Droplet ejection head

Abstract

A droplet ejection head according to the present disclosure includes: a flow path member; a heater; and a detection unit. The flow path member includes a nozzle surface in which a plurality of ejection holes are opened. The heater is positioned inside a head body configured to include the flow path member. The detection unit is positioned inside the head body and detects the temperature inside the head body. The detection unit is positioned closer to the nozzle surface than the heater.

Description

droplet ejection head

[0001] The present disclosure relates to droplet ejection heads.

[0002] Conventionally, droplet ejection heads that eject droplets onto a recording medium to perform various printing operations have been known as print heads. Patent Document 1 discloses a printing device that includes multiple heaters that heat the print head and heater drivers that independently drive the multiple heaters.

[0003] Japanese Unexamined Patent Publication No. 6-115074

[0004] A droplet ejection head according to one aspect of the present disclosure includes a flow path member, a heater, and a detection unit. The flow path member has a nozzle surface with a plurality of ejection holes. The heater is located inside a head main body that includes the flow path member. The detection unit is located inside the head main body and detects the temperature inside the head main body. The detection unit is also located closer to the nozzle surface than the heater.

[0005] FIG. 1 is a schematic side view of a printer according to a first embodiment. FIG. 2 is a schematic plan view of the printer according to the first embodiment. FIG. 3 is an exploded perspective view showing a schematic configuration of a droplet ejection head according to the first embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a perspective view showing the configuration of a plate-like member according to the first embodiment. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 3. FIG. 7 is a perspective view showing the configuration of a plate-like member according to a second embodiment. FIG. 8 is a cross-sectional view of a droplet ejection head according to the second embodiment. FIG. 9 is a plan view of a first substrate and a second substrate according to a third embodiment.

[0006] Hereinafter, a detailed description will be given of a droplet ejection head according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments are designated by the same reference numerals, and redundant explanations will be omitted.

[0007] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0008] In the drawings referred to below, for ease of understanding, the X-axis, Y-axis, and Z-axis directions are defined as being orthogonal to each other, and an orthogonal coordinate system is shown in which the positive Z-axis direction is the vertically upward direction. The rotation direction around the vertical axis is also referred to as the θ direction.

[0009] It is known that by maintaining a constant temperature inside the droplet ejection head or the temperature of the ink flowing inside the droplet ejection head, the viscosity of the ink can be maintained constant and the ink ejection state can be stabilized. For this reason, a heater and a temperature sensor are provided inside the droplet ejection head to adjust the ink temperature.

[0010] To stabilize the ink ejection state, it is preferable to maintain a constant temperature of the ink immediately before it is ejected from the nozzle surface. However, if the temperature sensor is located relatively far from the nozzle surface, the temperature sensor may not be able to detect a drop in the temperature of the nozzle surface, or even if it can, the detection may be delayed, making it impossible to properly adjust the temperature of the ink immediately before it is ejected from the nozzle surface. The temperature drop of the nozzle surface is likely to occur, for example, immediately after ink is ejected from the nozzle surface. That is, when ink is ejected from the nozzle surface, new ink is supplied to the interior of the droplet ejection head, and this new ink may temporarily lower the temperature of the nozzle surface. If ink is ejected in this state with the nozzle surface temperature lowered, the viscosity of the ink changes, causing a change in the ejection state. That is, there is a risk that ink may not be ejected stably from the nozzle surface.

[0011] Therefore, there is a need for a technology that can stabilize the ink ejection state by maintaining the temperature of the nozzle surface at a predetermined temperature.

[0012] (First embodiment) <Printer configuration> First, an overview of a printer 1, which is an example of a recording apparatus according to a first embodiment, will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic side view of the printer 1 according to the first embodiment, and Fig. 2 is a schematic plan view of the printer 1 according to the first embodiment. The printer 1 according to the first embodiment is, for example, a color inkjet printer.

[0013] As shown in FIG. 1, the printer 1 includes a paper feed roller 2, a guide roller 3, an applicator 4, a head case 5, a plurality of conveying rollers 6, a plurality of frames 7, a plurality of droplet ejection heads 8, a conveying roller 9, a dryer 10, a conveying roller 11, a sensor unit 12, and a recovery roller 13.

[0014] Furthermore, the printer 1 has a control unit 14 that controls the paper feed roller 2, guide roller 3, coater 4, head case 5, multiple conveying rollers 6, multiple frames 7, multiple droplet ejection heads 8, conveying roller 9, dryer 10, conveying roller 11, sensor unit 12, and recovery roller 13.

[0015] The printer 1 records images or characters on the printing paper P by causing droplets to land on the printing paper P. The printing paper P is an example of a recording medium. Before use, the printing paper P is wound around a paper feed roller 2. The printer 1 then transports the printing paper P from the paper feed roller 2, via a guide roller 3 and a coater 4, into the interior of a head case 5.

[0016] The coater 4 applies the coating agent evenly to the printing paper P. This allows the printing paper P to be surface treated, thereby improving the printing quality of the printer 1.

[0017] The head case 5 houses a plurality of transport rollers 6, a plurality of frames 7, and a plurality of droplet ejection heads 8. Inside the head case 5, a space is formed that is isolated from the outside, except for a portion that is connected to the outside, such as a portion where the printing paper P enters and leaves.

