JP2022146216A - Liquid discharge device - Google Patents

Abstract

To solve the problem that waveform designing is complex.SOLUTION: A liquid discharge device 1 includes a discharge part 10 for discharging liquid, and a drive signal generation part 60 for generating drive signals. A drive signal Com comprises a first discharge pulse Pw1 for discharging a first droplet 26A, and a second discharge pulse Pw2 for discharging a second droplet 26B. The first discharge pulse Pw1 and the second discharge pulse Pw2 have the same shape. The discharge pulses Pw1, Pw2 comprise expansion elements a1, a2 for expanding a pressure chamber 12, contraction elements c1, c2 for contracting the pressure chamber 12, and damping elements e1, e2 for expanding the pressure chamber 12 and weakening residual oscillation of liquid in the pressure chamber 12. A first pulse interval Ti1 which is an interval between the first discharge pulse Pw1 and the second discharge pulse Pw2 are adjusted in a period when the first droplet 26A and the second droplet 26 can be united before the first droplet 26A lands on a medium PA.SELECTED DRAWING: Figure 4

Description

The present invention relates to a liquid ejection device.

For example, Patent Literature 1 describes a liquid ejection device. The liquid ejecting apparatus supplies a drive signal including a drive waveform to the drive element to cause pressure fluctuations in the liquid in the pressure chamber. As a result, the liquid in the pressure chamber is pushed out and droplets are ejected from the nozzle.

JP 2017-95814 A

In a conventional liquid ejecting apparatus, ejection pulses with different waveforms are used to combine a plurality of droplets before the plurality of droplets land on a medium. However, when designing a plurality of ejection pulses with different waveforms, it is necessary to adjust the ejection stability of droplets by each ejection pulse and the relationship between the plurality of ejection pulses, which complicates the waveform design. was there.

A liquid ejecting apparatus according to the present invention includes a nozzle that ejects liquid to land on a medium, a pressure chamber that communicates with the nozzle, a drive element that causes pressure fluctuations in the liquid in the pressure chamber by being supplied with a drive signal, and a drive signal generator that generates a drive signal. A drive signal includes a first ejection pulse for ejecting a first droplet from the nozzle, and a second ejection pulse which is supplied to the driving element subsequent to the first ejection pulse and causes a second droplet to be ejected from the nozzle. including pulses. The first ejection pulse and the second ejection pulse have the same shape. The first ejection pulse includes a first expansion element that expands the pressure chamber, a first contraction element that contracts the pressure chamber expanded by the first expansion element, and contraction of the pressure chamber by the first contraction element. a first damping element that expands the pressure chamber after being damped to dampen the residual vibration of the liquid in the pressure chamber. The second ejection pulse includes a second expansion element that expands the pressure chamber, a second contraction element that contracts the pressure chamber expanded by the second expansion element, and contraction of the pressure chamber by the second contraction element. a second damping element that expands the pressure chamber after being damped to dampen the residual vibration of the liquid in the pressure chamber. The first pulse interval, which is the interval between the first ejection pulse and the second ejection pulse, allows the first droplet and the second droplet to coalesce before the first droplet lands on the medium. Adjusted for possible periods.

1 is a schematic diagram of a liquid ejection device according to an embodiment; FIG. 1 is a block diagram showing a liquid ejection device; FIG. It is a sectional view showing a discharge part. 4 is a waveform diagram showing waveforms of drive signals according to the first embodiment; FIG. 4 is a diagram showing a plurality of ink droplets ejected from a nozzle N; FIG. 7 is a graph showing the relationship between the length of the interval Ti1 and the velocity Vm2 of the subsequent ink droplets caused by the ejection pulse Pw2. FIG. 10 is a waveform diagram showing waveforms of drive signals according to the second embodiment; 4 is a diagram showing a plurality of ink droplets ejected from a nozzle N; FIG. 7 is a graph showing the relationship between the length of the interval Ti2 and the velocity Vm3 of the subsequent ink droplets caused by the ejection pulse Pw3.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from the actual ones. In addition, since the embodiments described below are preferred specific examples of the present invention, they are subject to various technically preferable limitations. It is not limited to these forms unless stated otherwise.

