JP2001253069A - Ink jet recorder and nozzle therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a vibration displacement of a vibration applying section in order to stabilize atomizing of a nozzle in an ink jet recorder that executes the atomizing by applying vibration to ink to be ejected from an orifice. SOLUTION: The vibration applying section comprises a piezoelectric body 31, a piston 30 of which the one end is fixed to the piezoelectric body 31 and the other end makes contact with the ink, and a sealing member 26 provided to the piston 30. The piezoelectric body 31 is supported to a frame by an elastic member 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to a nozzle of the apparatus.

[0002]

2. Description of the Related Art In general, a nozzle of an ink jet recording apparatus which ejects ink to generate ink particles to perform printing is provided with a predetermined vibration by a vibrating section which vibrates the ejected ink at a predetermined frequency. Is performed. Such a prior art is disclosed in Japanese Unexamined Patent Publication No.
No. 40 publication.

[0003]

In the above-mentioned prior art nozzle, there is a graining mode as shown in FIG. The particle formation mode changes depending on the displacement of the vibrating section as shown in FIG. 11, and the low-speed satellite mode in which the satellite particles catch up with the succeeding main particles, the constant-velocity satellite mode in which the satellite particles do not unite with the main particles, the satellite particles, Is a high-speed satellite mode that catches up with the preceding main particles, and a satellite-free mode in which no satellite particles are generated. Among these, a good particle formation mode in which particles can be stably charged is a high-speed satellite mode.In a low-speed satellite mode, a constant-speed satellite mode, and a non-satellite mode, an ink column length is unstable and printing is difficult. It is not suitable for printing because ghosts occur.

However, in the above prior art, one end on the orifice side is supported by an elastic member such as an O-ring, and one end (ink supply side) in the vibration direction of the vibrating section is fixed so as not to be moved by the housing (one end fixed). , One end free mode). Therefore, the vibration of the housing affects the displacement of the vibrating unit. As for the vibration state of the housing, the vibration mode and its size change depending on the supporting force of the vibrating unit, the supporting method of the housing, and the temperature change. Therefore, the vibration of the vibrating part is not stable,
There is a problem that the particles cannot be stably formed.

In order to stabilize the vibration of the vibrating section, it is necessary to prevent the resonance frequency from appearing in the vicinity of the driving frequency. However, a temperature change of 50 ° C. changes the resonance frequency by about 5%. At this time, when the driving frequency is 30 kHz away from the resonance frequency, there is a change in displacement of 3 dB, and the particle state changes.

At this time, the displacement of the piezoelectric body may be controlled by changing the resonance frequency, but there is a problem that the driving circuit of the piezoelectric body becomes complicated. Therefore, it has been experimentally found that the change in displacement of the piezoelectric body must be within 1 dB in order not to affect the particle formation. For this purpose, the resonance frequency and the drive frequency need to be separated by 50 kHz or more. Since the driving frequency is generally 20 to 100 kHz, it is necessary to at least set the resonance frequency of the piezoelectric body to 150 kHz or more. To do this, the size of the vibrating section may be reduced,
Since the vibrating part is supported so as to be in a vibration mode in which the vibrating part is fixed at one end and free at one end as in the above-described prior art, the size of the piezoelectric body must be considerably reduced. Therefore, there is a problem in that the generation force required for granulation decreases, and the displacement required for granulation cannot be obtained. An object of the present invention is to stabilize particle formation of a nozzle.

[0007]

In order to achieve the above object, in a nozzle of an ink jet recording apparatus comprising an orifice section for ejecting ink and a vibrating section for applying vibration to the ink, the vibrating section is made up of only an elastic member. It is intended to be supported.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, a schematic configuration of the ink jet recording apparatus will be described with reference to FIG.

The ink supply path 21 comprises an ink container 1 for storing ink, an ink pump 2 for pressure-feeding ink, a pressure regulating valve 3 for adjusting ink pressure, a solenoid valve 4 for opening and closing a flow path, and a filter 5. The ink is supplied to the nozzle 6.

A recording signal source 16 is connected to the charging electrode 7. By applying a recording signal voltage to the charging electrode 7, the ink particles 8 ejected from the nozzle 6 are charged.

A high voltage source 15 is applied to the upper deflection electrode 9, and the lower deflection electrode 10 is grounded. For this reason, an electrostatic field is formed between the upper deflection electrode 9 and the lower deflection electrode 10, and the charged ink particles 8 are deflected according to the amount of charge, and printing is performed.

The ink recovery path 22 is composed of a play 11, an electromagnetic valve 18, a filter 12, and a recovery pump 14. The ink recovery path 22 recovers ink particles 8 that are not charged by the charging electrode 7 and are not involved in recording. Return to container 1.
The ink circulation path 23 is connected to the ink recovery path 22 from the nozzle 6 via the electromagnetic valve 17, and circulates the ink in the nozzle.

