JPS6154600B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a control system for an inkjet recording device,
More specifically, the present invention relates to a jet resuscitation device for an inkjet recording apparatus that prevents problems caused by ink drying.

In recent years, various attempts have been made to use non-contact type inkjet generating devices as recording means in place of so-called contact type recording tools such as hollow pens and ballpoint pens. There are various types of ink jet generators, one of which is to guide ink from an ink tank to a nozzle, apply a minute pressure to the ink to the extent that the ink creates a meniscus at the tip of the nozzle in a stationary state, There is an electric field ejection type inkjet generator that applies a high electric field between a conductive nozzle or ink and a counter electrode installed in front of the nozzle to draw ink out of the nozzle and eject it as a jet stream. . This type of inkjet generator has been put into practical use as a recording head for printers and other devices that direct finely divided ink particles onto a recording medium to form characters using a dot matrix, and has also been applied to facsimiles, XY plotters, etc. has also been attempted.

However, inkjet type recording devices, including inkjet type XY plotters,
Inkjet ink requires a certain degree of viscosity and quick drying properties, so it is recommended to use it when starting recording for the first time after the device is ready for operation, or when multiple recording heads are installed to change the print width or perform color recording. When switching the operating recording head when the recording head is in use, or even when a single recording head is used and no jet is ejected for a long period of time, the ink at the nozzle tip dries, which not only deteriorates the image immediately after recording starts, but also causes serious problems. There were problems such as the nozzle becoming clogged and making it impossible to spray.

The present invention has been made in order to eliminate the above-mentioned problems caused by drying of ink.The present invention sets a position where there is no recording medium (return position), and forcibly jets the jet at the return position before starting recording. The jet is resuscitated by removing the dried ink from the nozzle, and the forced jetting force is changed depending on the degree of dryness.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which embodiments of the invention are shown.

In FIG. 1 showing an XY plotter equipped with a jet resuscitation device according to the present invention, a pair of rails 2 and 3 are placed facing each other on the upper side of a main body 1, and one rail 2 has a rack. It is provided. The X-movement girder 4, which extends horizontally over the pair of rails 2 and 3, has both ends connected to the rails 2 and 3.
It is placed on support stands 5 and 6 that are slidable on top.
An X servo motor 7 is installed inside the support base 5, and drives a pinion (not shown) that engages with the rack of the rail 2 through an appropriate transmission mechanism, so as to move the X moving girder 4 in the X direction. be. X moving digit 4
A Y-direction rail 8 is placed on the support stands 5, 6 adjacent to and parallel to the Y-direction rail 8, and this Y-direction rail 8 is also provided with a rack. A slider 9 is slidably arranged on the Y-direction rail 8, and a Y servo motor 10 is installed inside the slider 9.
The servo motor has a pinion (not shown) that engages with the rack of the Y-direction rail 8 via an appropriate transmission mechanism.
is driven to move the mover in the lateral direction (Y direction). A recording head 12 equipped with an inkjet generating element 11 is installed on the moving element 9, and the recording head 12 is moved vertically and horizontally integrally with the moving element 9 by an XY servo mechanism as a movement control mechanism to be described later. The printer is configured to eject ink and perform line recording using a jet ejection control mechanism. A flexible pipe 13 for controlling air pressure and a cable 14 for voltage application are connected to the recording head 12, and these flexible pipe 13 and cable 14 are respectively connected to a compression pump and a voltage application device inside the main body 1. There is.

FIG. 2 shows a block diagram of the XY servo control mechanism. Normally, in an XY plotter, the position of the recording head 12 must be controlled extremely accurately, so a negative feedback system is used for position control. Further, the illustrated control mechanism shows an example in which the target position signal is a digital signal such as a pulse number, and an analog servo motor is used as the servo motor. In addition, XY servo control
Although the control is performed independently in each direction, since they are substantially the same, the X control system will be explained.

When a drawing signal S is output as an output of a computer (not shown) and inputted to the interface system 16 of the servo control mechanism, an X target position signal is output as a digital signal, and the comparator 1
7, the signal is compared with the X position signal, converted to an analog signal by a digital-to-analog converter (D/A converter) 18, and then amplified by an X servo amplifier 19. Rotate by the corresponding angle. At this time, the output of the X servo motor 7 is detected by the X speed detector 20 and the X position detector 22.
The signal from the speed detector 20 is fed back to the front stage of the X servo amplifier 19 via the X speed feedback amplifier 21. In addition, the output of the position detector 22 is an analog-to-digital converter (A/D converter).
After being converted into a digital signal at 23, the comparator 17
The position is controlled while being compared with the target position signal. In this case, the rotational speed is detected by a speedometer such as a tachogenerator attached to the servo motor shaft, and the position is detected by a resolver or the like.

