Droplet ejection head

Abstract

A liquid droplet discharge head of the present disclosure includes a channel member, a heater, and a detector. The channel member has a nozzle surface on which a plurality of discharge holes are opened. The heater is positioned inside a head body configured to include the channel member. The detector is positioned inside the head body and detects a temperature inside the head body. The detector is positioned closer to the nozzle surface than the heater is.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a liquid droplet discharge head.BACKGROUND OF INVENTION

[0002] In the related art, as a printing head, for example, a liquid droplet discharge head is known that performs various types of printing by discharging liquid droplets onto a recording medium. Patent Document 1 discloses a printing apparatus including a plurality of heaters for heating a printing head and a heater driver for independently driving the plurality of heaters.CITATION LISTPATENT LITERATURE

[0003] Patent Document 1: JP H6-115074 ASUMMARY

[0004] A liquid droplet discharge head according to an aspect of the present disclosure includes a channel member, a heater, and a detector. The channel member has a nozzle surface on which a plurality of discharge holes are opened. The heater is positioned inside a head body configured to include the channel member. The detector is positioned inside the head body and detects a temperature inside the head body. In addition, the detector is positioned closer to the nozzle surface than the heater is.BRIEF DESCRIPTION OF THE DRAWINGS

[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 illustrating an overall configuration of a liquid droplet discharge head according to the first embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV illustrated in FIG. 3. FIG. 5 is a perspective view illustrating a configuration of a plate-like member according to the first embodiment. FIG. 6 is a cross-sectional view taken along line VI-VI illustrated in FIG. 3. FIG. 7 is a perspective view illustrating a configuration of a plate-like member according to a second embodiment. FIG. 8 is a cross-sectional view of a liquid droplet discharge 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. DESCRIPTION OF EMBODIMENTS

[0006] Modes (hereinafter will be referred to as "embodiments") for implementing a liquid droplet discharge head according to the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the present disclosure is not limited by the embodiments. In addition, the respective embodiments can be appropriately combined within a range so as not to contradict each other in terms of processing content. Additionally, in the following embodiments, the same portions are denoted by the same reference signs, and redundant descriptions are omitted.

[0007] In addition, in the following embodiments, expressions such as "certain", "orthogonal", "perpendicular", and "parallel" may be used, but these expressions need not mean exactly "certain", "orthogonal", "perpendicular", and "parallel". In other words, each of the expressions described above allows for deviations in, for example, manufacturing accuracy, or installation accuracy.

[0008] In addition, in the drawings referenced below, to facilitate understanding, an orthogonal coordinate system may be defined, in which the X-axis direction, Y-axis direction, and Z-axis direction mutually orthogonal are specified, and the Z axis positive direction is set as the vertically upward direction. In some cases, the rotational direction about the vertical axis may be referred to as the θ direction.

[0009] It is known that when the temperature inside a liquid droplet discharge head or the temperature of ink flowing inside the liquid droplet discharge head is kept constant, the viscosity of the ink can be kept constant, and the discharge state of the ink can be stabilized. Therefore, a heater and a temperature sensor are provided inside the liquid droplet discharge head to adjust the temperature of the ink.

[0010] Here, in order to stabilize the discharge state of the ink, it is preferable to keep the temperature of the ink immediately before being discharged from the nozzle surface constant. However, when the temperature sensor is positioned at a location relatively distant from the nozzle surface, the temperature sensor may fail to detect a temperature decrease of the nozzle surface, or, even if detection is possible, the detection is delayed. As a result, there is a risk of being unable to appropriately adjust the temperature of the ink immediately before being discharged from the nozzle surface. Note that the temperature decrease of the nozzle surface is likely to occur, for example, immediately after ink is discharged from the nozzle surface. That is, when ink is discharged from the nozzle surface, new ink is supplied to the inside of the liquid droplet discharge head, and there is a risk that the temperature of the nozzle surface temporarily decreases due to the newly supplied ink. When ink is discharged in a state in which the temperature of the nozzle surface is decreased in this manner, the viscosity of the ink changes, and the discharge state consequently changes. That is, there is a risk that the ink may not be stably discharged from the nozzle surface.

[0011] Therefore, a technology for stabilizing the discharge state of ink by maintaining the temperature of the nozzle surface at a predetermined temperature is expected.First EmbodimentConfiguration of Printer

[0012] First, an outline of a printer 1, which is an example of a recording device according to a first embodiment, will be described with reference to FIGs. 1 and 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 illustrated in FIG. 1, the printer 1 includes a paper feed roller 2, guide rollers 3, an applicator 4, a head case 5, a plurality of transport rollers 6, a plurality of frames 7, a plurality of liquid droplet discharge heads 8, transport rollers 9, a dryer 10, transport rollers 11, a sensor unit 12, and a collection roller 13.

[0014] The printer 1 further includes a controller 14 that controls the paper feed roller 2, the guide rollers 3, the applicator 4, the head case 5, the plurality of transport rollers 6, the plurality of frames 7, the plurality of liquid droplet discharge heads 8, the transport rollers 9, the dryer 10, the transport rollers 11, the sensor unit 12, and the collection roller 13.

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

[0016] The applicator 4 uniformly applies a coating agent to the printing paper P. This can apply surface treatment to the printing paper P, so that the printing quality of the printer 1 can be improved.

