阅读说明：本技术 液体喷头及打印机 (Liquid jet head and printer ) 是由 高村纯 于 2021-03-04 设计创作，主要内容包括：本发明提供可以防止印字品质的降低的液体喷头及打印机。根据实施方式,液体喷头具备致动器、以及控制部。致动器使与喷出油墨的喷嘴连通的压力室扩展或收缩。控制部针对所述致动器,在施加了使所述压力室扩展的扩展脉冲之后,施加使所述压力室收缩为第一体积的第一收缩脉冲,并施加使所述压力室的体积收缩为小于所述第一体积的第二体积的第二收缩脉冲。所述第二收缩脉冲的宽度包括从所述第一收缩脉冲变为所述第二收缩脉冲之后、从形成于所述喷嘴的弯液面向所述压力室的内部推进的状态变为所述弯液面向所述压力室的外部推进的状态的第一时间点。(The invention provides a liquid ejecting head and a printer capable of preventing printing quality from being reduced. According to an embodiment, a liquid ejecting head includes an actuator and a control unit. The actuator expands or contracts a pressure chamber communicating with a nozzle that ejects ink. The control unit applies, to the actuator, a first contraction pulse for contracting the pressure chamber into a first volume after an expansion pulse for expanding the pressure chamber is applied, and applies a second contraction pulse for contracting the volume of the pressure chamber into a second volume smaller than the first volume. The width of the second contraction pulse includes a first time point from a state in which a meniscus formed at the nozzle advances toward the inside of the pressure chamber to a state in which the meniscus advances toward the outside of the pressure chamber after the first contraction pulse is changed to the second contraction pulse.)

1. A liquid ejecting head includes:

an actuator that expands or contracts a pressure chamber communicating with a nozzle that ejects ink; and

a control unit that applies, to the actuator, a first contraction pulse that contracts the pressure chamber to a first volume after an expansion pulse that expands the pressure chamber is applied, and applies a second contraction pulse that contracts the volume of the pressure chamber to a second volume smaller than the first volume,

the width of the second contraction pulse includes a first time point from a state in which a meniscus formed at the nozzle advances toward the inside of the pressure chamber to a state in which the meniscus advances toward the outside of the pressure chamber after the first contraction pulse is changed to the second contraction pulse.

2. The liquid ejection head according to claim 1,

the first time point is a time point at which the flow velocity of the meniscus becomes zero for the third time after the control unit applies the extension pulse.

3. The liquid ejection head according to claim 1 or 2,

the first contraction pulse has a width including a second point in time at which a state in which the meniscus advances to the outside of the pressure chamber changes to a state in which the meniscus advances to the inside of the pressure chamber.

4. The liquid ejection head according to claim 1 or 2,

a period between the first time point and an end time point of the second contraction pulse is equal to or less than one-fourth of a natural vibration cycle of the pressure chamber.

5. The liquid ejection head according to claim 3,

a period between the first time point and an end time point of the second contraction pulse is equal to or less than one-fourth of a natural vibration cycle of the pressure chamber.

6. A printer that ejects liquid droplets onto a medium, the printer comprising:

a conveying mechanism that conveys a medium; and

a liquid spray-head is arranged on the upper surface of the shell,

the liquid ejecting head includes:

an actuator that expands or contracts a pressure chamber communicating with a nozzle that ejects ink; and

a control unit that applies, to the actuator, a first contraction pulse that contracts the pressure chamber to a first volume after an expansion pulse that expands the pressure chamber is applied, and applies a second contraction pulse that contracts the volume of the pressure chamber to a second volume smaller than the first volume,

the width of the second contraction pulse includes a first time point from a state in which a meniscus formed at the nozzle advances toward the inside of the pressure chamber to a state in which the meniscus advances toward the outside of the pressure chamber after the first contraction pulse is changed to the second contraction pulse.

7. The printer according to claim 6,

the first time point is a time point at which the flow velocity of the meniscus becomes zero for the third time after the control unit applies the extension pulse.

8. Printer according to claim 6 or 7,

the first contraction pulse has a width including a second point in time at which a state in which the meniscus advances to the outside of the pressure chamber changes to a state in which the meniscus advances to the inside of the pressure chamber.

