Inkjet Head and Inkjet Recording Apparatus

Abstract

To provide an ink jet head and an ink jet recording device which can arrange nozzles in the higher density while suppressing reduction in discharge accuracy of ink.SOLUTION: An ink jet head includes a head chip in which a pressure chamber substrate that has a pressure chamber (71) for applying pressure fluctuation to ink inside the ink jet head, a nozzle substrate that has a nozzle (N) for discharging the ink and a channel substrate that has a communication flow channel for making the nozzle (N) communicate to the pressure chamber (71) overlap each other. Regarding the cross-sectional shape vertical to the direction of overlapping of the pressure chamber (71), the first width in the first direction (X) is half or less of the first length in the second direction vertical to the first direction, and the second width in the first direction (X) in at least a portion (722) from the side contacting the nozzle (N) of the communication flow channel (72) is wider than the first width and the first diameter of a connection port being one end contacting the channel substrate of the nozzle (N).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] This invention relates to an inkjet head and an inkjet recording apparatus.

Background Art

[0002] There is an inkjet recording apparatus including an inkjet head that discharges ink from a plurality of nozzles and records an image or the like with the discharged ink. As one shape of the inkjet head, there is a structure in which a plurality of substrates through which ink flow paths penetrate are stacked, and ink is discharged from the openings of nozzles on a nozzle substrate located at the lowermost layer. From the viewpoints of increasing the nozzle array density and the stability of ink discharge characteristics, the nozzle diameter is smaller than the size of the ink flow path, and in a cross section perpendicular to the stacking direction of the ink flow paths, the width in the arrangement direction of a large number of nozzles is narrower than the width in the direction perpendicular to the arrangement direction. Such a technique is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the nozzle substrate and other parts of the head chip are bonded together with an adhesive. When trying to fix them in close contact, it is inevitable that the adhesive oozes out into the ink flow path and solidifies. When the oozed adhesive enters the nozzle, there is a problem that the ink discharge characteristics are significantly deteriorated.

[0005] An object of this invention is to provide an inkjet head and an inkjet recording apparatus capable of arranging nozzles at a higher density while suppressing a decrease in ink discharge accuracy.

Means for Solving the Problems

[0006] To achieve the above object, the invention according to claim 1 is a pressure chamber substrate having a pressure chamber for applying pressure fluctuations to the internal ink, a nozzle substrate having nozzles for ejecting ink, a flow path substrate having a communication flow path for communicating the nozzle and the pressure chamber, and a head chip in which they overlap, wherein a cross-sectional shape of the pressure chamber perpendicular to the overlapping direction is such that a first width in a first direction is equal to or less than half of a first length in a second direction perpendicular to the first direction, and a second width in the first direction in at least a part of the communication flow path on a side in contact with the nozzle is wider than a first diameter of a connection port which is one end of the nozzle in contact with the flow path substrate and the first width. く、 The communication flow path includes a lower flow path having the second width and in contact with the nozzle substrate, and an upper flow path located between the lower flow path and the pressure chamber substrate and having a portion with a wall surface inclined such that the width in the first direction gradually increases between the first width and the second width toward the lower flow path. This is an inkjet head characterized by the above.

[0007] Further, the invention according to claim 2 is the inkjet head according to claim 1, wherein the nozzle has a tapered shape in which a diameter gradually decreases from the first diameter between the connection port and an opening for ejecting ink.

[0008] Further, the invention according to claim 3 is the inkjet head according to claim 1 or 2, wherein the first width is smaller than the first diameter.

[0009] Further, the invention according to claim 4 is the inkjet head according to any one of claims 1 to 3, wherein the second width is wider than a width obtained by adding twice a tolerance which is a maximum value of a predetermined manufacturing error related to bonding of the flow path substrate and the nozzle substrate to the first diameter.

[0010] Further, the invention according to claim 5 is the inkjet head according to claim 4, wherein the tolerance is 50 μm or less.

[0011] Further, the invention according to claim 6 is the inkjet head according to any one of claims 3 to 5, wherein the first diameter is 50 μm or more and 100 μm or less.

[0012] Further, the invention according to claim 7 is the inkjet head according to any one of claims 3 to 6, wherein the taper angle of the tapered shape of the nozzle is 10 degrees or more.

[0013] Further, the invention according to claim 8 is the inkjet head according to any one of claims 1 to 7, wherein the nozzle substrate is a metal member.

