JP2010076329A - Electric current detecting sensor board, capacitive load driving apparatus, liquid discharging head driving apparatus, and liquid discharging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric current detecting sensor board which can detect a driving current without affecting a driving signal, and to provide a capacitive load driving apparatus, a liquid discharging head driving apparatus, and a liquid discharging apparatus. <P>SOLUTION: An electric current detecting section 92 is installed as a means for detecting the electric current of a driving signal wire 130 which transmits the driving signal. The electric current detecting section 92 includes a detecting signal wire 147 which is arranged to be proximal to the driving signal wire 130 through a dielectric body. Since the driving signal wire 130 and the detecting signal wire 147 are combined through an electromagnetic field, an induction current is derived to the detecting signal wire 147 in response to the change of the current which flows in the driving signal wire 130. The detecting signal which is taken out from the detecting signal wire 147 is converted into a voltage with a voltage converting section 150, and is transmitted to a deciding section 96 after an amplifying process is further applied with an amplifying section 152. At the deciding section 96, the presence/absence of a short-circuiting and disengagement of the driving signal wire 130, and the presence/absence of a displacement in the capacitance of a piezoelectric element 58 are decided conforming to the detecting signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current detection sensor substrate, a capacitive load driving device, a liquid ejection head driving device, and a liquid ejection device, and more particularly to a technology for detecting a driving current when driving a capacitive load such as a piezoelectric actuator.

  In general, an inkjet recording apparatus is widely used as a general-purpose image forming apparatus for forming a color image. The ink jet recording apparatus includes, for example, an ink jet head corresponding to each color of K (black), C (cyan), M (magenta), and Y (yellow), and discharges color ink from each head provided for each color. Thus, a desired color image is formed on the recording medium.

  Ink jet heads are provided with ejection force generating elements such as piezoelectric actuators (piezo actuators) corresponding to a large number of nozzles. When a predetermined drive signal is applied to each of the ejection force generating elements, A predetermined amount of ink is ejected at a predetermined timing.

  In this specification, a structure in which both surfaces of a piezoelectric layer are sandwiched by electrodes is called a piezoelectric element or a piezoelectric element, and a structure in which a structural member such as a deformation plate is joined to a piezoelectric element (piezo element) is a piezoelectric actuator (piezo element). Actuator).

  Here, a drive circuit for generating a drive signal to be applied to a piezo actuator (piezoelectric actuator) according to the prior art will be described with reference to FIG.

  As shown in the figure, the inkjet head 300 is provided with piezoelectric actuators 302 corresponding to a large number of nozzles (not shown). The piezoelectric actuator 302 is provided with an electrode (not shown) to which a drive signal is applied. The electrode is connected to a drive circuit 320 via a wiring pattern including a drive signal line (and a return signal line) formed on the flexible flat substrate 304. The output unit 366 is connected to the output unit 366.

  When the drive circuit 320 is operated to output a drive signal having a predetermined drive waveform, the drive signal is transmitted to the piezo actuator 302 via the flexible flat substrate 304.

  The operation of the drive circuit 320 shown in FIG. 15 will be briefly described. A digital data sequence (waveform data sequence) 326 is sequentially read out from the waveform data storage unit 324 that stores the drive waveform, converted into an analog signal by the D / A converter 328, and the analog signal is amplified by the operational amplifier 330. The

A boost circuit 335 including a configuration in which transistors 332 and 334 are connected to a totem pole through a predetermined input circuit 331 is connected to the output of the operational amplifier 330, and a driving power supply unit (+ V) that is a driving source of the piezo actuator 302 is connected. ₂ ), a large output current for driving the piezo actuator 302 can be supplied. This is because the piezoelectric actuator 302 is electrically equivalent to a capacitor, and when a voltage pulse signal (driving signal) is given to the piezoelectric actuator 302, the piezoelectric actuator 302 that is electrically equivalent to the capacitor is charged and discharged. This is because it is necessary to flow a large current instantaneously. A DC voltage of 20V to 30V is applied to the drive voltage + V ₂ of the piezo actuator 302.

Further, the drive circuit 320 includes resistors 336 and 338 constituting a feedback circuit of an amplifier circuit including the operational amplifier 330 and the boost circuit 335. Further, one terminal of the input circuit of the boost circuit 335 is connected to the low voltage source + V ₁ . A resistor 342 connected and having the other terminal connected to the base terminal of the transistor 332, a resistor having one terminal connected to the negative voltage source -V and the other terminal connected to the base terminal of the transistor 334 344, a diode 346 having one terminal connected to the base of the transistor 332 and the other terminal connected to the output of the operational amplifier 330, one terminal connected to the base of the transistor 334 and the other terminal connected to the output of the operational amplifier 330. Comprising a diode 348 connected to the output The

  Inside the inkjet head 300, piezoelectric actuators 302 corresponding to the respective nozzles (not shown) are formed, and the analog switches 350 are individually connected. One side of the analog switch 350 is connected to the output of the drive circuit 320.

  Further, an interface (not shown) with the inkjet head 300 has a port (not shown) for communicating image data, and the image data (of the analog switch 350) is synchronized with the timing at which the drive circuit 320 generates a drive signal. Control signal for controlling on / off), and each analog switch 350 is turned on / off according to the image data. With such a configuration, an ink ejection pattern is generated by controlling driving or non-driving of each piezo actuator 302 according to image data.

  In other words, a common drive signal is applied to the plurality of piezo actuators 302 from the output unit 366 of the drive circuit 320, and control for controlling on / off of the analog switches 350 connected to the piezo actuators 302 separately from the drive signals. A signal is applied. The ink discharge amount is determined by the waveform of the drive signal, and the ink discharge timing is determined by the control signal.

  Along with the downsizing and higher functionality of the apparatus, the number of nozzles and the size of the head itself have been reduced. For this reason, a narrow pitch multi-pin connector 360 is preferably used for connecting the drive circuit 320 (drive circuit board 322) and the inkjet head 300. Since the narrow-pitch multi-pin connector 360 has a small amount of current that can flow per pin, the drive signal line 362 and the return signal line 364 can be assigned to a plurality of pins so that a large current that can drive the piezo actuator 302 can flow. In many cases, drive signal lines 362 and return signal lines 364 are alternately arranged (adjacent to each other) in order to reduce the impedance of the transmission path.

  By the way, the narrow pitch multi-pin connector 360 may be fixed by being caught while the male / female are stuck diagonally with each other when being inserted / removed. The output portion 366 of the drive circuit is short-circuited to the ground 368 via the drive signal line 362 and the return signal line 364.

  Normally, when the drive circuit 320 is activated, the output circuit 366 of the drive circuit is often set to several volts as an initial operation. However, if the drive circuit 320 is activated while the output circuit 366 of the drive circuit is short-circuited to the ground 368, The output that should be several volts is always 0 V, feedback is applied to the input of the operational amplifier 330, and the output of the operational amplifier 330 rises to the maximum value. At this time, the base potential of the transistor 332 also increases in accordance with the increase in the output of the operational amplifier 330.

On the other hand, since the potential of the emitter of the transistor 332 is short-circuited to 0V (ground) via the output unit 366, the voltage applied between the base and the emitter of the transistor 332 is + V ₁ (5V to 12V) at the maximum. ) Generally, the maximum rating of the base-emitter voltage of the transistor 332 is about several volts, and if the voltage applied between the base-emitter of the transistor 332 exceeds the maximum rating, the transistor 332 is damaged.

  As a countermeasure against such a short circuit between the output portion 366 of the drive circuit 320 and the ground 368, a voltage dividing circuit including resistors 380 and 382 is added to the base input circuit of the transistor 332 as shown in FIG. Thus, a method of protecting a voltage exceeding the maximum rating from being applied between the base and emitter of the transistor 332 is known.

  Further, as a problem relating to driving of the ink jet head, there is a problem that the displacement (variation) of the electrostatic capacity of the piezo actuator 302 affects the ink discharge state. As described above, the drive signal is transmitted to the piezo actuator 302 provided in the inkjet head 300 via the analog switch 350. The drive signal is set assuming a predetermined capacitance of the piezoelectric actuator, and an error in the capacitance is not taken into consideration.

FIG. 17 shows a typical ink discharge waveform (drive signal waveform) used for driving the piezo actuator 302. The ink ejection state (landing state) is determined by the drive signal waveform when the media, such as ink and paper, and the mechanical positional relationship and structure are the same. Determinants of the ejection state in the drive signal waveform include the peak value (V), rising slew rate and falling slew rate (V / t ₁ ), waveform width (timing, t ₂ ), and the like.

  As shown in FIG. 17, the drive signal used for driving the piezoelectric actuator 302 has a peak value of 30 V (20 V to 50 V), and the rising slew rate and the falling slew rate are the same.

  These determining factors are related to the ink ejection speed, the amount of ejected liquid droplets, the ejection timing, etc., and when the variation in the electrostatic capacity of the piezo actuator 302 is larger than the allowable range, the driving is performed assuming a specified electrostatic capacity. When a discharge operation is performed using a signal, there is a problem that a desired stable ink discharge state cannot be obtained.

  As a method for detecting an abnormality in an ink jet head, Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for detecting a short circuit or a rare short circuit of a piezoelectric element. That is, in the technique disclosed in Patent Document 1, a capacitor is provided as means for applying a bias potential such as an intermediate potential of a drive signal for suppressing an abnormal current of a piezoelectric element to the ground side of the piezoelectric element, and the abnormal current is generated by the capacitor. When the battery is further charged, the charging voltage increases, and an abnormality is detected by comparing the increased charging voltage with a reference potential.