9. Printer according to claim 6 or 7,

a period between the first time point and an end time point of the second contraction pulse is equal to or less than one-fourth of a natural vibration cycle of the pressure chamber.

10. The printer according to claim 8,

a period between the first time point and an end time point of the second contraction pulse is equal to or less than one-fourth of a natural vibration cycle of the pressure chamber.

Technical Field

Embodiments of the present invention relate to a liquid ejecting head and a printer.

Background

Among the inkjet heads, there are the following ones: an ejection pulse is applied to an actuator that contracts and expands a pressure chamber, and an ink droplet is ejected from the pressure chamber to a medium such as a sheet of paper. The ink droplets thus ejected may fly in a state extending in the flying direction. As a result, a metal spot or blur may occur on the medium.

Therefore, in the conventional ink jet head, the printing quality may be degraded.

Disclosure of Invention

To solve the above-described problems, a liquid ejecting head and a printer capable of preventing deterioration of printing quality are provided.

According to an embodiment, a liquid ejecting head includes an actuator and a control unit. The actuator expands or contracts a pressure chamber communicating with a nozzle that ejects ink. The control unit applies, to the actuator, a first contraction pulse for contracting the pressure chamber into a first volume after an expansion pulse for expanding the pressure chamber is applied, and applies a second contraction pulse for contracting the volume of the pressure chamber into a second volume smaller than the first volume. The width of the second contraction pulse includes a first time point from a state in which a meniscus formed at the nozzle advances toward the inside of the pressure chamber to a state in which the meniscus advances toward the outside of the pressure chamber after the first contraction pulse is changed to the second contraction pulse.

Drawings

Fig. 1 is a block diagram showing an example of the configuration of a printer according to the embodiment.

Fig. 2 shows an example of a perspective view of an inkjet head according to an embodiment.

Fig. 3 is a cross-sectional view of an ink jet head according to an embodiment.

Fig. 4 is a longitudinal sectional view of the inkjet head according to the embodiment.

Fig. 5 is a block diagram showing an example of the configuration of the head drive circuit according to the embodiment.

Fig. 6 is a diagram illustrating an example of the operation of the inkjet head according to the embodiment.

Fig. 7 is a diagram illustrating an example of the operation of the inkjet head according to the embodiment.

Fig. 8 is a diagram illustrating an example of the operation of the inkjet head according to the embodiment.

Fig. 9 is a diagram illustrating an example of the operation of the inkjet head according to the embodiment.

Fig. 10 is a diagram showing an example of a drive waveform applied to the actuator according to the embodiment.

Fig. 11 is a diagram showing an example of a drive waveform applied to the actuator according to the embodiment.

Description of the reference numerals

A first piezoelectric component, a 2.. a.second piezoelectric component, a 3.. a.slot, a 4.. a.electrode, a 5.. a.common ink chamber, a 6.. a.top plate, a 7.. an.orifice plate, an 8.. a.nozzle, a 9.. a.base substrate, a 10.. an.electrode, an 11.. a.printed substrate, a 12.. a.driver IC, a 13.. a.conductive pattern, a 14.. a.lead, a 15.. a-15 c.. a.pressure chamber, a 16.. a.actuator, a 16a and a 16 b.a.partition wall, a 20.. a.bent, a 51.. a.52.. a.a.curved A 62.. a curve, a 63.. a curve, 81-83.. a time point, 91-93.. a time point, 100.. an inkjet head, 101.. a head driving circuit, 102.. a channel group, 200.. a printer, 201.. a processor, 202.. a ROM, 203.. a RAM, an operating panel, 205.

Detailed Description

Next, a printer according to an embodiment will be described with reference to the drawings.

The printer according to the embodiment forms an image on a medium such as paper using an inkjet head. The printer ejects ink in a pressure chamber provided in the inkjet head to the medium to form an image on the medium. Examples of the printer include an office printer, a two-dimensional code printer, a POS printer, an industrial printer, and a 3D printer. Note that the medium on which the printer forms the image is not limited to a specific configuration. The inkjet head provided in the printer according to the embodiment is an example of a liquid ejecting head, and the ink is an example of a liquid. For example, the liquid ejecting head may eject a chemical solution or the like.

Fig. 1 is a block diagram showing an example of the configuration of a printer 200.

