JP2022007186A - Liquid discharge head and printer - Google Patents

Abstract

To provide a liquid discharge head and a printer capable of preventing the degradation of print quality.SOLUTION: A liquid discharge head 100 comprises an actuator, and a control portion. The actuator expands and contracts a pressure chamber communicating to a nozzle discharging ink. The control portion applies an expansion pulse for expanding the pressure chamber, then applies a first contraction pulse for contracting the pressure chamber to a first volume, and applies a second contraction pulse for contracting the volume of the pressure chamber to a second volume smaller than the first volume. A width of the second contraction pulse includes a first time point that changes from the first contraction pulse to the second contraction pulse, and then changes from a state in which a meniscus formed at the nozzle advances into the pressure chamber to a state in which the meniscus advances to the outside of the pressure chamber.SELECTED DRAWING: Figure 1

Description

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

Some inkjet heads apply an ejection pulse to an actuator that contracts and expands a pressure chamber to eject ink droplets from the pressure chamber onto a medium such as paper. The ink droplets ejected in this way may fly in a state of being extended in the flight direction. As a result, satellite dots or mist may be generated on the medium.

Therefore, conventionally, the print quality of the inkjet head may deteriorate.

Japanese Unexamined Patent Publication No. 2017-105131

In order to solve the above problems, a liquid ejection head and a printer capable of preventing deterioration of print quality are provided.

According to the embodiment, the liquid discharge 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 an expansion pulse that expands the pressure chamber to the actuator, then applies a first contraction pulse that contracts the pressure chamber to the first volume, and reduces the volume of the pressure chamber to the first volume. A second contraction pulse is applied that contracts to a second volume that is smaller than the volume. The width of the second contraction pulse changes from the first contraction pulse to the second contraction pulse, and then the meniscus formed in the nozzle advances into the pressure chamber. Includes a first time point when the condition progresses to the outside of the pressure chamber.

FIG. 1 is a block diagram showing a configuration example of a printer according to an embodiment. FIG. 2 shows an example of a perspective view of the inkjet head according to the embodiment. FIG. 3 is a cross-sectional view of the inkjet head according to the embodiment. FIG. 4 is a vertical cross-sectional view of the inkjet head according to the embodiment. FIG. 5 is a block diagram showing a configuration example of the head drive circuit according to the embodiment. FIG. 6 is a diagram showing an operation example of the inkjet head according to the embodiment. FIG. 7 is a diagram showing an operation example of the inkjet head according to the embodiment. FIG. 8 is a diagram showing an operation example of the inkjet head according to the embodiment. FIG. 9 is a diagram showing an operation example 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.

Hereinafter, the printer according to the embodiment will be described with reference to the drawings.

The printer according to the embodiment uses an inkjet head to form an image on a medium such as paper. The printer ejects the ink in the pressure chamber of the inkjet head onto the medium to form an image on the medium. The printer is, for example, an office printer, a bar code printer, a POS printer, an industrial printer, a 3D printer, or the like. The medium on which the printer forms an image is not limited to a specific configuration. The inkjet head included in the printer according to the embodiment is an example of a liquid ejection head, and the ink is an example of a liquid. For example, the liquid discharge head may be one that discharges a chemical solution or the like.

FIG. 1 is a block diagram showing a configuration example of the printer 200.
As shown in FIG. 1, the printer 200 includes a processor 201, ROM 202, RAM 203, an operation panel 204, a communication interface 205, a transfer motor 206, a motor drive circuit 207, a pump 208, a pump drive circuit 209, an 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 line 211 such as an address bus and a data bus. The processor 201 is connected to the ROM 202, the RAM 203, the operation panel 204, the communication interface 205, the motor drive circuit 207, the pump drive circuit 209, and the head drive circuit 101 via the bus line 211 directly or via an input / output circuit. The motor drive circuit 207 is connected to the transfer motor 206. Further, the pump drive circuit 209 is connected to the pump 208. Further, the head drive circuit 101 is connected to the channel group 102.

In addition to the configuration shown in FIG. 1, the printer 200 may further include a configuration as required, or a specific configuration may be excluded from the printer 200.

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

It should be noted that some of the various functions realized by the processor 201 executing the program may be realized by the hardware circuit. In this case, the processor 201 controls the functions performed by the hardware circuit.