[0014] Further, the invention according to claim 9 is the inkjet head according to any one of claims 1 to 8, wherein the thickness of the flow path substrate related to the communication flow path is 100 μm or less.

[0015] Further, the invention according to claim 10 is the inkjet head according to any one of claims 1 to 9, wherein the pressure chamber substrate is characterized in that a piezoelectric member forming a drive wall and a plurality of pressure chambers penetrating the drive wall are alternately arranged in the first direction.

[0016] Further, the invention according to claim 11 is the inkjet head according to any one of claims 1 to 10, wherein the flow path substrate has individual ink discharge paths branching from the plurality of communication flow paths, and the inkjet head includes a common ink discharge path communicating with the plurality of individual ink discharge paths. This is the feature.

[0017] The invention according to claim 12 is an inkjet recording apparatus comprising the inkjet head according to any one of claims 1 to 11.

Effect of the Invention

[0018] According to the present invention, there is an effect that nozzles can be arranged at a higher density while suppressing a decrease in ink ejection accuracy.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus 1 which is an inkjet recording apparatus according to the present embodiment. In this FIG. 1, the case where the image forming apparatus 1 is viewed from the front is shown.

[0021] This image forming apparatus 1 is an inkjet recording apparatus that ejects ink from nozzles, and is, for example, a printer that has a line head and records a color image by ejecting a plurality of colors of ink at an appropriate timing while moving a recording medium M with respect to the line head. The image forming apparatus 1 includes a medium supply unit 10, a forming operation unit 20, a medium discharge unit 30, etc. In this image forming apparatus 1, the recording medium M stored in the medium supply unit 10 is conveyed and moved along a predetermined conveyance path to the forming operation unit 20, and after the image is recorded, it is discharged to the medium discharge unit 30.

[0022] The medium supply unit 10 feeds the recording media M stored therein one by one to the forming operation unit 20. As the recording medium M, in addition to printing papers of various thicknesses, various materials such as cells, films, and fabrics can be mentioned. Here, those that can be curved and supported on the outer peripheral surface of the image forming drum 21 are exemplified.

[0023] The medium supply unit 10 has a supply tray 11 for storing the recording medium M and a feeder board 12 for conveying the recording medium M from the supply tray 11 to the forming operation unit 20. The supply tray 11 is a plate-like member provided so that one or a plurality of recording media M can be placed thereon. The supply tray 11 is provided so as to move up and down according to the amount of the recording medium M placed on the supply tray 11, and in the vertical movement direction, the uppermost recording medium M is held at a position where it is conveyed by the feeder board 12. The feeder board 12 has a conveyance mechanism that drives an annular belt 123 whose inner side is supported by a plurality (for example, two) of rollers 121 and 122 to convey the recording medium M on the belt 123, and a supply unit that delivers the uppermost recording medium M placed on the supply tray 11 onto the belt 123. The feeder board 12 conveys the recording medium M delivered onto the belt 123 by the supply unit along the belt 123.

[0024] The forming operation unit 20 includes an image forming drum 21, a delivery unit 22, a drum heater 231, a head unit 24 (discharging operation unit), an irradiation unit 25, a delivery unit 26, etc.

[0025] The image forming drum 21 has a cylindrical outer shape, supports a maximum of three recording media M on the outer peripheral surface of the cylindrical portion, and performs a conveyance operation of conveying the recording medium M according to the rotational operation with respect to the central axis of the cylinder.

[0026] The delivery unit 22 delivers the recording medium M transferred from the medium supply unit 10 to the image forming drum 21. The delivery unit 22 includes a swing arm unit 221 that supports one end of the recording medium M conveyed by the feeder board 12, and a cylindrical delivery drum 222 that delivers the recording medium M carried by the swing arm unit 221 to the image forming drum 21. The recording medium M on the feeder board 12 is picked up by the swing arm unit 221 and delivered to the delivery drum 222, thereby guiding the recording medium M in a direction along the outer peripheral surface of the image forming drum 21 and delivering it to the image forming drum 21.

[0027] The drum heater 231 is located near the outer peripheral surface of the image forming drum 21 and heats this outer peripheral surface and the recording medium M. Here, the drum heater 231 is provided between the delivery position of the recording medium M to the image forming drum 21 by the delivery unit 22 and the image forming position on the recording medium M by the head unit 24 in the rotation direction of the image forming drum 21. The outer peripheral surface of the image forming drum 21 is heated by the drum heater 231, and the recording medium M carried thereon is set to an appropriate temperature. As a result, the curing speed of the recording medium M when the ink lands on the recording medium M is appropriately maintained, and a stable and high-quality image is recorded. For example, an infrared heater is used for this drum heater 231.

