JPS591594B2 - Inkjet recording device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an inkjet recording device.

In the performance of an inkjet recording device, its stability is an important factor, and stability with respect to temperature in particular occupies a large factor.

This is mainly due to the physical characteristics of ink used in inkjet with respect to temperature and the characteristics of excitation efficiency with respect to nozzle temperature. In other words, due to these factors, the conditions for creating ink particles change due to temperature changes, resulting in a decrease in recording quality, unstable operation of the device, and problems such as contamination of device components with ink. Become. The solution to this problem is to develop an ink whose physical properties change little with respect to temperature, but at present it has not been possible to obtain satisfactory results. Another conventional technique involves temperature control to maintain a constant nozzle and ink temperature. There are two methods of temperature control: one is to control the temperature at a constant temperature in the middle of the environmental temperature range, and the other is to control the temperature at a constant temperature slightly above the upper limit of the environmental temperature.
All of them have the disadvantage that they require warm-up time to reach a certain temperature at startup, and that they require a temperature control device, making the devices large and expensive. Furthermore, if temperature control is performed at a point exceeding the upper limit of the environmental temperature range, only a heating device is required, so there is relatively little need to increase the size of the device, but the ink is easily kept at a high temperature, making it easy to dry This has the disadvantage of making the nozzle more likely to become clogged. SUMMARY OF THE INVENTION An object of the present invention is to provide an ic-jet recording device that is stable against environmental temperatures and can print with good recording quality.

According to the present invention, when the temperature of the nozzle and ink of an ic-jet recording device changes due to a change in the environmental temperature of the device,
The stability or print quality deteriorates, but we focused on the fact that by changing the excitation voltage of the nozzle, we can restore the stability or print quality.We detected a temperature equivalent to the nozzle or ink temperature, and By configuring the apparatus to apply an optimum excitation voltage when the temperature changes based on the detection results, an ic-jet recording apparatus that is stable with respect to temperature and has little deterioration in print quality is realized.

Figure 1 shows the relationship between temperature and recording characteristics. ○ marks indicate good recording, Δ marks indicate records with a lot of recording distortion, X marks indicate unstable recording conditions, and lines 1 and 2 indicate good recording conditions. indicates a range.

An embodiment of the present invention will be described in detail.

FIG. 2 shows the configuration of the IC jet recording apparatus. 1 is an ink supply source; 2 is a nozzle connected to the ink supply source, and pressurized ink is supplied from the ink supply source 1;

A small diameter hole for ink ejection is provided at the tip of the nozzle 2. A charging electrode 3 charges ink particles created by ink ejected from the small diameter hole at the tip of the nozzle 2.

Reference numeral 4 denotes a deflection electrode, which is composed of electrode plates 4a and 4b, between which ink particles pass.

A DC high voltage source 5 is connected to the deflection electrode plate 4a and forms a deflection electric field between the deflection electrode plates.

A recording paper 6 moves in a direction perpendicular to the deflection of ink particles during recording, and forms a two-dimensional image using ink particles 9a.

A trap 7 captures ink particles 9b that are not used for recording, and is collected and reused by a collection means (not shown).

An electrostrictive vibrator 8 is mechanically coupled to the nozzle 2 and vibrates the nozzle 2.

Ink droplets are created in synchronization with this vibration frequency. 9
Ink particles 9a are used for recording and ink particles 9b are not used for recording.

A thermistor 10 is installed near the nozzle and exhibits a temperature equivalent to that of the ink and the nozzle.

11 is a high frequency source, which is a rectangular wave basic signal clock (CLOK).
) occurs.

A waveform converter 12 converts a rectangular wave clock signal into a sine wave excitation signal.

An excitation amplifier 13 amplifies an excitation signal to an excitation voltage necessary for excitation of the nozzle.

A recording signal generator 14 generates a recording signal voltage according to recording information.

A recording signal amplifier 15 amplifies the recording signal to a recording voltage necessary for charging the ink particles.

In addition, an automatic phase matching device (not shown) is provided for determining the optimum timing for charging the ink particles, and the timing for generating recording signals is determined based on this automatic phase matching device. The operation of the above configuration will be explained.

