JP2001105595A - Ink jet recording head and ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent destruction of a nozzle plate and a flow channel plate at their bonding surfaces caused by the temp. change. SOLUTION: A flow channel plate 4 being a silicon single crystal plate is bonded to a rolled plate made of stainless steel and a nozzle plate 6 is minimized in the quantity of linear expansion and contraction caused by a temp. change because the long side direction thereof crosses a rolling direction at a right angle. The pressure chamber 1 and reservoir chamber 2 of the flow channel plate 4 are connected by two-system flow channels formed to the front and rear surfaces of the flow channel plate 4 as grooves. When the ink in the pressure chamber 1 is frozen in low temp. environment, the ink corresponding to volumetric expansion due to freezing escapes from the pressure chamber 1 to the reservior chamber 2 easily through the two-system flow channels and the rise of the pressure in the pressure chamber 1 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a recording head of an ink jet printer.

[0002]

2. Description of the Related Art An ink jet recording head, for example, a recording head of the type that generates ink ejection pressure by using a piezoelectric element, has a plate (hereinafter referred to as a "nozzle plate") having a large number of nozzle holes formed on a front surface facing a sheet. ), And a component having an ink flow path for distributing ink to the nozzle holes (“flow path module”) on the back surface of the nozzle plate.
And a piezoelectric element for applying an ink discharge pressure to the flow path substrate is connected to the back surface of the flow path substrate.

The nozzle plate is generally made of metal, and is typically a stainless steel rolled plate. The channel module bonded to the back surface is made of a material having high rigidity that can withstand a strong impact from the piezoelectric element, typically, silicon.

[0004]

In the manufacturing process of a recording head, generally, in a high temperature atmosphere such as 65.degree. C., an adhesive which cures at such a high temperature is used to bond a nozzle plate and a flow path module. Work such as is performed. On the other hand, the lower limit of the temperature range of the operating environment where the operation of the recording head is required to be guaranteed is about -20 ° C. Therefore, it is required that the recording head does not fail over a wide temperature range of 65 ° C. to −20 ° C.

The first problem here is that the recording head may be destroyed due to the difference in the thermal expansion coefficient between the nozzle plate and the flow path module. In the nozzle plate made of stainless steel and the flow channel module made of silicon, the nozzle plate has a much larger linear expansion coefficient.
Therefore, in a print head assembled in a high-temperature atmosphere of 65 ° C., there is a possibility that the adhesion between the nozzle plate and the flow path module may be broken due to a difference in shrinkage between the nozzle plate and the flow path module, particularly when the environmental temperature is low.

The second problem is that the recording head may be destroyed due to freezing of the ink. Generally, ink for printers freezes in a sherbet-like manner when the temperature drops to about -5 ° C. Among the inks stored in the flow channel module in which the aqueous dye ink or the aqueous pigment ink is used, the ink that is located immediately behind the nozzle is most susceptible to the outside air temperature, and thus starts to freeze first. It is presumed. The location directly behind this nozzle is in a chamber called "pressure chamber" of the flow channel module. When the freezing of the ink starts at this location and the freezing of the ink in the pressure chamber proceeds, the freezing causes the ink to expand in volume and push the wall of the pressure chamber outward, so that the pressure chamber wall and the nozzle plate May be broken.

Accordingly, it is an object of the present invention to prevent the ink jet recording head from being destroyed due to a temperature change.

[0008]

According to a first aspect of the present invention, there is provided an ink jet recording head comprising: a nozzle plate having nozzles for discharging ink; a channel module having an ink channel adhered to the nozzle plate. The nozzle plate is a metal rolling plate having a planar shape with long and short outer dimensions, and the direction of the longer outer dimension of the planar shape of the nozzle plate is substantially orthogonal to the rolling direction.

[0009] The linear expansion coefficient of a metal rolled plate is largest in the rolling direction and smallest in a direction perpendicular to the rolling direction. Therefore, by making the longer direction (typically, the direction of the longer side of the rectangular plate) out of the longer and shorter outer dimensions of the planar shape of the nozzle plate orthogonal to the rolling direction, the line due to the temperature change of the rolled plate is obtained. The amount of expansion and contraction is reduced. Therefore, the bonding surface between the rolling plate and the channel module made of a material having a smaller linear expansion coefficient than the rolling plate,
The risk of breakage due to the difference between the two coefficients of linear expansion is reduced.

An ink jet recording head according to a second aspect of the present invention has a front face and a back face, and has a flow chamber having a pressure chamber, a reservoir chamber, and an ink supply path for supplying ink from the reservoir chamber to the pressure chamber. A flow path module, a nozzle plate adhered to the front surface of the flow path module, and having a nozzle for discharging ink at a position corresponding to the pressure chamber, a vibration plate bonded to the back surface of the flow path module, and the vibration plate And a piezoelectric vibrator in contact with a place corresponding to the pressure chamber on the back of the piezoelectric vibrator. The pressure chamber has a pressure chamber penetrating portion penetrating the flow channel module from the front surface to the rear surface, and a pressure chamber back groove portion formed on the rear surface of the flow channel module as a groove communicating with the pressure chamber penetrating portion. In addition, the ink supply path includes a back side ink supply path formed as a groove connecting the pressure chamber back groove and the reservoir chamber on the back of the flow path module, and a pressure chamber and a reservoir chamber on the front of the flow path module. And a front ink supply path formed as a connecting groove. Both the back ink supply path and the front ink supply path are thinner than the pressure chamber back groove, and the front ink supply path is longer than the back ink supply path.