In Patent Document 2, a Hall element is provided as a current detection unit for detecting a drive current in the wiring between the drive signal supply unit and the piezoelectric actuator, and the drive current of the capacitive load is detected and detected in one drive cycle. A technique is disclosed in which the drive signal supply is stopped by means for stopping the current of the constant current circuit of the drive circuit unit when the current value is integrated and the overcurrent specified value is exceeded.
Japanese Patent Laid-Open No. 2003-21665 JP 2008-119915 A

  However, when a current detection element or a voltage detection element (resistance, etc.) is connected to the transmission line of the drive signal, the slew rate of the drive waveform is deteriorated due to the resistance value (impedance) of the resistor. As a result, the charging / discharging speed of the piezoelectric actuator is reduced. That is, the drive waveform is distorted by the influence of the impedance of the detection element, affecting the pressure generated by the piezo actuator, and as a result, the ink suction and discharge characteristics of the inkjet head are degraded.

  Furthermore, the method described in Patent Document 1 also has a problem that the discharge efficiency is lowered due to the voltage across the piezoelectric element being reduced.

  On the other hand, as disclosed in Patent Document 2, when a Hall element that is electrically insulated from the drive signal transmission path is used as a means for detecting the drive current, there is a problem in that the ejection performance deteriorates due to waveform distortion of the drive signal. However, since the Hall element is a semiconductor, there is a problem of temperature drift.

  A capacitive load drive circuit such as a piezoelectric element and a drive signal transmission path generate heat because a high-frequency pulse current is transmitted, and the surrounding temperature tends to become high due to its heat dissipation, resulting in an error in the detected value. It is easy to produce. In addition, since the maximum input voltage and the detectable current value of the Hall element are lower than the voltage and current of the drive signal of the piezoelectric element applied to the inkjet head, detection of the drive current of the piezoelectric element applied to the inkjet head Not suitable for.

  The present invention has been made in view of such circumstances, and a current detection sensor substrate, a capacitive load driving device, a liquid discharge head driving device, and a liquid that can detect a driving current without affecting a driving signal. An object is to provide a discharge device.

  In order to achieve the above object, a current detection sensor substrate according to the present invention is electrically connected to an output terminal of a drive circuit that supplies a drive current to a driven element including a capacitive load, and the drive signal is transmitted. A signal line, a detection signal line that is disposed in proximity to the drive signal line via a dielectric, and an induced current is induced by a current of the drive signal transmitted by the drive signal line, and is induced by the detection signal line A detection signal extraction unit that extracts an induced current as a detection signal, the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction unit It is characterized by being formed in the same substrate.

  According to the present invention, an induction current is induced in a detection signal line that is electromagnetically coupled to the drive signal line without providing a detection element that is electrically connected to the drive signal line through which the drive signal is transmitted. Since the induced current is extracted as a detection signal, influences on the drive signal such as waveform rounding, oscillation, and voltage drop can be avoided, and the drive current can be detected over a wide current range.

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

[Overall configuration of inkjet recording apparatus]
FIG. 1 is a schematic diagram showing an overall configuration of an inkjet recording apparatus 10 according to an embodiment of the present invention. As shown in the figure, an inkjet recording apparatus 10 includes a plurality of inkjet heads (hereinafter referred to as heads) provided corresponding to black (K), cyan (C), magenta (M), and yellow (Y) inks. A printing unit 12 having 12K, 12C, 12M, and 12Y, an ink storage / loading unit 14 that stores ink to be supplied to each head 12K, 12C, 12M, and 12Y, and a recording paper 16 that is a recording medium. The paper feeding unit 18 to be supplied, the decurling unit 20 for removing the curl of the recording paper 16, and the nozzle surfaces of the heads 12K, 12C, 12M, and 12Y are arranged so as to maintain the flatness of the recording paper 16. The suction belt conveyance unit 22 that conveys the recording paper 16, the print detection unit 24 that reads the printing result of the printing unit 12, and the paper discharge that discharges the recorded recording paper (printed material) to the outside. It is provided with a 26, a.

  Although not shown in FIG. 1, each head 12K, 12C, 12C, 12M, 12Y included in the printing unit 12 is provided on each upper surface (the surface opposite to the surface facing the recording paper 16). 12M and 12Y drive circuit boards (indicated by reference numeral 101 in FIG. 8) are arranged in a standing state, and are electrically connected to the inkjet head by a flexible flat substrate (indicated by reference numeral 134 in FIG. 8).

  The ink storage / loading unit 14 has an ink supply tank (not shown in FIG. 1 and indicated by reference numeral 60 in FIG. 6) for storing inks of colors corresponding to the heads 12K, 12C, 12M, and 12Y. The ink is communicated with the heads 12K, 12C, 12M, and 12Y through a required ink flow path.

  Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing. Although detailed illustration is omitted, the ink jet recording apparatus 10 of the present example includes an ink supply unit on the upper surface of each head 12K, 12C, 12M, 12Y, and each head from the ink storage / loading unit 14 via the ink supply unit. Ink is supplied to 12K, 12C, 12M, and 12Y.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Thus, it is preferable to automatically determine the type of recording medium (media type) to be used and perform ink ejection control so as to realize appropriate ink ejection according to the media type.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration that uses roll paper, a cutter (first cutter) 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is disposed on the printing surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least nozzle surfaces of the heads 12K, 12C, 12M, and 12Y (ink discharge surfaces on which nozzle openings are formed). ) Is configured to form a horizontal surface (flat surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, an adsorption chamber 34 is provided at a position facing the nozzle surfaces of the heads 12K, 12C, 12M, and 12Y inside the belt 33 spanned between the rollers 31 and 32. The recording paper 16 is sucked and held on the belt 33 by sucking the chamber 34 with the fan 35 to obtain a negative pressure.

  When the power of a motor (not shown in FIG. 1 and indicated by reference numeral 88 in FIG. 7) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 rotates clockwise in FIG. , And the recording paper 16 held on the belt 33 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blowing method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip conveyance mechanism instead of the suction belt conveyance unit 22 is also conceivable, if the roller / nip conveyance is performed in the print area, the roller is brought into contact with the print surface of the sheet immediately after printing, so that the image is easily stained. There is a problem. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The heads 12K, 12C, 12M, and 12Y of the printing unit 12 have a length corresponding to the maximum paper width of the recording paper 16 that is the target of the inkjet recording apparatus 10, and the nozzle surface has at least a recording medium of the maximum size. This is a full-line head in which a plurality of nozzles for ejecting ink are arranged over a length exceeding one side (the entire width of the drawable range) (see FIG. 2).

  The heads 12K, 12C, 12M, and 12Y are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side in the recording paper 16 feed direction. 12K, 12C, 12M, and 12Y are fixedly installed so as to extend in the conveyance direction (paper feeding direction) of the recording paper 16.

  A color image can be formed on the recording paper 16 by discharging different color inks from the heads 12K, 12C, 12M, and 12Y while transporting the recording paper 16 by the suction belt transporting section 22.

  As described above, according to the configuration in which the full-line heads 12K, 12C, 12M, and 12Y having nozzle rows that cover the entire width of the paper are provided for each color, the recording paper 16 and the printing unit 12 are relatively disposed in the paper feeding direction. An image can be recorded on the entire surface of the recording paper 16 by performing the moving operation only once (that is, by one sub-scan). With such a configuration capable of single-pass printing, high-speed printing is possible and productivity can be improved as compared with a shuttle-type head in which the head reciprocates in a direction orthogonal to the paper conveyance direction.

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink color and number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited. Further, after the treatment liquid and the ink are attached to the recording paper 16, the ink color material is aggregated or insolubilized on the recording paper 16 to separate the ink solvent and the ink color material on the recording paper 16. In this ink jet recording apparatus, an ink jet head may be provided as means for attaching the treatment liquid to the recording paper 16.

  Each of the heads 12K, 12C, 12M, and 12Y may have a structure in which a plurality of head modules are connected in the width direction of the recording paper 16, or each head has a structure formed integrally. It may be.

  The print detection unit 24 provided at the subsequent stage of the printing unit 12 includes an image sensor for imaging the droplet ejection result of the printing unit 12, and checks for nozzle clogging and other ejection abnormalities from the droplet ejection image read by the image sensor. Functions as a means to

  The print detection unit 24 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink ejection width (image recording width) by the heads 12K, 12C, 12M, and 12Y. This line sensor includes an R light receiving element array in which photoelectric conversion elements (pixels) provided with a red (R) color filter are arranged in a line, and a G light receiving element array provided with a green (G) color filter. And a color separation line CCD sensor comprising a blue light receiving element array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads the test patterns printed by the heads 12K, 12C, 12M, and 12Y of the respective colors, and detects ejection of the heads 12K, 12C, 12M, and 12Y. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined surface uneven shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  When the recording paper 16 is pressed by the heating / pressurizing unit 44, when printing is performed on the porous paper with dye-based ink, the pores of the paper are blocked by pressurization, which causes damage to the dye molecules such as ozone. By preventing the contact with the image, the weather resistance of the image is improved.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown in FIG. 1, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

[Head structure]
Next, the structure of the head will be described. Since the structures of the color-specific heads 12K, 12C, 12M, and 12Y are common, the heads are represented by the reference numeral 50 in the following.

