Inkjet head and inkjet recording device

Abstract

To provide an ink jet head and an ink jet recording device, which can reduce volume of ink droplets while maintaining discharge speed of the ink droplets.SOLUTION: An ink jet head includes an actuator and a driver. The actuator expands or contracts a pressure chamber for filling ink. The driver applies, to the actuator, a discharge pulse constituted of an expansion pulse for expanding the pressure chamber, a downtime, and a contraction pulse for contracting the pressure chamber and changes a width of the expansion pulse while maintaining a width between a center of the expansion pulse and a center of the contraction pulse.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] An embodiment of the present invention relates to an inkjet head and an inkjet recording apparatus. [Background technology]

[0002] Some inkjet heads apply ejection pulses to actuators that contract and expand pressure chambers to eject ink droplets from the pressure chambers onto a medium such as paper. The ejection pulses include an expansion pulse that expands the pressure chambers.

[0003] The inkjet head reduces the width of the expanding pulse to reduce the volume of the ink drop.

[0004] Conventionally, inkjet heads have a problem in that the ejection speed of ink droplets decreases when the width of the expanding pulse is reduced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-45780 A Summary of the Invention [Problem to be solved by the invention]

[0006] In order to solve the above problems, an inkjet head and an inkjet recording apparatus are provided that are capable of reducing the volume of ink droplets while maintaining the ink droplet ejection speed. [Means for solving the problem]

[0007] According to an embodiment, an inkjet head includes an actuator and a driver. The actuator expands or contracts a pressure chamber filled with ink. The driver applies to the actuator an ejection pulse including an expansion pulse for expanding the pressure chamber, a pause period, and a contraction pulse for contracting the pressure chamber, and changes a width of the expansion pulse while maintaining a width between a center of the expansion pulse and a center of the contraction pulse. The driver reduces the width of the expansion pulse from a predetermined value. The driver acquires gradation data relating to the gradation of the dot, sets an adjustment amount for reducing the width of the expansion pulse based on the gradation data, and reduces the width of the expansion pulse by cutting the same width from the start point and the end point of the expansion pulse based on the adjustment amount. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an inkjet recording apparatus according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the inkjet head according to the embodiment. [Diagram 3] FIG. 3 is an exploded perspective view of the inkjet head according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along the line FF in FIG. [Diagram 5] FIG. 5 is a block diagram showing an example of the configuration of a control system of the inkjet printing apparatus according to this embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the operation of the inkjet head according to the embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the operation of the inkjet head according to the embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the operation of the inkjet head according to the embodiment. [Figure 9] FIG. 9 is a diagram showing an example of an ejection pulse applied to the actuator according to the embodiment. [Figure 10] FIG. 10 is a graph showing the relationship between the adjustment amount of the expansion pulse and the ejection volume and ejection speed according to the embodiment. [Figure 11] FIG. 11 is a diagram showing an example of a conventional ejection pulse applied to an actuator. [Figure 12]FIG. 12 is a graph showing the relationship between the adjustment amount of the expansion pulse in the ejection pulse of FIG. 11 and the ejection volume and ejection speed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an inkjet recording apparatus according to an embodiment will be described with reference to the drawings. The inkjet recording device according to the embodiment forms an image on a medium such as paper using an inkjet head. The inkjet recording device ejects ink droplets from a pressure chamber of the inkjet head onto the medium, and prints an image on the medium. Examples of the inkjet recording device include an office inkjet recording device, a barcode inkjet recording device, a POS inkjet recording device, an industrial inkjet recording device, and a 3D inkjet recording device. Note that the medium on which the inkjet recording device forms an image is not limited to a specific configuration. The inkjet head of the printer according to the embodiment is an example of a liquid ejection head, and ink is an example of a liquid.

[0010] 1 is a schematic diagram showing an example of the configuration of an inkjet recording apparatus 1 according to an embodiment. The inkjet recording apparatus 1 forms an image on an image forming medium S or the like using a recording material such as ink. The inkjet recording apparatus 1 includes, as an example, a plurality of liquid ejection units 2, a head support mechanism 3 that movably supports the liquid ejection units 2, and a medium support mechanism 4 (support unit) that movably supports the image forming medium S. The image forming medium S is, for example, a sheet made of paper, cloth, resin, or the like.

