JPH03108548A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make a printing density adjustable by mounting a means for inputting a printing density, a means for variably controlling the oscillating frequency of an oscillator, and a means for modulating the pulse width of a printing signal according to the change in oscillating frequency of the oscillator. CONSTITUTION:A control part 14 consists of a CPU 15 controlling the drive of an oscillator 3 and a charged electrode 4 on a head part and controlling a whole device, an operation panel 16 selecting a density, a divider 17 dividing the oscillating frequency of an oscillator 12, AND circuits 18, 19 gating the output of the divider 17, shift registers 20, 21 outputting image data in synchronism with a clock signal inputted thereto, an inverter 22, an OR circuit 23, and a charged electrode drive circuit 24 for driving the charged electrode 4. In accordance with the input of a predetermined printing density, the oscillating frequency of the oscillator 3 is variably controlled, and the pulse width of a printing signal is modulated according to the change in the oscillating frequency of the oscillator 3. In this manner, printing density can be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inkjet recording device in which print density can be adjusted.

(Prior Art) FIG. 4 shows a cross-sectional view of the head section of a continuous inkjet recording apparatus. The head section 20 includes a nozzle 2° vibrator 3. Charged electrode4. It is composed of a deflection electrode 5 and a ground electrode 6. Here, the ink 8 pressurized by the pump 7 is ejected from the nozzle 2 and separated into ink drops 9 by surface tension, and is further charged and modulated by the potential between the charging electrode 4 and the ground electrode 6a on the nozzle 2 side. Ru. The charged ink drop 9 is deflected toward the ground electrode 6 (lower side in the figure) while flying between the deflection electrode 5 and the ground electrode 6, and is removed by suction. On the other hand, the non-charged ink drop 9 travels straight and reaches the recording paper 11 wound around the rotating drum 10, thereby performing recording.

On the other hand, an inkjet recording device capable of expressing gradation is disclosed in Japanese Patent Publication No. 83046/1983. This is 1
Dots are formed by a plurality of ink drops 9 (for example, about 20), and the number of ink drops forming one dot is variably controlled, thereby making it possible to control the dot diameter and expressing gradation. It is. The number of ink drops included in one dot is controlled by keeping the repetition frequency of the charging voltage constant so that the interval between recording dots is constant).
This is done by modulating the pulse width of the charging signal.
is installed, and by applying forced vibration near the spontaneous separation frequency of ink 8, the particle size and separation frequency are further stabilized, and the charging timing (edge of the pulse) is synchronized with the separation timing of ink 8. , which measures the binarization of the charged state of the ink drop 9.

Therefore, with this device, the size of the ink drop is uniform, an image with uniform pixels can be obtained, and furthermore, gradation can be expressed.

(Problems to be Solved by the Invention) However, there are cases in which it is inappropriate to simply record dots in a constant state on a recording paper in accordance with image data. That is, the density of the recorded dots changes depending on the type of recording paper, and the overall density may become inappropriate. Furthermore, when enlarging or reducing the image, data processing such as double printing or thinning is required in order to adjust the overall density.

(Means for Solving the Problems) Therefore, the present invention provides an inkjet recording apparatus having a nozzle equipped with a vibrator for stabilizing the separation frequency of ejected ink drops in order to adjust print density. an input means for inputting a predetermined print density;
A vibrator drive means for variably controlling the vibration frequency of the vibrator based on the output of the input means, and a pulse width modulation means for modulating the pulse width of the print signal in response to changes in the vibration frequency of the vibrator. It is characterized by

(Function) By variably controlling the vibration frequency of the vibrator by the output of the input means, the ink droplet ejected from the nozzle can be stabilized at an arbitrary separation frequency around the spontaneous separation frequency.

At this time, since the ink flow rate is constant, when the separation frequency changes, the size of the ink drop also changes in correlation. Furthermore, by modulating the pulse width of the print signal in response to changes in the vibration frequency of the vibrator, it is possible to synchronize the ink drop separation frequency and the print signal, that is, the timing of ink separation and the timing of charging. can.

(Example) As an example of the present invention, one dot has 16 gradations, that is,
Referring to the drawings, an inkjet recording device in which one dot is formed by 1 to 16 ink drops, the printing density is set to 10 dots/Il hazy, and the overall density can be changed in three stages. explain.

FIG. 1 is a configuration diagram of a control section of an inkjet recording apparatus according to the present invention. This control section I4 drives and controls the vibrator 3 and charging electrode 4 of the head section l (see FIG. 4) described in the prior art.

This includes a CPU 15 that performs overall control, an operation panel 16 that performs concentration selection, a frequency divider I7 that divides the oscillation frequency of the oscillator 12, and an AND circuit 1 that gates the output of the frequency divider I7.
8.19, shift register 20, which outputs image data in synchronization with the input clock signal; 211 inverter 22;
It is constituted by an OR circuit 23 and a charging electrode drive circuit 24 that drives the charging electrode 4 .