As shown in fig. 1, the printer 200 includes a processor 201, a ROM202, a RAM203, an operation panel 204, a communication interface 205, a conveyance motor 206, a motor drive circuit 207, a pump 208, a pump drive circuit 209, the inkjet head 100, and the like. The inkjet head 100 includes a head drive circuit 101 (control unit), a channel group 102, and the like.

Further, the printer 200 includes a bus 211 of an address bus, a data bus, and the like. The processor 201 is connected to the ROM202, RAM203, operation panel 204, communication interface 205, motor drive circuit 207, pump drive circuit 209, and head drive circuit 101 directly or via an input/output circuit via the bus 211. The motor drive circuit 207 is connected to the conveyance motor 206. The pump drive circuit 209 is connected to the pump 208. The head drive circuit 101 is connected to the channel group 102.

Note that the printer 200 may have a configuration as needed in addition to the configuration shown in fig. 1, or a specific configuration may be removed from the printer 200.

The processor 201 has a function of controlling the overall operation of the printer 200. The processor 201 may also include an internal cache, various interfaces, and the like. The processor 201 realizes various processes by executing an internal cache or a program stored in advance in the ROM 202. The processor 201 realizes various functions as the printer 200 according to an operating system, an application program, and the like.

Note that a part of the various functions realized by the processor 201 executing the program may also be realized by a hardware circuit. In this case, the processor 201 controls functions implemented by hardware circuits.

The ROM202 is a nonvolatile memory in which a control program, control data, and the like are stored in advance. The control program and the control data stored in the ROM202 are installed in advance in accordance with the specification of the printer 200. For example, the ROM202 stores an operating system, application programs, and the like.

The RAM203 is a volatile memory. The RAM203 temporarily stores data and the like being processed by the processor 201. The RAM203 holds various application programs and the like based on commands from the processor 201. In addition, the RAM203 may store data necessary for executing the application program, the execution result of the application program, and the like. The RAM203 may also function as an image memory for expanding print data.

The operation panel 204 is an interface for receiving an input of an instruction from an operator and displaying various information to the operator. The operation panel 204 includes an operation unit for receiving an instruction input and a display unit for displaying information.

As the operation of the operation unit, the operation panel 204 transmits a signal indicating an operation received from the operator to the processor 201. For example, the operation unit is provided with function keys such as a power key, a paper feed key, and an error release key.

The operation panel 204 displays various information under the control of the processor 201 as an operation of the display unit. For example, the operation panel 204 displays the status and the like of the printer 200. For example, the display unit is constituted by a liquid crystal display.

Note that the operation unit may be formed of a touch panel. In this case, the display portion may be formed integrally with the touch panel as the operation portion.

The communication interface 205 is an interface for transmitting and receiving data to and from an external device via a Network such as a LAN (Local Area Network). For example, the communication interface 205 is an interface supporting LAN connection. For example, the communication interface 205 receives print data from a client terminal through a network. When an error occurs in the printer 200, for example, the communication interface 205 transmits a signal notifying the error to the client terminal.

The motor drive circuit 207 controls the drive of the conveyance motor 206 in accordance with a signal from the processor 201. For example, the motor drive circuit 207 sends power or a control signal to the conveyance motor 206.

The conveyance motor 206 functions as a drive source of a conveyance mechanism that conveys a medium such as paper under the control of the motor drive circuit 207. When the conveyance motor 206 is driven, the conveyance mechanism conveys the medium. The transport mechanism transports the medium to the printing position of the inkjet head 100. The transport mechanism discharges the medium on which printing has been completed to the outside of the printer 200 from a discharge port not shown.

Here, the motor drive circuit 207 and the conveyance motor 206 constitute a conveyance mechanism that conveys the medium.

The pump drive circuit 209 controls the drive of the pump 208. When the pump 208 is driven, ink is supplied from the ink tank to the inkjet head 100.

The inkjet head 100 ejects ink droplets (liquid droplets) onto a medium based on print data. The inkjet head 100 includes a head driving circuit 101, a channel group 102, and the like.

Next, an ink jet head according to an embodiment will be described with reference to the drawings. In the embodiment, an inkjet head 100 (see fig. 2) of a sharing mode type is illustrated as an example. The following description will take an example of a case where the inkjet head 100 ejects ink onto paper. The medium from which the ink is ejected from the inkjet head 100 is not limited to a specific configuration.

