JP7192547B2 - Droplet ejection device and droplet ejection method - Google Patents

Description

The present invention relates to a droplet ejection device and a droplet ejection method, and more particularly to a droplet ejection device and a droplet ejection method capable of preventing deterioration and breakage of piezoelectric elements over a long period of time.

2. Description of the Related Art Conventionally, droplet ejection devices such as inkjet printers are known that eject droplets (ink) from nozzles of a droplet ejection head to form an image on a recording medium.

A droplet discharge device has a plurality of pressure chambers, expands or contracts the volume of each pressure chamber by a piezoelectric element, and discharges the liquid in each pressure chamber from a plurality of nozzles. The piezoelectric element is driven by a drive signal supplied from the drive circuit.

In Patent Document 1, before the start of ejection of droplets from a nozzle (during standby), a piezoelectric element has a positive potential portion that exceeds the coercive electric field on the positive side and a negative potential portion that falls below the coercive electric field on the positive side so as not to eject droplets. A droplet ejection device adapted to be supplied with a signal is described.

JP 2014-172314 A

The droplet ejection device described in Patent Document 1 uses a drive signal whose potential changes from the positive side to the negative side during standby. Since a large stress is applied to the piezoelectric element over a period of time, there is a risk of deterioration or breakage of the piezoelectric element. When the piezoelectric element deteriorates or breaks, the driving efficiency of the piezoelectric element decreases, resulting in a drop in droplet ejection speed.

Accordingly, it is an object of the present invention to provide a droplet ejection apparatus and a droplet ejection method that can prevent deterioration and breakage of piezoelectric elements over a long period of time.

Other objects of the present invention will become clear from the following description.

The above problems are solved by the following inventions.

1.
a liquid droplet ejection head having a pressure chamber and expanding or contracting the volume of the pressure chamber by a piezoelectric element to eject the liquid in the pressure chamber from a nozzle;
a drive circuit that supplies a drive signal to the piezoelectric element corresponding to the pressure chamber;
The driving circuit converts a first input waveform containing an intermediate potential and a maximum potential during standby, and a second input waveform containing the maximum potential and a minimum potential for droplet ejection, into the first and second input waveforms. generating said drive signal by switching when both input waveforms are at said highest potential;
The droplet discharge device, wherein the absolute value of the intermediate potential is lower than the absolute value of the highest potential, and the intermediate potential and the highest potential have the same sign.
2.
2. The liquid droplet ejecting apparatus according to 1, wherein the first input waveform includes an oscillating waveform that vibrates the interface of the liquid in the nozzle.
3.
3. The droplet ejection device according to 1 or 2, wherein the potential difference between the highest potential and the intermediate potential is 0.2 to 0.4 times the potential difference between the intermediate potential and the lowest potential.
4.
A droplet ejection method for supplying a drive signal to a piezoelectric element corresponding to a pressure chamber of a droplet ejection head to expand or contract the volume of the pressure chamber and eject the liquid in the pressure chamber from a nozzle,
A first waveform containing an intermediate potential and a maximum potential during standby, and a second waveform containing the maximum potential and a minimum potential for discharging droplets are formed so that both the first and second waveforms are at the maximum potential. generating said drive signal by switching at a certain time;
A droplet discharge method, wherein the absolute value of the intermediate potential is lower than the absolute value of the highest potential, and the intermediate potential and the highest potential are potentials of the same sign.
5.
5. The liquid droplet ejection method according to 4 above, wherein the first waveform includes an oscillating waveform that vibrates the interface of the liquid in the nozzle.
6.
6. The droplet ejection method according to 4 or 5, wherein the potential difference between the highest potential and the intermediate potential is 0.2 to 0.4 times the potential difference between the intermediate potential and the lowest potential.

According to the present invention, it is possible to provide a droplet ejection apparatus and a droplet ejection method that can prevent deterioration and breakage of a piezoelectric element over a long period of time.