[0018] At least one of the control factors such as temperature, humidity, and air pressure of the internal space of the head case 5 is controlled by the control unit 14 as necessary. The transport rollers 6 transport the printing paper P inside the head case 5 to the vicinity of the droplet ejection heads 8.

[0019] The frame 7 is a rectangular flat plate, and is positioned above and in close proximity to the print paper P being transported by the transport rollers 6. As shown in Figure 2, the frame 7 is positioned so that its longitudinal direction is perpendicular to the transport direction of the print paper P. Inside the head case 5, multiple (for example, four) frames 7 are positioned along the transport direction of the print paper P.

[0020] In the following description, the transport direction of the printing paper P is also referred to as the "sub-scanning direction," and the direction perpendicular to the sub-scanning direction and parallel to the printing paper P is also referred to as the "main scanning direction."

[0021] Ink is supplied from an ink tank (not shown) to the droplet discharge head 8. The droplet discharge head 8 discharges the ink supplied from the ink tank.

[0022] The control unit 14 controls the droplet ejection head 8 based on data such as images or characters, and ejects droplets toward the printing paper P. The distance between the droplet ejection head 8 and the printing paper P is, for example, about 0.5 to 20 mm.

[0023] The droplet ejection head 8 is fixed to the frame 7. For example, both ends of the droplet ejection head 8 in the longitudinal direction are fixed to the frame 7. The droplet ejection head 8 is positioned so that the longitudinal direction is perpendicular to the transport direction of the printing paper P.

[0024] That is, the printer 1 according to the embodiment is a so-called line printer in which the droplet ejection head 8 is fixed inside the printer 1. Note that the printer 1 according to the embodiment is not limited to a line printer, and may also be a so-called serial printer. A serial printer is a printer that alternates between recording while moving the droplet ejection head 8 back and forth in a direction intersecting the transport direction of the printing paper P, for example, in a direction approximately perpendicular to the direction, and transporting the printing paper P.

[0025] As shown in Fig. 2, a plurality of (for example, five) droplet ejection heads 8 are fixed to one frame 7. Fig. 2 shows an example in which three droplet ejection heads 8 are positioned in front and two in the rear in the transport direction of the printing paper P, and the droplet ejection heads 8 are positioned in the transport direction of the printing paper P so that the centers of the droplet ejection heads 8 do not overlap.

[0026] A head group 8A is made up of multiple droplet ejection heads 8 positioned on one frame 7. The four head groups 8A are positioned along the transport direction of the printing paper P. The same color ink is supplied to droplet ejection heads 8 belonging to the same head group 8A. This allows the printer 1 to print with four colors of ink using the four head groups 8A.

[0027] The colors of ink ejected from each head group 8A are, for example, magenta (M), yellow (Y), cyan (C), and black (K). The control unit 14 controls each head group 8A to eject ink of multiple colors onto the printing paper P, thereby printing a color image on the printing paper P.

[0028] In order to treat the surface of the printing paper P, a coating agent may be ejected onto the printing paper P from the droplet ejection head 8 .

[0029] Furthermore, the number of droplet ejection heads 8 included in one head group 8A, or the number of head groups 8A mounted on the printer 1, can be changed as appropriate depending on the object to be printed or the printing conditions. For example, if a single color is printed on the printing paper P and the printing area is to be printed with one droplet ejection head 8, the number of droplet ejection heads 8 mounted on the printer 1 may be one.

[0030] The printing paper P that has been printed inside the head case 5 is transported to the outside of the head case 5 by transport rollers 9 and passes through the inside of a dryer 10. The dryer 10 dries the printing paper P that has been printed. The printing paper P that has been dried in the dryer 10 is transported by transport rollers 11 and collected by a collection roller 13.

[0031] In the printer 1, by drying the printing paper P in the dryer 10, it is possible to reduce adhesion between overlapping printing paper P wound up on the collection roller 13 and rubbing of undried ink.

[0032] The sensor unit 12 is configured with a position sensor, a speed sensor, a temperature sensor, etc. The control unit 14 can determine the state of each part of the printer 1 based on information from the sensor unit 12 and control each part of the printer 1.

[0033] The printer 1 described so far uses printing paper P as the printing object (i.e., recording medium), but the printing object of the printer 1 is not limited to printing paper P. For example, the printing object may be a roll of cloth or the like.

[0034] Furthermore, the printer 1 may transport the printing paper P on a conveyor belt instead of directly transporting the printing paper P. By using a conveyor belt, the printer 1 can print on sheets of paper, cut pieces of cloth, wood, tiles, etc.

[0035] The printer 1 may also print wiring patterns for electronic devices by discharging droplets containing conductive particles from the droplet discharging head 8. The printer 1 may also produce chemicals by discharging a predetermined amount of liquid chemicals or droplets containing chemicals from the droplet discharging head 8 toward a reaction vessel or the like.

[0036] The printer 1 may also include a cleaning unit that cleans the droplet ejection head 8. The cleaning unit cleans the droplet ejection head 8 by, for example, wiping or capping.

[0037] The wiping process is a process of removing ink adhering to the droplet ejection head 8 by wiping the surface of the area where droplets are ejected with a flexible wiper, for example.

[0038] The capping process is performed, for example, as follows: First, a cap is placed over the surface of the portion onto which droplets are to be ejected (this process is called capping). As a result, a nearly sealed space is formed between the surface onto which droplets are to be ejected and the cap.

