JP2010069679A - Method for inspecting capacitive load, driver of capacitive load and image forming device - Google Patents

Abstract

A method for inspecting the capacity of a plurality of capacitive loads such as piezoelectric elements, and a capacitive load driving apparatus and an image forming apparatus having such an inspection function are provided.
A plurality of capacitive loads (102) are arranged in parallel between a power supply line (104) and a ground (106) in correspondence with each capacitive load of a capacitive load group. By controlling the switching elements (PZ_SW1 to n) and selectively applying a DC voltage to any one of the plurality of capacitive loads to charge the capacitive load according to the selection, the capacitive load The information which shows the charge characteristic of is acquired. At the time of charging, a current regulating resistor (R_i) is inserted through the switch element (SW_2), and the charging current is narrowed to moderate the rising curve of the charging voltage and improve the measurement accuracy. Further, the capacity of each capacitive load can be obtained from comparison with information indicating the charging characteristics of the reference capacitive load (C_Ref) connected via the switch element (SW_3).
[Selection] Figure 7

Description

  The present invention relates to a capacitive load inspection technique, and in particular, a capacitive load inspection method suitable for measuring a capacitance of a piezoelectric element as a pressure generating element corresponding to each nozzle in an inkjet head having a plurality of nozzles, and the inspection. The present invention relates to a capacitive load driving device and an image forming apparatus having a function.

  As a means for ejecting droplets from a nozzle in a recording head (inkjet head) such as an ink jet recording apparatus, a piezoelectric element (piezo actuator) is provided corresponding to a pressure chamber communicating with the nozzle, and a driving voltage is applied to the piezoelectric element. A system is known in which ink droplets are ejected from nozzles by changing the volume of the pressure chamber (Patent Documents 1 and 2).

  In Patent Document 1, in order to solve the problem that the discharge amount varies due to the waveform disturbance of the drive signal caused by the change in the capacitance value of the load as viewed from the drive circuit due to the change in the number of nozzles that perform discharge, the capacitance value is made substantially constant. It is proposed to connect a capacitive dummy load to keep.

Patent Document 2 describes a technique of measuring a drive waveform applied to a capacitive load and monitoring whether the drive waveform is correct.
JP 11-320872 A JP 2007-276213 A

  Piezoelectric elements corresponding to each nozzle have variations in characteristics (capacitance) among the elements due to variations caused by manufacturing processes and deterioration over time due to use. Such variations in piezoelectric elements cause variations in ejection performance. Conventionally, a technique for grasping the ejection characteristics of a nozzle from a droplet ejection result such as a test pattern and performing correction is known, but a technique for measuring the capacitance of each piezoelectric element has not been proposed.

  The present invention has been made in view of such circumstances, and provides a method for inspecting the capacity of a plurality of capacitive loads, and also provides a capacitive load driving apparatus and an image forming apparatus having such an inspection function. For the purpose.

  In order to achieve the above object, a capacitive load inspection method according to the present invention is applied to each capacitive load of a capacitive load group in which a plurality of capacitive loads are arranged in parallel between a power supply line and a ground. A capacitive load inspection method in a circuit for driving the capacitive load by applying a driving voltage to the switch, the switch element provided corresponding to each of the plurality of capacitive loads, Information indicating charging characteristics of the capacitive load by selectively applying a DC voltage from the power supply line to charge the capacitive capacitive load according to the selection with respect to any of the plurality of capacitive loads. It is characterized by acquiring.

  According to the present invention, charging characteristics can be individually examined for a plurality of capacitive loads, and the capacity value of each capacitive load can be measured and abnormality / failure can be determined from the information.

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

[Overall configuration of inkjet recording apparatus]
First, an example of an ink jet recording apparatus to which the present invention is applied will be described. 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.

  The ink storage / loading unit 14 has an ink supply tank that stores inks of colors corresponding to the heads 12K, 12C, 12M, and 12Y. The inks of the respective colors are supplied to the heads 12K, 12C, 12M and 12Y communicate with each other.

  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.

  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.

  After the decurling process, the recording paper 16 cut to a predetermined size by the cutter 28 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. Instead of the suction (negative pressure) suction method, an electrostatic suction method may be adopted.

  The power of the motor (not shown in FIG. 1 and indicated by reference numeral 88 in FIG. 6) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that 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.

  A belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the printing 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.

  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). Each of the heads 12K, 12C, 12M, and 12Y is fixedly installed so as to extend along a direction substantially orthogonal to the conveyance direction of the recording paper 116.

  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.

  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 (imaging device) for imaging the droplet ejection result of the printing unit 12, and nozzle clogging and the like from the droplet ejection image read by the image sensor It functions as a means for checking discharge abnormality. 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.

  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. 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 perspective plan view showing another example of the structure of the head 50, and FIG. 4 is a diagram showing a droplet discharge element for one channel (an ink chamber unit corresponding to one nozzle 51) serving as a recording element unit. It is sectional drawing (sectional drawing in alignment with line 4-4 in Fig.3 (a)) which shows a three-dimensional structure.

  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 (nozzles 51, which are ink droplet ejection holes, and pressure chambers 52 corresponding to the nozzles 51). It has a structure in which the droplet discharge elements 53 are arranged in a staggered matrix (two-dimensionally), so that they are arranged along the longitudinal direction of the head 50 (main scanning direction perpendicular to the paper feed direction). High density of the substantial nozzle interval (projection nozzle pitch) projected onto the screen 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 an outlet to the nozzle 51 is provided at one of the diagonal corners, and the supply ink is provided at the other. Inflow port (supply port) 54 is provided. The shape of the pressure chamber 52 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon and other polygons, a circle, and an ellipse.