[0011] As shown in FIG. 1, a plurality of liquid ejection units 2 are supported by a head support mechanism 3 in a state in which they are arranged in parallel in a predetermined direction. The head support mechanism 3 is attached to an endless belt 3b that is hung on a roller 3a. The inkjet recording device 1 can move the head support mechanism 3 in a main scanning direction A that is perpendicular to the transport direction of the image forming medium S by rotating the roller 3a. The liquid ejection unit 2 is integrally equipped with an inkjet head 10 and a circulation device 20. The liquid ejection unit 2 performs an ejection operation to eject, for example, ink I as a liquid from the inkjet head 10. As an example, the inkjet recording device 1 is a scan type that forms a desired image on the image forming medium S that is arranged opposite to the head support mechanism 3 by performing an ink ejection operation while moving the head support mechanism 3 back and forth in the main scanning direction A. Alternatively, the inkjet recording device 1 may be a single-pass type that performs an ink ejection operation without moving the head support mechanism 3. In this case, the roller 3a and the endless belt 3b may not be provided. In this case, the head support mechanism 3 is fixed to, for example, a housing of the inkjet recording device 1.

[0012] The liquid ejection units 2 eject, for example, four colors of ink corresponding to CMYK (cyan, magenta, yellow, and key (black)), that is, cyan ink, magenta ink, yellow ink, and black ink.

[0013] The inkjet head 10 will be described below with reference to Fig. 2 to Fig. 4. Note that each figure illustrates a circulation-type side-shooter inkjet head of a share-mode share-wall system. Note that the inkjet head 10 may be of other types.

[0014] Fig. 2 is a perspective view showing an example of the configuration of the inkjet head 10. Fig. 3 is an exploded perspective view showing an example of the configuration of the inkjet head 10. Fig. 4 is a cross-sectional view taken along the line FF in Fig. 2.

[0015] The inkjet head 10 is mounted on the inkjet recording device 1 and is connected to an ink tank via a tube-like component. Such an inkjet head 10 includes a head body 11, a unit portion 12, and a pair of circuit boards 13. The inkjet head 10 is an example of a waveform generating device.

[0016] The head body 11 is a device for ejecting ink. The head body 11 is attached to a unit portion 12. The unit portion 12 includes a manifold that forms part of a path between the head body 11 and the ink tank, and a member for mounting inside the inkjet recording device 1. A pair of circuit boards 13 are each attached to the head body 11.

[0017] 3 and 4, the head body 11 includes a base plate 15, a nozzle plate 16, a frame member 17, and a pair of drive elements 18. Inside the head body 11, as shown in Fig. 4, an ink chamber 19 to which ink is supplied is formed.

[0018] 3, the base plate 15 is formed in a rectangular plate shape from ceramics such as alumina. The base plate 15 has a flat mounting surface 21. The base plate 15 has a plurality of supply holes 22 and a plurality of discharge holes 23 opening in the mounting surface 21.

[0019] The supply holes 22 are provided in the center of the base plate 15, aligned in the longitudinal direction of the base plate 15. The supply holes 22 communicate with the ink supply portion 12a of the manifold of the unit portion 12. The supply holes 22 are connected to an ink tank in the circulation device 20 via the ink supply portion 12a. Ink from the ink tank is supplied to the ink chamber 19 through the ink supply portion and the supply holes 22.

[0020] The discharge holes 23 are arranged in two rows on either side of the supply hole 22. The discharge holes 23 communicate with the ink discharge portion 12b of the manifold of the unit portion 12. The discharge holes 23 are connected to an ink tank in the circulation device 20 via the ink discharge portion 12b. The ink in the ink chamber 19 is collected in the ink tank through the ink discharge portion 12b and the discharge holes 23. In this manner, the ink circulates between the ink tank and the ink chamber 19.

[0021] The nozzle plate 16 is formed of, for example, a rectangular polyimide film having a liquid repellent function on its surface. The nozzle plate 16 faces the mounting surface 21 of the base plate 15. The nozzle plate 16 is provided with a plurality of nozzles 25. The plurality of nozzles 25 are arranged in two rows along the longitudinal direction of the nozzle plate 16.

