JP6766390B2 - Control method for a unit that ejects droplets, a droplet ejection device, and a droplet ejection head - Google Patents

Description

The present invention relates to a unit for ejecting droplets, a droplet ejection device, and a method for controlling a droplet ejection head.

Conventionally, in image formation by an inkjet method, it is known that when ink is ejected from an inkjet head, variations occur among a plurality of nozzles that eject droplets.

On the other hand, in Patent Document 1, the driving nozzles are grouped according to the nozzle arrangement position on the bottom surface of the nozzle, and the voltage value of the contraction pulse is changed according to the group.

However, in Patent Document 1, although the variation between the rows of the ejected nozzles is adjusted, the variation in the discharge volume due to the characteristics of the liquid chamber and the nozzle due to the manufacturing variation among a plurality of nozzles in the same row cannot be suppressed. It was.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a unit that ejects droplets that can suppress variations in ejection volume between a plurality of nozzles due to the characteristics of the liquid chamber and the nozzles.

In order to solve the above problems, in one aspect of the present invention, a plurality of nozzles for ejecting droplets, a plurality of liquid chambers communicating with each of the plurality of nozzles, and a plurality of liquid chambers for changing the volume of each of the plurality of liquid chambers. A droplet ejection head including a driving element of the above and two electrodes connected to each driving element; and a control unit for controlling the ejection of the droplet;
The two electrodes connected to each drive element include a first electrode and a second electrode in which a voltage that changes into a waveform is individually applied to each drive element.
By applying a voltage that changes to the waveform to the plurality of first electrodes and changing the potential difference between the two electrodes into a waveform, the plurality of driving elements change the volume of each of the corresponding liquid chambers.
The voltage that changes to the waveform is a driving portion in which the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes in front of the driving portion. It includes a voltage holding portion including a predetermined intermediate voltage, which has a predetermined potential difference.
In the control unit, the intermediate voltage of the voltage that changes to the waveform given to the first electrode connected to each drive element corresponding to each liquid chamber is set according to the characteristics of each liquid chamber and the nozzle. Provided is a unit for ejecting droplets, which is characterized in that correction is performed independently for each of the driving elements .

According to one aspect of the present invention, in the unit for ejecting droplets, it is possible to suppress variations in ejection volume among a plurality of nozzles due to the characteristics of the liquid chamber and the nozzles.

FIG. 5 is a cross-sectional view taken along the longitudinal direction of the liquid chamber of the droplet ejection head according to the embodiment of the present invention. FIG. 1A is a cross-sectional explanatory view of the droplet ejection head of FIG. 1A in the lateral direction (nozzle alignment direction) of the liquid chamber. The block diagram which shows the hardware configuration example of the image forming apparatus which concerns on one Embodiment of this invention. A bottom view and a side view showing a head surface of an example of a droplet ejection head included in the image forming apparatus according to an embodiment of the present invention. The block diagram which shows the structural example of the print control apparatus and the head driver which concerns on 1st Embodiment of this invention. The graph which shows an example of the drive waveform which concerns on 1st Embodiment of this invention. Explanatory drawing which shows the state of a meniscus and a drive pulse in a nozzle when a drive pulse waveform is applied. Explanatory drawing of an example of non-uniform droplet volume and an example of correction thereof The flowchart which shows the flow of control which concerns on 1st Embodiment of this invention. Schematic diagram of the liquid chamber when no applied voltage is applied. Schematic diagram around the nozzle, schematic diagram of the liquid chamber, and frequency characteristics when different intermediate potentials are applied to the liquid chamber with ideal characteristics. The schematic diagram of the liquid chamber, the driving waveform and the explanatory view of the frequency characteristic which explain the correction for the liquid chamber where the fluctuation amount of the liquid in a liquid chamber is large by the characteristic of a liquid chamber and a nozzle. The schematic diagram of the liquid chamber, the driving waveform and the explanatory view of the frequency characteristic which explain the correction for the liquid chamber which the fluctuation amount of the liquid in a liquid chamber is small by the characteristic of a liquid chamber and a nozzle. Graph showing the discharge droplet volume histogram before and after the correction It is a block diagram which shows the structural example of the print control apparatus and the head driver which concerns on 2nd Embodiment of this invention. Flow chart showing the flow of control according to the second embodiment of the present invention The schematic diagram which shows an example of the whole structure of the image forming apparatus which concerns on one Embodiment of this invention. The schematic diagram which shows an example of the whole structure of the image forming apparatus which concerns on one Embodiment of this invention. The schematic diagram which shows an example of the whole structure of the image forming apparatus which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the present specification and the drawings, the components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<Discharge head>
FIG. 1 is a cross-sectional view showing an example of a discharge head (droplet discharge head) according to an embodiment of the present invention. As shown in the figure, an individual flow path (hereinafter referred to as "pressurized liquid chamber") 6 is formed in the discharge head. Further, each nozzle 4 communicates with the pressurized liquid chamber 6. Further, the discharge head has a communication portion (restrictor) 9 provided with a diaphragm 2 for each pressurized liquid chamber 6. Further, the discharge head has a communication portion 9 formed in the flow path member 1.

Further, a common liquid chamber 8 is formed in the frame member 17. The common liquid chamber 8 supplies the recording liquid to each pressurized liquid chamber 6. Specifically, the recording liquid is supplied from the common liquid chamber 8 via the fluid resistance unit 7. A liquid, that is, a recording liquid is supplied from the common liquid chamber 8 to each pressurized liquid chamber 6 via a communication portion 9 formed in the diaphragm 2. The frame member 17 is provided with a recording liquid supply port in order to supply the recording liquid to the common liquid chamber 8 from the outside. Further, the common liquid chamber 8 is formed in a planar shape and a rectangular shape in the arrangement direction of the pressurized liquid chamber 6, that is, the arrangement direction of the nozzles (hereinafter, may be referred to as "longitudinal direction of the common liquid chamber"). Rectangle.

The flow path member 1 forms openings, grooves, and the like in the nozzle communication passage 5, each pressurized liquid chamber 6, the fluid resistance portion 7, the communication portion 10, and the like. These can be formed, for example, by performing anisotropic etching on a single crystal silicon substrate having a crystal plane orientation (Miller index 110) using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH). Further, when the SUS substrate is subjected to machining such as etching or punching using an acidic etching solution, each pressurized liquid chamber 6 can be formed. Further, the flow path member 1, the nozzle plate 3 and the diaphragm 2 can be integrally formed by electroforming. Furthermore, a photosensitive resin or the like may be used for these formations.

Further, the diaphragm 2 is formed by forming a three-layer structure of nickel plates in the order of the first layer 2a, the second layer 2b, and the third layer 2c from the pressurized liquid chamber 6 side. The diaphragm 2 is formed by, for example, electroforming. Further, the diaphragm 2 may be formed of, for example, a laminated member of a resin member such as polyimide and a metal plate such as a SUS substrate. Furthermore, the diaphragm 2 may be formed of a resin member or the like.

A plurality of nozzles 4 are formed in the nozzle plate 3 for each pressurized liquid chamber 6. For example, the nozzle plate 3 is a metal such as stainless steel or nickel, a resin such as a polyimide resin film, silicon, or a combination thereof.

Further, the internal shape of the nozzle 4, that is, the inner shape is formed into, for example, a horn shape. The internal shape of the nozzle 4 may be a substantially cylindrical shape, a truncated cone shape, or the like. Further, the hole diameter of the nozzle 4 is about 14 to 35 micrometers in diameter on the outlet side where the droplet is discharged.

A water-repellent film (layer) (3a, see FIG. 6) having been subjected to a water-repellent surface treatment is provided on the nozzle plate 3 and the nozzle surface (the surface in the direction in which the droplets are discharged, that is, the discharge surface). Be done. The water-repellent film is, for example, PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor deposition coating of evaporable fluororesin (for example, fluororesin, etc.), silicon-based resin, or fluororesin solvent. Baking after coating is selected and provided according to the physical properties of the recording liquid. In addition, the water-repellent film stabilizes the droplet shape and flight characteristics of the recording liquid so that high-quality image quality can be obtained.

Then, in the diaphragm 2, the second layer 2b is formed in the central portion of the diaphragm portion (vibration region) 2A which is formed by the first layer 2a and is a deformable region for each pressurized liquid chamber 6. A convex portion 2B having a laminated structure of the third layer 2c is formed. A laminated piezoelectric element 121 constituting a pressure generating means (actuator) is bonded to the convex portion 2B.