FIG. 1 is a schematic perspective view showing the internal configuration of a liquid ejection device 1 according to an embodiment. FIG. 2 is a block diagram showing the liquid ejection device 1. As shown in FIG. The liquid ejection device 1 shown in FIG. 1 ejects ink droplets from the ejection section 10 and lands the ink droplets on the medium PA. The medium PA is, for example, printing paper. The liquid ejecting apparatus 1 includes a liquid ejecting unit 20 having an ejecting unit 10, a carriage 3 on which the liquid ejecting unit 20 is mounted, a carriage transport mechanism 4 that transports the carriage 3, and a medium transport mechanism 5 that transports the medium PA. Prepare.

The carriage 3 is equipped with an ink cartridge 6 that stores ink. The ink cartridge 6 is an ink container that stores ink. The carriage 3 can mount a plurality of ink cartridges corresponding to, for example, four colors of ink. Four colors of ink include, for example, cyan, magenta, yellow, and black. The ink container does not have to be mounted on the carriage 3 . Ink stored in the ink cartridge is supplied to the liquid ejection section 20 .

The liquid ejection device 1 has a transport mechanism 7 . The transport mechanism 7 includes a carriage transport mechanism 4 and a medium transport mechanism 5 . The carriage transport mechanism 4 has a transport belt 4a for transporting the carriage 3 and a motor. The medium transport mechanism 5 has transport rollers 5a and a motor for transporting the medium PA. The liquid ejecting apparatus 1 causes the carriage 3 to be conveyed by the carriage conveying mechanism 4 while conveying the medium PA by the medium conveying mechanism 5 to eject ink droplets onto the medium PA for printing. The liquid ejection device 1 forms dots on the medium PA according to the print data Img.

The liquid ejection device 1 has a linear encoder 8 . A linear encoder 8 is provided at a position where the position of the carriage 3 can be detected. A linear encoder 8 acquires information about the position of the carriage 3 . The linear encoder 8 outputs encoder signals to the controller 30 as the carriage 3 moves.

The liquid ejection section 20 has a plurality of recording heads 22 . FIG. 3 is a cross-sectional view showing the ejection section 10 of the recording head 22. As shown in FIG. The print head 22 includes a plurality of ejection portions 10 and common liquid chambers 23 and 24 . The discharge part 10 includes individual channels 11 , pressure chambers 12 , communication channels 13 , and nozzles N. As shown in FIG. The liquid ejector 20 has a nozzle plate 25 in which a plurality of nozzles N are formed. The bottom surface of the nozzle plate 25 is the nozzle surface 25a. The ejection section 10 has a vibration plate 14 and a drive element 50 .

The common liquid chambers 23 and 24 communicate with the plurality of pressure chambers 12 and store ink before being supplied to the pressure chambers 12 . The common liquid chamber 24 is connected downstream of the common liquid chamber 23 . The individual channel 11 communicates the common liquid chamber 24 and the pressure chamber 12 . An individual channel 11 is provided for each pressure chamber 12 . The communication channel 13 communicates the pressure chamber 12 and the nozzle N with each other.

The diaphragm 14 forms part of the wall surface of the pressure chamber 12 . The vibration plate 14 is commonly provided for the plurality of pressure chambers 12 . A plurality of drive elements 50 are provided for each of the plurality of pressure chambers 12 . The driving element 50 includes an electrode 51 , an electrode 52 and a piezoelectric layer 53 . Electrode 51 is the lower electrode and electrode 52 is the upper electrode. Electrode 51 is a common electrode and electrode 52 is an individual electrode. A common electrode is an electrode common to a plurality of drive elements 50 . An individual electrode is provided for each of the plurality of drive elements 50 . Electrode 51 may be an individual electrode and electrode 52 may be a common electrode. The piezoelectric layer 53 is arranged between the electrodes 51 and 52 .

The electrode 51 is electrically connected to the feed line Lb. The power supply line Lb is set to the potential VBS. A supply drive signal Vin is supplied to the electrode 52 . When the supply drive signal Vin is supplied and a voltage is applied between the electrodes 51 and 52, the drive element 50 is displaced in the thickness direction according to the applied voltage. This vibrates the driving element 50 and the diaphragm 14 . The vibration of the vibration plate 14 changes the volume of the pressure chamber 12 and the pressure in the pressure chamber 12 , causing the ink filled in the pressure chamber 12 to flow into the communication channel 13 . The ink in the communication channel 13 is pushed out to the nozzle N, and the nozzle N ejects ink droplets.