The ROM 202 is a non-volatile memory in which a control program, control data, and the like are stored in advance. The control program and control data stored in the ROM 202 are preliminarily incorporated according to the specifications of the printer 200. For example, the ROM 202 stores an operating system, an application program, and the like.

The RAM 203 is a volatile memory. The RAM 203 temporarily stores data and the like being processed by the processor 201. The RAM 203 stores various application programs and the like based on the instructions from the processor 201. Further, the RAM 203 may store data necessary for executing the application program, an execution result of the application program, and the like. Further, the RAM 203 may function as an image memory in which print data is expanded.

The operation panel 204 is an interface that receives input of instructions from the operator and displays various information to the operator. The operation panel 204 includes an operation unit that accepts input of an instruction and a display unit that displays information.

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

The operation panel 204 displays various information as an operation of the display unit based on the control of the processor 201. For example, the operation panel 204 displays the status of the printer 200 and the like. For example, the display unit is composed of a liquid crystal monitor.
The operation unit may be composed of a touch panel. In this case, the display unit may be integrally formed with the touch panel as the operation unit.

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 that supports a LAN connection. For example, the communication interface 205 receives print data from a client terminal via a network. For example, when an error occurs in the printer 200, the communication interface 205 transmits a signal notifying the error to the client terminal.

The motor drive circuit 207 controls the drive of the transfer motor 206 according to the signal from the processor 201. For example, the motor drive circuit 207 transmits a power or control signal to the transfer motor 206.

The transport motor 206 functions as a drive source for a transport mechanism that transports a medium such as paper based on the control of the motor drive circuit 207. When the transport motor 206 is driven, the transport mechanism transports the medium. The transport mechanism transports the medium to the printing position by the inkjet head 100. The transport mechanism discharges the printed medium to the outside of the printer 200 from an ejection port (not shown).
Here, the motor drive circuit 207 and the transfer motor 206 constitute a transfer mechanism for transporting the medium.

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

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

Hereinafter, the inkjet head according to the embodiment will be described with reference to the drawings. In the embodiment, a share mode type inkjet head 100 (see FIG. 2) is exemplified. The inkjet head 100 will be described as ejecting ink onto paper. The medium for ejecting ink by the inkjet head 100 is not limited to a specific configuration.

Next, a configuration example of the inkjet head 100 will be described with reference to FIGS. 2 to 4. FIG. 2 is a perspective view showing a part of the inkjet head 100 in an exploded manner. FIG. 3 is a cross-sectional view of the inkjet head 100. FIG. 4 is a vertical sectional view of the inkjet head 100.

The inkjet head 100 has a base substrate 9. In the inkjet head 100, the first piezoelectric member 1 is bonded to the upper surface of the base substrate 9, and the second piezoelectric member 2 is bonded onto the first piezoelectric member 1. As shown by the arrow in FIG. 3, the joined first piezoelectric member 1 and the second piezoelectric member 2 are polarized in opposite directions along the plate thickness direction.

The base substrate 9 is formed by 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 the material of the base substrate 9, for example, alumina (Al203), silicon nitride (Si3N4), silicon carbide (SiC), aluminum nitride (AlN), lead zirconate titanate (PZT) and the like are preferable. As the material of the first piezoelectric member 1 and the second piezoelectric member 2, lead zirconate titanate (PZT), lithium niobate (LiNbO3), lithium tantalate (LiTaO3) and the like are used.

The inkjet head 100 is provided with a large number of long grooves 3 from the front end side to the rear end side of the joined first piezoelectric member 1 and the second piezoelectric member 2. Each groove 3 has a constant spacing and is parallel. The tip of each groove 3 is open and the rear end is inclined upward.

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

The inkjet head 100 is provided with a drawer electrode 10 from the rear end of each groove 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 closes the upper part of each groove 3. The orifice plate 7 closes the tip of each groove 3. The inkjet head 100 forms a plurality of pressure chambers 15 by each groove 3 surrounded by the top plate 6 and the orifice plate 7. The pressure chamber 15 is filled with ink supplied from the ink tank. The pressure chambers 15 have a shape having, for example, a depth of 300 μm and a width of 80 μm, and are arranged in parallel at a pitch of 169 μm. Such a pressure chamber 15 is also referred to as an ink chamber.