  The pressure chamber 52 communicates with the common flow channel 55 through the supply port 54. The common channel 55 communicates with an ink supply tank (not shown) as an ink supply source, and the ink supplied from the ink supply tank is distributed and supplied to each pressure chamber 52 via the common channel 55.

  A piezoelectric element 58 having individual electrodes 57 is joined to a diaphragm 56 that constitutes a part of the pressure chamber 52 (the top surface in FIG. 4) and also serves as a common electrode. By applying a drive voltage between the individual electrode 157 and the common electrode, the piezoelectric element 58 is deformed to change the volume of the pressure chamber 52, and ink is ejected from the nozzle 51 due to the pressure change accompanying this.

  When ink is ejected, new ink is supplied (refilled) from the common flow channel 55 through the supply port 54 to the pressure chamber 52.

  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, by adopting a structure in which a plurality of ink chamber units 53 are arranged in the direction of the angle θ at a fixed pitch d in the main scanning direction, the pitch P _N of the nozzles projected so as to align in the main scanning direction is d × cosθ next, the main scanning direction, substantially hence the nozzles 51 can be handled as the equivalent arranged linearly at a fixed pitch P _N.

  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.

[Explanation of control system]
FIG. 6 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, an image buffer memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit (image input means) 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 ROM 75 stores programs executed by the CPU of the system controller 72 and various data necessary for control (including ejection waveform data for image formation and ejection waveform for idle driving). The ROM 75 may be a non-rewritable storage means, or may be 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. 6, the motor 88 arranged in each part in the apparatus is represented by reference numeral 88.

  The heater driver 78 is a driver that drives various heaters 89 including the heater of the post-drying unit 42 shown in FIG. 1 in accordance with instructions 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 an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  An overview of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 70 and stored in the memory 74. At this stage, for example, RGB multi-valued image data is stored in the memory 74.

  The original image (RGB) data stored in the memory 74 is sent to the print control unit 80 via the system controller 72, and the print control unit 80 uses the halftoning process using a threshold matrix, error diffusion method, etc. It is converted into dot data (binary data or multi-value data including dot size information) for each color (K, C, M, Y).

  Thus, the dot data generated by the print control unit 80 is stored in the image buffer memory 82. The dot data for each color is converted into CMYK droplet ejection data for ejecting ink from the nozzles of the head 50, and the ink ejection data to be printed is determined.

  The head driver 84 is a drive signal for driving the piezoelectric elements 58 corresponding to the respective nozzles 51 of the head 50 based on print data (that is, dot data stored in the image buffer memory 82) given from the print control unit 80. Is output. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  The ink jet recording apparatus 10 shown in this example applies a common drive waveform signal to each piezoelectric element 58 and turns on / off the switch element connected to the individual electrode of each piezoelectric element 58 according to the ejection timing of each piezoelectric element 58. By switching, the driving method of the piezoelectric elements 58 that discharge ink from the nozzles corresponding to the piezoelectric elements 58 is applied.

  When a drive signal output from the head driver 84 is applied to the head 50, ink is ejected from the corresponding nozzle 51. An image is formed on the recording paper 16 by controlling the ink ejection from the head 50 while conveying the recording paper 16 at a predetermined speed.

  As described above, based on the ink discharge data and the drive signal waveform generated through the required signal processing in the print control unit 80, control of the discharge amount and discharge timing of the ink droplets from each nozzle via the head driver 84. Is done. Thereby, a desired dot size and dot arrangement are realized.

  As described with reference to FIG. 1, the print detection unit 24 is a block including an image sensor, reads an image printed on the recording paper 16, performs necessary signal processing, etc. And the detection result is provided to the print controller 80 and the system controller 72.

  The print control unit 80 performs various corrections on the head 50 based on information obtained from the print detection unit 24 as necessary, and performs cleaning operations (nozzle recovery operation) such as preliminary ejection, suction, and wiping as necessary. Perform the controls to be implemented.

[Means for inspecting the capacitance of piezoelectric elements]
Next, a configuration for performing a capacitance inspection of the piezoelectric element will be described. FIG. 7 is a circuit configuration diagram for measuring the capacitance of the piezoelectric element in the head 50.

  In FIG. 7, reference numeral 100 surrounded by an alternate long and short dash line is a head assembly constituting the head 50 described in FIGS. 3 to 5. In FIG. 7, PZT-i (i = 1 to n) indicated by reference numeral 102 represents each piezoelectric element (corresponding to reference numeral 58 in FIG. 5) in the head assembly 100.

  As illustrated, the piezoelectric elements PZT-i (i = 1 to n) are arranged in parallel between the common power supply line 104 and the ground line 106, and each piezoelectric element PZT-i (i = 1 to n). Are respectively connected in series with switch elements PZ_SWi (i = 1 to n). The switch element PZ_SWi (i = 1 to n) is a voltage supply switch provided in a normal head driver (piezoelectric element drive IC).