Pressurized ink from ink supply source 1 is supplied to nozzle 2VC. The ink is sent and ejected from the small diameter hole at the tip of the nozzle 2, forming an ink column. Since the electrostrictive vibrator 8 is excited by the excitation amplifier 13 at the frequency of the high frequency source 11, the nozzle 2 and the ink within the nozzle 2 are vibrated in response to the excitation. The ink column formed at the tip of the nozzle 2 is periodically constricted by this vibration, and the amplitude of this constriction increases as it approaches the tip of the ink column due to the effect of the surface tension of the ink, and eventually it separates. and become ink particles. At this time, since a recording voltage synchronized with the excitation of the nozzle is applied to the charging electrode 3 placed near where the ink particles are generated, the generated ink particles are individually charged in accordance with this voltage. When the charged ink particles 9a pass between the deflection electrode plates 4a and 4b, they are deflected according to the amount of charge and reach the recording paper 6 to form an image. Since the ink particles 9b that are not used for recording are not charged, they go straight without being deflected, reach the trap 7, and are collected. If we pay attention to the excitation voltage and recording quality when recording is performed in this manner, as shown in FIG. 1, there is a range in which recording is good, a range in which a large amount of recording distortion occurs, and a range in which recording is unstable. A range in which recording is good indicates that ink particles are generated stably. Recording distortion refers to the deviation between the intended recording position and the position where ink particles reach.It is mainly caused by factors other than excitation voltage, but one of the reasons why this increases with excitation voltage is The shape of the ink particles is thought to be caused by the strength of the excitation, and the other factor is the effect of small-diameter particles that occur within a certain range of ink preparation conditions.

In some cases, these small particles are deflected so much that they adhere to and contaminate equipment components. To explain in more detail how ink particles are generated, the state of ink particle generation near a stable operating point and the amount of charge (deflection amount) can be broadly classified as follows. (1) Normal individual ink particles (large-diameter particles) are generated, their charge is normally controlled, and they are normally deflected.

(2) Along with the generation of large-diameter particles, small-diameter particles are generated, and these small-diameter particles are the tails of ink columns separated to form large-diameter particles, and are separated from the preceding large-diameter particles during flight. Coalesce (state of high-speed small-diameter particle generation).

Since the small-diameter particles are charged under the same electrostatic pressure conditions as the preceding large-diameter particles and coalesce during flight, recording distortion due to changes in the amount of charge hardly occurs. (3) Small-diameter particles are generated along with the generation of large-diameter particles, but these small-diameter particles are separated from the tip of the ink column, and coalesce with the following large-diameter particles during flight (low-speed small-diameter particle generation state). ).

Since these small-diameter particles are separated earlier than the following large-diameter particles, the electrostatic charge conditions are different and they are in an uncharged or undercharged state. When such small-diameter particles coalesce with the subsequent charged large-diameter particles, the large-diameter particles after the coalescence become insufficiently charged, and the amount of deflection decreases, resulting in recording distortion. (4) Small-diameter particles are generated along with the generation of large-diameter particles, and these small-diameter particles are generated between the tail of the ink column that should be separated and the tip of the ink column that remains at the same time as the large-diameter particles are generated. After that, they fly at the same speed as the large-diameter particles and do not coalesce (uniform velocity small-diameter particle generation state).

These small-diameter particles are generated under the same electrostatic pressure conditions as the preceding large-diameter particles, so they are charged, but the amount of charge relative to the volume (weight) is greater than that of the large-diameter particles. Since these small-diameter particles are independently deflected during flight, the amount of deflection becomes excessive. If the amount of excessive deflection is significant, the small-diameter particles will adhere to the deflection electrode plate and contaminate the device components. An unstable range indicates that the cycle of ink droplet generation is irregular.

Another point that needs to be noted in FIG. 1 is that the range of recording characteristics changes depending on temperature, and furthermore, depending on a particular excitation voltage, it deviates from a good range.
The reason why it changes with temperature is thought to be due to the above-mentioned change in the physical properties of the ink due to temperature, and the temperature characteristics of the excitation efficiency of the nozzle. From the results shown in FIG. 1, if the excitation voltage is corrected according to the nozzle temperature, good recording can always be obtained. This correction will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows a waveform converter 12 that converts a rectangular wave into a sine wave,
A thermistor 10 is shown. Resistor R3 and transistor TRS constitute a switching circuit. Resistance R1
constitutes a voltage dividing circuit that divides the DC voltage +15V together with the thermistor 10. Capacitors Cl, C2} and coil L1 constitute a resonant circuit, and the clock signal CLOCK
resonates at the fundamental frequency of Resistance R4, R5, variable resistance V
The Rl hexagram and the amplifier AMP constitute an amplifier circuit.

