JPH07329317A - Continuous injection type ink jet recorder - Google Patents

Abstract

PURPOSE:To maintain an image density constant by eliminating the changer of a volume per one ink particle when the exciting frequency of a vibrator is altered. CONSTITUTION:A microprocessor MP so instructs as to output an exciting signal PCLK of the exciting frequency designated by a reference oscillator CG, and so instructs a pump controller 13 as to drive a stepping motor 8 according to a drive pulse rate proportional to the frequency. The signal PCLK output from the oscillator CG is applied to a vibrator 15 via a vibrator driver VD, thereby exciting a nozzle 6 by the frequency. When the controller 13 drives the motor 8 at the pulse rate, the discharge ink flow rate from the nozzle 6 becomes proportional to the frequency, and an ink particle to be divided from the signal to be applied to the nozzle 6 always becomes a constant volume. Accordingly, even if the frequency is regulated, an image density becomes constant.

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 in particular, in a continuous jet type ink jet recording apparatus, an exciting frequency (exciting signal frequency) of a vibrator mounted on a nozzle is variably adjusted, By adjusting the flow rate of the ink ejected from the printer in proportion to the excitation frequency, the generation of satellite particles (fine particles generated between the main particles) is controlled in an optimal state to improve the quality of the printed image and keep the image density constant. Regarding technology to keep in.

[0002]

2. Description of the Related Art In a conventional continuous jet type ink jet recording apparatus, as shown in FIG. 3, for example, an ink bottle 31 for containing ink, an ink pump 32 for pressurizing and delivering ink, and an ink tube 33 for supplying ink. And a nozzle 34 having an extra-fine diameter circular orifice, and a nozzle 34
Ink electrode 35 for setting the potential of the ink inside to the ground level
An image having a vibrator 36 formed of a piezo vibrator attached to the nozzle 34, a vibrator driving oscillator 37 for giving an excitation signal to the vibrator 36, and a circular opening or a slit-like opening concentric with the nozzle 34. A control electrode 38 to which a charging signal for controlling the charging of the inkjet corresponding to the data is applied.
A ground electrode 39 which is grounded and arranged in front of the control electrode 38, and a knife edge 40 which is attached to the ground electrode 39.
And high-voltage DC power supply for deflection (hereinafter, simply referred to as deflection power supply)
41 and the deflection power source 41 are connected to the ground electrode 39, a strong electric field orthogonal to the inkjet flight axis is created between the deflection electrode 41 and the ground electrode 39 to deflect the charged ink particles to the ground electrode 39 side.
It was equipped with and. The reference numeral 43 indicates a rotary drum around which the recording medium is wound.

In such a conventional continuous jet type ink jet recording apparatus, the ink pressurized by the ink pump 32 is guided to the nozzle 34 through the ink tube 33, the ink jet is formed from the orifice, and the jet diameter,
It splits into a row of ink particles at a spontaneous particle formation frequency that depends on the flow velocity and the physical properties of the ink. At this time, if the excitation frequency of the vibrator 36 attached to the nozzle 34 is set near the spontaneous particle generation frequency, the particle formation is synchronized with the excitation of the vibrator 36, and the ink particles of extremely uniform size coincide with the excitation frequency. Occurs.

When a uniform ink particle array split from an ink column is charge-modulated by a charging signal (recording pulse) corresponding to the density of an image and having a phase synchronized with an excitation signal, the charged ink particles are grounded by the action of a deflection electric field. It is deflected to the electrode 39 side and cut by the knife edge 40, and only the non-charged ink particles go straight and pass through the knife edge 40 to form dots on the recording medium wound around the rotary drum 43. As a result, an image is printed on the recording medium in accordance with the rotation of the rotary drum 43 and the movement of the carrier (not shown) mounting the nozzles 34 in the rotary drum axial direction.

By the way, in the continuous jet type ink jet recording apparatus, when the ink jet is divided into ink particles from the ink column, satellite particles may be generated between the main particles due to the non-linearity of the surface deformation. There are three satellite particle generation modes: a mode in which the generated satellite particles are combined with the subsequent main particles, a mode in which the satellite particles are combined with the preceding main particles, and a mode in which the satellite particles are not combined until the recording surface is reached. The mode in which satellite particles do not occur is the most desirable, but it does not cause any particular problem if they coalesce immediately after they occur. Satellite particles that do not coalesce immediately
The quality of the printed image is degraded for the following reasons.

