JP2017105220A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid-jetting type printer and the like in which an amplified modulation signal at the high frequency is used, a coil with the high conversion efficiency that can suppress heat generation and loss at the time of smoothing the amplified modulation signal can be selected, and which has the low power consumption.SOLUTION: A liquid discharge device includes: a signal modulation part 26 which performs pulse modulation of an original drive signal 125 and generates a modulation signal 126; a signal amplification part 28 which amplifies the modulation signal 126 and generates an amplified modulation signal 128; a coil L which smooths the amplified modulation signal 128 and generates a drive signal COM; a piezoelectric element PZT which is deformed with application of the drive signal COM; a cavity which expands or contracts due to deformation of the piezoelectric element PZT; and a nozzle which communicates with the cavity and discharges the liquid due to the increase/decrease of the pressure in the cavity. A core material of the coil L is Mn-Zn-based ferrite.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a liquid ejecting apparatus and a head unit that eject a liquid by applying a drive signal to an actuator. For example, fine liquid is ejected from a nozzle of a liquid ejecting head to form fine particles (dots) on a print medium. Thus, the present invention is suitable for a liquid jet printing apparatus that prints predetermined characters, images, and the like.

  As an example of a liquid ejecting apparatus, an ink jet printer that ejects ink (liquid) from a nozzle provided in a head toward a recording medium is known. In general, the head is formed with a nozzle row in which a large number of nozzles are arranged in a predetermined direction. For example, the head receives ink while relatively moving in a direction in which the scanning direction of the head intersects the conveyance direction of the recording medium. The nozzles are arranged in a line in a direction that intersects with the conveyance direction of the print medium as described in Japanese Patent Application Laid-Open No. 2005-26838 or a serial head method in which an image having a nozzle row width is printed by discharging. A line head system or the like in which an image is printed when passing below is known.

JP 2011-5733 A

  Here, Patent Document 1 exemplifies the use of a secondary filter composed of one capacitor C and a coil L as a smoothing filter, but there is no description about what coil L should be used.

  Coils used to smooth the amplified modulation signal from the digital power amplifier circuit generally tend to generate heat and loss, and selecting a coil that suppresses heat and loss is a One big challenge in design. In particular, in a printer, in order to obtain a printed matter having sufficient quality and resolution, an amplified modulation signal having a high frequency such as MHz order is used. Therefore, other electronic devices (for example, a general audio device has a frequency of about 32 kHz to 400 kHz). It is difficult to use the coil selection method as it is.

  The present invention has been made to solve the above-described problems. For example, in a liquid jet printing apparatus using a high frequency amplified modulation signal such as an ink jet printer, heat generation and loss when the amplified modulation signal is smoothed. An object of the present invention is to provide a liquid jet printing apparatus with low power consumption and a head unit used in the apparatus.

  (1) The liquid ejection apparatus of the present invention includes a signal modulation unit that generates a modulation signal by pulse-modulating an original drive signal, a signal amplification unit that amplifies the modulation signal to generate an amplification modulation signal, and the amplification modulation A coil that generates a drive signal by smoothing a signal, a piezoelectric element that deforms when the drive signal is applied, a cavity that expands or contracts due to deformation of the piezoelectric element, and a cavity that communicates with the cavity. And a nozzle that discharges liquid by increasing or decreasing the pressure of the coil, and the core material of the coil is Mn—Zn-based ferrite.

  In the liquid ejection device, a high frequency amplification modulation signal generated by a signal amplification unit (for example, a digital power amplification circuit) is input to the coil. Therefore, iron loss (loss of core material) is more dominant than copper loss (loss of wire) as a factor to increase the heat generation and power consumption of the coil. Since the liquid discharge apparatus of the present invention uses a coil having Mn—Zn ferrite as a core material, it is possible to suppress eddy current loss that occupies most of the iron loss. Since the coil that can obtain high conversion efficiency without increasing the heat loss and power consumption by suppressing the iron loss is used, the liquid ejection device of the present invention can realize low power consumption.

  The original drive signal is a signal that is a source of a drive signal that controls deformation of the piezoelectric element, that is, a signal before modulation and a signal that serves as a waveform reference. The modulation signal is a digital signal obtained by pulse modulation (for example, pulse width modulation, pulse density modulation, etc.) of the original drive signal, and the signal modulation unit is a modulation circuit that performs the pulse modulation. The signal amplifying unit is, for example, a digital power amplifier circuit having a half-bridge output stage, and the amplified modulation signal is a modulated signal amplified by the signal amplifying unit. The drive signal is a signal obtained by smoothing the amplified modulation signal using a coil, and is applied to the piezoelectric element.

  (2) Further, the frequency band of the AC component of the amplified modulated signal may be 1 MHz or more.

  In the liquid ejection device of the present invention, the amplification modulation signal is smoothed to generate a drive signal, and the liquid is ejected from the nozzle based on deformation of the piezoelectric element to which the drive signal is applied. Here, when the frequency spectrum analysis is performed on the waveform of the drive signal for the liquid ejection device to eject small dots (small dots), it is found that a frequency component of 50 kHz or less is included. In order to amplify the original drive signal including a frequency component of 50 kHz by a digital power amplifier circuit (a signal amplification unit supports), a modulation signal (amplification modulation signal) including a frequency component of 1 MHz or more is required. If the original drive signal is to be reproduced with only a frequency component of 1 MHz or less, the waveform edge becomes dull and rounded. In other words, the corners are removed and the waveform becomes dull. When the waveform of the drive signal is dull, the movement of the piezoelectric element that operates in response to the rising and falling edges of the waveform becomes slow, and unstable driving such as tailing during discharge or defective discharge occurs. In the liquid ejection apparatus of the present invention, since the frequency band of the alternating current component of the amplification modulation signal is 1 MHz or more, there is no unstable driving such as tailing or ejection failure during ejection, and a liquid with which a product with high resolution can be obtained. A discharge device can be realized.

  (3) The frequency band of the AC component of the amplified modulated signal may be less than 8 MHz.

  If a high frequency of 8 MHz or higher is supported as the frequency of the amplified modulation signal, the resolution of the waveform of the drive signal is increased, but the switching frequency in the digital power amplifier circuit (corresponding to the signal amplifying unit) is increased as the resolution is improved. When the switching frequency is increased, the switching loss increases, and the power saving and heat saving properties that the digital amplifier has superiority to the class AB amplifier are impaired, and amplification by the class AB amplifier may be better. In the liquid ejection device of the present invention, since the frequency band of the AC component of the amplified modulation signal is less than 8 MHz, it is possible to maintain advantages such as low power consumption and heat saving as compared with the case where a class AB amplifier is used.

  (4) The coil may be characterized in that a resistance component including a core loss and a wire loss is less than 200 mΩ when operated at 4 MHz.

In a coil using Mn—Zn-based ferrite as a core material, there is a correlation between the resistance component including copper loss (wire loss) and iron loss (core loss) and power consumption. This liquid ejecting apparatus can realize further lower power consumption by selecting a coil having a resistance component of less than 200 mΩ when operated at 4 MHz. In addition, 4 MHz operation | movement is giving a pulse signal with a frequency of 4 MHz to a coil.