As shown in FIG. 2 , the liquid ejection device 1 has a control section 30 . The control unit 30 includes one or more CPUs 31 . The control unit 30 may include an FPGA instead of the CPU 31 or in addition to the CPU 31 . Control unit 30 includes storage unit 40 . The storage unit 40 includes a RAM 42 and a ROM 41, for example. The storage unit 40 may include EEPROM or PROM. The storage unit 40 can store print data Img supplied from the host computer. The storage unit 40 stores control programs for the liquid ejection device 1 .

CPU is an abbreviation for Central Processing Unit. FPGA is an abbreviation for field-programmable gate array. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

The control section 30 generates signals for controlling the operations of each section of the liquid ejection apparatus 1 . The control unit 30 can generate the print signal SI and the waveform designation signal dCom. The print signal SI is a digital signal for designating the type of operation of the ejection section 10 . The print signal SI can designate whether or not to supply the drive signal Com to the ejection unit 10 . The waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the ejection section 10 .

The liquid ejection device 1 includes a drive signal generation circuit 60 . The drive signal generation circuit 60 is an example of a drive signal generation section. The drive signal generation circuit 60 is electrically connected to the control section 30 . The drive signal generation circuit 60 includes a DA conversion circuit. The drive signal generation circuit 60 generates a drive signal Com having a waveform defined by the waveform designation signal dCom. Upon receiving the encoder signal from the linear encoder 8 , the control section 30 outputs the timing signal PTS to the drive signal generation circuit 60 . The timing signal PTS defines the generation timing of the drive signal Com. The drive signal generation circuit 60 outputs the drive signal Com each time it receives the timing signal PTS.

The liquid ejection section 20 has a drive circuit 21 . The drive circuit 21 is electrically connected to the control section 30 and the drive signal generation circuit 60 . The drive circuit 21 switches whether to supply the drive signal Com to the ejection section 10 based on the print signal SI. The drive signal Com may include the supply drive signal Vin. The drive circuit 21 selects the drive element 50 of the ejection section 10 to which the drive signal Com is supplied based on the print signal SI, the latch signal LAT, the period designation signal Tsig, and the change signal CH supplied from the control section 30. can. The latch signal LAT defines latch timing of the print data Img. The change signal CH defines the selection timing of the drive pulse included in the drive signal Com.

FIG. 4 is a waveform diagram showing the waveform of the drive signal Com1 according to the first embodiment. In FIG. 4, the horizontal axis indicates the passage of time, and the vertical axis indicates the potential. The driving waveform included in the driving signal Com1 includes a plurality of ejection pulses Pw1 and Pw2 during one cycle T1. The ejection pulse Pw1 is an example of a first ejection pulse, and the ejection pulse Pw2 is an example of a second ejection pulse. The ejection pulse Pw2 is supplied to the drive element 50 after the ejection pulse Pw1. The ejection pulse Pw1 and the ejection pulse Pw2 have the same shape. "Same shape" includes substantially the same shape. For example, if they are considered to be substantially the same including errors and noise, they are included in the same shape.

The ejection pulse Pw1 includes an expansion element a1, an expansion maintenance element b1, a contraction element c1, a contraction maintenance element d1, and a damping element e1. The expansion element a 1 is an element that expands the volume of the pressure chamber 12 . Expansion element a1 is an example of a first expansion element. The expansion maintaining element b2 is an element that maintains the volume of the pressure chamber 12 expanded by the expansion element a1. The contraction element c1 is an element that contracts the volume of the pressure chamber 12 maintained by the expansion maintenance element b2. The contraction element c1 is an example of a first contraction element. The contraction maintaining element d1 is an element that maintains the volume of the pressure chamber 12 contracted by the contraction element c1. The damping element e1 is an element that expands the volume of the pressure chamber 12 maintained by the contraction maintaining element d1 to dampen the residual vibration of the ink in the pressure chamber 12. FIG. Damping element e1 is an example of a first damping element.

The potential of the ejection pulse Pw1 changes between the potential V1 and the potential V2. The expansion element a1 is started from the reference potential VB. The reference potential VB is a potential between the potential V1 and the potential V2. Expansion element a1 starts at reference potential VB at time t11 and reaches potential V1 at time t12.

The expansion maintaining element b1 is maintained at potential V1. The expansion maintaining element b1 is maintained at potential V1 from time t12 to time t13. The contraction element c1 changes in potential from potential V1 to potential V2. Contraction element c1 starts at potential V1 at time t13 and reaches potential V2 at time t14.