[0039] Next, droplets are repeatedly ejected in this sealed space, which makes it possible to remove ink with a viscosity higher than that of the standard state or foreign matter that has clogged the ejection holes (nozzles) that eject droplets.

[0040] <Configuration of droplet ejection head> Next, the configuration of the droplet ejection head 8 according to the first embodiment will be described with reference to Figures 3 and 4. Figure 3 is an exploded perspective view showing the schematic configuration of the droplet ejection head 8 according to the first embodiment. Figure 4 is a cross-sectional view taken along line IV-IV shown in Figure 3.

[0041] The droplet ejection head 8 includes a head main body 20, a wiring section 30, a head cover 40, two heat sinks 45, and two heat insulating members 50. The head main body 20 includes a flow path member 21, a pressing member 22 (see FIG. 4), a branch flow path member 23, a reservoir 24, a heater 71, and a detection section 72.

[0042] In the following description, for convenience, the direction in which the head body 20 is provided in the droplet ejection head 8 may be referred to as "downward," and the direction in which the head cover 40 is provided relative to the head body 20 may be referred to as "upward."

[0043] The flow path member 21 of the head main body 20 has a generally flat plate shape and has a first surface 21a (see FIG. 4) which is one main surface, and a second surface 21b (see FIG. 4) located on the opposite side of the first surface. The first surface 21a has an opening (not shown), and ink is supplied from a reservoir 24 to the inside of the flow path member 21 through this opening.

[0044] The second surface 21b has a plurality of ejection holes (not shown) that eject droplets onto the printing paper P. The second surface 21b is an example of a nozzle surface. The flow path member 21 has a flow path therein that allows ink to flow from the first surface 21a to the second surface 21b.

[0045] The piezoelectric actuator substrate (not shown) is located on the first surface 21a of the flow path member 21. The piezoelectric actuator substrate has a plurality of displacement elements (not shown). The flexible substrate 31 of the wiring section 30 is electrically connected to the piezoelectric actuator substrate.

[0046] The pressing member 22 is positioned above the flow path member 21 and the flexible substrate 31 and presses the flexible substrate 31 against the flow path member 21 .

[0047] The branch flow path member 23 is positioned above the flow path member 21. The branch flow path member 23 has a branch flow path (not shown) inside that connects to the flow path of the flow path member 21. The branch flow path member 23 is made of, for example, metal. The branch flow path member 23 is a box-shaped member that extends long in the main scanning direction (Y-axis direction) and has an open top. The branch flow path member 23 has a bottom 233, a peripheral wall 234 that stands up from the bottom 233, and two slits 235 that sandwich the bottom 233 and through which the flexible substrate 31 is inserted. The bottom 233 is positioned above the pressing member 22. The peripheral wall 234 further has an eave portion 234a that extends outward from the branch flow path member 23. This prevents droplets ejected from the ejection holes of the flow path member 21 from scattering onto the heat sink 45.

[0048] The reservoir 24 is located on the branch flow path member 23. The reservoir 24 has openings 24a at both ends in the main scanning direction (Y-axis direction). The reservoir 24 has an internal flow path, and ink is supplied from the outside through the openings 24a. The reservoir 24 supplies ink to the branch flow path member 23. The reservoir 24 also stores the ink supplied to the branch flow path member 23. The reservoir 24 has a lower cover 24c (see FIG. 4) that covers the lower surface of the reservoir 24.

[0049] When printing, the liquid may be supplied from one opening 24a while the other opening 24a is closed. Alternatively, the liquid may be supplied from both openings 24a. When initially introducing the liquid into the droplet ejection head 8, if the liquid is supplied from one opening 24a and collected from the other opening 24a, air and storage liquid that were in the flow path inside the reservoir 24 can easily escape from the flow path, making it easier to introduce the liquid into the droplet ejection head 8.

[0050] Furthermore, during printing, liquid may be supplied from one opening 24a and recovered from the other opening 24a. In this way, air bubbles are less likely to accumulate in the flow path inside the reservoir 24. Furthermore, by supplying liquid adjusted to a constant temperature, the temperature of the droplet discharge head 8 can be stabilized. The recovered liquid may be passed through a filter or the like and then supplied again to the droplet discharge head 8. In other words, the liquid may be circulated. The supply and recovery of liquid to the droplet discharge head 8, or the circulation of the liquid, may be controlled by the control unit 14.

[0051] Furthermore, liquid may be supplied from the reservoir 24 to the flow path member 21, and liquid may be recovered from the flow path member 21 to the reservoir 24. Furthermore, liquid may be supplied to and recovered from the flow path facing the nozzles (ejection holes) within the flow path member 21, so that liquid is less likely to stagnate within the nozzles and their surroundings. In such an embodiment, liquid is supplied from the outside to the droplet ejection head 8 as a whole, some of the liquid is ejected from the ejection holes, and the liquid that is not ejected is recovered externally.

[0052] The heater 71 is located on the branch flow path member 23 and is provided to bring the ink flowing through the head main body 20 close to a predetermined temperature (target temperature). The heater 71 includes, for example, a heating resistor. The detection unit 72 is located on the pressing member 22 and detects the temperature inside the head main body 20 or the heater 71. The detection unit 72 is, for example, a thermistor. The plate-like member 70 on which the heater 71 and detection unit 72 are located and the surrounding components will be described later.