  (5) Further, the signal modulation unit may generate the modulation signal by feeding back the drive signal.

  This liquid ejection device can feed back a drive signal and generate a modulation signal whose basic modulation operation is the same as that of a PDM (Pulse-Density Modulation) system based on a delay element of the drive signal. At this time, the smaller the value of the delay element, the higher the frequency of the generated modulation signal, and the waveform reproducibility is improved. This liquid ejecting apparatus can reduce the value of the delay element of the drive signal by performing phase advance correction using, for example, an error amplifier. Therefore, this liquid ejecting apparatus can realize modulation with good waveform reproducibility by feeding back the drive signal.

  (6) The head unit of the present invention includes a piezoelectric element that is deformed when a drive signal is applied, a cavity that expands or contracts due to the deformation of the piezoelectric element, an increase or decrease in pressure in the cavity that communicates with the cavity. The piezoelectric element is applied with a drive signal generated by smoothing the amplified modulation signal by a coil whose core material is Mn-Zn ferrite. To do.

  This head unit includes a piezoelectric element to which a drive signal generated by a coil having Mn—Zn ferrite as a core material is applied. Therefore, the liquid discharge apparatus including the head unit uses a coil that can suppress the iron loss and increase the heat generation and power consumption without increasing the heat generation and power consumption, and can achieve low power consumption.

1 is a block diagram illustrating an overall configuration of a printing system. It is a schematic sectional drawing of a printer. It is a schematic top view of a printer. It is a figure for demonstrating the structure of a head. It is a figure for demonstrating the drive signal COM from a drive signal generation part, and the control signal used for dot formation. It is a block diagram explaining the structure of a head control part. It is a figure explaining the flow until the production | generation of the drive signal COM. It is a detailed block diagram of a drive signal generator and the like. It is a figure explaining the difference of Rs by the kind of core material. It is a figure explaining the ratio of the iron loss and copper loss in Rs. FIG. 11A is a diagram for explaining the ratio between hysteresis loss and eddy current loss, and FIG. 11B is a diagram for explaining eddy current. FIGS. 12A and 12B are diagrams for explaining the correlation between Rs of a coil using a core material of Mn—Zn-based ferrite and power consumption. 13A is an external plan view of the coil, and FIGS. 13B and 13C are cross-sectional views taken along the line AA of FIG. 13A for explaining the core gap and the number of turns of the coil. FIG. It is a figure which illustrates the change of the frequency-Rs characteristic by the difference in the core gap and the winding number of a coil. It is a spectrum analysis figure of the original drive signal.

1. Configuration of Printing System As an embodiment of the liquid ejecting apparatus of the present invention, one applied to a liquid ejecting type printing apparatus will be described.

  FIG. 1 is a block diagram illustrating an overall configuration of a printing system including a liquid jet printing apparatus (printer 1) according to the present embodiment. As will be described later, the printer 1 is a line head printer in which a sheet S (see FIGS. 2 and 3) is transported in a predetermined direction and printed in a printing area in the middle of the transport.

  The printer 1 is communicably connected to the computer 80, and a printer driver installed in the computer 80 creates print data for causing the printer 1 to print an image and outputs the print data to the printer 1. The printer 1 includes a controller 10, a paper transport mechanism 30, a head unit 40, and a detector group 70. As will be described later, the printer 1 may include a plurality of head units 40, but here, one head unit 40 will be representatively shown in FIG.

  A controller 10 in the printer 1 is for performing overall control in the printer 1. The interface unit 11 transmits and receives data to and from the computer 80 that is an external device. The interface unit 11 outputs the print data 111 among the data received from the computer 80 to the CPU 12. The print data 111 includes, for example, image data, data specifying a print mode, and the like.

  The CPU 12 is an arithmetic processing unit for performing overall control of the printer 1, and controls the head unit 40 and the paper transport mechanism 30 via the drive signal generator 14, the control signal generator 15, and the transport signal generator 16. To do. The memory 13 is used to secure an area for storing programs and data of the CPU 12, a work area, and the like. The state in the printer 1 is monitored by the detector group 70, and the controller 10 performs control based on the detection result from the detector group 70. Note that the program and data of the CPU 12 may be stored in the storage medium 113. The storage medium 113 may be any one of a magnetic disk such as a hard disk, an optical disk such as a DVD, and a non-volatile memory such as a flash memory, but is not particularly limited. As illustrated in FIG. 1, the CPU 12 may be able to access a storage medium 113 connected to the printer 1. Further, the storage medium 113 may be connected to the computer 80, and the CPU 12 may be able to access the storage medium 113 via the interface unit 11 and the computer 80 (the path is not shown).

  The drive signal generation unit 14 generates a drive signal COM that displaces the piezoelectric element PZT included in the head 41. As will be described later, the drive signal generation unit 14 includes a part of the original drive signal generation unit 25, a signal modulation unit 26, a signal amplification unit 28 (digital power amplification circuit), and a signal conversion unit 29 (smooth filter) (see FIG. 7). The drive signal generation unit 14 generates an original drive signal 125 by the original drive signal generation unit 25 according to an instruction from the CPU 12, and generates a modulation signal 126 by pulse-modulating the original drive signal 125 by the signal modulation unit 26. The amplifying unit 28 amplifies the modulated signal 126, and the signal converting unit 29 smoothes the amplified modulated signal 128 (the amplified modulated signal 126) to generate the drive signal COM.

  The control signal generator 15 generates a control signal according to an instruction from the CPU 12. The control signal is a signal used for controlling the head 41, for example, selecting a nozzle to be ejected. In this embodiment, the control signal generation unit 15 generates a control signal including a clock signal SCK, a latch signal LAT, a channel signal CH, and drive pulse selection data SI & SP. Details of these signals will be described later. The control signal generation unit 15 may have a configuration included in the CPU 12 (that is, a configuration in which the CPU 12 also functions as the control signal generation unit 15).

  Here, the drive signal COM generated by the drive signal generation unit 14 is an analog signal whose voltage continuously changes, and the clock signal SCK, the latch signal LAT, the channel signal CH, and the drive pulse selection data SI & SP which are control signals are digital. Signal. The drive signal COM and the control signal are transmitted to the head 41 of the head unit 40 via the cable 20 which is a flexible flat cable (hereinafter also referred to as FFC). As for the control signal, a plurality of types of signals may be transmitted in a time division manner using a differential serial method. At this time, the number of necessary transmission lines can be reduced as compared with the case where the control signals are transmitted in parallel for each type, and a decrease in slidability due to the superposition of many FFCs can be avoided. The size of the connector provided in the unit 40 is also reduced.