  This switch element PZ_SWi (i = 1 to n) is a switch for switching supply (ON) / cutoff (OFF) of a drive voltage to each piezoelectric element PZT-i (i = 1 to n), and the voltage supply switch element PZ_SWi. By controlling (i = 1 to n), a driving voltage can be selectively applied to each piezoelectric element PZT-i (i = 1 to n). It is possible to sequentially drive a part or all of the piezoelectric element group consisting of the piezoelectric elements PZT-i (i = 1 to n) one by one, or to drive part or all of the piezoelectric element group simultaneously. Is possible.

  During printing, the voltage supply switch element PZ_SWi (i = 1 to n) is on / off controlled by the control unit 120 based on the print data. When the voltage supply switch element PZ_SWi is turned on, the voltage supply switch element PZ_SWi is turned on. On the other hand, a drive voltage (for example, +30 V) is applied from the head drive circuit 110.

  Although the detailed configuration of the head drive circuit 110 is not shown, the head drive circuit 110 is a waveform data string output from a waveform data storage unit in which digital waveform data of a drive signal applied to the piezoelectric element when ink is ejected is stored. A D / A converter that converts (digital data) into an analog signal, an operational amplifier (voltage amplifier) that amplifies the analog signal waveform output from the D / A converter, and the output of this operational amplifier drives a piezoelectric element. A power amplifying unit (for example, an amplifying circuit composed of push-pull connected transistors) that amplifies the current / voltage suitable for the above-described configuration is included.

  The power supply line 104 (drive voltage output line) connected to the output terminal of the head drive circuit 110 is provided with a switch element SW_1. The piezoelectric element group PZT-i (in the head assembly 100) by the switch element SW_1. Supply (ON) / cutoff (OFF) of voltage to i = 1 to n) can be switched. The switch element SW_1 can be replaced with a normal discharge drive switch.

  In the head drive unit (circuit board) 122 on which the head drive circuit 110 is mounted, the charge delay circuit 108 is provided in parallel with the switch element SW_1 on the power supply line 104. The charge delay circuit 108 limits the current charged in the piezoelectric element PZT-i (i = 1 to n) and delays the charging time when inspecting the capacitance of the piezoelectric element PZT-i (i = 1 to n). The resistor R_i (corresponding to “current regulating resistor”) and the switch element SW_2 are included, and the switch element SW_2 can be switched between addition and release (separation) of the resistor R_i.

  Further, in the head assembly 100 of this example, a reference capacitor C_Ref (corresponding to “reference capacitive load”) is arranged in parallel with the piezoelectric element group PZT-i (i = 1 to n), and is switched by the switch element SW_3. The connection / release of the reference capacity C_Ref can be switched. The reference capacitance C_Ref is a reference capacitance that serves as a reference for comparison when the capacitance of each piezoelectric element is measured based on the charging characteristics, and the switch element SW_3 is used to connect the reference capacitance C_Ref to a circuit. Switch.

  As shown in FIG. 7, it is desirable that the switch element SW_3 and the reference capacitor C_Ref are mounted in the head assembly 100. However, when the present invention is implemented, the switch element SW_3 and the reference capacitor C_Ref are mounted in the drive circuit. May be.

  A monitor signal (detection signal for monitoring the voltage) is extracted from the terminal 124 of the power supply line 104 via the switch element SW_4, and the control unit 120 monitors the voltage value. That is, the switch element SW_4 is a monitor connection switch used when monitoring the charging characteristics of the piezoelectric element. The monitor signal is input to an analog input port of the CPU in the control unit 120 or an A / D converter input port, converted into digital data, and stored in the memory 126. A memory 126 in the figure corresponds to the memory 74 described in FIG.

  Further, the head driving unit 122 of this example includes a discharge resistor R_s (corresponding to a “forced discharge circuit”) for forming a discharge path for forcibly discharging the residual charge of the piezoelectric element after the charge characteristics are examined. A switch element SW_5 is provided.

  The control unit 120 controls ON / OFF of each of the switch elements SW_1 to SW_5 and acquires information on the charging voltage. The control unit 120 is a block corresponding to the print control unit 80 and the system controller 72 described in FIG.

  In the circuit shown in FIG. 7, the piezoelectric element PZT-i (i = 1 to n) corresponds to a “capacitive load”, and the voltage supply switch element PZ_SWi corresponds to a “first switch element”. The switch element SW_3 corresponds to a “second switch element”, and the switch element SW_2 corresponds to a “third switch element”. The switch element SW_5 corresponds to a “fourth switch element”.

〔Measurement procedure〕
Next, a procedure for measuring the capacitance of the piezoelectric element with the above circuit configuration will be described.

  (Procedure 1): First, all of the voltage supply switch elements (PZ_S1 to n) and the switch elements SW_1 and SW_5 connected in series to each piezoelectric element of the head assembly 100 are turned off (open).

  (Procedure 2): With the switch elements SW_3 and SW_4 turned on (closed), the switch element SW_2 is turned on (closed), a DC voltage is applied to the reference capacitor C_Ref, and the reference capacitor C_Ref is charged.

  (Procedure 3): The time change of the charging voltage at this time is monitored, the obtained charging characteristic curve (voltage rising curve) is acquired as the reference charging characteristic, and the data is stored in the memory 126.

  (Procedure 4): After acquiring the charging characteristic curve data by monitoring the charging voltage for a predetermined time period set in advance, the switch elements SW_2 and SW_4 are turned OFF (open) and the switch element SW_5 is turned ON (closed) ) State, the residual charge is forcibly discharged to the ground (GND). After that, when the discharge is completed to a level that does not hinder the next measurement, the switch element SW_5 is turned off again.