  FIG. 3A is a plan perspective view showing an example of the structure of the head 50, and FIG. 3B is an enlarged view of a part thereof. 3C is a plan perspective view showing another example of the structure of the head 50, and FIG. 4 is a cross-sectional view showing the three-dimensional configuration of the head 50 (line 4-4 in FIGS. 3A and 3B). FIG.

  In order to increase the dot pitch printed on the recording paper 16, it is necessary to increase the nozzle pitch in the head 50. As shown in FIGS. 3A and 3B, the head 50 of this example includes a plurality of ink chamber units 53 including nozzles 51 that are ink droplet ejection holes and pressure chambers 52 corresponding to the nozzles 51. Are arranged in a matrix (two-dimensionally) in a staggered manner, and are thereby projected substantially in a line along the longitudinal direction of the head 50 (main scanning direction perpendicular to the paper feed direction). High nozzle density (projection nozzle pitch) is achieved.

  The form in which one or more nozzle rows are configured over a length corresponding to the entire width of the recording paper 16 in the main scanning direction substantially orthogonal to the feeding direction of the recording paper 16 is not limited to this example. For example, instead of the configuration of FIG. 3A, as shown in FIG. 3C, short head units 50 ′ in which a plurality of nozzles 51 are two-dimensionally arranged are arranged in a staggered manner and connected. Thus, a line head having a nozzle row having a length corresponding to the entire width of the recording paper 16 may be configured. Although not shown, a line head may be configured by arranging short head units in a line.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. Each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54. The common flow channel 55 communicates with an ink supply tank (not shown in FIGS. 3A to 3C, indicated by reference numeral 60 in FIG. 5) as an ink supply source, and the ink supplied from the ink supply tank is It is distributed and supplied to each pressure chamber 52 via the common flow channel 55 of FIG.

  A piezoelectric element 58 having an individual electrode 57 is joined to a diaphragm 56 that constitutes the top surface of the pressure chamber 52 and also serves as a common electrode. By applying a drive signal to the individual electrode 57, the piezoelectric element 58 is Deformation causes ink to be ejected from the nozzle 51. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  As shown in FIG. 5, the ink chamber unit 53 having such a structure is latticed in a fixed arrangement pattern along a row direction along the main scanning direction and an oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in the shape.

  That is, with a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  When the nozzles are driven by a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzle is divided into blocks, each block is sequentially driven from one side to the other, and the like in the width direction of the recording paper 16 (direction perpendicular to the conveyance direction of the recording paper 16). The driving of the nozzle that prints one line (one line of dots or a line of dots of a plurality of lines) is defined as main scanning.

  In particular, when driving the nozzles 51 arranged in a matrix as shown in FIGS. 3A and 3B, the main scanning as described in the above (3) is preferable. That is, nozzles 51-11, 51-12, 51-13, 51-14, 51-15, 51-16 are made into one block (other nozzles 51-21,..., 51-26 are made into one block, Nozzles 51-31,..., 51-36 as one block,...), And the nozzles 51-11, 51-12,. One line is printed in 16 width directions.

  On the other hand, by moving the full line head and the recording paper 16 relative to each other, printing of one line formed by the main scanning described above (a line composed of one line of dots or a line composed of a plurality of lines) is repeatedly performed. This is defined as sub-scanning.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. In other words, in the present embodiment, the conveyance direction of the recording paper 16 is the sub-scanning direction, and the width direction of the recording paper 16 orthogonal thereto is the main scanning direction. In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

[Configuration of ink supply system]
FIG. 6 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10. The ink supply tank 60 is a base tank that supplies ink to the head 50 and is included in the ink storage / loading unit 14 described with reference to FIG. The ink supply tank 60 includes a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  As shown in FIG. 6, a filter 62 is provided between the ink supply tank 60 and the head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 6, a configuration in which a sub tank is provided in the vicinity of the head 50 or integrally with the head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 is provided with a cap 64 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle. The cap 64 can be moved relative to the head 50 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the head 50 as necessary.

  The cap 64 is displaced up and down relatively with respect to the head 50 by an elevator mechanism (not shown). The cap 64 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the head 50, thereby covering the nozzle surface with the cap 64.

  During printing or standby, if the frequency of use of a specific nozzle 51 is reduced and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, ink cannot be ejected from the nozzle 51 even if the piezoelectric element 58 operates.

  Before such a state is reached (within the range of viscosity that can be discharged by the operation of the piezoelectric element 58), the piezoelectric element 58 is operated, and a cap is formed to discharge the deteriorated ink (ink in the vicinity of the nozzle whose viscosity has increased). Preliminary ejection (purge, idle ejection, collar ejection, dummy ejection) is performed toward 64 (ink receiver).

  Further, when air bubbles are mixed into the ink in the head 50 (in the pressure chamber 52), the ink cannot be ejected from the nozzle even if the piezoelectric element 58 is operated. In such a case, the cap 64 is applied to the head 50, the ink in the pressure chamber 52 (ink mixed with bubbles) is removed by suction with the suction pump 67, and the suctioned and removed ink is sent to the recovery tank 68.

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

[Explanation of control system]
FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, a memory 74, a motor driver 76, a heater driver 78, a print control unit 80, a memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. The image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the memory 74.

  The memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls each part such as the communication interface 70, the memory 74, the motor driver 76, the heater driver 78, etc., performs communication control with the host computer 86, read / write control of the memory 74, etc. A control signal for controlling the system motor 88 and the heater 89 is generated.

  The memory 74 stores programs executed by the CPU of the system controller 72 and various data necessary for control. Note that the memory 74 may be a non-rewritable storage means or a rewritable storage means such as an EEPROM. The memory 74 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 76 is a driver that drives the motor 88 in accordance with instructions from the system controller 72. In FIG. 7, the motor (actuator) arranged in each part in the apparatus is represented by reference numeral 88. For example, the motor 88 shown in FIG. 7 includes a motor for driving the drive roller 31 (32) of the belt 33 in FIG. 1, a motor for a moving mechanism for moving the cap 64 in FIG.

  The heater driver 78 is a driver that drives a heater 89 including a heater as a heat source of the heating fan 40 shown in FIG. 1 and a heater of the post-drying unit 42 according to an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 74 in accordance with the control of the system controller 72. The generated print data This is a control unit that supplies (dot data) to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing of the ink droplets of the head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes a memory 82, and image data, parameters, and other data are temporarily stored in the memory 82 when image data is processed in the print control unit 80, and a waveform data string of drive signals is stored. Has been. Note that an aspect in which the print control unit 80 and the system controller 72 are integrated and configured by one processor is also possible.

  The head driver 84 generates a drive signal to be applied to the piezoelectric element 58 of the head 50 based on the image data given from the print control unit 80, and drives the piezoelectric element 58 by applying the drive signal to the piezoelectric element 58. A drive circuit is included. Note that the head driver 84 shown in FIG. 7 may include a feedback control system for keeping the driving condition of the head 50 constant.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor. The print detection unit 24 reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, whether droplet ejection is performed). Variation), and the detection result is provided to the print controller 80.

  The print control unit 80 controls each unit to perform various corrections to the head 50 and maintenance of the head 50 based on information obtained from the print detection unit 24 as necessary.

  Data of an image to be printed is input from the outside via the communication interface 70 and stored in the memory 74. At this stage, RGB image data is stored in the memory 74.

  The image data stored in the memory 74 is sent to the print controller 80 via the system controller 72, and is converted into dot data for each ink color by the print controller 80. That is, the print control unit 80 performs processing for converting the input RGB image data into dot data of four colors of KCMY. The dot data generated by the print control unit 80 is stored in the memory 82.

  Various control programs are stored in the program storage unit 90, and the control programs are read and executed in accordance with instructions from the system controller 72. The program storage unit 90 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 90 may also be used as a recording means (not shown) for operating parameters.

  The current detection unit 92 illustrated by a broken line in FIG. 7 detects a current flowing through the drive signal line, and is formed on a substrate (a drive circuit substrate, a flexible flat substrate, a head) on which the drive signal line is provided. This is a current sensor using the structure of a wiring pattern.

  Although the detailed configuration and function of the current detection unit 92 will be described later, the current detection unit 92 shown in this example is electrically insulated from the drive signal line, and monitors the current of the drive signal using an electromagnetic field phenomenon. It is.

  The detection signal obtained by the current detection unit 92 is sent to the signal processing unit 94 and subjected to predetermined signal processing such as noise removal and amplification. The detection signal subjected to predetermined signal processing by the signal processing unit 94 is sent to the determination unit 96.

  The determination unit 96 is a functional block that determines the presence / absence of displacement of capacitance of each piezoelectric element, short circuit of the drive signal line, and open based on the current detection signal of the drive signal. Although FIG. 7 illustrates an example in which the system controller 72 has the function of the determination unit 96, the determination unit 96 may be provided independently of the system controller 72.

  The determination result by the determination unit 96 is displayed on the determination result display unit 98. For the determination result display unit 98, an aspect in which the determination result of the character information is displayed on a display device such as an LCD monitor or an LED display, an aspect in which an LED or a lamp representing the determination result is turned on (off), or the like can be applied. . In addition, a mode in which a determination result by the determination unit 96 is written (stored) in a predetermined memory, a mode in which determination result information is output to the outside via a communication interface, and the like are possible.