  The transport signal generator 16 generates a signal for controlling the paper transport mechanism 30 in accordance with an instruction from the CPU 12. The paper transport mechanism 30 rotatably supports a continuous paper S wound in a roll shape, for example, and transports the paper S by rotation so that predetermined characters, images, and the like are printed in the printing area. For example, the paper transport mechanism 30 transports the paper S in a predetermined direction based on the signal generated by the transport signal generator 16. The carrier signal generation unit 16 may have a configuration included in the CPU 12 (that is, a configuration in which the CPU 12 also functions as the carrier signal generation unit 16).

  The head unit 40 includes a head 41 as a liquid ejection unit. For the sake of space, only one head 41 is shown in FIG. 1, but the head unit 40 of the present embodiment is assumed to include a plurality of heads 41. The head 41 includes at least two actuator units including the piezoelectric element PZT, the cavity CA, and the nozzle NZ, and also includes a head control unit HC that controls the displacement of the piezoelectric element PZT. The actuator unit communicates with the cavity CA, the piezoelectric element PZT that can be displaced by the drive signal COM, the cavity CA that is filled with liquid and the internal pressure is increased or decreased by the displacement of the piezoelectric element PZT, It includes a nozzle NZ that ejects liquid as droplets by increasing or decreasing the pressure in the cavity CA. The head controller HC controls the displacement of the piezoelectric element PZT based on the drive signal COM and the control signal from the controller 10.

  Here, in order to distinguish the elements included in each actuator part, the numerals in parentheses are attached to the reference numerals. In the example of FIG. 1, there are three actuator units, and the first actuator unit includes a first piezoelectric element PZT (1), a first cavity CA (1), a first nozzle NZ (1), The actuator section includes a second piezoelectric element PZT (2), a second cavity CA (2), and a second nozzle NZ (2), and the third actuator section includes a third piezoelectric element PZT (3), a third cavity. CA (3) and the third nozzle NZ (3) are included. The number of actuator parts is not limited to three, and may be two, for example, or four or more. In FIG. 1, for convenience of illustration, the first to third actuator portions are included in one head 41, but a part thereof may be included in another head 41 (not shown).

  The drive signal COM is generated by the drive signal generator 14 as shown in FIG. 1, and the first piezoelectric element PZT (1), the second piezoelectric element PZT (2), the first piezoelectric element PZT (2) via the cable 20 and the head controller HC. 3 is transmitted to the piezoelectric element PZT (3). Further, the control signal including the clock signal SCK, the latch signal LAT, the channel signal CH, and the drive pulse selection data SI & SP is generated by the control signal generator 15 as shown in FIG. Used for control in HC.

2. Configuration of Printer FIG. 2 is a schematic sectional view of the printer 1. In the example of FIG. 2, the paper S is described as continuous paper wound in a roll shape. However, the recording medium on which the printer 1 prints an image is not limited to continuous paper, and may be cut paper, cloth, film, or the like. But you can.

  The printer 1 includes a winding shaft 21 that feeds the paper S by rotation, and a relay roller 22 that winds the paper S fed from the winding shaft 21 and guides the paper S to the upstream conveying roller pair 31. Then, the printer 1 winds and feeds the paper S, a plurality of relay rollers 32 and 33, an upstream conveyance roller pair 31 disposed on the upstream side in the conveyance direction from the printing area, and a conveyance direction from the printing area. And a downstream conveying roller pair 34 disposed on the downstream side. The upstream-side transport roller pair 31 and the downstream-side transport roller pair 34 are respectively connected to a motor (not shown) to be driven and rotated, and driven rollers 31a and 34a that are driven and rotated as the drive rollers 31a and 34a are rotated. 31b, 34b. The drive rollers 31a and 34a are driven and rotated while the upstream side transport roller pair 31 and the downstream side transport roller pair 34 sandwich the paper S, respectively, so that a transport force is applied to the paper S. The printer 1 includes a relay roller 61 that winds and feeds the paper S sent from the downstream transport roller pair 34, and a winding drive shaft 62 that winds up the paper S sent from the relay roller 61. As the winding drive shaft 62 is driven to rotate, the printed paper S is sequentially wound in a roll shape. These rollers and a motor (not shown) correspond to the paper transport mechanism 30 in FIG.

  The printer 1 includes a head unit 40 and a platen 42 that supports the paper S from the opposite side of the printing surface in the printing region. The printer 1 may include a plurality of head units 40. The printer 1 may prepare a head unit 40 for each color of ink, for example, and is capable of ejecting four inks of four colors of yellow (Y), magenta (M), cyan (C), and black (K). The head units 40 may be arranged in the transport direction. In the following description, a single head unit 40 will be described as a representative. However, it is assumed that an ink color is assigned to each nozzle and color printing is possible.

  As shown in FIG. 3, in the head unit 40, a plurality of heads 41 (1) to 41 (4) are arranged in the width direction (Y direction) of the paper S that intersects the transport direction of the paper S. For the sake of explanation, small numbers are assigned in order from the head 41 on the far side in the Y direction. In addition, on the surface (lower surface) of each head 41 that faces the paper S, a large number of nozzles NZ that eject ink are arranged at predetermined intervals in the Y direction. 3 virtually shows the positions of the head 41 and the nozzle NZ when the head unit 40 is viewed from above. The positions of the nozzles NZ at the ends of the heads 41 adjacent to each other in the Y direction (for example, 41 (1) and 41 (2)) are at least partially overlapped. The nozzles NZ are arranged at predetermined intervals in the Y direction for more than that. Therefore, a two-dimensional image is printed on the paper S when the head unit 40 ejects ink from the nozzles NZ to the paper S conveyed without stopping under the head unit 40.

  In FIG. 3, four heads 41 belonging to the head unit 40 are shown for the sake of space, but the present invention is not limited to this. That is, the number of heads 41 may be more or less than four. Moreover, although the head 41 of FIG. 3 is arrange | positioned at zigzag form, it is not restricted to such arrangement | positioning. Here, the ink discharge method from the nozzle NZ is a piezo method in which ink is discharged by applying a voltage to the piezoelectric element PZT to expand and contract the ink chamber in this embodiment. A thermal method in which bubbles are generated inside and ink is ejected by the bubbles may be used.

In this embodiment, the sheet S is supported by the horizontal surface of the platen 42. However, the present invention is not limited to this. For example, a rotating drum that rotates with the width direction of the sheet S as the rotation axis is used as the platen 42. Ink may be ejected from the head 41 while the paper S is wound and conveyed. In this case, the head unit 40 is inclined and disposed along the arc-shaped outer peripheral surface of the rotating drum. Further, when the ink ejected from the head 41 is, for example, UV ink that is cured by irradiating ultraviolet rays, an irradiator that irradiates ultraviolet rays may be provided on the downstream side of the head unit 40.

  Here, the printer 1 has a maintenance area for cleaning the head unit 40. In the maintenance area of the printer 1, there are a wiper 51, a plurality of caps 52, and an ink receiving portion 53. The maintenance area is located on the back side in the Y direction with respect to the platen 42 (that is, the printing area), and the head unit 40 moves to the back side in the Y direction during cleaning.