(1) When the charged satellite particles coalesce with the non-charged main particles, the non-charged main particles (recording particles) are slightly charged and deflected. As a result, the recording dots are misaligned or cut by the knife edge 40. In this case, missing recording dots occur.

(2) When the uncharged satellite particles are united with the charged main particles (non-recording particles), the specific charge of the charged main particles becomes small contrary to (1), and as a result, the deflection amount decreases. As a result, when the charged main particles pass through the knife edge 40, the charged main particles are recorded on the recording medium, which causes image noise.

(3) If the uncharged main particles and the uncharged satellite particles are not united until they are recorded, the uncharged satellite particles are recorded on the recording medium to form a ghost image.

Therefore, the inventor of the present application can variably adjust the excitation frequency of the vibrator attached to the nozzle in order to control the generation of satellite particles to the optimum state for the image quality and enable high image quality printing. A continuous jet type ink jet recording apparatus as described above has already been proposed (JP-A-4-220).
No. 350).

[0010]

However, in the above-mentioned conventional continuous jet type ink jet recording apparatus, the flow rate of the ink ejected from the nozzle is not changed even if the excitation frequency of the vibrator is changed. When the excitation frequency of the vibrator changes, the volume per ink particle that splits from the ink column also changes, and the image density of the printed image also changes.

In view of the above points, an object of the present invention is to change the flow rate of ink ejected from the nozzles in proportion to the change of the excitation frequency of the vibrator to change the volume per ink particle. It is an object of the present invention to provide a continuous jet type ink jet recording apparatus in which the image density of a printed image is kept constant by preventing the change of the value.

Another object of the present invention is, in a continuous jet type ink jet recording apparatus capable of color printing, in which a plurality of nozzles are mounted, when the excitation frequency of the vibrator is changed in common for each nozzle, it is proportional to this. By changing the flow rate of ink ejected from the nozzles so that the volume per ink particle does not change, continuous ejection is performed so that the image density of the printed image is kept constant without disturbing the color balance. Type inkjet recording apparatus.

[0013]

SUMMARY OF THE INVENTION A continuous jet type ink jet recording apparatus of the present invention comprises an ink jet forming means having nozzles for introducing ink pressurized by an ink pump to generate uniform ink particles, and the nozzles. Excitation signal generating means that excites the oscillator mounted on the device and generates an excitation signal to be applied to the oscillator in order to generate ink particles in synchronization with the excitation, and the charge of the ink particles generated from the nozzle is converted into image data. A charging control unit that controls with a corresponding charging signal and an excitation frequency of the vibrator can be variably adjusted, and the ink pump is proportional to the excitation frequency of the vibrator when the excitation frequency of the vibrator is changed. Control means for changing the flow rate of the ink ejected from the nozzle.

Further, the continuous jet type ink jet recording apparatus of the present invention is a continuous jet type ink jet recording apparatus which is equipped with a plurality of nozzles and is capable of color printing. Inkjet forming means having a plurality of nozzles for generating particles, and an excitation for generating a plurality of excitation signals to be applied to each oscillator to excite the oscillator attached to each nozzle and generate ink particles in synchronization with the excitation A signal generating unit, a charging control unit that controls the charging of the ink particles generated by the plurality of nozzles with a plurality of charging signals corresponding to independent image data, and a vibration frequency of the vibrator common to a plurality of vibrators. Can be variably adjusted, and when the excitation frequency of the vibrator is changed, each ink pump is proportional to the excitation frequency of the vibrator. And having a control means for varying the ejection ink flow rate of each nozzle that.

[0015]

In the continuous jet type ink jet recording apparatus of the present invention, when the exciting frequency of the vibrator mounted on the nozzle is variably adjusted, the control means causes the ink ejected from the nozzle by the ink pump to be proportional to the exciting frequency of the vibrator. Change the flow rate. As a result, the volume per ink particle does not change, and the image density is kept constant.

Further, in the continuous jet type ink jet recording apparatus of the present invention, in the continuous jet type ink jet recording apparatus having a plurality of nozzles and capable of color printing, when the excitation frequency of the vibrator is variably adjusted for each nozzle,
The control means changes the flow rate of ink ejected from each nozzle by each ink pump in proportion to the excitation frequency of the vibrator. As a result, the volume per ink particle does not change, and the image density is kept constant without disturbing the color balance.

