JP2002347240A - Ink jet head and ink-jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head and an ink-jet recorder which can drive with a small consumption of power and a low energy, can discharge a high- viscosity ink and have ink discharge characteristics improved. SOLUTION: The ink jet head has a head chip and a negative pressure- adjusting part 60. The head chip discharges ink filled inside grooves from nozzle openings by impressing a driving voltage to electrodes set to side walls of the grooves formed to a piezoelectric ceramic plate, and changing the volume in the grooves. The negative pressure-adjusting part 60 has a film-shaped body 70 set in the middle of an ink supply path for supplying ink to the head chip and partly formed of an elastic member. A heater 80 for heating ink in the negative pressure-adjusting part 60 is set to an outer face of the negative pressure-adjusting part 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet head and an ink jet recording apparatus applied to, for example, a printer and a facsimile.

[0002]

2. Description of the Related Art An ink jet recording apparatus for recording characters and images on a recording medium using an ink jet head for discharging ink from a plurality of nozzles has been known. This ink jet recording apparatus prints a dot pattern in a predetermined area by discharging ink from nozzles of the ink jet head while moving a carriage on which the ink jet head is mounted with respect to a recording medium in a main scanning direction, and printing once. When the main scanning is completed, the recording medium is moved by a predetermined amount in the multiple scanning direction, and these operations are repeated to print all desired areas.

In such a conventional ink jet recording apparatus, ink ejection with low power consumption and low energy is always pursued. For this reason, it is desirable to set the ink viscosity to be low, and it is usually about 10 mPa ·
We aim to discharge at a viscosity of s.

However, since the physical properties (particularly, ink viscosity) of the ink to be ejected greatly change depending on the environmental temperature, it is impossible to eject the ink when the ejection performance deteriorates with respect to normal temperature.

For this reason, conventionally, the head drive voltage has been varied according to the environmental temperature, and controlled so as to obtain the target ink droplet discharge speed and discharge performance such as ink volume.

[0006]

However, when controlling the drive voltage of the head in accordance with the environmental temperature, the control voltage is set higher because the ink viscosity increases significantly at a low temperature, and the power supply variable range is inevitably widened. And the need for excessive capacity.

Further, when the value of the ink viscosity itself at normal temperature is high, the initial control voltage at normal temperature is set to be high, so that there is a problem that low power consumption and low energy cannot be realized.

Further, in such an ink jet head, the viscosity of ink that can be ejected is 3 mPa · s to 10 mP.
For example, in order to eject a high-viscosity (10 mPa · s to 50 mPa · s) ink such as a radiation curable ink, the ink must be driven with a high voltage and a long voltage application time. However, there is a problem that the ink jet head is broken or durability is deteriorated.

In view of such circumstances, the present invention provides an ink jet head and an ink jet recording apparatus which can be driven with low power consumption and low energy, can discharge high viscosity ink, and have improved ink discharge characteristics. Make it an issue.

[0010]

According to a first aspect of the present invention for solving the above-mentioned problems, a driving voltage is applied to an electrode provided on a side wall of a groove formed in a piezoelectric ceramic plate to thereby form a piezoelectric element in the groove. A head chip that changes the volume and discharges the ink filled therein from the nozzle opening,
An outer surface of the negative pressure adjusting unit, wherein the negative pressure adjusting unit is provided in the middle of an ink supply path for supplying ink to the head chip, and has a negative pressure adjusting unit partially provided with a film-like body made of an elastic member. And a heater for heating the ink in the negative pressure adjusting section.

According to a second aspect of the present invention, in the ink jet head according to the first aspect, a concave portion is provided on an outer surface of the negative pressure adjusting portion, and the heater is attached to the concave portion. It is in.

A third aspect of the present invention is the ink jet head according to the first or second aspect, wherein the heater is a planar heater.

According to a fourth aspect of the present invention, in any one of the first to third aspects, at least one of the negative pressure adjusting section and the heating means detects an ink temperature in the negative pressure adjusting section. Means for providing an ink jet head.

A fifth aspect of the present invention is the ink jet head according to any one of the first to fourth aspects, wherein the ink is a radiation-curable ink.

According to a sixth aspect of the present invention, there is provided an ink jet recording apparatus comprising the ink jet head according to any one of the first to fifth aspects.

In the present invention, by heating the ink in the negative pressure adjusting unit by the heater, ink having a desired ink viscosity can be discharged regardless of the environmental temperature, and the ink discharge characteristics can be improved. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments of the present invention.