According to this ink jet recording head,
The pressure chamber and the reservoir chamber are connected through two channels formed as grooves on the front and back surfaces of the channel module. Therefore, when the ink in the pressure chamber freezes in a low-temperature environment, the ink corresponding to the volume expansion of the ink due to the freezing easily flows from the pressure chamber to the reservoir chamber through the two flow paths of the front surface and the back surface. You can escape. as a result,
An increase in the internal pressure of the pressure chamber when the ink is frozen is suppressed, and the destruction of the adhesive surface between the flow path module and the nozzle plate around the pressure chamber is prevented.

In this ink jet recording head, the ink supply path connecting the pressure chamber and the reservoir chamber has a back side ink supply path formed as a groove on the back of the flow path module and a groove on the front side of the flow path module. And the formed front ink supply path. Both the back side ink supply path and the front side ink supply path are thinner than the pressure chamber back groove, and
The front ink supply path is longer than the back ink supply path. According to this flow path configuration, even if two flow paths are provided on the back and front of the flow path module, the volume of the pressure chamber does not become unnecessarily large, so that it is possible to easily cope with high-speed printing. ,
In addition, since the ink flow is particularly good in the flow path on the back side where bubbles are likely to stay, the ability to remove bubbles is also good.

[0013]

FIG. 1 is an exploded perspective view showing the overall configuration of a recording head used in an ink jet printer according to an embodiment of the present invention.

The ink jet printer includes a printhead, a carriage mechanism for moving the printhead, a paper transport mechanism for transporting paper, a drive circuit for driving these mechanisms, and a print image receiving print data from a host device. And a control circuit for controlling the drive circuit, etc., but the components other than these recording heads can be understood by those skilled in the art without particular description, and therefore, the description thereof is omitted in this specification.

The recording head shown in FIG. 1 has a head case 10 made of synthetic resin. The ink jet unit 9 is fixed to the front surface 13 of the head case 10 with an adhesive or the like. The ink jet unit 9 includes a nozzle plate 6, a plate-shaped flow path module (hereinafter, referred to as a flow path plate) 4, and a flexible diaphragm 8, which are laminated and bonded with an adhesive or the like.

The nozzle plate 6 is a stainless steel rolled plate. A large number of nozzle holes 5 are formed in the nozzle plate 6 in a plurality of rows (five rows in this example). The channel plate 4 is made of a silicon single crystal plate. The flow path plate 4 has a number of pressure chambers 1 communicating with a number of nozzle holes 5 of the nozzle plate 6, a reservoir chamber 2 for temporarily storing ink supplied from the head case 10, and a reservoir chamber 2. An ink supply path 3 for sending ink from the pressure chamber 1 to the pressure chamber 1 is formed by etching.

The pressure chambers 1 are arranged in a plurality of rows (five rows in this example) in an arrangement corresponding to the nozzle holes 5, respectively.
The reservoir chamber 2 is formed in a shape elongated in each row of the pressure chambers 1, one chamber in each row. As described later in detail with reference to FIG. 4, the reservoir chamber 2 and the pressure chamber 1
Is formed so as to completely penetrate the flow path plate 4 up and down by full etching, and most of the ink supply path 3 and the pressure chamber 1 are shallow on the upper and lower surfaces of the flow path plate 4 by half etching. It is formed as a groove. The flow path plate 4 further includes the pressure chambers 1 facing each other.
The slits 11 which completely penetrate the flow path plate 4 up and down are provided between the rows.

The diaphragm 8 is a composite plate of a thin synthetic resin sheet and a stainless steel sheet, and has flexibility. The diaphragm 8 is provided with an ink inlet 12 at a position corresponding to the center of the reservoir chamber 2.

The head case 10 is made by injection molding of a thermosetting resin or a thermoplastic resin.
The reservoir chamber 2 is located at a position corresponding to the ink introduction port 12 of the reservoir 3.
An outlet of the ink supply pipe 14 for introducing ink into the ink supply port is provided. In the area corresponding to the reservoir chamber 2,
A recess 15 having a shape substantially matching the shape of the reservoir chamber 2 is formed. Air vent holes 17 extending in the row direction of the nozzle holes 5 are provided on both sides of the ink supply pipe 14 on the bottom surface of the recess 15.
Are drilled through the bottom surface. The recess 15 is a deformation space of the diaphragm 8 that seals the lower opening of the reservoir chamber 2. The pressure fluctuation in the reservoir chamber 2 at the time of ink ejection is absorbed by the deformation of the diaphragm 8.