[0028] The head unit 24 ejects ink droplets from a plurality of nozzle openings provided on the surface (nozzle opening surface) of the head unit 24 that faces the one image formation target surface of the recording medium M that moves in accordance with the rotation of the image formation drum 21 at an appropriate timing, and lands the ink droplets on the image formation target surface of the recording medium M to record an image. In the image forming apparatus 1 of the present embodiment, a plurality of head units 24 are arranged at predetermined intervals in the conveyance direction of the recording medium M. Here, four head units 24 are arranged side by side corresponding to each of the four colors of ink. The four head units 24 output C (cyan), M (magenta), Y (yellow), and K (black) ink, respectively. These inks may, for example, undergo a phase change between a sol state and a gel state according to temperature and may be cured by irradiation with ultraviolet rays. The ink may be heated by an ink heater (not shown) as necessary.

[0029] The irradiation unit 25 irradiates energy rays (electromagnetic waves) of a predetermined wavelength, here ultraviolet rays in the near ultraviolet region (wavelength of about 400 nm), to cure and fix the ink ejected from the head unit 24 and landed on the recording medium M (that is, the image recorded by the ink). The irradiation unit 25 has, for example, a light emitting diode (LED 251) that emits ultraviolet rays, and emits light and irradiates ultraviolet rays by applying a voltage to the LED 251 to allow a current to flow. The irradiation unit 25 is positioned on the downstream side of the landing position of the ink ejected from the head unit 24 with respect to the recording medium M conveyed by the rotation of the image formation drum 21 and on the upstream side of the position where the recording medium M is delivered to the delivery unit 26, that is, at a position where ultraviolet rays can be irradiated onto the recording medium M.

[0030] Note that the configuration for emitting ultraviolet rays in the irradiation unit 25 is not limited to an LED. The irradiation unit 25 may have, for example, a mercury lamp. Further, when the ink has the property of being cured by receiving energy rays other than ultraviolet rays, various light sources that emit energy rays of the wavelength for curing the ink are provided instead of the above-described configuration for emitting ultraviolet rays.

[0031] The delivery unit 26 conveys the recording medium M after the image forming operation is completed and the landed ink has hardened to the medium discharge unit 30. The delivery unit 26 includes a cylindrical transfer roller 261, a plurality (for example, two) of rollers 262 and 263, and an annular belt 264 supported by the rollers 262 and 263 on the inner surface. The transfer roller 261 receives the recording medium M from the image forming drum 21 and guides it onto the belt 264. The delivery unit 26 conveys the recording medium M delivered from the transfer roller 261 onto the belt 264 together with the belt 264 that moves in a circular motion as the rollers 262 and 263 rotate, and sends it out to the medium discharge unit 30.

[0032] The medium discharge unit 30 stores the recording medium M sent out from the forming operation unit 20 by the delivery unit 26 until it is taken out by the user. The medium discharge unit 30 includes a plate-shaped discharge tray 31 and the like, and places the recording medium M after image formation on the discharge tray 31. Note that the conveyance of the recording medium M is not limited to the above configuration. The recording medium M may be conveyed by a belt that moves in a circular motion, a roller, or the like. Also, the conveyance surface may be a flat surface, and the head unit 24 and the irradiation unit 25 may be arranged in a row from the upstream side to the downstream side of the conveyance direction facing the flat surface. Further, the mechanism for delivering the recording medium M from the medium supply unit 10 to the forming operation unit 20 and the configuration for discharging it from the forming operation unit 20 to the medium discharge unit 30 may also be different from the above.

[0033] FIG. 2 is a bottom view of the ink ejection surface side of the head unit 24. The head unit 24 has a plurality of, here eight each, inkjet heads 240, and fixedly holds these inkjet heads 240 to a support member. On a head chip 241 located on the bottom surface of each inkjet head 240, openings of a plurality of nozzles N for discharging ink are arranged side by side. The arrangement range of the nozzles N in each inkjet head 240 extends over the entire recordable width to the recording medium M while partially overlapping with some other inkjet heads 240 in the X direction (the first direction) orthogonal to the conveyance direction (Y direction). The nozzles N of each inkjet head 240 (head chip 241) are located on nozzle rows extending in the X direction at four positions in the Y direction (the second direction). The nozzle positions on each nozzle row are shifted from each other by 1 / 4 of the interval between the nozzles N in each nozzle row. Therefore, the nozzles N are arranged continuously in the X direction at a predetermined interval (nozzle interval D) as a whole.