  (Procedure 5): Next, the switch element SW_3 is turned off (opened), and each of the piezoelectric elements PZT-i (i = 1 to n) corresponding to the respective switches from PZ_SW1 to PZ_SWn in the head assembly 100 In addition, the charging characteristics are obtained in the same order as in the above steps 2 to 4 (by controlling the switch element PZ_SWi instead of the switch element SW_3).

  (Procedure 6) The capacitance of each element is calculated by comparing the discharge characteristics of each piezoelectric element acquired in Procedure 5 with the discharge characteristics of the reference capacity acquired in Procedure 3.

  For example, if the difference in time versus voltage level is within a certain level compared to the reference characteristic (memory characteristic), the allowable range (equivalent capacity) is set, and the capacity is calculated stepwise within a certain level range.

  FIG. 8 shows an example of charging characteristics.

  Let T be the time (charge time) from when the switch element SW_2 is turned on until it reaches (rises) a certain voltage Vd. When the capacity of the piezoelectric element is large compared to T when charging the reference capacity C_Ref (T_ref in the charging characteristic curve [1]), the charging time is slow (T_2 in the charging characteristic curve [2]), and the capacity is small The discharge time is shortened (T_3 in the charge characteristic curve [3]).

  That is, if T in the charging characteristic curve of the piezoelectric element is a value smaller than T_ref (T <T_ref), the capacitance Ci of the piezoelectric element is Ci <C_Ref, and T is larger than T_ref (Tref <T ), The capacitance Ci of the piezoelectric element is C_Ref <Ci.

  Based on the time difference between the charging time T_ref of the reference capacity C_Ref and the discharging time T of the piezoelectric element of interest, the capacity of the piezoelectric element is calculated. In specifying the capacitance value, an operation may be performed from a calculation formula, or a table may be used.

  As described with reference to FIG. 7, the charging time can be extended by adding a charging delay resistor (current regulating resistor) indicated by the symbol R_i to the charging circuit. Thereby, the difference in charging time due to the difference in capacity can be expanded, and the difference in capacity can be clearly obtained.

[Second Embodiment]
In the first embodiment, when the charging time T is determined, the monitor signal is input to the analog input port of the CPU in the control unit 120 or the A / D converter input port, and the time until the value reaches the specified voltage. However, as in the circuit shown in FIG. 9, it is also possible to input the monitor signal to the comparator 140 and count the arrival time until the predetermined reference voltage Vref is reached by the CPU 142. The CPU 142 calculates the capacitance of the piezoelectric element based on the obtained arrival time (charging time T).

  By setting this reference voltage (reference voltage) Vref low, the time until detection can be shortened, and the detection time can be shortened. That is, it is not necessary to repeat acquisition of time until each element is fully charged, and measurement time can be shortened by making a determination based on the time until reaching a predetermined reference voltage value.

[Third Embodiment]
In the first and second embodiments, the capacity is obtained by comparing the arrival time with the reference capacity C_Ref based on the time from when charging is started (timing when the switch element SW_2 is turned on) to reach a specified voltage. However, the capacity may be calculated by comparing the charging voltage with the reference capacity based on the charging voltage at a certain elapsed time.

[Fourth Embodiment]
In addition, since an error may be included in one measurement, a mode in which the error is removed by performing a series of charging characteristics acquisition several to several tens of times and obtaining the capacity with the average value thereof is preferable.

  In addition, when the charging characteristic curve is repeatedly obtained for the same element, if the next charging is performed before it is completely discharged, an error occurs in the second and subsequent charging times. In order to solve this problem, the switch element SW_5 is turned on (closed) to forcibly discharge the residual charge, so that it is possible to shift to the next charging operation, and the measurement time can be shortened.

[Fifth Embodiment]
The timing at which the above-described measurement of the capacity is performed is not particularly limited, but a change with time in the capacitive load or the like can be measured by periodically performing the measurement. It is also possible to detect the occurrence of a failure or abnormality in the capacitive load by such regular measurement.

[Sixth Embodiment]
In the above-described embodiment, the capacity was calculated based on the difference in charging time based on the reference capacity C_Ref. Alternatively, the capacity may be obtained based on this.

[Seventh Embodiment: Correction of Capacity Variation]
The ejection drive waveform to the piezoelectric element is generally driven with the same waveform in order to eject a certain droplet without considering the capacitance error of the piezoelectric element. Therefore, when the capacitance variation of the piezoelectric elements is large, the discharge state for each element is not constant, and a desired droplet amount and discharge speed cannot be realized. For this reason, the intended image quality cannot be obtained. The variation in the capacitance of the piezoelectric element can be grasped in advance by the above-described calculation method, the drive waveform is optimized according to the size of the capacitance, and deterioration of the image quality can be prevented.

  In an ink jet recording apparatus, a desired image quality is generally obtained by adjusting (changing) the state of ink landing on a medium such as photographic paper according to the ink discharge speed, the amount of liquid droplets, the discharge timing, and the like. By varying the waveform (ink ejection waveform), peak value, rising / falling slew rate, waveform width (timing), etc. of the drive voltage applied to the piezoelectric element, the ink ejection state is varied.

  FIG. 10 is an example of an ink ejection waveform using a typical piezoelectric element. The ink ejection state (landing state) is determined by the drive waveform when the media conditions such as ink and recording paper, and the mechanical positional relationship and structure are the same. Determinants of the ejection state in the drive waveform at this time include a peak value, a rising / falling slew rate, a waveform width (timing), and the like.