Oscillator I2 is IOM H! Outputs a signal with a frequency of

On the other hand, switches H, M, and L are provided on the operation panel I6. By selecting these switches H, M, and L,
The CPU 15 increases the frequency division number of the frequency divider I7 by +2 (H).
, 10 (M-), and 8 (L). At this time, the frequency ratio of the outputs of the oscillator 12 and the frequency divider 17, the frequency divider 1
Table 1 shows the relationship between the clock CLK of the output of No. 7, that is, the vibration frequency that drives the vibrator 3, and the generation time required for one ink drop.

Table 1 Here, the generation time of one ink drop is 1.2μ5
Since ec (when switch H is selected) is maximum, at least 1. ! x16-19.2
(μ5ec) of time is required. Therefore, printing is performed by switching the print signal for forming one dot every 20 μSee. Furthermore, the printing density at this time was increased to 10 dots/
The moving speed of the recording paper (peripheral speed of the drum) to make mm
is 5m1sec. FIG. 2 is a state diagram of ink drops ejected from the nozzles, and black circles indicate ink drops used for printing each gradation when switches H, M, and L are selected.

The ink drop separated by the vibrator 3 in synchronization with the clock CLK is charged as follows. Frequency divider 1
The clock CLK from 7 is input to AND circuits 18 and 19, respectively. On the other hand, the print signal from the CPU 15 is passed through the inverter 22 to the AND circuit 18, and
It is directly input to the D circuit I9. Therefore, when the print signal is Low, only the AND circuit 18, and when the print signal is High, only the AND circuit 19 opens the gates (AND circuits 18 and 19) and outputs the clock CLK. The CPU 15 also inputs image data (1 to 16 for forming one dot) into the shift register 20 and 21 alternately to form one dot.
number of ink drops) is given. That is, when the print signal becomes Lov, image data is output from the shift register 20 in synchronization with the clocks C1 and K, and during this time, the image data of the next dot is transferred to the shift register 21 from the CPU 1.
It is input from 5. Next, when the print signal becomes High, image data is output from the shift register 2I in synchronization with the clock CLK, and during this time, image data for the next dot is input from the CPU 15 to the shift register 20. The aforementioned image data, ie, shift register 20.2
The output of 1 is passed through an OR circuit 23 to a charged electrode drive circuit 24.
The charging electrode 4 is driven accordingly. In addition, the print signal H
Switching between high and low is performed every 20 μsec. Third
The figure is a schematic diagram showing the charging state that changes in synchronization with the ink drop, and shows the charging state for forming one dot with five uncharged ink drops. As shown in the figure, even if the ink drop separation frequency changes, the pulse width of the print signal is also modulated in correlation with this, so there is no need to change the image data even if the density is changed.

In addition, in the embodiment, concentration selection is performed using switches H, M,
Although there are three types of L, it is also possible to change the density by continuously changing the clock CLK by using a slide method for the switch.

Furthermore, when changing the resolution by changing the moving speed of the recording paper (rotational speed of the drum), the size of the dots can be changed according to the resolution.

Furthermore, even in an inkjet recording device in which one dot is composed of one ink drop, the density can be changed by making the change in the moving speed of the recording paper follow the change in the separation frequency of the ink drop. becomes.

(Effects of the Invention) As described above, in the apparatus of the present invention, a predetermined print density is input in an inkjet recording apparatus having a nozzle equipped with a vibrator for stabilizing the separation frequency of ejected ink drops. an input means, a vibrator drive means for variably controlling the vibration frequency of the vibrator based on the output of the input means, and a pulse width modulation means for modulating the pulse width of the print signal in response to changes in the vibration frequency of the vibrator. By providing this, the overall print density can be adjusted while accurately controlling the size and charging state of the ink drop.

[Brief explanation of drawings]

FIG. 1 shows control g1 of an inkjet recording apparatus according to the present invention.
2 is a state diagram of an ink drop ejected from a nozzle, FIG. 3 is a schematic diagram showing the charging state that changes in synchronization with the ink drop, and FIG. 4 is a head of a continuous inkjet recording device. FIG. 3... Vibrator, 4... Charged electrode, +2... Oscillator. 15...CPU, +6...Selection panel, 17...
・Frequency divider. +8/19...AND circuit, 20/21...shift register.

Claims (1)

[Scope of Claims] An inkjet recording device having a nozzle equipped with a vibrator for stabilizing the separation frequency of ejected ink drops, comprising: an input means for inputting a predetermined print density; and an output of the input means. A vibrator drive means for variably controlling the vibration frequency of the vibrator, and a pulse width modulation means for modulating the pulse width of the print signal in response to changes in the vibration frequency of the vibrator. Inkjet recording device.