Then, the peripheral edge portion of the diaphragm 2 is joined to the frame member 17. The frame member 17 is formed with an ink supply hole 10 which is a supply port for supplying ink to the common liquid chamber 8 from the outside.

The plurality of piezoelectric elements 121 are formed in a comb-teeth shape without being divided by performing half-cut groove processing (slit processing) on one driving element (piezoelectric member, piezoelectric element member) 12. Tooth. Further, the drive element 12 is arranged on the base member 13 along the direction in which the plurality of piezoelectric elements 121 are arranged.

The base member 13 is preferably made of a metal material. When the base member 13 is made of a metal material, heat storage due to self-heating of the drive element 12 can be reduced.

Further, the vibration region (diaphragm) 2A is displaced by the expansion and contraction of the piezoelectric element 121. Then, when the vibration region 2A is displaced, the pressurized liquid chamber 6 contracts or expands. In this way, when the drive signal is applied to the piezoelectric element 121 and charging is performed, the piezoelectric element 121 expands. On the other hand, when the electric charge charged in the piezoelectric element 121 is discharged, the piezoelectric element 121 contracts.

The liquid in the pressurizing liquid chamber 6 may be pressurized by using the displacement in the d33 direction in the piezoelectric direction of the drive element 12 which is a piezoelectric member. Further, the liquid in the pressurizing liquid chamber 6 may be pressurized by using the displacement of the piezoelectric element member 12 in the piezoelectric direction in the so-called d31 direction. Hereinafter, a configuration using displacement in the d33 direction will be described as an example.

FIG. 1B is a cross-sectional view taken along the plane direction of the liquid chamber of the droplet ejection head of FIG. 1A. Here, the piezoelectric member will be described.

A base member 13 that joins and fixes the piezoelectric member (driving element) 12 and constitutes the actuator unit is arranged. In the drive element 12, a plurality of piezoelectric elements 121 and strut members 123 are formed by forming grooves by slit processing that is not divided.

The end face electrode on one end surface of the drive element 12 was divided by dicing by half-cut to become an individual electrode 16, and the end face electrode on the other end surface was not divided due to restrictions due to processing such as notch and was conducted by all piezoelectric elements 121. It becomes the common electrode 15.

The common electrode 15 is connected to the ground (GND) electrode of the FPC cable 11 by providing an electrode layer at the end of the piezoelectric element 121 and turning it around. In this example, the piezoelectric element 121 is a drive piezoelectric element column that applies a drive waveform (absolute voltage) to the individual electrodes 16 and expands and contracts due to a change in the voltage difference between the common electrode 15 and the individual electrodes 16.

Here, the individual electrode 16 functions as a first electrode to which a voltage changing in a waveform is applied, and the common electrode 15 functions as a second electrode to which a common voltage is applied to a plurality of electrodes.

The support column member 123 is a non-driven piezoelectric element column that is not affected by changes in the voltage difference between the electrodes of the common electrode 15 and the individual electrodes 16.

Further, an FPC cable 11 connected to a drive circuit (drive IC) for selectively applying a drive waveform (drive voltage waveform) is connected to an individual electrode 16 connected to the piezoelectric element 121 of the drive element 12.

The driving element 12 alternates between a piezoelectric material 151 made of lead zirconate titanate (PZT) having a thickness of 10 to 50 μm / layer and an internal electrode 152 made of silver / palladium (AgPd) having a thickness of several μm / layer. It is laminated on. The internal electrodes 152 are alternately electrically connected to individual electrodes 16 and common electrodes 15 which are end face electrodes (external electrodes) on the end faces.

The piezoelectric constant of the piezoelectric element 121 is d33, and the pressurizing liquid chamber 6 is contracted and expanded by expansion and contraction due to a change in the voltage difference (relative voltage) between the electrodes 15 and 16 received by the piezoelectric element 121. The piezoelectric element 121 expands when a drive signal is applied and is charged to expand the pressurizing liquid chamber 6, and the piezoelectric element 121 contracts the pressurizing liquid chamber 6 in the opposite direction when the charged charge is discharged. It has become.

In the droplet ejection head configured in this way, for example, by lowering the voltage (absolute voltage) applied to the individual electrodes 16 from the reference voltage Ve (applying a pulse voltage of a drive waveform of 10 to 50 V, etc.), the electrodes 16, The voltage difference between 15 becomes small, and the piezoelectric element 121 contracts. Therefore, the diaphragm 2 descends and the volume of the liquid chamber 6 expands, so that the ink flows into the liquid chamber 6.

After that, the voltage applied to the individual electrodes 16 is increased to increase the voltage difference between the electrodes 16 and 15, the piezoelectric element 121, which is the driving piezoelectric element column, is extended in the stacking direction, and the vibrating plate 2 is deformed in the nozzle 4 direction. The volume of the liquid chamber 6 is contracted. By this operation, the ink in the liquid chamber 6 is pressurized, and ink droplets are ejected (sprayed) from the nozzle 4.

Then, by returning the voltage applied to the individual electrodes 16 to the reference voltage, the diaphragm 2 is restored to the initial position, the liquid chamber 6 expands and a negative pressure is generated. Therefore, at this time, the liquid chamber 8 to the liquid chamber. Ink is filled in 106. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation proceeds to the next droplet ejection operation.

In general, some inkjet heads that use a diaphragm are driven by a pushing method, a pulling method, or a combination of these methods. In the push-and-push method, the diaphragm is pushed toward the pressurizing chamber to reduce the volume of the pressurizing chamber, thereby ejecting ink droplets.

In the drive by the pulling method, the diaphragm is deformed by the force in the outward direction of the liquid chamber, and the displacement of the diaphragm is restored from the expanded state of the liquid chamber to the original volume, thereby causing ink droplets. Is discharged.

As described above, the above-mentioned head driving method is not limited to (pull-pushing), and pulling or pushing may be performed depending on the driving waveform.

A droplet ejection device including a unit for ejecting droplets provided with such a ejection head is, for example, an image forming apparatus. That is, when the image forming apparatus ejects droplets, the ejected droplets are a recording liquid such as ink. Hereinafter, an example of an image forming apparatus will be described. The configuration for ejecting droplets may be a unit having an integral configuration for ejecting droplets, such as a unit for ejecting droplets.

<Hardware configuration example>
FIG. 2 is a block diagram showing a hardware configuration example of the image forming apparatus according to the embodiment of the present invention. For example, the image forming apparatus according to an embodiment of the present invention has a hardware configuration shown in the figure.

The image forming apparatus includes a CPU (Central Processing Unit) 201, a ROM (Read-Only Memory) 202, and a RAM (Random Access Memory) 203. In addition, the image forming apparatus includes NVRAM (Non-Volatile RAM, non-volatile RAM) 204 and ASIC (Application Specific Integrated Circuit) 205.

Further, the image forming apparatus includes a host I / F (interface) 206, a print control device 207, a carriage 30, a motor drive device 210, an AC bias supply device 212, and an I / O (Input / Output) 213.

Furthermore, the image forming apparatus includes an operation panel 214, a temperature sensor 215, a main scanning motor 40, an encoder sensor 43, a sub scanning motor 31, a conveyor belt 21, an encoder sensor 35, and a charging roller 26.

The CPU 201 controls the entire image forming apparatus. That is, the CPU 201 is an arithmetic unit that performs operations for realizing the processing and data processing performed by the control unit 200. Further, the CPU 201 is a control device that controls the illustrated hardware.

ROM 202, RAM 203 and NVRAM 204 are examples of storage devices. Specifically, the ROM 202 stores data such as a program executed by the CPU 201 and fixed data. The RAM 203 also stores data such as image data. Further, since the NVRAM 204 can hold data even when the power of the image forming apparatus is cut off, the NVRAM 204 stores data and the like to be held even when the power of the image forming apparatus is turned off.

The ASIC 205 is an electronic circuit that performs various signal processing on image data, image processing such as sorting, and processing of input / output signals for controlling the entire image forming apparatus.

The host I / F 206 is an interface for transmitting and receiving data to and from the host side.

The print control device 207 transmits data for driving the ejection head (droplet ejection head) 209 and the like. Further, the print control device 207 generates and transmits a drive waveform.

The carriage 30 is realized by a head driver 208, a discharge head 209, and the like. The head driver 208 is a driver IC (Integrated Circuit) or the like for driving the discharge head 209 provided on the carriage 30 side.

