JP6477297B2 - Electromechanical transducer drive device and droplet discharge device - Google Patents

Description

  The present invention relates to an electromechanical transducer drive device and a droplet discharge device.

  2. Description of the Related Art Conventionally, there is a droplet discharge device that discharges ink or functional liquid from a nozzle to form an image or a thin film layer. In a droplet discharge device, a droplet is discharged at a desired amount, timing, and speed by applying an appropriate pressure to a discharge target liquid supplied to a pressure chamber provided in communication with a nozzle.

  As one configuration for applying pressure to droplets, piezoelectric elements (piezo elements) are widely used. In a droplet discharge device using an electromechanical conversion element such as a piezoelectric element, a driving voltage having an appropriate waveform pattern is applied to an electromechanical conversion element provided along the wall surface of a pressure chamber or via a diaphragm. The pressure chamber is deformed by expanding and contracting the piezoelectric element to increase or decrease the pressure applied to the liquid inside.

  However, if a voltage having the same polarity is continuously applied to the electromechanical conversion element for a long time, the internal structure of the electromechanical conversion element gradually changes, and the characteristics such as the amount of deformation with respect to the applied voltage change. However, there is a problem that the amount of ejected ink changes and the image quality is affected.

  On the other hand, Patent Document 1 is provided with a circuit and a switch element for short-circuiting both ends of the piezoelectric element in common, and when no voltage is applied, the switching element is turned on so that both ends of the piezoelectric element are equipotential. The technology to be assumed is disclosed. In addition to the driving voltage supply source, Patent Document 2 includes a DC voltage supply source for bias that is supplied to the other end of the piezoelectric element, and a voltage supply source that is connected to both ends of the piezoelectric element by a switch element. A configuration is disclosed in which the ink discharge operation can be performed by switching.

JP 2014-19111 A JP 2010-105300 A

  However, the conventional technique has a problem that a plurality of voltage supply sources are required, leading to an increase in size and power consumption. In addition, as described above, when a change occurs in the characteristics related to the deformation amount with respect to the applied voltage, if a voltage of the same magnitude is applied positively and negatively with respect to a potential difference of zero, even if the change is slight, the liquid There is a problem that a relative difference occurs in the discharge amount of the droplets and a problem is likely to occur, and the labor for performing daily adjustment increases.

  An object of the present invention is to provide an electromechanical conversion element driving device and a droplet discharge device capable of appropriately controlling the droplet discharge amount while avoiding an increase in power consumption and size.

In order to achieve the above object, the invention according to claim 1
A device for driving an electromechanical transducer that deforms by applying a voltage to cause a pressure change in the liquid and discharges the liquid as a droplet from a nozzle,
A drive voltage output unit for generating and outputting a drive voltage signal to be supplied to the electromechanical transducer;
A polarity selection switching unit that switches a connection destination on the first end side of the electromechanical conversion element and a connection destination on the second end side opposite to the first end between the drive voltage output unit and the ground plane, respectively; ,
A mode setting unit for determining a connection state in the polarity selection switching unit by an input control signal;
A mode setting control means for controlling the operation of the mode setting unit by outputting a control signal to the mode setting unit to determine a connection destination on the first end side and a connection destination on the second end side;
Equipped with a,
The mode setting control means connects the drive voltage output unit and the first end side, and connects the second end side to the first polarity mode, and the drive voltage output unit and the second end side. Connecting and outputting a control signal corresponding to each of the second polarity modes for grounding the first end side,
One of the first polarity mode and the second polarity mode is selected for each output of the drive voltage signal corresponding to one waveform pattern.
It is characterized a call.

According to a second aspect of the present invention, in the electromechanical transducer drive device according to the first aspect,
A discharge selection switching element that is connected to the first end of the electromechanical conversion element and switches whether to apply a voltage to the electromechanical conversion element,
The polarity selection switching unit switches between the connection destination on the first end side and the connection destination on the second end side via the discharge selection switching element between the drive voltage output unit and the ground plane, respectively. It is a feature.

According to a third aspect of the present invention, in the electromechanical transducer driving device according to the first or second aspect,
The polarity selection switching unit is
A first drive switching element for switching presence / absence of connection between the drive voltage output unit and the first end side;
A second drive switching element for switching presence / absence of connection between the drive voltage output unit and the second end side;
A first ground switching element for switching presence / absence of connection between the ground plane and the second end side;
A second ground switching element for switching presence / absence of connection between the ground plane and the first end side;
It is characterized by having.

Further, the invention according to claim 4 is the electromechanical transducer drive device according to any one of claims 1 to 3 ,
The mode setting control means sets the polarity selection switching unit to the mode setting unit during the period in which an ejection drive voltage signal corresponding to a waveform pattern for ejecting droplets from the nozzle is supplied to the electromechanical conversion element. One of the first polarity mode and the second polarity mode is a predetermined polarity mode.

According to a fifth aspect of the present invention, in the drive device for the electromechanical transducer element according to the fourth aspect ,
The mode setting control means is configured to select the polarity by the mode setting unit in at least a part of a period during which a non-ejection driving voltage signal corresponding to a waveform pattern that does not eject droplets from the nozzle is supplied to the electromechanical transducer. The switching unit is characterized in that the other polarity mode is different from the one polarity mode.

According to a sixth aspect of the present invention, in the electromechanical transducer driving device according to the fifth aspect ,
The mode setting control unit is configured to perform a predetermined condition for each output of the non-ejection drive voltage signal corresponding to each selected waveform pattern during a period in which the non-ejection drive voltage signal is supplied to the electromechanical conversion element. The mode setting unit causes the polarity selection switching unit to be in the other polarity mode.

The invention according to claim 7 is the electromechanical transducer drive device according to any one of claims 1 to 6 ,
The mode setting unit does not connect the first end side to the drive voltage output unit and the ground plane at the same time, and does not connect the second end side to the drive voltage output unit and the ground plane at the same time. It has a limiting part.

The invention according to claim 8 is the electromechanical transducer drive device according to any one of claims 1 to 7 ,
The mode setting unit includes a grounding limiting unit that grounds neither the first end side nor the second end side when the driving voltage output from the driving voltage output unit is equal to or higher than a predetermined reference voltage. It is characterized by.