[Description of drive circuit and current detection]
Next, the configuration of the drive circuit of the piezoelectric element (see FIG. 4) that is the ejection force generating element of the head 50 and the current detection of the drive signal will be described in detail.

  In the inkjet recording apparatus 10 shown in this example, a common drive signal is applied to each piezoelectric element 58, and on / off of the switch element 59 connected to the individual electrode of each piezoelectric element 58 according to the ejection timing of each piezoelectric element 58. By switching the above, a driving method is applied in which ink is ejected from the nozzle corresponding to each piezoelectric element 58.

FIG. 8 is a configuration diagram of the drive circuit 100. As shown in the figure, the drive circuit 100 includes a D / A converter 104 that converts a digital waveform data string 102 output from the waveform data storage unit (memory 82 in FIG. 7) into an analog signal, and an analog signal. The operational amplifier 106 that amplifies the voltage of the converted waveform data (waveform signal) and the electric power supplied from the driving power supply unit + V ₂ to amplify the current of the waveform signal that has been amplified by the operational amplifier 106, and the piezoelectric element A feedback circuit (feedback loop) 114 that includes a drive signal conversion unit 108 that converts the voltage into a voltage suitable for driving 58, resistors 110 and 112, and that feeds back the output voltage of the drive signal conversion unit 108 to the input of the operational amplifier 106; It has.

The drive signal conversion unit 108 includes a push-pull circuit including an NPN transistor 116 and a PNP transistor 118 connected in a totem pole connection. The bases of the transistor 116 and the transistor 118 include resistors 120 and 122 and diodes 124 and 128. A bias circuit (input circuit) 115 is connected. The bias circuit 115 is supplied with power from power sources + V ₁ (5V to 12V) and −V (−5V to −12V).

  The output of the drive circuit 100 (drive signal conversion unit 108) is output from drive signal lines 130 formed on the drive circuit board 101, pins (terminals) of the narrow pitch multi-pin connector 132, and drive signal lines formed on the flexible flat board 134. 136, the drive signal line 138 formed in the head 50, and the switch element 59 are electrically connected to the piezoelectric element 58 (individual electrode). The common electrode (see FIG. 4) of the piezoelectric element 58 includes a return signal line 140 formed on the head 50, a return signal line 142 formed on the flexible flat substrate 134, and a return signal formed on the drive circuit board 101. Electrical connection to the ground 146 of the drive circuit 100 is made via a line 144.

  Further, a current flowing through the drive signal line 130 (136, 138) is detected on the drive circuit board 101, and the state of the piezoelectric element 58 mounted on the head 50 and the drive signal lines 130, 136 to which the drive signal is transmitted. , 138, that is, a functional block for generating a signal representing an abnormality on the drive signal lines 130, 136, 138 is provided.

  The “state of the piezoelectric element 58” includes at least the displacement of the capacitance of the piezoelectric element 58. The “state of the drive signal lines 130, 136, 138” includes at least a short circuit between the drive signal lines 130, 136, 138 and the return signal lines 140, 142, 144 (ground 146).

  FIG. 8 shows an equivalent circuit model of the piezoelectric element 58 in which a resistor representing an insulation resistance is connected in parallel to a capacitor 58B representing a capacitance.

  That is, the drive current detection unit shown in this example includes a current detection unit 92 that extracts an induced current induced by the drive current flowing through the drive signal line 130 as a current detection signal. The current detection unit 92 includes a plurality of detection signal lines 147 provided in proximity to the drive signal line 130 via a dielectric.

  FIG. 8 shows an aspect in which three detection signal lines 147 are arranged around the drive signal line 130. The ends of the detection signal lines 147 are short-circuited together, and a current detection signal is extracted from one end.

  That is, the detection signal line 147 is electromagnetically coupled (capacitive coupling and inductive coupling) with the drive signal line 130, and an induced current is induced when the current flowing through the drive signal line 130 changes. The number of detection signal lines 147 may be one, and an embodiment in which the detection signal lines 147 are provided on both sides of the drive signal line 130 is preferable. From the viewpoint of increasing the detection sensitivity, it is preferable that the distance between the drive signal line 130 and the detection signal line 147 is smaller as long as the insulation performance between the drive signal line 130 and the detection signal line 147 can be secured.

  In addition, the drive current detector includes a voltage converter 150 that converts the voltage of the current detection signal obtained by the current detector 92, an amplifier 152 that amplifies the voltage-converted current detection signal, and a predetermined signal processor. On the basis of the current detection signal subjected to the signal processing, the displacement of the electrostatic capacitance of the piezoelectric element provided in the head 50 is determined, and whether or not the drive signal lines 130, 136, 138 are short-circuited or opened. And a holding unit 154 that holds the determination result of the determination unit 96 for a predetermined period.

  The signal processing unit 94 illustrated in FIG. 7 includes the voltage conversion unit 150 and the amplification unit 152 illustrated in FIG. Since the current detection signal is affected by high frequency noise, it is preferable to take measures such as acquiring a signal within a certain period or adding a filter circuit for removing high frequency noise.

  A determination signal serving as a determination threshold value is input to the determination unit 96. The determination signal includes a short-circuit determination voltage 155 that determines whether the drive signal lines 130, 136, and 138 are short-circuited, an open-circuit determination voltage 156 that determines whether the drive signal lines 130, 136, and 138 are open, and a displacement of the capacitance of the piezoelectric element 58. A capacity regulation value determination voltage 157, a capacity displacement class 1 determination voltage 158, and a capacity displacement class 2 determination voltage 159 used for determining the amount are included, and the determination results based on the respective determination voltages are sent to the holding unit 154 separately.

  The specified capacity value determination voltage 157 is a lower limit value allowed by the capacitance displacement specified by the specification (standard) of the piezoelectric element 58. If this upper limit value is exceeded, the displacement of the capacitance of the piezoelectric element 58 is within the variation range unique to the element and is acceptable. On the other hand, if it is below this lower limit, it is determined that the abnormal level is the first stage.

  The capacitance displacement class 1 determination voltage 158 is a capacitance displacement outside the normal range defined in the specification, and refers to a first-stage correction limit value. When the charging current to the piezoelectric element 58 decreases due to the decrease in the capacitance, and as a result, the voltage input to the determination unit 96 becomes equal to or lower than the specified capacitance value determination voltage 157, driving assuming a specified capacitance is performed. Even if a signal waveform is applied, a desired image formation is affected by a decrease in discharge performance such as a decrease in discharge amount. In view of this, the displacement (decrease) in the capacitance is compensated by correcting the drive signal waveform (voltage increase), thereby correcting the decrease in ejection performance and forming a desired image. The capacity displacement class 1 determination voltage 158 is a threshold value for determining the middle level of the abnormal level for determining the lower limit of the correction of the first level.

  The capacity displacement class 2 determination voltage 159 refers to a correction limit value that is less than the capacity displacement class 1 determination voltage 158. When the capacitance displacement class 1 determination voltage is less than 158 and the capacitance displacement class 2 determination voltage 159 is greater than or equal to, the drive signal waveform by the second stage correction is output (the degree of correction is greater than the first stage correction described above). Compensate for the decrease in capacitance by correcting the drive signal waveform. On the other hand, when the capacitance displacement class 2 determination voltage is less than 159, the abnormal level is higher than the correction limit value, and the head 50 including the abnormal piezoelectric element 58 is replaced, or the corresponding piezoelectric element 28 is unused. It becomes a criterion for performing such processing.

  The determination result held in the holding unit 154 is notified to upper blocks in the apparatus such as the system controller 72 and the print control unit 80 illustrated in FIG. 7, and processing corresponding to the state is appropriately performed. The determination result of the determination unit 96 is displayed by the determination result display unit 98 illustrated in FIG. Further, the information held in the holding unit 154 is reset by a reset signal (reset). The reset signal is input when the device is reset or at the timing of the drive signal.

  As an example of the process notified of the determination result, when a piezoelectric element 58 having a capacitance outside a predetermined appropriate range is found, the ID (identification number) of the nozzle corresponding to the piezoelectric element 58 is stored. In addition, the image data is changed so that the nozzle is not used. Further, when it is determined that the drive signal lines 130, 136, and 138 are short-circuited or opened, an error message to that effect is displayed on the determination result display unit 98, and the operation of the drive circuit is stopped. .

  Further, the drive circuit board 101 shown in this example is provided with a test drive circuit 160 for inspecting abnormality on the drive signal lines 130, 136, and 138. The test drive circuit 160 generates a test drive signal having a slew rate higher than the drive signal generated by the drive circuit 100.

Since the configuration of the test drive circuit 160 is the same as that of the drive circuit 100, a detailed description thereof is omitted. However, the operational amplifier 162 that amplifies the waveform data converted into the analog signal and the power supply + V ₁ and −V supply power. When the bias signals generated by the resistors 164 and 166 and the diodes 168 and 170 constituting the bias circuit 163 that generates the bias signal and the bias circuit 163 are input, the drive power supply unit + V ₂ Transistors 174 and 176 constituting a drive signal conversion unit 172 that receives a supply of energy and amplifies the current of the waveform data voltage amplified by the operational amplifier 106 and converts it to a voltage suitable for driving the piezoelectric element 58; Feedback that feeds back the output voltage of the drive signal converter 172 to the input of the operational amplifier 162 It includes a resistor 177 and 178 that constitute the road, the.

