JPS6127193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet type line recording device, and more particularly to a line recording device such as an XY plotter that achieves high-speed broken line recording.

A line recording device such as an XY plotter is a recording device that records a specified line pattern on a recording medium by mounting a writing instrument on a recording head that moves while its position and speed are controlled by external signals such as computer output. be. Conventional drawing recording devices use hollow pens, ballpoint pens, etc. as writing instruments, and record by raising and lowering the writing instrument according to drawing commands. To explain further, in the case of solid line recording, as shown in Figure 1, the recording head is moved according to the speed curve shown in the figure, and when a drawing command is given, the writing instrument is lowered to record, and the up and down operations are This was done with the recording head stopped. In the case of broken line recording, there were two methods as shown in FIG. 2a and b. That is, in the method shown in FIG. 2a, recording is performed by bringing the writing instrument into contact with the recording medium and then moving it, similar to the solid line recording shown in FIG.
After stopping, the writing instrument is removed from the recording medium, and this is repeated intermittently, but in this case, the broken line segment is short, so the recording head must be slowed down before it reaches its maximum speed. However, the recording speed becomes very slow. Next, the method shown in Figure 2b is
The recording head is moved at maximum speed in the same way as when recording a solid line, and the writing instrument is moved up and down repeatedly during this time, but this method involves hitting the recording medium repeatedly with the writing instrument, so recording is done, so there is no wear and tear on the writing instrument. The line quality also deteriorates significantly.

As described above, in conventional image recording apparatuses, broken line recording has a significant drawback.

The present invention relates to broken line recording when inkjet technology is applied to a line recording device such as an XY plotter. Figure 3 shows an inkjet generator for an XY plotter.
Ink tank 3 having a nozzle 2 with a small diameter of about μ
, an annular counter electrode 4 arranged concentrically with the nozzle 2, and a pressure sensor 5 attached to the ink tank 3 to detect air pressure acting on the ink surface. The ink tank 3 is connected to a pneumatic control system by a flexible pipe 6, and the pneumatic control system sends a recording speed signal v and a pressure signal P obtained by amplifying the ink surface pressure measured by the pressure sensor by a return amplifier 7 to a comparator 8. The output is used to operate the compressor drive circuit 9, and the air compressor 10 adjusts the ink surface pressure to a pressure corresponding to the recording speed. In addition, a high voltage DC power supply 1 is connected between the nozzle 2 and the annular counter electrode 4.
1 is connected, and when there is a drawing command, a voltage is applied between the nozzle and the annular opposing electrode to eject ink. The recording head mounting section 1
is controlled by a recording head drive control system (not shown).
It moves in the XY directions with its position and speed controlled, and when there is a drawing command, air pressure corresponding to the recording speed is applied to the ink surface, and a voltage is applied between the nozzle annular opposing electrodes, so the recording speed is controlled. A corresponding amount of ink is ejected by the voltage and is formed into droplets by its surface tension, directed onto the recording medium 12 to form an image. It has been confirmed in experiments that the inkjet type XY plotter described above can successfully record high-quality, constant line width in the case of solid line recording, and its high speed and noiseless properties are attracting attention and there are hopes for its practical use. . Now, looking at the operation response time, as shown in Fig. 4, the time from applying the voltage until the jet injects is t = 1 to 3 msec, and the time from turning off the voltage until the jet stops is t'<
Very fast response time of 0.5msec. Calculating from this value, the voltage can theoretically be turned on and off several hundred times per second.
The dashed line can be recorded by In addition, in the conventional pen type, the limit is several tens of times/sec. In this way, high-speed broken line recording using an inkjet is expected, and an experiment using the apparatus shown in Figure 3 revealed that when recording while the recording head is moving at high speed, the ink is discharged by air pressure when the voltage is OFF. It has been found that a phenomenon occurs in which the liquid wraps around the nozzle or drips onto the recording medium. This seems to be because the jet injection follows at high speed, but the air pressure control cannot follow it sufficiently. Further, if the speed is set to a low speed, broken lines can be recorded, but the recording speed becomes very slow and becomes practically inconvenient. Next, the third
If you try to record a solid line by moving the recording head at high speed with the device shown in the figure without applying air pressure, that is, opening it to atmospheric pressure, the above problem does not appear this time, but the amount of ink corresponding to the high speed is not supplied. As a result, the drawing width becomes narrower.

The present invention has been made in view of these points, and it is an object of the present invention to provide a highly practical inkjet type line recording device that can perform broken line recording at high speed.

