JPH10217460A - Ink jet recorder and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder and a method therefor capable of representing multiple gradations. SOLUTION: In a head driver of this ink jet printer, when an image signal Vin is inputted, a piezoeloctric element driving voltage Vout, consisting of a signal Vh1 outputted via a delay circuit 101, a circuit 102 wherein a lamp waveform discharging circuit and an inverting circuit are combined and an inversion amplifier circuit 103 and a signal Vh2 outputted via a pre-AC generator circuit, is generated. The driving voltage Vout is applied to the piezoelectric element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording apparatus and method, and more particularly to an ink-jet recording apparatus and method for driving a piezoelectric element and discharging ink to record an image.

[0002]

2. Description of the Related Art Heretofore, there has been an ink jet printer using a piezoelectric element as a print head. In such a printer head, ink in a predetermined closed space (ink channel) is pressurized by distortion of a piezoelectric element driven by application of a voltage. The pressurized ink flies toward the recording sheet as ink droplets (ink drops) from nozzles provided in a predetermined closed space.

Further, in such a printer head, gradation is expressed by flying ink droplets having a plurality of diameters. At present, a driving device for driving a piezoelectric element for printing a multi-gradation image with such a printer head is required.

[0004]

In order to meet the above-mentioned need, there has been proposed a method of applying a pre-pulse voltage before a main pulse voltage corresponding to an image signal for driving a piezoelectric element. According to such a method, the piezoelectric element to which the pre-pulse voltage is applied can vibrate the ink in the ink channel in preparation for the application of the main pulse voltage, and can fly a larger diameter ink with a small drive voltage. it can.

FIG. 13 is a diagram for explaining a method of applying a pre-pulse voltage before a main pulse voltage. FIG. 13A shows a first example in which a pre-pulse voltage in the same direction as the driving direction of the piezoelectric element is applied before the main pulse voltage for driving the piezoelectric element, and FIG. 13B shows the driving of the piezoelectric element. A second example in which a pre-pulse voltage in a direction opposite to the driving direction of the piezoelectric element is applied before the main pulse voltage is shown.

[0006] The main pulse voltage is applied so that the piezoelectric element is driven in a direction to press the ink. In the first example, a pre-pulse voltage is applied so that the piezoelectric element is driven in the direction of pressurizing the ink, and in the second example, the pre-pulse voltage is applied so that the piezoelectric element is driven in the direction of depressurizing the ink. I have.

However, since the pre-pulse voltage applied by such a method is either pressurization or depressurization of the ink, the main pulse voltage is to fly the ink droplet efficiently. Absent.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet recording apparatus and a method capable of expressing more gradations.

Another object of the present invention is to provide an ink jet recording apparatus and method which can reduce the load on a driving device for driving a piezoelectric element.

[0010]

According to a first aspect of the present invention, an alternating electric field is applied to a piezoelectric element in response to print data, and after the alternating electric field is applied, a predetermined magnitude of electric field is applied based on the print data. An ink jet recording apparatus characterized in that a voltage is applied to a piezoelectric element to eject ink.

According to a second aspect of the present invention, there is provided a first step of applying an alternating electric field to a piezoelectric element in response to print data, and after the first step, a voltage of a predetermined magnitude based on the print data. And a second step of ejecting ink by applying the ink jet recording method.

According to the first or second aspect of the present invention, after the alternating voltage is applied to the piezoelectric element, the voltage corresponding to the data is applied. Thus, the voltage applied to the piezoelectric element for causing ink droplets of the same size to fly can be further reduced, so that more gradations can be expressed. Further, the load on the driving device for driving the piezoelectric element can be further reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet printer 1 having a head driver for driving a piezoelectric element, which is one embodiment of the present invention, will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of an ink jet printer 1 according to one embodiment of the present invention.

[0015] The ink jet printer 1 uses paper or OH.
A recording sheet 2 that is a recording medium such as a P sheet, an inkjet head 3 that is an inkjet printer head, a carriage 4 that holds the inkjet head 3, and the carriage 4 is reciprocated in parallel with the recording surface of the recording sheet 2. Shafts 5 and 6 for driving, a drive motor 7 for reciprocatingly driving the carriage 4 along the swing shafts 5 and 6,
A timing belt 9 for changing the rotation of the drive motor 7 into a reciprocating motion of the carriage and an idle pulley 8 are included.