[0034] FIG. 3 is a diagram for explaining the schematic structure of the inkjet head 240. For the inkjet head 240, a cover H is attached to the upper side with respect to a housing F located at the lower part. The bottom surface of the housing F is open, and the above-described head chip 241 is exposed. On the upper surface side of the housing F, an inlet 2421 into which the supplied ink flows and outlets 2422, 2423 from which the discharged ink flows out extend. The inlet 2421 and the outlets 2422, 2423 are connected to a manifold located above the head chip 241 inside the housing F, respectively. Ink is supplied to an ink storage portion inside thereof, and ink is discharged from the ink storage portion. Ink is sent from the manifold to the individual nozzles N of the head chip 241.

[0035] Also, a circuit board 243 connects the inside and outside of the cover H via the upper end of the cover H, and a voltage signal is sent to an electrode for discharging ink from the nozzles N by the head chip 241 via a drive board inside the housing F. The circuit board 243 may be a flexible circuit board, although it is not particularly limited.

[0036] FIG. 4 is a diagram for explaining the ink flow path in the head chip 241. FIG. 4(a) shows a part of the nozzle N side in the cross section within the YZ plane of one of the nozzles N shown in FIG. 2.

[0037] The head chip 241 has a nozzle plate 63 (nozzle substrate) having nozzles N in the lowermost layer, and a flow path plate 62 (flow path substrate, also called a spacer flow path substrate) and a pressure chamber substrate 61 are sequentially laminated above it (+Z side). As described above, the ink is supplied from the ink storage portion of the manifold located further above the pressure chamber substrate 61.

[0038] The pressure chamber substrate 61 is made of a piezoelectric member, and the pressure chamber 71 penetrates vertically (Z direction). Electrodes (not shown) are located along the wall surface of the pressure chamber 71, and when a voltage is applied to the electrodes from the circuit board 243 via the drive board, this piezoelectric member forming the drive wall is deformed to impart pressure fluctuations to the ink inside the pressure chamber 71. The piezoelectric member is not particularly limited, but here it deforms in a shear mode. Further, a recess is provided in a portion of the pressure chamber substrate 61 in contact with the flow path plate 62, separated from the pressure chamber 71, and the recess serves as a common discharge flow path 74 (common ink discharge path) described later.

[0039] The flow path plate 62 has a communication flow path 72 that communicates the pressure chamber 71 of the pressure chamber substrate 61 with the nozzle N of the nozzle plate 63. The communication flow path 72 penetrates the flow path plate 62 in the vertical direction. The communication flow path 72 includes an upper flow path 721 having the same length as the pressure chamber 71 in a cross section parallel to the XY plane (perpendicular to the Z direction, which is the overlapping direction of the substrates in the head chip 241), and a lower flow path 722 that is longer than the pressure chamber 71. Further, individual discharge flow paths 73 (individual ink discharge paths) branch out and extend from both ends in the Y direction of the communication flow path 72, and are connected to the common discharge flow path 74 described above. Different from the pressure chamber 71 and the nozzle N, the flow path plate 62 is not directly related to ink ejection, and acts in a direction to lower the resonance frequency related to ink vibration by the length of the communication flow path 72. Therefore, it is better not to be thicker than necessary. For example, it is preferably 700 μm or less, and particularly preferably 100 μm or less. On the other hand, the lower limit of the length of the communication flow path 72 (the thickness of the flow path plate 62) may be as small as possible within the range that can be manufactured accurately, for example, 1 μm or more, as long as the lower flow path 722 can at least reduce ink pooling to the nozzle N.

[0040] The nozzle plate 63 has a nozzle N. One end of the nozzle N communicates with the communication flow path 72, and the other end is exposed and open to the outside. The nozzle plate 63 is a metal member, for example, SUS or nickel. The exposed part (outer surface) such as the bottom surface (-Z side) of the nozzle plate 63 may be coated with a water-repellent film (not shown) or the like to suppress troubles such as poor ink ejection and maintenance troubles caused by unnecessary ink adhering and drying and curing. (Note that the film itself is not included in the nozzle plate 63).