[0053] The wiring section 30 has a flexible substrate 31, a wiring substrate 32, and a plurality of driver ICs 33. The flexible substrate 31 is a flexible wiring substrate, and transmits a predetermined signal sent from the outside to the head main body 20. As shown in Fig. 3, the droplet ejection head 8 according to the embodiment has two flexible substrates 31.

[0054] One end of the flexible substrate 31 is electrically connected to the piezoelectric actuator substrate of the head body 20. The other end of the flexible substrate 31 is drawn out above the reservoir 24 and is electrically connected to the wiring substrate 32. This allows the piezoelectric actuator substrate of the head body 20 to be electrically connected to the outside.

[0055] The wiring board 32 is located above the head body 20. The wiring board 32 distributes signals to a plurality of driver ICs 33.

[0056] The plurality of driver ICs 33 are located on one main surface of the flexible substrate 31. As shown in Fig. 3, in the droplet ejection head 8 according to the embodiment, two driver ICs 33 are provided on each flexible substrate 31. Note that the number of driver ICs 33 provided on each flexible substrate 31 is not limited to two.

[0057] The driver IC 33 drives each displacement element on the piezoelectric actuator substrate of the head main body 20 based on a drive signal sent from the control unit 14 (see FIG. 1 ). In this way, the driver IC 33 drives the droplet ejection head 8.

[0058] The head cover 40 is attached to the head body 20 and is arranged so as to cover the wiring section 30, such as the flexible substrate 31 and the wiring substrate 32, located on the head body 20. This allows the head cover 40 to seal the wiring section 30. The head cover 40 is made of, for example, resin or metal.

[0059] The head cover 40 has a box shape that extends long in the main scanning direction and has a first opening 40a and a second opening 40b on two side surfaces that face each other in the sub-scanning direction. In the example of Fig. 3, the first opening 40a is provided on the side surface located on the positive side of the X axis, and the second opening 40b is provided on the side surface located on the negative side of the X axis. The head cover 40 also has a third opening 40c on its bottom surface and a fourth opening 40d on its top surface.

[0060] The two heat sinks 45 are attached to the head cover 40. One of the two heat sinks 45 is disposed so as to cover the first opening 40a, and the other is disposed so as to cover the second opening 40b.

[0061] The heat sink 45 is, for example, a plate-shaped member that is long in the longitudinal direction of the droplet ejection head 8, and is made of a metal or alloy with high heat dissipation properties. The heat sink 45 is provided so as to be in contact with the driver IC 33, and dissipates heat generated by the driver IC 33.

[0062] Each of the two heat sinks 45 has a plurality of first through holes 46 that accommodate fixing members. The head cover 40 has a plurality of through holes 41 that accommodate such fixing members. The two heat sinks 45 are each fixed to the head cover 40 by fixing members. The head cover 40 with the heat sinks 45 attached has a box shape in which the first opening 40a and the second opening 40b are closed and the third opening 40c and the fourth opening 40d are open.

[0063] The third opening 40c is positioned to face the reservoir 24. The flexible substrate 31 is inserted into the third opening 40c.

[0064] The fourth opening 40d is provided for inserting a connector (not shown) provided on the wiring board 32. If the space between the connector and the fourth opening 40d is sealed with resin or the like, it becomes difficult for liquid or dust to enter the inside of the head cover 40.

[0065] The heat sink 45 also has second through holes 48a to 48c at the center and both ends in the longitudinal direction of the head body 20. Protrusions 54 of a heat insulating member 50, which will be described later, are housed in the second through holes 48a to 48c.

[0066] The heat insulating member 50 is positioned between the heat sink 45 and the head main body 20. The width of the heat insulating member 50 in the longitudinal direction is wider than the width of the heat sink 45 in the longitudinal direction. The heat insulating member 50 is made of, for example, resin. The thermal conductivity of the heat insulating member 50 may be lower than the thermal conductivity of the heat sink 45. By providing the heat insulating member 50, heat generated in the driver IC 33 is less likely to be transmitted to the head main body 20 via the heat sink 45. Details of the heat insulating member 50 will be described later.

[0067] 3 shows an example of the configuration of the droplet ejection head 8, and the droplet ejection head 8 may further include members other than those shown in FIG.

[0068] 4, the detection unit 72 according to the embodiment is located closer to the second surface 21b (nozzle surface) than the heater 71. This allows the temperature in the vicinity of the second surface 21b to be detected, enabling accurate detection of temperature changes in ink before and after ejection. The heater 71 can then quickly adjust the temperature of the ejection holes (not shown) located on the second surface 21b and the ink located in their vicinity to a predetermined temperature, stabilizing the ink ejection state.

[0069] <Configuration of Plate-Shaped Member> Next, the configuration of the plate-shaped member 70 on which the heater 71 and the detector 72 according to the first embodiment are mounted will be further described with reference to Fig. 5. Fig. 5 is a perspective view showing the configuration of the plate-shaped member according to the first embodiment.

[0070] 5 is a flexible thin plate-like member. For example, the plate-like member 70 may be a flexible substrate.

[0071] The plate-shaped member 70 has a first region R1 in which the heater 71 is located, a second region R2 in which the detector 72 is located, and a connection portion 73 connecting the first region R1 and the second region R2. The first region R1, the second region R2, and the connection portion 73 are part of a single flexible substrate. That is, the first region R1, the second region R2, and the connection portion 73 are configured from a single member. In the first embodiment, the plate-shaped member 70 has two second regions R2, and one detector 72 is located in each second region R2 (first detector 72a and second detector 72b, which will be described later).

