver substrate.   3. The droplet discharge device according to claim 1, wherein the driver substrate outputs a drive waveform at a level at which no droplet is discharged from the nozzle or a drive waveform at a level at which a droplet is discharged. Cooling means for cooling the driver substrate;
A temperature measuring unit for measuring the temperature of the driver board,
The droplet discharge device according to claim 1, wherein the cooling unit is activated when a temperature measured by the temperature measuring unit is equal to or higher than a predetermined temperature.

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