[0041] FIG. 4(b) shows a part of two adjacent rows in the Y direction among the nozzle rows extending in the X direction shown in FIG. 3, of the pressure chamber substrate 61 cut along the cross-section A of FIG. 4(a). The pressure chambers 71 corresponding to the respective nozzles N each have a width W1 (first width) in the X direction (direction along the nozzle row) and a length L1 (first length) in the Y direction (direction perpendicular to the nozzle row). The cross-sectional shape of the pressure chamber 71 is such that the length L1 is significantly longer than the width W1 (i.e., the aspect ratio is high), and here, L1 ≧ 2 × W1 (the width W1 is half or less of the length L1). According to the positional relationship of the nozzles N described above, the pressure chambers 71 corresponding to the respective nozzle rows are alternately arranged with the piezoelectric member (i.e., the drive wall) at intervals of 4D (four times the nozzle interval D) in the X direction. Since these two rows of pressure chambers 71 are arranged staggeredly in a checkerboard pattern, the interval in the X direction between these two rows of pressure chambers 71 is half (2D) of the above interval 4D. The thickness T of the piezoelectric member (drive wall) between two pressure chambers 71 adjacent in the X direction corresponding to the same nozzle row is obtained by subtracting the width W1 of the pressure chamber from the interval 4D (T = 4D - W1).

[0042] FIG. 5 is a view showing a cross-section cut along the section line BB of FIGS. 4(a) and (b). As described above, the communication flow path 72 is divided into an upper flow path 721 and a lower flow path 722 (at least a part from the side in contact with the nozzle N) (FIG. 5(a)). The width of the upper flow path 721 in the X direction is equal to the width W1 of the pressure chamber 71, while the width W2 (second width) of the lower flow path 722 in the X direction is wider than the width W1.

[0043] The cross-sectional shape of the nozzle N in the X direction is the same frustum of a cone shape as the cross-sectional shape in the Y direction shown in FIG. 4(a), that is, a tapered shape in which the diameter (diameter φ) gradually decreases from the connection port Ni with the communication flow path 72 to the opening Ne (ink ejection port). By setting the taper angle, that is, the inclination angle of the inner wall surface of the nozzle N with respect to the Z-axis direction, to be, for example, 10 degrees or more, stable high-speed ejection of ink becomes possible. Also, when the nozzle plate 63 is a metal member, in the punching process for forming the nozzle N, it is easier to form the nozzle N with a somewhat tapered angle. The maximum diameter φ0 (the first diameter. That is, the diameter φ at the connection port Ni) is larger than the width W1 and smaller than the width W2 (W1 < φ0 < W2). Further, as shown in FIG. 5(b), in the relative position of the nozzle plate 63 bonded to the pressure chamber substrate 61 and the flow path plate 62 formed integrally by an adhesive, a minute deviation (manufacturing error) may occur in manufacturing. Even considering the maximum value (tolerance d) of the width (error) allowed as a minute deviation between the central axis of the pressure chamber 71 and the communication flow path 72 and the central axis of the nozzle N, the relationship W2 ≧ φ0 + 2d (that is, the width W2 is wider than the width obtained by adding twice the tolerance d to the maximum diameter φ0) is satisfied so that the connection port Ni of the nozzle N is within the cross-sectional range of the communication flow path 72. This tolerance depends on the diameter φ of the nozzle N, particularly the ink ejection amount per drop, etc., and is not particularly limited. For example, when the maximum diameter φ0 of the nozzle N is 50 μm or more and 100 μm or less, the tolerance is 50 μm or less.

[0044] FIG. 6 is a cross-sectional view of the head chip 241 along the cross-section line CC of FIG. 4(a). As described above, in plan view, the lower flow path 722 is positioned so as to enclose the pressure chamber 71 that is longer in the Y direction than the width in the X direction. Note that the ratio of the width W1 to the length L1 of the pressure chamber 71 may be different from the ratio of the width W2 to the length L2 of the lower flow path 722. Also, the connection port Ni of the nozzle N protrudes in the width direction (X direction) from the range of the pressure chamber 71 in plan view, while being enclosed inside the lower flow path 722 in plan view.

[0045] In the shear-mode inkjet head 240, when the piezoelectric member between the pressure chambers 71 arranged in the X direction becomes thin, it affects deformation, the applied voltage during deformation, etc., so it is difficult to reduce the thickness T. Therefore, to narrow the interval between the nozzles in the nozzle row, the width W1 of the pressure chamber 71 has to be narrowed.

