JP5807392B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection apparatus having an actuator including a piezoelectric layer.

  In the droplet discharge device of Patent Document 1, a piezoelectric actuator displaces a diaphragm and applies pressure to ink in a cavity. In Patent Document 1, by detecting a change in potential generated between drive electrodes that drive the piezoelectric actuator, residual vibration of the diaphragm is detected, and ink droplet ejection abnormality is detected.

JP 2005-305992 A

  In Cited Document 1, a change in potential between drive electrodes, that is, vibration generated in a piezoelectric layer sandwiched between drive electrodes is detected. On the other hand, a metal diaphragm is interposed between the piezoelectric layer and the cavity, and the vibration of the ink in the cavity is transmitted to the piezoelectric layer through the diaphragm. Therefore, if the vibration of the piezoelectric layer sandwiched between the drive electrodes is detected, it is difficult to accurately detect the vibration of the ink in the cavity.

  An object of the present invention is to provide a liquid ejection device that can accurately detect vibrations in a liquid in a liquid flow path.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a discharge port for discharging liquid and a liquid channel for supplying liquid to the discharge port, and a part of the liquid channel is on the surface. A plurality of layers that are stacked on the surface so as to straddle the opening of the liquid flow path, including a flow path unit that is open, a driving piezoelectric layer that converts voltage into a deformation force, and a detection piezoelectric layer that converts deformation into voltage A piezoelectric layer, and first and second drive electrodes sandwiching the drive piezoelectric layer and a detection electrode sandwiching the detection piezoelectric layer between the first and second drive electrodes with respect to the stacking direction of the piezoelectric layers. An actuator for applying pressure to the liquid in the liquid flow path based on a drive signal supplied between the first and second drive electrodes, and a drive signal supply means for supplying the drive signal to the actuator Any of the first and second drive electrodes A potential difference detection means for detecting a potential difference between the detection electrode and the detection electrode; and causing the drive signal supply means to supply the drive signal to the actuator and discharging the discharge port based on the potential difference detected by the potential difference detection means. A performance determination means for determining performance, wherein the drive signal supply means changes the potential difference between the first and second drive electrodes to the extent that liquid is discharged from the discharge port; A non-ejection drive signal that changes a potential difference between the first and second drive electrodes to such an extent that no liquid is ejected from the ejection port is selectively supplied to the actuator, and the drive piezoelectric element of the plurality of piezoelectric layers is selected. layers are stacked to be separated from most the channel unit, contact the detecting piezoelectric layer are laminated in the vicinity of the channel unit than any of the first and second driving electrodes A plurality of the discharge ports, a plurality of the actuators are provided corresponding to the plurality of discharge ports, and the first drive electrode is individually provided for each of the discharge ports, The second drive electrode and the detection electrode are provided in common across the plurality of actuators .
According to the second aspect of the present invention, the flow path unit has a discharge port for discharging a liquid and a liquid channel for supplying the liquid to the discharge port, and a part of the liquid channel is opened on the surface. A plurality of piezoelectric layers stacked on the surface so as to straddle the opening of the liquid flow path, and a driving piezoelectric layer that converts voltage into deformation force and a detection piezoelectric layer that converts deformation into voltage, The first and second drive electrodes sandwiching the drive piezoelectric layer and the detection electrode sandwiching the detection piezoelectric layer between the first and second drive electrodes with respect to the stacking direction of the piezoelectric layers, An actuator for applying pressure to the liquid in the liquid flow path based on a drive signal supplied between the first and second drive electrodes, drive signal supply means for supplying the drive signal to the actuator, Any one of the second drive electrodes and the detection electrode; A potential difference detection unit that detects a potential difference, and a performance determination that causes the drive signal supply unit to supply the drive signal to the actuator and determines the discharge performance of the discharge port based on the potential difference detected by the potential difference detection unit Means. The drive signal supply means includes a discharge drive signal for changing a potential difference between the first and second drive electrodes to the extent that liquid is discharged from the discharge port, and the first to the extent that liquid is not discharged from the discharge port. A non-ejection drive signal that changes a potential difference between the first and second drive electrodes is selectively supplied to the actuator, and the drive piezoelectric layer of the plurality of piezoelectric layers is farthest from the flow path unit. The detection piezoelectric layers are stacked so as to be closer to the flow path unit than any of the first and second drive electrodes. The detection electrode is grounded, and the second drive electrode is disposed between the detection electrode and the first drive electrode. Further, a switch that selectively takes a ground state in which the second drive electrode is grounded and an open state in which the second drive electrode is released from the ground state and electrically insulated, and the state of the switch is switched. Switch control means. When the performance determination unit determines the performance of the discharge port, the drive signal supply unit is configured to connect between the first drive electrode and the second drive electrode to which the switch in the ground state is connected. The non-ejection drive signal is supplied to the non-ejection drive signal, and the potential difference detection means detects a potential difference between the first drive electrode and the detection electrode following the supply of the non-ejection drive signal by the drive signal supply means. The switch control means sets the switch to the ground state when the drive signal supply means supplies the non-ejection drive signal, and sets the switch to the ground when the potential difference detection means detects a potential difference. Leave open.

According to the first and second aspects of the present invention, a detection electrode is provided separately from the two drive electrodes, and by detecting a potential difference between the drive electrode and the detection electrode, the liquid flow path is higher than that of the drive piezoelectric layer. The vibration of the detection piezoelectric layer close to can be detected. Thereby, the vibration in the liquid flow path can be detected with higher accuracy than when the vibration of the driving piezoelectric layer is detected.
In the second aspect, the voltage of the detection piezoelectric layer can be appropriately reflected in the detection voltage, and the residual vibration of the ink can be detected appropriately.