Next, an embodiment of the nozzle according to the present invention will be described with reference to FIG. The ink supply path 21 and the circulation path 23 are provided in the body 25, the orifice plate 29, the joint 43 bonded to the body 25, and the seal member 46. The ink is guided to an ink chamber 27 provided in an orifice plate 29 and is ejected from an orifice 28. FIG. 7 shows the orifice plate 29 viewed from the ink supply side.
Are arranged such that a swirling flow is generated in the chamber 27 when the ink is supplied, so that air does not accumulate.

The orifice plate 29 is screwed to the body 25 using a screw hole 45. Seal member 46
Is made of ethylene propylene rubber (EPDM) or silicone rubber, is sandwiched between the body 25 and the orifice plate 29, and prevents leakage of ink.

A vibrating section for generating a vibration in the ink in the ink chamber 27 includes a piezoelectric body 31, a piston 30, and an O-ring 26. The piezoelectric body 31 uses a laminated piezoelectric element capable of generating a large displacement at a low voltage. In this embodiment, the piezoelectric body 31 is made of PZT and has a length of 5 mm. It should be noted that any actuator that can displace about 0.1 μm in place of the piezoelectric body 31 may be used.

The piezoelectric body 31 is held by an elastic member 41 fixed to the body 25 and the base 24. The elastic member 41 used was ethylene propylene rubber (EPDM) having a rubber hardness of 50 to 90. The elastic member 41 does not cause swelling, corrosion, deterioration, or ink leakage due to the ink.
Other units may be used as long as they can hold the vibration unit in the free mode at both ends. Further, a sheet-like elastic member 46 as shown in FIG. 3 may be used. The lead wire 42 attached to the side surface of the piezoelectric body 31 is connected to the excitation source 13,
The piezoelectric body 31 is driven at a predetermined frequency. In this embodiment,
Vibration was performed in the direction of ink ejection at a frequency of 93 kHz.

The piston 30 is bonded to the piezoelectric body 31, and applies the vibration of the piezoelectric body 31 to the ink. Piston 30
Has a cylindrical shape, and the surface of the orifice plate 29 that contacts the ink is flat. A groove for receiving the O-ring 26 is provided on the side surface.

The O-ring 26 is made of ethylene propylene rubber (EPDM) having a wire diameter of 0.8 mm and a rubber hardness of 50 to 90, and is fitted in a groove provided in the piston 30. The piston 30 fitted with the O-ring 26 is
The ink chamber 27 is fitted into a cylindrical hole provided in the ink chamber 27.
It has a sealing structure so that the ink inside does not enter the piezoelectric body 31 side. A groove for fixing the O-ring 26 may be provided on the body 25 side.

FIG. 5 shows an embodiment in which a diaphragm 44 is used instead of the piston 30 of the vibrating section in the embodiment of FIG. The diaphragm 44 is adhered to the piezoelectric body 31, and applies the vibration of the piezoelectric body 31 to the ink. The material of the diaphragm 44 is SUS303 and has a thickness of 10 μm. The material of the diaphragm 44 is not corroded by the ink.
Others may be used. As shown in FIG. 6, the entire surface of the piezoelectric body 31 is covered with the elastic member 4 without using the diaphragm 44.
7 may be covered.

FIG. 4 shows an example in which only one end of the vibrating section is held by an elastic member. The piston 30 attached to the piezoelectric body 31 is supported by the O-ring 26 and the seal member 46, and the vibrating section is supported by the body 25. The piston 30 may be plate-shaped, but it is made convex so that the volume of the chamber 27 is reduced, and the ink ejected from the orifice 28
Vibration is transmitted efficiently.

Next, air or foreign matter in the ink chamber 27, which is used to stabilize the ejection of ink, is removed by the ink circulation path 2.
The method of removing in step 3 will be described. First, a control circuit for the ink supply and circulation control circuit will be described with reference to FIG. The CPU 300 is a central processing unit that controls the ink supply and circulation of the present embodiment. ROM32
A read-only memory 0 stores programs and control data necessary for the operation of the CPU 300. R
The AM 310 is a rewritable memory that temporarily stores data and the like handled by the CPU 300 during the execution of the program.

The bus line 400 is a signal line including all data, address signals, and control signals from the CPU 300. The interface circuit 330 mediates input and output of data, address signals, control signals, and the like. The pump control circuit 340 controls the driving of the ink pump 2 and the recovery pump 14. The valve control circuit 350 controls the opening and closing of the solenoid valves 4, 17 and 18. The timer includes a clock generator 390, a frequency divider 380, and a counter 370. Dividing circuit 380 divides the signal output from clock generator 390. Counter circuit 370 counts the signals divided by frequency dividing circuit 380. The counter circuit 370 can be reset by a command from the CPU 300, and the frequency division ratio of the frequency
It can be changed by the instruction of U300.