  The wiper 51 and the cap 52 are supported by the ink receiving portion 53 and can be moved in the X direction (the transport direction of the paper S) by the ink receiving portion 53. The wiper 51 is a plate-like member erected from the ink receiving portion 53, and is formed of an elastic member, cloth, felt, or the like. The cap 52 is a rectangular parallelepiped member formed of an elastic member or the like, and is provided for each head 41. And according to arrangement | positioning of the heads 41 (1) -41 (4) in the head unit 40, the caps 52 (1) -52 (4) are also located in the width direction. Therefore, when the head unit 40 moves to the back side in the Y direction, the head 41 and the cap 52 face each other, and when the head unit 40 descends (or when the cap 52 rises), the cap 52 comes into close contact with the nozzle opening surface of the head 41. The nozzle NZ can be sealed. The ink receiving portion 53 also plays a role of receiving ink ejected from the nozzles NZ when the head 41 is cleaned.

  When ink is ejected from the nozzle NZ provided in the head 41, a minute ink droplet is generated together with the main ink droplet, and the minute ink droplet rises as a mist and adheres to the nozzle opening surface of the head 41. . Further, not only ink but also dust and paper dust adhere to the nozzle opening surface of the head 41. If these foreign substances are left on the nozzle opening surface of the head 41 and left to accumulate, the nozzle NZ is blocked and ink ejection from the nozzle NZ is hindered. Therefore, in the printer 1 of the present embodiment, the wiping process is periodically performed as the cleaning of the head unit 40.

3. Drive Signal and Control Signal Details of the drive signal COM and control signal transmitted from the controller 10 through the cable 20 will be described below. First, the structure of the head 41 will be described, and after illustrating the waveforms of the drive signal COM and the control signal, the configuration of the head controller HC will be described.

3.1. Head Structure FIG. 4 is a diagram for explaining the structure of the head 41. FIG. 4 shows a nozzle NZ, a piezoelectric element PZT, an ink supply path 402, a nozzle communication path 404, and an elastic plate 406. The ink supply path 402 and the nozzle communication path 404 correspond to the cavity CA.

  Ink drops are supplied to the ink supply path 402 from an ink tank (not shown). The ink droplet is supplied to the nozzle communication path 404. A drive pulse PCOM of the drive signal COM is applied to the piezoelectric element PZT. When the drive pulse PCOM is applied, the piezoelectric element PZT expands and contracts (displaces) according to the waveform, and the elastic plate 406 is vibrated. An ink droplet of an amount corresponding to the amplitude of the drive pulse PCOM is ejected from the nozzle NZ. Actuators composed of such nozzles NZ, piezoelectric elements PZT, and the like are arranged as shown in FIG. 3 to constitute a head 41 having a nozzle row.

3.2. Signal Waveform FIG. 5 is a diagram for explaining a drive signal COM from the drive signal generation unit 14 and a control signal used for dot formation. The drive signal COM is a time series connection of drive pulses PCOM as unit drive signals that are applied to the piezoelectric element PZT and eject liquid.
The rising portion of the drive pulse PCOM is a step of enlarging the volume of the cavity CA communicating with the nozzle and drawing the liquid, and the falling portion of the drive pulse PCOM is a step of reducing the volume of the cavity CA and extruding the liquid, As a result of extruding the liquid, the liquid is ejected from the nozzle.

  By variously changing the voltage increase / decrease slope and peak value of the drive pulse PCOM consisting of this voltage trapezoidal wave, it is possible to change the amount of liquid drawn in, the speed of drawing in, the amount of liquid pushed out, and the speed of extrusion. Different sizes of dots can be obtained by changing the ejection amount. Therefore, even when a plurality of drive pulses PCOM are connected in time series, a single drive pulse PCOM is selected and applied to the piezoelectric element PZT to eject liquid or select a plurality of drive pulses PCOM. By applying the liquid to the piezoelectric element PZT and ejecting the liquid a plurality of times, dots of various sizes can be obtained. That is, if a plurality of liquids are landed at the same position before the liquid is dried, it is substantially the same as ejecting a large liquid, and the size of the dots can be increased. By combining such techniques, it is possible to increase the number of gradations. Note that the drive pulse PCOM1 at the left end in FIG. 5 is different from the drive pulses PCOM2 to PCOM4 and does not push out only the liquid. This is called microvibration, and is used to suppress or prevent the increase in the viscosity of the nozzle without ejecting liquid.

  In addition to the drive signal COM from the drive signal generator 14, the clock signal SCK, the latch signal LAT, the channel signal CH, and the drive pulse selection data SI & SP are input to the head controller HC as the control signal from the control signal generator 15. Is done. Among them, the latch signal LAT and the channel signal CH are control signals for determining the timing of the drive signal COM. As shown in FIG. 5, a series of drive signals COM starts to be output by the latch signal LAT, and the drive is performed for each channel signal CH. A pulse PCOM is output. The drive pulse selection data SI & SP includes pixel data SI (SIH, SIL) for designating a piezoelectric element PZT corresponding to a nozzle that should eject ink droplets, and waveform pattern data SP of a drive signal COM. SIH and SIL correspond to the upper and lower bits of 2-bit pixel data SI, respectively.

3.3. Head Controller FIG. 6 is a block diagram illustrating the configuration of the head controller HC. The head controller HC includes a shift register 211 that stores drive pulse selection data SI & SP for designating a piezoelectric element PZT corresponding to a nozzle that ejects liquid, and a latch circuit 212 that temporarily stores data of the shift register 211. The level shifter 213 applies the voltage of the drive signal COM to the piezoelectric element PZT by converting the level of the output of the latch circuit 212 and supplying the output to the selection switch 201.

  The drive pulse selection data SI & SP is sequentially input to the shift register 211, and the storage area is sequentially shifted from the first stage to the subsequent stage in accordance with the input pulse of the clock signal SCK. The latch circuit 212 latches each output signal of the shift register 211 by the input latch signal LAT after the drive pulse selection data SI & SP for the number of nozzles is stored in the shift register 211. The signal stored in the latch circuit 212 is converted by the level shifter 213 to a voltage level at which the selection switch 201 at the next stage can be turned on / off. This is because the drive signal COM is higher than the output voltage of the latch circuit 212, and the operating voltage range of the selection switch 201 is set higher accordingly. Accordingly, the piezoelectric element PZT whose selection switch 201 is closed by the level shifter 213 is connected to the drive signal COM (drive pulse PCOM) at the connection timing of the drive pulse selection data SI & SP.

After the drive pulse selection data SI & SP of the shift register 211 is stored in the latch circuit 212, the next print information is input to the shift register 211, and the stored data in the latch circuit 212 is sequentially updated in accordance with the liquid ejection timing. . Even after the selection switch 201 separates the piezoelectric element PZT from the drive signal COM (drive pulse PCOM), the input voltage of the piezoelectric element PZT is maintained at the voltage just before the separation.