Here, the print control device 207 and the carriage 30 are combined to form a unit 300 that ejects droplets. Further, the print control device 207 and the head driver 208 are combined to form a control unit 350 of the unit 300 that ejects droplets. The control of the unit 300 for ejecting droplets will be described later together with FIG.

The motor drive device 210 drives the main scanning motor 40 and the sub-scanning motor 31. The AC bias supply device 212 supplies the AC bias to the charging roller 26.

The encoder sensor 43 outputs a detection signal indicating the position of the main scanning motor 40. Similarly, the encoder sensor 35 outputs a detection signal indicating the position of the sub-scanning motor 31. The temperature sensor 215 measures the ambient temperature of the image forming apparatus and outputs a detection signal.

The I / O 213 is an interface for inputting detection signals from each sensor.

The operation panel 214 is a display device for displaying various information and an input device for inputting operations by the user to the user of the image forming apparatus.

For example, the control unit 200 receives image data and the like from an information processing device such as a PC (Personal Computer), an image reading device such as an image scanner, and an imaging device such as a digital camera by the host I / F 206. The image data or the like is received via a cable, a network, or the like. Next, the CPU 201 of the control unit 200 reads out and analyzes the image data and the like stored in the reception buffer of the host I / F 206.

Then, the control unit 200 performs processing such as image processing and data rearrangement by the ASIC 205. Subsequently, the image data processed by the ASIC 205 is transmitted to the head driver 208 by the print control device 207. It is assumed that the dot pattern data for image formation is generated by the printer driver on the host side.

Further, the print control device 207 converts the image data into serial data and transmits the image data to the head driver 208. Further, the print control device 207 transmits signals such as a clock signal, a latch signal, and a drop control signal (mask signal) used for transmitting image data to the head driver 208.

Furthermore, the print control device 207 includes a D / A converter and the like that D / A (digital-analog) convert data indicating a drive signal pattern stored in the ROM 202 or the like. Further, the print control device 207 has a common drive waveform generation unit 301 that generates a drive signal by a voltage amplifier that amplifies the voltage of the signal, a current amplifier that amplifies the current of the signal, and the like.

Further, the print control device 207 has a selection unit (transmission unit) 302 that instructs the selection of the drive waveform to be transmitted to the head driver 208. Subsequently, one or more drive waveform pulses, that is, drive signals (common drive waveforms) are transmitted to the head driver 208. The details of the print control device 207 will be described later.

Image data is serially transmitted to the head driver 208. Further, the image data is transmitted to the head driver 208 as data for one line of the discharge head 209. Based on the data for one line, the head driver 208 applies a drive signal to be a drive waveform to the discharge head 209 (individual electrode 16). When the drive signal is applied, the drive element (for example, the piezoelectric member 12 including the piezoelectric element 121) included in the discharge head 209 generates energy for discharging the droplet. In this way, the discharge head 209 is driven based on the image data.

Further, the image forming apparatus can be set to any size of, for example, a large drop (large dot), a medium drop (medium dot), a small drop (small dot), or the like by selecting the drive waveform pulse constituting the drive waveform. The dots can be separated so as to be.

Further, the CPU 201 samples the detection signal transmitted from the encoder sensor 43 constituting the linear encoder or the like to obtain a speed detection value, a position detection value, or the like. Next, the CPU 201 controls the main scanning motor 40 based on the speed target value and the position target position obtained from the speed and the position profile and the like stored in advance, and the speed detection value and the position detection value. That is, the control value is calculated. Subsequently, the CPU 201 drives the main scanning motor 40 via the motor drive device 210 based on the control value.

Similarly, the CPU 201 samples the detection signal transmitted from the encoder sensor 35 constituting the rotary encoder or the like to obtain a speed detection value, a position detection value, or the like. Next, the drive output value for controlling the sub-scanning motor 31 based on the speed target value and the position target position obtained from the speed and the position profile and the like stored in advance and the speed detection value and the position detection value, that is, Calculate the control value. Subsequently, the CPU 201 drives the sub-scanning motor 31 via the motor drive device 210 based on the control value.

<Arrangement of nozzles>
FIG. 3 is an external view showing an example of a discharge head included in the image forming apparatus according to the embodiment of the present invention. The image forming apparatus according to an embodiment of the present invention has, for example, a discharge head 209 as shown in the figure. Note that FIG. 3A is a plan view (bottom view) of the discharge head 209 as viewed from the so-called nozzle direction. On the other hand, FIG. 3B is a side view of the discharge head 209 as viewed from the side surface.

Hereinafter, the direction in which the nozzles 4 of the discharge head 209 are arranged (corresponding to the left-right direction in the figure) is defined as the x-axis. Further, the direction orthogonal to the x-axis is defined as the y-axis. The vertical direction is the z-axis.

In the illustrated example, there are a plurality of nozzles 4 and they are arranged in the x-axis direction. In this example, the nozzle group 102 is composed of a plurality of nozzles 4. Specifically, as shown in the drawing, a plurality of nozzles 4 are arranged so as to be in the first row 102a and the second row 102b, and the nozzle group 102 is formed. As shown in the figure, the second row 102b is a position where there is no nozzle 4 constituting the first row 102a, that is, a position for interpolating between the nozzles 4 constituting the first row 102a. It is installed as.

Further, the discharge head 209 has a flow path member 1 (sometimes referred to as a “droplet substrate”) that forms a flow path through which droplets flow. Further, the configuration shown in the figure is an example in which the diaphragm 2 is joined to the lower surface of the flow path member 1. On the other hand, in this example, the nozzle plate 3 is joined to the upper surface of the flow path member 1 with an adhesive or the like. Furthermore, the frame member 17 is joined to the diaphragm 2 with an adhesive or the like.

The flow path member 1, the diaphragm 2, the nozzle plate 3, the frame member 17, and the like form a flow path through which the liquid to be droplets discharged from the nozzle 4 flows, a liquid chamber in which the liquid is stored, and the like.

Further, a damper member 20 is used on at least one surface of the wall surface of the liquid chamber to be formed. The damper member 20 has a lower rigidity than the wall surface of the frame member 17. Further, the damper member 20 is not limited to one layer, and may be two or more layers. In addition, the damper member 20 may be made of a material different from that of the diaphragm 2. For example, the damper member 20 is a nickel (Ni) metal or the like. That is, the damper member 20 is preferably made of a material having low gas permeability such as nickel metal. Further, the damper member 20 may be formed of a resin film or the like.

<Structure example of the first embodiment>
FIG. 4 is a block diagram showing a configuration example of the print control device 207 and the head driver 208 according to the first embodiment of the present invention. FIG. 5 is a diagram illustrating a drive waveform according to an embodiment of the present invention.

As shown in FIG. 4, the print control device 207 has a common drive waveform generation unit 301 and a transmission unit 302.

On the other hand, the head driver 208 connected to the print control device 207 is provided with drive waveform generation units 310a to 310x capable of applying drive waveforms to individual nozzles.

The common drive waveform generation unit 301 generates and transmits a common drive waveform including a plurality of ejection pulses contributing to the formation of a plurality of drop sizes in a time series within one cycle in printing.

The transmission unit 302 transmits a drop control signal (a large drop MN signal, a medium drop MN signal, and a small applicable MN signal shown in FIG. 5) indicating the size of the drop to the head driver 208. Further, the transmission unit 302 transmits droplet data such as an image data signal, a latch signal, and a clock signal to the head driver 208.

Each drive waveform generation unit 310 in the head driver 208 in the present embodiment has a discharge pulse selection unit 311, an intermediate voltage correction value storage area 312, a drive voltage correction value storage area 313, and a selection waveform data correction unit 314.

The discharge pulse selection unit (data selection unit) 311 selects the selection waveform data from the common drive waveform data transmitted from the drive control unit according to the droplet data (FIGS. 5 (c), (d), e) See waveform). The discharge pulse selection unit 311 is composed of, for example, a shift register, a latch circuit, a decoder, a level shifter, an analog switch, and the like.

The intermediate voltage correction value storage area (first storage area) 312 stores the correction value (intermediate voltage correction value) of the intermediate voltage Ve in association with the characteristics of the corresponding nozzle and the drive waveform.

The drive voltage correction value storage area (second storage area) 313 stores the correction value of the drive voltage (peak voltage of the discharge pulse) in association with the corresponding nozzle characteristics and the drive waveform.