[0017] The head case 5 accommodates the plurality of transport rollers 6, the plurality of frames 7, and the plurality of liquid droplet discharge heads 8. The inside of the head case 5 forms a space isolated from the outside except for a portion connected to the outside, such as a portion where the printing paper P enters and leaves.

[0018] In the internal space of the head case 5, at least one of controlling factors such as temperature, humidity, and air pressure is controlled by the controller 14 as required. The transport rollers 6 transport the printing paper P to the vicinity of the liquid droplet discharge heads 8 inside the head case 5.

[0019] The frames 7 are rectangular flat plates and positioned above and in close proximity to the printing paper P transported by the transport rollers 6. In addition, as illustrated in FIG. 2, the frame 7 is positioned such that the longitudinal direction thereof is orthogonal to a transport direction of the printing paper P. The plurality (e.g., four) of frames 7 are positioned inside the head case 5 along the transport direction of the printing paper P.

[0020] Note that, in the following description, a direction in which the printing paper P is transported is also referred to as a "sub-scanning direction," and a direction orthogonal to the sub-scanning direction and parallel to the printing paper P is also referred to as a "main scanning direction".

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

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

[0023] The liquid droplet discharge head 8 is fixed to the frame 7. The liquid droplet discharge head 8 is fixed to the frame 7 at both end portions in the longitudinal direction, for example. The liquid droplet discharge head 8 is positioned such that the longitudinal direction thereof is orthogonal 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 liquid droplet discharge heads 8 are fixed inside the printer 1. Note that the printer 1 according to the embodiment is not limited to the line printer, but may be a so-called serial printer. The serial printer is a printer that employs a method of alternately performing an operation of recording while moving the liquid droplet discharge heads 8 in a direction intersecting the transport direction of the printing paper P, for example, by reciprocating the liquid droplet discharge heads 8 in a direction substantially orthogonal to the transport direction, and an operation of transporting the printing paper P.

[0025] As illustrated in FIG. 2, the plurality of (e.g., five) liquid droplet discharge heads 8 are fixed on one frame 7. FIG. 2 illustrates an example in which three of the liquid droplet discharge heads 8 are positioned on the front side and two of the liquid droplet discharge heads 8 are positioned on the rear side in the transport direction of the printing paper P. The liquid droplet discharge heads 8 are positioned such that the centers thereof do not overlap each other in the transport direction of the printing paper P.

[0026] The plurality of liquid droplet discharge heads 8 positioned on one frame 7 constitute a head group 8A. The four head groups 8A are positioned along the transport direction of the printing paper P. The same color ink is supplied to the liquid droplet discharge heads 8 belonging to the same head group 8A. Accordingly, the printer 1 can perform printing with inks of four colors by using the four head groups 8A.

[0027] The colors of inks discharged from the respective head groups 8A are, for example, magenta (M), yellow (Y), cyan (C), and black (K). The controller 14 can print a color image on the printing paper P by controlling the respective head groups 8A to discharge inks of a plurality of colors onto the printing paper P.

[0028] Note that, in order to treat the surface of the printing paper P, the liquid droplet discharge heads 8 may discharge the coating agent onto the printing paper P.

[0029] The number of the liquid droplet discharge heads 8 included in one head group 8A or the number of the head groups 8A mounted on the printer 1 can be changed as appropriate in accordance with a printing target or printing conditions. For example, when the color to be printed on the printing paper P is a single color and the printing range can be covered by one liquid droplet discharge head 8, the number of liquid droplet discharge 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 the transport rollers 9, and passes through the inside of the dryer 10. The dryer 10 dries the printing paper P that has been printed. The printing paper P dried by the dryer 10 is transported by the transport rollers 11 and collected by the collection roller 13.

[0031] In the printer 1, drying the printing paper P with the dryer 10 can reduce both adhesion between sheets of the printing paper P wound in an overlapping manner and rubbing of undried ink on the collection roller 13.

[0032] The sensor unit 12 is constituted by, for example, a position sensor, a speed sensor, or a temperature sensor. Based on information from the sensor unit 12, the controller 14 can determine the state of each unit of the printer 1 and control each unit of the printer 1.

[0033] The printer 1 described above uses the printing paper P as the printing target (i.e., the recording medium). However, the printing target in the printer 1 is not limited to the printing paper P. For example, the printing target may be a rolled cloth or the like.

[0034] Instead of directly transporting the printing paper P itself, the printer 1 may transport the printing paper P placed on a transport belt. By using the transport belt, the printer 1 can use a sheet of paper, a cut cloth, wood, a tile, or the like as the printing target.

[0035] In addition, the printer 1 may print a wiring pattern or the like of an electronic device by discharging liquid droplets containing electrically conductive particles from the liquid droplet discharge heads 8. The printer 1 may also discharge a predetermined amount of a liquid chemical agent or liquid droplets containing the chemical agent from the liquid droplet discharge heads 8 toward a reaction container or the like to produce chemicals.

[0036] In addition, the printer 1 may also include a cleaning unit that cleans the liquid droplet discharge heads 8. The cleaning unit cleans the liquid droplet discharge heads 8 by performing, for example, a wiping process or a capping process.

[0037] The wiping process is a process for removing ink adhering to the liquid droplet discharge head 8 by wiping a surface of a portion onto which the liquid droplets are discharged, for example, using a flexible wiper.