(Embodiment 1) FIG. 1 is a perspective view of an ink jet head according to Embodiment 1, FIG. 2 is a sectional view of a main part of the ink jet head, FIG. 3 is an exploded perspective view of a head chip, and FIG. It is a perspective sectional view.

As shown in the figure, the ink jet head 10 of the present embodiment has a head chip 20, a flow path substrate 30 provided on one side thereof, a drive circuit for driving the head chip 20, and the like. And a wiring board 40, and each of these members is fixed to the base plate 50.

The piezoelectric ceramic plate 21 constituting the head chip 20 has a plurality of grooves 2 communicating with the nozzle openings.
2 are arranged side by side, and each groove 22 is isolated by a side wall 23. One end of each groove 22 in the longitudinal direction extends to one end surface of the piezoelectric ceramic plate 21, and the other end does not extend to the other end surface, but gradually decreases in depth. In addition, electrodes 24 for applying a driving electric field are formed on the side walls 23 on both sides in the width direction of each groove 22 on the opening side of the groove 22 in the longitudinal direction.

Each groove 22 formed in the piezoelectric ceramic plate 21 is formed by, for example, a disk-shaped die cutter, and a portion whose depth is gradually reduced is formed by the shape of the die cutter. The electrodes 24 formed in the respective grooves 22 are formed, for example, by vapor deposition from a known oblique direction.

The groove 2 of the piezoelectric ceramic plate 21
The ink chamber plate 25 is joined to the opening side of the second. In the ink chamber plate 25, a common ink chamber 26 formed therethrough is provided over the entire groove 22 arranged side by side.

The ink chamber plate 25 can be formed of a ceramic plate, a metal plate, or the like. However, considering deformation after joining with the piezoelectric ceramic plate 21, a ceramic plate having an approximate coefficient of thermal expansion should be used. Is preferred.

A nozzle plate 27 is joined to the end face of the joined body of the piezoelectric ceramic plate 21 and the ink chamber plate 25 where the groove 22 is open, and the nozzle plate 27 is opposed to each groove 22 of the nozzle plate 27. Is formed with a nozzle opening 28.

In the present embodiment, the nozzle plate 27
The groove 22 of the joined body of the piezoelectric ceramic plate 21 and the ink chamber plate 25 is larger than the area of the open end face. The nozzle plate 27 is formed by forming a nozzle opening 28 in a polyimide film or the like by using, for example, an excimer laser device. Although not shown, a water-repellent film having a water-repellent property is provided on the surface of the nozzle plate 27 that faces the printing object, for preventing the adhesion of ink and the like.

In this embodiment, the groove 22 of the joined body of the piezoelectric ceramic plate 21 and the ink chamber plate 27 is used.
The nozzle support plate 2
9 are arranged. This nozzle support plate 29
It is joined to the outside of the end face of the joined body of the nozzle plate 27, and is formed by fitting and bonding the nozzle support plate 29 to the outside surface of the nozzle plate 27 and the joined body of the piezoelectric ceramic plate 21 and the ink chamber plate 25. .

A channel substrate 30 as shown in FIG. 2 is joined to one surface of the ink chamber plate 25, and one surface of the common ink chamber 26 is sealed by the channel substrate 30. Specifically, the flow path substrate 30 is in contact with one surface of the ink chamber plate 25 via, for example, an O-ring or the like, and is fixed to the base plate 50 by a screw member (not shown) or the like.

On the upper surface of the flow path substrate 30, there is formed a connecting portion 31 to which an ink communication tube 100 formed of a stainless steel tube or the like is connected. At the other end of the ink communication pipe 100, one end of which is connected to the connecting portion 31, a negative pressure for temporarily storing a predetermined amount of ink, which is connected to an ink tank such as an ink cartridge via an ink supply pipe 101, is provided. An adjusting unit 60 is provided.

This negative pressure adjusting section 60
The pressure of the ink in the common ink chamber 26 and the groove 22 is adjusted. Specifically, the inkjet head 10
When moves in the main scanning direction, the pressure in the head chip 20 changes, and there is a possibility that the meniscus formed by the surface tension of the ink in the nozzle openings 28 may be destroyed.
By adjusting the pressure change in the head chip 20 by the negative pressure adjusting unit 60, it is possible to discharge ink while maintaining a stable meniscus. Further, the negative pressure adjusting section 60 stores a predetermined amount of ink therein, so that bubbles in the ink supply pipe 101 are removed from the head chip 20.
It also contributes to the retention of air bubbles to prevent contamination.