Since the recording speed changes in the XY plotter, it is necessary to prevent the width of the image line recorded on the recording medium 15 from changing due to fluctuations in the recording speed.
Therefore, by utilizing the fact that the air pressure acting on the ink surface in the ink tank 24 of the ink jet generating element 11 and the amount of ejected ink are in a proportional relationship,
The pressure applied to the ink surface is controlled in accordance with the recording speed so that the width of the print line remains constant even if the recording speed changes. FIG. 3 shows the jet injection control mechanism including the pressure control mechanism.

An air compression system 28 is connected to the surface of the ink 25 in the ink tank 24 via the flexible pipe 13, and air pressure is applied to the tip of the nozzle 26 to form a meniscus, and this air pressure is applied to the interface. Pressure control signal V from system 30
is controlled in proportion to. The XY servo control mechanism includes a speed detector 2 such as a tachometer generator that detects the rotational speed of each of the XY servo motors 7 and 10.
9 and 29' are provided, and the respective output signals are inputted to the interface 30 of the pressure control mechanism as an X velocity signal Vx and a Y velocity signal Vy. Note that the speed detectors 29 and 29' are the speed detectors 20 and 29', respectively.
21 may be shared. The interface system 30 receives the speed signals Vx, Vy from the speed detectors 29, 29' and generates a pressure control signal v(=√
² + ² ) and sends it to the next stage comparator 31 only when the drawing command Sd is input. Comparator 3
1 is inputted with the pressure control signal v and a feedback signal that is detected by the pressure sensor 37 and amplified by the feedback amplifier 38, and the two are compared. and sends the error signal (comparison signal) to the controller 32. Controller 3
2 sets the window width ±V _R , and only when the absolute value of the error signal is larger than the window width, the signal CW is set.
Emit CCW. If the error signal is greater than +V _R , the signal CW is generated to activate the drive circuit 33 for driving the pulse motor 34, thereby causing the air compression system 28 to act in the direction of increasing the pressure, and the error signal increases. -V _R , a signal CCW is issued to the pulse motor drive circuit 33, thereby causing the air compression system 28 to act in the direction of lowering the pressure. This air compression system receives a signal CW from the controller 32,
It is comprised of a pulse motor drive circuit 33 that receives CCW, a pulse motor 34, a converter 35 that converts the rotational motion of the pulse motor 34 into linear motion, and an air compressor 36. interface system 30
Also, only when there is a drawing command signal Sd, the high voltage pulse generator of the high electric field generator 64 consisting of the high voltage bias power supply 39 and the high voltage pulse generator 40 connected between the nozzle 26 and the annular counter electrode 27 is activated. 40 and inject the jet. still,
The high voltage bias power supply 39 is constantly applied and contributes to the formation of a meniscus at the nozzle tip. FIG. 4 shows the operation timing of the XY plotter. Between _t1 and _t2 , the recording head 12 is only moving and no recording is performed. That is, the X, Y speed signal v
_x , v _y are output, but the drawing command signal Sd is not output, so the pressure Pa acting on the ink surface and the applied voltage V _J
Neither is applied and no recording is made. Time t ₂ ~ _{t 3}
between time t 4 and t 5 only in the X direction, and between time t ₄ and _{t 5} in the Y direction
This is a case where recording is performed according to the drawing command signal Sd while moving only in the direction (in the case of the figure, moving at the same speed in the X direction and Y direction), and the time t ₆ to _{t 7}
If you are moving in the XY direction at the same time,
Since the speed of the recording head is faster than in the case of t ₂ to t ₃ and t ₄ to t ₅ , the pressure control signal v is also large, and therefore a large pressure is applied to the ink surface, increasing the amount of ink ejected and recording. Despite the high speed, the image line width on the recording medium remains constant.