[0017]

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

FIG. 1 is a block diagram showing the essential parts of a continuous jet type ink jet recording apparatus according to the first embodiment of the present invention. The continuous jet type inkjet recording apparatus of the present embodiment is
An ink bottle 1 that contains ink, a cylinder 2 that sucks ink from the ink bottle 1, a piston 3 that reciprocates in the cylinder 2, and a solenoid valve 4 that opens and closes the ink bottle 1 and the cylinder 2 in a freely openable and closable manner. Ink tube 5 for supplying ink and cylinder 2 through ink tube 5
A nozzle 6 having an extremely small diameter circular orifice in communication with the pressure sensor 7, a pressure sensor 7 for measuring the pressure in the cylinder 2, and a stepping motor 8 for reciprocating the piston 3 in the cylinder 2.
And a gear A connected to the output shaft of the stepping motor 8.
9, a gear B10 that meshes with and interlocks with the gear A9, and a female screw 11 that is coaxially coupled to the gear B10 and rotates integrally.
A male screw 12 which is coupled to the piston 3 and meshes with the female screw 11 to reciprocate the piston 3 by the rotation of the female screw 11, a microprocessor MP which is a central processing unit of the continuous jet type ink jet recording apparatus, and a command from the microprocessor MP. And the output of the pressure sensor 7 to control the opening / closing of the solenoid valve 4 and the rotation of the stepping motor 8; the ink electrode 14 for setting the potential of the ink in the nozzle 6 to the ground level; A vibrator 15 that is a mounted piezoelectric vibrator, and a control electrode 16 that has a circular opening or a slit-shaped opening that is concentric with the nozzle 6 and that is applied with a charging signal that controls the charging of the inkjet corresponding to image data. , A ground electrode 17 which is grounded and arranged in front of the control electrode 16, and a knife electrode mounted on the ground electrode 17. A deflection power source E1 and a deflection electrode 19 for connecting the deflection power source E1 and a ground electrode 17 to create a strong electric field orthogonal to the inkjet flight axis and deflecting the charged ink particles to the ground electrode 17 side. A rotary drum 20 around which a recording medium is wound, a drum motor 21 that rotationally drives the rotary drum 20, a shaft encoder 22 that is coupled to the shaft of the rotary drum 20 to generate a pixel recording command signal DCLK, and an excitation commanded by the microprocessor MP. Reference oscillator C for generating frequency excitation signal PCLK
G, the excitation signal PCLK of the excitation frequency, and the pixel recording command signal DCLK generated by the shaft encoder 22 are input, and the drum motor 21 (that is, rotation) by the digital DC servo method (see Japanese Patent Laid-Open No. 4-158048 by the present inventor). The motor control circuit MC for controlling the rotation of the drum 20) and the oscillator 1 by the excitation signal PCLK of the excitation frequency.
5, a vibrator driver VD for driving the pulse width modulator 5, a pulse width modulator PM for converting the image data into a pulse width corresponding to the density gradation in synchronization with the pixel recording command signal DCLK, and the rise of the output of the pulse width modulator PM. A synchronizing circuit SC that synchronizes the falling edge with the rising or falling edge of the excitation signal PCLK, and a high-voltage switch H that amplifies the output of the synchronizing circuit SC and applies it as a charging signal to the control electrode 16.
The main part is composed of VS. The piston 3 is provided with a rotation prevention mechanism (not shown).

Next, the operation of the continuous jet type ink jet recording apparatus of the first embodiment thus constructed will be described.

When the start of the printing operation is instructed while the excitation frequency is specified, the microprocessor MP
Command the reference oscillator CG to generate an excitation signal PCLK of a specified excitation frequency.

The reference oscillator CG is a microprocessor M.
An excitation signal PCLK having an excitation frequency is output in response to a command from P. Excitation signal PCLK output from the reference oscillator CG
Are input to the motor control circuit MC, the oscillator driver VD, and the synchronization circuit SC, respectively.

The motor control circuit MC supplies a command clock obtained by dividing the excitation signal PCLK of the excitation frequency to the drum motor 2
1 to rotate the rotary drum 20 and input the pixel recording command signal DCLK from the shaft encoder 22 so that the drum motor 21 is driven by the digital DC servo system.
Start up so that the rotation of is the constant rotation speed required for recording.

The oscillator driver VD applies the excitation signal PCLK having the excitation frequency to the oscillator 15 to excite the nozzle 6.

Further, the microprocessor MP causes the stepping motor 8 to operate at a drive pulse rate such that the volume of the ink particles becomes a prescribed value (constant value) with respect to the excitation signal PCLK having the designated excitation frequency. To the pump control device 13.