The present invention will be explained below with reference to the drawings. FIG. 5 is an overall view of an XY plotter as a specific example of an inkjet type line recording apparatus embodying the present invention. 14 is attached to the Y-direction moving table 15. The movement of the recording head 14 is carried out by an X servo motor 17 provided at one end of the X direction moving column 16 and a Y servo motor 18 provided within the Y direction moving table 15.
This is done by moving the rack and pinion on the X-direction rail 19 and the Y-direction rail 20, respectively. A flexible pipe for air pressure control and a voltage application cable are connected from the recording head 14 to an air compressor, a voltage application device, etc. inside the main body. The recording head 14 is equipped with a jet generating element for solid lines and a jet generating element for broken lines. The operation of this XY plotter is shown in a block diagram in FIG. When an external signal such as a computer output enters the recording head drive control system 21, the recording head drive control system 21 drives the X and Y servo motors in accordance with the external signal to draw a predetermined trajectory.
At this time, accurate control is performed using a return signal S _R from a speed detector and a position detector attached to the servo motor. Further, the recording head drive control system 21 sends an X-velocity signal V to the interface 22 of the next stage inkjet generator.
_X , Y - Send a speed signal V _y , a drawing command Sd, and a drawing type designation signal α that designates whether the line is a solid line or a broken line. In the case of solid line recording, the interface 22 is the selector 23
Then, the image type designation signal α is sent to the electromagnetic valve operation circuit 24, and the element to which voltage is applied is set as the solid line jet generating element 25, and the electromagnetic valve 26 is opened to connect the pneumatic control system 27 and the solid line jet generating element 25. Furthermore ^, when there is a drawing command Sd, a pressure control signal V=√ _{x 2} is obtained by vectorial addition of the X and _Y speed signals V
+V _y ² is sent to the air compression system 27, and the air compressor 2
8 to perform pressure control and send a voltage application signal S _v to the high-pressure pulse generator 29 to inject jet and draw on the recording medium 12. Next, in the case of broken line recording, the interface 22 operates the selector 23 according to the image type designation signal α, sets the element to which voltage is applied to the broken line jet generating element 30, and closes the electromagnetic valve using the electromagnetic valve operation circuit 24. As a result, the jet generating element 25 for solid lines is not air-controlled during recording of broken lines. Incidentally, the difference in the position of the jet generating elements for the solid line and the broken line may be corrected in advance by computer programming. Recording is performed by moving the recording head at a constant high speed, for example, at the maximum speed during solid line recording, and intermittently injecting a jet in response to a voltage application signal _Sv to perform broken line recording. The solid line jet generating element 25 and the air compression system 27 mounted on the recording head 14 are connected to the third
It is the same as described in the figure. The jet generating element 30 for the broken line has its ink surface open to atmospheric pressure, and its nozzle size is larger in diameter or shorter than that for the solid line. This is to make the drawing widths of the solid line and the broken line almost the same, and takes advantage of the relationship between the nozzle size and the amount of injected ink as shown in FIG. FIG. 7a shows the relationship between the amount of ejected ink and the inner diameter of the nozzle, scaled on a double-logarithmic graph, from which it was found that the amount of ink ejected is approximately proportional to the fourth power of the inner diameter. FIG. 7b shows the relationship between the amount of ejected ink and the nozzle length, and shows that the two are almost inversely proportional. Since the jet generating element 30 for broken lines in FIG. 6 has its ink surface open to atmospheric pressure and is moved at high speed, the nozzle size must be increased in diameter or length in order to have the same image width as the solid line. This increases the amount of ink ejected to the same amount as when recording solid lines. If you want to make the dashed line have a different drawing width from the solid line, you can use the above relationship to change the nozzle dimensions as appropriate.