  However, when there is a large variation in the capacitance of the piezoelectric elements, there arises a problem that the desired stable ink ejection state cannot be obtained even when all elements are ejected with the same drive waveform.

  The following measures can be considered as means for solving this problem.

  (1) The amount of liquid droplets discharged and the landing state are stabilized by adjusting the energy applied to the piezoelectric element due to the difference in capacity and the drive waveform. Specifically, the drive waveform is adjusted by the following methods (1-a) to (1-c) to stabilize the ejection state.

  (1-a) The voltage value is varied by enlarging / reducing the peak value of the drive waveform.

  (1-b) Increase or decrease the slew rate.

  (1-c) The vibration period of the piezoelectric element is changed by shifting the waveform width (timing in the time direction) from the resonance frequency.

  Such adjustment of the drive waveform is performed for a waveform that is applied to each piezoelectric element.

  (2) However, the above (1) is often difficult to implement in practice because of complicated circuit.

  Therefore, it is conceivable to measure the capacity tendency of the head (piezoelectric element group) mounted on the device for each drive circuit block and adjust the drive waveform according to the center value for each block. For example, the following methods (2-a) and (2-b) are used.

  (2-a) The voltage value is varied for each load (element) block of the piezoelectric element group block to which the drive voltage is commonly supplied from the same drive circuit.

  (2-b) As shown in FIG. 11, a fixed-value dummy capacitor Cd is added in units of circuit blocks to the block 152 of the piezoelectric element group to which the drive voltage is commonly supplied from the same drive circuit 150. Further, instead of adding the dummy capacitor Cd or in combination with it, a resistor R0 is inserted into the series in units of circuit blocks (see FIG. 11).

  (3) As described in (1) above, when there is a large variation in the capacitance of piezoelectric elements in the same head, it is desirable to change the drive waveform to be applied for each element, but the circuit configuration becomes complicated. Have difficulty. Therefore, the discharge state due to the capacity variation is measured in advance and acquired as information. This information is fed back to the image processing to correct the target ejection droplet pattern. For example, the following methods (3-a) and (3-b) are used.

  (3-a) When the droplet discharge size (dot size) can be changed to three types of large droplets, medium droplets, and small droplets, large droplets are corrected to medium droplets, and medium droplets are corrected to large droplets. (Medium drop medium drop), medium drop is corrected to small drop, small drop is corrected to medium drop (medium drop ⇔ small drop).

  (3-b) Also, one large drop is corrected to a small drop × 2 drops (large drop 1 drop → small drop × 2 drops).

  FIG. 12A shows an example of a driving waveform when one large droplet is ejected, and FIG. 12B shows a driving waveform when two small droplets are ejected instead of one large droplet. It is an example.

  Thus, by driving with a waveform corresponding to the capacity of the piezoelectric element, an appropriate landing state can be realized. Thereby, the stability of the image quality is improved, and the image quality can be improved.

  In addition, since the correction contents due to the capacity difference are determined in advance, the same correction can be performed for the capacity fluctuation due to the change with time, and therefore it is possible to cope with the deterioration with time.

  Furthermore, (1) to (3) related to the above correction technique have described examples in which the drive waveform is changed, but this content is included in the image quality design (correction) in the image processing process to correct the density gradation. You may respond by doing.

[Eighth Embodiment; About Failure Detection]
FIG. 13 shows an example of the charging characteristics of the piezoelectric element capacitance at the time of abnormality. When the capacity becomes extremely small due to a failure, the charge characteristic curve draws a curve as shown in [4] in the figure (a curve in which the discharge time T to the specified voltage Vd becomes Tdet).

  Thus, paying attention to the charging curve of the piezoelectric element, when the charging time T deviates from the normal variation allowable range Tmin to Tmax, it is determined that there is a failure or abnormality.

  As a determination method, there is a method of determining from a measurement result of a charge voltage value after a specified time from SW_2_ON, in addition to a method of determining by the time until reaching the set voltage Vd from SW_2_ON as described above.

  In addition, when the capacity | capacitance falls remarkably, it can be judged that the capacity | capacitance reduction by load short circuit failure. Further, when the capacity increases (for example, increases by about 2 times), contact with an adjacent load or the like can be considered.

  As described above, the following effects can be obtained by the embodiment of the present invention.

  (1) Since the capacitance variation of each piezoelectric element can be measured, it is possible to grasp the abnormality / trend for each lot retroactively at the time of piezo manufacturing.

  (2) When investigating the charging characteristics, by adopting a configuration in which the current regulating resistor (R_i) is inserted in series in the power supply line 104, the charging curve can be moderated to improve the measurement accuracy.

  (3) By grasping the variation of the piezoelectric elements, the image quality can be improved by performing the correction for each element (voltage correction of the driving waveform, duty correction, etc.).

  (4) Since the capacity of all the piezoelectric elements can be investigated, it is possible to detect a faulty or abnormal piezoelectric element.

  (5) Since the inkjet recording apparatus can be measured in a normal operation state, it is not necessary to disassemble the machine for inspection, and no unnecessary man-hours are generated.

  (6) It is possible to periodically inspect the deterioration and abnormality of the piezoelectric element.