3.4. Drive Signal FIG. 7 is a diagram for explaining the flow until generation of the drive signal COM. As described above, a part of the original drive signal generation unit 25, the signal modulation unit 26, the signal amplification unit 28 (digital power amplification circuit), and the signal conversion unit 29 (smooth filter) in FIG. 7 correspond to the drive signal generation unit 14. doing. The original drive signal generation unit 25 generates an original drive signal 125 as shown in FIG. 7, for example, based on the print data 111 from the interface unit 11.

  As will be described later, the original drive signal generation unit 25 includes a CPU 12, a DAC 39, and the like, and the CPU 12 selects original drive data based on the print data 111 and outputs the original drive signal 125 to the DAC 39 to generate the original drive signal 125.

  When the signal modulation unit 26 receives the original drive signal 125 from the original drive signal generation unit 25, the signal modulation unit 26 performs predetermined modulation to generate a modulation signal 126. As will be described later, in the present embodiment, modulation using an error amplifier 37 (error amplifier) is performed as the predetermined modulation, but the basic modulation operation is the same as pulse density modulation (PDM). As the predetermined modulation, for example, another modulation method such as pulse width modulation (PWM) may be used.

  The signal amplifier 28 receives the modulated signal 126 and performs power amplification, and the signal converter 29 smoothes the amplified modulated signal 128 to generate an analog drive signal COM.

  Here, a detailed configuration of the functional block shown in FIG. 7 will be described. FIG. 8 is a detailed block diagram of the drive signal generation unit 14 and the like of the printer 1 according to the present embodiment. FIG. 8 also shows the head unit 40 that receives the drive signal COM generated by the drive signal generator 14.

  The original drive signal generation unit 25 reads the original drive data from the memory 13 based on the memory 13 that stores the original drive data of the original drive signal 125 configured by digital potential data and the like, and the print data 111 from the interface unit 11. It includes a CPU 12 and a DAC 39 that converts the voltage signal output from the CPU 12 into an analog signal and outputs it as an original drive signal 125.

  The signal modulation unit 26 is a circuit that generates a modulation signal 126 whose basic modulation operation is the same as that of a pulse density modulation method (hereinafter referred to as PDM method), and includes an error amplifier 37 and a comparator 35 that amplify an error.

  Here, in the PDM system, the pulse density is modulated by self-excited oscillation by comparing the output waveform with the input waveform. Usually, a circuit that realizes modulation in the PDM system includes an integration circuit, a comparator, and a delay unit, and the basic configuration is the same as a generally known ΔΣ modulator. ΔΣ modulation is one of A / D conversions for quantizing a signal. ΔΣ modulation shifts the error generated in the quantizer (comparator) by two characteristics such as oversampling and noise shaping, that is, the quantization noise to a higher frequency band than the input signal. The quantization noise shifted to the frequency band is distributed over a wide band. Then, the pulse frequency changes corresponding to the input signal level.

In the signal modulation unit 26 of the present embodiment, a path through which the modulation signal 126 returns via the signal amplification unit 28 or the like corresponds to a delay device. The signal modulator 26 uses an error amplifier 37 that amplifies the difference between two input signals instead of an integrator that is often used in a PDM modulation circuit. At this time, the feedback signal to the signal modulation unit 26 is not the amplified modulation signal 128 but the drive signal COM, and quantization is performed based on the difference between the drive signal COM and the original drive signal 125. Since the signal modulator 26 of the present embodiment does not require an integrator, the delay time (delay element) can be reduced, and the modulation process can be speeded up. Further, the signal modulation unit 26 can reduce the phase delay of the drive signal COM with respect to the original drive signal 125 by, for example, phase advance correction of the error amplifier 37. Since the oscillation frequency is increased by reducing the delay element, the signal modulator 26 can perform modulation with high waveform reproducibility.

  The signal amplifying unit 28 is a digital power amplifying circuit, and includes a half-bridge output stage composed of a high-side switching element QH and a low-side switching element QL for substantially amplifying power, and a signal modulating unit 26. And a gate drive circuit 38 for adjusting the gate input signals GH and GL of the switching element QH on the high side and the switching element QL on the low side. For example, a power MOSFET can be used as the switching elements QH and QL, but is not limited thereto.

  In the signal amplifier 28, when the modulation signal 126 is at a high level, the gate input signal GH of the high-side switching element QH is at a high level, and the gate input signal GL of the low-side switching element QL is at a low level. The high-side switching element QH is turned on, and the low-side switching element QL is turned off. As a result, the output of the half-bridge output stage is the supply voltage Vdd. On the other hand, when the modulation signal 126 is at a low level, the gate input signal GH of the high-side switching element QH is at a low level, and the gate input signal GL of the low-side switching element QL is at a high level. The switching element QH is turned off, and the low-side switching element QL is turned on. As a result, the output of the half-bridge output stage becomes zero.

  When the stop of the operation is instructed by the amplification instruction signal 112 output from the CPU 12, the gate drive circuit 38 turns off both the high-side switching element QH and the low-side switching element QL. Turning off both the high-side switching element QH and the low-side switching element QL is synonymous with stopping the operation of the signal amplifying unit 28, and is electrically equivalent to a capacitive element PZT that is a capacitive load. The actuator consisting of is maintained in a high impedance state.

  The signal conversion unit 29 is a smoothing filter and uses a secondary filter composed of a coil L and a capacitor C. The signal conversion unit 29 attenuates and removes the modulation frequency generated by the signal modulation unit 26, that is, the frequency component of pulse modulation, generates a drive signal COM, and outputs it to the head unit 40.

  The head unit 40 includes a head 41 and includes a number of piezoelectric elements PZT corresponding to nozzles that discharge liquid. The first piezoelectric element PZT (1), the second piezoelectric element PZT (2), and the third piezoelectric element PZT (3) are part of the entire piezoelectric element PZT (for example, several thousand). The head 41 includes a head control unit HC, and the head control unit HC includes a selection switch 201 that selects whether to apply the voltage of the drive signal COM to each of the piezoelectric elements PZT. In FIG. 8, illustration of functional blocks other than the cavity CA, the nozzle NZ, and the selection switch 201 of the head controller HC (for example, the shift register 211 and the like, see FIG. 6) is omitted.

As described above, the coil L is used to smooth the amplified modulated signal 128 from the signal amplifier 28 (digital power amplifier circuit) to generate the drive signal COM.
The heat generation / loss of the coil used to smooth the amplified modulated signal 128 from the digital power amplifier circuit tends to occupy a large part of the overall heat generation / power consumption of the liquid jet printing apparatus. Therefore, selecting a coil that suppresses heat generation and loss is one major problem in designing a liquid jet printing apparatus.

  In particular, in the printer 1, the amplified modulation signal 128 having a high frequency such as MHz order is used in order to obtain a printed matter having sufficient quality and resolution. Therefore, in the following, a coil selection method suitable for use in the printer 1 will be examined.

4). Coil selection 4.1. Types of core materials Generally, coils can be roughly classified into an air-core coil in which an electric wire is wound in a cylindrical shape and nothing is put in the cylinder, and a core coil in which a winding is wound around a core. The core coil often uses ferrite, which is a magnetic material, and is called a ferrite coil. The air-core type is low in distortion but has a large loss and is not suitable for use in the printer 1. Therefore, as described below, a plurality of coils having different core materials were evaluated from the ferrite coils, and the types of core materials suitable for the coil L were examined.