The negative pressure adjusting section 60 will be described in detail. FIG. 4 is a plan view of the negative pressure adjusting unit.
FIG. 5 is a sectional view taken along the line AA ′ and a sectional view taken along the line BB ′ of FIG.

As shown in the figure, the negative pressure adjusting section 60 includes an adjusting section main body 62 having an ink storing section 61 formed of a concave portion for holding ink, and an ink storing section 61 provided on one surface of the adjusting section main body 62. A film member 70 to be sealed, and an ink storage unit 6 provided on the outer surface of the other surface of the adjustment unit main body 62.
And a planar heater 80 for heating the ink in the ink jet printer 1.

The adjusting section main body 62 is provided with a filling path 63 for supplying ink from the ink tank to fill the ink storing section 61 with ink, and a head chip 20 from the ink storing section 61.
And a supply path 64 for supplying ink to the printer.

The other end of the ink supply pipe 101 made of a flexible tube such as rubber or plastic, one end of which is connected to the ink tank, is connected to the filling path 63 via a joint member 65.

That is, the ink from the ink tank is
Ink supply pipe 101, joint member 65 and filling path 6
The ink reservoir 61 is filled with the ink through the ink reservoir 3.

A filter 66 is provided at one end of the supply path 64 provided in the negative pressure adjusting section 60. The filter 66 removes minute dust and air bubbles, and is connected to the other end. The ink is supplied to the common ink chamber 26 via the ink communication pipe 100 that has been set.

On one side of the adjusting section main body 62,
A film member 70 for sealing the ink storage section 61 is adhered.

The film member 70 can be made of an elastically deformable member such as a polyimide resin or an epoxy resin.

The film member 70 is connected to the adjusting section main body 6.
The second ink reservoir 61 is adhered to the opening edge without any gap, so that the air and ink inside do not leak. The method of bonding the film member 70 to the adjustment unit main body 62 is not particularly limited, but in the present embodiment, the film member 70 is bonded by heat welding.

The ink reservoir 61 of the negative pressure regulator 60 is filled with substantially half the ink in the ink reservoir 61 in order to adjust the pressure of the ink in the head chip 20. As will be described in detail later, when the inkjet head 10 moves in the main scanning direction, the head chip 20
A pressure change occurs in the ink inside. At this time, a substantially constant negative pressure can be applied to the ink in the head chip 20 by elastically deforming the film member 70 with a change in pressure, that is, by changing the volume of the ink storage section 61.

Further, the filling of the ink into the ink storing section 61 is performed by sucking the ink from the nozzle opening 28 of the head chip 20. At this time, the air in the ink storage section 61 is sucked, and the film member 70 is moved to the ink storage section 6.
If it adheres to the bottom surface of the ink cartridge 1, the ink is filled in the ink storing portion 61 without any gap, and the negative pressure of the ink in the head chip 20 cannot be adjusted. For this reason,
A damper plate 71 formed of a plate-like member that restricts the film member 70 from contacting the bottom surface of the ink storage unit 61 is provided in the ink storage unit 61 of the negative pressure adjustment unit.

The damper plate 71 is made of an elastically deformable member, for example, stainless steel, and has a projection 71 a projecting in the vertical direction of the negative pressure adjusting section 60.

The damper plate 71 is connected to the ink storing section 6
1, the protrusion 71a of the damper plate 71 regulates the contact of the film member 70 with the bottom surface of the ink storage portion 61, so that a predetermined amount of ink is filled. ing.

The arrangement of the damper plate 71 at the predetermined position is achieved by forming the front end and the rear end of the damper plate 71 at the notch 67 provided at the opening edge of the adjusting section main body 62 where the ink storage section 61 opens. It is defined by engaging and thermally welding the film member 70 to the opening edge of the adjustment portion main body 62. Thereby, the damper plate 71 is attached to the adjustment unit main body 6.
2 and the film member 70 without a gap, and a predetermined space can be formed in the ink storage section 62.

Further, the film member 70 of the adjusting portion main body 62
A concave portion 68 is provided on the outer surface of the surface opposite to the above, and a planar heater 80 for heating the ink in the ink storing portion 61 is provided on the bottom surface of the concave portion 68.

In the ink storage section 61 of the negative pressure adjusting section 60, substantially half of the space of the ink is held, so that the sheet heater 80 is provided on the bottom surface so that the sheet heater 80 can easily heat the ink. The provided concave portion 68 is provided at a position facing the ink of the adjusting portion main body 62, that is, at a lower side.

The planar heater 80 is connected to the ink storage section 6.
There is no particular limitation as long as the ink in 1 can be heated, and examples thereof include a polyimide heater, a ceramic heater, a mica heater, and an aluminum heater.