1 is a schematic configuration diagram showing a droplet ejection device according to an embodiment of the present invention; FIG. Sectional view of a droplet ejection head of the droplet ejection device Block diagram of the electrical configuration of the droplet discharge device 4 is a timing chart showing input waveforms input to the drive circuit of the droplet discharge device of the first embodiment; 4 is a timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the first embodiment; A timing chart showing input waveforms input to the drive circuit of the droplet discharge device of the second embodiment. A timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the second embodiment. A timing chart showing input waveforms input to the drive circuit of the droplet discharge device of the third embodiment. A timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.
Since the droplet ejection method according to the embodiment of the present invention is performed by the drive circuit of the droplet ejection device according to the embodiment, the description of the operation of the drive circuit will be used to describe the droplet ejection method.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a droplet ejection device according to an embodiment of the present invention.

As shown in FIG. 1, the droplet ejection device 1 of the embodiment includes, for example, four droplet ejection heads 10A, 10B, 10C, and 10D. Each of the droplet ejection heads 10A, 10B, 10C, and 10D has a plurality of pressure chambers, and the volume of each pressure chamber is expanded or contracted by a piezoelectric element to eject the liquid in the plurality of pressure chambers from a plurality of nozzles. Let

In the present embodiment, each of the droplet ejection heads 10A, 10B, 10C, and 10D is an inkjet head for each color ink such as Y (yellow), M (magenta), C (cyan), and K (black). They are arranged side by side in the scanning direction (the X direction in FIG. 1). However, in the present invention, the droplets are not limited to ink, and the number of droplet ejection heads is not limited to four. Also, the number of pressure chambers and nozzles in the droplet discharge head is not limited to plural, and each may be single.

Each of the droplet ejection heads 10A, 10B, 10C, and 10D is mounted on a common carriage 20 with the nozzle surface having a plurality of nozzles facing the recording medium 50 . Each of the droplet ejection heads 10A, 10B, 10C, and 10D is electrically connected to a drive circuit provided in the droplet ejection device 1 via a flexible cable 30, respectively. The drive circuit supplies a drive signal to each of the piezoelectric elements corresponding to the plurality of pressure chambers of the droplet ejection heads 10A, 10B, 10C, and 10D.

The carriage 20 is reciprocally moved along the guide rail 40 in the main scanning direction by a main scanning motor. The recording medium 50 is intermittently conveyed by a predetermined amount by a sub-scanning motor in a sub-scanning direction (Y direction in FIG. 1) perpendicular to the main scanning direction.

Each of the droplet ejection heads 10A, 10B, 10C, and 10D ejects ink from a plurality of nozzles toward the recording medium 50 while being moved in the main scanning direction. A predetermined image is printed on the recording medium 50 by cooperation between the movement of the droplet ejection heads 10A, 10B, 10C, and 10D in the main scanning direction and the intermittent conveyance of the recording medium 50 in the sub-scanning direction.

FIG. 2 is a cross-sectional view of the droplet ejection head 10A of the droplet ejection device. Since the droplet ejection heads 10A, 10B, 10C, and 10D have the same configuration, FIG. 2 shows the configuration of the droplet ejection head 10A as a representative.

The droplet discharge head 10A includes a head substrate 11, a wiring substrate 12, and an adhesive resin layer 13, as shown in FIG. The head substrate 11 and the wiring substrate 12 are laminated in order from the lower layer side in FIG. 2 with the adhesive resin layer 13 interposed therebetween. An ink manifold 14 is joined to the upper surface of the wiring board 12 in FIG. The inside of the ink manifold 14 is a common ink chamber 14a in which ink is stored on the wiring board 12. As shown in FIG.

The head substrate 11 includes a nozzle plate 11a made of a Si (silicon) substrate, an intermediate plate 11b made of a glass substrate, a pressure chamber plate 11c made of a Si (silicon) substrate, and a _SiO2 thin film. and the diaphragm 11d. The nozzle plate 11a, the intermediate plate 11b, the pressure chamber plate 11c, and the vibration plate 11d are stacked in order from the lower layer side in FIG. A plurality of nozzles 11e are formed in the nozzle plate 11a. Each nozzle 11e is formed through the nozzle plate 11a and the intermediate plate 11b.