According to the invention, the control device of the XY plotter is provided with a jet resuscitation device. In normal recording, as described above, the operation signal So, drawing command Sd, X speed signal _vx , and Y speed signal _vy are converted by the interface system 30 into a pressure control signal v and an ON-OFF control signal Ss These are controlled by the pressure control system 28 and high pressure pulse generator 40 as appropriate.
is added to operate the inkjet generating element 11.

A mechanism for reviving the jet by performing a test injection at the start of operation or when the jet has stopped for a certain period of time during operation is incorporated in the interface system 30, and is shown in FIG. 5a.
A block that generates a return signal Sr to move the recording head to the return position, a signal to perform a test injection when the recording head reaches the return position, and a signal to notify that the test injection has ended, as shown in Figure 5b. It is equipped with a block that emits a signal for this purpose.

In this embodiment, when the operation starts, when the operation command So enters the interface system 30 from the interface system 16 of the XY servo mechanism, the rising edge of this operation command So is detected by the differentiating circuit 41 and returned through the OR circuit 42. A command Sr is issued and this return signal is sent to the interface system 16. On the other hand, when the stop time of the jet is longer than a certain period of time, the pulse train that is the output of the clock pulse generator 43 remains in the state where it has passed through the AND circuit 44 in the presence of the operation command So, and the pulse train that is the output of the clock pulse generator 43 remains in the state where it has passed through the AND circuit 44 and the NOT circuit 45 , AND
Due to the action of the circuit 46, when there is no drawing command Sd, that is, when the jet stops, the counting circuit 4
7, and this counting circuit 47 is connected to the NOT circuit 45.
Since it is reset by the differentiating circuit 48 that differentiates the rise of the output of the drawing command Sd, the clock pulse train is counted from 1 in synchronization when the drawing command Sd is turned OFF, and is reset every time the drawing command Sd is turned ON. be done. The output of this counting circuit 47 is compared with a reference pulse number prepared in advance by a comparing circuit 49, and only when the counting circuit output becomes greater than the reference pulse number, the comparing circuit 49 outputs an output, and the output is sent to a differentiating circuit. 50 and is sent to the XY servo mechanism interface system 16 through the OR circuit 42 as a return command Sr.

Upon receiving the return command Sr, the XY servo control mechanism moves the recording head 12 to a position where there is no recording object, that is, to a preset return position, and upon completion of the movement, sends a return end command Se to the interface system 30. This return end command Se is sent to the test signal generator 51 shown in FIG.
3. Send to OR circuit 54 and differentiation circuit 55. The second gate drive circuit 53 drives the gate 5 while the test signal is present.
6 to the lower side in the figure, the test pressure signal generator 52
and the comparator 31 of the pressure control device 59 including the air compression system 28. This applies a test pressure to the ink surface. Preferably, the test pressure is set higher than the pressure determined by the normal pressure control signal v.

At the same time as the test pressure is applied, the OR circuit 54
An ON-OFF control signal Ss is applied to the high-pressure pulse generator 40 through the high-pressure pulse generator 40, causing the jet to be injected. The differentiation circuit 55 detects the fall of the test signal and sends it to the interface system 16 of the XY servo control device as a test injection end signal Sj. Note that the first gate drive circuit 57 biases the first gate 58 upward in the figure only when there is a drawing command Sd, and allows the pressure control signal v to pass. During normal recording, the pressure control signal v is applied to the first gate 58 and the second gate 56.
The plotting command Sd passes through the OR circuit 54 and is directed to the high-voltage pulse generator 40 as an ON-OFF control signal.

The above embodiment is adapted to a case where a single jet generating element is installed, and at the start of operation and when the jet stop time exceeds a certain period of time, the recording head is moved to the return position and a test jet is performed to dry the ink. Since the recording operation starts after the removal, good recording is possible.

Figures 6 to 8 and Figure 5b show a second embodiment, which is equipped with a jet resuscitation mechanism when a plurality of jet generating elements are installed for changing the line width or for color recording. It shows a control device. Since the amount of ink to be ejected is approximately proportional to the nozzle size, that is, (inner diameter) ⁴ / length, the second embodiment utilizes this fact to mount three jet generating elements 11a, 11b, and 11c with different nozzle sizes. It is designed to allow recording with different line widths. In the case of color recording, the same effect can be achieved by installing recording heads for inks of different colors.