For example, the intermediate voltage correction value storage area 312 and the drive voltage correction value storage area 313 are formed in the same storage means 315 such as NVRAM. Alternatively, the storage areas 312 and 313 may be provided in separate storage means.

In the drive waveform generation unit 310, the selection waveform data correction unit 314 is connected to the discharge pulse selection unit 311, the intermediate voltage correction value storage area 312, and the drive voltage correction value storage area 313.

The selection waveform data correction unit 314 displays the waveform data selected by the discharge pulse selection unit.
Correction is performed according to the intermediate voltage correction value and the drive voltage correction value read out according to the drive frequency (see the arrows in FIGS. 5 (c), (d), and (e)). The selected waveform data reflecting the correction value becomes the drive waveform given (applied) to the individual electrodes 16 connected to the drive element 12.

Here, the drive waveform is a voltage that changes into a waveform. By applying a drive waveform, which is an absolute voltage (potential difference between the applied voltage and ground) that changes into a waveform, to a plurality of individual electrodes 16, the potential difference (relative voltage) between the individual electrodes 16 and the common electrode 15 becomes a waveform. Changes to. The drive element 12 expands and contracts due to the change in the potential difference (relative voltage) between the electrodes, and the plurality of drive elements 12 change the volumes of the corresponding liquid chambers.

Here, an example (absolute voltage = relative voltage) in which the common electrode 15 is connected to the ground voltage (0 V) is shown, but the common electrode may be connected to a bias voltage other than the ground voltage.

Further, in the above embodiment, the common electrode 15 and the individual electrode 16 are provided on both side surface portions of the piezoelectric element 121, but the electrodes may be located at different locations such as the upper surface portion and the lower surface portion. .. Further, although an example of a pair of common electrodes and individual electrodes is shown for one piezoelectric element, a plurality of paired common electrodes and individual electrodes may be provided in order to change the piezoelectric element.

The drive voltage, intermediate voltage, and the like described below mean the potential difference between the individual electrode 16 and the common electrode 15.

With such a configuration, it is possible to correct the intermediate voltage of the drive waveform (that is, the potential difference between the individual electrodes and the common electrode) applied to the individual individual electrodes 16 and to correct the energy given to the liquid chamber 6. .. Here, the intermediate voltage means a voltage in front of the driving portion where the potential difference between the individual electrodes 16 and the common electrodes 15 becomes a predetermined voltage difference when applied to the individual electrodes 16.

By this correction, it is possible to correct the variation in the characteristics of the liquid chamber, make the individual liquid chamber volumes (the part where the liquid can exist in the liquid chamber) evenly approach, and suppress the variation in the frequency fluctuation amount of the discharged droplet volume between the nozzles. It will be possible.

Next, the behavior around the head and the nozzle when a drive pulse is applied will be described. FIG. 6 shows an explanatory diagram showing a state of the meniscus and the drive pulse in the nozzle when the drive pulse waveform is applied.

On the right side of FIG. 6, the waveform portion of the drive pulse with respect to the state of the meniscus of the nozzle 4 on the left portion is shown by a thick line. In the present specification, the meniscus means the state of the surface of the liquid (ink) near the nozzle.

In the embodiment of the present invention, when the drive voltage waveform (overall voltage) is applied to the individual electrodes 16 connected to the drive element 12, the applied absolute voltage is once held at the intermediate voltage Vg. An intermediate voltage of about a dozen V is maintained for the discharge operation, particularly for pulling. At this time, the volume of the liquid chamber is reduced by the driving element expanded by applying the intermediate voltage.

At the reference voltage Vg, as shown in FIG. 5A, the meniscus overflows (swells due to surface tension).

From there, as shown in FIG. 5B, the meniscus is drawn into the nozzle 4 by expanding the individual liquid chamber 6 with the first pull-in waveform element a1. At this time, a part of the liquid La remains in the portion of the deteriorated water repellent film 3a.

However, as shown in FIG. 6C, the meniscus swings back (amplitude) during the intermediate voltage (Vg), which is the voltage holding portion (period) b1 from the first lead-in waveform element Pa to the first discharge pulse. Is generated, and the liquid L in the nozzle 4 and the remaining liquid La are united.

Therefore, as shown in FIG. 6D, by expanding the individual liquid chamber 6 by the lead-in waveform element a2 of the first discharge pulse, the remaining liquid La is also drawn into the nozzle 4, and the meniscus is centered on the nozzle. On the other hand, it has a symmetrical shape. Here, the waveform element that draws in the liquid L in the nozzle 4 together with the remaining liquid La is defined as the peak voltage (driving voltage) b. The drive voltage b is a voltage at which the potential difference between the individual electrode 16 and the common electrode 15 is the smallest.

From this state, as shown in FIG. 6E, the meniscus is extruded and the droplets are ejected by contracting the individual liquid chamber 6 by the contraction element c of the ejection pulse. At this time, since the meniscus has a symmetrical shape with respect to the center of the nozzle, injection bending does not occur. Therefore, the injection bending can be suppressed by performing the two-step drawing of the meniscus (two-step expansion of the individual liquid chamber).

In this way, the droplets are ejected from the nozzle 4 by the two-step pulling of the meniscus.

The drive waveform (voltage that becomes the waveform) applied in the embodiment of the present invention is not limited to the two-stage waveform, and may be a waveform excluding the steps of FIGS. 6A and 6B. In this case, since the voltage is the same before and after the waveform changes to a trapezoid, the voltage before and after the change is set as the intermediate voltage. Thus, in the case of one-step pulling, the intermediate voltage means the reference voltage Vg, which is the period during which a predetermined potential difference between the two electrodes is held in front of the drive portion.

FIG. 7 shows an explanatory diagram of an example of variation in droplet volume and an example of correction thereof. (A) shows the discharge volume variation due to the drive frequency variation between the plurality of nozzles. (B) shows a discharge example in which the variation of (a) is corrected.

Here, in general, there are manufacturing variations in the shape between the plurality of nozzles. For example, in the assembly process, the driving element is joined to the liquid chamber parts via a diaphragm, the liquid chamber is sealed, and the liquid chamber volume (volume), height, width, and the like are determined.

Specifically, each of the plurality of nozzles 4 of the discharge head 209 has the characteristics of Helmholtz natural vibration mainly corresponding to the shape of the liquid chamber 6 and the corresponding refill period mainly to the shape of the nozzle and the fluid resistance part. This characteristic is slightly different between the plurality of nozzles due to manufacturing variations.

In the present specification, the Helmholtz natural vibration (natural vibration frequency) is determined by the opening of the nozzle 4, the shape of the pressure chamber (liquid chamber) 6, and the ink supply port formed by the restrictor (communication portion) 9. It is dominated by volume change per pressure, degree of softness) and inertia.

Further, in the present specification, the refill means the degree of ink inflow (pull-in) from the common liquid chamber 8 to the individual liquid chamber (pressurized liquid chamber) 6, and changes according to the resistance value of the fluid resistance portion 7. It is a value to be used. If there are many refills, the inertia causes the liquid meniscus from the nozzle 4 to swell, and the liquid overflows.

Due to the difference in the natural vibration cycle of the liquid chamber 6 and the refill cycle of the nozzle 4, even if the same drive frequency is applied, the volume of the droplets ejected as shown in (a) varies.

Therefore, in the present invention, the correction described later is performed between a plurality of nozzles based on the difference in the characteristics of the liquid chamber and the nozzle, such as the natural vibration frequency peculiar to the nozzle (volume of the nozzle + liquid chamber). Make the volume of droplets ejected after correction uniform.

<Control flow of the first embodiment>
FIG. 8 shows a flowchart showing a control flow according to the first embodiment of the present invention.

First, in S1, the CPU 201 (see FIG. 2) acquires the paper transfer speed information via the host I / F 206 or the operation panel 214.

In S2, the CPU 201 acquires image data via the host I / F 206.

In S3, the CPU 201 sets the head movement speed according to the paper speed information and the image data. For example, in the ROM 202 or the like in the control unit 200 shown in FIG. 2, the head moving speed is set in advance according to the image data, and the speed is read out.

In S4, the drive frequency applied by the transmission unit 302 of the print control device 207 is determined according to the head movement speed.

In S5, the size of the droplet (drop size) is set in the transmission unit 302 according to the image data. Then, a drop control signal (MN signal for large drops, MN signal for medium drops, MN signal for small drops) is transmitted to the head driver 208 according to the droplet size.