The top plate 6 is provided with a common ink chamber 5 inside and behind the top plate 6. The orifice plate 7 is provided with a nozzle 8 at a position facing each groove 3. The nozzle 8 communicates with the facing groove 3, that is, the pressure chamber 15. The nozzle 8 has a tapered shape from the pressure chamber 15 side toward the ink ejection side on the opposite side. The nozzles 8 correspond to three adjacent pressure chambers 15 as one set, and are formed so as to be displaced at regular intervals in the height direction of the groove 3 (vertical direction of the paper surface in FIG. 3).

When the pressure chamber 15 is filled with ink, the meniscus 20 of the ink is formed in 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 each pressure chamber 15 to form an actuator 16 for driving the pressure chamber 15.

The inkjet head 100 joins the printed circuit board 11 on which the conductive pattern 13 is formed to the upper surface on the rear side of the base substrate 9. The inkjet head 100 mounts a drive IC 12 on which a head drive circuit 101 is mounted on a printed circuit board 11. The drive IC 12 is connected to the conductive pattern 13. The conductive pattern 13 is bonded to each of the leader electrodes 10 by wire bonding with a conducting wire 14.

The set of the pressure chamber 15, the electrode 4, and the nozzle 8 of the inkjet head 100 is referred to as a channel. That is, the inkjet head 100 has channels ch.1, ch.2, ..., Ch.N by the number N of the grooves 3.

Next, the head drive circuit 101 will be described.
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 arranged in the drive IC 12.

The head drive 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 a pressure chamber 15, an actuator 16, an electrode 4, a nozzle 8, and the like. That is, the channel group 102 ejects ink droplets by the operation of each pressure chamber 15 in which the actuator 16 expands and contracts based on the 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 uses an expansion pulse waveform pattern that expands the volume of the pressure chamber 15, a release period that releases the volume of the pressure chamber 15, and a contraction pulse waveform pattern that contracts the volume of the pressure chamber 15. , Generate various waveform patterns.

The pattern generator 301 generates a waveform pattern of an ejection pulse that ejects one ink droplet. The period of the ejection pulse is a section for ejecting one ink droplet, a so-called one drop cycle.
The discharge pulse will be described in detail later.

The frequency setting unit 302 sets the drive 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 according to the drive pulse.

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

The switch circuit 304 switches the voltage applied to the electrode 4 of each channel according to the pulse for each channel output from the drive signal generation unit 303. That is, the switch circuit 304 applies a voltage to the actuator 16 of each channel based on the energization time of the extended pulse or the like set by the pattern generator 301.

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

Next, an operation example of the inkjet head 100 configured as described above will be described with reference to FIGS. 6 to 9.
FIG. 6 shows the state of the pressure chamber 15b during the release period. Here, the partition wall 16a and the partition wall 16b constitute the actuator 16. As shown in FIG. 6, the head drive circuit 101 determines the potential of the electrodes 4 arranged in the partition walls 16a and 16b of the pressure chamber 15b and the adjacent pressure chambers 15a and 15c adjacent to the pressure chamber 15b, respectively. Is also the ground potential GND. In this state, the partition wall 16a sandwiched between the pressure chamber 15a and the pressure chamber 15b and the partition wall 16b sandwiched between the pressure chamber 15b and the pressure chamber 15c do not cause any distortion.

FIG. 7 shows an example of a state in which the head drive circuit 101 applies an expansion pulse to the actuator 16 of the pressure chamber 15b. As shown in FIG. 7, the head drive circuit 101 applies a negative voltage −V to the electrode 4 of the central pressure chamber 15b, and applies a voltage + V to the electrodes 4 of the pressure chambers 15a and 15c on both sides of the pressure chamber 15b. Apply. In this state, an electric field having a voltage of 2 V 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 so as to expand the volume of the pressure chamber 15b.

FIG. 8 shows an example of a state in which the head drive circuit 101 applies a first contraction pulse to the actuator 16 of the pressure chamber 15b. As shown in FIG. 8, in the head drive circuit 101, the electrode 4 of the central pressure chamber 15b is set to the ground potential GND, and a voltage −V is applied to the electrodes 4 of the pressure chambers 15a and 15c on both sides thereof. In this state, an electric field of voltage V acts on each of the partition walls 16a and 16b in the direction opposite to the state of FIG. 7. By this action, each of the partition walls 16a and 16b is deformed inward so as to contract the volume of the pressure chamber 15b. The first contraction pulse contracts the pressure chamber 15b to a first volume smaller than the original volume.

