JPH05246034A - Continuous ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To record a dot at a predetermined place regardless of a dot size by correcting the delay quantity due to the air resistance depending on the dot size. CONSTITUTION:A vibrator driver CD drives a piezoelectric vibrator 3 on the basis of the granulating frequency signal fd from an oscillator OSC to divide the ink jet emitted from a nozzle 1 into ink particle rows. A delay pulse generator DPG converts an encoder clock fE to an encoder clock fE* to which a delay time of an integral multiple of the cycle 1/fd of the granulating frequency signal fd is applied corresponding to the value of pixel data DP to output the same. A pulse width modulator PWM outputs a charge control signal SC rising in synchronous relation to the encoder clock fE* and having pulse width an integral multiple of the cycle 1/fd of the granulating frequency signal fd corresponding to the value of the pixel data DP and the signal SC* is boosted by a high voltage switch HVS to be applied to a control electrode 4. As a result, the delay quantity due to the air resistance of the ink particle rows is corrected on the basis of a delay time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous jet type ink jet recording apparatus, and more specifically, continuous jetting capable of expressing light and shade by changing the recording dot diameter by variably controlling the number of ink particles ejected per pixel. Type inkjet recording apparatus, the present invention relates to a technique for improving the image quality by accurately controlling the recording dot position regardless of the recording dot diameter.

[0002]

2. Description of the Related Art Using continuous jet type ink jet technology,
The technology for expressing the shading by changing the recording dot diameter by variably controlling the number of ink particles ejected per pixel is
For example, US Pat. No. 4,620,196 and JP-A-62-2
It is disclosed in Japanese Patent No. 25363.

FIG. 4 is a block diagram showing a conventional rotary drum type continuous jet type ink jet recording apparatus. This continuous jet type ink jet recording apparatus includes a nozzle 1 to which pressurized ink is supplied, an ink electrode 2 for setting the electric potential of the ink in the nozzle 1 to a ground level, and a piezoelectric vibrator 3 attached to the nozzle 1. , An oscillator OSC for generating a particleization frequency signal f _d having a constant particleization frequency f _d (hereinafter, the signal will be described with the same reference numeral as the frequency), and a particleization frequency signal f _d from the oscillator OSC. And a piezoelectric vibrator driver CD that drives the piezo vibrator 3 to make the ink jet into particles in synchronism therewith, and has a circular opening or a slit-like opening that is concentric with the nozzle 1 and charges the ink jet corresponding to pixel data. a control electrode 4 which controls the charge control signal S _C is applied, and the ground electrode 5 which is arranged to be grounded in the front of the control electrode 4, a knife edge mounted to the ground electrode 5 6 , A high voltage DC power supply for deflection (hereinafter, simply referred to as a deflection power supply) 7 and a grounding electrode 5 connected to the deflection power supply 7 to create a strong electric field orthogonal to the inkjet flight axis and deflect the charged ink particles to the grounding electrode 5 side. Deflection electrode 8, a line buffer LB for storing pixel data for one rotation of the rotating drum DR for generating the charging control signal S _C , and a shaft encoder SE coupled to the shaft of the rotating drum DR.
Encoder clock (dot recording clock) f _{E from}
A pulse width modulator PWM that converts the pixel data D _P read from the line buffer LB in synchronization with the pulse width into a pulse width in synchronization with the encoder clock f _E and the particle frequency signal f _d from the oscillator OSC; High-voltage switch HVS for converting the output of the pulse width modulator PWM into the charging control signal S _C
From that, the main part was composed. In addition, in FIG.
Reference numeral RM indicates a recording medium wound around the rotary drum DR.

The pulse width modulator PWM is provided with pixel data D corresponding to the pixel density read from the line buffer LB.
_P is converted into a charging control signal S _C having a pulse width corresponding to the value. The pulse width modulator PWM is composed of, for example, a preset down counter. That is, if the pixel data D _P is preset with the encoder clock f _E and the particle frequency signal f _d is input as the down clock,
The time from presetting until the preset down counter becomes empty is the pulse width of the charging control signal S _C.