  As the core material, there are generally three types: Mn—Zn-based ferrite (hereinafter simply referred to as “Mn—Zn-based”), Ni—Zn-based ferrite (hereinafter simply referred to as “Ni—Zn-based”), and dust core. Here, the dust core system is one using magnetic powder molded by a high-pressure press as a core material. FIG. 9 shows Rs measured for the coil using the above three types of core materials, and shows the difference in Rs depending on the types of core materials. Here, Rs is a resistance component of the coil, and includes a resistance component contributing to iron loss (core loss) and a resistance component contributing to copper loss (wire loss). In the following, “resistance component contributing to iron loss (core loss)” is simply “iron loss (core loss)” and “resistance component contributing to copper loss (wire loss)” is simply “copper. It may be expressed as “loss (loss of wire)”. Further, the resistance component includes a DC resistance of the coil (for example, about 2 mΩ), but it is sufficiently smaller (for example, two digits) than Rs, and may be excluded from the object of study.

  As shown in FIG. 9, a coil using an Mn—Zn core material (hereinafter also simply referred to as an Mn—Zn coil) is a coil using an Ni—Zn core material (hereinafter simply referred to as an Ni—Zn system). The value of Rs is larger than that of a coil using a dust core-based core material (hereinafter also simply referred to as a dust core-based coil). Although details will be described later, since an eddy current loss can be reduced when Rs is large, it is preferable to select a Mn—Zn-based coil as the coil L.

  Another feature of the core material is that the Ni—Zn coil has a low saturation magnetic flux density. This means that, for example, the number of turns needs to be increased as compared with other types of coils in order to obtain a desired inductance value. However, since a small coil L is used in the printer 1, it is difficult to significantly increase the number of turns. Therefore, the Ni—Zn coil is not appropriate as the coil L of the printer 1 from the viewpoint of the saturation magnetic flux density. When comparing the Mn—Zn coil and the dust core coil, the dust core coil generally tends to have a relatively large eddy current loss. Therefore, it can be said that it is preferable to select the Mn—Zn coil unless a dust core coil that sufficiently suppresses eddy current loss can be used.

Here, the value of Rs in FIG. 9 is an evaluation result when 4 MHz operation, that is, a pulse signal having a frequency of 4 MHz is applied to the Mn—Zn coil, Ni—Zn coil, and dust core coil, respectively. The frequency band of the AC component of the amplified modulated signal 128 is 1 MHz or more and less than 8 MHz, but in this frequency band, the Rs value of the Mn—Zn coil is relatively large.

  The reason why the frequency band of the AC component of the amplified modulated signal 128 is 1 MHz or more is as follows. 15 represents the result of frequency spectrum analysis of the pulse waveform in the original drive signal 125 (for example, a partial waveform of the original drive signal 125 corresponding to PCOM2 in FIG. 5). According to FIG. 15, it is known that a frequency of about 10 kHz to 400 kHz is included. In order to amplify by the signal amplifying unit 28 which is a digital power amplifying circuit and obtain the driving signal COM, it is necessary to drive the signal amplifying unit 28 at a switching frequency at least 10 times the frequency component included in the original driving signal 125. There is. If the switching frequency of the signal amplification unit 28 is less than 10 times the frequency spectrum included in the original drive signal 125, the high frequency spectrum component included in the original drive signal 125 cannot be modulated and amplified. The corner (edge) of the drive signal COM becomes dull and round. When the drive signal COM is dull, the movement of the piezoelectric element PZT that operates according to the rising and falling edges of the waveform becomes slow, and the discharge amount from the nozzle NZ may become unstable or may not discharge. . That is, unstable driving may occur. Here, according to FIG. 15, the high frequency spectrum component of the pulse waveform in the original drive signal 125 has a peak at about 60 kHz, and many components are below 100 kHz. Therefore, it is desirable to drive the signal amplifying unit 28 at a switching frequency of about 1 MHz, which is 10 times 100 kHz at the minimum.

  Here, the frequency component included in the original drive signal 125 varies depending on the size of the ink droplet to be ejected and the waveform of the original drive signal 125 corresponding to the size of the print dot. For example, a part of the waveform of the original drive signal 125 used in the spectrum analysis of FIG. 15 is the original drive signal 125 for ejecting an ink droplet having a size smaller than the standard, so that the vibration width is about as shown in FIG. It is as small as 2V. As described above, in order to eject a small-sized ink droplet, the piezoelectric element PZT is abruptly moved to eject a small amount of ink droplet. The drive signal COM for that purpose needs to contain a lot of high-frequency spectral components, and in order to perform high-speed printing, it is necessary to contain a lot of high-frequency spectral components for the convenience of moving the piezoelectric element PZT quickly. In other words, the required minimum frequency tends to increase as the high-speed and high-quality printing is pursued. The drive signal COM in the present embodiment is designed for use in general homes and offices, and prints an A4 size of about 5760 × 1440 dpi using 180 piezoelectric elements PZT. It is designed assuming that about 5 sheets are printed per minute.

  The reason why the frequency band of the AC component of the amplified modulated signal 128 is less than 8 MHz is as follows. If the switching frequency is high, switching at a high voltage and high frequency that drives the piezoelectric element PZT will increase the junction capacitance due to the structural reasons of the switching transistors (QH, QL), and noise will be generated. Various problems such as increase in switching loss due to high frequency driving. In particular, an increase in switching loss can be a big problem. In other words, an increase in switching loss may impair the merit of power saving and heat saving that the digital power amplifier circuit (digital amplifier) secures superiority compared to the class AB amplifier. It is.

  In the present embodiment, when compared with an analog amplifier (Class AB amplifier) that has been used in the past, a result that the digital amplifier is superior to 8 MHz was obtained, but at a frequency higher than that, This is because when a transistor is driven, a class AB amplifier may be superior.

The reason why it is preferable to select a Mn—Zn-based coil having a large Rs among the above three types will be described below with reference to FIGS. FIG. 10 is a diagram for explaining the ratio of iron loss and copper loss in Rs. The vertical axis (resistance value) in FIG. 10 uses a logarithmic scale.

  As described above, Rs is a resistance component of the coil including iron loss and copper loss. Rs represented by a solid line in FIG. 10 is based on data measured by an impedance analyzer. The amplified modulation signal 128 input to the coil L of the printer 1 can take a frequency in the range of Fmin to Fmax in FIG. 10 during normal operation in which the printer 1 performs printing. That is, in this embodiment, Fmin is 1 MHz and Fmax is about 8 MHz.

Here, the electrical resistance Rc of the copper loss in Rs is obtained by Expression (1) using the electrical resistivity ρ, the length L of the conductor, and the cross-sectional area S _{0 of the} conductor.