Contraction maintaining element d1 is maintained at potential V2. Contraction maintaining element d1 is maintained at potential V2 from time t14 to time t15. The potential of the damping element e1 changes from the potential V2 to the reference potential VB. Damping element e1 starts at potential V2 at time t15 and reaches potential VB at time t16.

The drive waveform includes a connection element f1 that connects the ejection pulse Pw1 and the ejection pulse Pw2. Connection element f1 is maintained at reference potential VB. Connection element f1 is maintained at reference potential VB from time t16 to time t21.

The ejection pulse Pw2 includes an expansion element a2, an expansion maintenance element b2, a contraction element c2, a contraction maintenance element d2, and a damping element e2. The expansion element a2 is an element that expands the volume of the pressure chamber 12. As shown in FIG. The expansion element a2 is an example of a second expansion element. The expansion maintaining element b2 is an element that maintains the volume of the pressure chamber 12 expanded by the expansion element a2. The contraction element c2 is an element that contracts the volume of the pressure chamber 12 maintained by the expansion maintenance element b2. The contraction element c2 is an example of a second contraction element. The contraction maintaining element d2 is an element that maintains the volume of the pressure chamber 12 contracted by the contraction element c2. The vibration damping element e2 is an element that expands the volume of the pressure chamber 12 maintained by the contraction maintaining element d2 to dampen the residual vibration of the ink in the pressure chamber 12. FIG. The damping element e2 is an example of a second damping element.

As described above, the ejection pulse Pw2 has the same shape as the ejection pulse Pw1. Each element of the ejection pulse Pw2 changes in potential in the same manner as each element of the ejection pulse Pw1. The ejection pulse Pw2 starts at time t21 and ends at time t26. The length from time t21 to time t26 is the same as the length from time t11 to time t16.

The interval Ti1 between the first ejection pulse Pw1 and the second ejection pulse Pw2 is such that the ink droplet 26A by the ejection pulse Pw1 and the ink droplet 26B by the ejection pulse Pw2 are formed before the ink droplet 26A by the ejection pulse Pw1 lands on the medium PA. has been adjusted to a period in which it can be combined. Ink droplet 26A and ink droplet 26B are illustrated in FIG. Interval Ti1 is an example of a first pulse interval. The length of the interval Ti1 is set so that the velocity Vm2 of the subsequent ink droplet 26B is faster than the velocity Vm1 of the leading ink droplet 26A. The subsequent ink droplet 26B becomes faster than the preceding ink droplet 26A by utilizing the residual vibration of the ink in the pressure chamber 12 caused by the preceding ejection pulse Pw1.

Next, the behavior of the ink droplets 26A and 26B ejected from the nozzle N will be described with reference to FIG. FIG. 5 is a diagram showing a plurality of ink droplets 26A and 26B ejected from nozzle N. As shown in FIG. When the driving signal Com1 is supplied to the driving element 50, pressure fluctuation occurs in the ink inside the pressure chamber 12, the ink inside the pressure chamber 12 is pushed out, and ink droplets 26A and 26B are ejected from the nozzle N. The ink droplet 26A is an example of a first droplet, and the ink droplet 26B is an example of a second droplet. The ink droplet 26A is ejected by supplying the ejection pulse Pw1 to the drive element 50. FIG. The ink droplet 26B is ejected by supplying the ejection pulse Pw2 to the driving element 50. FIG. After ink droplet 26A is ejected, ink droplet 26B is ejected. The velocity Vm2 of the trailing ink droplet 26B is faster than the velocity Vm1 of the leading ink droplet 26A. For example, ink droplet 26B coalesces with ink droplet 26A in mid-air. The coalesced ink droplets land on the medium PA. A coalesced ink drop is an example of a coalesced drop. Ink droplet 26B may, for example, coalesce with ink droplet 26A within a distance of 0.5 mm from nozzle face 25A.

Next, the velocity Vm2 of the subsequent ink droplet 26B will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the length of the interval Ti1 and the velocity Vm2 of the subsequent ink droplet 26B. In FIG. 6, the horizontal axis indicates the length of the interval Ti1, and the vertical axis indicates the velocity Vm2 of the subsequent ink droplet 26B. The length of the interval Ti1 is the length of the connection element f1 as described above. In FIG. 6, the length of the interval Ti1 is shown with the natural vibration period Tc of the ejection portion 10 as a reference. The relationship between the interval Ti1 and the speed Vm2 may be calculated based on experimental measurement data, or may be calculated by simulation. Depending on the length of the interval Ti1, the timing of supplying the ejection pulse Pw2 to the drive element 50 with respect to the residual vibration of the ink in the pressure chamber 12 remaining after the ejection pulse Pw1 is supplied to the drive element 50 changes. As a result, the velocity Vm2 of the ink droplet 26B ejected by the ejection pulse Pw2 changes.