[Modification]
In the above embodiment, an ink jet recording apparatus of a method (direct recording method) in which an ink droplet is directly formed on the recording paper 16 has been described. However, the scope of application of the present invention is not limited to this, and once, The present invention is also applied to an intermediate transfer type image forming apparatus that forms an image (primary image) on an intermediate transfer member and transfers the image onto a recording sheet in a transfer unit to form a final image. be able to.

  Further, in the above embodiment, an inkjet recording apparatus using a page-wide full-line head having a nozzle row having a length corresponding to the entire width of the recording medium (single-pass image for completing an image by one sub-scanning). However, the scope of application of the present invention is not limited to this, and an inkjet that performs image recording by scanning a plurality of heads while moving a short recording head such as a serial (shuttle scan) head. The present invention can also be applied to a recording apparatus.

  In addition, in the interpretation of the term "image forming apparatus", it is not limited to the use of so-called graphic printing such as photographic printing or poster printing, such as a resist printing apparatus, a wiring drawing apparatus for an electronic circuit board, a fine structure forming apparatus, etc. An industrial use apparatus capable of forming a pattern that can be grasped as an image is also included.

  Furthermore, in the above-described embodiment, an example in which a piezoelectric element is used as a capacitive load has been described. However, the scope of application of the present invention is not limited to this, and the present invention can be similarly applied to an electrostatic actuator, a liquid crystal, and the like.

[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 the invention described below.

  (Invention 1): Driving a capacitive load by applying a drive voltage to each capacitive load of a capacitive load group in which a plurality of capacitive loads are arranged in parallel between a power supply line and a ground. A method for inspecting a capacitive load in a circuit, wherein a switch element provided corresponding to each of the plurality of capacitive loads is controlled to selectively select one of the plurality of capacitive loads. A capacitive load inspection method characterized by acquiring information indicating charging characteristics of a capacitive load by applying a DC voltage from a power supply line and charging the capacitive load according to the selection.

  According to the present invention, it is possible to selectively form a charging path for each capacitive load and to check a charging characteristic for each capacitive load by controlling the switch element. Then, the capacity can be measured from the obtained charging characteristic information, and it is possible to determine the presence or absence of a failure / abnormality. Note that the charging characteristics may be sequentially checked for all the capacitive loads in the capacitive load group, or the charging characteristics may be checked for a part of the capacitive loads.

  (Invention 2): In the capacitive load inspection method according to Invention 1, a reference capacitive load having a reference capacitance value is arranged in parallel with the capacitive load group, and connection / release of the reference capacitive load is performed. Information indicating the charging characteristics of the reference capacitive load by controlling the switch element to selectively charge the reference capacitive load by applying a DC voltage from the power supply line. And obtaining the capacity of the capacitive load based on the information indicating the charging characteristics of the reference capacitive load and the information indicating the charging characteristics of the capacitive load.

  From the comparison between the discharge characteristics of the reference capacitive load and the discharge characteristics of each capacitive load, the capacity can be measured and the presence / absence of a failure / abnormality can be determined.

  (Invention 3): Capacitive negative inspection method according to Invention 1 or 2, wherein a current regulating resistor is inserted in series in the power supply line during the charging to limit the charging current. .

  The measurement accuracy can be improved by narrowing the current during charging rather than the driving current in normal load driving and delaying the charging time.

  (Invention 4): A capacitive load group in which a plurality of capacitive loads are arranged in parallel between the power supply line and the ground, and each capacitive load of the capacitive load group is provided corresponding to each capacitive load group, A plurality of switch elements that switch connection / release between a capacitive load and the power supply line, a drive circuit that supplies a voltage to the power supply line, and the switch element to control any one of the plurality of capacitive loads Control means for acquiring information indicating the charging characteristics of the capacitive load by selectively applying a DC voltage from the power supply line and charging the capacitive load according to the selection. Capacitive load driving device characterized by that.

  According to the present invention, charging characteristics can be acquired by selectively charging each capacitive load while controlling the switch element corresponding to each capacitive load. -The presence or absence of abnormality can be determined.

  (Invention 5): A capacitive load group in which a plurality of capacitive loads are arranged in parallel between the power supply line and the ground, and each capacitive load of the capacitive load group is provided corresponding to each capacitive load group, A plurality of first switch elements for switching connection / release between a capacitive load and the power supply line, a reference capacitive load arranged in parallel with the capacitive load group, the reference capacitive load, and the power supply line; A second switch element that switches connection / release of the power supply, a drive circuit that supplies a voltage to the power supply line, and the first and second switch elements to selectively supply the power to the reference capacitive load. Information indicating the charging characteristics of the reference capacitive load is obtained by charging by applying a DC voltage from the line, while DC is selectively transmitted from the power supply line for any of the plurality of capacitive loads. A capacitive load drive comprising: a control unit that obtains information indicating charging characteristics of the capacitive load by applying a pressure to charge the capacitive capacitive load according to the selection. apparatus.

  According to the present invention, while controlling the first and second switch elements, the respective capacitive loads of the reference capacitive load and the capacitive load group are selectively charged to charge the individual loads. The characteristics can be acquired, and the capacity can be measured and the presence / absence of a failure / abnormality can be determined by comparison with the charging characteristics of the reference capacitive load.

  (Invention 6): In the capacitive load driving device according to Invention 5, the control means calculates the capacity of the capacitive load from a comparison between a discharge characteristic of the reference capacitive load and a discharge characteristic of the capacitive load. Capacitive load driving device characterized by that.