The ink jet printer 1 has a platen 10 also serving as a guide plate for guiding the recording sheet 2 along the transport path, a paper pressing plate 11 for pressing the recording sheet 2 between the platen 10 and preventing floating. Recording sheet 2
Roller 12, spur roller 13 for discharging
It includes a recovery system 14 for recovering the ink ejection failure of the inkjet head 3 to a satisfactory state, and a paper feed knob 15 for manually conveying the recording sheet 2.

The recording sheet 2 is fed to a recording section where the ink jet head 3 and the platen 10 face each other by a paper feeding device such as a manual feed or a cut sheet feeder. At this time, the rotation amount of a paper feed roller (not shown) is controlled, and the conveyance to the recording unit is controlled.

The ink jet head 3 uses a piezoelectric element (PZT) as an energy source for flying ink. A voltage is applied to the piezoelectric element, causing distortion. This distortion changes the volume of the channel filled with ink. Due to this change in volume, ink is ejected from nozzles provided in the channel, and recording on the recording sheet 2 is performed.

The carriage 4 is driven by the drive motor 7, the idle pulley 8, and the timing belt 9 to perform main scanning in the digit direction of the recording sheet 2 (a direction crossing the recording sheet 2).
Record the image for the line. Each time recording of one line is completed, the recording sheet 2 is fed in the vertical direction and sub-scanned, and the next line is recorded.

The image is recorded on the recording sheet 2 in this manner, and the recording sheet 2 that has passed through the recording section is discharged by a discharge roller 12 disposed downstream of the conveyance direction and a spur roller 13 pressed against the discharge roller 12. Is done.

FIG. 2, FIG. 3, and FIG. 4 are views for explaining the configuration of the ink jet head 3. FIG. FIG. 2 is a plan view showing a part of the ink jet head 3, and FIG.
FIG. 4 is a sectional view taken along line III-III of FIG.
FIG. 4 is a sectional view taken along line IV.

The ink jet head 3 has a large diameter head 301 and a small diameter head 302. The large-diameter head section 301 and the small-diameter head section 302 include a channel plate 303, a partition wall 304, a diaphragm 305, and a substrate 306.
And are integrated with each other. Among the ink droplets having a plurality of dot diameters, a large-diameter head portion 301 ejects an ink droplet having a large dot diameter, and a small-diameter head portion 302 ejects an ink droplet having a small dot diameter.

The channel plate 303 is made of metal or ceramic, and has a water-repellent coating layer on the surface 320. The surface facing the partition wall 304 is finely processed by Ni electroforming or a photoresist, etc.
A plurality of ink channels 308 for accommodating ink 307 and an ink inlet 311 for connecting each ink channel 308 to an ink supply chamber 310 are formed in the small-diameter head portion 302 and the small-diameter head portion 302, respectively.

As shown in FIG. 3, the ink channels 308 of the large-diameter head portion 301 and the small-diameter head portion 302 have a long groove shape extending in the direction in which the large-diameter head portion 301 and the small-diameter head portion 302 face each other. They are formed in parallel. In addition, the ink supply chamber 310 and the ink channel 30
8 is formed symmetrically with respect to the center line 312,
It is connected to an ink tank (not shown).

A thin film is used for the partition wall 304, and is fixed between the channel plate 303 and the diaphragm 305. The partition 304 is fixed in a state where a predetermined tension is applied.

The diaphragm 305 includes the PZT 315. The processing of the diaphragm 305 is first fixed to the substrate 306 with an insulating adhesive, and then the separate grooves 3 are formed by dicer processing.
18 and 319 are formed and divided. In addition, due to this division, each ink channel 30
8, the PZT column 316 located between the adjacent PZTs 315, and the surrounding wall 317 surrounding them are separated.

The operation of the PZT 315 is controlled by the control unit of the ink jet printer 1 via a head driver 56 (see FIG. 5) described later. When a predetermined voltage, which is a print signal, is applied between two electrodes provided on the piezoelectric element from the control unit, the PZT 315 is deformed in the direction of arrow D1. The deformation of the PZT 315 is transmitted to the partition 304, thereby causing the ink 30
7 is pressurized, and the ink droplet flies toward the recording sheet 2 via the nozzle 309.

In the ink jet head 3 having the above-described structure, the ink 307 is supplied to the ink supply chamber 310 from an ink tank (not shown). Ink supply chamber 3
The ten inks 307 are distributed to each ink channel 308 via the ink inlet 311.

In this embodiment, an ink jet head having a large diameter nozzle and a small diameter nozzle has been described, but the diameter of the nozzle may be the same. When applying the present invention to an ink jet head having a nozzle having the same diameter and controlling the dot diameter to perform gradation printing, it is particularly important to accurately control the dot diameter and prevent the dot diameter from varying. Therefore, the present invention is effective.