[0038] The capping process is performed, for example, as follows. First, a cap is placed over the surface of the portion onto which the liquid droplets are discharged (this is called capping). This creates a substantially hermetically sealed space between the cap and the surface of the portion onto which the liquid droplets are discharged.

[0039] Subsequently, the discharge of the liquid droplets is repeated in the hermetically sealed space. As a result, ink having a viscosity higher than that of the ink in a normal state, foreign matter, or the like stuck in discharge holes (nozzles) for discharging the liquid droplets can be removed.Configuration of Liquid Droplet Discharge Head

[0040] Next, a configuration of the liquid droplet discharge head 8 according to the first embodiment will be described with reference to FIGs. 3 and 4. FIG. 3 is an exploded perspective view illustrating an overall configuration of the liquid droplet discharge head 8 according to the first embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV illustrated in FIG. 3.

[0041] The liquid droplet discharge head 8 includes a head body 20, a wiring portion 30, a head cover 40, two heat dissipation plates 45, and two thermal insulating members 50. The head body 20 includes a channel member 21, a pressing member 22 (see FIG. 4), a branched channel member 23, a reservoir 24, a heater 71, and a detector 72.

[0042] In the following description, for convenience, a direction in which the head body 20 is provided in the liquid droplet discharge head 8 may be referred to as "lower", and a direction in which the head cover 40 is provided with respect to the head body 20 may be referred to as "upper".

[0043] The channel member 21 of the head body 20 has a substantially flat plate shape with a first surface 21a (see FIG. 4) as one main surface, and a second surface 21b (see FIG. 4) positioned on an opposite side to the first surface. The first surface 21a includes an opening (not illustrated), and ink is supplied from the reservoir 24 to the inside of the channel member 21 through the opening.

[0044] A plurality of discharge holes (not illustrated) that discharge liquid droplets onto the printing sheet P are opened on the second surface 21b. The second surface 21b is an example of a nozzle surface. The channel member 21 internally includes a channel through which ink flows from the first surface 21a to the second surface 21b.

[0045] A piezoelectric actuator substrate (not illustrated) is positioned on the first surface 21a of the channel member 21. The piezoelectric actuator substrate includes a plurality of displacement elements (not illustrated). The piezoelectric actuator substrate is electrically connected to a flexible substrate 31 of the wiring portion 30.

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

[0047] The branched channel member 23 is positioned on the channel member 21. The branched channel member 23 internally includes a branched channel (not illustrated) connected to the channel of the channel member 21. The branched channel member 23 is composed of metal, for example. The branched channel member 23 is a member having a box shape extending long in the main scanning direction (Y-axis direction), with an upper surface opened. The branched channel member 23 includes a bottom portion 233, a peripheral wall portion 234 standing upright from the bottom portion 233, and two slit portions 235 sandwiching the bottom portion 233, through which the flexible substrate 31 is inserted. The bottom portion 233 is positioned above the pressing member 22. The peripheral wall portion 234 further includes an eave portion 234a protruding outward from the branched channel member 23. In this manner, the liquid droplets discharged from the discharge holes of the channel member 21 can be prevented from scattering to the heat dissipation plate 45.

[0048] The reservoir 24 is positioned on the branched channel member 23. The reservoir 24 is provided with openings 24a at both end portions in the main scanning direction (Y-axis direction). The reservoir 24 internally includes a channel, and ink is supplied from the outside through the openings 24a. The reservoir 24 supplies ink to the branched channel member 23. In addition, the reservoir 24 stores ink that is supplied to the branched channel member 23. The reservoir 24 includes a lower lid 24c (see FIG. 4) that covers a lower surface of the reservoir 24.

[0049] Note that, when performing printing, liquid may be supplied from the opening 24a on one side, with the opening 24a on the other side closed. In addition, liquid may be supplied from the openings 24a on both sides. When initially introducing liquid into the liquid droplet discharge head 8, supplying liquid from the opening 24a on one side and collecting liquid from the opening 24a on the other side allows air, stored liquid, and the like inside the channel in the reservoir 24 to be easily removed from the channel, and thus facilitates the introduction of liquid into the liquid droplet discharge head 8.

[0050] In addition, during the printing, liquid may be supplied from the opening 24a on one side and may be collected from the opening 24a on the other side. By doing so, air bubbles can be made less likely to accumulate in the channel inside the reservoir 24. Furthermore, supplying a liquid adjusted to a constant temperature allows the temperature of the liquid droplet discharge head 8 to be stabilized. The collected liquid may be passed through a filter or the like before being supplied to the liquid droplet discharge head 8 once again. In other words, the liquid may be circulated. The controller 14 may control the supply and collection of the liquid to and from the liquid droplet discharge head 8, or may control the circulation of the liquid.

[0051] In addition, the liquid may be supplied from the reservoir 24 to the channel member 21, and may be collected from the channel member 21 to the reservoir 24. In addition, in the channel member 21, the liquid may be supplied to and collected from the channel facing the nozzles (discharge holes) so that the liquid is less likely to stay in the nozzles and the periphery thereof. In such a mode, as a whole, the liquid is supplied to the liquid droplet discharge heads 8 from the outside, part of the liquid is discharged from the discharge holes, and the liquid that has not been discharged is collected to the outside.