FIG. 8 shows a second embodiment of the present invention, in which the jet generating element is a single solid and broken line jet generating element 3.
1, the air compressor 32 is equipped with a solenoid valve 26 that opens the ink surface to atmospheric pressure during broken line recording, and the solenoid valve operating circuit 24 is actuated by the image type designation signal α to perform broken line recording. Open when recording a solid line, and close when recording a solid line. Furthermore, the shortage of the amount of ink ejected due to the lack of pressure corresponding to high speed is compensated for by applying a higher voltage during broken line printing than during solid line printing. Its configuration is that a broken line step-down pulse generator 33 having an output voltage higher than that of the solid line high voltage pulse generator 29 is provided in parallel with the solid line high voltage pulse generator 29, and both are connected to a switch circuit 34 with an image type designation signal. α
It is to be switched when . Although the second embodiment is simple in structure, since the amount of ink to be ejected is adjusted by increasing the applied voltage, there are significant restrictions due to the ink. Since the conventional ink shown by P in FIG. 9 has a narrow range of variation in the amount of ink ejected within the usable voltage range, the amount of ejected ink cannot be said to be sufficient even if the maximum voltage is applied within the usable range. Therefore, if you want to obtain the same drawing width as a solid line, you must slow down the speed to some extent. However, as shown in FIG. 9Q, ink whose ejected ink amount varies widely with respect to voltage, for example,
If an ink containing SiO ₂ , Al ₂ O ₃ or the like dispersed therein is used to provide pseudo-viscosity, high-speed broken line recording can be performed as in the first embodiment.

As described above, the present invention enables high-speed broken line recording in an inkjet type line recording device, and when recording broken lines, the ink surface is opened to atmospheric pressure and the jet is ejected only by voltage. By changing the nozzle dimensions or increasing the applied voltage, the line width was made almost the same as that of a solid line, and a high-speed recording of hundreds of dots per second was achieved using the normal number of dots. be.

Note that in the present invention, a plurality of jet generating elements are mounted on the recording head in order to change the nozzle dimensions.
It does not depart from the spirit of the present invention to use other methods, for example, a method in which a needle-like rod is moved in and out of the nozzle to obtain the effect substantially similar to that of changing the nozzle size.

[Brief explanation of the drawing]

Figure 1 shows a solid line recording method using a conventional XY plotter, Figure 2 shows a broken line recording method using a conventional XY plotter, and Figure 3 shows a diagram showing a broken line recording method using a conventional XY plotter.
Figure 4 is a diagram showing the inkjet generation device for an XY plotter, Figure 4 is a diagram showing the start and stop of ink jetting, Figure 5 is a perspective view of an inkjet type
7 is a diagram showing the relationship between the amount of ink jetted and the nozzle dimensions, FIG. 8 is a block diagram of the main part of the second embodiment of the present invention, and FIG. It is a figure showing the difference by ink. 2... Nozzle, 3... Ink tank, 4... Annular counter electrode, 6... Flexible pipe, 10, 28, 3
2... Air compressor, 11... High voltage bias power supply, 12
...recording medium, 17...X servo motor, 18...Y
Servo motor, 21... Recording head drive control system, 2
2...Interface, 23...Selector, 24
... Solenoid valve operation circuit, 25... Jet generating element for solid line, 26... Solenoid valve, 27... Air compression system, 29... High pressure pulse generator, 30... Jet generating element for broken line, 31... Jet generating element for both solid line and broken line, 33
...High voltage pulse generator for broken line, 34...Switch circuit.

Claims (1)

[Claims] 1. An ink tank for storing ink, a nozzle for guiding the ink in the ink tank to the outside,
In the inkjet type image recording device, the inkjet type image recording device includes a counter electrode disposed close to the nozzle, and ink is ejected from the nozzle by applying a voltage between the nozzle and the counter electrode. means for controlling the air pressure acting on the ink surface in the ink tank in accordance with the recording speed; a broken line recording signal generating means; and a means for increasing the air pressure acting on the ink surface in the ink tank while the broken line recording signal is being generated. An inkjet type line recording device characterized by comprising a switching means for recording a line by opening it to atmospheric pressure. 2. The switching means includes a valve provided in a control system of the means for controlling the air pressure, and a switching means for switching the voltage applied between the nozzle and the opposing electrode between solid line recording and broken line recording. An inkjet type printer according to claim 1, wherein, when recording broken lines, the valve is opened to release the inside of the pneumatic control system to atmospheric pressure, and the applied voltage is made higher than when recording solid lines. Line recording device. 3 The switching means changes the voltage applied between the nozzle and the counter electrode between an ink tank whose pressure is controlled by the air pressure control means and an ink tank which is not subjected to air pressure control and is open to atmospheric pressure. An inkjet type image recording apparatus according to claim 1, further comprising switching means for applying an ink to either one of a tank and a tank. 4 The nozzle of the ink tank opened to the atmospheric pressure is connected to the nozzle of the tank that is controlled by air pressure.
An inkjet type image recording device according to claim 3, wherein the inner diameter is increased or the length thereof is decreased.