In S6, the discharge pulse selection unit 311 selects the discharge pulse from the common drive waveform according to the size of the droplet in the drive waveform generation units 310 provided in the head driver 208 on the carriage side.

In S7, the selected waveform data correction unit 314 reads out the correlation table of the liquid chamber size (characteristic), the intermediate voltage, and the peak voltage from the storage areas 312 and 313.

In S8, the selected waveform data correction unit 314 corrects the intermediate voltage by the correlation table according to the determined drive frequency or the high frequency drive frequency.

In S9, the peak voltage of the discharge pulse of the drop size selected according to the drop size is corrected by the correlation table according to the drive frequency used in S8.

Liquid due to the potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 generated by applying the intermediate voltage (absolute voltage) corrected in S8 in S10 to the individual electrode 16 connected to the drive element 12. The volume of the chamber 6 is adjusted, and the position of the meniscus in the nozzle 4 is adjusted.

The potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 generated by applying the discharge pulse (= drive waveform) corrected in S9 in S11 to the individual electrode 16 connected to the piezoelectric member (drive element) 12. ) Adjusts the volume of the liquid chamber 6 and ejects droplets from the nozzle 4.

As described above, the control operation is terminated.

<Applied voltage, head internal volume, and meniscus at the nozzle>
First, FIG. 9 shows a schematic diagram of the liquid chamber when no applied voltage is applied. The case where the applied voltage is not applied means that the potential difference between the individual electrode 16 and the common electrode 15 is 0. For example, both the individual electrode 16 and the common electrode 15 have a ground voltage.

In this state, the liquid chamber 6 is not pressed by the driving element 12, and the resistance value of the fluid resistance portion 7 is small. Therefore, as shown in the figure, the meniscus (liquid level) of the nozzle is inside the nozzle and is slightly recessed due to surface tension.

FIG. 10 shows a schematic view of the liquid chamber and the periphery of the nozzle when an intermediate voltage is applied to the liquid chamber having ideal characteristics. More specifically, the relationship between the intermediate voltage and the position of the meniscus when the frequency characteristic of the discharged droplet volume is equal to the ideal characteristic is shown.

In FIG. 10, (a) is a schematic diagram of a liquid chamber when a standard value intermediate voltage is applied, (b) is a schematic diagram of a liquid chamber when a high intermediate voltage is applied, and (c) is a high intermediate voltage. The schematic diagram of the liquid chamber in the case of the case is shown.

As shown in FIG. 10, when the applied intermediate voltage is different for the liquid having the same characteristics, the amount of pushing into the pressure chamber is different and the fluid resistance is different, so that the position of the meniscus at the nozzle is different.

The details of correcting the intermediate voltage once held by utilizing this property according to the characteristics of each nozzle and performing the correction control so as to make the amount of decrease in the liquid chamber volume before discharge uniform will be described below.

<When the volume fluctuates greatly>
FIG. 11 shows a liquid when an intermediate voltage and a corrected intermediate voltage are applied to a liquid chamber in which the amount of fluctuation of the liquid in the liquid chamber is large (for example, the volume of the liquid chamber is large) due to the characteristics of the liquid chamber and the nozzle. The schematic diagram around the chamber and the nozzle is shown.

In FIG. 11, FIG. 11A shows a schematic diagram of the liquid chamber before the correction is performed, a drive waveform, and frequency fluctuation characteristics of the discharged droplet volume, and FIG. 11B shows a schematic diagram of the liquid chamber and the drive waveform after the correction of the intermediate voltage. , The frequency fluctuation characteristic of the discharged droplet volume is shown, and (c) shows the driving waveform after the correction of the driving voltage and the frequency fluctuation characteristic of the discharged droplet volume.

As shown in FIG. 11A, with respect to the drive element 12 corresponding to the liquid chamber 6 in which the amount of fluctuation of the liquid in the liquid chamber is large due to the characteristics of the liquid chamber and the nozzle, the reference value shown in FIG. When the same voltage (intermediate voltage) is applied, the liquid L contained in the liquid L tends to swell outward from the nozzle 4.

As described above, the magnitude of the fluctuation amount of the liquid in the liquid chamber is the natural vibration frequency due to the volume of the liquid chamber 6, the vertical length, and the horizontal length, the volume of the nozzle 4, and the vertical length. It is defined by the dimensions at the time of manufacture due to the difference in the refill cycle due to the difference in the length and the horizontal length.

Therefore, it is preferable to apply the same voltage in advance after manufacturing to measure and store the relationship between the meniscus positions of the liquid L of the nozzle 4.

When the frequency characteristic of the ejected droplet volume fluctuates more than the ideal characteristic, the fact that the ejected droplet volume is particularly large at high frequencies means that the meniscus on the nozzle surface is excessively raised due to the effect of refilling. It means that it is.

In order to approach the ideal characteristics, it is necessary to suppress excessive swelling of the meniscus on the nozzle surface. For this purpose, the resistance value of the fluid resistance portion 7 of the liquid chamber 6 may be increased by increasing the amount of pushing the drive element 12 into the liquid chamber 6, and refilling may be suppressed.

Further, if the intermediate voltage is simply increased, the pulse height (amplitude) used for the ejection operation also increases, and the volume of the ejected droplet during low frequency driving becomes large. In order to prevent this, as shown in (c), the pulse height is also adjusted to correct the ejected droplet volume during low frequency driving.

<When the volume fluctuates small>
FIG. 12 shows a liquid when an intermediate voltage and a corrected intermediate voltage are applied to a liquid chamber in which the amount of fluctuation of the liquid in the liquid chamber is small (for example, the volume of the liquid chamber is small) due to the characteristics of the liquid chamber and the nozzle. It is a schematic diagram around a chamber and a nozzle.

In addition, in FIGS. 12 and 13, the drive waveform diagram shown in the center shows the potential difference (relative potential) between the individual electrode 16 and the common electrode 15 which directly affects the expansion and contraction of the drive element 12 and the fluctuation of the volume of the liquid chamber 6. ) Shall be indicated. In addition, in FIGS. 12 and 13, for simplification of the description, it is assumed that the common electrode 15 is grounded (0V) (relative voltage = absolute voltage).

In FIG. 12, FIG. 12A shows a schematic diagram of the liquid chamber before the correction is performed, a drive waveform, and frequency fluctuation characteristics of the discharged droplet volume, and FIG. 12B shows a schematic diagram of the liquid chamber and the drive waveform after the correction of the intermediate voltage. , The frequency fluctuation characteristic of the discharged droplet volume is shown, and (c) shows the driving waveform after the correction of the driving voltage and the frequency fluctuation characteristic of the discharged droplet volume.

As shown in FIG. 12A, with respect to the drive element 12 corresponding to the liquid chamber 6 in which the amount of fluctuation of the liquid in the liquid chamber is small due to the characteristics of the liquid chamber and the nozzle, the reference value shown in FIG. When the same voltage (intermediate voltage) is applied, the contained liquid L tends to be drawn inward of the nozzle 4.

When the frequency characteristic of the ejected droplet volume fluctuates smaller than the ideal characteristic, the fact that the ejected droplet volume at a high frequency is small means that the meniscus of the nozzle 4 is excessively drawn in due to the influence of the refill. Is to be done.

It is necessary to suppress excessive refill drawing in order to approach the ideal characteristics. Therefore, by reducing the amount of the driving element 12 pushed into the liquid chamber 6, the resistance value of the fluid resistance portion 7 of the liquid chamber may be reduced to promote refilling.

Further, if the intermediate voltage is simply lowered as in (b), the pulse height (amplitude) used for the ejection operation also becomes small, and the ejected droplet volume at the time of low frequency driving becomes small. In order to prevent this, as shown in (c), the pulse height is also adjusted to correct the ejected droplet volume during low frequency driving.

As shown in FIGS. 11 and 12, by correcting the intermediate voltage according to the characteristics of the individual liquid chambers and nozzles, the state of the meniscus with respect to the nozzle before applying the drive waveform can be made uniform.

図１１、図１２の傾向を表１に示す。このような製造バラツキに起因する吐出液滴体積のばらつきを補正するために、表２のように補正値を記憶しておくと好適である。

Table 1 shows the trends of FIGS. 11 and 12. In order to correct the variation in the discharged droplet volume due to such manufacturing variation, it is preferable to store the correction value as shown in Table 2.