FIG. 5 is a diagram for explaining the principle of variably controlling the recording dot diameter by pulse width modulation used in the conventional continuous jet type ink jet recording apparatus shown in FIG. Here, for the sake of convenience, the case where 9 gradations are expressed is illustrated, and the encoder clock f _E that is the output of the shaft encoder SE has a frequency that is ⅛ of the particle frequency signal f _d that is the output of the oscillator OSC. Moreover, the phase is designed to be locked to the particle frequency signal f _d . Eight ink particles in one cycle of the encoder clock f _E form one pixel. The recording dot diameter is controlled by the number of non-charged ink particles out of eight, and the number of non-charged ink particles is stored in the line buffer LB as pixel data D _P. In FIG. 5, the black circles represent uncharged ink particles, which travel straight without being deflected and are recorded on the recording medium RM, and the white circles represent charged ink particles, which are deflected and cut by the knife edge 6 to form the recording medium R.
It does not reach above M. In particular, in FIG. 5, one pixel is 1,
The case of being formed with 3 and 5 ink particles is illustrated.

In such a conventional continuous jet type ink jet recording apparatus, the non-charged ink particle train to be recorded flies in the air and is decelerated by the air resistance. The degree of reduction, i.e. delay amount t _d is dependent inks the number of particles constituting the ink particles columns. That is, when a plurality of ink particle rows fly in the air, the head ink particles are most decelerated due to the air resistance and are combined with the subsequent ink particles. This is repeated, and the ink particle row is changed to that shown in FIG.
As shown in, the ink particles are in the form of dumplings. The size of the ink particle group changes in proportion to the number of ink particles forming the ink particle row. The deceleration rate of ink particles flying in the air is inversely proportional to the size of the ink particles (viscosity resistance is proportional to (particle size) ² / (particle size) ³ ). For example, FIG. 6 shows the delay amounts t _d1 , t _d3, and t _{d5 in} each case where the ink particle row for recording one pixel is composed of 1, 3 and 5 ink particles, respectively. , The amount of delay t _d1 , t in inverse proportion to the size (dot size) of the ink particle group
_d3 and t _d5 become large (generally t _d1 > t _d2 > t
_d3 >…). When dots are recorded on the recording medium RM in a state where the delay amount t _d is different, the positional deviation of the recording dots occurs according to the dot size. That is, smaller dots (dots with lower density) are printed later.

[0007]

In the above-mentioned conventional continuous jet type ink jet recording apparatus, since the delay amount t _d is different depending on the dot size, the recording dot is displaced, so that the recorded image is recorded. However, there was a problem that the position shift was conspicuous at the place where the concentration changed abruptly. In particular, there is a problem in that when a color image in which a color having a large ratio of C (cyan), M (magenta), and Y (yellow) is greatly different is expressed, a remarkable color shift occurs.

In view of the above points, the object of the present invention is to correct the delay amount t _d depending on the dot size so that the dots are recorded at a predetermined location regardless of the dot size. To provide a device.

More specifically, as shown in FIG.
The charge control signal S _C is delayed by a delay time Δt according to its pulse width.
_{1, Δt 2, Δt 3,} converted ... into the charge control signal S _C ^* with, by controlling the charging of the ink particles in the charge control signal S _C ^* to correct the delay amount t _d by the air resistance,
It is an object of the present invention to provide a continuous jet type inkjet recording apparatus in which recording dots can be accurately positioned regardless of the dot size.

[0010]

SUMMARY OF THE INVENTION A continuous jet type ink jet recording apparatus of the present invention comprises a particle frequency signal generating means for outputting a particle frequency signal, and a series of ink particles for ink jet synchronized with the particle frequency signal. Particle forming means for dividing into rows, storage means for storing pixel data to be recorded, charging means for charging ink particles by a charge control signal according to the pixel data from the storage means, and charging by this charging means And a delay unit for delaying the charging signal input to the charging unit according to the pixel data from the storage unit.

In the continuous jet type ink jet recording apparatus of the present invention, the particle generation frequency signal generating means for outputting the particle formation frequency signal and the ink jet are divided into a series of ink particle rows in synchronization with the particle formation frequency signal. Particle forming means, storage means for storing pixel data to be recorded, pulse width modulation means for modulating pixel data from the storage means into a charge control signal having a pulse width corresponding to the value, and pulse width modulation means. Charging means for charging ink particles with a charge control signal pulse-width modulated by the deflecting means, deflecting means for deflecting the ink particles charged by the charging means, and inputting to the charging means according to pixel data from the storage means. Delaying means for delaying the charging control signal.

[0012]

In the continuous jet type ink jet recording apparatus of the present invention, the particle generation frequency signal generating means outputs the particle formation frequency signal, and the particle formation means divides the ink jet into a series of ink particle rows in synchronization with the particle formation frequency signal. The storage means stores the pixel data to be recorded, the charging means charges the ink particles with a charging control signal according to the pixel data from the storage means, and the deflecting means deflects the ink particles charged by the charging means. The delay unit delays the charging signal input to the charging unit according to the pixel data from the storage unit.