That is, when the drive pulse rate is f _P and the ink flow rate ejected from the nozzle 6 is Q, the equation (1) is established. Q = K ₁ · f _P (1)

Here, K ₁ is a constant determined by the step angle of the stepping motor 8, the tooth number ratio between the gear A9 and the gear B10, the pitch of the female screw 11 and the male screw 12, and the sectional area of the piston 3.

On the other hand, when the excitation frequency is f _S and the volume of the ink particles is V _d (constant), the equation (2) is established. Q = f _S · V _d (2)

Therefore, from the equations (1) and (2), the equation (3) can be obtained by setting V _d / K ₁ = K. f _P = K · f _S (3)

Since K is a constant, the stepping motor 8 may be operated at a drive pulse rate f _P proportional to the excitation frequency f _S in order to keep the volume V _{d of the} ink particles constant. become. Microprocessor MP
Issues such a command to the pump control device 13.

Then, the pump control device 13 causes the solenoid valve 4
To drive the stepping motor 8 Pulse rate f _P
Drive with.

When the stepping motor 8 is driven at the drive pulse rate f _P , the gear A9, the gear B10 and the female screw 11 rotate, and the male screw 12 moves in the axial direction, whereby the piston 3 is proportional to the excitation frequency f _S. The ink enters the cylinder 2 at a constant speed, ink is supplied into the nozzle 6 through the ink tube 5, and an ink column is ejected from the tip orifice. At this time, the vibrator 15 is installed in the nozzle 6.
Since the excitation at the excitation frequency f _S is applied by, the ink column is divided into ink particles in synchronization with the excitation frequency f _S. The ink flow rate Q discharged from the nozzle 6 is proportional to the excitation frequency f _S, it is needless to say that the volume V _d of the ink particles divide at the excitation frequency f _S is constant.

On the other hand, the image data is sent to the pulse width modulator PM in synchronization with the pixel recording command signal DCLK produced from the output of the shaft encoder 22 directly connected to the rotary drum 20, and the image data corresponds to the density gradation. Is converted into a pulse width (the pulse width of the excitation signal PCLK is a reference) to be sent to the synchronizing circuit SC.

The synchronizing circuit SC detects the rising or falling edge of the output of the pulse width modulator PM from the reference oscillator CG.
The high-voltage switch HVS is synchronized with (matched with) the rising or falling edge of the excitation signal PCLK input from the.

The high-voltage switch HVS voltage-amplifies the output of the synchronization circuit SC to a potential necessary for charging the ink jet and applies it to the control electrode 16 as a charging signal.

The ink particles of a fixed volume V _d discharged from the nozzle 6 and divided are inductively charged by the control electrode 16 according to a charging signal, and the charged ink particles are formed between the deflection electrode 19 and the ground electrode 17. The non-charged ink particles are attracted to the ground electrode 17 by the generated electric field and cut by the knife edge 18, and the non-charged ink particles pass straight through the knife edge 18 and reach the recording medium on the rotating drum 20 to form dots. As a result, an image corresponding to the image data is printed on the recording medium according to the rotation of the rotary drum 20 and the movement of the carrier (not shown) mounting the nozzle 6 in the rotary drum axial direction.

If it is judged that the image of the desired image quality is not obtained by visually observing the printed image,
Adjust the excitation frequency and print again. It goes without saying that the image density of the reprinted image and the image density of the previously printed image do not change. By adjusting the excitation frequency and repeating the printing, it is possible to obtain an image of desired image quality.

FIG. 2 is a block diagram showing the essential parts of a continuous jet type ink jet recording apparatus according to the second embodiment of the present invention. The continuous jet type inkjet recording apparatus of the present embodiment is
A continuous jet type inkjet recording apparatus capable of color printing, which is equipped with a plurality of (four in the figure) nozzles 6,
The reference oscillator CG, the ground electrode 17, the knife edge 18, the deflection electrode 19, the deflection power source E1, the microprocessor MP, the motor control circuit MC, the pump control circuit 1 in the continuous jet type ink jet recording apparatus of the first embodiment shown in FIG.
Except for 3 etc., the four colors of C, M, Y and BK are configured independently. Therefore, the portions corresponding to those in the continuous jet type ink jet recording apparatus of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. It should be noted that the reason why the reference oscillators CG are not independent of four colors is that if the reference oscillators CG are also independent of four colors, the number of ink particles generated per unit time is different for each color, and the number of ink droplets on the recording medium is four. This is because, in the case of a continuous jet type inkjet recording apparatus capable of color printing by controlling the amount of ink adhered to colors, color balance is disturbed and other problems occur.