FIG. 5 is a block diagram showing the configuration of the control unit of the ink jet printer 1. The main controller 51 receives image data from a computer or the like, and the image data is stored in a buffer frame memory 52 in units of one frame. When printing on the recording sheet 2,
The main controller 51 includes motor drivers 54 and 55
The drive motor 7 of the carriage 4 and the paper feed motor are driven and controlled via the.

Along with these drive controls, the main controller 51 controls the large-diameter head 301 and the small-diameter head 302 via the driver controller 53 and the head driver 56 based on the image data read from the frame memory 52. The driving of each piezoelectric element 315 is controlled.

FIG. 6 is a diagram showing a schematic configuration of the head driver 56 and a voltage applied by the head driver 56.

As described above, the head driver 56 includes:
The driver controller 53 and the inkjet head 3 are connected. From the driver controller 53 to the head driver 56, it corresponds to the dot diameter of the ink to be printed,
A signal Vin, which is a square pulse voltage of 0 to 5 V representing an image signal, is input, and a driving voltage Vout for driving each piezoelectric element 315 in the inkjet head 3 is output from the head driver 56 to the inkjet head 3.

The head driver 56 includes a delay circuit 101
, A circuit 102 combining a discharge circuit for ramp waveform and an inverting circuit (hereinafter, referred to as an inverting circuit 102), an inverting amplifying circuit 103, and a pre-AC generating circuit 104.
The output of the delay circuit 101 and the input of the inverting circuit 102, and the output of the inverting circuit 102 and the input of the inverting amplifier 103 are connected in series via nodes n2 and n3, respectively. The input of the delay circuit 101 is connected to the node n1 and the output of the inverting amplifier 103 is connected to the node n4. In parallel with these, the input of the pre-AC generation circuit 104 is connected to the node n1 and the output is connected to the node n4.

In FIG. 6, an image signal Vin is input from a node n1 to a delay circuit 101, and the delay circuit 101 outputs a signal Vd obtained by delaying the image signal. Inverting circuit 1
02 inputs the signal Vd and outputs a signal Vo obtained by inverting the signal Vd, which is a square wave, into a ramp waveform signal. This signal Vo is input to the inverting amplifier circuit 103, and the inverting amplifier circuit 103 inverts and amplifies the signal Vo to obtain the signal Vh.
1 is output toward the node n4. At the same time, the image signal Vin is supplied from the node n1 to the pre-AC generation circuit 104.
And the pre-AC generation circuit 104 outputs the image signal Vi
In response to n, a sinusoidal alternating voltage is output toward node n4.

From the node n4, the drive voltage Vout is output from the output Vh1 of the piezoelectric amplification circuit 103 and the output Vh2 of the pre-AC generation circuit 104 generated as described above, and the PZT 315 of the ink jet head 3 is driven. You.

FIGS. 7 to 10 are diagrams for explaining the configuration of the circuit in the head driver 56. FIG. FIG. 7 is a diagram showing an example of the delay circuit 101, FIG. 8 is a diagram showing an example of the inverting circuit 102, FIG. 9 is a diagram showing an example of the inverting amplifier circuit 103, and FIG. FIG. 4 is a diagram showing an example of the example 104.

The signal Vin shown in FIG.
Is input to output a signal Vd, and the inverting amplifier circuit 102 receives the signal Vd and outputs a signal Vo. The inverting amplifier 103 receives the signal Vo and outputs the signal Vh1, and the pre-AC generator 104 receives the signal Vin and outputs the signal Vh2. These individual circuits are used for general purposes, and a description thereof will be omitted.

Next, the dot diameter of the ink from the piezoelectric element driven by the applied voltage having the pulse waveform after the ink has adhered to the recording sheet will be described in comparison with the conventional example.

FIG. 11 is a diagram showing the dot diameter after the recording sheet is attached to the applied voltage Vo of the main pulse applied to the piezoelectric element. FIG. 12 is a diagram showing the driving applied to the piezoelectric element, which comprises a pre-pulse and a main pulse. FIG. 3 is a diagram illustrating a voltage waveform. FIG. 12A shows the waveform of the driving voltage of the piezoelectric element according to the present invention, and FIG. 12B shows the waveform of the driving voltage of the conventional piezoelectric element. The conditions other than the driving voltage waveform are the same. .