In the continuous jet type ink jet recording apparatus of the present invention, the particle generation frequency signal generating means outputs the particle formation frequency signal, and the particle formation means synchronizes the particle formation frequency signal with the inkjet to form a series of ink particle trains. Split into
The storage means stores the pixel data to be recorded, the pulse width modulation means modulates the pixel data from the storage means into a charging control signal having a pulse width corresponding to the value, and the charging means modulates the pulse width by the pulse width modulation means. The ink particles are charged by the charged charging control signal, the deflection unit deflects the charged ink particles by the charging unit, and the delay unit delays the charging control signal input to the charging unit according to the pixel data from the storage unit. Let

[0014]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a continuous jet type ink jet recording apparatus according to an embodiment of the present invention. The continuous jet type ink jet recording apparatus of this embodiment is different from the conventional continuous jet type ink jet recording apparatus shown in FIG.
The delay pulse generator DPG is added.
Therefore, the other parts are configured in the same manner as the corresponding parts in the conventional continuous jet type ink jet recording apparatus shown in FIG. 4, and the corresponding parts are designated by the same reference numerals and their detailed description will be given. Omit it.

In the delay pulse generator DPG, the pixel data D _P which is the output of the line buffer LB, the encoder clock f _E which is the output of the shaft encoder SE, and the particle frequency signal f _d which is the output of the oscillator OSC are supplied. Has been entered. The encoder clock f _E undergoes a time delay according to the value of the pixel data D _P in the delay pulse generator DPG, is converted into an encoder clock f _E ^* , and is output. The encoder clock f _E is output to the pulse width modulator PWM by the dot recording clock (charging). It is input to determine the rising edge of the control signal S _C ^* (see FIG. 7)). Delay time Δt ₁ , Δ of charging control signal S _C ^*
t ₂ , Δt ₃ , ... Are integer multiples of the period 1 / f _d of the particle frequency signal f _d according to the value of the pixel data D _P n / f _d (n
Is an integer greater than or equal to 0). Here, the pixel data D
The value of n, which represents the relationship between _P and the delay times Δt ₁ , Δt ₂ , Δt ₃ , ... Is based on experimental data, the delay amount t _d due to air resistance is corrected, and the dots are recorded on the recording medium regardless of the dot size. It is decided to hit a predetermined position on the RM. Therefore, the delay times Δt ₁ , Δt ₂ , Δt ₃ , ...
Satisfies ₁ ≤ Δt ₂ ≤ Δt ₃ ≤.

FIG. 2 is a circuit diagram showing an example of the delay pulse generator DPG. The delay pulse generator DPG includes a look-up table LUT and a delay circuit DC, and the encoder clock f _{E is} generated according to the pixel data D _P.
Is delayed and output as an encoder clock f _E ^* . Here, the lookup table LUT converts the pixel data D _P into pixel data D _P ^* . As described above, the pixel data D _P ^* is determined based on the experiment so that each dot hits a predetermined position regardless of the dot size (value of the pixel data D _P ). The delay circuit DC is composed of, for example, a down counter that presets (loads) the pixel data D _P ^* with the encoder clock f _E and subtracts the particle generation period number signal f _d as a clock. The delay times Δt ₁ , Δt ₂ , Δt ₃ , ... From the encoder clock f _E to the encoder clock f _E ^* are pixel data D _P ^*
The period 1 / f _{d of} the particle frequency signal f _d which changes according to
Becomes an integral multiple of n / f _d .

Next, the operation of the continuous jet type ink jet recording apparatus of this embodiment having the above structure will be described.

The oscillator OSC has a constant graining frequency f _d.
And oscillates and outputs the particle frequency signal f _d .

The oscillator driver CD amplifies the particle generation frequency signal f _d from the oscillator OSC to drive the piezo oscillator 3, and synchronizes the ink jet ejected from the nozzle 1 with the particle formation frequency f _d . Break up into ink particles.

On the other hand, the delay pulse generator DPG has the pixel data D _P output from the line buffer LB and the encoder clock f output from the shaft encoder SE.
_E and the particle frequency signal f _d which is the output of the oscillator OSC
And input the encoder clock f _E to the pixel data D _P
The encoder clock f _E ^* is provided with a delay time that is an integer multiple of the cycle 1 / f _d of the particle frequency signal f _d , and is output.

The pulse width modulator PWM is the pixel data D _P which is the output of the line buffer LB, an encoder clock f _E is the output of the shaft encoder SE, an encoder clock f _E is the output of the delay pulse generator DPG
Input ^* and, in synchronization with the encoder clock f _E ^* , the charging control signal S _C ^{* having} a pulse width that is an integral multiple of the cycle 1 / f _d of the particle frequency signal f _d corresponding to the value of the rising pixel data D _P. Is output.