なお、表２では、模式的に補正の大、小等の傾向のみを示したが、実際には、段階的に変化する補正値や、補正倍率等を記憶しておくとより好ましい。このような製造ばらつきを、図４に示した、中間電圧補正値記憶領域３１２及び駆動電圧補正値記憶領域３１３に保存させておき、図８に示すように制御動作を実行する際に読み出して、補正に利用される。

Although Table 2 schematically shows only the tendency of the correction to be large or small, it is more preferable to store the correction value that changes stepwise, the correction magnification, and the like. Such manufacturing variations are stored in the intermediate voltage correction value storage area 312 and the drive voltage correction value storage area 313 shown in FIG. 4, and are read out when the control operation is executed as shown in FIG. Used for correction.

Therefore, it is possible to suppress the variation in discharge volume between a plurality of nozzles due to the characteristics (variation in characteristics) of the individual liquid chambers and nozzles.

<Deviation due to frequency>
FIG. 13 shows a discharge droplet volume histogram before and after the correction. In FIG. 13, the standard deviation of the discharge droplet volume distribution among a plurality of nozzles of the discharge droplet volume discharged from the nozzle 4 when the piezoelectric element 121 of the drive element 12 is driven at a low frequency is driven at a low frequency. It shows the standard deviation of the discharge droplet volume distribution among a plurality of nozzles of the discharge droplet volume discharged from the nozzle 4 when the piezoelectric element 121 is driven at a high frequency.

As shown in FIG. 13, the variation in the volume of the ejected droplets during high-frequency driving in which the droplets are ejected at high frequency is easily detected as an abnormal image, particularly uneven density. Therefore, the variation in the volume of the ejected droplets during high-frequency driving is prioritized and corrected.

Specifically, the standard deviation of the discharge droplet volume distribution between a plurality of nozzles during low-frequency driving is corrected to be smaller than the standard deviation of the ejection droplet volume distribution between multiple nozzles during high-frequency drive. To do.

In the above embodiment, an example of correcting the pulse according to the characteristics peculiar to the nozzle after selecting the discharge pulse corresponding to the drop size from the common drive waveform has been described, but if the correction is performed for each nozzle, the discharge pulse is used. The common drive waveform before selection may be corrected.
The common drive waveform corrected for each nozzle includes the same intermediate voltage as described above and the peak voltage of the discharge pulse.

<Structure example of the second embodiment>
FIG. 14 is a block diagram showing a configuration example of the print control device 207 and the head driver 208-1 according to the second embodiment of the present invention.

As shown in the figure, the print control device 207 has a common drive waveform generation unit 301 and a transmission unit 302. On the other hand, the head driver 208-1 connected to the print control device 207 is provided with drive waveform generation units 320a to 320x capable of applying drive waveforms to individual nozzles.

The common drive waveform generation unit 301 generates and transmits a common drive waveform including a plurality of ejection pulses contributing to the formation of a plurality of drop sizes in a time series within one cycle in printing.

The transmission unit 302 transmits droplet data such as a droplet control signal, an image data signal, a latch signal, and a clock signal that indicate the size of the droplet to the head driver 208-1.

Each drive waveform generation unit 320 in the head driver 208-1 in the present embodiment has an intermediate voltage correction value storage area 321, a drive voltage correction value storage area 322, a common drive waveform correction unit 323, and a drive waveform selection unit 324. ..

The intermediate voltage correction value storage area (first storage area) 321 stores the intermediate voltage correction value in association with the characteristics of the corresponding nozzles and the drive waveform.

The drive voltage correction value storage area (second storage area) 322 stores the correction value of the drive voltage (peak voltage of the discharge pulse) in association with the corresponding nozzle characteristics and the drive waveform.

For example, the intermediate voltage correction value storage area 321 and the drive voltage correction value storage area 322 are formed in the same storage means 325 such as NVRAM. Alternatively, the storage areas 321 and 322 may be provided in separate storage means.

The common drive waveform correction unit 323 corrects the intermediate voltage and the drive voltage (absolute voltage) of the common drive waveform according to the input intermediate voltage correction value and drive voltage correction value.

The drive waveform selection unit (waveform selection) 324 selects a selection waveform corrected for each nozzle from the common drive waveform data corrected for each nozzle transmitted from the common drive waveform correction unit 323 according to the droplet data. To do. The drive waveform selection unit 324 is composed of, for example, a shift register, a latch circuit, a decoder, a level shifter, an analog switch, and the like.

In the drive waveform generation unit 320, the common drive waveform correction unit 323 reflects the correction value, and the selection waveform selected by the drive waveform selection unit 324 is connected to the respective drive elements 12-a to 12x. It becomes a drive waveform applied to ~ 16-x.

With such a configuration, it is possible to correct the intermediate voltage of the drive waveform applied to each liquid chamber. Therefore, it is possible to correct the variation in characteristics, bring the individual liquid chamber volumes close to each other uniformly, and suppress the variation in the frequency fluctuation amount of the discharged droplet volume between the nozzles.

<Control flow of the second embodiment>
FIG. 15 shows a flowchart showing the flow of control according to the second embodiment.

First, in S21, the CPU 201 acquires the paper transfer speed information via the host I / F 206 or the operation panel 214.

In S22, the CPU 201 acquires image data via the host I / F 206.

In S23, the CPU 201 (FIG. 2) sets the head moving speed according to the paper speed information and the image data.

In S24, the drive frequency applied by the transmission unit 302 of the print control device 207 is determined according to the head movement speed.

In S25, the transmission unit 302 sets the size of the droplet according to the image data. Then, a drop control signal (MN signal for large drops, MN signal for medium drops, MN signal for small drops) is transmitted to the head driver 208-1 according to the droplet size.

In S26, the common drive waveform correction unit 323 reads out the correlation table of the liquid chamber dimensions (characteristics), the intermediate voltage, and the peak voltage in the drive waveform generation units 320 provided in the head drivers 208-1 on the carriage side.

In S27, the common drive waveform correction unit 323 corrects the intermediate voltage and the peak voltage of the common drive waveform according to the determined drive frequency or the high frequency drive frequency by the correlation table.

In S28, the selection unit 324 selects a discharge pulse corrected for each nozzle from the corrected common drive waveform according to the size of the droplet.

In S29, the intermediate voltage (absolute voltage) corrected in S27 is applied to the individual electrode 16 connected to the piezoelectric element 121, and the potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 causes the liquid chamber 6 to have an intermediate voltage. Adjust the volume and adjust the position of the meniscus in the nozzle 4.

In S31, the discharge pulse (= drive waveform, absolute voltage) corrected in S27 and selected in S28 is applied to the individual electrode 16 connected to the piezoelectric element 121, and the potential difference between the individual electrode 16 and the common electrode 15 ( The volume of the liquid chamber 6 is adjusted by the relative voltage), and the droplets are ejected from the nozzle 4.

<Overall configuration example>
FIG. 16 is a schematic view showing an example of the overall configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 17 is a schematic view showing an example of a mechanical portion of the image forming apparatus according to the embodiment of the present invention. The inkjet printer 500, which is an example of the image forming apparatus illustrated in FIG. 16, is a so-called serial type.

As shown in FIG. 17, the inkjet printer has side plates 221A and side plates 221B on the left and right sides. A guide lot 231 and a guide lot 232 are installed on the side plates 221A and 221B. Along the guide lot 231 and the guide lot 232, the carriage 30 is moved by the main scanning motor in the y-axis direction (hereinafter referred to as “carriage main scanning direction”) via the timing belt.

The carriage 30 ejects droplets of each color such as yellow (Y), cyan (C), magenta (M), and black (K). Further, the carriage 30 may be simply referred to as a "recording head 234" when a plurality of recording heads 234a and a recording head 234b having a discharge head 209 (FIG. 2) (hereinafter, the recording head 234a and the recording head 234b are not distinguished). There is.). As shown in the figure, the carriage 30 is installed so that a plurality of nozzles are arranged in a direction orthogonal to the carriage main scanning direction (hereinafter, may be referred to as a “sub-scanning direction”).

In the configuration illustrated in FIG. 17, each recording head 234 has two nozzle rows. For example, the recording head 234a has, on one side, a row of nozzles for ejecting black (K) droplets. On the other hand, the recording head 234a has a nozzle row for ejecting droplets of cyanide (C). Similarly, the recording head 234b has, on one side, a row of nozzles that eject magenta (M) droplets. The recording head 234b, on the other hand, has a nozzle row for ejecting yellow (Y) droplets.