Next, a configuration example of the ink jet head 100 will be described with reference to fig. 2 to 4. Fig. 2 is an exploded perspective view showing a part of the inkjet head 100. Fig. 3 is a cross-sectional view of the inkjet head 100. Fig. 4 is a longitudinal sectional view of the inkjet head 100.

The inkjet head 100 has a base substrate 9. The inkjet head 100 bonds the first piezoelectric component 1 to the upper surface of the base substrate 9, and bonds the second piezoelectric component 2 to the first piezoelectric component 1. As shown by arrows in fig. 3, the first piezoelectric member 1 and the second piezoelectric member 2 after bonding are polarized in directions opposite to each other in the plate thickness direction.

The base substrate 9 is formed using a material having a small dielectric constant and a small difference in thermal expansion coefficient between the first piezoelectric member 1 and the second piezoelectric member 2. As a material of the base substrate 9, for example, aluminum (a 1) is preferable₂0₃) Silicon nitride (Si)₃N₄) Silicon carbide (SiC), aluminum nitride (AlN), lead zirconate titanate (PZT), or the like. As the material of the first piezoelectric member 1 and the second piezoelectric member 2, lead zirconate titanate (PZT) or lithium niobate (LiNbO) can be used₃) Or lithium tantalate (LiTaO)₃) And the like.

In the ink jet head 100, a plurality of elongated grooves 3 are provided from the leading end side to the trailing end side of the first piezoelectric member 1 and the second piezoelectric member 2 that are bonded. The grooves 3 are fixed at intervals and parallel to each other. The grooves 3 are open at the front ends and inclined upward at the rear ends.

In the ink jet head 100, the electrodes 4 are provided on the side walls and the bottom surface of each of the grooves 3. The electrode 4 has a two-layer structure of nickel (Ni) and gold (Au). The electrode 4 is uniformly formed in each of the grooves 3 by, for example, a plating method. The method of forming the electrode 4 is not limited to the electroplating method. In addition, sputtering, vapor deposition, or the like may be used.

In the inkjet head 100, the lead electrodes 10 are provided from the rear ends of the respective grooves 3 toward the rear upper surface of the second piezoelectric member 2. The extraction electrode 10 extends from the electrode 4.

The inkjet head 100 includes a top plate 6 and an orifice plate 7. The top plate 6 blocks the upper part of each tank 3. The orifice plate 7 blocks the front end of each groove 3. In the inkjet head 100, a plurality of pressure chambers 15 are formed by the respective grooves 3 surrounded by the top plate 6 and the orifice plate 7. The pressure chamber 15 is filled with ink supplied from an ink tank. The pressure chambers 15 have a shape with a depth of 300 μm and a width of 80 μm, for example, and are arranged in parallel at an interval of 169 μm. Such a pressure chamber 15 is also referred to as an ink chamber.

The top plate 6 has a common ink chamber 5 at the inner rear side thereof. The orifice plate 7 includes nozzles 8 at positions facing the respective grooves 3. The nozzles 8 communicate with the opposite grooves 3, i.e. the pressure chambers 15. The nozzle 8 is tapered from the pressure chamber 15 side toward the ink discharge side on the opposite side. The nozzles 8 are formed by arranging nozzles corresponding to the adjacent three pressure chambers 15 as a set, and shifting them at a constant interval in the height direction of the groove 3 (the vertical direction of the paper surface in fig. 3).

When the pressure chamber 15 is filled with ink, a meniscus 20 of the ink is formed at the nozzle 8. The meniscus 20 is formed along the inner wall of the nozzle 8.

The first piezoelectric member 1 and the second piezoelectric member 2 constituting the partition wall of the pressure chamber 15 are sandwiched by the electrodes 4 provided in the pressure chambers 15, and form an actuator 16 for driving the pressure chambers 15.

In the inkjet head 100, the print substrate 11 on which the conductive pattern 13 is formed is bonded on the upper surface of the rear side of the base substrate 9. In the inkjet head 100, a driver IC12 having a head drive circuit 101 mounted thereon is mounted on the print substrate 11. The driver IC12 is connected to the conductive pattern 13. The conductive pattern 13 is bonded to each extraction electrode 10 by wire bonding using a wire 14.