The high voltage switch HVS has a charging control signal S _C.
^* Is converted into high voltage and applied to the control electrode 4.

As a result, the divided ink particle array is
The charge is controlled by the control electrode 4 to form a cluster of ink particle groups according to the number of ink particles. The delay amount t _d due to the air resistance of the ink particle groups generated at this time depends on the value of the pixel data D _P. Delay time Δt of charging control signal S _C ^*
_The dots are hit at a predetermined position on the recording medium RM regardless of the dot size by being corrected by ₁ , Δt ₂ , Δt ₃ , ....

By the way, the delay amount t _d that the ink particle array forming a pixel receives due to the air resistance may be influenced not only by the configuration of the ink particle array of its own pixel but also by the preceding ink particle array. In particular, when the maximum number of ink particles constituting one pixel is small, that is, in the case of image recording with a small gradation, this influence must be taken into consideration. Figure 3
(A), (b) and (c) are circuit diagrams respectively showing an example of the delay pulse generator DPG in which the look-up table LUT is configured in consideration of this history (preceding ink particle column pattern). The delay circuit DC for converting the encoder clock f _E into the encoder clock f _E ^* is shown in FIG.
A circuit similar to the delay circuit DC in the inside can be used.

FIG. 3A is a circuit diagram showing an example of the delay pulse generator DPG which uses the look-up table LUT created in consideration of the preceding ink particle column pattern for one pixel. This delay pulse generator DPG
Is a 1-pixel delay circuit PDC and a lookup table L
It is composed of a UT and a delay circuit DC. In this delay pulse generator DPG, the pixel data D _P to be recorded,
Pixel data D delayed by one pixel by the one-pixel delay circuit PDC
_P-1 and _P-1 are input to the lookup table LUT, and pixel data D _P ^* in consideration of the ink particle column pattern to be recorded and the ink particle column pattern preceding by one pixel are output from the lookup table LUT. The table data of the look-up table LUT is experimentally determined as described above.

FIG. 3B is a circuit diagram showing an example of the delay pulse generator DPG which uses the look-up table LUT created in consideration of the preceding ink particle column pattern for two pixels. This delay pulse generator DPG
Is composed of a two-stage 1-pixel delay circuit PDC, a lookup table LUT, and a delay circuit DC. In this delay pulse generator DPG, the pixel data D to be recorded is recorded.
_P , the pixel data D _P-1 delayed by one pixel by the one-pixel delay circuit PDC, and the pixel data D _P-2 delayed by two pixels by the two-stage one-pixel delay circuit PDC are used as a lookup table L.
Pixel data D _P ^* that is input to the UT and takes into consideration the ink particle row pattern, the ink particle row pattern that precedes by 1 pixel, and the ink particle row pattern that precedes by 2 pixels
Is output from the lookup table LUT. The table data of the look-up table LUT is experimentally determined as described above.

FIG. 3C is a circuit diagram showing an example of the delay pulse generator DPG using the look-up table LUT created in consideration of the preceding ink particle column pattern for n pixels. This delay pulse generator DPG
Is composed of an n-stage 1-pixel delay circuit PDC, a lookup table LUT, and a delay circuit DC. In this delay pulse generator DPG, the pixel data D to be recorded is recorded.
_P , pixel data D _P-1 delayed by 1 pixel by the 1-pixel delay circuit PDC, ..., Pixel data D _Pn delayed by n pixels by the n-stage 1-pixel delay circuit PDC are input to the lookup table LUT, Ink particle row pattern to record,
Pixel data D that takes into account the ink particle row pattern that precedes by one pixel, ...
_P ^* is output from the lookup table LUT. The pixel data D _P ^* of the look-up table LUT is experimentally determined as described above.

When the delayed pulse generator DPG as shown in FIGS. 3 (a), 3 (b) and 3 (c) is used, more recording is performed by taking the previous history (preceding ink particle column pattern) into consideration. It is possible to obtain a high-quality image with no dot displacement.

In the above embodiment, the Hertz type continuous jet type ink jet recording apparatus for deflecting and removing the charged ink particles and recording the non-charged ink particles has been described. However, the non-charged ink particles are removed and the ink is uniformly charged. It is obvious that the present invention can be similarly applied to the continuous ejection type inkjet recording apparatus of the binary deflection type sweet method for recording with the charged ink particles.