The natural vibration period Tc of the discharge section 10 may be measured by performing an experiment, or may be calculated by simulation. The velocity of the ink droplet 26B may be measured by performing an experiment, or may be calculated by simulation. The natural vibration period Tc may be the natural vibration period of vibration of the ink in the pressure chamber 12 .

The natural vibration period Tc may be calculated using, for example, the following formula (1). In Equation (1), Mn is the mass of ink per unit length in the nozzle N [kg/m]. The direction of the unit length is, for example, along the vibration direction of the ink. Ms is the mass [kg/m] of ink per unit length in the individual channel 11 that supplies ink to the pressure chamber 12 . Cc is the volume change of ink per unit pressure in the pressure chamber 12 [m ³ /N].
Tc=2π[{(Mn×Ms)/(Mn+Ms)}×Cc] ^1/2 (1)

As shown in FIG. 6, when the length of the interval Ti1 is 0.814Tc or more and 1.431Tc or less, the velocity Vm2 of the ink droplet 26B is 6.0m/s or more. When the length of the interval Ti1 is 1.082 Tc or more and 1.137 Tc or less, the velocity Vm2 of the ink droplet 26B is 6.5 m/s or more.

When the interval Ti1 is 0.814 to 1.431 times the natural vibration period Tc, the velocity Vm2 of the subsequent ink droplet 26B is 6.0 m/s or more, and the ink droplets 26A and 26B coalesce after coalescence. A droplet lands on the medium PA.

When the interval Ti1 is 1.082 times or more and 1.137 times or less of the natural vibration period Tc, the velocity Vm2 of the subsequent ink droplet 26B is 6.5 m/s or more, and after the ink droplets 26A and 26B coalesce, the A droplet lands on the medium PA.

According to the liquid ejecting apparatus 1 according to the present embodiment, while the ejection pulses Pw1 and Pw2 have the same shape, the interval between the ejection pulse Pw1 and the ejection pulse Pw2 is adjusted. The ink droplets 26A and 26B can be coalesced in the air by making the velocity Vm2 higher than the velocity Vm1 of the ink droplet 26A by the preceding ejection pulse Pw1. Since the liquid ejecting apparatus 1 uses the ejection pulses Pw1 and Pw2 having the same shape, waveform design becomes easy. By using the ejection pulses Pw1 and Pw2 having the same shape, it is possible to easily adjust the ink ejection stability for each of the ejection pulses Pw1 and Pw2, and avoid the complexity of adjusting the relationship between the ejection pulses Pw1 and Pw2.

In the liquid ejection device 1, the ink droplets 26A and 26B can be combined, so scattering of mist can be suppressed. In the liquid ejection device 1, the ink droplets 26A and 26B can be combined to increase the mass of the ink droplets, so that the influence of the airflow in the vicinity of the nozzle surface 25a can be reduced. As a result, in the liquid ejecting apparatus 1, flight deflection of ink droplets can be suppressed.

The pulse width of the ejection pulse Pw1 may be 0.54 to 1.13 times the natural vibration period Tc of the ejection section 10 . Referring to FIG. 4, the pulse width of ejection pulse Pw1 is the length from time t11, which is the start time of expansion element a1, to time t14, which is the end time of contraction element c1. When the pulse width of the ejection pulse Pw1 is 0.54 to 1.13 times the natural vibration period Tc, the ejection pulse Pw1 can stably eject an ink droplet 26A having a desired weight.

The length of the contraction maintaining element d1 of the ejection pulse Pw1 may be 0.49 times or more and 0.90 times or less of the natural vibration period Tc of the ejection section 10 . Referring to FIG. 4, the length of the contraction maintaining element d1 is the length from time t14, which is the end time of the contraction element c1, to time t15, which is the start time of the damping element e1. When the length of the contraction maintaining element d1 is 0.49 to 0.90 times the natural vibration period Tc, the velocity Vm2 of the ink droplet 26B ejected by the subsequent ejection pulse Pw2 can be preferably adjusted. Therefore, it is possible to cause the vibrating plate 14 to vibrate so that the speed of the ink droplets 26B can be appropriately adjusted.

