JPS5843034B2 - Ink particle deflection control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves ejecting ink subjected to ultrasonic vibration from a nozzle, selectively charging the ejected ink at a position where it separates into ink particles with a charging electrode, and deflecting the charged ink particles with an electrode. The present invention relates to an inkjet recording apparatus that deflects charged ink particles to collide with a recording paper, and particularly relates to a deflection control device for charged ink particles.

This type of inkjet recording device is already known (IMB Technical Disclos
ureBulletin, Vol, 16&, 12
Mayl 974, Japanese Patent Publication No. 47-43450, Japanese Patent Publication No. 46450-1987, etc.).

However, in this type of recording device, if the timing of the generation of ink particles and the application of the charging voltage (pulsed) to the charging electrode are misaligned, the amount of charge on the ink particles will not be as intended, and the printing on the recording paper will not be possible. Dots may be misaligned, causing disturbances in recorded images.

Therefore, in the past, for example,
As disclosed in Japanese Patent Laid-open No. 450 and Japanese Patent Application Laid-Open No. 50-60131, the timing of applying the charging voltage to the charging electrode is determined appropriately by searching for the appropriate charging phase of the ink particles. .

However, in this case, although it is detected whether the charge is appropriate, it is not detected whether the amount of deflection is appropriate, so even if the charging timing is correct, the amount of deflection is excessive. When there is a shortage, the image shrinks or expands, and since the recording paper is normally fed at a constant pitch or speed, the recorded image is also disturbed.

Generally, the amount of deflection of ink particles is expressed by the following equation (1).

However, K: constant determined by the deflection electrode Qj: Charge amount of ink particles mj: mass of ink particles Vd: Deflection voltage Sd: electrode spacing of deflection electrodes vj: Flying speed of ink particles It is.

As can be seen from Equation (1), the amount of deflection of ink particles depends on many factors. Therefore, it is not possible to know the amount of deflection by simply detecting the amount of charge. I can't do it.

For example, even if the above-mentioned K, Vd, and Sd are constant (they can be easily maintained constant), and even if Q can be controlled to an appropriate value by phase search, mj, Vj are the variable factors. exist.

In other words, the viscosity of the ink changes due to changes in the temperature of the ink liquid, resulting in changes in Vj and mj, and the properties of the ink are slightly different when the ink is not changed for a long time and immediately after changing the ink, so Vj and mj change. Change.

Therefore, it is desirable not only to search for an appropriate charge phase through phase search to set Qj to an optimal value, but also to detect the amount of deflection and determine the appropriate amount of deflection.

An object of the present invention is to provide a deflection amount control device that determines an appropriate amount of deflection of charged ink particles.

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, 1 is an ink tank, 2 is a filter, 3 is a pump, 4 is an accumulator, 5 is an ink jet nozzle, and 7 is an ink tank.
8 is a charging electrode, 8 is a charge detection electrode, 9 is a deflection electrode, 10 is a gutter, and 11 is a recording paper.

Ink in the ink tank 1 is sucked by a pump 3 through a filter 2 and enters an accumulator 4.

Gas is sealed in the accumulator 4, and this gas absorbs the pulsations in the ejection pressure of the ink 3, so that the nozzle 5
Ink is supplied at a constant pressure, and the ink is ejected from the nozzle 5.

A charging electrode 7 is disposed at a position where the ejected ink is separated into ink particles, and a charging voltage is applied to the charging electrode 7 in accordance with a printing signal in synchronization with the timing of formation of the ink particles.

The ink particles thus charged are deflected by the electric field of the deflection electrode 9 and collide with the recording paper 11, while the uncharged ink particles travel straight and are captured by the gutter 10.

Ink trapped within gutter 10 also reaches filter 2.

A constant deflection voltage is always applied to the deflection electrode 9 from a deflection voltage power source 12 .

An alternating current or pulsating current of a constant voltage and a constant frequency is applied to the ultrasonic transducer of the nozzle 5 from the amplifier 13, and as a result,
The ultrasonic vibrator of the nozzle 5 vibrates at that frequency, and the vibration is applied to the ink inside the nozzle.

This vibration causes the ink column to break at the charging electrode 7 portion, and the ink particles are removed at a speed (number/5ee) corresponding to the above-mentioned frequency.