The group of the pressure chamber 15, the electrode 4, and the nozzle 8 included in the inkjet head 100 is referred to as a channel. That is, the inkjet head 100 has channels ch.1, ch.2, …, ch.n corresponding to the number N of the grooves 3.

Next, the head drive circuit 101 will be explained.

Fig. 5 is a block diagram for explaining a configuration example of the head drive circuit 101. As described above, the head drive circuit 101 is disposed in the driver IC 12.

The head driving circuit 101 drives the channel group 102 of the inkjet head 100 based on the print data.

The channel group 102 is composed of a plurality of channels (ch.1, ch.2, …, ch.n) including the pressure chamber 15, the actuator 16, the electrode 4, the nozzle 8, and the like. That is, the channel group 102 ejects ink droplets by the operation of the respective pressure chambers 15 expanded and contracted by the actuator 16 based on a control signal from the head drive circuit 101.

As shown in fig. 5, the head drive circuit 101 includes a pattern generator 301, a frequency setting unit 302, a drive signal generation unit 303, a switch circuit 304, and the like.

The pattern generator 301 generates various waveform patterns using a waveform pattern of an expansion pulse for expanding the volume of the pressure chamber 15, a release period for releasing the volume of the pressure chamber 15, a waveform pattern of a contraction pulse for contracting the volume of the pressure chamber 15, and the like.

The pattern generator 301 generates a waveform pattern of ejection pulses that eject one ink droplet. The period of the ejection pulse is a period for ejecting one ink droplet, that is, a so-called one-droplet cycle.

The ejection pulse will be described later in detail.

The frequency setting unit 302 sets the driving frequency of the inkjet head 100. The drive frequency is the frequency of the drive pulse generated by the drive signal generation unit 303. The head drive circuit 101 operates in accordance with the drive pulse.

The drive signal generation unit 303 generates a pulse corresponding to each channel based on the waveform pattern generated by the pattern generator 301 based on the print data input from the bus and the drive frequency set by the frequency setting unit 302. A pulse corresponding to each channel is output from the drive signal generation section 303 to the switch circuit 304.

The switching circuit 304 switches the voltage applied to the electrode 4 of each channel in accordance with the pulse corresponding to each channel output from the drive signal generating unit 303. That is, the switching circuit 304 applies a voltage to the actuator 16 of each channel based on the energization time of the extension pulse or the like set by the pattern generator 301.

The switching circuit 304 expands or contracts the volume of the pressure chamber 15 of each channel by switching the voltage, and ejects ink droplets corresponding to the number of gradations from the nozzles 8 of each channel.

Next, an operation example of the ink jet head 100 configured as described above will be described with reference to fig. 6 to 9.

Fig. 6 shows the state of the pressure chamber 15b during release. Here, the partition wall 16a and the partition wall 16b constitute the actuator 16. As shown in fig. 6, the head drive circuit 101 sets the potential of the electrode 4 of each of the partition walls 16a and 16b provided in the pressure chamber 15b and the two adjacent pressure chambers 15a and 15c adjacent to the pressure chamber 15b to the ground potential GND. In this state, neither the partition wall 16a sandwiched between the pressure chambers 15a and 15b nor the partition wall 16b sandwiched between the pressure chambers 15b and 15c is deformed.

Fig. 7 shows an example of a state in which the head driving circuit 101 applies an extension pulse to the actuator 16 of the pressure chamber 15 b. As shown in fig. 7, the head drive circuit 101 applies a voltage-V of negative polarity to the electrode 4 of the central pressure chamber 15b, and applies a voltage + V to the electrodes 4 of the two adjacent pressure chambers 15a and 15c of the pressure chamber 15 b. In this state, an electric field of a voltage 2V acts on each of the partition walls 16a and 16b in a direction orthogonal to the polarization direction of the first piezoelectric member 1 and the second piezoelectric member 2. By this action, each of the partition walls 16a and 16b is deformed outward to expand the volume of the pressure chamber 15 b.