A plurality of pressure chambers 15 each containing ink are formed as through holes in the pressure chamber plate 11c. Each pressure chamber 15 is a closed space with the intermediate plate 11b serving as a lower wall and the diaphragm 11d serving as an upper wall. Each pressure chamber 15 is communicated with a nozzle 11e passing through the intermediate plate 11b. One nozzle 11 e is formed for each pressure chamber 15 .

Piezoelectric elements 16 are laminated corresponding to the pressure chambers 15 on the upper surface of the diaphragm 11d. The piezoelectric element 16 is a thin film PZT (lead zirconate titanate) or the like, and is sandwiched between an upper electrode and a lower electrode (both not shown) as drive electrodes. The upper electrode is an electrode separated for each piezoelectric element 16 and serves as a drive electrode for each piezoelectric element 16 . The lower electrode spreads over the entire upper surface of the vibration plate 11 d and serves as a common electrode common to all the piezoelectric elements 16 . A common electrode is grounded.

A wiring pattern is formed on the wiring board 12 . This wiring supplies drive signals from drive circuits provided for the droplet discharge heads 10A, 10B, 10C, and 10D to the drive electrodes of the piezoelectric elements 16, respectively.

The adhesive resin layer 13 is formed of, for example, a thermosetting photosensitive adhesive resin sheet, and bonds the head substrate 11 and the wiring substrate 12 together. A space corresponding to the thickness of the adhesive resin layer 13 is formed between the head substrate 11 and the wiring substrate 12 . The adhesive resin layer 13 has an opening formed by removing the area corresponding to the piezoelectric element 16 and its periphery by exposure and development processes. Each piezoelectric element 16 is arranged in an opening of the adhesive resin layer 13 .

The wiring substrate 12 and the adhesive resin layer 13 are formed with an ink supply path 12a and a through hole 13a penetrating vertically so as to correspond to each pressure chamber 15. As shown in FIG. The ink supply path 12a and the through hole 13a communicate with each other. The upper end of each ink supply path 12a communicates with the common ink chamber 14a, and the lower end of each through hole 13a communicates with each pressure chamber 15. As shown in FIG. The common ink chamber 14a communicates with each pressure chamber 15 through the ink supply path 12a and the through hole 13a.

In the droplet ejection head 10A, ink is supplied from the common ink chamber 14a to each pressure chamber 15 through the ink supply path 12a and the through hole 13a. A drive signal including an expansion pulse and a contraction pulse is supplied to the drive electrode of each piezoelectric element 16 from the drive circuit. When the piezoelectric element 16 is deformed by the drive signal, the diaphragm 11d is displaced and the volume of the corresponding pressure chamber 15 is expanded or contracted. The pressure of the ink in the pressure chamber 15 is changed by expansion or contraction of the pressure chamber 15, and is ejected from the nozzle 11e toward the recording medium 50. FIG.

FIG. 3 is a block diagram of the electrical configuration of the droplet discharge device.

The droplet ejection device 1 is used by being connected to a host computer 200 via a communication line, as shown in FIG. The droplet ejection device 1 includes the droplet ejection heads 10A, 10B, 10C, and 10D described above, drive circuits 60A, 60B, 60C, and 60D corresponding to the respective droplet ejection heads 10A, 10B, 10C, and 10D, and a host computer. 200 and a control device 100 connected thereto.

The control device 100 has an interface controller 101, an image memory 102, a transfer section 103, a CPU (Central Processing Unit) 104, a main scanning motor 105, a sub-scanning motor 106, an input operation section 107, a drive signal generation circuit 108, and the like.

The interface controller 101 receives image information to be printed on the recording medium 50 from the host computer 200 .

Image memory 102 temporarily stores image information received via interface controller 101 . The image information stored in the image memory 102 is input to drive circuits 60A, 60B, 60C and 60D.