The invention according to claim 9 is the electromechanical transducer drive device according to any one of claims 1 to 6 ,
The mode setting unit is configured to switch the first end of the ejection selection switching element and the second end of the electromechanical conversion element when performing a switching operation between the first polarity mode and the second polarity mode. Both are characterized by passing through a non-connection state in which they are not connected to the drive voltage output section or the ground plane.

The invention according to claim 10
A drive device for an electromechanical transducer according to any one of claims 1 to 9 ,
A droplet discharge head comprising: a nozzle that discharges a droplet; and an electromechanical conversion element that is provided corresponding to the nozzle and is driven by the driving device;
An operation control unit for controlling the operation of the driving device;
A droplet discharge device comprising:

  According to the present invention, there is an effect that the droplet discharge amount can be appropriately controlled while avoiding an increase in power consumption and size.

1 is a block diagram illustrating a functional configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is a figure explaining the circuit structure which concerns on the voltage application to each piezoelectric element of a droplet discharge head. It is a figure which shows the circuit structure of the protection circuit in a polarity selection part. It is a figure which shows the example of switching to 1st polarity mode and 2nd polarity mode. It is a flowchart which shows the control procedure of a polarity mode switching process. It is a figure which shows the modification 1 of the protection circuit in a polarity selection part. It is a figure which shows the modification 2 and the modification 3 of the protection circuit in a polarity selection part. It is a figure which shows the time change of the control signal at the time of using the modification 3 of a protection circuit.

Hereinafter, embodiments of a droplet discharge device of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of a droplet discharge device 1 of the present embodiment.

  Here, the droplet discharge device 1 is, for example, an inkjet recording device that records an image by discharging ink onto a recording medium. The droplet discharge device 1 includes a control unit 41, a movement control unit 42, a movement operation unit 51, a communication unit 52, an operation display unit 53, a notification output unit 54, a head drive control unit 20, a droplet An ejection head 30 and the like are provided, and are connected via a bus 55 so that signals can be transmitted and received.

  The controller 41 controls the overall operation of the droplet discharge device 1. The control unit 41 includes a CPU 411 (Central Processing Unit), a RAM 412 (Random Access Memory), a storage unit 413, and the like.

  The CPU 411 performs various arithmetic processes. The CPU 411 reads out a control program stored in the storage unit 413 and performs various control processes related to image recording and setting thereof.

  The RAM 412 provides a working memory space to the CPU 411 and stores temporary data. The storage unit 413 includes a non-volatile memory that stores a control program, setting data, and the like. Further, the storage unit 413 may include a DRAM or the like that temporarily stores settings related to a droplet discharge command (print job) acquired from the outside via the communication unit 52, image data to be recorded, and the like.

The moving operation unit 51 moves the recording medium, which is a target for image recording, in a predetermined direction to move the recording medium with respect to the droplet discharge head 30, and performs at least operations related to supply and discharge of the recording medium. Examples of the moving operation unit 51 include an outer periphery of a cylindrical drum carrying a recording medium on the surface and a rotary motor that rotates around the surface of an endless belt. The moving operation unit 51 is only required to move the recording medium and the droplet discharge head 30 relative to each other, that is, the movement unit 51 can move relative to the recording medium on which the droplet discharge head 30 is stationary or moves. Also good.
The movement control unit 42 operates the movement operation unit 51 to perform a control operation for moving the carried recording medium at an appropriate timing and speed. The movement control unit 42 may have a common configuration with the control unit 41.

  The droplet discharge head 30 is provided with a plurality of nozzles arranged in a predetermined pattern, and records an image on a recording medium by discharging droplets, that is, ink at appropriate timing from the openings of the plurality of nozzles. To do. The arrangement pattern of the nozzles is not particularly limited, and may be a one-dimensional array or a two-dimensional array. The droplet discharge head 30 includes an electromechanical conversion element 31, a discharge selection switching element 32, and the like.

  The electromechanical transducer 31 is provided for each of a plurality of nozzles, and deforms in accordance with an applied voltage (drive voltage signal) to change the pressure applied to the liquid to be ejected, thereby ejecting droplets from the nozzles. It is an actuator to make it. Here, as the electromechanical conversion element 31, a piezoelectric element is used. The deformation mode of the piezoelectric element is not particularly limited as long as the applied voltage corresponds to the deformation amount of the piezoelectric element and the pressure applied to the ink changes according to the deformation.

  The ejection selection switching element 32 switches whether or not each electromechanical conversion element 31 is supplied with a drive voltage signal from the head drive control unit 20. The ejection selection switching element 32 switches the presence / absence of liquid droplet ejection from each nozzle by not causing the electromechanical conversion element 31 corresponding to the nozzle that does not eject liquid droplets to be supplied based on image data to be output. . In addition, this switching is not limited to the ejection of droplets, and is similarly applied to a drive voltage signal related to a non-ejection waveform that does not eject droplets.

  The head drive control unit 20 outputs a drive voltage signal that drives the electromechanical transducer 31 of the droplet discharge head 30 at an appropriate timing according to each pixel data of the output target image. The head drive control unit 20 may be formed collectively on a substrate or the like, or may be distributed and arranged in each part of the droplet discharge device 1. A part or all of the configuration of the head drive control unit 20 may be provided in the droplet discharge head 30. The head drive control unit 20 includes a head control unit 43, a drive voltage output unit 21, a polarity selection unit 22, and the like.

  The drive voltage output unit 21 outputs a drive voltage signal having a predetermined waveform pattern to each electromechanical conversion element 31 in accordance with a droplet discharge timing from the nozzle, a non-discharge state type, or the like. In the droplet discharge device 1 of the present embodiment, a trapezoidal driving voltage signal having a plurality of types of peak voltages is applied to the electromechanical transducer 31. The drive voltage output unit 21 converts the waveform pattern data held in advance into an analog voltage value, amplifies the power, and outputs the analog voltage value.

  The polarity selection unit 22 selects the direction (polarity) to which the drive voltage signal output from the drive voltage output unit 21 is applied to the electromechanical conversion element 31 and switches the circuit connection. The polarity selection unit 22 includes a polarity selection switching unit 220 and a mode setting unit 227. The circuit configuration of the polarity selector 22 will be described later.