[0052] The heater 71 is positioned on the branched channel member 23 and is provided to bring the temperature of ink flowing through the head body 20 close to a predetermined temperature (target temperature). The heater 71 includes, for example, a heat generating resistor. The detector 72 is positioned on the pressing member 22 and detects the temperature of the inside of the head body 20 or the heater 71. The detector 72 is, for example, a thermistor. A plate-like member 70 on which the heater 71 and the detector 72 are positioned and peripheral components thereof will be described below.

[0053] The wiring portion 30 includes the flexible substrate 31, a wiring board 32, and a plurality of driver ICs 33. The flexible substrate 31 is a flexible wiring board, and transmits, to the head body 20, a predetermined signal transmitted from the outside. Note that, as illustrated in FIG. 3, the liquid droplet discharge head 8 according to the embodiment includes two flexible substrates 31.

[0054] The flexible substrate 31 includes one end portion electrically connected to the piezoelectric actuator substrate of the head body 20. The other end portion of the flexible substrate 31 is drawn out above the reservoir 24 and electrically connected to the wiring board 32. In this way, the piezoelectric actuator substrate of the head body 20 can be electrically connected to the outside.

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

[0056] The plurality of driver ICs 33 are positioned on one main surface of the flexible substrate 31. As illustrated in FIG. 3, in the liquid droplet discharge head 8 according to the embodiment, two driver ICs 33 are provided on one flexible substrate 31. Note that the number of driver ICs 33 provided on one flexible substrate 31 is not limited to two.

[0057] The driver IC 33 drives each displacement element in the piezoelectric actuator substrate of the head body 20 based on a driving signal transmitted from the controller 14 (see FIG. 1). In this way, the driver IC 33 drives the liquid droplet discharge head 8.

[0058] The head cover 40 is mounted to the head body 20, and is disposed so as to cover the wiring portion 30 positioned on the head body 20, such as the flexible substrates 31 and the wiring board 32. In this way, the head cover 40 can seal the wiring portion 30. The head cover 40 is made of, for example, a resin or a metal.

[0059] The head cover 40 has a box shape extending long in the main scanning direction and includes a first opening 40a and a second opening 40b on two side surfaces facing each other along the sub-scanning direction, respectively. In the example of FIG. 3, the first opening 40a is provided on the side surface positioned on the X-axis positive direction side, and the second opening 40b is provided on the side surface positioned on the X-axis negative direction side. The head cover 40 also includes a third opening 40c on a lower surface thereof, and a fourth opening 40d on an upper surface thereof.

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

[0061] The heat dissipation plate 45 is a plate-like member that is long in the longitudinal direction of the liquid droplet discharge head 8, and is composed of a metal, an alloy, or the like with high heat dissipation properties, for example. The heat dissipation plates 45 are provided in contact with the corresponding driver ICs 33 to dissipate heat generated in the driver ICs 33.

[0062] Each of the two heat dissipation plates 45 includes a plurality of first through holes 46 that accommodate fixing members. The head cover 40 includes a plurality of through holes 41 that accommodate the fixing members. The two heat dissipation plates 45 are each fixed to the head cover 40 with the fixing members. The head cover 40 on which the heat dissipation plates 45 are mounted 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 so as to face the reservoir 24. The flexible substrates 31 are inserted into the third opening 40c.

[0064] The fourth opening 40d is provided to allow a connector (not illustrated) provided on the wiring board 32 to be inserted therein. When a space between the connector and the fourth opening 40d is sealed with a resin or the like, liquid, dust, or the like is less likely to enter the head cover 40.

[0065] In addition, the heat dissipation plate 45 has second through holes 48a to 48c at a center portion and both end portions in the longitudinal direction of the head body 20. Protruding portions 54 of a thermal insulating member 50 described below are accommodated into the second through holes 48a to 48c.

[0066] The thermal insulating member 50 is positioned between the heat dissipation plate 45 and the head body 20. A width of the thermal insulating member 50 in the longitudinal direction thereof is greater than a width of the heat dissipation plate 45 in the longitudinal direction thereof. The thermal insulating member 50 is composed of, for example, a resin. A thermal conductivity of the thermal insulating member 50 may be lower than that of the heat dissipation plate 45. By providing the thermal insulating members 50, heat generated in the driver ICs 33 is less likely to be transferred to the head body 20 via the heat dissipation plates 45. Details of the thermal insulating member 50 will be described below.

[0067] Note that FIG. 3 illustrates an example of the configuration of the liquid droplet discharge head 8, and members other than those illustrated in FIG. 3 may be further included.

[0068] As illustrated in FIG. 4, the detector 72 according to the embodiment is positioned closer to the second surface 21b (nozzle surface) than the heater 71 is. Accordingly, the temperature in the vicinity of the second surface 21b can be detected, and a temperature change in the ink before and after discharge can be accurately detected. The temperature of the ink in the discharge holes (not illustrated) positioned on the second surface 21b and in the vicinity of the discharge holes can be quickly adjusted to a predetermined temperature by the heater 71, and the discharge state of the ink can be stabilized.Configuration of Plate-Like Member

[0069] Subsequently, the configuration of the plate-like 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 illustrating the configuration of the plate-like member according to the first embodiment.

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

[0071] The plate-like member 70 includes a first region R1 in which the heater 71 is positioned, a second region R2 in which the detector 72 is positioned, and a connecting portion 73 connecting the first region R1 and the second region R2. The first region R1, the second region R2, and the connecting portion 73 are portions of one flexible substrate. That is, the first region R1, the second region R2, and the connecting portion 73 are composed of a single member. In the first embodiment, the plate-like member 70 includes two second regions R2, and one detector 72 is positioned in each of the second regions R2 (a first detector 72a and a second detector 72b described below).