[0072] 5, the plate-like member 70 has a first region R1 and a second region R2 that are unequal in level. Specifically, the second region R2 is positioned more offset in the negative Z-axis direction than the first region R1. As a result, the second region R2 is positioned closer to the second surface 21b than the first region R1. That is, the detector 72 located in the second region R2 is positioned closer to the second surface 21b than the heater 71 located in the first region R1.

[0073] The heater 71 is, for example, a film heater. The heater 71 includes a first heat generating portion 71a and a second heat generating portion 71b. The first heat generating portion 71a is provided at a position corresponding to one end of the droplet ejection head 8 in the longitudinal direction. The second heat generating portion 71b is provided at a position corresponding to the other end of the droplet ejection head 8 in the longitudinal direction.

[0074] The position corresponding to one longitudinal end of the droplet ejection head 8 specifically refers to the region on one longitudinal end side of the first region R1. Similarly, the position corresponding to the other longitudinal end of the droplet ejection head 8 specifically refers to the region on the other longitudinal end side of the first region R1. The region on one longitudinal end side of the first region R1 may be, for example, the region located closest to one longitudinal end side of the first region R1 when the first region R1 is divided into four equal parts in the longitudinal direction. Similarly, the region on the other longitudinal end side of the first region R1 may be, for example, the region located closest to the other longitudinal end side of the first region R1 when the first region R1 is divided into four equal parts in the longitudinal direction.

[0075] In a droplet ejection head, the temperature at both ends in the longitudinal direction tends to be lower than that at the center of the droplet ejection head in the longitudinal direction. In contrast, in the droplet ejection head 8 according to this embodiment, by providing heaters 71 at both ends in the longitudinal direction of the droplet ejection head 8, it is possible to improve the in-plane temperature uniformity of the nozzle surface compared to, for example, providing heaters 71 over the entire area of ​​the droplet ejection head 8 in the longitudinal direction.

[0076] The first heating element 71a is controlled based on the results of detection by a first detector 72a (described later). The second heating element 71b is controlled based on the results of detection by a second detector 72b (described later). Such control processing will be described later. The heater 71 (first heating element 71a and second heating element 71b) may be located on the plate-like member 70 or inside the plate-like member 70.

[0077] The detection unit 72 includes a first detection unit 72a and a second detection unit 72b. The first detection unit 72a is provided at a position corresponding to one longitudinal end of the droplet ejection head 8. The second detection unit 72b is provided at a position corresponding to the other longitudinal end of the droplet ejection head 8. Specifically, the first detection unit 72a is located in a second region R2 that is closer to the first heat generating unit 71a out of the first and second heat generating units 71a and 71b, and the second detection unit 72b is located in a second region R2 that is closer to the second heat generating unit 71b out of the first and second heat generating units 71a and 71b.

[0078] 5 , the plate-shaped member 70 has a space S between the first region R1 and the second region R2. Specifically, in the plate-shaped member 70 according to the first embodiment, the first region R1 and the second region R2 are connected by two connection portions 73, and the space S is located between these two connection portions 73.

[0079] In this way, by providing the space S in the plate-like member 70, it is possible to reduce the strength of the connection portion 73 compared to when no space S is provided. This makes the connection portion 73 more flexible, which makes it easier to assemble the first region R1 and the second region R2 into the head main body 20 at different levels during the assembly process of the droplet ejection head 8.

[0080] Next, the peripheral members of the plate-shaped member 70 according to the embodiment will be described with reference to Figures 4 to 6. Figure 6 is a cross-sectional view taken along line VI-VI shown in Figure 3.

[0081] A plurality of elastic members 80 are positioned above the heater 71. As shown in Fig. 6, the plurality of elastic members 80 are provided at positions corresponding to the first heat generating portion 71a and the second heat generating portion 71b, respectively. That is, in the first embodiment, the droplet ejection head 8 has two elastic members 80, and each elastic member 80 is provided above the first heat generating portion 71a and the second heat generating portion 71b, respectively.

[0082] The lower cover 24c of the reservoir 24 is positioned on the elastic member 80 and presses the elastic member 80 against the heater 71. The lower cover 24c is an example of a predetermined member positioned inside the head main body 20. Specifically, the lower cover 24c has a protruding portion 241 that protrudes toward the elastic member 80, and the protruding portion 241 presses the elastic member 80 partially against the heater 71. This improves the adhesion between the heater 71 and the elastic member 80. Furthermore, by partially pressing the elastic member 80 against the heater 71, the repulsive force from the elastic member 80 can be minimized. Therefore, deformation of the second surface 21b due to such repulsive force can be reduced.

[0083] Although the example in which the lower cover 24c has the protruding portion 241 protruding toward the elastic member 80 has been described here, the present invention is not limited to this, and the elastic member 80 may have a protruding portion protruding toward the lower cover 24c. In this case as well, the elastic member can be partially pressed against the heater 71 by the contact between the protruding portion and the lower cover 24c.

[0084] The pressing member 22 that presses the flexible substrate 31 against the flow path member 21 is located below the detection unit 72. The pressing member 22 may be made of a metal with a higher thermal conductivity than stainless steel, for example. The thermal conductivity of stainless steel is, for example, 16 to 27 W / m·°C. The pressing member 22 may be made of a metal with a thermal conductivity higher than 27 W / m·°C. Examples of such metals include aluminum and copper. This makes it possible to more uniformly distribute the temperature of the second surface 21b.