[0046] On the other hand, since the shape and size of the nozzle N also directly affect the ejection of ink, they cannot be freely changed. Also, if there is a portion where ink does not flow smoothly into the nozzle N and accumulates, the ink ejection characteristics from the nozzle N will deteriorate. Therefore, it is not preferable that the connection port Ni of the nozzle N has a portion wider than the connection surface with the nozzle N of the communication flow path 72. In the inkjet head 240, as described above, while making the width W1 near the pressure chamber 71 smaller than the maximum diameter φ0 of the nozzle N, the connection portion of the communication flow path 72 with the nozzle N is made to have a width W2 that is partially wider than the width W1 and the maximum diameter φ0 (diameter), thereby suppressing a decrease in the ink ejection characteristics from the nozzle N while reducing the interval 4D between each nozzle row.

[0047] Also, when the nozzle N has a tapered shape, it is easier to stably eject ink at high speed. However, the maximum diameter φ0, which is the diameter of the connection port Ni, becomes larger according to the taper angle with respect to the diameter of the opening Ne determined according to the droplet size from the nozzle N. Thus, by making the width W2 of the lower flow path 722 larger than the maximum diameter φ0, appropriate ink ejection becomes possible without deteriorating the ink ejection characteristics.

[0048] As described above, the inkjet head 240 of the present embodiment includes a pressure chamber substrate 61 having a pressure chamber 71 that applies pressure fluctuations to the internal ink, a nozzle plate 63 having nozzles N for discharging the ink, and a flow path plate 62 having communication flow paths 72 that communicate the nozzles N and the pressure chambers 71, and a head chip 241 in which they overlap. The cross-sectional shape of the pressure chamber 71 perpendicular to the stacking direction of each substrate is such that the width W1 in the X direction is less than or equal to half of the length L1 in the Y direction perpendicular to the X direction, and the width W2 in the X direction in the lower flow path 722 which is at least part of the communication flow path 72 on the side in contact with the nozzle N is wider than the diameter (maximum diameter φ0) and the width W1 of the connection port Ni which is one end in contact with the flow path plate 62 of the nozzle N. In this way, since there is a portion that is partially wider than the maximum diameter φ0 and the width W1 on the side of the communication flow path 72 in contact with the nozzle N, when the nozzle plate 63 is bonded to the flow path plate 62, a minute amount of adhesive leaking from the bonding surface is suppressed from entering the nozzle N, so that a decrease in the discharge characteristics of the nozzle N is suppressed and the ink can be discharged more stably. Further, if the width of the ink flow path widens discontinuously, the ink tends to accumulate at the widened corners and the like, and if such accumulation occurs in the nozzle N, it is likely to lead to a decrease in the discharge characteristics of the ink. However, by widening the width of the ink flow path upstream of the nozzle N, such a decrease in the discharge characteristics can be suppressed. In particular, by widening the flow path width only in the non-deformable flow path plate 62, it is possible to suppress an adverse effect on ink discharge even when the width W1 of the pressure chamber 71 is narrowed in order to arrange the nozzles N at a high density.

[0049] Also, the width W1 may be smaller than the maximum diameter φ0. In this way, even if the width of the pressure chamber 71 is made smaller than the maximum diameter φ0 of the nozzle N, a decrease in the ink discharge characteristics from the nozzle N can be suppressed, so that a denser arrangement of the nozzles N becomes possible.

[0050] Further, the nozzle N has a tapered shape in which the diameter φ gradually decreases from the maximum diameter φ0 between the connection port Ni and the opening Ne from which the ink is ejected. Thereby, the ink can be ejected more stably and at high speed. Further, since it becomes easier to form the nozzle N on the nozzle plate 63 made of a metal member, the durability of the head chip 241 can be improved as compared with a conventional nozzle plate made of resin or the like.

[0051] Further, the width W2 is wider than the width obtained by adding twice the tolerance d related to the bonding of the flow path plate 62 and the nozzle plate 63 to the maximum diameter φ0. That is, even when the bonding position is displaced to the maximum allowable extent, the connection port Ni of the nozzle N is included in the lower flow path 722 in plan view, so that it is possible to suppress the above-described adverse effect on the ink ejection characteristics from the nozzle N.

[0052] Further, the above tolerance is 50 μm or less. Thereby, at the nozzle pitch in many current inkjet heads 240, the axis of the flow from the pressure chamber 71 of the ink to the nozzle N does not greatly deviate, so that the ink ejection characteristics are not deteriorated.