Next, an ink circulation method will be described with reference to FIG. When an instruction to start the device is output from the input device 19 to the control device 20, the process of step 100 is performed.

In step 100, the recovery pump 14 and the ink pump 2 are started, and the solenoid valves 4 and 17 are opened.
The ink solvent is supplied from the ink solvent supply path 23 to the nozzle 6. Since the solenoid valve 17 is open, ink does not jet from the nozzle 6 and is collected in the ink container 1 through the ink collection path 22.

In steps 110 to 120, the timer is started after resetting, and when the timer reaches the set value, the process proceeds to step 130, where the solenoid valve 17 is closed and the solenoid valve 18 is opened. Therefore, the ink in the ink chamber 27 is pressurized, and the ink is ejected from the nozzle 6.

In step 140, the excitation voltage is applied to the piezoelectric body 31 from the excitation source 13, the ink ejected from the nozzle 6 is turned into particles, and the ink becomes a printable state, and the processing for starting the apparatus ends.

With the above configuration, the body 2
5. Transmission of vibration from the base 24 to the vibrating portion is reduced, and stable particle formation can be performed. In addition, the resonance frequency of the vibration unit can be set to 200 to 240 kHz, and the drive frequency and the resonance frequency of the vibration unit can be sufficiently separated from each other. It becomes possible. Further, since the ink circulation path 23 is provided to remove air and foreign matter in the ink chamber 27, the ejection of ink can be stabilized.

[0028]

According to the present invention, stable ink particle formation can be performed in an ink jet recording apparatus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a nozzle head according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a nozzle head according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a nozzle head according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a nozzle head according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of a nozzle head according to an embodiment of the present invention.

FIG. 7 is a diagram of an orifice plate according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of an ink supply and circulation control device according to an embodiment of the present invention.

FIG. 9 is a diagram showing an apparatus activation method according to an embodiment of the present invention.

FIG. 10 is a diagram showing a particle formation mode in a nozzle according to an embodiment of the present invention.

FIG. 11 is a diagram showing a region where a nozzle in a particle generation mode according to an embodiment of the present invention is generated.

[Explanation of symbols]

Ink containers ... 1, 2 ... Ink pumps, 6 ... Nozzles, 7 ...
Charging electrode, 8: ink particles, 9: upper deflection electrode, 11 ...
Gutter, 26 O-ring, 28 Orifice, 29 Orifice plate, 30 Piston

Continued on the front page (72) Inventor Kenji Asaba 502 Kandate-cho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Seiji Fujikura 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (72) Inventor Akira Miyao 1-1-1 Higashitagacho, Hitachi City, Ibaraki Prefecture F-term (reference) 2C057 AF71 AG17 AG44 BC02 BC08

Claims (9)

[Claims] A nozzle having an orifice section for ejecting ink and a vibrating section for applying vibration to the ink supported only by an elastic member; an ink supply system for supplying ink to the nozzle; and ink particles ejected from the nozzle An ink jet recording apparatus comprising: a charging electrode for charging the electrode; and a deflection electrode for deflecting the charged electrode. 2. A nozzle of an ink jet recording apparatus comprising an orifice section for ejecting ink and a vibrating section for applying vibration to the ink, wherein the vibrating section is supported only by an elastic member. . 3. An ink jet recording apparatus comprising: an orifice section for ejecting ink; and a vibrating section for vibrating the ink, wherein the vibrating section is vibrated in a free vibration mode at both ends. nozzle. 4. An ink jet recording apparatus comprising an orifice section for ejecting ink and a vibrating section for applying vibration to the ink, wherein only one end of the vibrating section is supported by an elastic member. Nozzle. 5. A nozzle of an ink jet recording apparatus comprising an orifice section for ejecting ink and a vibration section for applying vibration to the ink, wherein both ends of the vibration section are supported by elastic members. nozzle. 6. A nozzle of an ink jet recording apparatus comprising an orifice section for ejecting ink and a vibrating section for applying vibration to the ink, wherein the natural frequency of the vibrating section is set to 150 kHz or more. Nozzle. 7. A nozzle of an ink jet recording apparatus comprising an orifice section for ejecting ink and a vibrating section for applying vibration to the ink, wherein the vibrating section is operated at a frequency of 2/3 or less of the natural frequency f of the vibrating section. A nozzle of an ink jet recording apparatus that is driven. 8. A nozzle according to claim 2, wherein said vibrating section comprises a piezoelectric element and a piston member attached in a direction of displacement of said piezoelectric element. 9. A nozzle according to claim 2, wherein said vibrating portion comprises a piezoelectric element and a diaphragm attached in a direction in which said piezoelectric element is displaced.