[0085] As shown in FIG. 4 , the pressing member 22 and the branch flow path member 23 are electrically connected by a conductive member 85. The conductive member 85 may be, for example, a metal tape. By electrically connecting the pressing member 22 and the branch flow path member 23 in this manner, electric charges accumulated in the pressing member 22 can be released to the outside via the conductive member 85 and the branch flow path member 23. This reduces the risk of electric charges accumulated in the pressing member 22 moving to the detection unit 72 and damaging the detection unit 72. Furthermore, using a metal tape as the conductive member 85 reduces production costs and allows the pressing member 22 and the branch flow path member 23 to be connected without taking up space within the droplet discharge head.

[0086] Next, the control process of the heater 71 according to the first embodiment will be described.

[0087] The droplet ejection head 8 according to the first embodiment may further include a memory unit (not shown). For example, the memory unit may store a target temperature common to the first and second heating elements 71 a and 71 b, a first voltage to be input to the first heating element 71 a, and a second voltage, different from the first voltage, to be input to the second heating element 71 b. In this case, the control unit 14 inputs the first voltage to the first heating element 71 a to bring the temperature detected by the first detection unit closer to the target temperature.

[0088] For example, when the temperature detected by the first detector 72a falls below a threshold, the controller 14 inputs a first voltage to the first heater 71a to cause the first heater 71a to generate heat. Then, when the temperature detected by the first detector 72a reaches a target temperature, the controller 14 stops the input of the first voltage to the first heater 71a, thereby causing the first heater 71a to stop generating heat.

[0089] Furthermore, the control unit 14 inputs a second voltage to the second heating unit 71b to bring the temperature detected by the second detection unit 72b closer to the target temperature. For example, when the temperature detected by the second detection unit 72b falls below a threshold, the control unit 14 inputs the second voltage to the second heating unit 71b to cause the second heating unit 71b to generate heat. Then, when the temperature detected by the second detection unit 72b reaches the target temperature, the control unit 14 stops inputting the second voltage to the second heating unit 71b to stop the second heating unit 71b from generating heat.

[0090] The first and second voltages are determined taking into consideration individual differences between the first and second heat generating portions 71 a and 71 b. For example, the first and second voltages may be determined based on the difference between the temperatures detected by the first and second detectors 72 a and 72 b when the same voltage is input to the first and second heat generating portions 71 a and 71 b.

[0091] Specifically, the control unit 14 sets a predetermined temperature as the target temperature, and then inputs the same voltage to the first heating unit 71a and the second heating unit 71b so that the temperatures detected by the first detector 72a and the second detector 72b approach the set target temperature. The control unit 14 then adjusts the input voltages to the first heating unit 71a and the second heating unit 71b so that the difference between the temperatures detected by the first detector 72a and the second detector 72b becomes zero, in other words, so that the target temperature is detected by both the first detector 72a and the second detector 72b. The final input voltages are then determined as the first voltage and the second voltage.

[0092] The control unit 14 may perform the above-described input voltage determination process multiple times to obtain the average values ​​of the first voltage and the second voltage, and the first voltage and the second voltage obtained in this manner are stored in the storage unit as the first voltage and the second voltage for the set target temperature.

[0093] Furthermore, the control unit 14 may generate information associating the first voltage and the second voltage for each target temperature by changing the target temperature and repeatedly performing the input voltage determination process as described above. Note that the storage unit may store a ratio of the second voltage to the first voltage instead of the value of the second voltage itself. Similarly, the storage unit may store a ratio of the first voltage to the second voltage instead of the value of the first voltage itself.

[0094] As described above, the detection unit 72 according to the first embodiment is located closer to the second surface 21b than the heater 71. This allows the temperature in the vicinity of the second surface 21b to be detected, and the temperature change of the ink before and after ejection to be accurately detected. The heater 71 can then quickly adjust the temperature of the ejection holes (not shown) located on the second surface 21b and the ink located in their vicinity to a predetermined temperature, thereby stabilizing the ejection state of the ink.

[0095] Second Embodiment Fig. 7 is a perspective view showing the configuration of a plate-like member 70a according to a second embodiment. Fig. 8 is a cross-sectional view of a droplet ejection head 8 according to the second embodiment. In the first embodiment, an example in which the first region R1 and the second region R2 are connected by a plurality of connecting portions 73 has been described, but this is not limiting, and the number of connecting portions 73 may be one, as shown in Figs. 7 and 8.

[0096] In the plate-like member 70a according to the second embodiment, the second region R2 extends along the longitudinal direction of the droplet ejection head 8. A detection unit 72 is provided on one end side of the second region R2, and a connection unit 73a that connects the first region R1 and the second region is provided on the other end side. Specifically, one end of the second region R2 is located closer to one longitudinal end of the first region R1 than the longitudinal center of the first region R1, and the other end of the second region R2 is located closer to the longitudinal end of the first region R1 than the longitudinal center of the first region R1.

[0097] For example, in the example shown in Figure 7, one end of the second region R2 in which the first detection unit 72a is located is located closer to one longitudinal end of the first region R1 (positive Y-axis side) than the longitudinal center of the first region R1, and the other end of the second region R2 is located closer to the other longitudinal end of the first region R1 (negative Y-axis side) than the longitudinal center of the first region R1.