Fig. 8 shows an example of a state in which the head drive circuit 101 applies the first contraction pulse to the actuator 16 of the pressure chamber 15 b. As shown in fig. 8, the head drive circuit 101 sets the electrode 4 of the central pressure chamber 15b to the ground potential GND, and applies a voltage-V to the electrodes 4 of the two adjacent pressure chambers 15a and 15 c. In this state, an electric field of a voltage V acts on each of the partition walls 16a and 16b in a direction opposite to the state of fig. 7. By this action, the partition walls 16a and 16b are deformed inward to contract the volume of the pressure chamber 15 b. The first contraction pulse contracts the pressure chamber 15b to a first volume that is less than the original volume.

Note that, as the first contraction pulse, the head drive circuit 101 may apply the voltage + V to the electrode 4 of the central pressure chamber 15b so that the electrodes 4 of the two adjacent pressure chambers 15a and 15c are at the ground potential GND.

Fig. 9 shows an example of a state in which the head drive circuit 101 applies the second contraction pulse to the actuator 16 of the pressure chamber 15 b. As shown in fig. 9, the head drive circuit 101 applies a positive voltage + V to the electrode 4 of the central pressure chamber 15b, and applies a voltage-V to the electrodes 4 of the two adjacent pressure chambers 15a and 15 c. In this state, an electric field of a voltage 2V acts on each of the partition walls 16a and 16b in a direction opposite to the state of fig. 7. By this action, the partition walls 16a and 16b are deformed inward to contract the volume of the pressure chamber 15 b. The second contraction pulse contracts the pressure chamber 15b to a second volume that is less than the first volume.

When the volume of the pressure chamber 15b is expanded or contracted, pressure vibration is generated in the pressure chamber 15 b. By this pressure oscillation, the pressure in the pressure chamber 15b rises, and ink droplets are ejected from the nozzles 8 communicating with the pressure chamber 15 b.

In this way, the partition walls 16a and 16b partitioning the pressure chambers 15a, 15b, and 15c serve as the actuators 16 for applying pressure vibration to the inside of the pressure chamber 15b, and the pressure chamber 15b has the partition walls 16a and 16b as wall surfaces. That is, the pressure chamber 15 is expanded or contracted by the action of the actuator 16.

Further, each pressure chamber 15 shares an actuator 16 (partition wall) with the adjacent pressure chamber 15. Therefore, the head drive circuit 101 cannot drive the pressure chambers 15 individually. The head drive circuit 101 drives the pressure chambers 15 by dividing them into (n +1) groups every n (n is an integer of 2 or more). In the present embodiment, a case of so-called three-division driving in which the head drive circuit 101 divides each pressure chamber 15 into three groups every two is illustrated. Note that the three-division drive is only an example, and may be a four-division drive or a five-division drive.

The head drive circuit 101 ejects ink droplets from each channel of the channel group 102 based on a signal from the processor 201. That is, the head drive circuit 101 applies an ejection pulse to the actuators 16 constituting each (a part or all) of the channels of the channel group 102 based on a signal from the processor 201.

Next, an example of the ejection pulse applied to the actuator 16 of the channel group 102 by the head driving circuit 101 will be described.

The head drive circuit 101 applies an ejection pulse for ejecting a predetermined amount of ink droplets from the nozzles 8 to the actuator 16.

Fig. 10 shows an example of the configuration of the ejection pulse. In fig. 10, a curve 51 shows the voltage applied to the actuator 16 by the head drive circuit 101. The curve 52 shows the pressure generated in the pressure chamber 15. Curve 53 shows the flow rate of meniscus 20. In the curve 53, a negative value indicates that the meniscus 20 advances to the inside of the pressure chamber 15, and a positive value indicates that the meniscus 20 advances to the outside of the pressure chamber. The horizontal axis represents time.

As shown in fig. 10, the ejection pulse is composed of an expansion pulse, a first contraction pulse, and a second contraction pulse.

Further, while the head drive circuit 101 applies the ejection pulse to the actuator 16, the flow rate is zero three times. In the example shown in fig. 10, at time point 81, the flow rate is zero for the first time. At time point 81, the flow rate changes from negative to zero and to positive. That is, at the time 81, the meniscus 20 is changed from a state of advancing to the inside of the pressure chamber 15 to a state of advancing to the outside.