[0022] The frame member 17 is formed in a rectangular frame shape from, for example, a nickel alloy. The frame member 17 is interposed between the mounting surface 21 of the base plate 15 and the nozzle plate 16. The frame member 17 is bonded to both the mounting surface 21 and the nozzle plate 16. In other words, the nozzle plate 16 is attached to the base plate 15 via the frame member 17. The ink chamber 19 is formed surrounded by the base plate 15, the nozzle plate 16, and the frame member 17, as shown in FIG.

[0023] The driving element 18 is formed of two plate-shaped piezoelectric bodies made of, for example, lead zirconate titanate (PZT) The two piezoelectric bodies are bonded together so that their polarization directions are opposite to each other in the thickness direction.

[0024] The pair of drive elements 18 are bonded to the mounting surface 21 of the base plate 15, as shown in Fig. 3. The pair of drive elements 18 are arranged parallel to each other in the ink chamber 19 in correspondence with the two rows of nozzles 25, as shown in Fig. 4. The drive elements 18 are formed to have a trapezoidal cross section. The tops of the drive elements 18 are bonded to the nozzle plate 16.

[0025] A plurality of grooves 27 are provided in the driving element 18. The grooves 27 each extend in a direction intersecting the longitudinal direction of the driving element 18, and are aligned in the longitudinal direction of the driving element 18. The plurality of grooves 27 face the plurality of nozzles 25 of the nozzle plate 16. In the driving element 18 of this embodiment, as shown in FIG. 4, a plurality of pressure chambers 50 filled with ink are arranged in the grooves 27.

[0026] An electrode 28 is provided in each of the multiple grooves 27. The electrode 28 is formed, for example, by photoresist etching a thin nickel film. The electrode 28 covers the inner surface of the groove 27.

[0027] 3, a plurality of wiring patterns 35 are provided from the mounting surface 21 of the base plate 15 to the driving elements 18. These wiring patterns 35 are formed, for example, by photoresist etching a nickel thin film.

[0028] The wiring pattern 35 extends from one side end 21a and the other side end 21b of the mounting surface 21. The side end 21a and the side end 21b include not only the edge of the mounting surface 21 but also the surrounding area. Therefore, the wiring pattern 35 may be provided inside the edge of the mounting surface 21.

[0029] The wiring pattern 35 extending from one side end 21a will be representatively described below. The basic configuration of the wiring pattern 35 at the other side end 21b is similar to that of the wiring pattern 35 at one side end 21a.

[0030] As shown in Fig. 3 and Fig. 4, the wiring pattern 35 has a first portion 35a and a second portion 35b. The first portion 35a of the wiring pattern 35 is a portion that extends linearly from the side end portion 21a of the mounting surface 21 toward the driving element 18. The first portions 35a extend parallel to each other. The second portion 35b of the wiring pattern 35 is a portion that straddles the end portion of the first portion 35a and the electrode 28. The second portion 35b is electrically connected to each of the electrodes 28.

[0031] In one driving element 18, some of the multiple electrodes 28 constitute a first electrode group 31. Other several of the multiple electrodes 28 constitute a second electrode group 32.

[0032] The first electrode group 31 and the second electrode group 32 are separated at the center in the longitudinal direction of the driving element 18. The second electrode group 32 is adjacent to the first electrode group 31. The first electrode group 31 and the second electrode group 32 each include, for example, 159 electrodes 28.

[0033] 2, each of the pair of circuit boards 13 includes a board body 44 and a pair of film carrier packages (FCPs) 45. The FCP is also called a tape carrier package (TCP).

[0034] The board body 44 is a rigid printed wiring board formed in a rectangular shape. Various electronic components and connectors are mounted on the board body 44. In addition, a pair of FCPs 45 are attached to the board body 44, respectively.

[0035] Each of the pair of FCPs 45 has a flexible resin film 46 on which a plurality of wirings are formed, and a head drive circuit 47 connected to the plurality of wirings. The film 46 is a tape automated bonding (TAB) film. The head drive circuit 47 is an IC (integrated circuit) for applying a voltage to the electrodes 28. The head drive circuit 47 is fixed to the film 46 by resin.

[0036] One end of the FCP 45 is thermocompression-bonded to the first portion 35a of the wiring pattern 35 by an anisotropic conductive film (ACF) 48. As a result, the multiple wires of the FCP 45 are electrically connected to the wiring pattern 35.