  A switch 180 is provided at the output portion of the D / A converter 104, and a switch 182 is provided at the output portion of the drive circuit 100, the output portion of the test drive circuit 160, and the connection portion of the drive signal line 130. By switching the switches 180 and 182, it is possible to switch between a normal operation mode using the drive circuit 100 and a test mode using the test drive circuit 160.

  That is, when the apparatus is started up, at the time of startup after an emergency stop (temporary pause), or during non-image recording, such as during maintenance, the test drive circuit 160 is switched to perform inspection, and during normal image recording, the drive circuit 100 is switched. The inspection is executed in parallel with the image recording.

  FIG. 9A illustrates a waveform example of a drive signal of the piezoelectric element 58 applied to the inkjet head. The drive signal waveform 200 shown in FIG. 9A has a voltage value of 50V and a slew rate of 50V / μsec. A general drive signal has a voltage value of about several tens of volts and a slew rate of about several tens of volts / μsec.

  In addition, the full line type ink jet head applied to this example has several hundred to several thousand nozzles (number of piezoelectric elements), and the capacitance per one piezoelectric element is about several hundred pF. .

  FIG. 9B shows the current waveform of the drive signal. As shown in the figure, a charging current for charging the capacitive component of the piezoelectric element flows at the rising edge of the driving signal, and a discharging current for discharging the capacitive component of the piezoelectric element flows at the falling edge of the driving signal. That is, a high-frequency pulse current flows through the drive signal line (reference numerals 130, 136, and 138 in FIG. 8).

  The current value i of the drive signal flowing through the drive signal line is calculated by the following equation (1).

i = C × (dv / dt) (1)
If the slew rate (dV / dt) of the drive circuit is increased in order to detect the displacement of the capacitance C with the current i, the displacement amount of C can be easily identified.

  An example of calculating the drive current value i using the above equation (1) is shown below. The calculation conditions are as follows.

(Calculation conditions)
Capacitance of one piezoelectric element: 500 pF
Insulation resistance of piezoelectric element: 1 GΩ (when insulation is defective: 10 kΩ to 100 kΩ)
Drive signal slew rate: 50 V / μsec
Drive voltage: 50V (maximum value)
Number of nozzles of inkjet head (number of piezoelectric element elements): 256 When the driving current i when driving one nozzle (one piezoelectric element) is the maximum driving voltage (50 V),
i = (500 × 10 ⁻¹² ) × (50 × 10 ⁶ ) = 2.5 × 10 ⁻² [A]
It is.

The drive current i when the insulation resistance value is 1 GΩ (normal) is
i = V / R = 50 / (1 × 10 ⁹ ) = 5 × 10 ⁻⁸ [A]
It becomes.

On the other hand, when the insulation resistance value is 100 kΩ (when insulation is defective), the drive current i is
i = V / R = ^{50/10 5} = 5 × 10 ⁻⁴ [A]
When the insulation resistance is 10 kΩ (when insulation is defective), the drive current i is
i = V / R = 50/10 ⁴ = 5 × 10 ⁻³ [A]
It is.

The drive current i when driving 256 nozzles (piezoelectric elements 256 elements) is:
i = (500 × 10 ⁻¹² × 256) × (50 × 10 ⁶ ) = 6.4 [A]
When the insulation resistance value is 1 GΩ, the drive current i is
i = V / R = 50 / (10 ⁹ /256)=1.28×10 ⁻⁵ [A]
It is. The drive current i when the insulation resistance value is 100 kΩ (when insulation is defective) is
i = V / R = 50 / (10 ⁵ /256)=1.28×10 ⁻¹ [A]
When the insulation resistance value is 10 kΩ (when insulation is defective), the drive current i is
i = V / R = 50 / (10 ⁴ /256)=1.28 [A]
It is.

  As described above, as an abnormal case when the ink jet head is viewed from the drive circuit, (1) short circuit, (2) open or connector disconnection, and (3) capacitance displacement can be considered. FIG. 10 shows the current waveform of the drive signal corresponding to each abnormality.

  A curve denoted by reference numeral 220 in FIG. 10 is a current waveform of a drive signal during charging during a short circuit. A curve indicated by a broken line denoted by reference numeral 222 is a current waveform of a drive signal in a normal state when a plurality of (256 in this example) piezoelectric elements are charged, and a curve denoted by reference numeral 224 is 1 A current waveform of a drive signal in a normal state when one piezoelectric element is charged, and a curve denoted by reference numeral 226 is a drive when the capacitance is displaced (when the capacitance is lowered) when one piezoelectric element is charged. It is a current waveform of a signal.

  It is possible to detect the abnormalities (1) to (3) by setting an appropriate threshold value by paying attention to the difference between the current values of the drive current waveforms and comparing the detected current value with the threshold value. it can.

FIG. 10 shows threshold currents Ip _{0 to} Ip ₄ as threshold setting examples. The threshold currents Ip _{0 to} Ip ₄ shown in the figure are converted into voltage values, and the short circuit determination voltage 155, the open determination voltage 156, the specified capacity value determination voltage 157, the capacity displacement class 1 determination voltage 158, and the capacity displacement shown in FIG. A class 2 determination voltage 159 is sent to the determination unit 96.

Since a large current flows when the transmission circuit (drive signal lines 130, 136, and 138 in FIG. 8) from the drive circuit to the piezoelectric element is short-circuited and when the piezoelectric element itself is short-circuited, the detection voltage is much higher than when other abnormalities occur. Shows a high level. Ip _{0 in} FIG. 10 is a current value corresponding to the short circuit determination voltage 155 in FIG.

  In addition, since many piezoelectric elements are connected, the normal electric current for charging these many piezoelectric elements also becomes large. In other words, the discrimination between the charging current and the short-circuit current is where a considerably high current value flows. Therefore, it is desirable that short-circuit detection is performed at an early stage in a low current value by driving several adjacent piezoelectric elements as one detection block and driving in units of blocks or in units of one piezoelectric element. Since a large current flows suddenly during a short circuit, a current level that is clearly different from the normal state is detected. Therefore, abnormalities are detected early before reaching a dangerous current value that causes the drive circuit or piezoelectric element to fail. It is possible.

When the transmission line from the drive circuit to the piezoelectric element is open, for example, when the connector on the transmission line is disconnected or disconnected, the current does not flow, so the threshold value can be set to a much lower level than in other abnormal cases. Ip _{4 in} FIG. 10 is a current value corresponding to the open determination voltage 156 in FIG.

  When the piezoelectric actuator is in an electrostatic capacity state (capacity displacement), an abnormal signal is output in comparison with a certain displacement level from a detection voltage corresponding to a normal charge / discharge current value.

  When the head 50 is divided into several blocks and inspection is performed for each block, for example, if the nozzle 51 (piezoelectric element 58) is one block in a group of several to several tens, one block The total per-capacitance is (capacitance per element × number of elements in the block). In this way, the current value detected by performing the inspection in units of blocks increases, and the detection voltage also increases. That is, since the difference in detection voltage between the normal state and the abnormal state of the piezoelectric element also increases, there is an advantage that the normal state and the abnormal state can be clearly distinguished.

  In addition, since the inspection is performed for each block, the inspection time is shortened compared with the inspection for each element. In a block that is determined to be abnormal, the piezoelectric elements that are abnormal are identified by inspecting the piezoelectric elements included in the block one by one.

  The block and the piezoelectric element can be selected by switching control of the switch 59 shown in FIG. 8 according to an instruction from a host device (for example, the system controller 72 and the print control unit 80 in FIG. 7).

_{Ip1 in} FIG. 10 corresponds to a specified value determination voltage 157 (see FIG. 8) when detection is performed in units of blocks. When detection is performed in units of blocks, the charging current for charging the combined capacitance of the piezoelectric elements included in the block is a reference. Further, I _p2 corresponds to the specified value determination voltage 157 when the inspection is performed for each element.

I _p3 corresponds to the capacitance displacement class 1 determination voltage 158 or the capacitance displacement class 2 determination voltage 159. The determination based on the capacitance displacement class 1 determination voltage 158 and the capacitance displacement class 2 determination voltage 159 is performed for each element.

[Specific example of current detector]
Next, a specific structural example of the current detection unit 92 shown in FIGS. 7 and 8 will be described. As described above, the current detection unit 92 applied to this example is configured by the wiring pattern structure of the drive circuit board 101, and is not electrically connected to the drive signal lines 130, 136, and 138, and the electromagnetic field phenomenon. Is used to detect the current flowing in the drive signal lines 130, 136, and 138.

  FIG. 11 is a cross-sectional view illustrating a structure example of the current detection unit 92 when a four-layer substrate is applied to the drive circuit substrate 101. In FIG. 11, parts that are the same as or similar to those in FIG. 8 are given the same reference numerals, and descriptions thereof are omitted.

  As shown in the figure, the current detection unit 92 in FIG. 8 is formed by a pattern structure of drive signal lines 130 (shown by broken lines) from the output unit of the drive circuit 100 to the terminals of the connector 132 of the inkjet head. Specifically, a signal pattern line (detection signal line) 147 for current detection is arranged so as to surround the pattern line of the drive signal line 130. The pattern of the drive signal line 130 passes through the inner layer 242 of the drive circuit board 101. The pattern of the detection signal line 147 is arranged on the upper layer (surface layer) 244 and the lower layer 246 of the pattern of the drive signal line 130 arranged on the inner layer 242.