The copper loss represented by the dotted line in FIG. 10 indicates Rc in the formula (1). Therefore, in FIG. 10, the difference between the solid line Rs and the dotted line copper loss represents the iron loss. Here, since the vertical axis (resistance value) is a logarithmic scale, there is a relationship of iron loss >> copper loss in the frequency range of Fmin to Fmax, and the iron loss is dominant in the loss of the coil L in the printer 1. is there.

Here, the iron loss (W) is the sum of the hysteresis loss (W _h ) and the eddy current loss (W _e ), and can be expressed as the following equation (2).

In Equation (2), B _m is the magnetic flux density, K _h , K _e1 , η1, and η2 are constants, and f is the frequency of the signal of the coil L. Hysteresis loss (W _h ) is a loss that occurs when the direction of the magnetic field in the core changes. Since it occurs in proportion to the number of magnetic field changes, the hysteresis loss (W _h ) is proportional to the frequency (f). On the other hand, eddy current loss (W _e ) is a loss that occurs when an electromotive force is generated by electromagnetic induction due to a change in the magnetic field in the core and an induced current flows through the core. The magnitude of the eddy current flowing through the core is proportional to the magnetic field change speed, that is, the frequency (f). Since this is multiplied by the frequency (number of occurrences), the eddy current loss is proportional to the square of the frequency (f).

  FIG. 11A is a diagram for explaining the ratio between hysteresis loss and eddy current loss, and is based on the above equation (2). The printer 1 uses an amplified modulation signal 128 that is used in a high frequency range (Fmin to Fmax). Therefore, as shown in FIG. 11A, eddy current loss proportional to the square of the frequency (f) is dominant in the same range, and it can be said that most of the iron loss is eddy current loss.

  FIG. 11B is a diagram for explaining the eddy current EC. It is generated when an electromotive force is generated by electromagnetic induction due to a change in a magnetic field (dotted line in FIG. 11B) inside the core CM. Here, in order to suppress the eddy current loss, it is necessary to reduce the eddy current, that is, to select the material of the core CM having a large electric resistance. Therefore, eddy current loss can be suppressed by selecting a Mn—Zn coil having a large resistance component Rs from among Mn—Zn coils, Ni—Zn coils, and dust core coils. As described above, in the printer 1 using the amplified modulation signal 128 used in a high frequency range, iron loss is more dominant than copper loss, and eddy current loss is dominant among iron losses. Therefore, since the most dominant eddy current loss can be suppressed by selecting the Mn—Zn coil as the coil L, the heat generation / loss of the coil L is suppressed, and the low power consumption printer 1 is provided. Can do.

4.2. Coil selection 4.2.1. Selection Criteria Here, the coil L of the printer 1 constitutes a filter for smoothing the amplified modulated signal 128, but usually has a range of selection. For example, as shown in FIG. 12A, when there are coils L ₁ , L ₂ , and L ₃ that are all Mn—Zn coils, and any of them can satisfy desired filter characteristics, It is preferable that there is a criterion indicating whether it is optimal. Below, criteria for selection other than the type of core material will be examined.

FIGS. 12A and 12B are diagrams for explaining the correlation between Rs of the Mn—Zn-based coil and power consumption. FIG. 12A shows the result of measuring Rs of each of the _three coils L ₁ , L ₂ , and L ₃ that are Mn—Zn based coils. As shown in FIG. 12A, Rs increases in the order of the coils L ₁ , L ₂ , and L ₃ . As shown in FIG. 12B, the power consumption also increases in the order of the coils L ₁ , L ₂ , L ₃ . That is, as a result of experiments, it was found that there is a positive correlation between the resistance component Rs and the power consumption for the Mn—Zn coil.

  FIG. 12A and FIG. 12B both show measured values in the 4 MHz operation, but the above correlation does not change in the operation in the range of Fmin to Fmax. Further, as a result of further verification by increasing the number of samples, when a coil having an Rs of less than 200 mΩ was selected in 4 MHz operation, heat generation / loss was reduced and good results were obtained.

Therefore, an appropriate coil can be selected for the Mn—Zn-based coil by setting Rs to be less than 200 mΩ. According to this selection criterion, it is preferable to select the coil L ₁ having an Rs of less than 200 mΩ as shown in FIG. 12A among the coils L ₁ , L ₂ , and L ₃ .

4.2.2. Adjustment Method Next, a case where there is no coil that satisfies the above selection criteria will be considered. For example, it is assumed that there is no coil such as the coil L ₁ , but the coil L ₂ capable of adjusting the number of turns and the core gap CG can be used.

As described above, there is a relationship of iron loss >> copper loss in the frequency range of Fmin to Fmax, and eddy current loss is dominant as iron loss. Here, in the above formula (2), the constant η2 is specifically “2”, and the eddy current loss (W _e ) is proportional to the square of the magnetic flux density (B _m ). Therefore, it is effective to reduce the magnetic flux density (B _m ) in order to reduce the eddy current loss (W _e ).

The magnetic flux (Φ), the magnetic flux density (B _m ), and the inductance value (V _L ) are expressed by the following formulas (3), (4), and (5), respectively.

In Expressions (3) to (5), I is the current flowing through the coil, N is the number of turns, S ₁ is the cross-sectional area of the core, k is a proportionality constant determined by the shape of the coil, and μ _e is the effective permeability. According to the formulas (3) to (5), the magnetic flux density (B _m ) can be lowered by the following adjustment to the coil.

First, the magnetic flux density (B _m ) can be reduced by reducing the inductance value (V _L ) or the current (I) flowing through the coil. However, since the inductance value (V _L ) and the current (I) flowing through the coil are in an inversely proportional relationship, even if one is changed, the other cancels out, so the effect of lowering the magnetic flux density (B _m ) is small. .

Further, the magnetic flux density (B _m ) can be lowered by increasing the cross-sectional area (S ₁ ) of the core. However, there are many design restrictions such as an increase in coil mounting area and a decrease in the degree of freedom in coil design, which is not realistic.

Therefore, an adjustment method for reducing the magnetic flux density (B _m ) by reducing the effective magnetic permeability (μ _e ) can be considered. The effective magnetic permeability (μ _e ) changes with the change in the core gap CG of the coil, for example.

FIG. 13A is an external plan view of a coil (corresponding to the coil L ₂ described above), and FIG. 13B is a cross-sectional view taken along the line AA. As shown in FIGS. 13A and 13B, the coil body in which the wire is wound around the core CM is surrounded by the upper package Pu, the side package Ps, and the bottom package Pb. . The terminals T1 and T2 are connected to both ends of the coil wire. As shown in FIG. 13B, the gap between the core CM and the upper package Pu is the core gap CG.

FIG. 13C is an AA cross-sectional view showing a case where the core gap CG is widened. At this time, when the core gap CG increases, the effective magnetic permeability (μ _e ) decreases and the magnetic flux density (B _m ) also decreases.