1 is a schematic side view showing an internal structure of an ink jet printer to which an ink jet head according to an embodiment of the present invention is applied. FIG. 2 is a schematic diagram illustrating a configuration of an ink supply unit that supplies ink from an ink cartridge to a head in FIG. 1. FIG. 2 is a plan view of a flow path unit that is a lower structure of the ink jet head of FIG. 1. It is an enlarged view of the range of the dashed-two dotted line IV of FIG. It is the VV sectional view taken on the line of the flow path unit of FIG. FIG. 6A is an enlarged view of the vicinity of the actuator unit of FIG. FIG. 6B is a plan view of the individual electrodes and lands. It is a block diagram which shows the structure of a control system. FIG. 8A is a schematic circuit diagram corresponding to the configuration and state of a control system that supplies a drive signal from the drive unit to the actuator via the driver IC. FIG. 8B is a schematic circuit diagram corresponding to the configurations and states of the actuator, the driver IC, and the detection unit when the drive signal is supplied. FIG. 9A is a schematic circuit diagram corresponding to the configurations and states of the actuator, the driver IC, and the drive unit when the detection signal is output. FIG. 9B is a schematic circuit diagram corresponding to the configuration and state of a control system that outputs a detection signal from the actuator to the drive unit via the driver IC. It is a longitudinal cross-sectional view corresponding to Drawing 6 (a) of an actuator unit and a channel unit concerning the 1st-the 3rd modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  First, an overall configuration of an ink jet printer 1 to which an ink jet head 2 according to an embodiment of the present invention is applied will be described with reference to FIG.

  The printer 1 includes a conductor casing 1a having a rectangular parallelepiped shape. Some of the components in the printer 1 are electrically connected to the housing 1a and are at the reference potential. Hereinafter, such a reference potential is referred to as “ground”. A paper discharge unit 31 is provided on the top of the casing 1a. In the following description, the internal space of the housing 1a is divided into spaces A, B, and C in order from the top. Spaces A and B are spaces in which a paper transport path that continues to the paper discharge unit 31 is formed. In the space A, the conveyance of the paper P and the recording of the image on the paper P are performed. In the space B, an operation related to paper feeding is performed. In the space C, an ink cartridge 40 as an ink supply source is accommodated.

  In the space A, there are arranged four inkjet heads 2, an ink supply unit 140 that supplies ink from the ink cartridge 40 to the head 2, a transport unit 21 that transports the paper P, a guide unit that guides the paper P, and the like. Yes. In the space A, a control unit 100 that controls the operation of each part of the printer 1 including these mechanisms and controls the operation of the entire printer 1 is arranged.

  The controller 100 synchronizes with the recording preparation operation, the paper P supply / conveyance / discharge operation, and the paper P conveyance so that an image is recorded on the paper P based on image data supplied from the outside. Controls discharge operation, recovery performance recovery operation, and the like.

  In addition to a CPU (Central Processing Unit) which is an arithmetic processing unit, the control unit 100 includes a ROM (Read Only Memory), a RAM (Random Access Memory: including a nonvolatile RAM), an ASIC (Application Specific Integrated Circuit), an I / O F (Interface), I / O (Input / Output Port), etc. The ROM stores programs executed by the CPU, various fixed data, and the like. The RAM temporarily stores data (for example, image data) necessary for executing the program. In the ASIC, image data is rewritten and rearranged (signal processing and image processing). The I / F performs data transmission / reception with a host device. I / O inputs / outputs detection signals of various sensors. The configuration of the control system shown in FIG. 7, which will be described later, is constructed by cooperation of these hardware, software stored in a ROM, and the like. Alternatively, a dedicated circuit or the like specialized for the function of the function unit illustrated in FIG. 7 may be provided as appropriate.

  Each head 2 is a line head having a substantially rectangular parallelepiped shape elongated in the main scanning direction (second direction). The four heads 2 are arranged at a predetermined pitch in the sub-scanning direction, and are supported by the housing 1a via the head frame 3. The head 2 includes a flow path unit 12 and four actuator units 120 (see FIG. 3). During image recording, magenta, cyan, yellow, and black inks are ejected from the lower surfaces (ejection surfaces 2a) of the eight heads 2, respectively. A more specific configuration of the head 2 will be described in detail later.

  As shown in FIG. 1, the transport unit 21 includes a belt roller 6, 7 and an endless transport belt 8 wound between both rollers 6, 7, and a nip roller 4 disposed on the outer side of the transport belt 8 and a peeling member. The plate 5 and the platen 9 disposed inside the conveyor belt 8 are included.

  The belt roller 7 is a driving roller and rotates clockwise in FIG. As the belt roller 7 rotates, the conveyor belt 8 travels in the direction of the thick arrow in FIG. The belt roller 6 is a driven roller and rotates clockwise in FIG. 1 as the transport belt 8 travels. The nip roller 4 is disposed to face the belt roller 6 and presses the paper P supplied from the upstream guide portion (described later) against the outer peripheral surface 8 a of the transport belt 8. The peeling plate 5 is disposed so as to face the belt roller 7, and peels the paper P from the outer peripheral surface 8 a and guides it to the downstream guide portion (described later). The platen 9 is disposed so as to face the four heads 2 and supports the loop upper portion of the conveyor belt 8 from the inside. Thus, a predetermined gap suitable for image recording is formed between the outer peripheral surface 8a and the ejection surface 2a of the head 2.

  The guide unit includes an upstream guide portion and a downstream guide portion disposed with the transport unit 21 interposed therebetween. The upstream guide portion has two guides 27 a and 27 b and a pair of feed rollers 26. The guide portion is along the conveyance path from the paper feeding unit 1b (described later) to the conveyance unit 21. The downstream guide portion has two guides 29 a and 29 b and two pairs of feed rollers 28. The guide unit is along a conveyance path from the conveyance unit 21 to the paper discharge unit 31.

  In the space B, the paper feeding unit 1b is arranged. The paper feed unit 1b has a paper feed tray 23 and a paper feed roller 25, and the paper feed tray 23 is detachable from the housing 1a. The paper feed tray 23 is a box that opens upward, and stores a plurality of types of paper P. The paper feed roller 25 feeds the uppermost paper P in the paper feed tray 23 and supplies it to the upstream guide unit.