[0072] As illustrated in FIG. 5, the plate-like member 70 has the first region R1 and the second region R2 arranged in a stepped manner. Specifically, the second region R2 is provided at a position shifted from the first region R1 in the Z-axis negative direction. Thereby, the second region R2 is positioned closer to the second surface 21b than the first region R1 is. That is, the detector 72 positioned in the second region R2 is positioned closer to the second surface 21b than the heater 71 positioned in the first region R1 is.

[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 liquid droplet discharge head 8 in the longitudinal direction. The second heat generating portion 71b is provided at a position corresponding to the other end of the liquid droplet discharge head 8 in the longitudinal direction.

[0074] Note that the position corresponding to one end of the liquid droplet discharge head 8 in the longitudinal direction is specifically a region on one end side of the first region R1 in the longitudinal direction. Similarly, the position corresponding to the other end of the liquid droplet discharge head 8 in the longitudinal direction is specifically a region on the other end side of the first region R1 in the longitudinal direction. The region on one end side of the first region R1 in the longitudinal direction may be, for example, a region positioned on the extreme one end side in the longitudinal direction among four regions obtained by equally dividing the first region R1 in the longitudinal direction. Similarly, the region on the other end side of the first region R1 in the longitudinal direction may be, for example, a region positioned on the extreme other end side in the longitudinal direction among four regions obtained by equally dividing the first region R1 in the longitudinal direction.

[0075] In the liquid droplet discharge head, the temperature at both end portions of the liquid droplet discharge head in the longitudinal direction is likely to be lower than that at the center portion in the longitudinal direction. In contrast, in the liquid droplet discharge head 8 according to the embodiment, the heaters 71 are provided at both ends of the liquid droplet discharge head 8 in the longitudinal direction. Therefore, the in-plane uniformity of the temperature of the nozzle surface can be improved as compared with a case where the heater 71 is provided over the entire region of the liquid droplet discharge head 8 in the longitudinal direction, for example.

[0076] The first heat generating portion 71a is controlled based on a result detected by the first detector 72a described below. The second heat generating portion 71b is controlled based on a result detected by the second detector 72b described below. Such a control process will be described below. Note that the heater 71 (the first heat generating portion 71a and the second heat generating portion 71b) may be positioned above the plate-like member 70 or may be positioned inside the plate-like member 70.

[0077] The detector 72 includes the first detector 72a and the second detector 72b. The first detector 72a is provided at a position corresponding to one end of the liquid droplet discharge head 8 in the longitudinal direction. The second detector 72b is provided at a position corresponding to the other end of the liquid droplet discharge head 8 in the longitudinal direction. Specifically, the first detector 72a is positioned in the second region R2 closer to the first heat generating portion 71a of the first heat generating portion 71a and the second heat generating portion 71b, and the second detector 72b is positioned in the second region R2 closer to the second heat generating portion 71b of the first heat generating portion 71a and the second heat generating portion 71b.

[0078] As illustrated in FIG. 5, the plate-like member 70 has a space S between the first region R1 and the second region R2. Specifically, in the plate-like member 70 according to the first embodiment, the first region R1 and the second region R2 are connected to each other by two connecting portions 73, and the space S is positioned between the two connecting portions 73.

[0079] In this manner, by providing the space S in the plate-like member 70, the strength of the connecting portion 73 can be reduced as compared with a case where the space S is not provided. Accordingly, the connecting portion 73 is easily bent, thereby facilitating an operation of incorporating the first region R1 and the second region R2 in a stepped manner inside the head body 20 during an assembly process of the liquid droplet discharge head 8.

[0080] Subsequently, the peripheral members of the plate-like member 70 according to the embodiment will be described with reference to FIGs. 4 to 6. FIG. 6 is a cross-sectional view taken along line VI-VI illustrated in FIG. 3.

[0081] A plurality of elastic members 80 are positioned above the heater 71. As illustrated 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, the liquid droplet discharge head 8 of the first embodiment has two elastic members 80, and the elastic members 80 are provided above the first heat generating portion 71a and the second heat generating portion 71b, respectively.

[0082] The lower lid 24c of the reservoir 24 is positioned on the elastic members 80, and presses the elastic members 80 against the heater 71. The lower lid 24c is an example of a predetermined member positioned inside the head body 20. Specifically, the lower lid 24c has protruding portions 241 protruding toward the elastic members 80, and the elastic members 80 are partially pressed against the heater 71 by the protruding portions 241. This can improve adhesiveness between the heater 71 and the elastic members 80. In addition, by partially pressing the elastic members 80 against the heater 71, the repulsive force from the elastic members 80 can be minimized. As a result, deformation of the second surface 21b caused by the repulsive force can be reduced.

[0083] Note that, although the example in which the lower lid 24c includes the protruding portions 241 protruding toward the elastic members 80 has been described here, no such limitation is intended, and the elastic member 80 may have a protruding portion protruding toward the lower lid 24c. In this case, similarly, the elastic member can be partially pressed against the heater 71 by contact between the protruding portion and the lower lid 24c.