The head control unit 43 controls the operation of the head drive control unit 20 in accordance with the presence / absence of image data to be recorded and the content of the image data. The head control unit 43 includes a CPU 431, a storage unit 432, and the like. Based on the image data to be recorded stored in the storage unit 432 or the storage unit 413, the CPU 431 sends a drive voltage signal having an appropriate waveform pattern to the head drive control unit 20 according to whether or not droplets are ejected from each nozzle. Is output at an appropriate timing according to a clock signal (synchronization signal) (not shown).
The head control unit 43 may be provided in common with the control unit 41.
The movement control unit 42 and the head control unit 43 constitute an operation control unit 40 related to image recording.
In addition, the drive device 10 for the electromechanical transducer 31 is configured by each configuration of the head drive controller 20 and the ejection selection switching element 32.

  The communication unit 52 communicates with an external device according to a predetermined communication standard, and transmits and receives data. As communication standards to be used, various standards such as TCP / IP by LAN (Local Area Network), short-range wireless communication such as wireless LAN, Bluetooth communication (registered trademark: Bluetooth), USB (Universal Serial Bus), etc. It is possible to use direct communication with an external device. The communication unit 52 receives a print job that is a command related to image recording from an external device, and outputs status information of the droplet discharge device 1 to the external device as necessary.

  The operation display unit 53 accepts user operations and displays information and menus for the user. As the operation display unit 53, for example, a display unit provided with an LCD (liquid crystal display) as the display unit 532 is used, and various menus and statuses related to image formation are displayed on the display screen of the LCD. In addition, a touch panel serving as the operation detection unit 531 is provided corresponding to the LCD, and the touch operation corresponding to the display on the display screen can be detected by arranging the touch panel on the LCD display screen. Alternatively, the operation display unit 53 may include a push button switch and detect a push operation of the push button switch.

  The notification output unit 54 performs a predetermined notification operation when an abnormality occurs in the droplet discharge device 1. Examples of the notification output unit 54 include a sound generation unit that generates a predetermined beep sound using a piezoelectric element or the like, and a light emitting unit that blinks or lights an LED lamp.

  Next, the configuration and operation related to droplet ejection from the droplet ejection head 30 in the droplet ejection apparatus 1 of the present embodiment will be described.

  FIG. 2 is a diagram illustrating a circuit configuration relating to voltage application to each electromechanical transducer 31 of the droplet discharge head 30 in the droplet discharge device 1 of the present embodiment.

  Each electromechanical conversion element 31 has an individual electrode (first end) connected to a discharge selection switching element 32. The opposite side of the discharge selection switching element 32 connected to the electromechanical conversion element 31 is connected to the first drive switching element 221 and the second ground switching element 223 of the polarity selection switching unit 220 in the polarity selection unit 22. . That is, the first end side of the electromechanical conversion element 31 is connected to the first drive switching element 221 and the second ground switching element 223 via the ejection selection switching element 32. In the electromechanical conversion element 31, the side opposite to the side (first end) connected to the discharge selection switching element 32 (second end side), that is, the common electrode is connected to the polarity selection unit 22 in the polarity selection switching unit 220. The two-drive switching element 222 and the first ground switching element 224 are connected.

The drive voltage Vd output from the drive voltage output unit 21 is input to the polarity selection unit 22 and connected to the droplet discharge head 30 in the first drive switching element 221 and the second drive switching element 222 via the mode setting unit 227. It is connected to the opposite side to the connected side. On the other hand, the opposite side of the second ground switching element 223 and the first ground switching element 224 to the side connected to the droplet discharge head 30 is grounded.
Thereafter, a part or all of the first drive switching element 221, the second drive switching element 222, the first ground switching element 224, and the second ground switching element 223 included in the polarity selection switching unit 220 are collectively switched. It is written as 224.

  The first drive switching element 221 and the first ground switching element 224 are synchronized on and off (connected state) based on a common control signal Cont1 input from the head control unit 43 (mode setting control means) to the mode setting unit 227. Can be switched. Here, the state in which the first drive switching element 221 and the first ground switching element 224 are turned on by the control signal Cont1 is referred to as a first polarity mode. The second drive switching element 222 and the second ground switching element 223 are switched on and off in synchronization based on a common control signal Cont 2 input from the head control unit 43 to the mode setting unit 227. Here, a state in which the second drive switching element 222 and the second ground switching element 223 are turned on by the control signal Cont2 is referred to as a second polarity mode.

  In this droplet discharge device 1, since all the switching elements 221 to 224 are not turned on at the same time, control is performed in association with each other so that the control signals Cont1 and Cont2 are not simultaneously activated. When the first driving switching element 221 and the second ground switching element 223 are simultaneously turned on or when the second driving switching element 222 and the first ground switching element 224 are simultaneously turned on, the driving voltage Vd is short-circuited to the ground. Such a short circuit is prevented by controlling the control signals Cont1 and Cont2. The drive voltage Vd can be supplied to one side of the electromechanical transducer 31 according to the activated one of the control signals Cont1 and Cont2, and the other side can be connected to the ground plane. In other words, the drive voltage Vd having the same magnitude can be applied to the electromechanical conversion element 31 according to the control signals Cont1 and Cont2 in both polarities.

Such limitation of the operation of the switching elements 221 to 224 can be performed not only by the CPU 431 of the head control unit 43 but also by hardware as a circuit.
FIG. 3 shows that the mode setting unit 227 of the polarity selection unit 22 includes a second drive switching element 222 and a first ground switching element 224 connected to the common electrode side (that is, the second end side of the electromechanical transducer 31). It is a figure which shows the circuit structure in the case of including the protection circuit 225 (a connection restriction | limiting part, a ground restriction | limiting part) for not turning ON simultaneously. Here, the configuration for the first drive switching element 221 and the second ground switching element 223 connected to the individual electrode side (the first end side of the electromechanical conversion element 31, that is, the ejection selection switching element 32) is omitted. However, a similar circuit configuration can be obtained.