The transfer unit 103 has a timing generation circuit 103a and a memory control circuit 103b. The timing generation circuit 103a obtains the positional information of the carriage 20 using, for example, an encoder sensor (not shown). From the position information of the carriage 20, the memory control circuit 103b obtains the address of the partial image information required for each of the droplet ejection heads 10A, 10B, 10C, and 10D. Using the address of the partial image information, the memory control circuit 103b retrieves the partial image information recorded by one ejection from the plurality of nozzles 11e of the droplet ejection heads 10A, 10B, 10C, and 10D from the image memory 102. Read out and transfer to each drive circuit 60A, 60B, 60C, 60D.

The CPU 104 is a control unit that controls the droplet ejection device 1, and controls conveyance of the recording medium 50, movement of the carriage 20, and ejection of ink from the droplet ejection heads 10A, 10B, 10C, and 10D.

The main scanning motor 105 is a motor for moving the carriage 20 shown in FIG. 1 in the main scanning direction. A sub-scanning motor 106 is a motor for conveying the recording medium 50 in the sub-scanning direction. Driving of the main scanning motor 105 and sub-scanning motor 106 is controlled by the CPU 104 .

An input operation unit 107 is a part where the CPU 104 receives various input operations by an operator, and is, for example, a touch panel or a keyboard.

The driving signal generation circuit 108 generates signal waveforms of driving signals for ejecting ink from the droplet ejection heads 10A, 10B, 10C, and 10D. This signal waveform is synchronized with the image information latch signal of the timing generation circuit 103a, is generated for each latch signal, and is input to each of the drive circuits 60A, 60B, 60C, and 60D.

Each drive circuit 60A, 60B, 60C, 60D has a voltage setting section 61A, 61B, 61C, 61D, respectively. The voltage setting units 61A, 61B, 61C, and 61D set predetermined voltages based on the signal waveform of the drive signal input from the drive signal generation circuit . The drive circuits 60A, 60B, 60C, and 60D apply the drive signals whose voltages are set by the voltage setting units 61A, 61B, 61C, and 61D to the corresponding droplet ejection heads 10A, 60D based on the image information sent from the image memory 102. It is supplied to the drive electrodes of the piezoelectric elements 16 of 10B, 10C and 10D. The voltage values set by the voltage setting units 61A, 61B, 61C and 61D may be independently controlled by the CPU 104 for each of the drive circuits 60A, 60B, 60C and 60D.

FIG. 4 is a timing chart showing input waveforms input to the drive circuit of the droplet ejection device of the first embodiment.

As shown in FIG. 4, the signal waveforms input from the drive signal generation circuit 108 to the drive circuits 60A, 60B, 60C, and 60D are the first potentials including the intermediate potential (Vref) and the highest potential (Vh) during standby. An input waveform (COM1) and a second input waveform (COM2) containing the highest potential (Vh) and the lowest potential (Vlx) for droplet ejection. The second input waveform (COM2) also includes a middle potential (Vref) and a low potential (Vlo) between the middle potential (Vref) and the lowest potential (Vlx).

A first input waveform (COM1) is selected and supplied to each piezoelectric element 16 when each of the droplet ejection heads 10A, 10B, 10C, and 10D is on standby. The second input waveform (COM2) is selected and supplied to each piezoelectric element 16 when droplets are ejected from each of the droplet ejection heads 10A, 10B, 10C, and 10D.

In the first and second input waveforms (COM1, COM2), the absolute value of the intermediate potential (Vref) is lower than the absolute value of the highest potential (Vh), and the intermediate potential (Vref) and the highest potential (Vh) Vh) is a potential of the same sign. Both the intermediate potential (Vref) and the highest potential (Vh) may be positive potentials, or both may be negative potentials.

In this embodiment, the highest potential (Vh) is, for example, about 30-36V. The intermediate potential (Vref) is, for example, about 15-20V. The low potential (Vlo) is about 0V, for example. The lowest potential (Vlx) is, for example, about -15 to -20V.