The excitation reference wave is generated by the excitation signal generator 15 in synchronization with the clock pulse of the clock pulse oscillator 14.

The clock pulse is also applied to charge signal generation circuit 16 and search signal generation circuit 17.

The charge signal generation circuit 16 synchronizes with the clock pulse,
A charging pulse is generated in which the wave height increases or decreases in a stepwise manner and repeats this at a regular cycle for each predetermined pulse.

This stepwise change in wave height determines the printing position in the feeding direction of the recording paper (from top to bottom in FIG. 1, or vice versa: sub-scanning).

The nozzles 5 to gutter 10 are continuously driven to scan (main scan) from the back side of the page to the front side at a constant speed, and when they reach the end, they are returned to the starting end and are driven again in the main scan.

- The recording paper is fed by one line in the sub-scanning direction for each main scan.

The output pulse of the charge signal generation circuit 16 is applied to the phase setting circuit 19 via the switching circuit 18.

In the recording mode, the phase setting circuit 19 adjusts the phase of the charging pulse to the phase set in the phase search mode and supplies it to the charging control circuit 20. , a search pulse with a constant peak value is given to the phase setting circuit via the switching circuit 18), the phase of the search pulse is sequentially shifted until an appropriate charge detection signal is obtained from the charge detection circuit 21. When the charge detection signal appears, the phase is fixed at that time, and when the search command signal arrives, the charge control circuit 20 starts the phase search operation of the cycle. When there is a signal representing printing, a charging pulse is output to the amplifier 22, and when there is no image signal, the charging pulse is cut off and not supplied to the amplifier 22.

To summarize, in the recording mode, the switching circuit 18 applies a charging pulse to the phase setting circuit 19, the amount of deflection of ink droplets (in the sub-scanning direction) is determined by the peak value of the charging pulse, and the phase setting circuit 19 applies a charging pulse to the phase setting circuit 19. On the other hand, the phase of the charging pulse is adjusted to the charging voltage phase for most appropriately charging the ink droplets, and the charging control circuit 20 determines whether printing is to be performed or not.

In the phase search mode, the switching circuit 18 applies a search pulse to the phase setting circuit 19, and since the peak value of this pulse is constant, the amount of deflection of the ink particles is constant (provided that they are properly charged). The phase setting circuit 19 sequentially shifts the phase of the charging pulse until the charge detection circuit 21 issues an appropriate charge detection signal, and fixes the adjusted phase to the phase when the proper charge detection signal is issued.

The components and their operations described above have already been proposed.

Next, parts added based on the present invention will be explained.

62 and 63 are guard plates, and 6 is a detection electrode.

These guard plates 62, 63 and detection electrode 61 are
In this example, it is placed on the ink flight path toward the recording position with the largest set deflection amount.

An enlarged perspective view of the guard plates 62 and 63 and the detection electrode 61 is shown in FIG. 2a.

A slit 25 is formed between the guard plates 62 and 63, and the opening width of this slit 25 is such that it allows ink particles flying toward the set maximum deflection position on the recording paper to pass through, and also allows the ink particles to pass toward the set maximum deflection position on the recording paper. It is designed to be extremely narrow, allowing ink particles flying toward a deflection position within the allowable error range to pass through, while blocking ink particles with other deflection amounts.

That is, in the front view shown in FIG. 2b, the slit 25
The 0 width is the ink particle ■8 (solid line) flying on the reference trajectory and the ink particle IS that deviates from the reference trajectory by an allowable range.
The aperture width allows only a (dotted line) to pass through.

The guard plates 6□ and 63 are arranged in a direction perpendicular to the deflection direction, as shown in FIG. It is preferable to make it slightly inclined with respect to the direction HH.

In this way, the ink swings along the deflection direction D-D, but the ink that collides with the guard plate 6□ flows to the left along the slope (Fig. 2c), so that the ink particles pass through the slit 25. This will no longer interfere with your attempts.

Referring again to FIG.

The ink that collides with the detection electrode 6 □ and the guard plates 6 □ and 63 falls into the gutter 26 .

These detection electrodes 6, guard plates 62, 63, and gutter 24 are either placed at the recording start position as shown in FIG. 3b), or in a recording standby position as shown in FIG. 3b, or in a position that does not interfere with normal recording.

23 is an integrating circuit, and a field effect transistor 23
, a, operational amplifier 231b and integrating capacitor 2
3. It is composed of c.