[0084] The pressing member 22 that presses the flexible substrate 31 against the channel member 21 is positioned below the detector 72. The pressing member 22 may be made of a metal having a higher thermal conductivity than that of 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 having a higher thermal conductivity than 27 W / m·°C. Examples of the metal include aluminum and copper. As a result, the temperature variation of the second surface 21b can be made more uniform.

[0085] As illustrated in FIG. 4, the pressing member 22 and the branched channel member 23 are electrically connected to each other by an electrically conductive member 85. The electrically conductive member 85 may be a metal tape, for example. In this manner, by electrically connecting the pressing member 22 and the branched channel member 23, the electric charges accumulated in the pressing member 22 can be released to the outside via the electrically conductive member 85 and the branched channel member 23. This reduces the possibility that the electric charges accumulated in the pressing member 22 move to the detector 72 and damage the detector 72. In addition, by using a metal tape as the electrically conductive member 85, it is possible to reduce the production cost, and to connect the pressing member 22 and the branched channel member 23 without occupying a space inside the liquid droplet discharge head.

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

[0087] The liquid droplet discharge head 8 according to the first embodiment may further include a storage unit (not illustrated). For example, the storage unit may store a target temperature common to the first heat generating portion 71a and the second heat generating portion 71b, a first voltage that is input to the first heat generating portion 71a, and a second voltage that is input to the second heat generating portion 71b and has a value different from that of the first voltage. In this case, the controller 14 inputs the first voltage to the first heat generating portion 71a to bring the temperature detected by the first detector close to the target temperature.

[0088] For example, when the temperature detected by the first detector 72a is below a reference value, the controller 14 inputs the first voltage to the first heat generating portion 71a to cause the first heat generating portion 71a to generate heat. When the temperature detected by the first detector 72a reaches the target temperature, the controller 14 stops the input of the first voltage to the first heat generating portion 71a to stop the heat generation of the first heat generating portion 71a.

[0089] In addition, the controller 14 inputs the second voltage to the second heat generating portion 71b to bring the temperature detected by the second detector 72b close to the target temperature. For example, when the temperature detected by the second detector 72b is below the reference value, the controller 14 inputs the second voltage to the second heat generating portion 71b to cause the second heat generating portion 71b to generate heat. When the temperature detected by the second detector 72b reaches the target temperature, the controller 14 stops the input of the second voltage to the second heat generating portion 71b to stop the heat generation of the second heat generating portion 71b.

[0090] The first voltage and the second voltage are determined in consideration of individual differences between the first heat generating portion 71a and the second heat generating portion 71b. For example, the first voltage and the second voltage may be determined based on a difference between temperatures detected by the first detector 72a and the second detector 72b, respectively, when voltages having the same value are input to the first heat generating portion 71a and the second heat generating portion 71b.

[0091] Specifically, the controller 14 sets a predetermined temperature as the target temperature, and then inputs voltages having the same value to the first heat generating portion 71a and the second heat generating portion 71b so that the temperatures detected by the first detector 72a and the second detector 72b approach the set target temperature. Thereafter, the input voltages to the first heat generating portion 71a and the second heat generating portion 71b are respectively adjusted so that the difference between the temperatures detected by the first detector 72a and the second detector 72b become zero, in other words, so that the target temperature is detected by both the first detector 72a and the second detector 72b. Then, final input voltages are determined as the first voltage and the second voltage.

[0092] The controller 14 may perform the above-described input voltage determination process a plurality of times to obtain an average value of each of the first voltage and the second voltage. 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 with respect to the set target temperature.

[0093] In addition, the controller 14 may generate information in which the first voltage and the second voltage are associated with each target temperature by repeatedly performing the above-described input voltage determination process while changing the target temperature. Note that a multiplication factor of the second voltage with respect to the first voltage may be stored in the storage unit instead of the value of the second voltage itself. Similarly, a multiplication factor of the first voltage with respect to the second voltage may be stored in the storage unit instead of the value of the first voltage itself.

[0094] As described above, the detector 72 according to the first embodiment is positioned closer to the second surface 21b than the heater 71 is. Accordingly, the temperature in the vicinity of the second surface 21b can be detected, and a temperature change in the ink before and after discharge can be accurately detected. The temperature of the ink in the discharge holes (not illustrated) positioned on the second surface 21b and in the vicinity of the discharge holes can be quickly adjusted to a predetermined temperature by the heater 71, and the discharge state of the ink can be stabilized.Second Embodiment

[0095] FIG. 7 is a perspective view illustrating a configuration of a plate-like member 70a according to a second embodiment. FIG. 8 is a cross-sectional view of the liquid droplet discharge head 8 according to the second embodiment. In the first embodiment, the example in which the first region R1 and the second region R2 are connected to each other by the plurality of connecting portions 73 has been described. However, no such limitation is intended, and the number of connecting portions 73 may be one as illustrated 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 liquid droplet discharge head 8. The detector 72 is provided on one end side of the second region R2, and a connecting portion 73a connecting the first region R1 and the second region is provided on the other end side. Specifically, one end of the second region R2 is positioned on one end side of the first region R1 in the longitudinal direction with respect to the center of the first region R1 in the longitudinal direction, and the other end of the second region R2 is positioned on the other end side of the first region R1 in the longitudinal direction with respect to the center of the first region R1 in the longitudinal direction.