The resistor R2 is for supplying a signal to the resonant circuit, and its value is selected to be . Next, the operation will be explained.

The voltage Ei is as shown in FIG. 4 because the DC voltage +15V divided by the resistor R1 and thermistor 10 is switched by the transistor TRS in response to the clock signal CLOCK. Voltage Ei is supplied to the resonant circuit by resistor R2. In the resonant circuit, components other than the resonant frequency are excluded, so the sine wave signal is sent to the amplifier AMP, amplified, and output. The output voltage is calculated using the following formula.

The gain A of the amplifier is the output voltage EOUT, the voltage Ei is the temperature coefficient K, and the temperature coefficient KTH is the temperature coefficient of the thermistor. Therefore, in order to perform correction, the temperature coefficient of the temperature characteristic shown in Fig. 1 and the temperature coefficient of the temperature characteristic shown in Fig. 3 are used. It is only necessary to match the temperature coefficients of the waveform conversion circuits.

In this embodiment, the following is true.

According to the embodiment of the present invention described above, since the excitation voltage is corrected by the thermistor and the excitation voltage is always kept at the optimum value, (1) there is no need to control the temperature of the ink or nozzle.
Good recording with little recording distortion can be obtained over a wide temperature range.

(2) Stable recording can be obtained over a wide temperature range.

(3) Eliminates contamination of device components due to small diameter particles.

(4) By using a thermistor, the number of parts is reduced, and the recording described in items (1) and (2) above can be obtained at low cost.

(5) Since correction is performed using a low-voltage circuit that is not amplified, the thermistor requires less power capacity and is therefore smaller.
It becomes an inexpensive device. It has excellent effects such as

In the example, the thermistor was placed near the nozzle, but it can be installed in a thermally coupled manner with the nozzle, or it can be placed away from the nozzle as long as it exhibits a value equivalent to the temperature of the nozzle or ink. This is consistent with the purpose and effect of the invention.

Since the temperature coefficient of the recording characteristic is negative, a thermistor with a negative characteristic was used, but it will be understood that depending on the circuit configuration, a thermistor with a positive characteristic can be easily used.
Further, in the embodiment, the means for detecting the temperature and the means for varying the excitation voltage are electrically coupled, but other coupling means, such as manual switching and adjustment depending on the season, will still achieve the purpose and effect of the present invention. It matches. According to the present invention, (1) Since the device is always kept under optimal conditions with respect to the environmental temperature, it is possible to obtain stable records with good quality, and furthermore, the device components are prevented from being contaminated by small-diameter particles. It disappears.

(2) Since there is no need to perform temperature control, a small and inexpensive device can be realized.

(3) No heating or cooling is required, so no warm-up time is required.

It has excellent effects such as:

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram for explaining the operation of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a detailed configuration of a part of FIG. 1. FIG. 4 is a signal waveform diagram showing the operation of FIG. 3. 1... Ink supply source, 2... Nozzle,
3...Charging electrodes, 4a, 4b...Deflection electrodes, 5...DC high voltage source, 10...
Thermistor, 12... Waveform converter, 13...
... Excitation amplifier, 11 ... High frequency source, 14.
... Recording signal generator, 15... Recording signal amplifier, 9a, 9b... Ink particles, 6...
...Recording paper, R1...Resistor.

Claims (1)

[Claims] 1. An ink supply source, a nozzle to which pressurized ink is supplied from the ink supply source, a vibrator coupled to the nozzle, and an excitation voltage supplied to the vibrator. In an inkjet recording apparatus having an excitation circuit, a means for charging ink particles generated from a nozzle, and a means for deflecting the charged ink particles, the excitation circuit includes a detection means for detecting the temperature of the nozzle or the ink, and a detection means for detecting the temperature of the nozzle or the ink. An inkjet recording apparatus comprising an excitation intensity control means for controlling the excitation intensity of the nozzle by the vibrator based on the output of the means. 2. In claim 1, the detection means has means for converting the temperature of the nozzle or ink into an electric signal, and the excitation intensity control means has an excitation voltage that changes based on the electric signal according to the temperature. An inkjet recording apparatus characterized by having an excitation voltage generating means that generates an excitation voltage. 3. The inkjet recording according to claim 2, wherein the detection means includes a thermistor, and the excitation voltage generation means includes a resistor connected in series with the thermistor to divide the excitation signal voltage. Device.