[0037] When the FCP 45 is connected to the wiring pattern 35, the head drive circuit 47 is electrically connected to the electrodes 28 via the wiring of the FCP 45. The head drive circuit 47 applies a voltage to the electrodes 28 via the wiring of the film 46.

[0038] When the head drive circuit 47 applies a voltage to the electrode 28, the drive element 18 undergoes shear mode deformation, increasing or decreasing the volume of the pressure chamber 50 in which the electrode 28 is provided. This changes the pressure of the ink in the pressure chamber 50, causing the ink to be ejected from the nozzle 25. In this way, the drive element 18 separating the pressure chambers 50 serves as an actuator for applying pressure vibrations to the inside of the pressure chamber 50.

[0039] The circulation device 20 shown in Fig. 1 is integrally connected to the upper part of the inkjet head 10 by a connecting part made of metal or the like. The circulation device 20 has a predetermined circulation path configured to allow liquid to circulate through the ink tank and the inkjet head 10. The circulation device 20 has a pump for circulating the liquid. The liquid is supplied from the circulation device 20 through an ink supply unit into the inkjet head 10 by the action of the pump, and after passing through a predetermined flow path, is sent from the inkjet head 10 to the circulation device 20 through an ink discharge unit.

[0040] Furthermore, the circulation device 20 supplies the liquid to the circulation path from a cartridge serving as a supply tank provided outside the circulation path.

[0041] A description will be given of the main circuit configuration of the inkjet recording apparatus 1. Fig. 5 is a block diagram showing an example of the main circuit configuration of the inkjet recording apparatus 1 according to the embodiment.

[0042] The inkjet recording apparatus 1 includes a processor 101 , a ROM 102 , a RAM 103 , a communication interface 104 , a display unit 105 , an operation unit 106 , a head interface 107 , a bus 108 , and an inkjet head 10 .

[0043] The processor 101 corresponds to the central part of a computer that performs processing and control required for the operation of the inkjet recording apparatus 1. The processor 101 controls each part to realize various functions of the inkjet recording apparatus 1 based on programs such as system software, application software, or firmware stored in a ROM 102. The processor 101 is, for example, a central processing unit (CPU), a micro processing unit (MPU), a system on a chip (SoC), a digital signal processor (DSP), or a graphics processing unit (GPU). Alternatively, the processor 101 is a combination of these.

[0044] ROM 102 is a non-volatile memory used exclusively for reading data, which corresponds to the main memory of a computer centered around processor 101. ROM 102 stores the above-mentioned programs. ROM 102 also stores data and various setting values ​​used by processor 101 when performing various processes.

[0045] The RAM 103 is a memory used for reading and writing data, which corresponds to the main memory of a computer centered around the processor 101. The RAM 103 is used as a so-called work area for storing data that is temporarily used when the processor 101 performs various processes.

[0046] The communication interface 104 is an interface for allowing the inkjet recording apparatus 1 to communicate with a host computer or the like via a network or a communication cable.

[0047] The display unit 105 displays a screen for notifying various pieces of information to the operator of the inkjet recording apparatus 1. The display unit 105 is, for example, a display such as a liquid crystal display or an organic EL (electro-luminescence) display.

[0048] The operation unit 106 accepts operations by an operator of the inkjet recording apparatus 1. The operation unit 106 is, for example, a keyboard, a keypad, a touchpad, or a mouse. A touchpad arranged over the display panel of the display unit 105 can also be used as the operation unit 106. That is, the display panel of the touch panel can be used as the display unit 105, and the touchpad of the touch panel can be used as the operation unit 106.

[0049] The head interface 107 is provided to enable the processor 101 to communicate with the inkjet head 10. The head interface 107 transmits gradation data and the like to the inkjet head 10 under the control of the processor 101.

[0050] The bus 108 includes a control bus, an address bus, a data bus, etc., and transmits signals exchanged among the various parts of the inkjet recording apparatus 1 .

[0051] The inkjet head 10 includes a head driver 100 .

[0052] The head driver 100 is a drive circuit for operating the inkjet head 10. The head driver 100 is made up of a head drive circuit 47 and the like. The head driver 100 is, for example, a line driver. The head driver 100 stores waveform data WD.