  In the spaces A and B, as described above, a paper transport path from the paper feed unit 1b to the paper discharge unit 31 via the transport unit 21 is formed. When the control unit 100 drives the paper feed roller 25, the feed rollers 26 and 28, the transport motor 19 and the like based on the recording command, first, the paper P is sent out from the paper feed tray 23. The paper P is supplied to the transport unit 21 by the feed roller 26. When the paper P passes directly below each head 2 in the sub-scanning direction, ink is ejected from each ejection surface 2a, and a color image is recorded on the paper P. The paper P is then peeled off by the peeling plate 5 and conveyed upward by the two feed rollers 28. Further, the paper P is discharged from the upper opening 30 to the paper discharge unit 31.

  The sub-scanning direction is a direction parallel to the transport direction of the paper P by the transport unit 21, and the main scanning direction is a direction parallel to the horizontal plane and orthogonal to the sub-scanning direction.

  In the space C, the ink unit 1c is detachably arranged with respect to the housing 1a. The ink unit 1 c includes a cartridge tray 35 and four cartridges 40 accommodated in the tray 35 side by side. Each cartridge 40 supplies ink to the corresponding head 2 via an ink tube.

  Next, the configuration of the head 2 and the ink supply unit 140 will be described in more detail with reference to FIGS. In FIG. 3, the pressure chamber 16 and the aperture 15 which are located below the actuator unit 120 and should be indicated by dotted lines are indicated by solid lines.

  As shown in FIG. 2, the ink supply unit 140 connects the ink cartridge 40 and the head 2. The ink supply unit 140 is provided for each head 2 and includes an ink tube 141 and a pump 142 (discharge unit) provided in the middle thereof. The pump 142 forces ink from the ink cartridge 40 to flow into the head 2 and pressurizes the ink in the head 2. Thereby, when there is a foreign substance such as a bubble in the ink flow path of the head 2, the foreign substance can be discharged from the head 2 together with the ink. The pump 142 is stopped in a normal situation such as during printing processing or during standby. At this time, the pump 142 constitutes a part of the flow path, and when the ink is consumed by the head 2, the ink of the ink cartridge 40 is naturally supplied to the head 2 through the ink tube 141. At this time, the pump 142 is stopped in a state where ink can be circulated.

  As shown in FIGS. 2 and 3, the head 2 includes a reservoir unit 11, a flow path unit 12, and an actuator unit 120. An ink flow path 33 is formed inside the reservoir unit 11, and the ink flow path 33 and the ink cartridge 40 communicate with each other via the ink supply unit 140. The ink flow path 33 is branched downward into a plurality of outflow flow paths 33a. The outflow channel 33 a is open on the lower surface of the reservoir unit 11.

  The flow path unit 12 is a laminated body in which nine rectangular metal plates 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, and 12i (see FIG. 5) having substantially the same size are bonded to each other. As shown in FIG. 3, an opening 12 y is formed on the upper surface 12 x of the flow path unit 12. The opening 12 y is connected to the opening of the outflow channel 33 a and communicates with the ink channel 33. Inside the flow path unit 12, an ink flow path that is connected to the ejection port 14a from the opening 12y is formed. As shown in FIGS. 3 to 5, the ink flow path includes a manifold flow path 13 having an opening 12y as one end, a sub-manifold flow path 13a branched from the manifold flow path 13, and an outlet of the sub-manifold flow path 13a. An individual ink flow path 14 that reaches the discharge port 14 a via the pressure chamber 16 is included.

  The individual ink channel 14 is formed for each ejection port 14a, and includes an aperture 15 that functions as a throttle for channel resistance adjustment, and a pressure chamber 16 that opens to the upper surface 12x, as shown in FIG. As shown in FIGS. 4 to 6, the opening of the pressure chamber 16 has a substantially rhombus shape. A large number of pressure chambers 16 are arranged in a matrix on the upper surface 12x, and constitute a total of eight pressure chamber groups. Each pressure chamber group occupies a substantially trapezoidal region in plan view. The discharge ports 14a are also arranged in the same manner as the pressure chamber 16, and constitute a total of eight discharge port groups.

  As shown in FIG. 3, each of the actuator units 120 has a trapezoidal plane shape, and is arranged in two rows in a staggered pattern on the upper surface 12x. As shown in FIG. 4, each actuator unit 120 is disposed on a trapezoidal region occupied by a pressure chamber group (discharge port group). The size is slightly larger than the area where the pressure chamber group and the discharge port group are closed.

  A drive signal is supplied from the driver IC 132 (drive signal supply means) to the actuator unit 120 based on a control command from the control unit 100. The control unit 100, the driver IC 132, and the actuator unit 120 are connected to each other by the FPC 131. The FPC 131 is a flat flexible substrate provided for each actuator unit 120 and has a driver IC 132 mounted thereon. The FPC 131 is formed with various wirings for transmitting a drive signal to the actuator 120a described later, a detection signal from the actuator 120a, and the like. One end of the FPC 131 is provided with a connection terminal and is connected to the actuator unit 120.

  Next, the configuration of the actuator unit 120 will be described in more detail with reference to FIGS.

  As shown in FIG. 6A, the actuator unit 120 includes an individual electrode 123, a drive piezoelectric layer 121, a common electrode 124, a detection piezoelectric layer 122, and a detection electrode 125 stacked on the upper surface 12 x of the flow path unit 12 in order from the top. Is a laminated body. The individual electrode 123 and the common electrode 124 correspond to the first and second drive electrodes in the present invention in any order. Each actuator unit 120 is disposed across all the pressure chambers 16 included in one pressure chamber group while facing each other.

  The drive piezoelectric layer 121 and the detection piezoelectric layer 122 have the same size and a trapezoidal shape in plan view, and define the planar shape of the actuator unit 120. Both the drive piezoelectric layer 121 and the detection piezoelectric layer 122 are sheet-like members made of ceramics of lead zirconate titanate (PZT) having ferroelectricity. The drive piezoelectric layer 121 and the detection piezoelectric layer 122 are both polarized in the same direction as the stacking direction of the stacked body. In this embodiment, the drive piezoelectric layer 121 and the detection piezoelectric layer 122 have substantially the same thickness (15 μm).