The absolute value of the intermediate potential (Vref) is lower than the absolute value of the highest potential (Vh), and the intermediate potential (Vref) and the highest potential (Vh) have the same sign. The linearity of the piezoelectric element is maintained because it does not use a potential with a different sign than (Vref) and does not pass through 0V. Also, since the absolute value of the intermediate potential (Vref) is low, the piezoelectric element 16 is not subjected to large stress over a long period of time. As a result, deterioration of the drive efficiency of the piezoelectric element 16 can be suppressed in this droplet discharge device, and deterioration and breakage of the piezoelectric element 16 can be prevented over a long period of time.

The potential difference (V2) between the highest potential (Vh) and the intermediate potential (Vref) is preferably 0.2 to 0.4 times the potential difference (V1) between the intermediate potential (Vref) and the lowest potential (Vlx). . By setting the potential difference (V1, V2) to such a ratio, the intermediate potential (Vref) can be suppressed (while suppressing the deterioration of the piezoelectric element 16), and a sufficient driving force can be obtained by pulling and striking. 16 driving efficiency can be increased. Here, the pull-out means that the ink in the nozzle 11e is once drawn into the pressure chamber 15 side by the expansion of the pressure chamber 15, and then the ink is ejected by the contraction of the pressure chamber 15. FIG.

In this embodiment, the first input waveform (COM1) is a pulse waveform in which the intermediate potential (Vref) and the highest potential (Vh) are periodically switched, and the interface (meniscus) of the liquid in the nozzle 11e. It is a waveform that includes a rocking waveform that vibrates. The oscillating waveform is a drive pulse weaker than the contraction pulse for ejecting droplets, and is a contraction or expansion pulse that contracts or expands the volume of the pressure chamber 15 within a range where only pressure waves are generated. This is a waveform for shaking the interface of the liquid in the nozzle 11e for the purpose of suppressing clogging (decap) caused by drying and increasing viscosity of the ink. The first input waveform (COM1) can suppress decap by including the fluctuation waveform.

In this embodiment, the second input waveform (COM2) is a pulse waveform that starts at an intermediate potential (Vref) and periodically switches between a highest potential (Vh) and a low potential (Vlo) or lowest potential (Vlx). , and has a waveform including an ejection waveform for ejecting the liquid in the nozzle 11e. The pulse reaching the highest potential (Vh) is a contraction pulse (ejection pulse) that contracts the volume of the pressure chamber 15, and the pulse reaching the low potential (Vlo) and the pulse reaching the lowest potential (Vlx) are the An expansion pulse that expands the volume. The second input waveform (COM2) includes a plurality of contraction pulses (ejection pulses) and can perform gradation control by so-called multi-drive.

In this embodiment, the rising and falling edges of each pulse are sloped waveforms. By using a slope waveform, it is possible to suppress unstable ejection such as satellites, abnormal speed, and bending, which is a preferable aspect in the present invention.

FIG. 5 is a timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the first embodiment.

Each drive circuit 60A, 60B, 60C, 60D, as shown in FIGS. Q), a drive signal is generated and supplied to each piezoelectric element 16 of the corresponding droplet ejection heads 10A, 10B, 10C, and 10D.

The waveform shown in FIG. 5(a) shows that when the first input waveform (COM1) reaches the highest potential (Vh) for the third time (Q), the second input which is at the highest potential (Vh) It is a drive signal that switches to the waveform (COM2), then returns to the intermediate potential (Vref) via the lowest potential (Vlx) (expansion pulse), the highest potential (Vh) (ejection pulse). Droplets are discharged when the maximum potential (Vh) is reached.