The output of the integrating circuit 23□ is applied to the differential amplifier 28a of the deflection amount control circuit 28.

Charged ink particles collide with the detection electrode 6□, and the integration circuit 2
31c generates an analog voltage corresponding to the integral value of the detected cart quantity, and when this analog voltage level becomes higher than the reference value ■8, the output of the differential amplifier 28a becomes a high level "1", and at this rising point, the flip-flop 28b is reset.

Note that the Q output of the rlJ level (when set) of the flip-flop 28b opens the AND gate 28c and provides the output pulse of the frequency divider 28d to the counter 28e.

The count code of the counter 28e is applied to a digital-to-analog converter (hereinafter referred to as a D/A converter) 28f, and the D/A
The analog voltage from the converter 28f is applied to the deflection voltage control circuit 27.
is applied to the base of transistor 27a.

In the deflection amount control circuit 28, the reference signal generator 28 converts all the output pulses of the phase setting circuit 19 into pulses having a constant peak value corresponding to the maximum peak value.

The deflection voltage control circuit 27 includes a coil 27b wound around the core of the transformer 12a of the deflection voltage power supply circuit 12, diodes 27c1 and 27c2, a smoothing capacitor 27d, a Zener diode 27e, transistors 27a and 27f, a capacitor 27g, and a resistor. Ru.

In this case, the collector voltage of the transistor 27a is maintained constant by the Zener diode 27e, and when the base voltage of the transistor 27a increases to the positive side, the conductivity of the transistor 28a increases and the transistor 28a increases.
When the conductivity of 7f becomes low, the current value flowing through the coil 27b becomes small, and when the base voltage of the transistor 2γa becomes low, the conductivity of the transistor 27a becomes low, and the conductivity of the transistor 27f becomes high, and the current flowing through the coil 27b decreases. The value increases.

In the deflection voltage power supply circuit 12, when the current of the coil 27b, that is, the load current increases, the voltage drop due to the primary side resistor 12b increases, and the output voltage (that is, the deflection voltage) increases.
When the current in the coil 27b decreases, the output voltage increases.

In this way, increasing the base voltage of the transistor 27a increases the output voltage of the deflection voltage power supply circuit 12, and decreasing the base voltage decreases the output voltage.

It is now assumed that the phase search and phase setting have already been completed, and the phase setting circuit 19 has been adjusted to the optimal charging phase with respect to the timing of ink droplet generation.

In this state, the deflection control command pulse is transmitted to the deflection amount control circuit 28.
When applied to the set end S of the flip-flop 28b, its Q output becomes "1", and the reference signal generator 28g synchronizes with the charging pulse and generates a pulse with a constant peak value equal to the maximum peak value of the switching circuit. 28h, switching circuit 28
h gives this to the charge control circuit 20.

As a result, a charging pulse having a constant peak value whose level is controlled by the reference signal generator 28k is applied to the charging electrode 7 at the optimum charging timing, and charged ink particles fly in the direction of the guard plate 63.

However, since the current level 5228e is cleared when the flip-flop 28b is set, the output level of the D/A converter is low and the base bias of the transistor 27a is small, so the output of the deflection voltage power supply circuit 12 is Voltage value is low.

Therefore, the ink particles collide with the lower part of the guard plate 63.

Among them, the frequency divider 28d generates a pulse at a frequency division ratio of, for example, 1/612, that is, every time 612 ink particles are generated, the counter 28e counts this pulse, and the D/A converter 28f outputs a pulse. The output level gradually increases.

Correspondingly, the base bias of the transistor 27a gradually increases, and the output voltage value of the deflection voltage power supply circuit 12 gradually increases.

Accompanying this, the flight trajectory of the charged ink particles gradually rises.

When the charged ink particles finally pass through the slit 25 between the guard plates 62.6s, the output potential of the integrating circuit 23 rises rapidly, and the output of the differential amplifier 28a becomes "1".
, the flip-flop 28b is reset, and the AND gate 28c is turned off, and the counter 28
e stops counting up while outputting the count code at that point.

In this state, the deflection amount control circuit 27 and the phase setting circuit 19
When the highest wave height pulse (corresponding to the maximum amount of deflection) arrives, the amplification factor is set to appropriately charge the ink particles to pass through the slit 25 between the guard plates 62 and 63. .