  Between the pattern of the detection signal line 147 and the pattern of the drive signal line 130, dielectric layers (insulating layers between the wiring layers of the drive circuit board 101) 248, 250 are sandwiched, and the drive signal line 130 and the detection signal line Reference numeral 147 denotes an insulating relationship. This structure obtains electromagnetic coupling between the mutual patterns of the drive signal line 130 and the detection signal line 147, and induces an induced current in the pattern of the detection signal line 147 by the current of the drive signal flowing through the pattern of the drive signal line 130. To do. The capacitor symbol marks illustrated in the dielectric layers 248 and 250 in FIG. 11 indicate that the drive signal line 130 and the detection signal line 147 are capacitively coupled.

  In particular, in the via connection when the pattern of the drive signal line 130 is connected from the inner layer 242 to the output terminal of the drive circuit on the surface layer 244 (terminal of the connector 132), the current detection via 147A surrounds the via 130A. Be placed. That is, between different wiring layers so as to surround the periphery of a via (vertical wiring) 130A that penetrates a dielectric layer (insulating layer) between different wiring layers and is electrically connected to the drive signal line 130 provided between the different wiring layers. A via 147A that penetrates the dielectric layer (insulating layer) and is electrically connected to the detection signal line 147 provided between the different wiring layers is provided.

  The above-described form “the current detection via 147 </ b> A is disposed so as to surround the via 130 </ b> A” includes a form “the drive signal line passes through the detection signal line having a closed curve”.

  The distance between the drive signal line 130 and the detection signal line 147 when using a general printed circuit board is 1.6 mm and the inner layer conductor 35 μm is {1600− (35 + 35 + 35)} / 2 (dielectric 2 layers) = 747.5 (μm). That is, the distance between the drive signal line 130 and the detection signal line 147 is about several tens μm to several hundreds μm (1 mm or less).

The area of the detection signal line 147 is determined by the dielectric constant of the dielectric between the drive signal line 130 and the detection signal line 147 (C in equation (2) described later) and the induced electromotive force (V in equation (3) described later). _N ). In Expression (2), when ε ₀ : 8.854 × 10 ⁻¹² and ε _r = 4.7, ^□ 1.1 mm.

  FIG. 12 illustrates an arrangement example of the vias 130A and 147A viewed from the surface layer 244 of the drive circuit board 101. In the arrangement example shown in FIG. 12, the vias 147A of the nine detection signal lines 147 are arranged so as to surround the nine vias 130A that are electrically connected to the drive signal line 130. The vias 130A and the vias 147A are arranged substantially in parallel so as not to cross each other, and the nine vias 147A are arranged at equal intervals in the peripheral direction of the vias 130A.

  In order to surround the periphery of the via 130A electrically connected to the drive signal line 130, the number of the vias 147A of the detection signal line 147 may be three or more. However, in order to improve the current detection sensitivity, the detection signal The vias 147A of the line 147 are preferably arranged as densely as possible.

  The via 147A of the detection signal line 147 has a higher inductance component than the pattern of the detection signal line 147, so that the impedance is increased and the detection sensitivity is relatively high. Therefore, the decrease in S / N is suppressed. Can do.

  The stray capacitance between the wiring layers of the drive circuit board 101 can be expressed by the following equation (2).

C = ε ₀ × ε _r × S / d (2)
In the above equation (2), ε is the dielectric constant of the insulating material (substrate base material) between the wiring layers, S is the area of the wiring pattern (the total area when a plurality of patterns are used), and d is the distance between the wiring layers. .

  According to the equation (1), the stray capacitance C is preferably increased in order to improve the detection sensitivity. According to the equation (2), the stray capacitance C between the wiring layers is inversely proportional to the distance d between the wiring layers (the distance between the drive signal line and the detection signal line), so that the stray capacitance can be reduced by reducing the distance d between the wiring layers. C can be made larger.

  In the case of a four-layer board having a total thickness of about 1 mm, the distance d between the wiring layers is about 100 μm, and the value of d is determined from the viewpoint of ensuring a predetermined insulation performance. There is a limit on the structure of the substrate to reduce the value. When a multilayer substrate structure is used, the stray capacitance C is preferably increased by using a material having a high dielectric constant as the material of the insulating layer between the wiring layers.

  The detection structure described above is modeled on a transmission line crosstalk equivalent circuit that is generally known. The crosstalk model (adjacent noise coupling model) involves both capacitive and inductive electrical coupling.

Figure 13 (a), (b) shows the capacitive coupling between conductors due to the stray capacitance C ₁₂ between the conductor 1 and the conductor 2. FIG. 13A is a physical representation, and FIG. 13B is an equivalent circuit. The coupling voltage V _N of the load resistance R (R << 1 / [j × ω × (C ₁₂ + C _2G )]) can be approximated by the following equation (3).

V _N = j × ω × R × C ₁₂ × V ₁ (3)
Figure 13 C ₁₂ in is the stray capacitance between conductors of the conductor 1 and the conductor 2, if voltage is time-varying signals flowing in the conductor 1 at both ends of the C ₁₂ is a potential difference occurs time-varying, the Displacement current flows through the conductor 2 using the potential difference as an electromotive force. That is, the change of the voltage V1 of the conductor 1 is a displacement current flows in the conductor 2 due to the presence of the conductor capacitance C _12, the induced voltage V _N is induced by the load resistor R.

That is, the conductor 1 in FIGS. 13A and 13B corresponds to the drive signal lines 130, 136 and 138, and the conductor 2 corresponds to the detection signal line 147. Induction current is induced in the conductor 2 (detection signal line 147) by the induced voltage V _N generated across the load resistor R.

FIGS. 14A and 14B show inductive coupling of conductors. FIG. 14A is a physical representation, and FIG. 14B is an equivalent circuit. The coupling voltage V _N can be approximated by the following equation (4).

V _N = j × ω × M × I = M × (dI / dt) (4)
Here, electromagnetic induction will be briefly described with reference to FIG. If Figure 14 the magnetic flux generated by the current I flowing through the circuit 270 shown in (c) [Phi is, that interlinks the closed circuit of the circuit 272, the proportionality constant linking the magnetic flux [Phi ₁₂ of the current I and the circuit 272 flowing through the circuit 270 each other Inductance M. The magnetic flux Φ ₁₂ is expressed by the following equation (5) using the mutual inductance M and the current I.

Φ ₁₂ = M × I (5)
Current I temporally flux [Phi and [Phi ₁₂ is changed when changing electromotive voltage V _N in a direction of canceling the temporal change in [Phi ₁₂ occurs. In the equivalent circuit model shown in FIG. 14 (b), the induced current is induced by the electromotive voltage V _N and R _2.

  That is, the circuit 270 in FIG. 14C corresponds to the via 130A in FIG. 12, and the circuit 272 in FIG. 14C corresponds to the via 147A in FIG.

  According to the current detection of the drive signal for driving the ink jet head configured as described above, the current of the drive signal transmitted by the drive signal line is generated in the detection signal line electrically insulated from the drive signal. Therefore, the drive signal waveform rounding, voltage drop, slew rate decrease, etc. do not occur, and it is possible to prevent the discharge performance of the inkjet head from being deteriorated due to the current detection of the drive signal.

  In addition, by using the wiring pattern of the substrate for the bulb detection unit, there is no limitation on the current range and voltage range as in the Hall element, and it is driven at several tens of volts and several amperes like the piezoelectric element provided in the inkjet head. It is possible to detect the signal. Furthermore, the detection characteristics can be freely designed by devising the interval and area of the wiring pattern.

  In the present embodiment, an example in which the current detection unit 92 that functions as a current detection sensor is formed on the drive circuit board 101 is illustrated. However, the current detection unit 92 is a substrate on which the drive signal lines 130, 136, and 138 are formed. It can be formed also in a region where the flexible flat substrate 134 and the drive signal line of the head 50 are disposed. Of course, only the current detection unit 92 may be configured in one substrate. Further, the drive signal lines 130, 136, 138 and the detection signal line 147 may be formed in the same plane (in the wiring layer).

  Further, in the present embodiment, the current detection of the drive signal for driving the piezoelectric element used as the ejection force generating element of the ink jet head is exemplified, but the driven element including a capacitive load such as a piezoelectric element used for other applications The present invention can also be applied to current detection of the drive signal.

  In the present embodiment, an inkjet recording apparatus that forms a color image on a recording medium is shown as an example of an apparatus to which the present invention is applied. However, the present invention is a liquid ejecting apparatus (dispenser or the like) that ejects liquid from the ejection head onto the medium. Etc.) and can be widely applied to configurations in which a piezoelectric actuator is applied to an ejection force generating element.

  The present invention is not limited to the above examples, and it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

<Appendix>
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including at least the invention described below.

  (Invention 1): a drive signal line that is electrically connected to an output terminal of a drive circuit that supplies a drive current to a driven element including a capacitive load and transmits the drive signal; and a dielectric is connected to the drive signal line And a detection signal line that induces an induced current by a current of a drive signal transmitted by the drive signal line, and a detection signal extraction unit that extracts the induced current induced in the detection signal line as a detection signal; The drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate. Current detection sensor board to be used.