[0097] For example, in the example illustrated in FIG. 7, one end of the second region R2 where the first detector 72a is positioned is positioned on one end side (the Y-axis positive direction side) of the first region R1 in the longitudinal direction with respect to the center of the first region R1 in the longitudinal direction, and the other end of the second region R2 is positioned on the other end side (the Y-axis negative direction side) of the first region R1 in the longitudinal direction with respect to the center of the first region R1 in the longitudinal direction.

[0098] In this case, similarly, the second region R2 is positioned closer to the second surface 21b than the first region R1, so that the detector 72 is positioned closer to the second surface 21b than the heater 71 is, as described above. In addition, by increasing a distance from one end to the other end of the second region R2, a step formed between the first region R1 and the second region R2 can be made more gradual, thereby improving the ease of assembly and making the second region R2 less likely to peel off.Third Embodiment

[0099] In the first embodiment, the example in which the heater 71 and the detector 72 are positioned on the single plate-like member 70 has been described, but the heater 71 and the detector 72 may be positioned on different 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 body 20 may include a first substrate 74 on which the heater 71 is positioned and a second substrate 75 on which the detector 72 is positioned. 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. A thickness of the first substrate 74 as a glass epoxy substrate may be greater than that 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 to each other via a cable harness 76. The first substrate 74 and the second substrate 75 are integrated, thereby facilitating an operation of incorporating the first substrate 74 and the second substrate 75 inside the head body 20 during an assembly process of the liquid droplet discharge head 8. The second substrate 75 is positioned closer to the second surface 21b than the first substrate 74, resulting in the configuration in which the detector 72 is positioned closer to the second surface 21b than the heater 71 is, as described above.Other Embodiments

[0102] In the above-described embodiments, the example in which one detector is provided for one heat generating portion has been described, but the liquid droplet discharge head 8 may have a configuration in which one detector is provided for a plurality of heat generating portions. For example, the liquid droplet discharge head 8 may have a configuration including only one of the two detectors 72 (the first detector 72a and the second detector 72b) illustrated in FIG. 5. In this case, the plate-like member 70 may have at least one second region R2.

[0103] In an embodiment, (1) a liquid droplet discharge head (for example, the liquid droplet discharge head 8) includes a channel member (for example, the channel member 21), a heater (for example, the heater 71), and a detector (for example, the detector 72). The channel member has a nozzle surface (for example, the second surface 21b) on which a plurality of discharge holes are opened. The heater is positioned inside a head body (for example, the head body 20) configured to include the channel member. The detector is positioned inside the head body and detects a temperature inside the head body. The detector is positioned closer to the nozzle surface than the heater is.

[0104] (2) The liquid droplet discharge head described in the above (1) may further include a plate-like member (for example, the plate-like member 70) including a first region (for example, the first region R1) in which the heater is positioned and a second region (for example, the second region R2) in which the detector is positioned, and the second region may be positioned closer to the nozzle surface than the first region is.

[0105] (3) In the liquid droplet discharge head described in the above (1), the plate-like member may be a flexible substrate.

[0106] (4) In the liquid droplet discharge head described in the above (3), the plate-like member may include at least one connecting portion (for example, the connecting portion 73) configured to connect the first region and the second region, and a space (for example, the space S) may be present between the first region and the second region.

[0107] (5) The liquid droplet discharge head described in any one of the above (1) to (4) may include a first substrate on which the heater is positioned and a second substrate on which the detector is positioned, the first substrate and the second substrate may be connected to each other via a cable harness, and the second substrate may be positioned closer to the nozzle surface than the first substrate is.

[0108] (6) The liquid droplet discharge head described in any one of the above (1) to (5) may include a pressurizing chamber connected to the discharge holes, and a supply manifold connected to the pressurizing chamber and configured to supply a liquid to the pressurizing chamber, and the heater may be positioned upstream of the supply manifold.

[0109] (7) In the liquid droplet discharge head described in the above (6), the head body may be configured to include a branched channel member positioned above the channel member and including a branched channel connected to the channel member, and the heater may be in contact with the branched channel member.

[0110] (8) The liquid droplet discharge head described in the above (7) may include an elastic member (for example, the elastic member 80) positioned above the heater, and the elastic member may be pressed against the heater by a predetermined member (for example, the lower lid 24c) positioned inside the head body.

[0111] (9) In the liquid droplet discharge head described in the above (8), one of the elastic member and the predetermined member may include a protruding portion (for example, the protruding portion 241) protruding toward the other of the elastic member and the predetermined member.

[0112] (10) The liquid droplet discharge head described in any one of the above (1) to (9) may include a piezoelectric actuator substrate positioned above the channel member, a flexible substrate (for example, the flexible substrate 31) positioned above the piezoelectric actuator substrate and electrically connected to the piezoelectric actuator substrate, and a pressing member (for example, the pressing member 22) positioned above the flexible substrate and configured to press the flexible substrate against the channel member, and the detector may be positioned above the pressing member.

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

[0114] (12) The liquid droplet discharge head described in the above (11) may include an electrically conductive member (for example, the electrically conductive member 85) configured to electrically connect the pressing member and the branched channel member.

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

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

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

[0118] (16) In the liquid droplet discharge head described in the above (15), the first heat generating portion may be controlled based on a result detected by the first detector, and the second heat generating portion may be controlled based on a temperature detected by the second detector.