Therefore, when the recording mode is subsequently set and a recording operation is started, recording is always performed with a predetermined deflection amount in which the maximum deflection position corresponds to the position of the slit 25.

Therefore, even though the amount of deflection changes depending on many parameters as shown in equation (1), the amount of deflection can always be adjusted stably using the charge amount detection device of the present invention.

In the embodiment shown in FIG. 4, the guard plates 6□ and 63 are also used as detection electrodes and are connected to the integrating circuits 232 and 2, respectively.
33 and connect these outputs as well as the detection electrodes 6,
The deflection voltage is controlled by the output of an integrating circuit 23 connected to the deflection voltage.

In this embodiment, the integrating circuits 23□ and 233 are 23□
It is said to have exactly the same configuration.

The deflection amount control circuit 28 includes flip-flops 28b and 2
8h, and Kate 28c, 28h.

28g, orgate 281,281. Up/down counter 28e, -number output circuit 28m, code generator 28n
, digital-to-analog converter 28f, switching circuit 28j,
It consists of a reference signal generator 28 and a frequency divider 28d.

The code generator 28n generates a count code corresponding to the reference deflection voltage of the deflection voltage power supply circuit 120. For example, an adjustable code generator (matrix circuit) consisting of a combination of a resistor, a diode, and a code setting switch is used. It will be done.

In other words, the code generator 28n is the deflection voltage power supply circuit 12
This specifies the initial setting voltage.

That is, the pulse representing power-on is applied to the deflection amount control circuit 2.
8, the flip-flop 28g is set and its Q output becomes "1", and the clock pulse (output of 14) is applied to the count pulse input terminal CK of the counter 28e through the AND gate 28h and the OR gate 28i. At the same time, the Q output "1" of the flip-flop 28g is sent to the counter 28 through the OR gate 281.
e as an up-count designation signal.

As a result, the counter 28e starts counting up.
When the count code becomes equal to the output code of the code generator 28n, the output of the coincidence detection circuit 28m becomes "1", and at this rising time, the flip-flop 28g is reset and its Q output becomes "0", and the AND 2
8h is turned off and the clock pulse to counter 28e is cut off.

In this way, when the power-on pulse arrives, the counter 28e is first cleared to zero, then counts up until it reaches the output code of the code generator 28n, and then stops.

Therefore, the D/A converter 28f is the code generator 28
An analog voltage corresponding to the code set to n is applied to the base of the transistor 27a of the deflection voltage control circuit 27.

Therefore, the phase search and setting described above are performed with the output voltage of the deflection voltage power supply circuit 12 set to the reference value (corresponding to the output code of the code generator 28n).

The coincidence detection circuit 28m is, for example, a combination of n exclusive NOR gates and one AND gate whose outputs are input, where the number of code digits is n.
Each exclusive output is a combination of signals of corresponding digits of the outputs of the counter 28e and code generator 28n.

When the pulse specifying the deflection amount control arrives, the flip-flop 28b is set, thereby changing its Q output to "
1”, Antogame) 28c and Orgame) 28
The output pulse of the frequency divider 28d passes through the counter 28e.
is applied to the count pulse input terminal of

The frequency divider 28d divides the frequency of the clock pulse into 17612, for example, and in this case, outputs one pulse every time 612 ink droplets are generated.

Since the phase search has already been completed by the time the deflection amount control designation pulse arrives, the ink droplets are charged, but the Q output of the flip-flop 28b is "1" and the switching circuit 28j
is the output pulse to the reference signal generator 28 to the charging control circuit 2
Give to 0.

This reference signal generator 28 is synchronized with the output charging pulses of the phase setting circuit 19, and among these pulses, a signal (
A pulse with a constant peak value that is equal to a pulse with a certain fixed peak value assigned to print an ink droplet at a certain pixel position in the sub-scanning direction on the recording paper is output.

Therefore, as originally designed and originally planned (1
) If ink is ejected under recording conditions that exactly match the conditions of the equation, all charged ink particles will fall onto the guard plates 6□, 6.
It should pass through the gap between 3 and 3.

When the charge actually passes, the charge detection electrode 6□ detects it, the output potential of the integrating circuit 23 rises, and the frequency divider 28
By the time d outputs one pulse, the differential amplifier 28a
1 becomes "1", and at the rising edge of the flip-flop 28
b is reset, the counter 28e neither counts up nor counts down, and its output code remains the same as the output code of the code generator 28n (deflection amount adjustment completed).