  The head controller 43 operates the npn-type bipolar transistor Tr1 via the resistance element R11 by outputting a control signal Cont2 having a high level “H” in the active state (that is, active high). As a result, the current flowing through the resistance elements R13 and R12 and the bipolar transistor Tr1 causes both ends of the resistance element R13, that is, between the gate / source of the p-channel field effect transistor 222T (PMOS) forming the second drive switching element 222. A voltage difference is generated to turn on the field effect transistor 222T. As a result, the drive voltage Vd is output as the supply voltage Vcom to the common electrode. When the control signal Cont2 becomes low level “L” (inactive), the energization state of the bipolar transistor Tr1 and the field effect transistor 222T is turned off, and the output of the drive voltage Vd to the common electrode is cut off.

  On the other hand, the head controller 43 outputs a low level “L” control signal Cont1 in an inactive state to the AND circuit Ac1, and outputs a high level “H” control signal Cont1 in an active state (ie, Active high). When the control signal Cont1 at the low level “L” is output, the output of the inverting circuit Nc1 is always at the high level “H”. As a result, a collector current flows between the collector / emitter of the npn bipolar transistor Tr2, and the voltage supplied to the gate electrode of the n-channel field effect transistor 224T (NMOS) forming the first ground switching element 224 is the power supply voltage. It becomes lower than Vk. By setting the resistance value of the resistance element R22 so that this voltage is lower than the operating voltage of the field effect transistor 224T, the conduction between the source and drain of the field effect transistor 224T is cut off, and no current flows, and the common electrode Is not grounded.

  When the control signal Cont1 at the high level “H” is output from the head control unit 43 and the control signal Cont2 is at the low level “L”, the logical operation of the OR circuit Oc1, the AND circuit Ac1, and the inverting circuit Nc1. Therefore, a low level “L” is output to the base terminal of the npn-type bipolar transistor Tr2, and no collector current flows in the bipolar transistor Tr2. As a result, the power supply voltage Vk is supplied to the gate terminal of the field effect transistor 224T, and a current flows between the source / drain of the field effect transistor 224T due to the voltage difference with respect to the grounded source. Is supplied.

  Further, in the protection circuit 225, even when the control signals Cont1 and Cont2 are both at the high level “H”, when the drive voltage Vd is lower than the predetermined reference voltage Vref, the comparator Cp1 performs an OR circuit Oc1. The output of the inverting circuit Nc1 becomes a low level “L” in accordance with the comparison result input to, and a current flows between the source / drain of the field effect transistor 224T. That is, in the protection circuit 225, the second drive switching element 222 and the first ground switching element 224 can be simultaneously turned on only when the drive voltage Vd is lower than the reference voltage Vref. In this case, the reference voltage Vref is determined to be equal to or less than an upper limit value that does not cause destruction or the like in each component in the current path due to a short-circuit current flowing between the drive voltage Vd and the ground plane. When the control signals Cont1 and Cont2 are both unintentionally set to a high level “H” due to a failure of the head control unit 43 or a reset operation, or when the control signals Cont1 and Cont2 are intentionally set to high by maintenance or inspection. When the level is set to “H”, the protection circuit 225 suppresses a large current that causes destruction.

FIG. 4 is a diagram illustrating an example of switching between the first polarity mode and the second polarity mode.
The head controller 43 can perform this switching for each drive voltage signal corresponding to one waveform pattern. Here, the judgment for switching at the joints of the respective drive voltage signals such as timings t1, t2, and t3 is performed prior to the timing. The head controller 43 refers to the waveform pattern data corresponding to the next output drive voltage signal, and as shown in FIG. 4A, the drive voltage signal (discharge) related to the waveform pattern for discharging droplets from the nozzles. Drive voltage signal) (timing t2, peak voltage is VwH), the control signal Cont1 is set to the high level “H” and the control signal Cont2 is set to the low level “L”. As shown, the first polarity mode (one polarity mode) is set. Thus, when ink is ejected, the drive voltage signal is always supplied to the individual electrodes, and the common electrode is grounded.

  On the other hand, when the drive voltage signal does not cause the droplets to be ejected from the nozzle (non-ejection drive voltage signal) (timing t1, t3), the control signal Cont1 is set to the low level “L” and the control signal Cont2 is set to the high level “ H ”is appropriately assigned between the second polarity mode (polarity mode different from one polarity mode) set and the first polarity mode described above. In the second polarity mode, the individual electrodes are grounded, and the drive voltage Vd is supplied to the common electrode.

  The distribution of these polarity modes at the time of outputting the drive voltage signal related to the waveform pattern that does not eject droplets from the nozzles is made in advance so that the selection frequency of the first polarity mode and the selection frequency of the second polarity mode do not differ greatly. (Predetermined conditions) are determined. The drive voltage signal that does not cause the liquid droplets to be ejected from the nozzle is a small amplitude non-ejection signal (timing t1 to t2, peak output) that is output to cause the liquid (ink) in the nozzle to vibrate slightly while not ejecting the liquid droplets. Non-operation signal with a voltage of VwL smaller than VwH) and an amplitude of zero (after timing t3, constant at the bottom voltage VwB in the drive voltage signal related to the above-described droplet ejection or non-ejection), or a drive voltage for ejecting ink Preliminary drive voltage signal to preferentially vibrate the liquid prior to the signal, or to properly return the vibration of the liquid level in the nozzle after the drive voltage signal that caused the droplet to be ejected, etc. included.

FIG. 5 is a flowchart showing a control procedure by the head controller 43 of the polarity mode switching process executed in the droplet discharge device 1 of the present embodiment.
This polarity mode switching process is called when the droplet discharge head 30 is activated, and is continuously executed in parallel with the process related to the output of the drive waveform voltage. Or you may control collectively as a part of control process which concerns on the output of the drive voltage Vd.

  The head controller 43 (CPU 431) first determines whether or not it is a predetermined time before the joint of the drive voltage signal (step S101). If it is determined that it is not a predetermined time (“NO” in step S101), the head controller 43 repeats the process of step S101.

  If it is determined that the predetermined time has passed (“YES” in step S101), the head controller 43 acquires the type of the drive waveform pattern related to the drive voltage signal to be output next (step S102). The head controller 43 determines whether or not the drive waveform pattern is a waveform pattern related to ink ejection (step S103). If it is determined that the waveform pattern is related to ink ejection (“YES” in step S103), the head controller 43 sets the first polarity mode (step S104), and the timing of the joint of the drive voltage signal Then, if necessary, a control signal is output to the polarity selector 22 to change the connection to the first polarity mode. Then, the process of the head controller 43 returns to step S101.