The head drive circuit 101 may apply a voltage + V to the electrode 4 of the central pressure chamber 15b as the first contraction pulse, and may use the electrodes 4 of the pressure chambers 15a and 15c on both sides as the ground potential GND.

FIG. 9 shows an example of a state in which the head drive circuit 101 applies a second contraction pulse to the actuator 16 of the pressure chamber 15b. 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 adjacent pressure chambers 15a and 15c. In this state, an electric field having a voltage of 2V acts on each of the partition walls 16a and 16b in the direction opposite to the state shown in FIG. By this action, each of the partition walls 16a and 16b is deformed inward so as to contract the volume of the pressure chamber 15b. The second contraction pulse causes the pressure chamber 15b to contract to a second volume smaller than the first volume.

When the volume of the pressure chamber 15b is expanded or contracted, pressure vibration is generated in the pressure chamber 15b. Due to this pressure vibration, the pressure in the pressure chamber 15b increases, and ink droplets are ejected from the nozzle 8 communicating with the pressure chamber 15b.

As described above, the partition walls 16a and 16b separating the pressure chambers 15a, 15b and 15c are actuators 16 for applying pressure vibration to the inside of the pressure chamber 15b having the partition walls 16a and 16b as the wall surface. That is, the pressure chamber 15 is expanded or contracted by the operation of the actuator 16.

Further, each pressure chamber 15 shares an actuator 16 (partition wall) with an adjacent pressure chamber 15. Therefore, the head drive circuit 101 cannot drive each pressure chamber 15 individually. The head drive circuit 101 divides each pressure chamber 15 into (n + 1) groups every n (n is an integer of 2 or more) and drives the pressure chambers 15. In the present embodiment, the case of so-called three-division drive in which the head drive circuit 101 divides each pressure chamber 15 into three sets every two and drives them is illustrated. The 3-split drive is just an example, and may be a 4-split drive, a 5-split drive, or the like.

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

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

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

FIG. 10 shows a configuration example of the discharge pulse. In FIG. 10, graph 51 shows the voltage applied to the actuator 16 by the head drive circuit 101. Graph 52 shows the pressure generated in the pressure chamber 15. Graph 53 shows the flow velocity of the meniscus 20. In graph 53, a negative value indicates that the meniscus 20 is traveling inside the pressure chamber 15, and a positive value indicates that the meniscus 20 is traveling outside the pressure chamber. The horizontal axis indicates time.

As shown in FIG. 10, the discharge 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 discharge pulse to the actuator 16, the flow velocity becomes 0 three times. In the example shown in FIG. 10, at time point 81, the flow velocity is initially 0. At time point 81, the flow velocity changes from negative to 0 and turns positive. That is, at the time point 81, the meniscus 20 changes from a state of progressing inside the pressure chamber 15 to a state of progressing outside.

Further, at the time point 82, the flow velocity becomes 0 for the second time. At time point 82, the flow velocity changes from positive to 0 and turns negative. That is, at the time point 82, the meniscus 20 changes from a state of progressing to the outside of the pressure chamber 15 to a state of progressing to the inside.

Further, at the time point 83 (first time point), the flow velocity becomes 0 at the third time. At time point 83, the flow velocity changes from negative to 0 and turns positive. That is, at time point 83, the meniscus 20 changes from a state of progressing inside the pressure chamber 15 to a state of progressing outside.

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

The pressure chamber 15 is expanded by the expansion pulse. That is, the pressure chamber is in the state shown in FIG. In this state, the pressure in the pressure chamber 15 drops, and ink is supplied to the pressure chamber 15 from the common ink chamber 5.

In addition, the flow velocity drops from the start of the expansion pulse, reaches the bottom, and rises. The flow velocity continues to rise and becomes 0 at the time point 81.

The head drive circuit 101 applies a first contraction pulse after applying an 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.

The first contraction pulse causes the pressure chamber 15 to contract to the first volume. That is, the pressure chamber is in the state shown in FIG. In this state, the pressure in the pressure chamber 15 rises. As the pressure in the pressure chamber 15 rises, the speed of the meniscus 20 formed in the nozzle 8 exceeds the threshold value at which ink droplets are ejected. When the speed of the meniscus 20 exceeds the threshold value, ink droplets are ejected from the nozzle 8 of the pressure chamber 15.
The flow velocity reaches its peak and decreases.