Further, at time point 82, the flow rate is zero a second time. At time 82, the flow rate changes from positive to zero and to negative. That is, at the time 82, the meniscus 20 changes from a state of advancing to the outside of the pressure chamber 15 to a state of advancing to the inside.

Further, at a time point 83 (first time point), the flow rate is zero for the third time. At time point 83, the flow rate changes from negative to zero and to positive. That is, at the time point 83, the meniscus 20 is changed from a state of advancing to the inside of the pressure chamber 15 to a state of advancing to the outside.

First, the head drive circuit 101 applies an expansion pulse to the actuator 16. Here, the head drive circuit 101 applies an extension pulse having a width AL (half of the natural vibration period of the pressure chamber 15). Further, as described above, the peak value (voltage) of the extension pulse is 2V. Here, V is a prescribed value.

By the expansion pulse, the pressure chamber 15 expands. That is, the pressure chamber is in the state of fig. 7. In this state, the pressure of the pressure chamber 15 is reduced, and ink is supplied from the common ink chamber 5 to the pressure chamber 15.

Further, the flow rate decreases from the start time point of the expansion pulse and rises bottoming. The flow rate continues to rise to zero at time 81.

The head drive circuit 101 applies a first contraction pulse after applying the expansion pulse. Here, the head drive circuit 101 applies a first contraction pulse having a width of AL. Further, as described above, the peak value (voltage) of the first contraction pulse is V.

By means of the first contraction pulse, the pressure chamber 15 is contracted to a first volume. That is, the pressure chamber is in the state of fig. 8. In this state, the pressure of the pressure chamber 15 rises. The velocity of the meniscus 20 formed at the nozzle 8 exceeds the threshold for ejecting ink droplets by the pressure rise in the pressure chamber 15. When the speed of the meniscus 20 exceeds the threshold value, the ejection of ink droplets from the nozzles 8 of the pressure chambers 15 is started.

The flow rate drops after the peak.

The head drive circuit 101 applies a second contraction pulse after applying the first contraction pulse. Here, the head drive circuit 101 applies the second contraction pulse having a width including the time point 83. That is, the second contraction pulse includes a point in time at which the flow rate becomes zero for the third time. The width of the second contraction pulse is greater than AL. Further, as described above, the peak value (voltage) of the second contraction pulse is 2V.

By means of the second contraction pulse, the pressure chamber 15 is contracted to a second volume. That is, the pressure chamber is in the state of fig. 9. In this state, the flow rate continues to decrease and passes through the time point 82. The flow rate rises again after bottoming. The flow rate becomes zero at time 83 and then rises.

The second contraction pulse ends before the flow velocity approaches the peak. That is, the period between time point 83 and the end time point of the second contraction pulse is equal to or less than half of AL (one-fourth of the natural vibration period).

By the second contraction pulse, the pressure chamber 15 continues to contract even after the time point 83, and the vibration of the flow rate and the pressure continues even after the head drive circuit 101 applies the ejection pulse.

Next, another example of the ejection pulse applied to the actuator 16 of the channel group 102 by the head driving circuit 101 will be described.

Fig. 11 shows another configuration example of the ejection pulse. In fig. 11, a curve 61 shows the voltage applied to the actuator 16 by the head drive circuit 101. The curve 62 shows the pressure generated in the pressure chamber 15. Curve 63 shows the flow rate of meniscus 20. The horizontal axis represents time.

As shown in fig. 11, the ejection pulse is composed of an expansion pulse, a first contraction pulse, and a second contraction pulse.

Further, while the head drive circuit 101 applies the ejection pulse to the actuator 16, the flow rate is zero three times. In the example shown in fig. 11, the flow rate is zero for the first time at time point 91. At time point 91, the flow rate changes from negative to zero and to positive. That is, at the time point 91, the meniscus 20 is changed from a state of advancing to the inside of the pressure chamber 15 to a state of advancing to the outside.

Further, at a time point 92 (second time point), the flow rate is zero for the second time. At time 92, the flow rate changes from positive to zero and to negative. That is, at the time point 92, the meniscus 20 changes from a state of advancing to the outside of the pressure chamber 15 to a state of advancing to the inside.