  The common electrode 124 is formed over the entire upper surface of the detection piezoelectric layer 122, and the detection electrode 125 is formed over the entire lower surface of the detection piezoelectric layer 122. The individual electrode 123, the common electrode 124, and the detection electrode 125 are all made of Au (gold) and have a thickness of about 1 μm. The common electrode 124 is connected to the switch circuit 133 in a region not shown in FIG. 6 (see FIG. 8). The switch circuit 133 includes a ground state in which the common electrode 124 is connected to the housing 1a and grounded, and an open state in which the common electrode 124 is opened from the connection to the housing 1a and is electrically insulated from the housing 1a and other conductors. Take selectively. Switching of the state of the switch circuit 133 is performed by the driver IC 132. That is, the driver IC 132 functions as switch control means in the present invention.

  The detection electrode 125 is always grounded (see FIG. 8). The detection electrode 125 is bonded to the upper surface 12 x of the flow path unit 12 and seals the pressure chamber 16. The detection electrode 125 is connected to the wiring of the FPC 131 in a region not shown in FIG. This wiring is connected to the detection unit 103 described later via the driver IC 132.

  The individual electrodes 123 are arranged in a matrix like the pressure chambers 16. As shown in FIG. 6B, each individual electrode 123 includes a main part 123a and an extension part 123b. The main portion 123a has a rhombus shape similar to the pressure chamber 16 in a plan view, and is formed in the pressure chamber 16 to be slightly smaller than this. The extending portion 123b extends from one acute angle portion of the main portion 123a. The tip of the extension part 123 b is disposed outside the pressure chamber 16.

  A land 126 is formed at the tip of the extending portion 123b. The land 126 is made of a conductive material such as Ag—Pd (silver palladium), Au (gold), or Ag (silver). In the present embodiment, the land 126 is made of Ag—Pd. The land 126 has a cylindrical shape with a diameter of approximately 130 μm, and the upper end surface thereof is located at a position approximately 10 μm higher than the upper surface of the drive piezoelectric layer 121. The land 126 is connected to a connection terminal of the FPC 131 via a bump (not shown) formed on the upper surface. A drive signal from the driver IC 132 is supplied from the land 126 to the individual electrode 123 via the FPC 131.

  The actuator unit 120 applies pressure to the ink in the pressure chamber 16 when a drive signal is supplied from the driver IC 132. The piezoelectric layer that functions at this time is the driving piezoelectric layer 121. In the present embodiment, the individual electrode 123 and the common electrode 124 that are drive electrodes sandwich only the drive piezoelectric layer 121. The detection piezoelectric layer 122 is not used for driving. The driving piezoelectric layer 121 is deformed when a voltage is applied. That is, the voltage is converted into a deformation force (pressure applied to the ink). If the polarization direction and the electric field direction are the same in the driving piezoelectric layer 121, the portion facing the individual electrode 123 extends in the thickness direction (stacking direction) and contracts in the surface direction. On the other hand, when the detection electrode 125 is kept at the same potential as the common electrode 124, the detection piezoelectric layer 122 does not spontaneously deform. Therefore, a strain difference is generated between the drive piezoelectric layer 121 and the detection piezoelectric layer 122 in a region facing the individual electrode 123. At this time, the region sandwiched between the individual electrode 123 and the pressure chamber 16 is deformed into a convex shape (unimorph deformation) toward the pressure chamber 16. Such deformation can be performed for each individual electrode 123, that is, for each pressure chamber 16.

  As described above, the actuator unit 120 includes the individual actuators 120 a that can be driven for each pressure chamber 16. By driving each actuator 120a, the volume of the pressure chamber 16 changes. At this time, when the energy applied to the ink exceeds a predetermined level, the ink is ejected from the ejection port 14a corresponding to the pressure chamber 16.

  The actuator 120a of this embodiment has a function of detecting vibration generated in the ink in the individual ink flow path 14 in addition to the above function. The vibration generated in the ink is transmitted to the detection piezoelectric layer 122 through the detection electrode 125. At this time, the detection piezoelectric layer 122 is deformed according to the vibration of the ink and induces a voltage in the polarization direction. That is, the deformation is converted into a voltage. At this time, the drive piezoelectric layer 121 is also deformed together with the detection piezoelectric layer 122 and similarly induces a voltage. As a result, a potential difference is generated between the individual electrode 123 and the detection electrode 125. This potential difference corresponds to the sum of the voltages generated in both piezoelectric layers 121 and 122. By acquiring this change in potential difference, vibration of the actuator 120a, that is, vibration of the ink in the individual ink flow path 14 can be detected. A detection signal indicating the detected potential difference is output to the driver IC 132 via the FPC 132. This output signal is further output to the detection unit 103 described later. As described above, the driver IC 132 is also a potential difference detection unit that detects a potential difference between the individual electrode 123 and the detection electrode 125.

  Hereinafter, the configuration and control contents of the control system related to ink vibration detection will be described with reference to FIGS. This control system constitutes a part of the control unit 100, and as shown in FIG. 7, includes a drive unit 101, a vibration information storage unit 102, a detection unit 103 (performance determination means), a head pressurization control 104, and the like. The

  The drive unit 101 generates an actuator instruction signal and a drive signal based on the print command, the detection drive command, and the performance recovery command. The actuator instruction signal is a signal for driving the driver IC 132, and the actuator 120a to which the drive signal is to be supplied is selected. The drive signal is a signal for driving the actuator unit 120 and is supplied to the actuator 120 a selected by the driver IC 132. The drive signal includes an ejection drive signal and a non-ejection drive signal. When the ejection drive signal is applied between the drive electrodes 123 and 124, ink is ejected from the ejection port 14a. Even if the non-ejection drive signal is applied between the drive electrodes 123 and 124, only the meniscus of the ejection port 14a vibrates, and no ink is ejected. In the present embodiment, the ejection drive signal is used for the print command and the performance recovery command, and the non-ejection drive signal is used for the detection drive command.