By driving such a planar heater 80 by, for example, an external power supply, the ink in the ink storage section 61 can be heated via the adjustment section main body 62 and can be controlled to a predetermined ink viscosity. .

A temperature sensor 81 for detecting the temperature of the ink in the ink storage unit 61 is provided on at least one of the outer surface of the negative pressure adjusting unit 60 near the planar heater 80 and the inside of the ink storage unit 61. In the present embodiment, the detection sensor 81 is provided in the ink storage unit 61 of the negative pressure adjustment unit 60. Specifically, the detection sensor 81 is provided on the lower surface of the adjustment unit main body 62 so as to be always immersed in the ink in the ink storage unit 61. Thus, the detection sensor 81 can accurately detect the ink temperature in the ink storage section 61.

The negative pressure adjusting section 60 provided with the planar heater 80 and the detection sensor 81 is held on the base plate 50 by a holding member 72. The holding member 72 has an arm 72 a that holds the ink supply pipe 101 and prevents the ink supply pipe 101 from coming off the joint 65.

As described above, in the negative pressure adjusting section 60, the detection sensor 81 detects the ink temperature of the ink storage section 61, and based on the detection result, for example, the control means for controlling the printing operation and the like is controlled by an external power supply or the like. By controlling the planar heater 80, the ink in the ink storage unit 61 can be controlled to a desired temperature and supplied to the head chip 20.

The ink jet head 10 having the negative pressure adjusting section 60 provided with such a planar heater 80 is also provided.
In this case, since the ink viscosity can be made substantially constant by controlling the temperature of the ink, the ink discharge voltage can be set lower and there is no need to variably control the voltage in accordance with the environmental temperature. Therefore, it can be driven with low power and low energy. In addition, since a low-capacity power supply can be mounted as a driving power supply, it can be manufactured at low cost.
Furthermore, by making the ink viscosity substantially constant, it is possible to improve the ink ejection characteristics and improve print quality and print reliability.

Further, in the ink jet head 10 of the present embodiment, the ink temperature can be controlled by providing the planar heater 80 in the negative pressure adjusting section 60.
For example, a high-viscosity ink such as a radiation-curable ink can be used.

Here, a high-viscosity ink at 20 ° C.
FIG. 6 shows the relationship between the ink viscosity and the temperature of the 5 mPa · s ultraviolet curable ink. The dotted line in the drawing indicates the viscosity range (approximately 30 mPa · s or less) that can be ejected from the inkjet head 10 of the present embodiment.

As shown, 45 mPa · s at 20 ° C.
By heating the ink temperature to approximately 50 ° C., the UV-curable ink can reduce the ink viscosity to a dischargeable viscosity of 30 mPa · s or less.

As described above, even if the ink has a high viscosity,
By providing a planar heater 80 in the negative pressure adjusting unit 60 of the inkjet head 10 and controlling the temperature of the ink in the negative pressure adjusting unit 60, the ink viscosity in the ink storage unit 61 is reduced, and the high viscosity Ink can be ejected.

For this reason, printing can be performed at low cost on an object to be printed such as a CD or DVD, which has been conventionally performed by screen printing, by using the ink jet head 10 using a radiation curable ink such as an ultraviolet curable ink.

The ink jet head 10 having the negative pressure adjusting section 60 provided with such a planar heater 80 is also provided.
Is used, for example, mounted on a carriage of an ink jet recording apparatus.

Here, the ink jet recording apparatus will be described. FIG. 7 is a perspective view of a carriage on which an inkjet head is mounted, and FIG. 8 is a schematic perspective view of an inkjet recording apparatus.

As shown in the figure, a plurality of ink jet heads 60 provided for each color, a carriage 110 on which a plurality of ink jet heads 10 are mounted in parallel in the main scanning direction, and an ink supply pipe 101 made of a flexible tube. And an ink cartridge 111 for supplying ink through the carriage 110. The carriage 110 is mounted on a pair of guide rails 112a and 112b so as to be movable in the axial direction. Also, guide rails 112a, 112b
A drive motor 113 is provided on one end side of the drive motor.
3 and a guide rail 112
a and 112b are moved along a timing belt 115 stretched over a pulley 114b provided on the other end side.

The guide rails 112a, 112a are provided at both ends of the carriage 110 in the direction perpendicular to the carrying direction.
2b, a pair of transport rollers 116, 117
Is provided. These transport rollers 116, 117
Transports the recording medium S below the carriage 110 in a direction orthogonal to the transport direction of the carriage 110.