In this drive signal, the first input waveform (COM1) is switched to the second input waveform (COM2) when (Q) changes from the intermediate potential (Vref) to the highest potential (Vh). After switching to the second input waveform (COM2), the expansion pulse causes liquid (ink) to flow into the pressure chamber 15 from the common ink chamber 14a. This expanded state is maintained for a certain period of time. The next contraction pulse causes the volume of the pressure chamber 15, which was in the inflated state, to contract. A positive pressure wave is generated in the pressure chamber 15 due to the contraction of the volume of the pressure chamber 15 . This pressure wave pushes the liquid out of the nozzle 11e to eject droplets. This contracted state is maintained for a certain period of time. With the next expansion pulse, the volume of pressure chamber 15 begins to expand again, and the volume of pressure chamber 15 returns to its standby state. A negative pressure wave is generated in the pressure chamber 15 by expanding the volume of the pressure chamber 15 . This pressure wave generates a composite wave with the positive pressure wave generated within the pressure chamber 15 by the contraction pulse.

The waveform shown in FIG. 5(b) shows that when the first input waveform (COM1) reaches the highest potential (Vh) for the second time (Q), the second input waveform (COM1) is at the highest potential (Vh). After switching to the waveform (COM2), the low potential (Vlo) (expansion pulse) and the highest potential (Vh) (ejection pulse) are repeated, the lowest potential (Vlx) (expansion pulse) and the highest potential (Vh) (ejection pulse). ) to return to the intermediate potential (Vref). Droplet ejection occurs when a low potential (Vlo) and a lowest potential (Vlx) (expansion pulse) are followed by a highest potential (Vh).

The waveform shown in FIG. 5(c) is the first input waveform (COM1) when the first input waveform (COM1) reaches the highest potential (Vh) at the first time (Q), the second input which is the highest potential (Vh) After switching to the waveform (COM2), the low potential (Vlo) (expansion pulse) and the highest potential (Vh) (ejection pulse) are repeated, the lowest potential (Vlx) (expansion pulse) and the highest potential (Vh) (ejection pulse). ) to return to the intermediate potential (Vref). Droplet ejection occurs when a low potential (Vlo) and a lowest potential (Vlx) (expansion pulse) are followed by a highest potential (Vh).

In these drive waveforms, since the input waveforms are switched when both the first and second input waveforms (COM1, COM2) are at the highest level (Vh), the low potential (Vlo) or the lowest potential (Vlx) is switched after that. ) can be a pulse having a large potential difference, and the droplet ejection speed can be increased. In addition, since the ejection pulse can be a pulse reaching the highest level (Vh), it is possible to widen the range in which the droplet ejection amount can be controlled. A wide controllable range means that there is a large difference between the minimum ejection amount for one ejection and the maximum ejection amount for one ejection.

[Second embodiment]
Since the configuration of the droplet ejection device is the same as that of the first embodiment, the description is omitted by citing the description.

FIG. 6 is a timing chart showing input waveforms input to the drive circuit of the droplet ejection device of the second embodiment.

In this embodiment, the first input waveform (COM1) is similar to the first input waveform (COM1) of the first embodiment, as shown in FIG. A second input waveform (COM2) is a pulse waveform that starts from an intermediate potential (Vref) and periodically switches between a highest potential (Vh) and a low potential (Vlo) or a lowest potential (Vlx). The waveform includes an ejection waveform for ejecting the liquid in 11e. A pulse reaching the lowest potential (Vlx) returns to the intermediate potential (Vref) without reaching the highest potential (Vh).

FIG. 7 is a timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the second embodiment.

The waveform shown in FIG. 7(a) shows that when the first input waveform (COM1) reaches the highest potential (Vh) for the third time (Q), the second input waveform (COM1), which is at the highest potential (Vh), It is a drive signal that switches to a waveform (COM2), then returns to an intermediate potential (Vref) via the lowest potential (Vlx) (expansion pulse). Droplet ejection occurs when the intermediate potential (Vref) follows the lowest potential (Vlx) (expansion pulse).

The waveform shown in FIG. 7(b) shows that when the first input waveform (COM1) reaches the highest potential (Vh) for the second time (Q), the second input waveform (COM1), which is at the highest potential (Vh), It is a drive signal that switches to the waveform (COM2), then repeats the low potential (Vlo) and the highest potential (Vh) (ejection pulse), returns to the intermediate potential (Vref) through the lowest potential (Vlx) (expansion pulse). . Droplet ejection occurs when a low potential (Vlo) (expansion pulse) is followed by a highest potential (Vh) and a lowest potential (Vlx) (expansion pulse) is followed by an intermediate potential (Vref).