  The vibration information storage unit 102 stores information related to ink vibration in the individual ink flow path 14. The vibration information is composed of a plurality of indices (value information such as period, amplitude, amplitude attenuation rate, etc.) characterizing the residual vibration, and is information on the residual vibration when the ejection characteristics are normal. This vibration information is information of a normal value (predetermined value) obtained from a result of supplying a non-ejection drive signal to the actuator 120a and measuring in advance the residual vibration generated in the corresponding individual ink flow path 14.

  The detection unit 103 controls the generation, detection, evaluation, and recovery processing based on the evaluation with respect to ink vibration. Upon occurrence of vibration, the detection unit 103 outputs a detection drive command to the drive unit 101. Upon detection and evaluation, the detection unit 103 directly outputs an actuator instruction signal (second instruction signal) to the driver IC 132 to specify a detection target. This actuator instruction signal instructs the driver IC 132 to perform a switch switching operation almost opposite to the actuator instruction signal from the drive unit 101. Further, the detection unit 103 compares each residual vibration index indicated by the detection signal with the vibration information stored in the vibration information storage unit 102, and identifies the detected residual vibration. In the recovery process based on the evaluation, the detection unit 103 outputs a performance recovery command to the drive unit 101. The recovery process is performed in cooperation with the drive unit 101 and a head pressurization control 104 described later.

  The head pressurization control 104 mainly controls the driving of the pump 142. When the pump 142 is driven, ink is forced to flow from the ink cartridge 40 to the head 2.

  The driver IC 132 includes three switch circuits 132a, 132b, and 133, as shown in FIGS. The switch circuit 132a selects the actuator 120a to be driven. The switch circuit 132b selects the detection target actuator 120a. The switch circuit 133 switches the electrical connection state of the common electrode 124 to the housing 1a.

  The control contents of the control system will be described. For example, when image formation is performed based on image data, a head control system (control system for controlling the head 2) functions. The head control system includes a driver IC 132 in addition to the drive unit 101. When a print command is input from the outside during image formation, the drive unit 101 generates a drive signal and an actuator instruction signal (first instruction signal). Both signals are generated based on the image data. At this time, the drive signal is an ejection drive signal and is supplied to the selected actuator 120a. The signal is supplied every printing cycle and is synchronized with the conveyance of the paper P.

  Here, the driver IC 132 selects the actuator 120a according to the actuator instruction signal. This selection operation includes disconnection of the detection system circuit (detection unit 103) and selective connection of the drive system circuit (drive unit 101) for the actuator 120a. As shown in FIG. 8B, the driver IC 132 opens all the detection target selection switch circuits 132b. Further, as shown in FIG. 8A, the switch circuit 133 is switched to the ground state, and only the designated switch circuit 132a is switched on (connected state). As a result, the ejection drive signal can be supplied only to the selected actuator 120a. Ink droplets are ejected from the ejection port 14a corresponding to the actuator 120a, and pixels (dots) constituting an image are formed on the paper P.

  The contents of control related to vibration detection will be described. At this time, in addition to the head control system, the vibration information storage unit 102, the detection unit 103 (performance determination unit), the head pressurization control 104, and the like operate in cooperation. The vibration detection operation proceeds in the order of ink vibration, its detection, and recovery processing based on the detection result.

  First, when ink vibrates, the detection unit 103 controls the driver IC 132 through the drive unit 101. The detection unit 103 outputs a detection drive command to the drive unit 101. This detection drive command instructs the actuator 120a to be detected to supply a drive signal for meniscus vibration. In response to this, the drive unit 101 outputs a drive signal and an actuator instruction signal to the driver IC 132. In this case, the drive signal is a non-ejection drive signal. As a result, the actuator 120a to be detected is driven to the extent that ink is not ejected. At this time, the operations of the switch circuits 132a, 132b, and 133 are the same as those in the above-described image formation. As a result, pressure is applied to the ink in the individual ink flow path 14 corresponding to the actuator 120a, and vibration occurs in the ink.

  Immediately thereafter, the vibration detection operation stops the vibration operation and moves to vibration detection. The detection unit 103 outputs an actuator instruction signal (second instruction signal) to instruct the detection target actuator 120a. The output destination of this signal is the driver IC 132. As shown in FIG. 9A, the driver IC 132 opens the switch circuit 133 and turns off all the switch circuits 132a. On the other hand, as shown in FIG. 9B, the driver IC 132 turns on only the switch circuit 132b indicated by the actuator instruction signal. At this time, the actuator 120a is disconnected from the drive system circuit to stop driving, and is selectively connected to the detection system circuit. The common electrode 124 is in an electrically floating state and is insulated from other conductors. Thus, the voltage generated between the individual electrode 123 and the detection electrode 125 is output to the detection unit 103 as a detection signal through the switch circuit 132b. Even after the drive of the actuator 120a is stopped, the vibration of the ink continues while being attenuated. This detection signal is a signal reflecting the residual vibration in the ink, and indicates a time change of the residual vibration.

  The detection unit 103 compares the vibration period and amplitude indicated by the detection signal with the normal value stored in the vibration information storage unit 102 to determine whether there is an abnormality in the residual vibration of the ink. Thus, the detection unit 103 functions as a comparison unit that compares the detection value with a predetermined value with respect to the period and amplitude. The cause of the abnormality in the residual vibration of the ink is, for example, a case where bubbles are generated in the individual ink flow path 14 or a case where the viscosity of the ink near the ejection port 14a is increased. In the former case, the vibration period becomes smaller and the amplitude becomes smaller than the normal value. In the latter case, the period of the residual vibration is increased and the amplitude is reduced as compared with the normal value. Based on this, when the detection value changes from the normal value, the detection unit 103 determines that there is an abnormality in the residual vibration of the ink, that is, there is an abnormality in the discharge performance of the ink from the discharge port 14a.