In the printing operation of the continuous jet type ink jet recording apparatus of the second embodiment thus constructed, the first operation is performed.
It goes without saying that a color image can be printed based on the image data for each color of C, M, Y, and BK, as in the case of printing by the printing operation of the continuous jet type ink jet recording apparatus of the embodiment. Therefore, when the excitation frequency of the vibrator 15 is adjusted for each nozzle, the flow rate of the ink ejected from each nozzle 6 changes in proportion to the excitation frequency, so that the volume per ink particle is always kept constant. Therefore, it is possible to perform color printing having a constant image density without disturbing the color balance.

[0039]

As described above, according to the present invention, when the excitation frequency of the vibrator is changed, the flow rate of the ink ejected from the nozzle is changed proportionally.
Even when the excitation frequency of the vibrator is adjusted so that the generation of satellite particles does not affect the image quality, there is an effect that the volume per ink particle is kept constant and a print image having a constant image density can be obtained.

Further, in a continuous jet type ink jet recording apparatus capable of color printing equipped with a plurality of nozzles, the flow rate of ink ejected from each nozzle is proportional when the excitation frequency of the vibrator is changed for each nozzle. By changing the excitation frequency of the vibrator so that the generation of satellite particles does not affect the image quality, the volume per ink particle is kept constant and the color balance is not disturbed. There is an effect that a color print image having a constant image density can be obtained.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a main part of a continuous jet type ink jet recording apparatus according to a second embodiment of the invention.

FIG. 3 is a configuration diagram showing a main part of a conventional continuous jet type ink jet recording apparatus.

[Explanation of symbols]

 1 Ink Bottle 2 Cylinder 3 Piston 4 Solenoid Valve 5 Ink Tube 6 Nozzle 7 Pressure Sensor 8 Stepping Motor 9 Gear A 10 Gear B 11 Female Screw 12 Male Screw 13 Pump Control Device 14 Ink Electrode 15 Vibrator 16 Control Electrode 17 Grounding Electrode 18 Knife Edge 19 Deflection Electrode 20 Rotating Drum 21 Drum Motor 22 Shaft Encoder CG Reference Oscillator E1 Deflection Power Supply HVS High Voltage Switch MC Motor Control Circuit MP Microprocessor PCLK Excitation Signal PM Pulse Width Modulator SC Synchronization Circuit VD Oscillator Driver

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41J 3/04 103 G

Claims (3)

[Claims] 1. An ink jet forming unit having a nozzle for guiding ink pressurized by an ink pump to generate uniform ink particles, and an oscillator mounted on the nozzle for exciting ink in synchronization with the excitation. Excitation signal generating means for generating an excitation signal to be applied to the vibrator to generate particles, charging control means for controlling charging of the ink particles generated by the nozzles with a charging signal corresponding to image data, and the vibrator The excitation frequency of can be adjusted variably,
Continuous ejection type inkjet recording, comprising: a control unit that changes the flow rate of ink discharged from the nozzle by the ink pump in proportion to the excitation frequency of the oscillator when the excitation frequency of the oscillator is changed. apparatus. 2. A continuous jet type ink jet recording apparatus which is equipped with a plurality of nozzles and is capable of color printing, and which is provided with a plurality of nozzles for guiding ink pressurized by an ink pump to generate uniform ink particles. Means, an excitation signal generating means for exciting a vibrator attached to each nozzle, and generating a plurality of excitation signals to be applied to each vibrator to generate ink particles in synchronism with the excitation; The charging control means for controlling the charging of the generated ink particles by a plurality of charging signals corresponding to independent image data respectively, and the exciting frequency of the vibrator can be variably adjusted commonly to a plurality of vibrators, and A control unit that changes the ink flow rate of ink discharged from each nozzle by each ink pump in proportion to the vibration frequency of the vibrator when the vibration frequency is changed. Continuous jet type ink jet recording apparatus characterized by having and. 3. The ink pump comprises a cylinder, a piston, and a piston drive mechanism including a stepping motor, and the control means changes a drive pulse rate of the stepping motor in proportion to an excitation frequency of the vibrator. The continuous jet type ink jet recording apparatus according to claim 1 or 2.