Next, the waveform of the drive signal Com2 according to the second embodiment will be described with reference to FIG. FIG. 7 is a waveform diagram showing the waveform of the drive signal Com2 according to the second embodiment. The drive waveform of the drive signal Com2 according to Example 2 includes a plurality of ejection pulses Pw1, Pw2, Pw3, and Pw4 during one cycle T2. The ejection pulse Pw3 is an example of a third ejection pulse. The ejection pulse Pw3 is supplied to the drive element 50 after the ejection pulse Pw2. The ejection pulse Pw4 is supplied to the drive element 50 after the ejection pulse Pw3. The ejection pulses Pw1, Pw2, Pw3, and Pw4 have the same shape. In addition, in the description of the second embodiment, the description similar to that of the first embodiment is omitted.

The ejection pulse Pw3 includes an expansion element a3, an expansion maintenance element b3, a contraction element c3, a contraction maintenance element d3, and a damping element e3. The expansion element a3 expands the volume of the pressure chamber 12. As shown in FIG. The expansion maintaining element b3 is an element that maintains the volume of the pressure chamber 12 expanded by the expansion element a3. The contraction element c3 is an element that contracts the volume of the pressure chamber 12 maintained by the expansion maintenance element b3. The contraction maintaining element d3 is an element that maintains the volume of the pressure chamber 12 contracted by the contraction element c3. The vibration damping element e3 is an element that expands the volume of the pressure chamber 12 maintained by the contraction maintaining element d3 to dampen the residual vibration of the ink in the pressure chamber 12. FIG. The ejection pulse Pw3 has the same shape as the ejection pulses Pw1 and Pw2. Each element of the ejection pulse Pw3 changes in potential in the same manner as each element of the ejection pulses Pw1 and Pw2.

The ejection pulse Pw4 includes an expansion element a4, an expansion maintenance element b4, a contraction element c4, a contraction maintenance element d4, and a damping element e4. The ejection pulse Pw4 has the same shape as the ejection pulses Pw1, Pw2, and Pw3. Each element of the ejection pulse Pw4 changes in potential in the same manner as each element of the ejection pulses Pw1, Pw2, and Pw3.

The drive signal Com2 according to the second embodiment includes a connection element f2 that connects the ejection pulse Pw2 and the ejection pulse Pw3. The connection element f2 continues from the end of the ejection pulse Pw2 until the start of the ejection pulse Pw3. Connection element f2 is maintained at reference potential VB. The length of connecting element f2 is the length of interval Ti2. Interval Ti2 is an example of a second pulse interval. The interval Ti2 is shorter than the interval Ti1.

The interval Ti2 is adjusted to a period in which the ink droplet 26C generated by the ejection pulse Pw3 cannot catch up with the combined ink droplet of the ink droplets 26A and 26B before the combined ink droplet of the ink droplets 26A and 26B lands on the medium PA. there is A coalesced ink drop is an example of a coalesced drop. Ink drop 26C is illustrated in FIG. The velocity Vm3 of the ink droplet 26C is slower than the velocity Vm2 of the ink droplet 26B.

The drive signal Com2 according to the second embodiment includes a connection element f3 that connects the ejection pulse Pw3 and the ejection pulse Pw4. The connection element f3 continues from the end of the ejection pulse Pw3 until the start of the ejection pulse Pw4. Connection element f3 is maintained at reference potential VB. The length of the connecting element f3 is the length of the interval Ti3. The interval Ti3 is longer than the interval Ti2.

The interval Ti3 may be adjusted to a period in which the ink droplet 26D produced by the ejection pulse Pw4 and the ink droplet 26C produced by the ejection pulse Pw3 are combined before the ink droplet 26C produced by the ejection pulse Pw3 lands on the medium PA. The length of the interval Ti3 is set so that the velocity Vm4 of the subsequent ink droplet 26D is faster than the velocity Vm3 of the leading ink droplet 26C. The subsequent ink droplet 26D becomes faster than the preceding ink droplet 26C by utilizing the residual vibration of the ink in the pressure chamber 12 caused by the preceding ejection pulse Pw3. The interval Ti3 is adjusted to a period in which the ink droplets 26C and 26D coalesce using the residual vibration of the ink in the pressure chamber 12 due to the ejection pulses Pw1 to Pw3 before the ink droplets 26C and 26D reach the medium PA. ing.