The head drive circuit 101 applies a second contraction pulse after applying the first contraction pulse. Here, the head drive circuit 101 applies a second contraction pulse having a width including time point 83. That is, the second contraction pulse includes the time when the flow velocity becomes 0 for the third time. The width of the second contraction pulse is longer than AL. Further, as described above, the peak value (voltage) of the second contraction pulse is 2V.

The second contraction pulse causes the pressure chamber 15 to contract to a second volume. That is, the pressure chamber is in the state shown in FIG. In this state, the flow velocity continues to decrease and passes through the time point 82. The flow velocity reaches the bottom and rises again. The flow velocity becomes 0 at time point 83 and then increases.

The second contraction pulse ends before the flow velocity peaks. That is, the period between the time point 83 and the end time point of the second contraction pulse is less than half of AL (a quarter of the natural vibration cycle).

Since the pressure chamber 15 continues to contract after the time point 83 due to the second contraction pulse, the vibration of the flow velocity and the pressure continues even after the head drive circuit 101 applies the discharge pulse.

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

FIG. 11 shows another configuration example of the discharge pulse. In FIG. 11, graph 61 shows the voltage applied to the actuator 16 by the head drive circuit 101. Graph 62 shows the pressure generated in the pressure chamber 15. Graph 63 shows the flow velocity of the meniscus 20. The horizontal axis indicates time.

As shown in FIG. 11, the discharge 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 discharge pulse to the actuator 16, the flow velocity becomes 0 three times. In the example shown in FIG. 11, at time point 91, the flow velocity is initially 0. At time point 91, the flow velocity changes from minus to zero and turns to plus. That is, at time point 91, the meniscus 20 changes from a state of progressing inside the pressure chamber 15 to a state of progressing outside.

Further, at the time point 92 (second time point), the flow velocity becomes 0 for the second time. At time point 92, the flow velocity changes from positive to 0 and turns negative. That is, at time point 92, the meniscus 20 changes from a state of progressing to the outside of the pressure chamber 15 to a state of progressing to the inside.

Further, at the time point 93 (first time point), the flow velocity becomes 0 at the third time. At time point 93, the flow velocity changes from negative to 0 and turns positive. That is, at time point 93, the meniscus 20 changes from a state of progressing inside the pressure chamber 15 to a state of progressing outside.

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

The pressure chamber 15 is expanded by the expansion pulse. That is, the pressure chamber is in the state shown in FIG. In this state, the pressure in the pressure chamber 15 drops, and ink is supplied to the pressure chamber 15 from the common ink chamber 5.

In addition, the flow velocity drops from the start of the expansion pulse, reaches the bottom, and rises. The flow velocity continues to rise and becomes 0 at the time point 91.

The head drive circuit 101 applies a first contraction pulse after applying an expansion pulse. Here, the head drive circuit 101 applies a first contraction pulse having a width including time point 92. That is, the first contraction pulse includes the time when the flow velocity becomes 0 for the second time. The width of the first contraction pulse is longer than AL. Further, as described above, the peak value (voltage) of the first contraction pulse is V.

The first contraction pulse causes the pressure chamber 15 to contract to the first volume. That is, the pressure chamber is in the state shown in FIG. In this state, the pressure in the pressure chamber 15 rises. As the pressure in the pressure chamber 15 rises, the speed of the meniscus 20 formed in the nozzle 8 exceeds the threshold value at which ink droplets are ejected. When the speed of the meniscus 20 exceeds the ejection threshold, ink droplets are ejected from the nozzle 8 of the pressure chamber 15.
The flow velocity reaches its peak and decreases. The flow velocity continues to decrease and passes through time point 92. The flow velocity reaches the bottom and rises again.

The head drive circuit 101 applies a second contraction pulse after applying the first contraction pulse. Here, the head drive circuit 101 applies a second contraction pulse having a width including time point 93. The second contraction pulse includes the time when the flow velocity becomes 0 for the third time. The width of the second contraction pulse is AL. Further, as described above, the peak value (voltage) of the second contraction pulse is 2V.

The second contraction pulse causes the pressure chamber 15 to contract to a second volume. That is, the pressure chamber is in the state shown in FIG. In this state, the flow velocity continues to rise and becomes 0 at the time point 93. After that, the flow velocity 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 less than half of AL.