[0053] The head driver 100 repeatedly generates a single drive signal based on the waveform data WD. The head driver 100 then controls the number of times droplets are ejected onto each pixel on the image forming medium S based on the gradation data. Each time a single ejection pulse is applied, one shot of ink (main droplet) is ejected from the nozzle 25. Therefore, the inkjet recording device 1 expresses shading by, for example, the number of shots of ink ejected onto each pixel. That is, the more sets of ink that are ejected onto one pixel, the darker the corresponding color will be at that pixel.

[0054] The head driver 100 is an example of a waveform generating device, and operates as a generating unit by generating a drive signal.

[0055] As an example, the head driver 100 is transferred to an administrator of the head driver 100 with the waveform data WD stored therein. The head driver 100 may be transferred to the administrator without the waveform data WD stored in the head driver 100. The head driver 100 may also be transferred to the administrator with other waveform data stored therein. The waveform data WD may then be transferred separately to the administrator and written to the head driver 100 under the operation of the administrator or a serviceman. The waveform data WD can be transferred in this case by recording it on a removable storage medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory, or by downloading it via a network or the like.

[0056] When a drive signal is applied, the drive element 18, which is a piezoelectric body, undergoes shear mode deformation. Due to this deformation, the volume of the pressure chamber 50 changes.

[0057] The pressure chamber 50 is in a normal state when the potential of the drive signal is zero. The potential of the drive signal in the normal state is not limited to zero, but may be any predetermined potential. When the potential of the drive signal is positive, the pressure chamber 50 contracts and the volume of the pressure chamber 50 decreases compared to the normal state. When the potential of the drive signal is negative, the pressure chamber 50 expands and the volume of the pressure chamber 50 increases compared to the normal state. The pressure of the ink in the pressure chamber 50 changes in accordance with the above-mentioned change in the volume of the pressure chamber 50. The inkjet head 10 ejects ink by applying an ejection pulse having a specific waveform.

[0058] Next, examples of the state of the pressure chamber 50 will be described. The pressure chamber 50 changes to a normal state, a PULL state, or a PUSH state.

[0059] First, the normal state will be described with reference to Fig. 6.

[0060] Here, an explanation will be given taking as an example the pressure chamber 50b, which is one of the pressure chambers 50. The pressure chamber 50b is formed between the pressure chamber 50a and the pressure chamber 50c. The pressure chamber 50b is formed by the driving element 18a and the driving element 18b. The pressure chambers 50a to 50c are provided with electrodes 28a to 28c.

[0061] In the normal state, the pressure chamber 50b is in the default state. As shown in Fig. 6, the head driver 100 sets the potentials of the electrode 28b formed in the pressure chamber 50b and the electrodes 28a and 28c formed in the pressure chambers 50a and 50c adjacent to the pressure chamber 50b to a voltage +V. In this state, the driving element 18a sandwiched between the pressure chambers 50a and 50b and the driving element 18b sandwiched between the pressure chambers 50b and 50c do not generate any distortion. The head driver 100 may set the electrodes 28a to 28c to the potential GND.

[0062] Next, the PULL state will be described with reference to Fig. 7.

[0063] The PULL state is a state in which the pressure chamber 50b is expanded. As shown in Fig. 7, the head driver 100 sets the electrode 28b of the pressure chamber 50b to a potential GND, and applies a voltage +V to the electrodes 28a and 28c of the pressure chambers 50a and 50c. In this state, an electric field of the voltage V acts on each of the drive elements 18a and 18b in a direction perpendicular to the polarization direction of the drive element 18. Due to this action, each of the drive elements 18a and 18b deforms outward so as to expand the volume of the pressure chamber 50b.

[0064] Next, the PUSH state will be described with reference to Fig. 8.

[0065] In the PUSH state, the pressure chamber 50b is contracted. As shown in Fig. 8, the head driver 100 applies a voltage +V to the electrode 28b of the pressure chamber 50b, and sets the electrodes 28a and 28c of the pressure chambers 50a and 50c to GND potential. In this state, an electric field of voltage V acts on each of the drive elements 18a and 18b in the opposite direction to the drive voltage in the PULL state. Due to this action, each of the drive elements 18a and 18b deforms inward so as to contract the volume of the pressure chamber 50b.

[0066] When the volume of the pressure chamber 50b is expanded or contracted, a pressure vibration occurs in the pressure chamber 50b. This pressure vibration increases the pressure in the pressure chamber 50b, and ink droplets are ejected from the nozzle 25 that communicates with the pressure chamber 50b.