Further, the carriage 30 simply supplies the head tank 235a and the head tank 235b that supply the ink liquids of each color to the nozzle row of the recording head 234 (hereinafter, when the head tank 235a and the head tank 235b are not distinguished). It may be referred to as "head tank 235"). Supply tubes 236 of each color are connected to the head tank 235. Ink liquid is supplied to the head tank 235 from the cartridges 210k, 210c, 210m and 210y of each color via the supply tube 236.

On the other hand, as shown in FIG. 16, the inkjet printer 500 has a paper feed tray 250. The paper feed tray 250 has a paper mounting portion 241 such as a pressure plate. Further, the paper S, which is an example of the recording medium, is placed on the paper mounting unit 241. In this way, the paper feed tray 250 becomes a paper feed unit that supplies the paper S.

Then, the paper S is separated from the paper mounting unit 241 one by one and supplied. For example, as shown in the figure, the inkjet printer 500 has a paper feed roller 243 such as a half-moon roller. A separation pad 244 is provided at a position facing the paper feed roller 243. The separation pad 244 is made of a material or the like having a large friction coefficient.

In order to convey the paper S from the paper feed unit to the lower side of the recording head 234, a guide member 245 or the like for guiding the paper S is provided. Similarly, in order to transport the paper S to the lower side of the recording head 234, a counter roller 246, a transport guide member 247, a pressing member 248 having a tip pressure roller 249, and the like are provided.

Further, since the paper S to be transported is electrostatically attracted and transported to a position facing the recording head 234, a transport belt (transport means) 251 or the like is provided. The transport belt 251 is a so-called endless belt or the like. The transport belt 251 is bridged between the transport roller 252 and the tension roller 253. As a result, the transport belt 251 orbits in the belt transport direction (sub-scanning direction). A charging roller 256 is provided for the transport belt 251. The charging roller 256 charges the surface of the transport belt 251. As shown, the charging roller 256 is provided so as to come into contact with the surface of the transport belt 251. Further, the charging roller 256 rotates according to the rotation of the transport belt 251.

When the transfer roller 252 is rotated by the sub-scanning motor, the transfer belt 251 rotates according to the rotation of the transfer roller 252. Therefore, the transport belt 251 orbits in the belt transport direction by the sub-scanning motor.

Next, an image is formed on the paper S by the recording head 234 or the like. After the image is formed by the recording head 234 or the like, the paper S is discharged. The paper ejection unit for ejecting paper is realized by a separation claw 261 for separating the paper S from the transport belt 251, a paper ejection roller 262, a paper ejection roller 263, a paper ejection tray 255, and the like.

The inkjet printer 500 may have a double-sided unit 271 or the like on the back surface or the like. The double-sided unit 271 is a detachable unit or the like. The double-sided unit 271 reverses the paper S sent from the transport belt 251 and feeds the paper S between the counter roller 246 and the transport belt 251 again. The configuration shown in the figure is an example in which the upper surface of the double-sided unit 271 is a manual feed tray 272.

Returning to FIG. 17, the maintenance / recovery mechanism 281 is installed on one side (right side in the drawing) of the range scanned by the carriage 30. The maintenance / recovery mechanism 281 is a mechanism for maintaining and recovering the state of each nozzle of the recording head 234. It is assumed that no image is formed on the recording medium at the position where the maintenance / recovery mechanism 281 is installed. Hereinafter, the area in which the image is not formed on the recording medium is referred to as a “non-printing area”.

The maintenance / recovery mechanism 281 is provided with a cap member (hereinafter referred to as “cap”) 282a and a cap member 282b (hereinafter, when the cap 282a and the cap 282b are not distinguished, they may be simply referred to as “cap 282”). Be done. The cap 282 is used to cap each nozzle surface of the recording head 234.

The maintenance / recovery mechanism 281 is provided with a wiper blade 283. The wiper blade 283 is a blade member for wiping each nozzle surface. Further, the maintenance / recovery mechanism 281 is provided with an empty discharge receiver 284. Since the air discharge receiver 284 discharges the thickened recording liquid, it receives droplets discharged by so-called empty discharge, which discharges droplets not used for image formation.

Of the non-printed area, the other side on which the maintenance / recovery mechanism 281 is installed is provided with an empty discharge receiver 288. Further, the empty discharge receiver 288 is provided with an opening 289.

In the image forming apparatus as described above, as shown in FIG. 16, the paper S is separated and fed one by one from the paper feed tray 250. Next, the fed paper S is fed between the counter roller 246 and the transport belt 251 by the guide member 245. Subsequently, the paper S is guided by the transport guide member 247, and the paper S is pressed against the transport belt 251 by the tip pressurizing roller 249.

At this time, positive output and negative output are alternately applied to the charging roller 256 so as to repeat. That is, alternating voltages are applied to the charging roller 256. By this application, the transport belt 251 is alternately charged with alternating charging voltage patterns, that is, pluses and minuses in a predetermined width in a strip shape in the sub-scanning direction. In this way, when the paper S is transported onto the transport belt 251 in which plus and minus are alternately charged in a strip shape with a predetermined width, the paper S is attracted to the transport belt 251. Further, the paper S is conveyed in the sub-scanning direction by the conveying belt 251.

The carriage 30 (FIG. 2) moves relative to the conveyed paper S. Further, the carriage 30 drives the recording head 234 based on the image signal. As a result, droplets are ejected onto the paper S, and an image for one line is formed. Next, the inkjet printer 500 conveys a predetermined amount of paper S. Similarly, droplets are ejected onto the paper S to form an image for one line. When the recording end signal or the signal indicating that the rear end of the paper S has reached the recording area is received, the inkjet printer 500 finishes image formation and discharges the paper S to the paper ejection tray 255 or the like.

<Full-line image forming device>
Further, the image forming apparatus may be an apparatus having an overall configuration as shown in FIG.

FIG. 18 is a schematic view showing an example of another overall configuration of the image forming apparatus according to the embodiment of the present invention. The inkjet printer 501, which is an example of the image forming apparatus illustrated in FIG. 18, is a so-called full-line head. The inkjet printer 501 includes an image forming unit 601 and a transport mechanism 604 for transporting paper. Further, the inkjet printer 501 has a paper feed tray 603 on which a plurality of sheets S are placed.

First, the paper S is taken in from the paper feed tray 603. Next, the image forming unit 601 forms an image on the paper S conveyed by the conveying mechanism 604. After that, the paper S is discharged to the output tray 605.

The image forming unit 601 has a liquid tank in which a liquid to be a recording liquid is stored. Further, the image forming unit 601 has line type heads 410y, 410m, 410c and 410k of each color. The line heads 410y, 410m, 410c and 410k of each color have lengths corresponding to the lengths in the width direction of the paper, that is, in the direction orthogonal to the transport direction. Further, the line type heads 410y, 410m, 410c and 410k of each color are attached to a head holder or the like. The line-type heads 410y, 410m, 410c and 410k of each color eject droplets onto the paper S in the order of black, cyan, magenta and yellow from the upstream side in the transport direction.

The line heads 410y, 410m, 410c and 410k of each color may be one head in which a plurality of nozzles for ejecting droplets of each color are arranged at predetermined intervals. Further, the line type heads 410y, 410m, 410c and 410k of each color may have a configuration in which the head and the cartridge are separate.

The paper S placed on the paper feed tray 603 is separated one by one by the paper feed roller 421. Next, the paper S is conveyed to the conveying mechanism 604 by the paper feeding roller 425.

The transport mechanism 604 has a transport belt 433 and the like spanned between the drive roller 431 and the driven roller 432. In addition, a charging roller 434 that charges the surface of the transport belt 433 is provided.

Further, the inkjet printer 501 has a guide member 435 and the like at a position facing the image forming unit 601. Further, the inkjet printer 501 has a cleaning roller or the like made of a porous body or the like in order to remove the ink adhering to the transport belt 433. Furthermore, the inkjet printer 501 has a static elimination roller or the like made of conductive rubber or the like in order to statically eliminate the paper S. In addition, the inkjet printer 501 has a pressing roller or the like that presses the paper S against the transport belt 433.

Further, on the downstream side of the transport mechanism 604, a paper ejection roller 438 and a paper ejection roller 439 for ejecting the image-formed paper S are provided.