  According to the present invention, an induction current is induced in a detection signal line that is electromagnetically coupled to the drive signal line without providing a detection element that is electrically connected to the drive signal line through which the drive signal is transmitted. Since the induced current is extracted as a detection signal, influences on the drive signal such as waveform rounding, oscillation, and voltage drop can be avoided, and the drive current can be detected over a wide current range.

  In other words, the drive signal line and the detection signal line are disposed in the vicinity of several tens to several hundreds of micrometers with a dielectric interposed therebetween, and are electromagnetically coupled, and this structure is used as a current detection sensor. According to such a structure, a current sensor that is electrically insulated from the drive signal line is used to excite an induced current in the detection signal line in response to a change in the current flowing through the drive signal line, and the induced current is detected. By taking it out as a signal, a detection signal corresponding to the current flowing through the drive signal line can be obtained.

  The current detection sensor having such a structure is preferable because it has a simple structure using the wiring structure of the substrate, has a very low possibility of failure, and does not change with time.

  The drive signal generator includes a low voltage circuit (circuit that handles small signals) that converts waveform data into a predetermined analog signal, and current and voltage required to drive the piezoelectric actuator using the waveform data converted into the analog signal as an input signal. And a power circuit (a circuit that handles a high voltage and a large current) that converts the drive signal into a drive signal having the above.

  There is a mode in which the electrical wiring includes a drive signal line through which a drive signal is transmitted and a return signal line through which a return signal (ground potential signal) is transmitted.

  A driven element having a capacitive load includes a piezoelectric actuator. The piezoelectric actuator includes a piezoelectric element having a structure in which a piezoelectric material is sandwiched between metal films serving as electrodes. Moreover, the member which operate | moves according to a deformation | transformation of a piezoelectric element may be included.

  (Invention 2): The current detection sensor substrate according to Invention 1, wherein an insulating layer including at least three wiring layers and including a dielectric is provided between the wiring layers, and the driving signal line is provided. Has a structure sandwiched between wiring layers provided with the detection signal lines via the insulating layer, and the detection signal lines obtain characteristics of electromagnetic coupling with the drive signal lines.

  According to this aspect, by using the multilayer wiring structure of the substrate, the freedom of wiring of the drive signal line and the detection signal line is increased, and the structure is simplified.

  In order to increase the detection sensitivity, a mode in which a material having a high dielectric constant is applied to the insulating layer is preferable.

  (Invention 3): In the current detection sensor substrate according to Invention 2, the detection signal line has a predetermined area.

  In this aspect, the area of the detection signal line can be obtained from the electrostatic capacitance between the drive signal line and the detection signal line and the induced electromotive force induced in the detection signal line.

  (Invention 4): In the current detection sensor substrate according to Invention 2 or 3, the drive signal line passes through an insulating layer between different wiring layers and electrically connects drive signal lines provided in different wiring layers. The detection signal line includes an interlayer wiring, and the detection signal line includes a detection signal interlayer wiring arranged so as to surround the drive signal interlayer wiring through an insulating layer between different wiring layers.

  According to this aspect, the interlayer wiring can lower the impedance than the wiring pattern on the surface formed in the wiring layer, which contributes to improvement in detection sensitivity.

  (Invention 5): A drive signal line that is electrically connected to an output terminal of a drive circuit that supplies a drive current to the capacitive load and transmits the drive signal, and surrounds the periphery of the drive signal line via an insulator. A detection signal line in which an induced current is induced by a current of a drive signal transmitted by the drive signal line, and a detection signal extraction unit that extracts the induced current induced in the detection signal line as a detection signal; The drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction part are formed in the same substrate. Current detection sensor board.

  According to the present invention, the detection signal line is disposed in proximity to and inductively coupled around the drive signal line via the insulator, and this structure is used as a current detection sensor, which is electrically insulated from the drive signal line. By using the current sensor, an induced current is excited in the detection signal line according to a change in the current flowing in the drive signal line, and the induced current is taken out as a detection signal, thereby detecting a detection signal corresponding to the current flowing in the drive signal line. Obtainable.

  (Invention 6): In the current detection sensor substrate according to Invention 5, the drive signal line includes at least two wiring layers, and the driving signal line is provided in a different wiring layer through an insulating layer between different wiring layers. Drive signal interlayer wiring for electrically connecting the lines, and the detection signal line includes a detection signal interlayer wiring disposed so as to surround the drive signal interlayer wiring through an insulating layer between different wiring layers, and an electromagnetic field It is characterized by obtaining the characteristics of bonding.

  The drive signal interlayer wiring and the detection signal interlayer wiring in this aspect include vias that electrically connect the wiring layers having a laminated structure.

  (Invention 7): a drive signal generation unit that generates a drive signal, an output terminal that supplies a drive signal generated by the drive signal generation unit to a driven element having a capacitive load, the driven element, and the output Inductive current is induced by the current of the drive signal line electrically connected to the end and disposed close to the drive signal line via a dielectric, and the drive signal line transmitted through the drive signal line. A detection signal line, and a detection signal extraction unit that extracts an induced current induced in the detection signal line as a detection signal, and the drive signal line and the detection signal line are formed as a wiring pattern, and The capacitive load driving device, wherein the drive signal line, the detection signal line, and the detection signal extraction unit are formed in the same substrate.

  According to the present invention, an induction current is induced in a detection signal line that is electromagnetically coupled to the drive signal line without providing a detection element that is electrically connected to the drive signal line through which the drive signal is transmitted. Since the induced current is extracted as a detection signal, influences on the drive signal such as waveform rounding, oscillation, and voltage drop can be avoided, and the drive current can be detected over a wide current range.

  (Invention 8): In the capacitive load driving device described in Invention 7, the substrate includes the current detection sensor substrate described in any one of Inventions 2 to 4.

  (Invention 9): a drive signal generation unit that generates a drive signal, an output terminal that supplies a drive signal generated by the drive signal generation unit to a driven element having a capacitive load, the driven element, and the output A drive signal line that is electrically connected to the end and that transmits the drive signal, and is disposed so as to surround the periphery of the drive signal line via an insulator, and is driven by a current of the drive signal that is transmitted by the drive signal line A detection signal line that induces an induced current; and a detection signal extraction unit that extracts the induced current induced in the detection signal line as a detection signal. The drive signal line and the detection signal line are formed as a wiring pattern. And the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate.

  According to the present invention, the detection signal line is arranged close to the periphery of the drive signal line via the insulator and electromagnetically coupled, and this structure is used as a current detection sensor and is electrically insulated from the drive signal line. Detection signal corresponding to the current flowing in the drive signal line by exciting the induced current in the detection signal line in accordance with the change in the current flowing in the drive signal line and taking out the induced current as a detection signal. Can be obtained.

  (Invention 10): In the capacitive load driving device described in Invention 9, the substrate includes the current detection sensor substrate described in Invention 6.

  (Invention 11): a liquid discharge head including a piezoelectric actuator that applies discharge pressure to liquid discharged from a nozzle, a drive signal generation unit that generates a drive signal supplied to the piezoelectric actuator, and a drive signal generation unit A drive signal line that is electrically connected to the output end and transmits the drive signal, and is disposed in proximity to the drive signal line via a dielectric, and an induced current is generated by the current of the drive signal transmitted through the drive signal line. A detection signal line that is induced, and a detection signal extraction unit that extracts an induced current induced in the detection signal line as a detection signal, and the drive signal line and the detection signal line are formed as a wiring pattern, The liquid ejection head drive device, wherein the drive signal line, the detection signal line, and the detection signal extraction unit are formed in the same substrate.

  According to the present invention, an induction current is induced in a detection signal line that is electromagnetically coupled to the drive signal line without providing a detection element that is electrically connected to the drive signal line through which the drive signal is transmitted. Since the induced current is extracted as a detection signal, influences on the drive signal such as waveform rounding, oscillation, and voltage drop can be avoided, and the drive current can be detected over a wide current range.

  The liquid discharge head includes an ink jet type discharge head that discharges a liquid from a nozzle by using a discharge pressure applied from a discharge force generating element having a capacitive load such as a piezoelectric actuator.

  (Invention 12): In the liquid ejection head driving device according to Invention 11, the substrate includes the current detection sensor substrate according to any one of Inventions 2 to 4.

  (Invention 13): a drive signal generation unit that generates a drive signal supplied to a piezoelectric actuator provided in a liquid discharge head that discharges liquid from a nozzle, and an output terminal of the drive signal generation unit, and the drive signal And a detection signal line that is disposed so as to surround the drive signal line via an insulator, and an induced current is induced by the current of the drive signal transmitted by the drive signal line And a detection signal extraction unit that extracts an induced current induced in the detection signal line as a detection signal, and the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line and the detection signal line A liquid ejection head driving device, wherein the detection signal line and the detection signal extraction portion are formed in the same substrate.

  According to the present invention, the detection signal line is arranged close to the periphery of the drive signal line via the insulator and electromagnetically coupled, and this structure is used as a current detection sensor and is electrically insulated from the drive signal line. Detection signal corresponding to the current flowing in the drive signal line by exciting the induced current in the detection signal line in accordance with the change in the current flowing in the drive signal line and taking out the induced current as a detection signal. Can be obtained.

  (Invention 14): In the liquid ejection head driving device according to Invention 13, the substrate includes the current detection sensor substrate according to Invention 6.

  (Invention 15): In the liquid ejection head drive device according to any one of Inventions 11 to 14, at least one of the piezoelectric actuator and the drive signal line based on a current of the drive signal detected by the detection signal line. An abnormality determination unit for determining the presence or absence of any abnormality is provided.

