JPS6249191B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic fluid recording device equipped with a print signal control circuit, and the present invention relates to a magnetic fluid recording device equipped with a print signal control circuit. A fluid recording device is provided.

FIG. 1 shows the configuration of the main parts of a conventionally proposed magnetic fluid recording device. In the example shown in the figure, magnetic ink 4 contained in an ink tank 5 is supplied to the tip of the needle electrode 2 through a supply path 3 made up of a magnet, thereby forming a bump due to magnetic force. A voltage pulse from a high voltage switching circuit 9 controlled by a needle electrode control circuit 10 is applied to the needle electrode 2, and the ink at the tip of the needle electrode 2 is charged. On the other hand, a voltage pulse from a high-voltage switching circuit 7 controlled by an image signal control circuit 8 is applied to the gate electrode 1, and charges are induced on the surface of the recording paper 6 that is in contact with the gate electrode 1.

When the Coulomb force generated by the charged ink at the tip of the needle electrode 2 and the electric charge induced on the surface of the recording paper 6 exceeds a certain value that depends on the distance between the ink and the paper surface, the ink begins to fly. It reaches the surface of the paper and a recorded image is formed.

FIG. 2 shows the relationship between the gate electrode 1 and the needle electrodes 2, in which 16 needle electrodes are arranged to face one gate electrode. Usually, matrix driving is performed to simplify the driving circuit.

While applying an image signal to the gate electrode 1, the needle electrode 2
When recording is performed by scanning sequentially, voltage pulses may be applied to the gate electrode 1 two or more times in succession. FIG. 3 shows a timing chart of the voltage pulses applied to gate electrode 1 and needle electrode 2. FIG. 15a, 16a, and 17a in FIG. 3A show the needle electrode voltage pulse waveform, gate electrode voltage pulse waveform, and recording paper surface voltage waveform, respectively, when the recording cycle is long. 15b, 16b, 17b in Figure 3B
show the needle electrode voltage waveform, gate electrode voltage pulse waveform, and recording paper surface voltage waveform, respectively, when the recording cycle is short. If the recording cycle is long, the voltage appearing on the surface of the recording paper 6 will be sufficiently discharged before the next voltage pulse is applied, and will have no effect on the next pulse.

However, as the recording speed increases and the voltage application cycle becomes shorter, the voltage response on the surface of the recording paper 6 is slow, so the next voltage pulse is not applied before the charge on the surface of the recording paper 6 is completely discharged. , charges are superimposed. Therefore, when voltage pulses are continuously applied to the same gate electrode 1 in this way, charges are accumulated on the surface of the recording paper 6, and the needle electrode 2
Bias voltage 1 even if no voltage pulse is applied to
3 and the surface potential of the recording paper 6 causes the ink to fly, which appears as half-selection noise. It has been experimentally confirmed that this noise becomes more significant as the recording speed increases and the pause period of the image signal becomes shorter.

The present invention has been made in view of the conventional problem that noise flying occurs due to the image signal pattern, and it is possible to achieve high speed by controlling the signal according to the image signal pattern. The present invention provides a magnetic fluid recording device with excellent printing quality.

An embodiment of the present invention will be described below based on the drawings.

One way to prevent the noise from flying around due to the accumulation of charge due to the succession of image signals mentioned above is to dynamically control the peak value of the gate electrode voltage pulse according to the pattern of the image signal. This is a method to keep the upper limit of the voltage appearing on the paper surface constant by combining with However, it is necessary to apply a high-voltage pulse signal of several hundred volts to the gate electrode, and it is difficult to dynamically control the peak value of such a high-voltage pulse, and it is not practical from the standpoint of circuit configuration. do not have. Therefore, in the present invention, we focused on the fact that the printing density and the on/off of ink flying depend on the energy of the signal pulse, that is, the product of the pulse height value and the pulse width, and by changing the pulse width while keeping the pulse height constant. It is characterized by dynamic control.

FIG. 4 shows an embodiment of a magnetic fluid recording device equipped with an image signal pulse width control circuit according to the present invention. The image signal pattern detection circuit 18 detects the continuity of the image signal based on the image signal pulse train output from the image signal control circuit 8, and detects the continuity of the image signal using the image signal pulse train outputted from the image signal control circuit 8.
A control signal is given to 9. In the pulse width control circuit 19, the voltage waveform 17b on the surface of the recording paper shown in FIG.
When the image signals are continuous, the high-voltage switching circuit 7 is configured to shorten the pulse width so that the energy applied in each cycle is almost equal, that is, to lengthen the pause period, so that the influence of the accumulated charge does not appear when the image signal is continuous. Controls the pulse width of the input image signal.