The waveform shown in FIG. 7(c) is the first input waveform (COM1) when the first input waveform (COM1) reaches the highest potential (Vh) for the first time (Q). It is a drive signal that switches to the waveform (COM2), then repeats the low potential (Vlo) and the highest potential (Vh) (ejection pulse), returns to the intermediate potential (Vref) through the lowest potential (Vlx) (expansion pulse). . Droplet ejection occurs when a low potential (Vlo) (expansion pulse) is followed by a highest potential (Vh) and a lowest potential (Vlx) (expansion pulse) is followed by an intermediate potential (Vref).

In these drive waveforms, since the input waveforms are switched when both the first and second input waveforms (COM1, COM2) are at the highest level (Vh), the low potential (Vlo) or the lowest potential (Vlx) is switched after that. ) can be a pulse having a large potential difference, and the droplet ejection speed can be increased. In addition, since the ejection pulse can be a pulse reaching the highest level (Vh), it is possible to widen the range in which the droplet ejection amount can be controlled.

[Third Embodiment]
Since the configuration of the droplet ejection device is the same as that of the first embodiment, the description is omitted by citing the description.

FIG. 8 is a timing chart showing input waveforms input to the drive circuit of the droplet discharge device of the third embodiment.

In this embodiment, the first input waveform (COM1) is, as shown in FIG. 8, a waveform that includes an intermediate potential (Vref) and a highest potential (Vh) and does not include a swing waveform. The second input waveform (COM2) is the same as the second input waveform (COM2) of the first embodiment.

FIG. 9 is a timing chart showing drive signals supplied to the droplet ejection head of the droplet ejection device of the third embodiment.

The waveform shown in FIG. 9(a) is that after the highest potential (Vh) is maintained for a predetermined long time (Q) in the first input waveform (COM1), the second input waveform at the highest potential (Vh) (COM2), and then the lowest potential (Vlx) (expansion pulse), the highest potential (Vh) (ejection pulse), and then return to the intermediate potential (Vref). Droplets are discharged when the maximum potential (Vh) is reached.

The waveform shown in FIG. 9B is such that after the highest potential (Vh) is maintained for a predetermined short time (Q) in the first input waveform (COM1), the second input waveform at the highest potential (Vh) (COM2), after which the low potential (Vlo) (expansion pulse) and highest potential (Vh) (ejection pulse) are repeated, and the lowest potential (Vlx) (expansion pulse) and highest potential (Vh) (ejection pulse) , and returns to the intermediate potential (Vref). Droplet ejection occurs when a low potential (Vlo) and a lowest potential (Vlx) (expansion pulse) are followed by a highest potential (Vh).

The waveform shown in FIG. 9(c) switches to the second input waveform (COM2), which is the highest potential (Vh), when the first input waveform (COM1) reaches the highest potential (Vh) (Q). , then the low potential (Vlo) (expansion pulse) and the highest potential (Vh) (ejection pulse) are repeated, and the intermediate potential ( Vref) is the drive signal. Droplet ejection occurs when a low potential (Vlo) and a lowest potential (Vlx) (expansion pulse) are followed by a highest potential (Vh).

In these drive waveforms, since the input waveforms are switched when both the first and second input waveforms (COM1, COM2) are at the highest level (Vh), the low potential (Vlo) or the lowest potential (Vlx) is switched after that. ) can be a pulse having a large potential difference, and the droplet ejection speed can be increased. In addition, since the ejection pulse can be a pulse reaching the highest level (Vh), it is possible to widen the range in which the droplet ejection amount can be controlled.