  According to this aspect, it is possible to detect the cause of the deterioration of the discharge performance of the liquid discharge head by detecting the abnormality of the piezoelectric actuator and the drive signal line using the current value of the drive signal.

  (Invention 16): In the liquid ejection head drive device according to Invention 15, the abnormality determination unit includes a capacitance determination unit that determines a displacement amount of a capacitance with respect to a reference capacitance in the piezoelectric actuator, and the It includes at least one of a short-circuit determination unit that determines whether or not a drive signal line is short-circuited and an open-circuit determination unit that determines whether or not the drive signal line is open.

  According to this aspect, the cause of the decrease in the discharge performance of the liquid discharge head is discovered by determining the displacement of the capacitance of the piezoelectric actuator, the presence or absence of a short circuit of the drive signal line, and the presence or absence of the release of the drive signal line. It becomes possible.

  A short circuit of a drive signal line means a state in which the resistance value between the drive signal line and the return signal line (reference potential) to which the return signal is transmitted is approximately 0Ω, or a certain resistance value (several Ω to All of the states that are connected with a resistance value of about several hundred ohms are included.

  (Invention 17): In the liquid ejection head drive device according to any one of Inventions 11 to 16, the abnormality determination unit includes an abnormal state storage unit that stores an abnormal state for a predetermined period, the piezoelectric actuator, and the drive And an informing means for informing an abnormal state when at least one of the signal lines is abnormal.

  According to such an aspect, when it is determined that there is an abnormality, the abnormal state is notified, so that the cause of the abnormality can be removed and it is possible to prevent a decrease in the discharge performance of the liquid discharge head.

  (Invention 18): The liquid ejection head drive device according to any one of Inventions 11 to 17, wherein the test drive circuit generates a test drive signal having a slew rate higher than the drive signal generated by the drive circuit. It is provided with.

  According to this aspect, it is possible to improve the detection sensitivity of the drive current by using the test drive circuit that generates the test drive signal having a high slew rate.

  In such an aspect, an aspect including switching means for switching between a normal drive circuit and a test drive circuit is preferable.

  (Invention 19): A liquid ejection apparatus comprising: a liquid ejection head that ejects liquid from a nozzle; and the liquid ejection head driving device according to any one of Inventions 11 to 18.

  The liquid ejecting apparatus includes an ink jet recording apparatus that ejects color ink from a nozzle to form a desired image on a recording medium.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a plan view of a main part around a printing unit of the inkjet recording apparatus shown in FIG. Plane perspective view showing structural example of head Sectional view along line 4-4 in FIG. Enlarged view showing the nozzle arrangement of the head shown in FIG. 1 is a schematic diagram showing the configuration of an ink supply system of the ink jet recording apparatus shown in FIG. Schematic diagram showing the configuration of the control system of the ink jet recording apparatus shown in FIG. Block diagram showing the configuration of an inkjet head drive circuit The figure explaining an example of a drive signal The figure explaining the electric current of a drive signal Sectional drawing which shows the structure of the electric current detection sensor board | substrate which concerns on embodiment of this invention. The figure explaining the structure of the wiring pattern of the electric current detection sensor board | substrate shown in FIG. Equivalent circuit model for capacitive coupling Equivalent circuit model for inductive coupling. The figure explaining the drive circuit of the piezoelectric element which concerns on a prior art The figure explaining the modification of the drive circuit of the piezoelectric element which concerns on a prior art The figure explaining an example of a drive signal

Explanation of symbols

  12K, 12C, 12M, 12Y, 50 ... head, 58 ... piezoelectric element, 84 ... head driver, 92 ... current detection unit, 96 ... determination unit, 98 ... display unit, 100 ... drive circuit, 101 ... drive circuit board, 130 ... Drive signal line, 130A, 147A ... Via, 147 ... Detection signal line, 160 ... Test drive circuit

Claims (19)

A drive signal line that is electrically connected to an output terminal of a drive circuit that supplies a drive current to a driven element including a capacitive load, and that transmits the drive signal;
A detection signal line that is disposed in proximity to the drive signal line via a dielectric, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction part are formed in the same substrate. substrate. The current detection sensor substrate according to claim 1,
An insulating layer including at least three wiring layers and including a dielectric is provided between the wiring layers,
The wiring layer provided with the drive signal line has a structure sandwiched between the wiring layers provided with the detection signal line via the insulating layer, and the detection signal line is electromagnetically coupled with the drive signal line. A current detection sensor substrate characterized by obtaining characteristics. In the current detection sensor substrate according to claim 2,
The current detection sensor substrate, wherein the detection signal line has a predetermined area. In the current detection sensor substrate according to claim 2 or 3,
The drive signal lines include drive signal interlayer wirings that electrically connect drive signal lines provided in different wiring layers through insulating layers between different wiring layers,
The current detection sensor substrate, wherein the detection signal line includes a detection signal interlayer wiring disposed so as to pass through an insulating layer between different wiring layers and surround the drive signal interlayer wiring. A drive signal line that is electrically connected to an output terminal of a drive circuit that supplies a drive current to the capacitive load and transmits the drive signal;
A detection signal line which is disposed so as to surround the drive signal line via an insulator, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction part are formed in the same substrate. substrate. In the current detection sensor substrate according to claim 5,
Having at least two wiring layers;
The drive signal lines include drive signal interlayer wirings that electrically connect drive signal lines provided in different wiring layers through insulating layers between different wiring layers,
The detection signal line includes a detection signal interlayer wiring disposed so as to surround the drive signal interlayer wiring through an insulating layer between different wiring layers, and obtains electromagnetic coupling characteristics. substrate. A drive signal generator for generating a drive signal;
An output terminal for supplying a drive signal generated by the drive signal generator to a driven element having a capacitive load;
A drive signal line that is electrically connected to the driven element and the output end and transmits the drive signal;
A detection signal line that is disposed in proximity to the drive signal line via a dielectric, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The capacitive load, wherein the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate. Drive device. The capacitive load driving device according to claim 7,
5. The capacitive load driving device according to claim 2, wherein the substrate includes the current detection sensor substrate according to any one of claims 2 to 4. A drive signal generator for generating a drive signal;
An output terminal for supplying a drive signal generated by the drive signal generator to a driven element having a capacitive load;
A drive signal line that is electrically connected to the driven element and the output end and transmits the drive signal;
A detection signal line which is disposed so as to surround the drive signal line via an insulator, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The capacitive load, wherein the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate. Drive device. The capacitive load driving device according to claim 9, wherein
The capacitive load driving device according to claim 6, wherein the substrate includes the current detection sensor substrate according to claim 6. A liquid discharge head comprising a piezoelectric actuator that applies discharge pressure to the liquid discharged from the nozzle;
A drive signal generator for generating a drive signal supplied to the piezoelectric actuator;
A drive signal line that is electrically connected to an output end of the drive signal generation unit and transmits the drive signal;
A detection signal line that is disposed in proximity to the drive signal line via a dielectric, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The liquid ejection head, wherein the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate. Drive device. In the liquid discharge head drive device according to claim 11,
5. A liquid ejection head driving apparatus, wherein the substrate includes the current detection sensor substrate according to claim 2. A drive signal generating unit that generates a drive signal supplied to a piezoelectric actuator provided in a liquid discharge head that discharges liquid from a nozzle;
A drive signal line that is electrically connected to an output end of the drive signal generation unit and transmits the drive signal;
A detection signal line which is disposed so as to surround the drive signal line via an insulator, and an induced current is induced by a current of the drive signal transmitted by the drive signal line;
A detection signal extraction unit for extracting an induced current induced in the detection signal line as a detection signal;
With
The liquid ejection head, wherein the drive signal line and the detection signal line are formed as a wiring pattern, and the drive signal line, the detection signal line, and the detection signal extraction portion are formed in the same substrate. Drive device. The liquid ejection head drive device according to claim 13,
The liquid discharge head driving device according to claim 6, wherein the substrate includes the current detection sensor substrate according to claim 6. The liquid discharge head drive device according to any one of claims 11 to 14,
A liquid ejection head drive comprising: an abnormality determination unit that determines whether or not there is an abnormality in at least one of the piezoelectric actuator and the drive signal line based on a current of a drive signal detected by the detection signal line apparatus. The liquid discharge head driving device according to claim 15,
The abnormality determination unit includes a capacitance determination unit that determines a displacement amount of a capacitance with respect to a reference capacitance in the piezoelectric actuator, a short-circuit determination unit that determines whether or not the drive signal line is short-circuited, and the drive signal A liquid discharge head driving device comprising: at least one of open determination units for determining whether or not a line is open. The liquid discharge head drive device according to any one of claims 11 to 16,
The abnormality determining unit stores an abnormal state for a predetermined period, and an abnormal state storage unit;
Informing means for informing an abnormal state when at least one of the piezoelectric actuator and the drive signal line is abnormal;
A liquid discharge head driving device comprising: The liquid discharge head driving device according to any one of claims 11 to 17,
A liquid ejection head drive device comprising: a test drive circuit that generates a test drive signal having a slew rate higher than a drive signal generated by the drive circuit. A liquid discharge head for discharging liquid from a nozzle;
A liquid discharge head driving device according to any one of claims 11 to 18,
A liquid ejection apparatus comprising:

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