Since the pressure chamber 15 continues to contract after the time point 83 due to the second contraction pulse, the vibration of the flow velocity and the pressure continues even after the head drive circuit 101 applies the discharge pulse.

The inkjet head may be a circulation type head.
The peak value of the second contraction pulse does not have to be twice the peak value of the first contraction pulse. Further, the peak value of the expansion pulse does not have to be the same as the peak value of the second contraction pulse.

The inkjet head configured as described above applies a discharge pulse including a second contraction pulse formed so as to include a time point at which the flow velocity of the meniscus changes from negative to positive to the actuator. As a result, the inkjet head can maintain the vibration of the flow velocity even after applying the ejection pulse. Therefore, the inkjet head can push out the ink droplets extending in the flight direction from the nozzles. Therefore, the inkjet head can prevent the ink droplets from flying in a stretched state. Therefore, the inkjet head can prevent satellites, mist, and the like to prevent deterioration of print quality.

Further, the inkjet head applies an ejection pulse including a first contraction pulse and a second contraction pulse formed so as to include a time point when the flow velocity of the meniscus changes from plus to minus to the actuator. As shown in FIG. 11, the inkjet head can increase the vibration of the flow velocity after applying the ejection pulse. Therefore, the inkjet head can more effectively prevent satellites, mists, and the like.

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

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 embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... 1st piezoelectric member, 2 ... 2nd piezoelectric member, 3 ... groove, 4 ... electrode, 5 ... common ink chamber, 6 ... top plate, 7 ... orifice plate, 8 ... nozzle, 9 ... base substrate, 10 Electrodes, 11 ... printed circuit boards, 12 ... drive ICs, 13 ... conductive patterns, 14 ... conductors, 15 (15a to 15c) ... pressure chambers, 16 ... actuators, 16a and 16b ... partition walls, 20 ... meniscus, 51 ... graphs, 52 ... Graph, 53 ... Graph, 61 ... Graph, 62 ... Graph, 63 ... Graph, 81 to 83 ... Time points, 91 to 93 ... Time points, 100 ... Inkjet head, 101 ... Head drive circuit, 102 ... Channel group, 200 ... Printer, 201 ... Processor, 202 ... ROM, 203 ... RAM, 204 ... Operation panel, 205 ... Communication interface, 206 ... Conductor motor, 207 ... Motor drive circuit, 208 ... Pump, 209 ... Pump drive circuit, 211 ... Bus line, 301 ... Pattern generator, 302 ... Frequency setting unit, 303 ... Drive signal generator, 304 ... Switch circuit.

Claims (5)

An actuator that expands or contracts the pressure chamber that communicates with the nozzle that ejects ink,
To the actuator
After applying the expansion pulse that expands the pressure chamber,
A first contraction pulse that contracts the pressure chamber to a first volume is applied, and a second contraction pulse that contracts the volume of the pressure chamber to a second volume smaller than the first volume is applied.
Control unit and
Equipped with
The width of the second contraction pulse changes from the first contraction pulse to the second contraction pulse, and then the meniscus formed in the nozzle advances into the pressure chamber. Including the first time point when the state progresses to the outside of the pressure chamber,
Liquid discharge head. The first time point is the time point when the flow velocity of the meniscus becomes 0 for the third time after the control unit applies the expansion pulse.
The liquid discharge head according to claim 1. The first contraction pulse has a width including a second time point in which the meniscus changes from a state of traveling outside the pressure chamber to a state of the meniscus traveling inside the pressure chamber.
The liquid discharge head according to claim 1 or 2. The period between the first time point and the end time point of the second contraction pulse is less than a quarter of the natural vibration cycle of the pressure in the pressure chamber.
The liquid discharge head according to any one of claims 1 to 3. A printer that ejects droplets onto a medium
A transport mechanism that transports the medium and
An actuator that expands or contracts the pressure chamber that communicates with the nozzle that ejects ink,
To the actuator
After applying the expansion pulse that expands the pressure chamber,
A first contraction pulse that contracts the pressure chamber to a first volume is applied, and a second contraction pulse that contracts the volume of the pressure chamber to a second volume smaller than the first volume is applied.
With a control unit,
The width of the second contraction pulse changes from the first contraction pulse to the second contraction pulse, and then the meniscus formed in the nozzle advances into the pressure chamber. Including the first time point when the state progresses to the outside of the pressure chamber,
With a liquid discharge head,
A printer equipped with.

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