  When it is determined that the waveform pattern is not related to ink ejection (“NO” in step S103), the head control unit 43 determines whether the setting frequency of the second polarity mode so far is equal to or lower than the upper limit. It discriminate | determines (step S105). This setting frequency is obtained, for example, by storing each setting number of times of the first polarity mode and the second polarity mode in the storage unit 432. If it is determined that it is not below the upper limit (“NO” in step S105), the processing of the head controller 43 proceeds to step S104.

  When it is determined that the setting frequency of the second polarity mode is equal to or lower than the upper limit (“YES” in step S105), the head controller 43 sets the second polarity mode (step S106), and the drive voltage signal If necessary, a control signal is output to the polarity selection unit 22 at the joint timing to change the connection state according to the second polarity mode. Then, the process of the head controller 43 returns to step S101.

[Modification]
The protection circuit 225 of the polarity selection unit 22 may be appropriately changed from the circuit configuration of the above embodiment.
FIG. 6 is a diagram illustrating a first modification of the protection circuit 225.
In the protection circuit 225a of the first modification, the comparator Cp1 is deleted from the protection circuit 225 of the above-described embodiment shown in FIG. 3, and the control signal Cont2 is inverted and input to the AND circuit Ac1 instead of the OR circuit Oc1. An inverting circuit Nc2 is provided. Other configurations are the same as those of the protection circuit 225 of the above-described embodiment, and detailed description thereof is omitted.

In the protection circuit 225a, when the control signal Cont2 is at the high level “H” and the field effect transistor 222T is turned on, the field effect transistor 224T is always turned off regardless of the control signal Cont1.
Similarly to the protection circuit 225 described above, the control signal Cont1 is set to the high level “H” only during the period when the control signal Cont2 is at the low level “L” and the field effect transistor 222T is turned off. The effect transistor 224T is turned on.

  That is, in the protection circuit 225a of the first modification, the circuit configuration prohibits the field effect transistor 222T and the field effect transistor 224T from being turned on simultaneously regardless of the control signals Cont1 and Cont2.

FIG. 7 is a diagram illustrating a second modification and a third modification of the protection circuit 225.
In the protection circuit 225b of Modification 2 shown in FIG. 7A, a logic circuit is not used.

  The field effect transistor 222T constituting the second drive switching element 222 is controlled to be turned on / off based on the control signal Cont2, similarly to the protection circuit 225 of the above embodiment. On the other hand, the voltage supplied to the gate terminal of the field effect transistor 224T constituting the first ground switching element 224 is the bipolar transistor Tr2 based on the comparison result between the drive voltage Vd and the reference voltage Vref2 in the comparator Cp2 and the control signal Cont1. It is controlled by turning on and off. In the protection circuit 225b of the second modification, the field effect transistor 224T is turned on when the control signals Cont1 and Cont2 are both at the low level “L” (that is, the control signal Cont1 is active low).

  In this case, when the field effect transistor 222T is turned on, the field effect transistor 224T is not turned on regardless of the control signal Cont1, so that the control signal Cont1 is at the low level “L” and the collector current of the bipolar transistor Tr2 Even if the current does not flow, the output voltage of the comparator Cp2, which is the voltage applied to the gate terminal of the field effect transistor 224T, needs to be set to the low level “L”. Accordingly, the resistance values of the resistance elements R12 and R13 are set so that the voltage between the resistance elements R12 and R13 having the maximum value assumed as the drive voltage Vd does not exceed the reference voltage Vref2. On the other hand, when the control signal Cont2 is at a low level and the control signal Cont1 is at a low level “L”, the field effect transistor 224T is reliably turned on, so the reference voltage Vref2 is the minimum value of the drive voltage Vd. Need to be set smaller. The power supply voltage supplied to the comparator Cp2 may be the drive voltage Vd.

  As shown in FIG. 7B, the protection circuit 225c of the third modification generates and outputs two control signals Cont1 and Cont2 by outputting a single control signal Cont-mode from the head control unit 43. To do.

  In the protection circuit 225c of Modification 3, the control signal Cont-mode output from the head control unit 43 is input via the NOR circuit NOc1 instead of being input directly to the resistance element R11 as the control signal Cont2. The control signal Cont-mode is divided into two, one is directly input to the NOR circuit NOc1 and the other is input to the NOR circuit NOc1 via the delay circuit 228. The delay circuit 228 outputs the delayed signal Cont-del after being delayed for a predetermined time. Then, the output of the NOR circuit NOc1 becomes the control signal Cont2.

  The control signal Cont1 is generated by the output of the NAND circuit NAc1 to which the control signal Cont-mode and the delay signal Cont-del are input, and is input to the resistance element R21. The circuit configuration relating to the signal path after input to the resistance element R21 is the same as that of the protection circuit 225 in the above embodiment. Therefore, in the third modification, the control signal Cont1 has an active low configuration.

  The output of the NOR circuit NOc1 of the control signal Cont-mode and the delay signal Cont-del is such that the control signal Cont-mode is switched from the high level “H” to the low level “L” or from the low level “L” to the high level “L”. After switching to “H”, the delay signal Cont-del becomes low level after a predetermined time delay and follows this switching, and the field effect transistor 222T is turned off. On the other hand, the output of the NAND circuit NAc1 of the control signal Cont-mode and the delayed signal Cont-del is at a high level from the switching of the control signal Cont-mode to the switching of the delayed signal Cont-del after a predetermined time delay. The field effect transistor 224T is also turned off. In other words, in the protection circuit 225c according to the third modification, neither the drive voltage Vd nor the ground voltage is connected (supplied) to the electromechanical transducer 31 during the switching between the first polarity mode and the second polarity mode. A period of state occurs. This more reliably prevents the occurrence of a short circuit.

  FIG. 8 is a diagram illustrating temporal changes in the control signals Cont-mode, Cont1, and Cont2 when the protection circuit 225c is used.