Further, the continuous jet type ink jet recording apparatus capable of expressing gradation by pulse width modulation of the charging control signal has been described, but one pixel is composed of one ink particle.
The present invention is similarly applicable to a value recording type continuous jet type ink jet recording apparatus. The delay time in this case is
The delay pulse generator shown in FIGS. 3A, 3B and 3C is used to variably adjust according to the preceding pixel pattern (the preceding ink particle column pattern).

[0032]

As described above, according to the present invention, by providing the delay pulse generator and delaying the charging control signal in accordance with the value of the pixel data to be recorded, it is possible to prevent the misalignment of the recording dots. There is an effect that a quality image can be obtained. In particular, there is an effect that a large color misregistration does not occur even when a color in which a ratio of C, M, and Y amounts greatly differs is expressed in a color image.

Further, by delaying the charging control signal based on the pixel data to be recorded and the preceding pixel data, there is an effect that a high quality image in which there is no positional deviation of the recording dots can be obtained.

Furthermore, by determining the delay time with a look-up table based on experiments, there is an effect that the dot position can be controlled extremely accurately.

Furthermore, the entire system is synchronized with the particle formation by synchronizing the particle formation of the charge control signal with the particle formation frequency signal and giving a delay time which is an integral multiple of the period of the frequency particle formation signal. Therefore, there is an effect that it is possible to realize a high-quality continuous jet type ink jet recording apparatus in which the control for each ink particle is accurately performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a continuous jet type ink jet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a delay pulse generator used in the continuous jet ink jet recording apparatus of this embodiment.

FIG. 3 is a circuit diagram showing another example of the delay pulse generator used in the continuous jet ink jet recording apparatus of this embodiment.

FIG. 4 is a configuration diagram showing a conventional continuous jet type ink jet recording apparatus.

FIG. 5 is a timing chart for explaining the principle of variably controlling the recording dot diameter by pulse width modulation in a conventional continuous jet type inkjet recording device.

FIG. 6 is a diagram illustrating that a recording dot position shifts according to a dot size in a conventional continuous jet type inkjet recording device.

FIG. 7 is a timing chart illustrating a delay time generated in the continuous jet type inkjet recording apparatus of the present embodiment.

[Explanation of symbols]

1 Nozzle 2 Ink Electrode 3 Piezoelectric Oscillator 4 Control Electrode 5 Ground Electrode 6 Knife Edge 7 Deflection Power Supply 8 Deflection Electrode CD Oscillator Driver DC Delay Circuit D _P , D _P ^* Pixel Data DPG Delay Pulse Generator DR Rotating Drum f _d Particle Frequency signal f _E , f _E ^* Encoder clock HVS High voltage switch LB Line buffer OSC oscillator PDC 1 pixel delay circuit PWM pulse width modulator RM Recording medium S _C , S _C ^* Charge control signal SE Shaft encoder

Claims (5)

[Claims] 1. A particle generation frequency signal generating means for outputting a particle formation frequency signal, particle formation means for dividing an ink jet into a series of ink particle rows in synchronization with the particle formation frequency signal, and pixel data to be recorded. Storage means for storing, charging means for charging the ink particles with a charging control signal according to the pixel data from the storage means, deflection means for deflecting the ink particles charged by the charging means, A continuous jet type ink jet recording apparatus, comprising: a delay unit that delays a charging control signal input to the charging unit according to pixel data. 2. A particle generation frequency signal generation means for outputting a particle formation frequency signal, a particle formation means for dividing an ink jet into a series of ink particle rows in synchronization with the particle formation frequency signal, and pixel data to be recorded. Storage means for storing, pulse width modulation means for modulating the pixel data from the storage means into a charge control signal having a pulse width corresponding to the value, and ink with the charge control signal pulse width modulated by the pulse width modulation means Charging means for charging the particles, deflecting means for deflecting the ink particles charged by the charging means, and delay means for delaying the charging control signal input to the charging means in accordance with the pixel data from the storage means A continuous-jet ink jet recording apparatus comprising: 3. A lookup table for converting the pixel data from the storage means into pixel data for determining a delay time based on the value, and a dot recording clock according to the output of the lookup table. 3. The continuous jet type ink jet recording apparatus according to claim 1, further comprising a delay circuit for delaying. 4. The continuous jet type inkjet according to claim 1, wherein the delay unit creates a delay time that is an integral multiple of the cycle of the particle frequency signal based on the pixel data from the storage unit. Recording device. 5. The continuous jet according to claim 1, wherein the delay means determines the delay time based on the pixel data to be recorded and the pixel data of one pixel or a plurality of pixels preceding the pixel data. Type inkjet recording device.