[0067] In this way, the driving elements 18a and 18b separating the pressure chambers 50a, 50b, and 50c function as actuators for applying pressure vibrations to the inside of the pressure chamber 50b, the walls of which are the driving elements 18a and 18b. That is, the pressure chamber 50 is expanded or contracted by the operation of the driving elements 18.

[0068] Furthermore, each pressure chamber 50 shares a drive element 18 (partition) with the adjacent pressure chamber 50. For this reason, the head driver 100 cannot drive each pressure chamber 50 individually. The head driver 100 divides each pressure chamber 50 into (n+1) groups, where n (n is an integer of 2 or more) chambers are arranged, and drives them. In this embodiment, a case of so-called three-division drive in which the head driver 100 divides each pressure chamber 50 into three groups, where every two pressure chambers are arranged, and drives them is illustrated. Note that three-division drive is merely an example, and four-division drive or five-division drive may also be used.

[0069] Next, the ejection pulses that the head driver 100 applies to the driving elements 18 will be described. The head driver 100 applies an ejection pulse to the driving element 18 to cause the nozzle 25 to eject a predetermined amount of ink droplets.

[0070] Fig. 9 shows the waveform of an ejection pulse applied by the head driver 100 to the driving element 18. In Fig. 9, the horizontal axis indicates elapsed time, and the vertical axis indicates driving voltage. A driving voltage higher than a reference voltage (for example, 0 V) ​​contracts the volume of the pressure chamber 50. A driving voltage lower than the reference voltage expands the volume of the pressure chamber 50.

[0071] As shown in FIG. 9, the ejection pulse is made up of an expansion pulse, a pause period, and a contraction pulse.

[0072] First, the head driver 100 applies an expansion pulse to the driving element 18. The width of the expansion pulse is T1 (default value) in an unadjusted state. For example, T1 is the width of the expansion pulse that maximizes the volume of the ink droplet. The expansion pulse is a pulse that applies a predetermined drive voltage for a predetermined time (for example, T1).

[0073] The expansion pulse expands the volume of the pressure chamber 50 formed by the drive element 18. That is, the head driver transitions the pressure chamber 50 from the normal state to the PULL state. When the pressure chamber 50 is in the PULL state, the pressure in the pressure chamber 50 decreases. When the pressure in the pressure chamber 50 decreases, ink is supplied to the pressure chamber 50 from the common ink chamber.

[0074] The head driver 100 provides a pause period having a predetermined width after applying the expansion pulse. That is, the head driver 100 shifts the pressure chamber 50 from the PULL state to the normal state after a predetermined time has elapsed in the PULL state.

[0075] When the idle period has elapsed, the head driver 100 applies a contraction pulse to the driving element 18. The contraction pulse has a predetermined width. The contraction pulse is a pulse that applies a predetermined driving voltage for a predetermined time. The contraction pulse contracts the volume of the pressure chamber 50 formed by the driving element 18.

[0076] That is, the head driver 100 transitions the pressure chamber 50 from the normal state to the PUSH state. After a predetermined time has elapsed since transitioning from the normal state to the PUSH state, the head driver 100 transitions the pressure chamber 50 from the PUSH state to the normal state.

[0077] The head driver 100 applies an ejection pulse to the driving element 18 as described above, thereby ejecting ink from the pressure chamber 50 .

[0078] Moreover, the width between the center of the expansion pulse and the center of the contraction pulse is 2AL. AL (Acoustic Length) is half the time of the natural vibration period of the pressure in the pressure chamber 50. In other words, 2AL is the time of the natural vibration period of the pressure in the pressure chamber 50.

[0079] Next, an example of the operation of the head driver 100 to adjust the width of the expanding pulse will be described. For example, the head driver 100 acquires gradation data indicating the gradation of the dots from the processor 101 or the like. Based on the gradation data, the head driver 100 adjusts the width of the expansion pulse so that the volume of the ejected ink droplets (ejection volume) becomes a predetermined volume.

[0080] The head driver 100 sets an adjustment amount for adjusting the width of the expansion pulse based on the gradation data, etc. Here, the adjustment amount is a value for subtracting from T1 to calculate the adjusted width.