[0053] Further, the maximum diameter φ0 of the nozzle N is 50 μm or more and 100 μm or less. Even if the connection port Ni is determined to be larger as described above as compared with the diameter of the opening Ne, the nozzles N can be arranged at a high density as compared with the size of the head chip 241.

[0054] Further, the taper angle of the tapered shape of the nozzle N is 10 degrees or more. Thereby, it becomes possible to stably eject the ink at high speed. Further, even with the nozzle plate 63 made of a metal member, it is easy to form the nozzle N by punching or the like, and an increase in cost or the like can be suppressed.

[0055] Further, the nozzle plate 63 is a metal member. Thereby, the durability of the head chip 241 can be improved. Further, even in this case, the above structure enables a higher density arrangement of the nozzles N.

[0056] Further, the thickness of the flow path plate 62 related to the communication flow path 72 is preferably 700 μm or less, more preferably 100 μm or less. As described above, the flow path plate 62 itself has no relation to the application of pressure fluctuations to the ink and has no relation to the ejection operation of the ink. On the other hand, it functions to lower the resonance frequency by the length of the communication flow path 72. Therefore, it is necessary for the connection between the pressure chamber 71 and the nozzle N, and by not making it much longer than the length required to suppress the deterioration of the ejection characteristics of the nozzle N by the lower flow path 722 as described above, the deterioration of the performance of the inkjet head 240 can be suppressed.

[0057] Further, in the pressure chamber substrate 61, a plurality of piezoelectric members forming drive walls and a plurality of pressure chambers 71 penetrating the drive walls are alternately arranged in the X direction. Such a structure in which both side surfaces of the pressure chamber 71 are sandwiched by piezoelectric members for driving is generally the application of pressure fluctuations to the ink due to the deformation of the piezoelectric member in the shear mode. In this configuration, since it is difficult to reduce the thickness of the drive wall, by partially leaving the lower flow path 722 as described above and making the width W1 of the pressure chamber 71 and the like smaller with respect to the length L1 and the maximum diameter φ0, a high-density arrangement of the nozzles N becomes possible.

[0058] Further, the flow path plate 62 has individual discharge flow paths 73 branched from the plurality of communication flow paths 72, and the inkjet head 240 includes a common discharge flow path 74 communicating with the plurality of individual discharge flow paths 73. Since bubbles and the like are likely to accumulate in this part due to the locally wide width W2 of the communication flow path 72, particularly the lower flow path 722, by branching the discharge flow path from the position of this communication flow path 72, bubbles can be effectively discharged, and thereby, the ink can be ejected more stably.

[0059] Further, the image forming apparatus 1 which is the inkjet recording apparatus of the present embodiment includes the above-described inkjet head 240. With such an image forming apparatus 1, a high-resolution and high-precision image can be recorded with a higher-density nozzle arrangement while suppressing the deterioration of the ejection characteristics.

[0060] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the above-described embodiment, it has been described that the widths W1 and W2 change stepwise between the upper flow path 721 and the lower flow path 722 in the flow path plate 62, but the wall surface may be slightly inclined at the boundary. Also, the lengths of the upper flow path 721 and the lower flow path 722 (the thickness of the flow path plate 62 corresponding to the relevant part) may be appropriately changed and set.

[0061] Also, in the above-described embodiment, it has been described that the width W1 of the pressure chamber is smaller than the maximum diameter φ0 of the nozzle N, but it is not necessarily required to satisfy this condition. The width W1 may be equal to or greater than the maximum diameter φ0.

[0062] Also, in the above-described embodiment, it has been described that the nozzle N has a tapered shape, but the diameter φ may be constant. Also, even in the case of a tapered shape, the taper angle may be less than 10 degrees.

[0063] Also, in the above-described embodiment, it has been described that the nozzle plate 63 is a metal member such as SUS or nickel, but other metal members may be used, or members other than metal members, for example, resin members, may be used.

[0064] Also, the specific numerical values shown in the above-described embodiment may be appropriately changed according to the resolution and ejection cycle of the inkjet head 240, etc.

[0065] Also, the arrangement of the nozzles N in the inkjet head 240 is not limited to that shown in the above-described embodiment. For example, all the nozzles N may be arranged in a single row, or a more two-dimensional arrangement may be used. Also, the nozzles N do not necessarily have to be arranged strictly in the X direction. Also, the pressure chamber 71 does not have to be deformed according to the deformation of the surrounding piezoelectric member in the shear mode. It may be deformed according to deformation in other modes, such as deformation in the bending mode.