[0098] Similarly, in this case, the second region R2 is located closer to the second surface 21b than the first region R1, and as described above, the detection unit 72 is located closer to the second surface 21b than the heater 71. Furthermore, by increasing the distance from one end to the other end of the second region R2, the step between the first region R1 and the second region R2 can be made gentler, which improves ease of assembly and makes it less likely for the second region R2 to peel off.

[0099] Third Embodiment In the first embodiment, an example in which the heater 71 and the detector 72 are located on a single plate-like member 70 has been described, but the heater 71 and the detector 72 may be located on separate members. Fig. 9 is a plan view of a first substrate 74 and a second substrate 75 according to a third embodiment.

[0100] The head main body 20 may have a first substrate 74 on which the heater 71 is located and a second substrate 75 on which the detection unit 72 is located. The first substrate 74 may be, for example, a glass epoxy substrate. The second substrate 75 may be, for example, a flexible substrate or a metal plate. The thickness of the first substrate 74 as a glass epoxy substrate may be greater than the thickness of the second substrate 75 as a flexible substrate or a metal plate.

[0101] The first substrate 74 and the second substrate 75 may be connected via a cable harness 76. By integrating the first substrate 74 and the second substrate 75, it is possible to simplify the work of assembling the first substrate 74 and the second substrate 75 inside the head main body 20 in the process of assembling the droplet ejection head 8. By positioning the second substrate 75 closer to the second surface 21b than the first substrate 74, as described above, the detection unit 72 is configured to be positioned closer to the second surface 21b than the heater 71.

[0102] Other Embodiments In the above-described embodiments, examples have been described in which one detector is provided for one heat generating element, but the droplet ejection head 8 may be configured to have one detector for multiple heat generating elements. For example, the droplet ejection head 8 may be configured to have only one of the two detectors 72 (first detector 72a and second detector 72b) shown in Figure 5. In this case, it is sufficient that the plate-like member 70 has at least one second region R2.

[0103] In one embodiment, (1) a droplet ejection head (for example, droplet ejection head 8) has a flow path member (for example, flow path member 21), a heater (for example, heater 71), and a detection unit (for example, detection unit 72). The flow path member has a nozzle surface (for example, second surface 21b) in which a plurality of ejection holes are opened. The heater is located inside a head main body (for example, head main body 20) that is configured to include the flow path member. The detection unit is located inside the head main body and detects the temperature inside the head main body. The detection unit is located closer to the nozzle surface than the heater.

[0104] (2) The droplet ejection head described in (1) above may further include a plate-like member (for example, plate-like member 70) having a first region (for example, first region R1) where the heater is located and a second region (for example, second region R2) where the detection unit is located, and the second region may be located closer to the nozzle surface than the first region.

[0105] (3) In the droplet ejection head described in (2) above, the plate-like member may be a flexible substrate.

[0106] (4) In the droplet ejection head described in (3) above, the plate-like member has at least one connection portion (for example, connection portion 73) connecting the first region and the second region, and there may be a space (for example, space S) between the first region and the second region.

[0107] (5) The droplet ejection head described in any one of (1) to (4) above has a first substrate on which the heater is located and a second substrate on which the detection unit is located, the first substrate and the second substrate being connected via a cable harness, and the second substrate may be located closer to the nozzle surface than the first substrate.

[0108] (6) The droplet ejection head described in any one of (1) to (5) above may have a pressure chamber connected to the ejection hole, and a supply manifold connected to the pressure chamber and supplying liquid to the pressure chamber, and the heater may be located upstream of the supply manifold.

[0109] (7) In the droplet ejection head described in (6) above, the head body is configured to include a branch flow path member located above the flow path member and having a branch flow path connected to the flow path member, and the heater may be in contact with the branch flow path member.

[0110] (8) The droplet ejection head described in (7) above has an elastic member (for example, elastic member 80) located on the heater, and the elastic member may be pressed against the heater by a predetermined member (for example, lower cover 24c) located inside the head body.

[0111] (9) In the droplet ejection head described in (8) above, one of the elastic member and the specified member may have a protrusion (for example, protrusion 241) that protrudes toward the other of the elastic member and the specified member.

[0112] (10) The droplet ejection head described in any one of (1) to (9) above has a piezoelectric actuator substrate located on a flow path member, a flexible substrate (for example, flexible substrate 31) located on the piezoelectric actuator substrate and electrically connected to the piezoelectric actuator substrate, and a pressing member (for example, pressing member 22) located on the flexible substrate and pressing the flexible substrate against the flow path member, and the detection unit may be located on the pressing member.

[0113] (11) In the droplet ejection head described in (10) above, the pressing member may be made of a metal having a higher thermal conductivity than stainless steel.

[0114] (12) The droplet ejection head described in (11) above may have a conductive member (for example, the conductive member 85) that electrically connects the pressing member and the branch flow path member.

[0115] (13) In the droplet ejection head described in (12) above, the conductive member may be a metal tape.

[0116] (14) In the droplet ejection head described in any one of (1) to (13) above, the detection unit may include a first detection unit (for example, first detection unit 72a) provided at a position corresponding to one end of the droplet ejection head in the longitudinal direction, and a second detection unit (for example, second detection unit 72b) provided at a position corresponding to the other end of the droplet ejection head in the longitudinal direction.

[0117] (15) In the droplet ejection head described in (14) above, the heater may include a first heating element (for example, first heating element 71a) provided at a position corresponding to one end of the droplet ejection head in the longitudinal direction, and a second heating element (for example, second heating element 71b) provided at a position corresponding to the other end of the droplet ejection head in the longitudinal direction.