  (Invention 7): In the capacitive load driving device according to any one of Inventions 4 to 6, the control means determines the load from a charging characteristic curve representing a relationship between a charging time and a charging voltage of the capacitive load. Capacitive load driving device characterized by calculating the capacity of

  (Invention 8): In the capacitive load driving device according to Invention 4 or 5, the capacitive load driving device includes storage means for storing a table defining a relationship between charging characteristics and capacity, and the control means is information indicating the acquired charging characteristics. And a capacitive load driving device that calculates the capacity of the capacitive load from the table.

  By previously storing the relationship between the discharge time and capacity of several capacities as a reference table, the capacity can be obtained based on this.

  (Invention 9): In the capacitive load driving device according to any one of Inventions 4 to 8, the current regulating resistor that limits the charging current at the time of charging and delays the charging time, and the power supply of the current regulating resistor A third switch element that switches connection / release to / from the line, wherein the third switch element is controlled by the control means, and the current regulating resistor is inserted into the power supply line during the charging. Capacitive load driving device.

  By narrowing the charging current in the charging process for performing the capacity inspection, the rate of increase of the charging voltage (charging speed) becomes gradual, and the voltage and its change over time can be accurately measured.

(Invention 10): In the capacitive load driving device according to any one of claims 4 to 9,
A forced discharge circuit for forcibly discharging residual charge remaining in the load after acquiring the charge characteristic information, and a fourth switch element for switching connection / release of the forced discharge circuit are provided. Capacitive load driving device.

  When necessary charging characteristic information is obtained, the inspection time can be shortened by forcibly discharging the residual charge.

  (Invention 11): The capacitive load driving device according to any one of Inventions 4 to 10, further comprising correction means for correcting operation variations caused by capacitance value variations of the plurality of capacitive loads. Capacitive load driving device characterized by the above.

  Examples of the correction means include a mode of correcting the drive waveform and a mode of adding a dummy capacitor and a resistance element in the circuit configuration.

  (Invention 12): In the capacitive load driving device according to any one of Inventions 4 to 11, the control means determines the presence or absence of abnormality of the load from information indicating a charging characteristic of the capacitive load. Capacitive load driving device characterized by the above.

  Instead of or in combination with the aspect of obtaining the capacity value from the charging characteristics, the presence / absence of a failure / abnormality can be determined. A failure is a form of “abnormal”.

  As an aspect of the capacitive load driving device according to any one of the third to eleventh aspects, for example, a liquid ejection device including a liquid ejection head that ejects droplets from nozzles by driving the capacitive load is provided.

(Invention 13): An image forming apparatus to which the capacitive load driving device according to any one of Inventions 4 to 12 is applied,
A liquid discharge head having a plurality of piezoelectric elements corresponding to the plurality of capacitive loads, and discharging droplets from corresponding nozzles by driving the piezoelectric elements, and droplets discharged from the liquid discharge heads are attached. An image forming apparatus comprising: a recording medium conveying unit that conveys the recording medium to be conveyed.

  An ink jet recording apparatus as an aspect of an image forming apparatus according to the present invention includes a nozzle (ejection port) for ejecting ink droplets for forming dots and a pressure generating element (piezoelectric element) for generating ejection pressure. A liquid discharge head (recording head) in which a large number of liquid droplet discharge elements (ink liquid chamber units) are arranged at high density, and the liquid discharge based on ink discharge data (dot image data) generated from an input image An ejection control unit that controls ejection of droplets from the head, and forms an image on the recording medium by droplets ejected from the nozzles.

  For example, color conversion and halftoning processing are performed based on image data (print data) input via the image input means, and ink ejection data corresponding to the ink color is generated. Based on this ink ejection data, the drive of the pressure generating element corresponding to each nozzle of the liquid ejection head is controlled, and an ink droplet is ejected from the nozzle.

  As a configuration example of such an ink jet recording head, a full line type head having a nozzle row in which a plurality of ejection openings (nozzles) are arranged over a length corresponding to the entire width of the recording medium can be used. In this case, a combination of a plurality of relatively short ejection head modules having a nozzle row less than the length corresponding to the entire width of the recording medium, and connecting them together, the nozzle having a length corresponding to the entire width of the recording medium as a whole There is an aspect that constitutes a column.

  A full-line type head is usually arranged along a direction perpendicular to the relative feeding direction (relative conveyance direction) of the recording medium, but has a certain angle with respect to the direction perpendicular to the conveyance direction. There may be a mode in which the head is arranged along the oblique direction.

  A “recording medium” is a medium (which can be called a printing medium, an image forming medium, a recording medium, an image receiving medium, a discharged medium, etc.) that receives adhesion of liquid droplets discharged from the discharge port of the head, and is continuous. Paper, cut paper, sealing paper, resin sheets such as OHP sheets, films, cloth, printed circuit boards on which wiring patterns are formed, intermediate transfer media, and other various media and shapes are included.

  The transporting means for moving the recording medium and the head relative to each other includes a mode for transporting the recording medium to the stopped (fixed) head, a mode for moving the head with respect to the stopped recording medium, or a head and recording Any aspect of moving both of the media is included. In addition, when forming a color image using an ink jet print head, a head may be arranged for each color of a plurality of inks (recording liquids), and a plurality of colors of ink can be ejected from one recording head. It is good also as a simple structure.