However, as shown in the above equation (5), an increase in the number of turns (N) changes the inductance value (V _L ). If the inductance value (V _L ) changes, the characteristics of the smoothing filter may change. Therefore, it is preferable to adjust the number of turns (N) at the same time so as to maintain the inductance value (V _L ). In FIG. 13C, compared with the state of FIG. 13B, the core gap CG is widened and the number of turns is increased from 2 turns to 3 turns so that the inductance value (V _L ) is maintained. doing.

FIG. 14 is a diagram illustrating a change in the frequency-Rs characteristic due to a difference in the core gap CG and the number of turns of the coil. Characteristic curve CC0 indicated by a dotted line represents the characteristics of the coil (corresponding to the coil L ₂ above) prior to the adjustment of the core gap CG and turns. At this time, the Rs of the coil does not satisfy the above selection criterion of less than 200 mΩ in 4 MHz operation.

And the characteristic curve CC2 shown with the continuous line of FIG. 14 represents the characteristic at the time of extending the core gap CG to 1.1 mm. At this time, as the magnetic flux density (B _m ) decreases, Rs decreases to less than 200 mΩ at 4 MHz operation. However, since the inductance value (V _L ) is also reduced, it is necessary to adjust the inductance value (V _L ) to be the same as before the expansion of the core gap CG.

A characteristic curve CC1 indicated by a fine dotted line in FIG. 14 represents the characteristic when the number of turns is further increased to 3 turns and the inductance value (V _L ) is made the same as before the expansion of the core gap CG. Even in this case, Rs decreases to less than 200 mΩ at 4 MHz operation, and the heat generation / loss of the coil can be sufficiently reduced.

As described above, Rs can be sufficiently reduced by adjusting the core gap CG to 1.1 mm or more even for a coil that does not satisfy the above selection criteria. Further, by increasing the number of turns to 3 turns or more, it is possible to adjust to maintain the inductance value (V _L ), and even if this adjustment is performed, a state where Rs is sufficiently low (less than 200 mΩ) can be maintained. That is, Rs can be sufficiently reduced by the above adjustment method without affecting the characteristics of the smoothing filter.

  Here, in the present embodiment, the above adjustment method is described on the assumption that the coil is a Mn—Zn coil. However, the present invention is not limited to the Mn—Zn coil, but other types of coils (for example, a Ni—Zn coil). ) Is also applicable. The above formulas (3) to (5) do not depend on the type of coil, and the adjustment method described above is derived from studies based on the formulas (3) to (5). -It is applicable not only to Zn type coils but also to other types of coils.

  As described above, in a liquid jet printing apparatus using a high-frequency amplified modulation signal 128 such as the printer 1, the conversion efficiency can be reduced so as to suppress heat generation and loss when the amplified modulation signal 128 is smoothed. A high coil can be selected. First, by selecting a Mn—Zn-based coil, eddy current loss that occupies most of the iron loss can be suppressed, and heat generation and loss can be reduced. In addition, by using the selection criterion that Rs during operation at 4 MHz is less than 200 mΩ, a coil with low heat generation and loss can be selected based on the correlation between Rs and power consumption. Further, by adjusting the core gap CG to 1.1 mm or more, or by selecting such a coil, eddy current loss can be suppressed and heat generation / loss can be reduced. At this time, the inductance value can be maintained by adjusting the number of turns to 3 turns or more, or by selecting such a coil, and the filter characteristics are not affected. By using such a coil, it is possible to provide a liquid jet printing apparatus with low power consumption.

  The present embodiment is not limited to a line head type liquid ejecting apparatus (for example, a serial head type liquid ejecting apparatus), but may be the same as long as it is a liquid jet type printing apparatus using a high-frequency amplified modulation signal 128. An effect can be obtained.

5). Others The present invention includes configurations that are substantially the same as the configurations described in the above embodiments and application examples (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). The present invention also includes a configuration in which non-essential portions of the configuration described in the embodiments and the like are replaced. Further, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiments and the like, or a configuration that can achieve the same object. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiments and the like.

DESCRIPTION OF SYMBOLS 1 Printer, 10 Controller, 11 Interface part, 12 CPU, 13 Memory, 14 Drive signal generation part, 15 Control signal generation part, 16 Conveyance signal generation part, 20 Cable, 21 Winding axis, 22 Relay roller, 25 original drive signal generation Unit, 26 signal modulation unit, 28 signal amplification unit, 29 signal conversion unit, 30 paper transport mechanism, 31a driving roller, 31b driven roller, 32 relay roller, 33 relay roller, 34a driving roller, 34b driven roller, 35 comparator, 37 Error amplifier, 38 Gate drive circuit, 39 DAC, 40 Head unit, 41 Head, 42 Platen, 51 Wiper, 52 Cap, 53 Ink receiving part, 61 Relay roller, 62 Winding drive shaft, 70 Detector group, 80 Computer 111 print data 112 Amplification instruction signal, 113 storage medium, 125 original drive signal, 126 modulation signal, 128 amplification modulation signal, 201 selection switch, 211 shift register, 212 latch circuit, 213 level shifter, 402 ink supply path, 404 nozzle communication path, 406 elasticity Plate, C capacitor, CA cavity, CG core gap, CH channel signal, CM core, COM drive signal, EC eddy current, GH gate input signal, GL
Gate input signal, HC head controller, L coil, LAT latch signal, NZ nozzle, PCOM drive pulse, PZT piezoelectric element, Pb bottom package, Ps side package, Pu top package, QH switching element, QL switching element, Rc electricity Resistance, S paper, SCK clock signal, SI & SP drive pulse selection data, SI pixel data, SP waveform pattern data, T1 terminal, T2 terminal

Claims (6)

A signal modulation unit that generates a modulated signal by pulse-modulating the original drive signal;
A signal amplifier for amplifying the modulated signal to generate an amplified modulated signal;
A coil for smoothing the amplified modulated signal to generate a drive signal;
A piezoelectric element that is deformed when the drive signal is applied;
A cavity that expands or contracts due to deformation of the piezoelectric element;
A nozzle that communicates with the cavity and discharges liquid by increasing or decreasing the pressure in the cavity;
Have
The core material of the said coil is a Mn-Zn type ferrite, The liquid discharge apparatus characterized by the above-mentioned.   The liquid ejection apparatus according to claim 1, wherein the frequency band of the alternating current component of the amplification modulation signal is 1 MHz or more.   3. The liquid ejection apparatus according to claim 1, wherein the frequency band of the AC component of the amplified modulation signal is less than 8 MHz. The coil is
4. The liquid ejection device according to claim 1, wherein a resistance component including a core loss and a wire rod loss when operated at 4 MHz is less than 200 mΩ. 5. The signal modulator is
5. The liquid ejection apparatus according to claim 1, wherein the modulation signal is generated by feeding back the driving signal. 6. A piezoelectric element that deforms when a drive signal is applied;
A cavity that expands or contracts due to deformation of the piezoelectric element;
A nozzle that communicates with the cavity and discharges liquid by increasing or decreasing the pressure in the cavity;
Have
The piezoelectric element is
A head unit to which a drive signal generated by smoothing an amplified modulation signal is applied by a coil whose core material is Mn-Zn ferrite.