The transport rollers 116, 117
By scanning the carriage 110 in a direction orthogonal to the feeding direction while feeding the recording medium S, characters, images, and the like are recorded on the recording medium S by the inkjet head 10.

Although the pressure of the ink in the head chip 20 of the ink jet head 10 fluctuates due to the movement of the carriage 110, the pressure can be easily adjusted by providing the ink jet head 10 with the negative pressure adjusting unit 60. Discharge of the ink can be executed.

The ink jet head 10 of the present embodiment is for discharging a single color ink. In the present embodiment, four inks of black (B), yellow (Y), magenta (M), and cyan (C) are used. Four are arranged in parallel corresponding to the colors and mounted on the carriage 110.

Further, four ink cartridges 111 are provided for each color corresponding to each ink jet head 10. Such an ink cartridge 111 is positioned so as not to hinder the movement of the carriage 76 in the main scanning direction or the movement of the recording medium S, and to apply a negative pressure to the inkjet head 10 so as to apply a negative pressure to the inkjet head 10.
It is provided at a position lower than the nozzle opening of No. 0 by a predetermined amount.

(Other Embodiments) Although the first embodiment of the present invention has been described above, the ink jet head and the ink jet recording apparatus of the present invention are not limited to such a configuration.

For example, in the above-described first embodiment, the Saar type ink jet head 10 has been described as an example. However, the present invention is not limited to this. For example, a serial ink jet head such as a bubble jet (registered trademark) type ink jet head is scanned. It is needless to say that the present invention can be applied to an ink jet recording apparatus of the type.

Further, for example, when the temperature of the ink in the negative pressure adjusting unit 60 becomes a predetermined temperature or more due to driving heat or the like,
A cooling means for lowering the ink temperature of the ink in the negative pressure adjusting section 60 and the ink in the head chip 20 may be provided.

[0068]

As described above, according to the present invention, by providing a heater on the outer surface of the negative pressure adjusting unit, the heater controls the temperature of the ink in the negative pressure adjusting unit to adjust the ink viscosity. it can. Therefore, low power consumption,
The ink can be driven with low energy and can discharge high-viscosity ink, and the ink discharge characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an inkjet head according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view of a main part of the inkjet head according to the first embodiment of the present invention.

FIG. 3 is an exploded perspective view and a perspective sectional view of a head chip according to the first embodiment of the present invention.

FIG. 4 is a plan view of a negative pressure adjusting unit according to the first embodiment of the present invention.

5A is a cross-sectional view of the negative pressure adjusting unit according to the first embodiment of the present invention, FIG. 5A is a cross-sectional view taken along line AA ′ of FIG. 4, and FIG.
FIG. 6 is a sectional view taken along line BB ′ of FIG. 4.

FIG. 6 is a diagram illustrating a relationship between temperature and viscosity of the ultraviolet curable ink according to the first embodiment of the present invention.

FIG. 7 is a perspective view of the carriage according to the first embodiment of the present invention.

FIG. 8 is a schematic perspective view of the ink jet recording apparatus according to the first embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 inkjet head 20 head chip 30 flow path substrate 40 wiring substrate 50 base plate 60 negative pressure adjusting unit 61 ink storing unit 62 adjusting unit main body 70 film member 71 damper plate 72 holding member 80 planar heater 81 detection sensor 100 ink communication tube 101 ink Supply tube 110 Carriage 111 Ink cartridge

Claims (6)

[Claims] 1. A drive voltage is applied to an electrode provided on a side wall of a groove formed in a piezoelectric ceramic plate to change a volume in the groove and discharge ink filled therein from a nozzle opening. An ink jet head comprising: a head chip; and a negative pressure adjusting unit provided in the middle of an ink supply path for supplying ink to the head chip and partially provided with a film-shaped body made of an elastic member. An ink jet head comprising a heater for heating the ink in the negative pressure adjusting unit on an outer surface of the adjusting unit. 2. The ink jet head according to claim 1, wherein a concave portion is formed on an outer surface of the negative pressure adjusting portion, and the heater is attached to the concave portion. 3. The ink jet head according to claim 1, wherein the heater is a planar heater. 4. The apparatus according to claim 1, wherein at least one of said negative pressure adjusting section and said heating means is provided with a detecting means for detecting an ink temperature in said negative pressure adjusting section. An inkjet head according to any one of the above. 5. The ink jet head according to claim 1, wherein said ink is a radiation curable ink. 6. An ink jet recording apparatus comprising the ink jet head according to claim 1.