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 block diagram showing the configuration of a control system of the ink jet recording apparatus shown in FIG. Circuit configuration diagram according to the first embodiment Graph showing examples of charging characteristics curves Main part circuit diagram of 2nd Embodiment Waveform diagram showing examples of drive waveforms during ink ejection Explanatory drawing of 7th Embodiment Waveform diagram showing examples of ink ejection waveforms Graph showing an example of the charging characteristic curve at the time of abnormality

Explanation of symbols

  12K, 12C, 12M, 12Y, 50 ... head, 58 ... piezoelectric element, 72 ... system controller, 80 ... print controller, 84 ... head driver, 100 ... head assembly, 104 ... feed line, 106 ... ground line, 110 ... Head drive circuit, 112... Head drive unit, 120... Control unit, 126... Memory, PZ_SW 1 to PZ_SWn.

Claims (13)

Capacitive load in a circuit that drives the capacitive load by applying a drive voltage to each capacitive load of the capacitive load group in which a plurality of capacitive loads are arranged in parallel between the power supply line and the ground. The inspection method of
The switch element provided corresponding to each of the plurality of capacitive loads is controlled, and a DC voltage is selectively applied from any of the plurality of capacitive loads to the selection. A capacitive load inspection method characterized by acquiring information indicating charging characteristics of a capacitive load by charging the capacitive capacitive load. The capacitive load inspection method according to claim 1,
A reference capacitive load having a reference capacitance value is arranged in parallel with the capacitive load group, and a switch element for switching connection / release of the reference capacitive load is provided, and the reference capacitance is controlled by controlling the switch element. By selectively applying a direct-current voltage from the power supply line and charging the capacitive load, information indicating the charging characteristics of the reference capacitive load is obtained,
A capacitive load inspection method, wherein a capacity of the capacitive load is obtained based on information indicating charging characteristics of the reference capacitive load and information indicating charging characteristics of the capacitive load. In the capacitive load inspection method according to claim 1 or 2,
A capacitive load inspection method characterized by limiting a charging current by inserting a current regulating resistor in series with the feeding line during the charging. A capacitive load group in which a plurality of capacitive loads are arranged in parallel between the power supply line and the ground; and
A plurality of switch elements that are provided corresponding to each capacitive load of the capacitive load group, and that switch connection / release between each capacitive load and the power supply line;
A drive circuit for supplying a voltage to the power supply line;
By controlling the switch element and selectively applying a DC voltage from the power supply line to any one of the plurality of capacitive loads to charge the capacitive capacitive load according to the selection, Control means for acquiring information indicating the charging characteristics of the sexual load;
A capacitive load driving device comprising: A capacitive load group in which a plurality of capacitive loads are arranged in parallel between the power supply line and the ground; and
A plurality of first switch elements provided corresponding to the capacitive loads of the capacitive load group, respectively, for switching connection / release between the capacitive loads and the power supply line;
A reference capacitive load arranged in parallel with the capacitive load group;
A second switch element for switching connection / release between the reference capacitive load and the power supply line;
A drive circuit for supplying a voltage to the power supply line;
Information indicating charging characteristics of the reference capacitive load by controlling the first and second switch elements and selectively charging the reference capacitive load by applying a DC voltage from the power supply line. On the other hand, the capacitive load is charged by selectively applying a DC voltage from the power supply line to any one of the plurality of capacitive loads and charging the capacitive load according to the selection. Control means for acquiring information indicating the characteristics;
A capacitive load driving device comprising: The capacitive load driving device according to claim 5,
The capacitive load driving device characterized in that the control means calculates a capacity of the capacitive load from a comparison between a charging characteristic of the reference capacitive load and a charging characteristic of the capacitive load. The capacitive load driving device according to any one of claims 4 to 6,
The capacitive load driving device, wherein the control means calculates a capacity of the load from a charging characteristic curve representing a relationship between a charging time and a charging voltage of the capacitive load. The capacitive load driving device according to claim 4 or 5,
A storage means for storing a table defining the relationship between the charging characteristics and capacity;
The said control means calculates the capacity | capacitance of the said capacitive load from the information which shows the acquired said charge characteristic, and the said table, The capacitive load drive device characterized by the above-mentioned. The capacitive load driving device according to any one of claims 4 to 8,
A current regulating resistor that limits the charging current at the time of charging and delays the charging time; and
A third switch element for switching connection / opening of the current regulating resistor to the power supply line;
With
The capacitive load driving device, wherein the third switch element is controlled by the control means, and the current regulating resistor is inserted into the power supply line during the charging. The capacitive load driving device according to any one of claims 4 to 9,
A forced discharge circuit for forcibly discharging the residual charge remaining in the load after obtaining the charge characteristic information;
A fourth switch element for switching connection / release of the forced discharge circuit;
A capacitive load driving device comprising: The capacitive load driving device according to any one of claims 4 to 10,
A capacitive load driving device comprising correction means for correcting variation in operation caused by variation in capacitance values of the plurality of capacitive loads. The capacitive load driving device according to any one of claims 4 to 11,
The said control means determines the presence or absence of the abnormality of the said load from the information which shows the charge characteristic of the said capacitive load, The capacitive load drive device characterized by the above-mentioned. An image forming apparatus to which the capacitive load driving device according to any one of claims 4 to 12 is applied,
A liquid ejection head having a plurality of piezoelectric elements corresponding to the plurality of capacitive loads, and ejecting liquid droplets from corresponding nozzles by driving the piezoelectric elements;
An image forming apparatus comprising: a recording medium conveying unit that conveys a recording medium to which droplets ejected from the liquid ejection head are attached.

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