Next, the behavior of ink droplets 26A to 26D ejected from nozzle N will be described with reference to FIG. FIG. 8 is a diagram showing a plurality of ink droplets 26A-26D ejected from nozzle N. As shown in FIG. When the driving signal Com2 is supplied to the driving element 50, pressure fluctuation occurs in the ink inside the pressure chamber 12, the ink inside the pressure chamber 12 is pushed out, and ink droplets 26A to 26D are ejected from the nozzle N. FIG. Ink droplet 26C is an example of a third droplet. The ink droplet 26C is ejected by supplying the ejection pulse Pw3 to the drive element 50. FIG. The ink droplet 26D is ejected by supplying the ejection pulse Pw4 to the drive element 50. FIG.

After ink droplet 26B is ejected, ink droplet 26C is ejected. The velocity Vm3 of the subsequent ink droplet 26C is lower than the velocity Vm2 of the preceding ink droplet 26B. For example, ink drop 26C cannot catch up with ink drop 26B in air. The ink droplet 26C does not coalesce with the ink droplet 28B before landing on the medium PA.

After the ink droplet 26C is ejected, the ink droplet 26D is ejected. The velocity of the trailing ink drop 26D is faster than the velocity of the leading ink drop 26C. For example, ink droplet 26D may coalesce with ink droplet 26C in mid-air. Ink droplet 26D can coalesce with ink droplet 26C before landing on medium PA.

Next, the speed Vm3 of the ink droplet 26C will be described with reference to FIG. FIG. 9 is a graph showing the relationship between the length of the interval Ti2 and the velocity Vm3 of the subsequent ink droplet 26C caused by the ejection pulse Pw3. In FIG. 9, the horizontal axis indicates the length of the interval Ti2, and the vertical axis indicates the velocity Vm3 of the subsequent ink droplet 26C. The length of the interval Ti2 is the length of the connecting element f2 as described above. In FIG. 9, the length of the interval Ti2 is shown with the natural vibration period Tc of the ejection portion 10 as a reference. Depending on the length of the interval Ti2, the timing of supplying the ejection pulse Pw3 to the drive element 50 with respect to the residual vibration of the ink in the pressure chamber 12 remaining after the ejection pulses Pw1 and Pw2 are supplied to the drive element 50 changes. As a result, the velocity Vm3 of the ink droplet 26C ejected by the ejection pulse Pw3 changes.

As shown in FIG. 9, when the length of the interval Ti2 is 0.515 Tc or more and 1.000 Tc or less, the velocity Vm3 of the ink droplet 26C is less than 6.0 m/s. When the length of the interval Ti2 is 0.685Tc or more and 0.795Tc or less, the velocity Vm3 of the ink droplet 26C is 5.5m/s or less.

When the interval Ti2 is 0.515 to 1.000 times the natural vibration period Tc, the velocity Vm3 of the subsequent ink droplet 26C is less than 6.0 m/s, and the ink droplet 26C reaches the medium PA before reaching the medium PA. cannot catch up with the ink droplet 26B.

When the interval Ti2 is 0.685 times to 0.795 times the natural vibration period Tc, the velocity Vm3 of the subsequent ink droplet 26C is 5.5 m/s or less, and the ink droplet 26C reaches the medium PA before reaching the medium PA. cannot catch up with the ink droplet 26B.

Since the liquid ejection apparatus 1 according to the second embodiment uses ejection pulses Pw1 to Pw4 having the same shape, waveform design can be facilitated. By using the ejection pulses Pw1 to Pw4 having the same shape, it is possible to easily adjust the ejection stability of the ink in each of the ejection pulses Pw1 to Pw4, and to avoid the complexity of adjusting the relationship between the ejection pulses Pw1 to Pw4.

It should be noted that the above-described embodiment merely shows a typical form of the present invention, and the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Changes and additions are possible.

In the above-described embodiments, the liquid ejecting apparatus 1 is described as a serial inkjet printer, but the liquid ejecting apparatus 1 is not limited to a serial inkjet printer. The liquid ejection device 1 may be a line-type inkjet printer in which a plurality of liquid ejection units 20 are arranged in a straight line.

In the above embodiment, the drive signal includes a plurality of ejection pulses Pw, but the drive signal may include a plurality of drive pulses that cause the nozzles N not to eject ink. For example, a non-ejection pulse that does not eject ink may be included between the ejection pulse Pw1 and the ejection pulse Pw2.