Here, only the nozzle (nozzle diameter 30 μm) of the above-mentioned large diameter head portion is used. In addition, a piezoelectric element in which 17 layers of 35 μm PZT per layer are stacked is used.

As shown in FIG. 12A, in the present invention, a pulse voltage as a print signal corresponding to one dot is a pre-pulse voltage consisting of one cycle of an alternating voltage having a cycle of 20 μsec, and this pre-pulse is applied. 10 μs
c), and the trapezoidal main pulse voltage to be applied. The amplitude of the pre-pulse voltage is 8 V, and the main pulse voltage rises with an extremely small rising time, continues with the amplitude Vo changed according to the dot diameter of the ink, and then falls with a falling time of 50 μsec. The time interval between a certain pulse voltage and the next successive pulse voltage is the reciprocal of the driving frequency.

As shown in FIG. 12 (b), in the conventional example, the square wave of the pre-pulse voltage rises with a short rise time, continues at an amplitude of 4 V for 10 μsec, and falls again with a small fall time. . This square wave is applied only in the same direction as the main pulse voltage. The time interval between the pre-pulse voltage and the main pulse voltage, and the main pulse voltage are the same as the drive voltage in the present invention.

The horizontal axis of the graph shown in FIG. 11 represents the applied voltage Vo (V) of the main pulse shown in FIG. 12, and the vertical axis represents the dot of the ink after the recording sheet adheres when the applied voltage Vo is changed. The diameter (μm) is shown. In FIG. 11, a black circle indicates printing when the piezoelectric element is driven by the pulse voltage shown in FIG. 12A in the ink jet printer according to the present invention, and a white circle indicates a pulse shown in FIG. 12B in the conventional ink jet printer. 7 shows printing when a piezoelectric element is driven by a voltage.

As shown in FIG. 11, the difference in the waveform of the pre-pulse voltage as described above has a great influence on the dot diameter of the ink after the recording sheet is attached.

By using the driving waveform according to the present invention, a piezoelectric element which can be driven only by an applied voltage of a main pulse of 20 V or more can be driven by a smaller voltage. Further, even if a main pulse having the same size as that of the related art is applied, an ink drop having a larger dot diameter can be obtained by using the driving waveform according to the present invention.

In an ink jet printer having a piezoelectric element driven by the above-described drive waveform, the voltage applied to the piezoelectric element can be further reduced, so that more gradations can be expressed. Further, the load on the driving device for driving the piezoelectric element can be further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an inkjet printer 1 according to one embodiment of the present invention.

FIG. 2 is a plan view showing a part of the inkjet head 3 for explaining a configuration of the inkjet head 3. FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2 for explaining the configuration of the inkjet head 3.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3 for explaining the configuration of the inkjet head 3.

FIG. 5 is a block diagram illustrating a configuration of a control unit of the inkjet printer 1.

FIG. 6 is a diagram showing a schematic configuration of a head driver 56 and a voltage applied by the head driver 56.

FIG. 7 is a diagram showing an example of a delay circuit 101 in a head driver 56.

FIG. 8 is a diagram showing an example of an inversion circuit 102 in a head driver 56.

FIG. 9 is a diagram showing an example of an inverting amplifier circuit 103 in the head driver 56.

FIG. 10 shows a pre-AC generation circuit 1 in a head driver 56.
It is a figure showing the example of No. 04.

FIG. 11 is a diagram illustrating a dot diameter after a recording sheet is adhered to an applied voltage Vo of a main pulse applied to a piezoelectric element.

FIG. 12 is a diagram showing a waveform of a drive voltage composed of a pre-pulse and a main pulse and applied to a piezoelectric element.

FIG. 13 is a diagram for explaining a method of applying a pre-pulse voltage before a main pulse voltage.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 inkjet printer 3 printer head 56 head driver 101 delay circuit 102 circuit combining discharge circuit for ramp waveform and inversion circuit 103 inversion amplification circuit 104 pre-AC generation circuit 315 PZT Vin image signal Vd, Vo, Vh1, Vh2 signal Vout piezoelectric Device drive voltage

Claims (2)

[Claims] An alternating electric field is applied to a piezoelectric element in response to print data, and after applying the alternating electric field, a voltage of a predetermined magnitude is applied to the piezoelectric element based on the print data to eject ink. An ink jet recording apparatus, characterized in that: 2. A first step of applying an alternating electric field to a piezoelectric element in response to print data, and after the first step, applying a voltage of a predetermined magnitude to the piezoelectric element based on the print data. A second step of discharging ink.