FIG. 5 shows a specific example of the image signal pattern detection circuit 18. In this configuration, a signal waveform equivalent to the change in voltage appearing on the surface of the recording paper is obtained by a combination of an integrating circuit consisting of R ₁ and C and a discharging circuit consisting of R ₂ and C. This is impedance-converted by the inverting amplifier 20 and is input to the pulse width control circuit 19.

It is assumed that the input signal 21 to the image signal pattern detection circuit 18 in FIG. 5 is a TTL level positive pulse. Therefore, as the image signal is continuously applied, the output of the inverting amplifier 20 becomes smaller. Therefore, if the pulse width control circuit 19 is configured to have a function like a voltage-pulse width conversion circuit, it becomes possible to reversely correct and absorb fluctuations in paper surface potential due to charge accumulation.

FIG. 6 shows an embodiment in which pulse width control is performed by a digital method. The TTL level image signal pulse train 21 is input as a clock to the counter 22. A signal obtained by NANDing the polarity of the image signal with the reference clock signal CK is applied to the clear input of the counter 22. A clear input to the counter is given when the image signal is turned off. Therefore counter 2
The output No. 2 is a count of the number of consecutive image signals. On the other hand, a plurality of mono/multi circuits 23a, 2 which are triggered by the image signal and output pulse signals having slightly different pulse widths from each other.
3b, 23c...... are prepared and the selection circuit 24
, one of the outputs is selected and ANDed with the image signal 21 to obtain the final image signal. The control signal to the selection circuit 24 is
2, and a pulse with an appropriate pulse width is dynamically selected in response to successive arrival of a predetermined number of image signals.

This method also makes it possible to correct fluctuations in potential on the paper surface due to charge accumulation.

Since the image signal pattern differs for each gate electrode, the image signal pattern detection circuit and pulse width control circuit described above must be provided for each gate electrode. Therefore, from a practical standpoint including cost, a simple control method that detects whether two or more image signals are consecutive and uniformly shortens the pulse width if two or more image signals are consecutive is recommended. Methods may be practical. This control method is, for example,
The continuity of the image signal is detected using a J-K flip-flop instead of a counter, and the selection circuit can also be a 2-1 selection circuit, so although it has a very simple circuit configuration, it is sufficiently effective in preventing noise. can get.

For recording devices, the occurrence of printing noise is a fatal defect, but as described above, according to the configuration of the present invention, by simply adding a simple signal control circuit, it is possible to eliminate printing noise from conventional devices. This technology solves the extremely serious problems of density unevenness and flying noise due to continuous image signal patterns, and makes it possible to realize a magnetic fluid recording device that is high-speed and has excellent print quality. be.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main parts of a conventional magnetic fluid recording device, Fig. 2 is an explanatory diagram showing the positional relationship between the needle electrode and the gate electrode, and Figs. Voltage waveform diagram of main parts when short,
FIG. 4 is a block diagram of main parts showing one embodiment of the present invention, FIG. 5 is a block diagram showing a specific example of the image signal pattern detection circuit of this embodiment, and FIG. 6 is a block diagram of another embodiment of the present invention. FIG. 1... Gate electrode, 2... Needle electrode, 7... High voltage switching circuit, 8... Image signal control circuit, 18
...Picture signal pattern detection circuit, 19...Pulse width control circuit.

Claims (1)

[Claims] 1. A needle electrode group in which a plurality of needle electrodes are arranged, a magnet that is provided close to the needle electrode group and makes the supplied magnetic ink rise at the tip of each needle electrode, and a recording paper for the needle electrode group. a group of gate electrodes facing each other via the needle electrode group, and matrix driving is performed by applying a pulsed signal voltage of opposite polarity to the needle electrode group and the gate electrode group, and an electric field between the needle electrode and the gate electrode facing each other is used. In a magnetic fluid recording device that forms an image on a recording paper by flying magnetic ink at the tip of a needle electrode, a pulse train of image signals given to each gate electrode is input, and when the image signal pulses are continuous, a correspondingly large ( If a continuous image signal is detected by an image signal pattern detection circuit that outputs an output signal (or a small) output signal, and an output signal of the image signal pattern detection circuit, the image signal is formed on the recording paper by the continuous image signal. What is claimed is: 1. A magnetic fluid recording device comprising: a pulse width control circuit that controls the pulse width of an image signal pattern to be shortened to compensate for the accumulation of charge caused by the magnetic flux.