JP2004130573A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure capable of keeping a sufficient strength of the housing of a print head without sacrifice of cleaning performance at a high voltage part of the housing. <P>SOLUTION: A deflection electrode mounting part is integrally molded out of a plastic resin as an independent component and set on a metallic print head. Furthermore, the resin is sandwiched between the metallic print head and an ink heater. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a print head for an ink jet recording apparatus, and contributes to improvement in handleability and maintainability.
[0002]
[Prior art]
A charge control type ink jet recording apparatus (hereinafter, referred to as IJP) converts a high-pressure jetted ink stream into small droplets by micro-vibration of a piezoelectric element or the like of a nozzle, charges with a charging electrode, and deflects in a deflecting electric field with a deflecting electrode. This is a device that prints dot characters. A voltage of several hundred to several thousand volts is applied to each of the charging electrode and the deflection electrode. In particular, when a conductive substance such as ink adheres to the deflection electrode, a voltage leak causes a reduction in the amount of deflection, and further a reduction in print quality. Therefore, it is necessary to clean around the deflection electrode before starting IJP.
[0003]
As a measure for preventing leakage of dirt, it is good to increase the creepage distance with a spacer or the like. However, since the surface tension of the ink is low, the ink has a property of penetrating into the joint surface of the component without any gap. The ink that has entered the gap cannot be completely removed except for disassembly and cleaning. In order to solve this problem, the deflection electrode spacer and the like are formed in a boss shape and are integrally molded with plastic. However, there is a problem that the print head housing made of plastic has lower strength than metal.
In addition, a glass additive is sometimes added to plastic in order to increase dimensional accuracy, but the molded product becomes brittle against impact, is easily damaged by the housing, and tends to be broken.
[0004]
On the other hand, the charge control type IJP is a method of printing by making ink small droplets. Droplet size depends on the physical properties of the ink. However, since the physical properties of the ink change due to a change in ambient temperature, IJP has been used in a limited temperature range. In order to solve this, there is a method in which the temperature is kept constant by heating the ink before the droplet size is reduced. Thereby, the operating temperature range in a low temperature range can be expanded. By mounting a heater in a plastic housing, the ink can be efficiently heated and transmitted to the ink. However, in the case of a metal print head, a part of the heat of the heater escapes to the print head, so that the efficiency is poor and the ability to follow the ambient temperature is poor. This can be dealt with by increasing the energizing voltage of the heater. However, since there is a limit to flammable ink, it is necessary to change the shape of the heater to improve the heat transfer efficiency.
Further, the heated ink flows into the nozzles and dissipates heat before the ink is reduced to small droplets. Since the heater and the nozzle need to be replaced as maintenance parts, they are connected by a tube that is resistant to organic solvents.
As a material of the nozzle, rigid stainless steel which is resistant to an organic solvent and is used. However, since stainless steel is a metal and has good heat dissipation unlike resin, even if heated by a heater, it cools down immediately before droplet formation, making it difficult to control.
[Patent Document 1]
JP-A-7-76076
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a structure capable of sufficiently maintaining the strength of the print head housing without impairing the cleaning performance of the high voltage portion of the housing.
[0006]
Another problem is to efficiently transfer the heat of the heater to the ink with a simple configuration.
[0007]
Still another problem is to reduce the heat radiation of the nozzle with an easy configuration.
[0008]
[Means for Solving the Problems]
This is achieved by forming the high-voltage portion of the metal print head, that is, the mounting portion of the deflection electrode integrally with an insulator to form a separate part.
[0009]
Yet another solution is achieved by sandwiching a resin between the head base and the heater.
[0010]
Yet another solution is achieved by sandwiching insulation between the nozzle and the nozzle base.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a side view illustrating the present invention. The ink (omitted in the figure) pressurized from the IJP main body (omitted in the figure) is supplied to the heater 3 via the ink tube 2 in the head cable 1. When the ambient temperature becomes low, the temperature is detected by a thermistor 5 provided in the print head 4, and power is supplied from the IJP main body to the heater 3 to heat the ink. The inside of the heater 3 is provided with an ink flow path, and has a configuration in which heat is transferred from the heater element. The heated ink is supplied to the nozzle 8 via the nozzle tube 7 via the valve 6. Here, the valve 6 is a valve for controlling ejection and stop of ink.
FIG. 2 is a plan view of a nozzle representing the present invention.
[0012]
The ink supplied from the nozzle tube 7 is ejected as a jet stream from an orifice plate 16 having minute holes. The ink jet flow is minutely constricted by the vibration of the driven piezo element 15 due to the sine wave signal output from the main body, and is reduced into droplets by the surface tension. The ink jet flow is reduced into droplets when the physical properties of the ink have a fixed relationship with the flow speed of the jet flow, the hole diameter of the orifice plate 16, the piezo element vibration frequency, and the piezo element vibration amount.