  When the detection unit 103 determines that there is an abnormality in the ejection performance, the detection unit 103 performs a performance recovery process for eliminating the abnormality. For example, when the period of the residual vibration is smaller than the normal value, the detection unit 103 outputs a performance recovery command to the head pressurization control unit 104. This performance recovery command includes information indicating the head 2 having an abnormal discharge performance. The head pressurization control unit 104 controls the pump 142 when a performance recovery command is input. As a result, ink is forcibly sent from the ink cartridge 40 to the head 2. Bubbles are discharged from the head 2 together with the ink, and the ejection performance is restored.

  On the other hand, when the period of the residual vibration is larger than the normal value, the detection unit 103 outputs another performance recovery command to the drive unit 101. This performance recovery command includes information indicating the discharge port 14a where the viscosity increase has occurred and the corresponding actuator 120a. When the performance recovery command is input, the drive unit 101 generates an actuator instruction signal and a drive signal. The actuator instruction signal is output to the driver IC 132. The drive signal is an ejection drive signal and is output to the selected actuator 120a via the driver IC 132. Here, the ejection drive signal is a signal for discharging the thickened ink near the ejection port 14a, and is different from the ejection drive signal at the time of image formation. Thereby, since the thickened ink in the vicinity of the ejection port 14a is ejected, the ejection performance is recovered.

  In addition, the cause of the abnormality in the ejection performance may not be determined depending on the period as described above, but may be determined depending on how the amplitude changes. For example, the separation may be performed based on the fact that the amplitude changes earlier or later than the normal value of the attenuation rate of the amplitude. Moreover, you may divide by evaluating both the magnitude of a period and the way of a change of an amplitude.

  According to the present embodiment described above, by detecting the potential difference between the individual electrode 123 and the detection electrode 125, it is possible to appropriately determine the ink ejection performance and execute various recovery processes. On the other hand, instead of the automatic processing by such an apparatus, for example, when the user of the printer 1 is requested to deal with based on an abnormality in the print image, the burden on the user is large. In this embodiment, not only the determination of the ejection performance but also the recovery process is performed on the apparatus side, so that the burden on the user can be greatly reduced.

  Further, since the detection electrode 125 is provided separately from the individual electrode 123 and the common electrode 124, the individual ink flow path is more than that of the driving piezoelectric layer 121 by detecting the potential difference between the individual electrode 123 and the detection electrode 125. The vibration of the detection piezoelectric layer 122 close to 14 can be detected. In this embodiment, since only the detection electrode 125 separates the detection piezoelectric layer 122 and the pressure chamber 16, the detection piezoelectric layer 122 is particularly close to the individual ink flow path 14. Thereby, the residual vibration of the ink can be detected with high accuracy.

  Further, since the detection electrode 125 covers the opening 16a of the pressure chamber 16 and separates the piezoelectric layer and the ink, it is possible to prevent the ink from penetrating into the piezoelectric layer and corroding it. Furthermore, since the piezoelectric layer is protected by the detection electrode 125 as compared with the case where the detection electrode 125 is not present and the piezoelectric layer is exposed, when the actuator unit 120 is bonded to the flow path unit 12, the foreign substance is bitten into the piezoelectric layer. The generation of cracks in the layer is suppressed.

  In the present embodiment, when determining the ejection performance, first, a non-ejection drive signal is supplied to the actuator 120a. Accordingly, since ink is not ejected when determining the performance, ink consumption is suppressed.

  Further, when detecting the residual vibration of the ink, the switch circuit 133 switches the common electrode 124 disposed between the individual electrode 123 and the detection electrode 125 from the grounded state to the opened state. On the other hand, when the common electrode 124 is constantly grounded or held at some constant potential, the voltage generated in the detection piezoelectric layer 122 is reflected in the potential difference between the individual electrode 123 and the detection electrode 125. Therefore, there is a possibility that the residual vibration of the ink cannot be detected properly. On the other hand, in this embodiment, the common electrode 124 is released from the ground, whereby the voltage of the detection piezoelectric layer 122 can be appropriately reflected in the detection voltage, and the residual vibration of the ink can be detected appropriately.

  In this embodiment, since the residual vibration of the ink can be detected for each actuator 120a, the recovery process can be executed for each head 2 or individual ink flow path 14 in which an abnormality has occurred as described above. Therefore, it is not necessary to perform unnecessary recovery processing such as ink discharge and ink ejection on the normal head 2 and the individual ink flow path 14, and wasteful power consumption and ink consumption can be avoided. The

  Hereinafter, various modifications according to the above-described embodiment will be described. The first to third modifications relate to the actuator unit 120. As shown in FIG. 10A, the actuator unit 220 according to the first modification is the above-described actuator unit 120 in which an additional piezoelectric layer 223 is interposed between the common electrode 124 and the detection piezoelectric layer 122. It is. Even in such a case, by detecting a potential difference between the individual electrode 123 and the detection electrode 125, it is possible to detect a voltage generated in the detection piezoelectric layer 122 and resulting from residual vibration of the ink. The piezoelectric layer 223 may or may not be polarized. That is, it may or may not be a piezoelectric layer related to ink vibration detection.

  As shown in FIG. 10B, the actuator unit 320 according to the second modified example includes an additional piezoelectric layer 323 between the detection piezoelectric layer 122 and the upper surface 12x of the flow path unit 12 in the actuator unit 120 described above. Is interposed. Even in such a case, by detecting a potential difference between the individual electrode 123 and the detection electrode 125, it is possible to detect a voltage generated in the detection piezoelectric layer 122 and resulting from residual vibration of the ink. Further, since the voltage generated in the detection piezoelectric layer 122 closer to the flow path unit 12 than the drive piezoelectric layer 121 is detected, the residual vibration of the ink can be detected with higher accuracy than when the voltage of the drive piezoelectric layer 121 is detected. The piezoelectric layer 323 may or may not be polarized, or may be a metal diaphragm instead of the piezoelectric layer.

