JPS635948A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To obtain the long life of the title recording head and to make the stable high speed discharge of ink easy, by providing the ink chamber in which ink is preheated and the variable resistance of which electric resistance increases as the temperature of preheated ink is increased. CONSTITUTION:A heater 25 and a bimetal 24 are provided on the inside of an ink subtank 22 to preheat ink. A positive characteristic thermister 23 is joined thereto. They are wired in series to heating elements 16 via electrode 15. Power is intermittently supplied to the heating elements 16 with switching elements SW and joule heat is generated. An ink drop 27 is discharged from a nozzle 17 by the change of the pressure generated by the occurrence of the film boiling of recording ink in contact with the surface of the heating elements 16. The positive thermistor 23 is the variable resistance of which electric resistance increases as the temperature of preheated ink is increased. When the temperature of ink is low, the voltage impressed to the heating elements 16 is high. The voltage gradually decreases as the temperature of ink is increased. By possessing the structure having the variable resistance of which electric resistance increases as the temperature of ink is increased, the acquisition of its long life and the high speed, stable discharge of ink can be made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording head that performs recording by ejecting ink using thermal energy.

C. Prior Art] The structure of a conventional inkjet recording head that performs recording by discharging ink using thermal energy is disclosed in Japanese Patent Application Laid-Open No. 1982-
220757 had a structure in which only a heater was provided in the fourth ink chamber, and the ink was preheated only when the ambient temperature in the fourth ink chamber was low.

[Problem that the invention seeks to solve]

However, in the prior art described above, the ink is preheated only when the ambient temperature is low, and is not effective when the ambient temperature is not low.

Furthermore, since the heater in the ink chamber is controlled by on/off control, the ink temperature fluctuates, making it difficult to eject ink stably.

Furthermore, even though the ink is preheated, the voltage applied to eject the ink is not lowered.
It has a short lifespan.

Therefore, the present invention is intended to solve these problems.
The purpose is to provide an inkjet recording head that has a long life and is capable of ejecting ink stably at high speed.

[Means for solving problems]

The inkjet recording head of the present invention is characterized by a structure having an ink chamber for preheating ink and a variable resistance whose electrical resistance increases as the temperature of the preheated ink increases.

〔Example〕

The present invention will be explained in detail based on examples.

FIG. 1 is a schematic diagram of the overall configuration of an inkjet recording apparatus including an inkjet recording head according to the present invention.

[In Figure 1, the inkjet recording head l of the present invention
Is recording ink supplied from the ink tank 5 through the ink supply pipe 12'ik? Carriage guide 6 while receiving
The recording paper 3 moves in the direction of the arrow I while being guided by the recording head 1, and performs inkjet recording on the recording paper 3, which is fed by an intermittent line feed in synchronization with the recording head 1, by the platen 2 and guide rollers 4.

wcz diagram μ1 I of the inkjet recording head 1 of the present invention
FIG. 3 is a perspective view showing the II structure, and FIG. 3 is a main sectional view of FIG. 2.

In Figure 2, the substrates 13 and 14 are joined to the base 21 with an ink supply groove in the center, and the gap plate 18 is spaced by μ so that the nozzle 17 is directly above the heating element 16. The sealing part 20tl-
The above-described paste 21 was joined to an ink sub-tank n equipped with an ink supply pipe 12 and sealed with a thermosetting sealant or the like. Inside the ink subtank η.

Heater 25, bimetal 2 to preheat the ink
I have set up 4. Also, on the inner wall of the infusator/habit,
Positive temperature coefficient thermistor 23 was joined. Positive characteristic thermistor 2
3 was wired in series with the heating element 16 through the electric oven 15.

Electric power is intermittently supplied to the heating element 16 by the switching element SW, generating Joule heat, and the pressure generated by film boiling of the recording ink in contact with the surface of the heating element 16 changes, resulting in a change in the pressure shown in Figure 3. Similarly, 27 gold ink droplets are ejected from the nozzle 17.

Characteristics of positive temperature coefficient thermistor B are shown in Figure 4.

As shown in FIG. 4, the positive temperature coefficient thermistor 23 is a variable resistor whose electrical resistance increases as the temperature of the preheated ink rises, and is wired in series with the heating element 16 as shown in the IClegZ diagram. Therefore, the voltage applied to the heating element 16 changes depending on the temperature of the recording ink. That is, when the ink temperature is low, the voltage applied to the heating element 16 is high, and as the ink temperature decreases, the voltage applied to the heating element 16 gradually decreases. In other words, the positive temperature coefficient thermistor device controls the voltage applied to the first heating element 16 to an analog gas according to the preheated ink temperature.

Using a recording solution containing 43 wt% water, 52 ut% diethylene glycol, and 5 wt% water-soluble dye, the life spans of the inkjet recording head of the present invention and the conventional inkjet recording head were measured. The measurement results are shown in Table 1. In Table 1, the temperature at which the bimetallic cell is turned off is abbreviated as OFF temperature.

Table 1 Note that in both cases, the driving frequency was 2 KHg, the applied pulse width was 6β89, and the ambient temperature was 15°C.

Furthermore, using a conventional inkjet recording head that does not preheat ink and an inkjet recording head of the present invention,
When the above-mentioned recording ink was ejected and an image quality evaluation gfJ was performed, the results shown in % Table 2 were obtained.

Happy 2 Table 2 shows β, and the evaluation criteria for both sides are: ◎・φ・Paintings of good quality ○...Paintings that can be used for practical use are ×---・Not for practical use^ Both edges, In Table 2, as in Table 1, the temperature at which the metal switch is turned off is abbreviated as OFF temperature. In both cases, the applied pulse width was 6 μm and the ambient temperature was 15° C.

〔Effect of the invention〕

As described above, according to the present invention, by using an ink chamber that preheats the ink and a variable resistance whose electrical resistance increases as the temperature of the preheated ink rises, it has a long life. , and it becomes easy to eject ink stably at high speed. It has this effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic overall configuration diagram of an inkjet recording device having an inkjet recording head according to the present invention. Figure 2 is a perspective view showing the W structure of the inkjet recording head of the present invention. Figure 3 is a main sectional view of the inkjet DD recording head of the present invention. The vg4 diagram is a diagram showing the characteristics of a variable resistor in which the electrical resistance increases as the temperature rises.

Claims (1)

[Claims] An inkjet recording head that performs recording by ejecting ink using thermal energy, and is characterized by a structure having an ink chamber that preheats the ink and a variable resistance whose electrical resistance increases as the temperature of the preheated ink increases. head.