[0013]
The charging electrode 9 and the ink jet stream immediately before the dropletization are dropletized while charged by electrostatic induction. The ink droplets are charged in an amount corresponding to the character information from the main body. The charged ink droplets are applied with a high voltage to the deflection electrode 11 from a high voltage power source (not shown) of the main body via a high voltage line 10. The deflecting electrode 11 is provided on a deflecting base 12 made of an insulator, and a boss stands on the electrode mounting portion to increase the creepage distance. Further, the packing 17 is sealed so that the ink and the cleaning liquid do not leak to the high voltage line 10 inside the print head 4.
[0014]
The charged droplet in the deflection electric field is deflected according to the charge amount. The deflected droplet lands on a printed matter to form a dot character.
[0015]
A deflection voltage of several kilovolts is applied. At the moment when the ink stops, such as when the IJP stops, the ink jet flow bends due to a decrease in the ink pressure, thereby staining the print head 4. Also, during operation, ink powder may enter the print head 4 due to the rebound of the ink that has landed on the printed matter, and contaminate the deflection electrode 11. Dirty ink reduces the creepage distance of the deflection base and causes voltage leakage. When voltage leakage occurs, the amount of deflection and the quality of printing are reduced. In such a case, it is necessary to wash the deflection base 12 with the cleaning liquid during the IJP operation or at the end of work. The deflection base 12 is fixed to a boss to increase the creepage distance between the deflection electrodes 11. Since the boss is made of an insulator and is molded integrally with the deflection base 12, the boss can be washed away without leaving ink on the deflection base 12, so that the creepage distance can always be ensured.
[0016]
Next, another embodiment of the present invention will be described.
When the ambient temperature decreases, the physical properties of the ink jet stream change, and the state of droplet formation changes. In order to maintain the print quality, the vibration amount, flow velocity, and ink temperature of the piezo element 15 are controlled by the ambient temperature so as to keep the droplet size constant. Of these, the ink temperature is heated by the heater 3. In order to respond quickly to changes in the ambient temperature, it is necessary to efficiently transfer heat from the heater 3 to the ink. The heater 3 is fixed to the print head 4 via a heater base 13 made of resin. The print head 4 is formed of metal to make it robust, but has good heat transfer, so if the heater 3 is directly mounted, the heat will escape. In the present invention, since the heat transfer is cut off by the heater base 13, the heat can be efficiently and quickly transferred to the ink.
[0017]
Further, another embodiment of the present invention will be described.
[0018]
1 and 2, the nozzle 8 is attached to a metal nozzle base 18 via a resin nozzle jacket 14. Since the nozzle jacket 18 is made of resin, heat transfer from the nozzle 8 to the metal nozzle base 18 and the print head 4 is blocked to prevent heat transfer. Further, the ink heated by the heater 3 is transmitted to the nozzles via the nozzle tube 7, but can be partially shielded from the outside by the nozzle jacket 18, so that heat radiation can be reduced.
[0019]
【The invention's effect】
According to the present invention, the deflecting electrode is mounted on the deflecting base of the insulator and provided in the print head, so that dirt can be easily washed away with the cleaning liquid, so that the creepage distance can be always maintained, and robust printing can be performed. A head can be configured.
Further, according to the present invention, by providing the heater base made of resin between the heater and the print head, it is possible to transmit the heat transfer of the heater to the ink without escaping to the print head.
[0020]
Further, according to the present invention, by providing a resin nozzle jacket between the nozzle and the nozzle base, heat radiation of the ink tube and the nozzle can be reduced.
[Brief description of the drawings]
FIG. 1 is a side view of a print head.
FIG. 2 is a plan view of a nozzle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Head cable, 2 ... Ink tube, 3 ... Heater, 4 ... Print head, 5 ... Thermistor, 6 ... Valve, 7 ... Nozzle tube, 8 ... Nozzle, 9 ... Charging electrode, 10 ... High voltage line, 11 ... Deflection electrode , 12: deflection base, 13: heater base, 14: nozzle jacket, 15: piezo element, 16: orifice plate, 17: packing, 18: nozzle base.

Claims (6)

In the head base of a charge control type ink jet recording apparatus including a nozzle for generating ink droplets, a charging electrode for charging the droplets, and a deflection electrode for deflecting the droplets by an electrostatic field, a portion where the deflection electrodes are arranged is insulated. A print head for an ink jet recording apparatus, comprising a body. The print head according to claim 1,
A print head for an ink jet recording apparatus, wherein the head base is made of metal. The print head according to claim 1 or 2,
A print head for an ink jet recording apparatus, comprising: a heater for heating ink to be supplied to a nozzle; and a resin sandwiched between the heater and a head base. The print head according to claim 1 or 2,
A print head of an ink jet recording apparatus, wherein a nozzle is fixed to a head base via a resin. The print head according to claim 4,
A nozzle head for fixing via a resin is a resin, the print head of the ink jet recording apparatus. The print head according to claim 4,
5. A print head for an ink jet recording apparatus, wherein the nozzle jacket for fixing via the resin according to claim 4 is a resin.

Images