Even in the inkjet printer 501 having such a full-line head, when the transport belt 433 is charged and the paper S is transported to the transport belt 433, the paper S is adsorbed on the transport belt 433. Next, the paper S is conveyed by the transfer belt 433. Subsequently, the image forming unit 601 forms an image on the paper S. After that, the paper S is discharged to the output tray 605.

The image forming apparatus according to the present invention may be an apparatus in which the head having a carriage moves as shown in FIGS. 16 and 17, or may be an apparatus having a full-line head as shown in FIG. That is, the image forming apparatus according to the present invention may be an apparatus in which the recording medium and the ejection head move relatively.

The image forming apparatus according to the present invention can be applied to, for example, an apparatus having a single function of a printer, a facsimile or a copy. Further, the image forming apparatus according to the present invention can be applied to a multifunction device or the like having a plurality of functions such as a printer, a facsimile and a copy. Further, the droplet is not limited to the ink, and may be another type of recording liquid, fixing treatment liquid, or the like. That is, the image forming apparatus according to the present invention may be applied to an apparatus that ejects droplets of a type other than ink.

Therefore, the device for ejecting droplets or the apparatus for using a unit for ejecting droplets according to the present invention is not limited to forming an image. For example, the formed object may be a three-dimensional model or the like.

Further, the recording medium is not limited to paper or the like. The recording medium may be made of a material to which droplets can adhere. For example, the material to which the liquid can adhere may be any material such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, or a combination thereof, as long as it can adhere even temporarily.

Further, the embodiment according to the present invention may be realized by a program for causing a computer such as an image forming apparatus to perform image forming.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are made within the scope of the gist of the present invention described in the claims. Or it can be changed.

300 Unit that ejects droplets 350 Control unit 4 Nozzle 6 Liquid chamber 7 Fluid resistance unit 121 Piezoelectric element 12 Drive element (piezoelectric member)
15 Common electrode (second electrode)
16 Individual electrode (first electrode)
208, 208-1 Print control device (drive control unit)
209 Discharge head (droplet discharge head)
301 Common drive waveform generation unit 302 Transmission unit 310 (310a to 310x), 320 (320a to 320x) Drive waveform generation unit 311 Discharge pulse selection unit (data selection unit)
312,321 Intermediate voltage correction value storage area (first storage area)
313,322 Drive voltage correction value storage area (second storage area)
315,325 Storage means 314 Drive waveform correction unit 323 Common drive waveform correction unit 324 Drive waveform selection unit (waveform selection unit)
209 Discharge head (droplet discharge head)
21,251 Conveyance belt (conveyance means)
500,501 Inkjet printer (image forming device, droplet ejection device)
L Liquid S Paper (Recording medium)
a1 Intermediate voltage b Drive voltage

JP 2015-212101

Claims (10)

A plurality of nozzles for ejecting droplets, a plurality of liquid chambers communicating with each of the plurality of nozzles, a plurality of driving elements for changing the volume of each of the plurality of liquid chambers, and connected to each of the driving elements 2 A droplet ejection head with two electrodes and
A unit for ejecting droplets, comprising a control unit for controlling the ejection of droplets.
The two electrodes connected to each drive element include a first electrode and a second electrode in which a voltage that changes into a waveform is individually applied to each drive element.
By applying a voltage that changes to the waveform to the plurality of first electrodes and changing the potential difference between the two electrodes into a waveform, the plurality of driving elements change the volume of each of the corresponding liquid chambers.
The voltage that changes to the waveform is a driving portion in which the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes in front of the driving portion. It includes a voltage holding portion including a predetermined intermediate voltage, which has a predetermined potential difference.
In the control unit, the intermediate voltage of the voltage that changes to the waveform given to the first electrode connected to each drive element corresponding to each liquid chamber is set according to the characteristics of each liquid chamber and the nozzle. It is characterized in that correction is performed independently for each of the driving elements .
A unit that ejects droplets. In the control unit, the driving portion of a voltage that changes to the waveform given to the first electrode connected to the driving element corresponding to each liquid chamber according to the characteristics of each liquid chamber and the nozzle. Is characterized by being corrected independently of each other.
The unit for ejecting the droplet according to claim 1. The control unit
A common drive waveform generator that generates a common drive waveform that includes multiple drive waveform data that is the basis of the voltage that changes into a waveform that contributes to the formation of droplets of multiple drop sizes.
A data selection unit that selects one or more drive waveform data from the common drive waveform according to the size of the droplet to be discharged, and
A first storage area for storing an intermediate voltage correction value of a voltage changing to the waveform associated with the characteristics of the liquid chamber and the nozzle, and a voltage changing to the waveform associated with the characteristics of the liquid chamber. A storage unit including a second storage area for storing the drive voltage correction value of
The voltage that changes to the waveform by reflecting the intermediate voltage correction value stored in the first storage area and the drive voltage correction value stored in the second storage area in the selected drive waveform data. It is equipped with a drive waveform correction unit that generates a drive waveform that is
The first storage area, the second storage area, and the drive waveform correction unit are provided corresponding to each of the liquid chambers.
The unit for ejecting the droplet according to claim 2. The control unit
A common drive waveform generator that generates a common drive waveform that includes multiple drive waveform data that contribute to the formation of drops of multiple drop sizes,
A first storage area for storing an intermediate voltage correction value of a voltage changing to the waveform associated with the characteristics of the liquid chamber and the nozzle, and a voltage changing to the waveform associated with the characteristics of the liquid chamber. A storage unit including a second storage area for storing the drive voltage correction value of
The intermediate voltage correction value stored in the first storage area and the drive voltage correction value stored in the second storage area are reflected in the common drive waveform to generate a corrected common drive waveform. , Equipped with a common drive waveform correction unit,
A waveform selection unit that selects one or more corrected drive waveform data from the corrected common drive waveforms and generates a drive waveform that is a voltage that changes to the waveform.
The first storage area, the second storage area, the common drive waveform correction unit, and the waveform selection unit are provided corresponding to the respective liquid chambers.
The unit for ejecting the droplet according to claim 1. Due to the characteristics of the liquid chamber and the nozzle, the liquid chamber has a large fluctuation in the volume of the liquid chamber.
The intermediate voltage correction value and the drive voltage correction value are set to values that increase the potential difference between the two electrodes.
The unit that ejects the droplet according to claim 3 or 4. Due to the characteristics of the liquid chamber and the nozzle, for a liquid chamber in which the fluctuation amount of the volume of the liquid chamber is small,
The intermediate voltage correction value and the drive voltage correction value are set to values such that the potential difference between the two electrodes becomes small.
The unit that ejects the droplet according to claim 3 or 4. In the control unit, when the driving element is driven at a low frequency, the discharge droplet volume discharged from the nozzle is larger than the standard deviation of the discharge droplet volume distribution among the plurality of nozzles. ,
It is characterized in that the standard deviation of the discharge droplet volume distribution between the plurality of nozzles is corrected so as to be small during high-frequency driving.
The unit that ejects the droplet according to any one of claims 1 to 6. The second electrode is a common electrode to which a voltage common to the plurality of driving elements is applied.
The unit that ejects the droplet according to any one of claims 1 to 7. The unit that ejects the droplet according to any one of claims 1 to 8.
A transport means for moving the recording medium relative to the unit that ejects the droplets is provided.
Droplet ejection device. A plurality of nozzles for ejecting droplets, a plurality of liquid chambers communicating with each of the plurality of nozzles, a plurality of driving elements for changing the volume of each of the plurality of liquid chambers, and connected to each of the driving elements 2 A method of controlling a droplet ejection head having two electrodes.
A generation step that generates drive waveform data that is the basis of the voltage that changes into a waveform,
A correction step in which each drive element independently corrects the drive waveform data to generate a voltage that changes into a waveform according to the characteristics of each liquid chamber.
By applying a voltage that changes to each waveform to the first electrode connected to each of the driving elements and changing the potential difference between the two electrodes into a waveform, the plurality of driving elements are connected to each of the corresponding liquid chambers. It has a discharge step that changes the volume and discharges droplets.
The drive waveform data defines a drive portion in which the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes in front of the drive portion. A voltage holding portion including a predetermined intermediate voltage, which is a potential difference between the two, is included.
Wherein in the correction step, according to the characteristics of the liquid chambers, the intermediate voltage of the voltage that changes the waveform applied to said first electrodes connected to the respective drive elements corresponding to the liquid chambers, each said The feature is that each drive element is corrected independently.
How to control the droplet ejection head.

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