However, in general, the charged ink particles deviate from the predetermined trajectory and collide with the second or third charge detection electrodes 62, 63, and as a result, the differential amplifier 28a2 or 28a3 is The output of is "1", and a down-count command signal (when the output of 28a2 is "1") or an up-count command (when the output of 28a3 is "1") is given to the counter 28e. .

Therefore, when the frequency divider 28d outputs a pulse, the counter 28e counts down or counts up by one.

As a result, the output voltage of the D/A converter 28f decreases or increases by 1 step, and the output voltage of the deflection voltage power supply circuit 12 decreases by 1 step.
The step is changed.

This down-counting or up-counting operation continues until the output of the differential amplifier 28a1 becomes high level "1" and the flip-flop 28b is reset, that is, the charged ink particles pass through the gap between the guard plates 62 and 63. You can continue until you can do it.

When the flip-flop 28b is reset, the AND gate 28c is turned off, so that the count code of the counter 28e remains as it is at that time. Therefore, the output voltage of the deflection voltage power supply circuit 12 is kept at a constant value (the value that gives the desired amount of deflection). adjustment value), and the switching circuit 28j switches to a mode in which the output of the phase setting circuit 19 is given to the level adjustment circuit 27 (the deflection amount adjustment is completed).

As explained above, according to the present invention, there are many parameters that affect the amount of deflection as shown in equation (1), and even though the amount of deflection changes from time to time, it is possible to always perform optimal control of the amount of deflection. I can do it.

Note that in the above description, ink particles are transferred to the charged detection electrode 6.
1 and the guard plates 62 and 63, the ink particles may be detected by conventionally known ink particle detection means such as a photo sensor or a piezo element plate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2a shows a charge detection electrode and a guard plate 6. 63, FIG. 2b is an enlarged front view, FIG. 2c is an enlarged perspective view showing another arrangement thereof, FIGS. 3a and 3.
Figure b is a front view showing their arrangement. FIG. 4 is a block diagram showing another embodiment of the present invention. 1: Ink tank, 2: Filter, 3: Pump, 4: Accumulator, 5: Nozzle, 61: Charge detection electrode, 62.6
a: Guard plate, 7: Charged electrode, 8: Charged detection electrode, 9
: Deflection electrode, 10, 24 nigator 11: Recording paper, 12:
Deflection voltage power supply circuit, 23° to 233: Integral circuit, 25
27: Deflection voltage control circuit, 28: Deflection amount control circuit, 31 Nidram.

Claims (1)

[Scope of Claims] 1. A charge detection electrode disposed in the flight path of charged ink particles ejected from a nozzle, charged by a charge electrode, and deflected by a deflection electrode, and a charge detection electrode with a large amount of deflection toward the charge detection electrode. An ink comprising a guard plate that forms a narrow slit through which only charged ink particles having a specific amount of deflection among the particles can pass and prevents charged ink particles having other amounts of deflection from passing through, and an integrating circuit connected to a charge detection electrode. Particle deflection detection device; Deflection amount control means that generates a deflection voltage control signal and changes the deflection voltage control signal until a charged ink particle is detected by a charge detection electrode of the deflection detection device; and An ink particle deflection control device, comprising: voltage control means for determining a deflection voltage applied to an electrode. 2. If the charge detection electrode is called a first charge detection electrode, the guard plate allows only charged ink particles with a specific amount of deflection to pass through, out of the number of charged ink particles with many deflections toward the first charge detection electrode. second and third charge detection electrodes forming a narrow slit therebetween to prevent passage of charged ink particles of other deflection amounts; an integrating circuit is connected to the second and third charge detection electrodes; and an integrating circuit; the deflection amount control means is configured to lower the deflection voltage when the charged ink particles are colliding with the second charged detection electrode, based on the detection signal of the deflection detection device; When the charged ink particles collide with the third charged detection electrode, the deflection voltage control signal is changed to increase the deflection voltage, and the charged ink particles collide with the first charged detection electrode. 2. The ink droplet deflection control device according to claim 1, wherein the ink droplet deflection control device is configured to stop changing the deflection voltage control signal when the ink droplets collide with the ink droplets.