  When the control signal Cont-mode and the delay signal Cont-del are both the low level voltage VL, the control signal Cont1 and the control signal Cont2 are both the high level voltage VH, and the second driving switching element 222 (field effect transistor 222T). Is turned on, and the first ground switching element 224 (field effect transistor 224T) is turned off.

After the control signal Cont-mode is changed to the high level voltage VH, the control signal Cont2 is kept at the low level until the delay signal Cont-del output from the delay circuit 228 changes from the low level voltage VL to the high level voltage VH. While the field effect transistor 222T is turned off by changing to the voltage VL, the control signal Cont1 is maintained at the high level voltage VH, and the field effect transistor 224T is maintained in the off state.
When the delay signal Cont-del changes to the high level voltage VH, the control signal Cont2 is maintained at the low level voltage VL, and the control signal Cont1 changes to the low level voltage VL. As a result, the field effect transistor 224T is turned on.

  When the control signal Cont-mode returns to the low level voltage VL, only the control signal Cont1 changes to the high level voltage VH until the delay signal Cont-del returns from the high level voltage VH to the low level voltage VL. 224T is turned off. Thereafter, when the delay signal Cont-del becomes the low level voltage VL, the control signal Cont2 also changes to the high level voltage VH, and the field effect transistor 222T is turned on.

As described above, the driving device 10 for the electromechanical conversion element 31 in the droplet discharge device 1 of the present embodiment generates the drive voltage signal to be supplied to the electromechanical conversion element 31 and outputs the drive voltage output unit 21. The connection destination on the individual electrode side (first end side) of the electromechanical conversion element 31 and the connection destination on the common electrode side (second end side) opposite to the individual electrode side are respectively connected to the drive voltage output unit 21. A polarity selection switching unit 220 that switches between a ground plane and the polarity selection switching unit 220.
Accordingly, the polarity of the voltage applied to the electromechanical conversion element 31 can be appropriately reversed while avoiding an increase in power consumption and size, so that the deterioration of the characteristics of the electromechanical conversion element 31 with respect to the applied voltage can be suppressed appropriately. In addition, the droplet discharge amount can be controlled.

The electromechanical conversion element 31 includes an ejection selection switching element 32 that is connected to an individual electrode (first end) and switches whether to apply a voltage to the electromechanical conversion element 31. The connection destination on the individual electrode end side via the selective switching element 32 and the connection destination on the common electrode side (second end side) are switched between the drive voltage output unit 21 and the ground plane, respectively.
Thus, even when the discharge selection switching element 32 is sandwiched between the supply source of the applied voltage and the individual electrode, the polarity of the voltage applied to the electromechanical conversion element 31 can be similarly reversed. Therefore, it is possible to suppress the deterioration over time of the characteristics of the electromechanical transducer 31 with respect to the applied voltage. Further, by providing the discharge selection switch element 32, it is possible to easily perform control related to whether or not discharge is possible from a plurality of (many) nozzles.

  In addition, the polarity selection switching unit 220 includes a first drive switching element 221 that switches connection / non-connection between the drive voltage output unit 21 and the first end of the ejection selection switching element 32, and the drive voltage output unit 21 and the electromechanical conversion element 31. A second drive switching element 222 for switching presence / absence of connection to the second end, a first ground switching element 224 for switching presence / absence of connection between the ground plane and the second end of the electromechanical conversion element 31, a ground plane and a discharge selection switching element And a second ground switching element 223 for switching presence / absence of connection with the first end of 32. Thus, by providing four switching elements and switching each on / off, it becomes possible to switch easily. In particular, an analog switch such as a field effect transistor can be used with such a configuration of the switching element, so that the polarity can be switched at an appropriate timing by a small, high-speed and reliable switching operation.

In addition, a mode setting unit 227 that determines a connection state in the polarity selection switching unit 220 based on the input control signals Cont1, Cont2, and the like, a connection destination of the first end of the discharge selection switching element 32, and a second end of the electromechanical conversion element 31 A head control unit 43 that functions as a mode setting control unit that outputs control signals Cont1 and Cont2 that are determined in association with each other to the mode setting unit 227, and controls the operation of the mode setting unit 227.
Therefore, it becomes possible to switch the plurality of switching elements 221 to 224 in association with each other without any trouble.

  The head control unit 43 as a mode setting control unit connects the drive voltage output unit 21 and the first end of the ejection selection switching element 32, and a first polarity mode in which the second end of the electromechanical transducer 31 is grounded. And control signals Cont1 and Cont2 corresponding to the second polarity mode in which the drive voltage output unit 21 and the second end of the electromechanical conversion element 31 are connected and the first end of the discharge selection switching element 32 is grounded. To do. Therefore, it is possible to easily switch to the connection state by setting a mode corresponding to a desired connection state in the polarity selection switching unit 220. In particular, it is easy to switch to a preferable connection state with a small number of control signals.

In addition, the head control unit 43 as a mode setting control unit performs polarity by the mode setting unit 227 during the period in which the ejection drive voltage signal corresponding to the waveform pattern for ejecting droplets from the nozzles is supplied to the electromechanical transducer 31. The selection switching unit 220 is set to one predetermined polarity mode (here, the first polarity mode) of the first polarity mode and the second polarity mode.
As described above, the change in the characteristics of the electromechanical conversion element 31 is suppressed, and the deviation of the characteristics is suppressed to such an extent that the absolute value does not cause a problem. Therefore, it is possible to prevent a relative deviation in characteristics from affecting the ejected droplets due to the reversal of polarity. In addition, since adjustment such as application of a bias voltage for suppressing such a shift in relative characteristics can be avoided, control of the droplet discharge device 1 becomes easier.

  In addition, the head control unit 43 serving as a mode setting control unit performs mode setting in at least a part of a period during which the non-ejection driving voltage signal corresponding to the waveform pattern that does not eject droplets from the nozzles is supplied to the electromechanical transducer 31. The unit 227 causes the polarity selection switching unit 220 to switch to the other polarity mode (second polarity mode) different from the one polarity mode (first polarity mode) described above. As a result, the polarity of the applied voltage can be reversed at any time while the droplets are not being ejected between droplet ejection operations, so that it is easy and efficient without affecting the ejected droplets. The characteristic change of the electromechanical transducer 31 can be suppressed well. In particular, it is not necessary to perform voltage application with the polarity reversed separately during maintenance, start-up or termination, and the operation can be started and terminated quickly.