In the above embodiment, the interval Ti1 is exemplified as 0.814 to 1.431 times the natural vibration period Tc of the ejection section 10, but the interval Ti1 is not limited to this. The interval Ti1 may be less than 0.814 times the natural vibration period Tc. The interval Ti1 may be longer than 1.431 times the natural vibration period TC.

In the above embodiment, the interval Ti2 is exemplified as 0.515 to 1.000 times the natural vibration period Tc of the discharge section 10, but the interval Ti2 is not limited to this. The interval Ti2 may be less than 0.515 times the natural vibration period Tc. The interval Ti2 may be longer than 1.000 times the natural vibration period Tc.

The liquid ejecting apparatus 1 exemplified in the above embodiments can be employed in various types of equipment such as facsimile machines and copiers, in addition to equipment dedicated to printing. However, the application of the liquid ejecting apparatus of the present invention is not limited to printing. For example, a liquid ejecting apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus for forming a color filter for a display device such as a liquid crystal display panel. Also, a liquid ejecting apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus for forming wiring and electrodes of a wiring board. Further, a liquid ejecting apparatus that ejects a solution of an organic matter related to living organisms is used as a manufacturing apparatus for manufacturing biochips, for example.

REFERENCE SIGNS LIST 1 liquid ejection device 10 ejection section 12 pressure chamber 20 liquid ejection section 26A ink droplet (first droplet) 26B ink droplet (second droplet) 50 drive element , 60... drive signal generation circuit (drive signal generator), a1... expansion element (first expansion element), a2... expansion element (second expansion element), c1... contraction element (first contraction element), c2... Contraction element (second contraction element), e1... Damping element (first damping element), e2... Damping element (second damping element), N... Nozzle, PA... Medium, Pw1... Ejection pulse (first ejection pulse), Pw2... Ejection pulse (second ejection pulse), Pw3... Ejection pulse (third ejection pulse), Ti1... Interval (first pulse interval), Ti2... Interval (second pulse) 2 pulse intervals).

Claims (7)

an ejection portion having a nozzle for ejecting a liquid to land on a medium, a pressure chamber communicating with the nozzle, and a drive element for causing pressure fluctuations in the liquid in the pressure chamber by being supplied with a drive signal;
a drive signal generator that generates the drive signal;
with
The driving signal includes a first ejection pulse for ejecting a first droplet from the nozzle, and a drive element supplied to the driving element subsequent to the first ejection pulse to eject a second droplet from the nozzle. a second ejection pulse;
the first ejection pulse and the second ejection pulse have the same shape,
The first ejection pulse is
a first expansion element that expands the pressure chamber;
a first contraction element for contracting the pressure chamber expanded by the first expansion element;
a first damping element that expands the pressure chamber after the pressure chamber is contracted by the first contraction element to dampen residual vibration of the liquid in the pressure chamber;
The second ejection pulse is
a second expansion element that expands the pressure chamber;
a second contraction element for contracting the pressure chamber expanded by the second expansion element;
a second damping element that expands the pressure chamber after the pressure chamber is contracted by the second contraction element to dampen residual vibration of the liquid in the pressure chamber;
The first pulse interval, which is the interval between the first ejection pulse and the second ejection pulse, is the interval between the first droplet and the second droplet before the first droplet lands on the medium. is adjusted to a period during which the droplets of
Liquid ejection device. The first pulse interval is 0.814 times or more and 1.431 times or less of the natural vibration period Tc of the ejection portion.
The liquid ejection device according to claim 1. The first pulse interval is 1.082 times or more and 1.137 times or less of the natural vibration period Tc of the discharge section.
The liquid ejection device according to claim 2. the drive signal includes a third ejection pulse that is supplied to the drive element following the second ejection pulse and causes a third droplet to be ejected from the nozzle;
The third ejection pulse has the same shape as the first ejection pulse and the second ejection pulse,
The second pulse interval, which is the interval between the second ejection pulse and the third ejection pulse, is such that a united droplet formed by uniting the first droplet and the second droplet lands on the medium. adjusted to a period in which the third droplet does not catch up with the coalesced droplet before
The liquid ejection device according to any one of claims 1 to 3. The second pulse interval is 0.515 times or more and 1.000 times or less of the natural vibration period Tc of the discharge section.
The liquid ejection device according to claim 4. The second pulse interval is 0.685 times or more and 0.795 times or less of the natural vibration period Tc of the ejection portion.
The liquid ejection device according to claim 5. the second pulse interval is shorter than the first pulse interval;
6. The liquid ejection device according to claim 4 or 5.

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