  In the actuator unit 420 according to the third modification, as shown in FIG. 10C, the individual electrode 423 is disposed between the drive piezoelectric layer 121 and the detection piezoelectric layer 122, and the common electrode 424 is the drive piezoelectric layer 121. It is formed on the upper surface. The common electrode 424 is formed so as to avoid the periphery of the land 126 disposed on the upper surface of the drive piezoelectric layer 121. The individual electrode 423 has the same planar shape as that of the individual electrode 123, and is similarly disposed with respect to the pressure chamber 16. On the other hand, the tip of the extended portion 423 a corresponding to the extended portion 123 b and the land 126 are electrically connected by a wiring 426 that penetrates the drive piezoelectric layer 121. In this modification, the voltage generated in the drive piezoelectric layer 121 does not contribute to the potential difference between the individual electrode 423 and the detection electrode 125. For this reason, the vibration remaining in the drive piezoelectric layer 121 itself is suppressed from appearing as noise in the detection result, and the residual vibration of the ink can be detected with high accuracy. In this modification, since the common electrode 424 is not sandwiched between the individual electrode 423 and the detection electrode 125, the common electrode 424 may be always grounded.

  As shown in the first to third modifications, the present invention can be applied to actuator units having various configurations. However, the detection piezoelectric layer 125 needs to be disposed closer to the flow path unit 12 than either the individual electrode or the common electrode serving as the drive electrode.

  In the fourth modification, the ejection performance is determined immediately after the ejection drive signal is supplied to the actuator 120a. In the above-described embodiment, the determination is made immediately after the non-ejection drive signal is supplied. For example, even if the ejection performance is determined within the print processing period in which an image is formed on the paper P based on the image data. Good. Within the printing process period, after ink is ejected to form an image from a certain ejection port 14a, ink may not be ejected from that ejection port 14a for a predetermined period. When such a non-ejection period, that is, a non-ejection period from when an ejection drive signal is supplied to when the ejection drive signal is supplied for a certain actuator 120a is longer than a predetermined length, the detection unit 103 The discharge performance may be determined based on the detection signal output from the actuator 120a within the non-discharge period. The detection unit 103 acquires the non-ejection period based on the image data, and executes the above processing. The “predetermined length” may be a period extending over a plurality of continuous printing cycles or a period corresponding to one printing cycle. Here, the printing cycle corresponds to the time required for the paper P to be conveyed by a distance corresponding to one dot in the sub-scanning direction.

  In the present embodiment, an ejection signal composed of a plurality of pulses is used for ink ejection based on image data. In order not to affect the next ejection operation, the last of the ejection signal is composed of a cancel pulse for suppressing ink vibration. Here, in the fourth modification, from the viewpoint of improving detection sensitivity, it is preferable that the ejection drive signal related to vibration detection does not include a cancel pulse. Further, from the viewpoint of not including noise in the residual vibration, it is preferable to select a signal composed of only one ejection pulse as the ejection drive signal involved in vibration detection.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims.

  For example, in the above-described embodiment, the pump 142 that pressurizes the ink in the head 2 is used as one of the recovery processes of the ejection performance. However, a means for sucking ink from the ejection port 14a side may be used. For example, a capping unit that covers the discharge surface 2a may be provided, and a pump that sucks air between the capping unit and the coated discharge surface 2a may be provided. In the above-described embodiment, the ejection drive signal is supplied to the actuator 120a as one of the recovery processes, but a non-ejection drive signal may be supplied. As a result, the ink in the vicinity of the ejection port 14a vibrates and the viscosity is lowered.

  In the above-described embodiment, the recovery process is executed based on the result of determining the discharge performance. However, for example, the determination result may be displayed on a display provided on the front panel of the printer 1 to prompt the user to deal with an abnormality in ejection performance.

  The liquid discharge head according to the present invention is not limited to a printer, and can be applied to a liquid discharge apparatus such as a facsimile or a copier. Further, the number of liquid discharge heads applied to the liquid discharge apparatus is not limited to four, and may be one or more. The liquid discharge head is not limited to the line type, and may be a serial type. Furthermore, the liquid discharge head according to the present invention may discharge a liquid other than ink.

1 Inkjet printer (printer)
2 Inkjet head (head)
12 channel unit 14 individual ink channel 14a discharge port 16 pressure chamber 16a pressure chamber opening 100 control unit 101 drive unit 103 detection unit 104 head pressure control unit 120 actuator unit 120a actuator 121 drive piezoelectric layer 122 detection piezoelectric layer 123 individually Electrode 124 Common electrode 125 Detection electrode 132 Driver IC
133 Switch circuit 142 Pump

Claims (14)