[0081] As shown in Fig. 9, the head driver 100 adjusts the width of the expanding pulse by trimming the same width from each of the start and end points of the expanding pulse toward the inside. Here, the head driver 100 trims Tc from each of the start and end points of the expanding pulse toward the inside. Tc is half the adjustment amount. The width of the expanding pulse after adjustment is T1-2Tc.

[0082] That is, the head driver 100 reduces the width of the expanding pulse by 2Tc while maintaining the width between the center of the expanding pulse and the center of the contracting pulse at 2AL.

[0083] Next, the relationship between the adjustment amount and the ejection volume and ejection speed will be described. Fig. 10 is a graph showing the relationship between the adjustment amount and the ejection volume and ejection speed. In Fig. 10, the horizontal axis shows the adjustment amount (ns). The vertical axis shows the ejection volume (pl) and ejection speed (m / s). Fig. 10 also shows the ejection volume and ejection speed when three divisions are driven in sequence. Fig. 10 also shows the ejection volume and ejection speed of the sixth ink droplet in multi-drop drive.

[0084] As shown in Figure 10, as the adjustment amount increases (the width of the expansion pulse decreases), the ejection volume decreases. Also, as the adjustment amount increases, the ejection speed decreases gradually.

[0085] Next, a conventional operation example in which the head driver 100 adjusts the width of the expanding pulse will be described. FIG. 11 is a diagram for explaining a conventional operation example in which the head driver 100 adjusts the width of the expanding pulse.

[0086] Fig. 11 shows the waveform of an ejection pulse applied by the head driver 100 to the driving element 18. In Fig. 11, the horizontal axis indicates elapsed time, and the vertical axis indicates driving voltage. A driving voltage higher than a reference voltage (for example, 0 V) ​​contracts the volume of the pressure chamber 50. A driving voltage lower than the reference voltage expands the volume of the pressure chamber 50.

[0087] As shown in FIG. 11, the ejection pulse is made up of an expansion pulse, a pause period, and a contraction pulse.

[0088] The head driver 100 sets an adjustment amount for adjusting the width of the expanding pulse based on the gradation data, etc. Once the adjustment amount is set, the head driver 100 adjusts the width of the expanding pulse based on the adjustment amount.

[0089] 11, the head driver 100 adjusts the width of the expanding pulse by trimming the width from the starting point of the expanding pulse toward the inside. Here, the head driver 100 trims Ta from the starting point of the expanding pulse. Ta is the amount of adjustment. The width of the expanding pulse after adjustment is T1-Ta. In this case, the distance between the center of the expansion pulse and the center of the contraction pulse varies from 2AL.

[0090] Next, the relationship between the adjustment amount and the ejection volume and ejection speed in the conventional example will be described. Fig. 12 is a graph showing the relationship between the adjustment amount and the ejection volume and ejection speed in a conventional example. In Fig. 12, like Fig. 10, the horizontal axis shows the adjustment amount (ns). The vertical axis shows the ejection volume (pl) and ejection speed (m / s). Fig. 12 also shows the ejection volume and ejection speed when three divisions are driven in sequence. Fig. 12 also shows the ejection volume and ejection speed of the sixth ink droplet in multi-drop drive.

[0091] As shown in Figure 12, as the adjustment amount increases (the width of the expansion pulse decreases), the ejection volume decreases. Also, as the adjustment amount increases, the ejection velocity decreases.

[0092] Comparing FIG. 10 with FIG. 12, when the adjustment amount is 600 ns, the ejection volume is approximately 19 pl in both cases. Furthermore, when the adjustment amount is 600 ns, the ejection speed is approximately 10.5 m / s in Fig. 10 (embodiment), whereas the ejection speed is approximately 8.5 m / s in Fig. 12 (conventional example). Therefore, in this embodiment, when the width of the ejection pulse is reduced by the same amount, the ejection volume is approximately the same, but the ejection speed is less likely to decrease compared to the conventional example. Therefore, when the width of the ejection pulse is reduced, the inkjet head 10 according to the embodiment can reduce the ejection volume while maintaining the ejection speed.

[0093] The inkjet head 10 may be of a non-circulating type. The head driver 100 may also apply an auxiliary pulse before applying the ejection pulse, and may also apply a cancel pulse that further suppresses residual vibration after applying the ejection pulse.