[0118] (16) In the droplet ejection head described in (15) above, the first heat generating section may be controlled based on the result detected by the first detection section, and the second heat generating section may be controlled based on the temperature detected by the second detection section.

[0119] (17) The droplet ejection head described in (16) above has a control unit (for example, control unit 14) that controls the first heating unit and the second heating unit, and a memory unit that stores a target temperature common to the first heating unit and the second heating unit, a first voltage to be input to the first heating unit, and a second voltage of a value different from the first voltage to be input to the second heating unit, and the control unit may input the first voltage to the first heating unit to bring the temperature detected by the first detection unit closer to the target temperature, and input the second voltage to the second heating unit to bring the temperature detected by the second detection unit closer to the target temperature.

[0120] (18) In the droplet ejection head described in (17) above, the first voltage and the second voltage may be determined based on the difference in temperature detected by the first detection unit and the second detection unit when the same voltage value is input to the first heating element and the second heating element.

[0121] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0122] REFERENCE SIGNS LIST 1 printer 6 transport roller 7 frame 8 droplet ejection head 20 head body 21 flow path member 22 pressing member 23 branch flow path member 24 reservoir 24c lower cover 30 wiring section 40 head cover 45 heat sink 50 heat insulating member 70 plate-shaped member 71 heater 72 detection section

Claims

1. A droplet ejection head comprising: a flow path member having a nozzle surface with a plurality of ejection holes opening therein; a heater located inside a head body comprising the flow path member; and a detection unit located inside the head body for detecting the temperature inside the head body, the detection unit being located closer to the nozzle surface than the heater.

2. A droplet ejection head as described in claim 1, further comprising a plate-like member having a first region where the heater is located and a second region where the detection unit is located, the second region being located closer to the nozzle face than the first region.

3. The droplet ejection head according to claim 2, wherein the plate-like member is a flexible substrate.

4. A droplet ejection head as described in claim 3, wherein the plate-like member has at least one connection portion connecting the first region and the second region, and has a space between the first region and the second region.

5. A droplet ejection head as described in any one of claims 1 to 4, comprising a first substrate on which the heater is located, and a second substrate on which the detection unit is located, the first substrate and the second substrate being connected via a cable harness, and the second substrate being located closer to the nozzle surface than the first substrate.

6. A droplet ejection head as described in any one of claims 1 to 5, comprising: a pressure chamber connected to the ejection hole; and a supply manifold connected to the pressure chamber and supplying liquid to the pressure chamber, wherein the heater is positioned upstream of the supply manifold.

7. A droplet ejection head as described in claim 6, wherein the head body is configured to include a branch flow path member located above the flow path member and having a branch flow path connected to the flow path member, and the heater is in contact with the branch flow path member.

8. The droplet ejection head according to claim 7, further comprising an elastic member located on said heater, said elastic member being pressed against said heater by a predetermined member located inside said head body.

9. The droplet ejection head according to claim 8, wherein one of the elastic member and the specified member has a protruding portion that protrudes toward the other of the elastic member and the specified member.

10. A droplet ejection head as described in any one of claims 1 to 9, comprising: a piezoelectric actuator substrate located on said flow path member; a flexible substrate located on said piezoelectric actuator substrate and electrically connected to said piezoelectric actuator substrate; and a pressing member located on said flexible substrate and pressing said flexible substrate against said flow path member, wherein said detection unit is located on said pressing member.

11. The droplet ejection head according to claim 10, wherein the pressing member is made of a metal having a higher thermal conductivity than stainless steel.

12. A droplet ejection head as described in claim 11, wherein the head body is configured to include a branch flow path member located above the flow path member and having a branch flow path connected to the flow path member, and has a conductive member that electrically connects the pressing member and the branch flow path member.

13. The droplet ejection head according to claim 12, wherein the conductive member is a metal tape.

14. A droplet ejection head described in any one of claims 1 to 13, wherein the detection unit includes a first detection unit provided at a position corresponding to one longitudinal end of the droplet ejection head, and a second detection unit provided at a position corresponding to the other longitudinal end of the droplet ejection head.

15. A droplet ejection head as described in claim 14, wherein the heater includes a first heating portion provided at a position corresponding to one end of the droplet ejection head in the longitudinal direction, and a second heating portion provided at a position corresponding to the other end of the droplet ejection head in the longitudinal direction.

16. A droplet ejection head as described in claim 15, wherein the first heating section is controlled based on the result detected by the first detection section, and the second heating section is controlled based on the temperature detected by the second detection section.

17. A droplet ejection head as described in claim 16, comprising: a control unit that controls the first heating unit and the second heating unit; and a memory unit that stores a target temperature common to the first heating unit and the second heating unit, a first voltage to be input to the first heating unit, and a second voltage of a value different from the first voltage to be input to the second heating unit, wherein the control unit brings the temperature detected by the first detection unit closer to the target temperature by inputting the first voltage to the first heating unit, and brings the temperature detected by the second detection unit closer to the target temperature by inputting the second voltage to the second heating unit.

18. A droplet ejection head as described in claim 17, wherein the first voltage and the second voltage are determined based on the difference in temperature detected by the first detection unit and the second detection unit, respectively, when the same voltage value is input to the first heating unit and the second heating unit.

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