[0066] Further, the inkjet head 240 does not necessarily have to include the individual discharge channels 73 and the common discharge channel 74. Also, the individual discharge channels 73 do not necessarily have to branch from both sides in the Y direction of the lower channel 722.

[0067] Further, the inkjet head 240 may be sold by transfer or the like independently of the image forming apparatus 1.

[0068] In the above embodiment, the pressure chamber 71 and the upper channel 721 have been described as being rectangular in plan view, but they do not necessarily have to be rectangular. Similar to what is shown in the lower channel 722, the corners may be somewhat rounded. Also, the nozzle N does not necessarily have to be circular in plan view. It may be elliptical or square. In this case, the diameter φ or the maximum diameter φ0 may be the maximum distance from the center of the connection port Ni or the opening Ne to the edge. In addition, the specific configurations, the contents and procedures of the processing operations, etc. shown in the above embodiment can be appropriately changed without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0069] 1 Image forming apparatus 10 Medium supply unit 11 Supply tray 12 Feeder board 121, 122 Rollers 123 Belt 20 Forming operation unit 21 Image forming drum 22 Delivery unit 221 Swing arm unit 222 Delivery drum 231 Drum heater 24 Head unit 240 Inkjet head 241 Head chip 2421 Inlet 2422, 2423 Outlets 243 Circuit board 25 Irradiation unit 26 Delivery unit 261 Transfer roller 262, 263 Rollers 264 Belt 30 Media discharge unit 31 Discharge tray 61 Pressure chamber substrate 62 Flow path plate 63 Nozzle plate 71 Pressure chamber 72 Communication flow path 721 Upper flow path 722 Lower flow path 73 Individual discharge flow path 74 Common discharge flow path F Housing H Cover M Recording medium N Nozzle Ne Opening Ni Connection port

Claims

1. A pressure chamber substrate having a pressure chamber for applying pressure fluctuations to the internal ink, A nozzle substrate having nozzles for ejecting ink, A flow path substrate having a communication flow path for communicating the nozzles and the pressure chamber, A head chip in which the above are overlapped, The cross-sectional shape of the pressure chamber perpendicular to the overlapping direction is such that the first width in the first direction is half or less of the first length in the second direction perpendicular to the first direction, The second width in the first direction of at least a part from the side in contact with the nozzle of the communication flow path is wider than the first diameter of the connection port which is one end of the nozzle in contact with the flow path substrate and the first width, The communication flow path has a lower flow path having the second width and in contact with the nozzle substrate, and an upper flow path located between the lower flow path and the pressure chamber substrate and having a wall surface inclined such that the width in the first direction gradually increases between the first width and the second width toward the lower flow path, An inkjet head characterized by the above.

2. The inkjet head according to claim 1, wherein the nozzle has a tapered shape in which the diameter gradually decreases from the first diameter between the connection port and the opening for ejecting ink.

3. The inkjet head according to claim 1 or 2, wherein the first width is smaller than the first diameter.

4. The inkjet head according to any one of claims 1 to 3, wherein the second width is wider than the width obtained by adding twice the tolerance, which is the maximum value of a predetermined manufacturing error related to the bonding of the flow path substrate and the nozzle substrate, to the first diameter.

5. The inkjet head according to claim 4, wherein the tolerance is 50 μm or less.

6. The inkjet head according to any one of claims 3 to 5, wherein the first diameter is 50 μm or more and 100 μm or less.

7. The inkjet head according to any one of claims 3 to 6, wherein the taper angle of the tapered shape of the nozzle is 10 degrees or more.

8. The inkjet head according to any one of claims 1 to 7, wherein the nozzle substrate is a metal member.

9. The inkjet head according to any one of claims 1 to 8, wherein the thickness of the flow path substrate related to the communication flow path is 700 μm or less.

10. The inkjet head according to any one of claims 1 to 9, wherein the pressure chamber substrate has a piezoelectric member forming a drive wall and a plurality of pressure chambers penetrating the drive wall, alternately arranged in the first direction.

11. The flow path substrate has individual ink discharge paths branching from the plurality of communication flow paths, and the inkjet head includes a common ink discharge path communicating with the plurality of individual ink discharge paths. The inkjet head according to any one of claims 1 to 10, characterized by the above.

12. An inkjet recording apparatus comprising the inkjet head according to any one of claims 1 to 11.

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