[0094] The head driver 100 may also increase the width of the expansion pulse of the ejection pulse. In this case, the head driver 100 increases the width of the expansion pulse while maintaining the width between the center of the expansion pulse and the center of the contraction pulse at 2AL. That is, the head driver 100 adds a predetermined width from each of the start and end points of the expansion pulse toward the outside.

[0095] The expansion pulse may have a shape in which the voltage increases or decreases stepwise, and the contraction pulse may have a shape in which the voltage increases or decreases stepwise.

[0096] The inkjet head configured as above adjusts the width of the expansion pulse in the ejection pulse to reduce the ejection volume. The inkjet head also adjusts the width of the expansion pulse while maintaining the width between the center of the expansion pulse and the center of the contraction pulse in the ejection pulse at 2AL. As a result, the inkjet head adjusts the width of the expansion pulse while maintaining the width between the center of the expansion pulse and the center of the contraction pulse in an optimal state for ejection. Therefore, the inkjet head can reduce the volume of the ink droplet while maintaining the ejection speed.

[0097] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. The invention as originally claimed in the present application is set forth below. [1] an actuator for expanding or contracting a pressure chamber filled with ink; applying to the actuator an ejection pulse including an expansion pulse for expanding the pressure chamber, a pause period, and a contraction pulse for contracting the pressure chamber; Varying the width of the expansion pulse while maintaining the width between the center of the expansion pulse and the center of the contraction pulse. Driver and An inkjet head comprising: [2] The width between the center of the expansion pulse and the center of the contraction pulse is the natural vibration period of the pressure chamber. [1] The inkjet head according to the present invention. [3] The driver reduces the width of the expanding pulse from a predetermined value. The inkjet head according to [1] or [2]. [4] The driver includes: Obtain gradation data related to the gradation of the dots, setting an adjustment amount for reducing the width of the extension pulse based on the gradation data; reducing the width of the extended pulse by removing the same width from the start point and the end point of the extended pulse based on the adjustment amount; [3] The inkjet head according to the present invention. [5] An inkjet recording apparatus that ejects ink droplets onto a medium, A support portion that supports the medium; [1] to [4], and an ink-jet head according to any one of the above. An inkjet recording apparatus comprising: [Explanation of symbols]

[0098] 1...inkjet recording device, 2...liquid ejection section, 3...head support mechanism, 3a...roller, 3b...endless belt, 4...medium support mechanism, 10...inkjet head, 11...head body, 12...unit section, 12a...ink supply section, 12b...ink discharge section, 13...circuit board, 15...base plate, 16...nozzle plate, 17...frame member, 18...driving element, 18a...driving element, 18b...driving element, 19...ink chamber, 20...circulation device, 21...mounting surface, 21a...side end, 21b...side end, 22...supply hole, 23...discharge hole, 25...nozzle, 27...groove, 28...electrode, 28a...electrode, 28 b...electrode, 28c...electrode, 31...first electrode group, 32...second electrode group, 35...wiring pattern, 35a...first part, 35b...second part, 44...substrate main body, 45...film carrier package (FCP), 46...film, 47...head drive circuit, 48...anisotropic conductive film (ACF), 50...pressure chamber, 50a...pressure chamber, 50b...pressure chamber, 50c...pressure chamber, 100...head driver, 101...processor, 102...ROM, 103...RAM, 104...communication interface, 105...display unit, 106...operation unit, 107...head interface, 108...bus.

Claims

1. An actuator that expands or contracts a pressure chamber filled with ink, applying a discharge pulse composed of an expansion pulse for expanding the pressure chamber, a rest period, and a contraction pulse for contracting the pressure chamber to the actuator, changing the width of the expansion pulse while maintaining the widths of the center of the expansion pulse and the center of the contraction pulse, a driver, comprising, the driver reduces the width of the expansion pulse from a predetermined value, the driver, obtains tone data regarding the tone of dots, sets an adjustment amount for reducing the width of the expansion pulse based on the tone data, reducing the width of the expansion pulse by cutting the same width from the start point and the end point of the expansion pulse based on the adjustment amount, an inkjet head.

2. The widths of the center of the expansion pulse and the center of the contraction pulse are the natural vibration period of the pressure chamber, The inkjet head according to Claim 1.

3. An inkjet recording apparatus that discharges ink droplets onto a medium, a support portion that supports the medium, the inkjet head according to Claim 1 or 2, an inkjet recording apparatus comprising.

Images