A flow path unit having a discharge opening for discharging liquid and a liquid flow path for supplying liquid to the discharge opening, and a part of the liquid flow path being opened on the surface;
A plurality of piezoelectric layers stacked on the surface so as to straddle the opening of the liquid flow path; and a driving piezoelectric layer that converts voltage into deformation force and a detection piezoelectric layer that converts deformation into voltage, and the piezoelectric layer The first and second drive electrodes sandwiching the drive piezoelectric layer, and the detection electrode sandwiching the detection piezoelectric layer between the first and second drive electrodes. An actuator for applying pressure to the liquid in the liquid channel based on a drive signal supplied between the second drive electrodes;
Drive signal supply means for supplying the drive signal to the actuator;
A potential difference detecting means for detecting a potential difference between any one of the first and second drive electrodes and the detection electrode;
The drive signal supply means to supply the drive signal to the actuator, and based on the potential difference detected by the potential difference detection means, the performance determination means for determining the discharge performance of the discharge port,
The drive signal supply means includes a discharge drive signal for changing a potential difference between the first and second drive electrodes to the extent that liquid is discharged from the discharge port, and the first to the extent that liquid is not discharged from the discharge port. A non-ejection drive signal for changing a potential difference between the first and second drive electrodes is selectively supplied to the actuator;
Of the plurality of piezoelectric layers, the drive piezoelectric layer is stacked most distant from the flow path unit, and the detection piezoelectric layer is closer to the flow path unit than any of the first and second drive electrodes. Are stacked ,
A plurality of the discharge ports are provided,
A plurality of the actuators are provided corresponding to the plurality of discharge ports,
The first drive electrode is provided individually for each of the ejection openings,
The liquid ejection apparatus, wherein the second drive electrode and the detection electrode are provided in common across the plurality of actuators . The detection electrode is grounded;
The second drive electrode is disposed between the detection electrode and the first drive electrode,
A switch that selectively takes a ground state for grounding the second drive electrode and an open state for electrically insulating the second drive electrode from the ground state;
Switch control means for switching the state of the switch, and
When the performance determination means determines the performance of the discharge port,
The drive signal supply means supplies the non-ejection drive signal between the first drive electrode and the second drive electrode connected to the grounded switch, and the potential difference detection means Following the supply of the non-ejection drive signal by the signal supply means, a potential difference between the first drive electrode and the detection electrode is detected,
The switch control means sets the switch to the ground state when the drive signal supply means supplies the non-ejection drive signal, and sets the switch to the open state when the potential difference detection means detects a potential difference. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is a liquid ejecting apparatus. A flow path unit having a discharge opening for discharging liquid and a liquid flow path for supplying liquid to the discharge opening, and a part of the liquid flow path being opened on the surface;
A plurality of piezoelectric layers stacked on the surface so as to straddle the opening of the liquid flow path; and a driving piezoelectric layer that converts voltage into deformation force and a detection piezoelectric layer that converts deformation into voltage, and the piezoelectric layer The first and second drive electrodes sandwiching the drive piezoelectric layer, and the detection electrode sandwiching the detection piezoelectric layer between the first and second drive electrodes. An actuator for applying pressure to the liquid in the liquid channel based on a drive signal supplied between the second drive electrodes;
Drive signal supply means for supplying the drive signal to the actuator;
A potential difference detecting means for detecting a potential difference between any one of the first and second drive electrodes and the detection electrode;
The drive signal supply means to supply the drive signal to the actuator, and based on the potential difference detected by the potential difference detection means, the performance determination means for determining the discharge performance of the discharge port,
The drive signal supply means includes a discharge drive signal for changing a potential difference between the first and second drive electrodes to the extent that liquid is discharged from the discharge port, and the first to the extent that liquid is not discharged from the discharge port. A non-ejection drive signal for changing a potential difference between the first and second drive electrodes is selectively supplied to the actuator;
Of the plurality of piezoelectric layers, the drive piezoelectric layer is stacked most distant from the flow path unit, and the detection piezoelectric layer is closer to the flow path unit than any of the first and second drive electrodes. Are stacked,
The detection electrode is grounded;
The second drive electrode is disposed between the detection electrode and the first drive electrode,
A switch that selectively takes a ground state for grounding the second drive electrode and an open state for electrically insulating the second drive electrode from the ground state;
Switch control means for switching the state of the switch, and
When the performance determination means determines the performance of the discharge port,
The drive signal supply means supplies the non-ejection drive signal between the first drive electrode and the second drive electrode connected to the grounded switch, and the potential difference detection means Following the supply of the non-ejection drive signal by the signal supply means, a potential difference between the first drive electrode and the detection electrode is detected,
The switch control means sets the switch to the ground state when the drive signal supply means supplies the non-ejection drive signal, and sets the switch to the open state when the potential difference detection means detects a potential difference. A liquid discharge apparatus characterized by: When forming an image based on image data,
The switch control means sets the switch to the ground state,
The drive signal supply unit supplies the ejection drive signal corresponding to the image data between the first drive electrode and the second drive electrode connected to the switch in the ground state. The liquid discharge apparatus according to claim 2 or 3. The detection electrode, the liquid ejecting apparatus according to any one of claims 1-4, characterized in that in contact with said surface. The liquid ejection apparatus according to claim 5 , wherein the detection electrode covers the opening. When the performance determination unit determines the discharge performance of the discharge port, the drive signal supply unit supplies the non-ejection drive signal to the actuator, and then, based on the potential difference detected by the potential difference detection unit. apparatus according to any one of claim 1 6, wherein the determining. When the performance determination unit determines the discharge performance of the discharge port, the determination is made based on the potential difference detected by the potential difference detection unit after the drive signal supply unit supplies the discharge drive signal to the actuator. apparatus according to any one of claim 1 6, characterized in that. When the performance determination unit determines the discharge performance of the discharge port within a period of forming an image based on image data, immediately after the discharge drive signal is supplied to the actuator corresponding to the image data. Next, when the non-ejection period until the ejection drive signal is supplied to the actuator corresponding to the image data is equal to or longer than a predetermined length, the potential difference detected by the potential difference detection unit is detected in the non-ejection period. The liquid ejection apparatus according to claim 8 , wherein the determination is made based on the determination. The performance determining means is
2. A comparison means for determining which of at least one of a period and amplitude at which the potential difference detected by the potential difference detection means changes and a predetermined value corresponding thereto is larger. 10. The liquid ejection device according to any one of 9 above. The drive signal supply means supplies the ejection drive signal to the actuator when the comparison means determines that the period of change of the potential difference detected by the potential difference detection means is greater than the predetermined value. Item 11. The liquid ejection device according to Item 10 . A discharge means for forcibly discharging the liquid in the liquid channel from the discharge port;
When the comparison unit determines that the period of change of the potential difference detected by the potential difference detection unit is smaller than the predetermined value, the discharge unit discharges the liquid in the liquid channel without being based on the drive signal. the liquid ejection apparatus according to claim 10 or 11, characterized in that. The liquid ejecting apparatus according to claim 12 , wherein the ejecting unit pressurizes the liquid in the liquid flow path and forcibly ejects the liquid from the ejection port without driving the actuator. A plurality of the discharge ports, and a plurality of the actuators corresponding to the plurality of discharge ports,
Based on the result of determining the discharge performance for each of the discharge ports by the performance determination unit, the drive signal supply unit applies the discharge drive signal to the actuator corresponding to the discharge port for each of the discharge ports having deteriorated discharge performance. apparatus according to any one of claim 1 13, wherein the supplying.