[0119] (17) The liquid droplet discharge head described in the above (16) may include a controller (for example, the controller 14) configured to control the first heat generating portion and the second heat generating portion, and a storage unit in which a target temperature common to the first heat generating portion and the second heat generating portion, a first voltage to be input to the first heat generating portion, and a second voltage to be input to the second heat generating portion and having a value different from that of the first voltage are stored, the controller may input the first voltage to the first heat generating portion to bring a temperature detected by the first detector close to the target temperature, and input the second voltage to the second heat generating portion to bring a temperature detected by the second detector close to the target temperature.

[0120] (18) In the liquid droplet discharge head described in the above (17), the first voltage and the second voltage may be determined based on a difference between temperatures respectively detected by the first detector and the second detector when voltages having the same value are input to the first heat generating portion and the second heat generating portion.

[0121] Note that the embodiments disclosed herein are exemplary in all respects and not restrictive. Actually, the above-described embodiments can be embodied in a variety of forms. In addition, the above-described embodiments may be omitted, substituted or modified in various forms without departing from the scope and spirit of the appended claims.REFERENCE SIGNS

[0122] 1 Printer 6 Transport roller 7 Frame 8 Liquid droplet discharge head 20 Head body 21 Channel member 22 Pressing member 23 Branched channel member 24 Reservoir 24c Lower lid 30 Wiring portion 40 Head cover 45 Heat dissipation plate 50 Thermal insulating member 70 Plate-like member 71 Heater 72 Detector

Claims

1. A liquid droplet discharge head comprising: a channel member having a nozzle surface on which a plurality of discharge holes are opened; a heater positioned inside a head body configured to comprise the channel member; and a detector positioned inside the head body and configured to detect a temperature inside the head body, wherein the detector is positioned closer to the nozzle surface than the heater is.

2. The liquid droplet discharge head according to claim 1, further comprising a plate-like member comprising a first region in which the heater is positioned and a second region in which the detector is positioned, wherein the second region is positioned closer to the nozzle surface than the first region is.

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

4. The liquid droplet discharge head according to claim 3, wherein the plate-like member comprises at least one connecting portion configured to connect the first region and the second region, and a space provided between the first region and the second region.

5. The liquid droplet discharge head according to any one of claims 1 to 4, comprising: a first substrate on which the heater is positioned, and a second substrate on which the detector is positioned, wherein the first substrate and the second substrate are connected to each other via a cable harness, and the second substrate is positioned closer to the nozzle surface than the first substrate is.

6. The liquid droplet discharge head according to any one of claims 1 to 5, comprising: a pressurizing chamber connected to the discharge holes, and a supply manifold connected to the pressurizing chamber and configured to supply a liquid to the pressurizing chamber, wherein the heater is positioned upstream of the supply manifold.

7. The liquid droplet discharge head according to claim 6, wherein the head body is configured to comprise a branched channel member positioned above the channel member and comprising a branched channel connected to the channel member, and the heater is in contact with the branched channel member.

8. The liquid droplet discharge head according to claim 7, comprising an elastic member positioned above the heater, wherein the elastic member is pressed against the heater by a predetermined member positioned inside the head body.

9. The liquid droplet discharge head according to claim 8, wherein one of the elastic member and the predetermined member comprises a protruding portion protruding toward the other of the elastic member and the predetermined member.

10. The liquid droplet discharge head according to any one of claims 1 to 9, comprising: a piezoelectric actuator substrate positioned above the channel member, a flexible substrate positioned above the piezoelectric actuator substrate and electrically connected to the piezoelectric actuator substrate, and a pressing member positioned above the flexible substrate and configured to press the flexible substrate against the channel member, wherein the detector is positioned above the pressing member.

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

12. The liquid droplet discharge head according to claim 11, wherein the head body is configured to comprise a branched channel member positioned above the channel member and comprising a branched channel connected to the channel member, and a conductive member configured to electrically connect the pressing member and the branched channel member is provided.

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

14. The liquid droplet discharge head according to any one of claims 1 to 13, wherein the detector comprises a first detector provided at a position corresponding to one end of the liquid droplet discharge head in a longitudinal direction, and a second detector provided at a position corresponding to the other end of the liquid droplet discharge head in the longitudinal direction.

15. The liquid droplet discharge head according to claim 14, wherein the heater comprises a first heat generating portion provided at a position corresponding to one end of the liquid droplet discharge head in the longitudinal direction, and a second heat generating portion provided at a position corresponding to the other end of the liquid droplet discharge head in the longitudinal direction.

16. The liquid droplet discharge head according to claim 15, wherein the first heat generating portion is controlled based on a result detected by the first detector, and the second heat generating portion is controlled based on a temperature detected by the second detector.

17. The liquid droplet discharge head according to claim 16, comprising: a controller configured to control the first heat generating portion and the second heat generating portion, and a storage unit in which a target temperature common to the first heat generating portion and the second heat generating portion, a first voltage to be input to the first heat generating portion, and a second voltage to be input to the second heat generating portion and having a value different from that of the first voltage are stored, wherein the controller inputs the first voltage to the first heat generating portion to bring a temperature detected by the first detector close to the target temperature, and inputs the second voltage to the second heat generating portion to bring a temperature detected by the second detector close to the target temperature.

18. The liquid droplet discharge head according to claim 17, wherein the first voltage and the second voltage are determined based on a difference between temperatures respectively detected by the first detector and the second detector when voltages having the same value are input to the first heat generating portion and the second heat generating portion.

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