Further, at a time point 93 (first time point), the flow rate is zero for the third time. At time point 93, the flow rate changes from negative to zero and to positive. That is, at the time point 93, the meniscus 20 is changed from a state of advancing to the inside of the pressure chamber 15 to a state of advancing to the outside.

First, the head drive circuit 101 applies an expansion pulse to the actuator 16. Here, the head drive circuit 101 applies an extension pulse having a width of AL. Further, as described above, the peak value (voltage) of the extension pulse is 2V.

By the expansion pulse, the pressure chamber 15 expands. That is, the pressure chamber is in the state of fig. 7. In this state, the pressure of the pressure chamber 15 is reduced, and ink is supplied from the common ink chamber 5 to the pressure chamber 15.

Further, the flow rate decreases from the start time point of the expansion pulse and rises bottoming. The flow rate continues to rise to zero at time point 91.

The head drive circuit 101 applies a first contraction pulse after applying the expansion pulse. Here, the head drive circuit 101 applies the first contraction pulse having a width including the time point 92. I.e. the first contraction pulse comprises the point in time when the flow rate becomes zero for the second time. The width of the first contraction pulse is greater than AL. Further, as described above, the peak value (voltage) of the first contraction pulse is V.

By means of the first contraction pulse, the pressure chamber 15 is contracted to a first volume. That is, the pressure chamber is in the state of fig. 8. In this state, the pressure of the pressure chamber 15 rises. The velocity of the meniscus 20 formed at the nozzle 8 exceeds the threshold for ejecting ink droplets by the pressure rise in the pressure chamber 15. When the speed of the meniscus 20 exceeds the threshold value, the ejection of ink droplets from the nozzles 8 of the pressure chambers 15 is started.

The flow rate decreases after the peak. The flow rate continues to decrease and passes through time point 92. The flow rate reached the bottom and then increased again.

The head drive circuit 101 applies a second contraction pulse after applying the first contraction pulse. Here, the head driving circuit 101 applies the second contraction pulse having a width including the time point 93. The second contraction pulse includes the point in time when the flow rate is third to zero. The width of the second contraction pulse is AL. Further, as described above, the peak value (voltage) of the second contraction pulse is 2V.

By means of the second contraction pulse, the pressure chamber 15 is contracted to a second volume. That is, the pressure chamber is in the state of fig. 9. In this state, the flow rate continues to decrease and becomes zero at time point 93. Thereafter, the flow rate continues to rise.

The second contraction pulse ends before the pressure in the pressure chamber 15 peaks. That is, the period between time point 93 and the end time point of the second contraction pulse is equal to or less than half AL.

By the second contraction pulse, the pressure chamber 15 continues to contract even after the time point 83, and the vibration of the flow rate and the pressure continues even after the head drive circuit 101 applies the ejection pulse.

Note that the inkjet head may be a circulation type head.

It is noted that the peak value of the second contraction pulse may not be twice as large as the peak value of the first contraction pulse. Further, the peak value of the extension pulse may be different from the peak value of the second contraction pulse.

The ink jet head configured as described above applies an ejection pulse including a second contraction pulse formed to include a time point at which the flow velocity of the meniscus transitions from negative to positive to the actuator. As a result, the inkjet head can maintain the vibration of the flow velocity even after the application of the ejection pulse. Therefore, the inkjet head can press out ink droplets extending in the flying direction from the nozzles. Thus, the ink jet head can prevent the ink droplets from flying in an extended state. Therefore, the ink jet head can prevent the ink jet head from being stained or blurred, and prevent the print quality from being degraded.

Further, the inkjet head applies a first contraction pulse and a second contraction pulse to the actuator including a point in time at which the flow rate of the meniscus is changed from positive to negative. As shown in fig. 11, the inkjet head can increase the vibration of the flow velocity after applying the ejection pulse. This makes it possible to prevent the ink jet head from being clogged or blurred more effectively.

Further, in the inkjet head, the second contraction pulse does not include a peak of the flow velocity. As a result, the ink jet head prevents the vibration of the flow velocity from becoming excessive. Therefore, the inkjet head can prevent unnecessary ink from being ejected after the ejection pulse is applied.

Several embodiments of the present invention have been described, but these embodiments are merely examples and are not intended to limit the scope of the present invention. These new embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications are included in the spirit of the scope of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.