In addition, the head control unit 43 serving as a mode setting control unit outputs each non-ejection drive voltage signal corresponding to each selected waveform pattern during a period in which the non-ejection drive voltage signal is supplied to the electromechanical transducer 31. The polarity setting switching unit 220 is set to the second polarity mode by the mode setting unit 227 under a predetermined condition.
Accordingly, the polarity inversion is finely and frequently performed without affecting the drive voltage waveform, so that it can be quickly eliminated before the characteristic change becomes large.

  Further, the mode setting unit 227 includes the protection circuits 225, 225a to 225c, and the like, so that the first end of the ejection selection switching element 32 is not simultaneously connected to the drive voltage output unit 21 and the ground plane, and the electric machine The second end of the conversion element 31 is not simultaneously connected to the drive voltage output unit 21 and the ground plane. Accordingly, it is possible to prevent an abnormal operation of the CPU 431 of the head control unit 43 and a short circuit between the drive voltage output unit 21 and the ground plane due to an unintended output of the control signals Cont1, Cont2, etc. when the head control unit 43 is started up. Further, it is possible to prevent the discharge selection switching element 32 and the switching elements 221 to 224 from being damaged due to a large current.

  Further, the protection circuit 225 of the mode setting unit 227 shown in the first modification example is configured such that the first of the ejection selection switching elements 32 is output when the drive voltage Vd output from the drive voltage output unit 21 is equal to or higher than a predetermined reference voltage Vref2. Neither the end nor the second end of the electromechanical transducer 31 is grounded. Therefore, even when the control signals Cont1 and Cont2 are appropriately output, the switching elements 223 and 224 that generate a short-circuit current in a situation where a large drive voltage Vd can be connected to the first end or the second end of the polarity selection switching unit 220. By not turning on, failure of the switching elements 221 to 224 due to an unintended large current can be prevented more reliably.

  Further, the mode setting unit 227 including the protection circuit 225c according to the modified example 3 performs the first end of the ejection selection switching element 32 and the electromechanical conversion when performing the switching operation between the first polarity mode and the second polarity mode. Since the second end of the element 31 is not connected to the drive voltage output unit 21 or the ground plane, the switching elements to be switched are unintentionally connected simultaneously by the threshold voltages of the switching elements 221 to 224. Therefore, it is possible to prevent destruction of the switching elements 221 to 224 and the like due to a short circuit current.

  In addition, the droplet discharge device 1 of the present embodiment is provided in correspondence with the driving device 10 for the electromechanical conversion element 31 described above, a nozzle for discharging droplets, and the nozzle, and is driven by the driving device 10. A droplet discharge head 30 including a mechanical conversion element 31 and an operation control unit 40 that controls the operation of the driving device 10 are provided. That is, since it is possible to more easily suppress a change in characteristics caused by applying a voltage to the electromechanical conversion element 31 with only one direction of polarity, without increasing the power consumption or the size of the droplet discharge device 1. It is possible to stably perform appropriate and accurate droplet discharge over a long period of time compared to the conventional method without affecting the droplet discharge amount.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, the first drive switching element 221, the second drive switching element 222, the second ground switching element 223, and the first ground switching element 224 are connected to the drive voltage output unit 21 and the ground plane. Although the connection destination is determined, the configuration is not limited to using four switching elements. For example, instead of the first drive switching element 221 and the second drive switching element 222, a single switching element that alternatively determines the connection destination of the drive voltage output unit 21 may be provided. Alternatively, instead of the first drive switching element 221 and the second ground switching element 223, a single switching element that alternatively determines the connection destination of the first end of the ejection selection switching element 32 may be provided.

  In the above embodiment, field effect transistors are used as the first drive switching element 221, the second drive switching element 222, the first ground switching element 224, and the second ground switching element 223, but other analog switches are used. Alternatively, a switching element that can be switched mechanically may be used.

  In the above embodiment, the switching operation of each switching element 221 to 224 of the polarity selection unit 22 is performed by the control operation of the CPU 431 of the head control unit 43, but information regarding the waveform pattern to be output next is input. The switching elements 221 to 224 may be switched without using a CPU process using a logic circuit.

  Further, in addition to or instead of the case where the polarity is appropriately reversed by the processing of the head controller 43, the user can manually reverse the polarity to operate the driving device 10.

  Further, the criterion for switching between the first polarity mode and the second polarity mode at the time of outputting a drive voltage signal that does not cause droplets to be ejected may be different from the criterion in the above embodiment. For example, in the case of a non-ejection drive voltage signal, the second polarity mode may be set, and in the case of a constant voltage signal, the first polarity mode may be set.

  In the above-described embodiment, the case where the polarity is reversed during the non-ejection operation period between the droplet ejection operations has been described as an example. The polarity of the applied voltage may be reversed when no droplet is ejected or when a large problem does not occur in the variation of the droplet ejection amount due to the droplet ejection operation for clogging prevention.

  In the above embodiment, the first polarity mode and the second polarity mode are inverted at the connection between the waveform patterns in the drive voltage signal in the non-ejection operation period. However, the drive voltage corresponding to one waveform pattern is used. Inversion in the middle of the signal is not uniformly prohibited. In addition, the number of waveform patterns that can be output in the second polarity mode in advance is determined in advance, and when switching to a droplet discharge operation in the middle or when a drive voltage signal is supplied according to the number of waveform patterns. Only when it is finished, the next polarity may be determined.

  In the above embodiment, an example in which the ejection selection switching element 32 that determines whether or not ink is ejected from a plurality of nozzles is provided has been described. However, the electromechanical conversion is performed without using the ejection selection switching element 32. A drive voltage signal corresponding to the ink ejection state may be individually supplied to the element 31. In this case, the first drive switching element 221 and the second ground switching element 223 are directly connected to the individual electrodes. Further, the number of nozzles and the corresponding electromechanical transducer 31 may be one.

  Further, the protection circuit 225 and the like described in the above embodiment may not be provided, or may be another known circuit configuration that functions in the same manner.

  In the above embodiment, the protection circuit 225c describes an example in which a non-connection state that is neither the first polarity mode nor the second polarity mode occurs in the circuit configuration. A state may be set.