[Regarding each embodiment]
In each of the above-described embodiments, a single plate type piezoelectric element is used, but the present invention is not limited to this. For example, a laminated piezoelectric element may be used, or another type of piezoelectric element such as a shear mode type piezoelectric element that deforms in a shear mode may be used. A shear mode type piezoelectric element is preferable because a rectangular drive waveform can be used more effectively, the drive voltage can be lowered, and more efficient drive can be achieved.

In the above description, an inkjet head for recording an image is used as the droplet ejection head. However, the present invention is not limited to this. Any device provided with a piezoelectric element that changes the pressure in the pressure chamber can be similarly applied.

Furthermore, the detailed configuration and detailed operation of each part constituting the droplet discharge device 1 in the above embodiment can be changed as appropriate without departing from the scope of the present invention.

1 droplet ejection devices 10A, 10B, 10C, 10D droplet ejection head 11 head substrate 11a nozzle plate 11b intermediate plate 11c pressure chamber plate 11d vibration plate 11e nozzle 12 wiring substrate 13 adhesive resin layer 14 ink manifold 15 pressure chamber 16 piezoelectric element 50 recording medium 100 control device 101 interface controller 102 image memory 103 transfer unit 103a timing generation circuit 103b memory control circuit 104 CPU
105 main scanning motor 106 sub-scanning motor 107 input operation unit 108 drive signal generation circuits 60A, 60B, 60C, 60D drive circuits 61A, 61B, 61C, 61D voltage setting unit 200 host computer

Claims (4)

a piezoelectric element that is sandwiched between a drive electrode and a grounded common electrode and deforms when a drive signal having a potential difference with respect to the potential of the common electrode is supplied to the drive electrode;
a liquid droplet ejection head having a pressure chamber and expanding or contracting the volume of the pressure chamber by the piezoelectric element to eject the liquid in the pressure chamber from a nozzle;
a drive circuit that supplies the drive signal to the piezoelectric element corresponding to the pressure chamber;
The drive circuit is
During standby, from the highest potential , which is positive or negative, which is the maximum potential difference with respect to the potential of the common electrode, to an intermediate potential, which has the same sign as the highest potential and is small and positive or negative . and including a wobble waveform that vibrates the interface of the liquid in the nozzle as the drive signal;
a second input for ejecting droplets, wherein the potential difference with respect to the highest potential changes from the highest potential to the lowest potential with the same sign as the potential difference with respect to the highest potential of the intermediate potential, when droplets are ejected; switching to a waveform to provide the second input waveform as the drive signal;
A droplet discharge device, wherein switching between the first input waveform and the second input waveform is performed when both the first and second input waveforms are at the highest potential. 2. The droplet discharge device according to claim 1, wherein the potential difference between the highest potential and the intermediate potential is 0.2 to 0.4 times the potential difference between the intermediate potential and the lowest potential. supplying the drive signal to a piezoelectric element sandwiched between a drive electrode and a grounded common electrode and having a potential difference with respect to the potential of the common electrode, the piezoelectric element deforming when the drive signal is supplied to the drive electrode; A droplet ejection method for expanding or contracting the volume of a pressure chamber of a droplet ejection head corresponding to the piezoelectric element and ejecting the liquid in the pressure chamber from a nozzle,
During standby, from the highest potential , which is positive or negative, which is the maximum potential difference with respect to the potential of the common electrode, to an intermediate potential, which has the same sign as the highest potential and is small and positive or negative . and including a wobble waveform that vibrates the interface of the liquid in the nozzle as the drive signal;
a second input for ejecting droplets, wherein the potential difference with respect to the highest potential changes from the highest potential to the lowest potential with the same sign as the potential difference with respect to the highest potential of the intermediate potential, when droplets are ejected; switching to a waveform to provide the second input waveform as the drive signal;
A droplet discharge method, wherein switching between the first input waveform and the second input waveform is performed when both the first and second input waveforms are at the highest potential. 4. The droplet discharging method according to claim 3, wherein the potential difference between the highest potential and the intermediate potential is 0.2 to 0.4 times the potential difference between the intermediate potential and the lowest potential.

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