JPS61173949A - Ink jet head - Google Patents

Abstract

PURPOSE:To shorten a rising time, by enhancing vibration efficiency by improving the heat transfer efficiency in the heating of ink. CONSTITUTION:An ink column is injected from a nozzle 13 by the vibration of a vibrator 12 driven by an exciting power source 11 and the temp. of ink is controlled so as to be made constant by a heat generator 14 energized by the power source 15 on the surface of a liquid chamber part 10b, a temp. detector 16 and a temp. control part 17. Because a ceramic body 10 has good heat conductivity and directly applied to the surface of the thinned part of the heat generator 14 by vapor deposition or coating, the ink can be rapidly raised to predetermined temp. The length l2 of a flange part transmitting vibration from the vibrator 12 and the distance L between the boundary B of a filter part 18 and the nozzle 13 are set so that the resonance frequency of both flange and filter parts becomes same to or slightly higher than exciting frequency to raise vibration efficiency and, therefore, a rising time can be sufficiently shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a head structure of an inkjet recording apparatus.

The inkjet recording device of Shimai Chenghou directs the ink from the ink supply section to a thin nozzle, and continuously sprays the ink in the form of particles from the opening at the tip of this nozzle.

In order to draw characters, figures, etc. on a recording medium, it is necessary for the frequency of occurrence of ink droplets ejected from a nozzle to be stable and for the size of the ink droplets to be uniform. however.

The characteristics of ink are affected by changes in ambient temperature, and in particular, the viscosity of ink increases as the ambient temperature decreases. In this way, the viscosity of the ink increases.

The frequency of ink droplet generation decreases, and the ink droplet diameter increases. As described above, if the frequency of occurrence of ink particles or the diameter of ink particles becomes non-uniform, characters etc. printed on a recording medium become unstable and unclear, resulting in a lack of reliability in quality. Therefore, conventional methods have been to control the viscosity of the ink by heating the ink.

FIG. 4 is a diagram showing a conventional ink temperature control system. Ink is supplied under pressure by a pump (not shown) and is sent to the liquid chamber 4 of the head 3 via a filter 1 and a tube 2, where it is driven Due to the vibration of the vibrator 6 excited by the power source 5,
Ink in the liquid chamber 4 is ejected from the nozzle 7. 8 is a heating element provided in the filter section, 9 is a power source, and the heating element 8 heats the ink staying in the filter section. However, in the apparatus shown in FIG. 4, since the distance from the heating element 8 to the nozzle part 1 is long, the ink temperature drops depending on the external temperature, and if the contact surface between the heating element and the ink is heated too much, the ink will Because it changes the temperature, it can only be heated up to a maximum of about 70 degrees Celsius, and it takes time for the temperature to become constant depending on the heat capacity of the head. In particular, it takes time to start up when the power supply 9 is turned on. Waiting time was an issue.

The present invention was made in view of the above-mentioned circumstances,
The rise time is shortened by improving heat transfer efficiency in ink heating and increasing vibration efficiency.

■--Sato In order to achieve the above object, the present invention provides an insulating, thermally conductive ceramic inkjet head in which a heating element is directly provided by vapor deposition or coating. It is characterized by being set equal to or slightly higher than fp. below,
An explanation will be given based on an example of the present invention.

FIG. 1 is a diagram showing an embodiment of an inkjet head according to the present invention. In the figure, numeral 10 is a head body made of a ceramic material with good thermal conductivity, and is composed of a flange portion 10a and a liquid chamber portion 10b. , vibrations from a vibrator 12 driven by an excitation power source 11 are transmitted, and an ink column is ejected from a nozzle 13. Liquid chamber part 1 of ceramic body O
A heating element 14 energized by a power source 15 is mounted on the surface of 0b.
is directly vapor-deposited or coated, and the output of the temperature sensor 16 similarly provided on the surface of the liquid chamber is sent to the temperature controller 1.
7, and the temperature control section 17 controls the ink temperature to be constant. Ceramic body has good thermal conductivity,
Moreover, since the heating element is directly deposited or coated on the surface, the ink temperature can be quickly brought to a predetermined temperature. Furthermore, by configuring the liquid chamber part 10b thinly,
It becomes possible to further improve thermal conductivity.

On the other hand, the length Q2 of the flange portion to which the vibration from the vibrator 12 is transmitted is set to have a resonance relationship of Q2=L (n: a positive integer). λ is determined by the sound speed and frequency at the flange portion, and by setting the resonance frequency fm to be the same as or slightly higher than the excitation frequency, it is possible to drive at the resonance frequency and improve vibration efficiency. . In this example, the excitation frequency fp is set to 132
KHz and mechanical resonance frequency fm of 140 K
It was set around Hz.

Next, regarding the liquid chamber section, the pressure waves are reflected at the boundary B of the filter section 18, and the number of boundaries B, λQ: the wavelength of the sound wave in the ink, is set so that the liquid resonates. By setting the frequency fr to be the same as or slightly higher than the excitation frequency, liquid resonance can be caused and vibration efficiency can be improved. In the configuration shown in FIG. 1, the heating element 14 is located near the filter 18, and the heat transfer efficiency is improved by heating the part with a large contact area with the ink.

FIG. 2 shows the impedance characteristics of the head configured as shown in FIG. 1, and as mentioned above, the mechanical resonance point fm and the liquid resonance point fr
is set to be the same as or slightly above the head excitation frequency fP, so that it becomes the primary resonance point of the entire system.

Figure 3 shows the wetted surface of 5 when the ceramic material is porous.
It is coated with 10c such as i02, SiN, Teflon, etc. Since Teflon coating etc. are processed at high temperature, it is easy to heat treatment after coating.

- As described above, according to the present invention, a ceramic material is used for the head body, and a heating element is directly attached to the surface of the ceramic material to heat the ink, thereby increasing heat transfer efficiency and reducing the mechanical resonance point and liquid resonance of the head. Since the point is set to be the same as or slightly above the excitation frequency for resonance driving, the vibration efficiency can be increased and the rise time when the power is turned on can be sufficiently shortened.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of an inkjet head according to the present invention, Fig. 2 is a diagram showing the relationship between impedance characteristics of the head, resonance point, and excitation frequency, and Fig. 3 is a diagram showing the relationship between the impedance characteristics of the head, the resonance point, and the excitation frequency. Figure 4 shows the head that has been
10b showing the conventional head configuration; liquid chamber section; 10c;
...Coating section, 11...Excitation power supply, 12...
Vibrator, 13... Nozzle, 14... Heating element, 15.
...Power source, 16...Temperature sensor, 17...Temperature control unit, 18...Filter.

Claims (6)

[Claims] (1) In an insulating, thermally conductive ceramic inkjet head in which a heating element is directly provided by vapor deposition or coating, the mechanical resonance point fm of the head member is set to be the same as or slightly higher than the head excitation frequency fp. inkjet head. (2) The ceramic head portion is formed of a flange portion and a liquid chamber portion, and the length of the flange portion is set to be a mechanical resonance point fm. inkjet head. (3) The inkjet according to claim (1), wherein the liquid chamber length is a liquid resonance point (fr), and the liquid resonance point is set to be the same as or slightly higher than the head excitation frequency fp. head. (4) Claim (1) characterized in that the liquid chamber is made thinner and the heating element is provided in the thinner part.
The inkjet head described in section. (5) The inkjet head according to claim (1), further comprising a filter provided near the heating element. (6) The inkjet head according to claim (1), wherein the liquid contact portion of the head member is coated with a sealing material.