  Further, as the electromechanical conversion element, in addition to a piezoelectric element, the present invention can be applied to an electrostrictive element that can be similarly deformed and whose characteristics related to the deformation can be changed.

In the above embodiment, an ink jet recording apparatus that ejects ink onto a recording medium has been described as an example of a droplet ejecting apparatus. However, other functional liquids may be ejected, wiring of a thin film layer or an electric circuit, The present invention is also applied to a droplet discharge device, a 3D printer, or the like that discharges a material for forming a terminal or the like onto a substrate, or discharges a liquid sample used for an experiment or inspection onto an inspection plate. I can do it.
In addition, the specific details shown in the above embodiment can be appropriately changed without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Droplet discharge device 10 Drive apparatus 20 Head drive control part 21 Drive voltage output part 22 Polarity selection part 220 Polarity selection switching part 221 1st drive switching element 222 2nd drive switching element 222T Field effect transistor 223 2nd ground switching element 224 First ground switching element 224T Field effect transistor 225 Protection circuit 225a Protection circuit 225b Protection circuit 225c Protection circuit 227 Mode setting unit 228 Delay circuit 30 Droplet discharge head 31 Electromechanical transducer 32 Discharge selection switching element 40 Operation control unit 41 Control unit 411 CPU
412 RAM
413 Storage unit 42 Movement control unit 43 Head control unit 431 CPU
432 Storage unit 51 Moving operation unit 52 Communication unit 53 Operation display unit 531 Operation detection unit 532 Display unit 54 Notification output unit 55 Bus Ac1 AND circuit Cont-mode Control signal Cont-del Delay signal Cont1 Control signal Cont2 Control signal Cp1 Comparator Cp2 Comparator NAc1 NAND circuit Nc1 Inverter circuit Nc2 Inverter circuit NOc1 NOR circuit Oc1 OR circuit R11 Resistor element R12 Resistor element R13 Resistor element R22 Resistor element Tr1 Bipolar transistor Tr2 Bipolar transistor Vcom Supply voltage Vd Drive voltage VH High Level voltage Vk Power supply voltage VL Low level voltage Vref Reference voltage Vref2 Reference voltage

Claims (10)

A device for driving an electromechanical transducer that deforms by applying a voltage to cause a pressure change in the liquid and discharges the liquid as a droplet from a nozzle,
A drive voltage output unit for generating and outputting a drive voltage signal to be supplied to the electromechanical transducer;
A polarity selection switching unit that switches a connection destination on the first end side of the electromechanical conversion element and a connection destination on the second end side opposite to the first end between the drive voltage output unit and the ground plane, respectively; ,
A mode setting unit for determining a connection state in the polarity selection switching unit by an input control signal;
A mode setting control means for controlling the operation of the mode setting unit by outputting a control signal to the mode setting unit to determine a connection destination on the first end side and a connection destination on the second end side;
Equipped with a,
The mode setting control means connects the drive voltage output unit and the first end side, and connects the second end side to the first polarity mode, and the drive voltage output unit and the second end side. Connecting and outputting a control signal corresponding to each of the second polarity modes for grounding the first end side,
One of the first polarity mode and the second polarity mode is selected for each output of the drive voltage signal corresponding to one waveform pattern.
Driving device for an electromechanical transducer, wherein the this. A discharge selection switching element that is connected to the first end of the electromechanical conversion element and switches whether to apply a voltage to the electromechanical conversion element,
The polarity selection switching unit switches between the connection destination on the first end side and the connection destination on the second end side via the discharge selection switching element between the drive voltage output unit and the ground plane, respectively. The drive device for an electromechanical transducer according to claim 1. The polarity selection switching unit is
A first drive switching element for switching presence / absence of connection between the drive voltage output unit and the first end side;
A second drive switching element for switching presence / absence of connection between the drive voltage output unit and the second end side;
A first ground switching element for switching presence / absence of connection between the ground plane and the second end side;
A second ground switching element for switching presence / absence of connection between the ground plane and the first end side;
The drive device for an electromechanical transducer according to claim 1 or 2, further comprising: The mode setting control means sets the polarity selection switching unit to the mode setting unit during the period in which an ejection drive voltage signal corresponding to a waveform pattern for ejecting droplets from the nozzle is supplied to the electromechanical conversion element. 4. The electromechanical conversion element driving device according to claim 1, wherein one of the first polarity mode and the second polarity mode is set to a predetermined polarity mode. 5. The mode setting control means is configured to select the polarity by the mode setting unit in at least a part of a period during which a non-ejection driving voltage signal corresponding to a waveform pattern that does not eject droplets from the nozzle is supplied to the electromechanical transducer. 5. The drive device for an electromechanical transducer according to claim 4 , wherein the switching unit is set to the other polarity mode different from the one polarity mode. The mode setting control unit is configured to perform a predetermined condition for each output of the non-ejection drive voltage signal corresponding to each selected waveform pattern during a period in which the non-ejection drive voltage signal is supplied to the electromechanical conversion element. 6. The drive device for an electromechanical transducer according to claim 5, wherein the polarity selection switching unit is set to the other polarity mode by the mode setting unit. The mode setting unit does not connect the first end side to the drive voltage output unit and the ground plane at the same time, and does not connect the second end side to the drive voltage output unit and the ground plane at the same time. The drive device for an electromechanical transducer according to claim 1 , further comprising a limiting unit. The mode setting unit includes a grounding limiting unit that grounds neither the first end side nor the second end side when the driving voltage output from the driving voltage output unit is equal to or higher than a predetermined reference voltage. The drive device for an electromechanical transducer according to any one of claims 1 to 7 . When the mode setting unit performs the switching operation between the first polarity mode and the second polarity mode, both the first end side and the second end side are the drive voltage output unit or the ground plane. The electromechanical transducer drive device according to any one of claims 1 to 6, wherein a non-connection state in which no connection is made is passed. A drive device for an electromechanical transducer according to any one of claims 1 to 9 ,
A droplet discharge head comprising: a nozzle that discharges a droplet; and an electromechanical conversion element that is provided corresponding to the nozzle and is driven by the driving device;
An operation control unit for controlling the operation of the driving device;
A droplet discharge apparatus comprising:

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