In FIG. 6, the jet generating element 11 used for recording is selected by an element selection signal Ses sent from an interface system 30. In FIG. The element selection signal Ses is a solenoid valve located between the air compression system 28 and the jet generating elements 11a, 11b, and 11c.
Solenoid valve selector 61 for selecting SW ₁ , SW ₂ , SW ₃
and the jet generating element selector 62 located between the high voltage pulse generator 40 and the nozzle 26 of the high voltage applying device 64. Note that the element selection signal Ses
uses the drawing type designation signal Sdd input from the XY servo control mechanism 60 to the interface 30.
For example, when there are three jet generating elements 11, the drawing type designation signal Sdd can be classified by a combination of two binary signals. In Figure 7, the object type designation signal
When Sdd is issued, that is, the replacement of the jet generating element 11 is completed, a return command Sr is issued through the OR circuit 63 and the differential circuit 41 shown in FIG. When the return command Sr is issued, the newly replaced jet generating element 11 is moved to the return position in the circuit shown in FIG. 5b and a test injection is performed. Since the image type designation signal Sdd is always output at the start of engine start, test injection at the start of engine start can also be performed using this circuit. Further, if the jet is stopped for a certain period of time or more, test injection is performed in the same manner as in FIGS. 5a and 5b.

FIG. 9 represents a third embodiment of the invention. In the third embodiment, if the jet in operation continues for a certain period of time after the recording head is operated, the problem caused by ink drying is slight, and since the number of times is relatively small, air pressure is not required. This method was developed based on the fact that the test jetting effect can be sufficiently obtained with voltage alone, and when the image type designation signal is output, air pressure and voltage are simultaneously applied and test jetting is performed to print the selected record. When the jet stops for a certain period of time while the head is in operation, only voltage is applied to perform a test injection.
That is, the test pressure signal generator 52 is configured to generate a test pressure signal only when the signal from the differentiating circuit 41 that detects a change in the image type designation signal Sdd is received, and the image type designation signal Sdd changes. When I got tired,
A return command Sr is issued through the OR circuit 63, the differentiation circuit 41, and the OR circuit 42, and at the same time, the output of the differentiation circuit 41 is applied to the test pressure signal generator 52, based on the test signal issued at the end of the return. A test pressure signal generator 52 applies a test pressure to the ink surface. At this time, a voltage is also applied at the same time. The return command Sr, which is issued when the jet stop time exceeds a certain level, is sent to the differentiator circuit 4.
Since the output from 1 is not combined, only the voltage is applied in this case. Note that this can also be applied to the first embodiment.

10 and 11 show a fourth embodiment of the invention. In the first to third embodiments, the applied voltage used for test ejection was the same as the voltage used during normal recording, but in the fourth embodiment, the voltage during test ejection was made even stronger to prevent ink clogging. This enhances the resuscitation effect of the jet that removes the That is, the high voltage application device 64 is configured by further connecting a test high voltage generator 65 in cascade to the high voltage pulse generator 40 (see FIG. 11b), and its operation is performed using the output of the test signal generator 51. It tightens it. FIG. 11a is the same as the second embodiment, and when the image type designation signal Sdd changes or when the jet stop time exceeds a certain time, a return command Sr is issued and the recording head 12 is moved to the return position. , and output a test signal using the return end signal Se. Air pressure and voltage are simultaneously applied using the test signal.The test signal is simultaneously applied to the high-voltage pulse generator 40 and the test high-voltage generator 65, and the voltage of the test high-voltage generator 65 is increased from the voltage during normal recording. The jet is injected by applying a voltage that is higher than that of the jet. It goes without saying that this can also be applied to the first and third embodiments.

As explained above, the present invention includes a recording head having a small diameter nozzle, a jet ejecting means for ejecting ink in a jet form by applying pressure and voltage to the ink in the recording head, and In an inkjet type recording apparatus that is equipped with a head moving mechanism that moves the head relative to the recording medium, and performs recording on the recording medium by controlling on/off jet ejection means while moving the recording head by the head movement mechanism, the operation of the recording head is means for outputting a first signal at the time of start; means for outputting a second signal when the off time during operation of the recording head exceeds a predetermined time; A means for outputting a return signal to the head moving mechanism for returning to the return position without the body, and a means for performing a test injection by applying pressure and voltage if the first signal is output when the recording head reaches the return position. control the jet injection means so that
On the other hand, if the second signal is output, the test jetting control means controls the jet jetting means so as to perform test jetting by applying only voltage, and if ink jetting is stopped for a long time, At the start of operation of the recording head, test ejection is performed with a strong ejection force using voltage and pressure in response to the first signal, and the off time during the operation of the recording head, during which ink ejection is considered to be stopped for a relatively short period of time, is determined. When a predetermined time has elapsed, test ejection is performed using only voltage in response to the second signal, so test ejection can be performed appropriately depending on the degree of dryness of the ink, and ink is not wasted. It is possible to eliminate the harmful effects caused by ink drying. The first signal here is a signal output when the recording head starts operating, and the rising edge of the operation command So, the rising edge of the image type selection signal Sdd, and other signals can be used. The second signal is a signal that is output when the recording head starts operating but no ink is ejected for a predetermined time period, and in the embodiment, this is done by counting clock pulses, but other off-off signals are used. It may also be a time measurement.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an XY plotter according to the present invention;
Figure 2 is a block diagram of the servo control mechanism, Figure 3
Figure 4 is a block diagram of the pressure control mechanism, Figure 4 is a diagram showing the operation timing of the XY plotter, and Figure 5a is a return signal generation circuit in the jet resuscitation mechanism that forms a signal to move the recording head to the return position. FIG. 5b is a block diagram of a test ejection signal generation circuit that generates a signal for test ejection at the return position, and FIG. 6 shows the main part of another embodiment equipped with a plurality of inkjet generation elements. 7 is a block diagram of its control mechanism, FIG. 8 is a block diagram of its return signal generation circuit, FIG. 9 is a block diagram of a jet resuscitation mechanism showing another embodiment, and FIG. 10 is a block diagram of another embodiment. Figures 11a and 11b are block diagrams of the jet resuscitation mechanism. 1...Main body, 2, 3...Rail, 4...X moving girder, 5, 6...Support stand, 7...X servo motor,
8... Y direction rail, 9... Mover, 10... Y
Servo motor, 11, 11a, 11b, 11c...
... Inkjet generating element, 12 ... Recording head, 13 ... Flexible pipe, 15 ... Recording object,
16,30...interface system, 1
7, 17'... Comparator, 18, 18'... Digital-analog converter, 19, 19'... Servo amplifier, 20, 20'... Speed detector, 21, 21'...
...Velocity feedback amplifier, 22, 22'...Position detector, 23, 23'...Analog-digital converter, 24...Ink tank, 26...Nozzle, 2
7... Opposed annular electrode, 28... Air compression system, 31
... Comparator, 32 ... Controller, 33 ... Pulse motor drive circuit, 34 ... Pulse motor, 35 ...
converter, 36... air compressor, 37... pressure sensor, 38... feedback amplifier, 39... high voltage bias power supply, 40... high voltage pulse generator, 41, 48,
50, 55... Differential circuit, 42, 54, 63...
OR circuit, 43...Clock pulse generator, 44, 46...AND circuit, 45...NOT circuit, 17...Counting circuit, 49...Comparison circuit, 51
... Test signal generator, 52 ... Test pressure signal generator, 53, 57 ... Gate drive circuit, 56,
58...gate, 59...pressure control device, 60...
... Servo control mechanism, 61 ... Solenoid valve selector, 6
2... Jet generating element selector, 64... Voltage application device, 65... Test high voltage generator.

Claims (1)

[Scope of Claims] 1. A recording head having a small diameter nozzle, an ejecting means for ejecting ink in a jet form by applying pressure and voltage to the ink of the recording head, and a recording head that is directed onto a recording medium. In an inkjet type recording apparatus, the recording head is moved by the head movement mechanism and the jet ejecting means is controlled on/off to perform recording on the recording medium. means for outputting a signal; means for outputting a second signal when the off time during operation of the recording head exceeds a predetermined time; means for outputting a return signal to the head moving mechanism to return the recording head to the return position;
When the signal is output, the jet injection means is controlled so as to perform a test injection by applying pressure and voltage, and on the other hand, when the second signal is output, only voltage is applied to perform a test injection. A jet resuscitation device comprising: a test injection means for controlling a jet injection means, and performs a test injection according to the degree of dryness of a nozzle. 2. The jet resuscitation apparatus according to claim 1, wherein a plurality of said recording heads are provided, and said first signal is output every time a recording head to be used is changed. 3. The jet resuscitation device according to claim 1, wherein the voltage or pressure during test injection is set to provide a stronger injection force than during normal recording.