At the position corresponding to each row of the pressure chambers 1 on the front surface 13 of the head case 10, the front end of the piezoelectric vibrator 7 is
A window 16 for exposing to the outside is formed. The piezoelectric vibrator 7 is fixed inside the head case 10, and the tip of the piezoelectric vibrator 7 is bonded to the diaphragm 8 through the window 16.

FIG. 2 is a plan view of the nozzle plate 6.

The nozzle plate 6 is a rolled plate of stainless steel, has a rectangular plane shape as shown in the drawing, and the direction of the short side thereof matches the rolling direction.
That is, the direction of the long side is orthogonal to the rolling direction. Generally, the linear expansion coefficient of a metal rolling plate is large in the rolling direction,
It is small in the direction perpendicular to it. Therefore, by making the rolling direction perpendicular to the long side direction, the amount of linear expansion and contraction of the nozzle plate 6 due to a temperature change can be minimized.
Therefore, the possibility that the adhesion between the nozzle plate 6 and the flow path plate 4 made of silicon having a much smaller linear expansion coefficient is broken by the linear expansion or contraction due to a temperature change can be minimized.

As shown in FIG. 3, even in the nozzle plate 106 in which the nozzle holes 5 are arranged in a direction different from that of the present embodiment, regardless of the arrangement direction of the nozzle holes 5, the nozzle plate 106 extends in a direction orthogonal to the rolling direction. The long side direction is selected. Further, if a nozzle plate having a plane shape different from a square is used, the longer one of the longer and shorter outer dimensions of the plane shape of the nozzle plate (for example, a triangle or The direction of the longer one of the base and height of the trapezoid, the major axis of the ellipse, etc.) is selected so as to be orthogonal to the rolling direction.

FIG. 4 shows the flow path plate 4 of the recording head.
It is sectional drawing of the part centering on FIG. FIG. 5 is a cross-sectional view of FIG.
FIG. 6 is a sectional view taken along the line A, and FIG. 6 is a sectional view taken along the line BB in FIG. FIG. 4 is a sectional view taken along the line CC of FIGS. 5 and 6.
It is a cross-sectional view along the line (because it was cut along the flow path,
Note that the position of the CC cutting line is partially different between FIG. 5 and FIG. 6).

The ink-jet recording head is generally provided with a recording head shown in FIG.
As shown in the figure, the nozzle holes 5 are arranged in a posture facing downward. As described above, the pressure chamber 1, the reservoir chamber 2, and the ink supply path 3 connecting the pressure chamber 1 and the reservoir chamber 2 are formed in the flow path plate 4.

As shown in FIG. 4, the pressure chamber 1 has a penetrating portion 1a formed through the flow path plate 4 by full etching and a front surface (lower surface in the figure) of the flow path plate 4 by half etching. Front groove 1b formed as a shallow groove
And a back groove portion 1c formed as a shallow groove on the back surface (upper surface in the figure) of the flow path plate 4 by half etching. The through portion 1 a is located behind the nozzle hole 5. A piezoelectric vibrator 7 is provided on a portion of the through portion 1a near the back groove 1 and on the back of most of the back groove 1 via a diaphragm 8.
Vibration is applied.

As shown in FIGS. 5 and 6, each pressure chamber 1 has a width W1 sufficient to match the width of the front surface of the piezoelectric vibrator 7.
have. As shown in FIG. 6, the back groove 1 c has a sufficient length L 1 c corresponding to the length of the front surface of the piezoelectric vibrator 7 and extends near the reservoir chamber 2. On the other hand, as shown in FIG. 5, the length L1b of the front groove portion 1b is much shorter than the back groove portion 1c, and the volume of the front groove portion 1b of the pressure chamber 1 is smaller than that of the back groove portion 1c or the through portion 1a. Much smaller.

The reservoir chamber 2 has a penetrating portion 2a formed through the flow path plate 4 by full etching, a vestibular part 2b formed like a shallow terrace on the front surface of the flow path plate 4 by half etching, A back yard 2c formed as a shallow terrace on the back of the flow path plate 4 by etching.

The ink supply passage 3 is provided with a front groove 1 b of the pressure chamber 1.
The front supply path 3a formed as a shallow groove on the front surface of the flow path plate 4 by half-etching so as to connect the front chamber 2b of the reservoir chamber 2 with the front yard 2b of the reservoir chamber 2; And a back supply path 3b formed as a shallow groove on the back surface of the flow path plate 4 by half-etching so as to connect with the portion 2c. As shown in FIG.
The back supply path 3b is composed of two extremely thin and short flow paths, and the thickness thereof is much smaller than the back groove 1c of the pressure chamber 1 even when the two flow paths are added. As shown in FIG. 5, the front supply path 3a is a thin and long single flow path,
Its length is much longer than the back supply passage 3b, and its thickness is much thinner than the front groove 1a of the pressure chamber 1.

In the above-described flow path configuration, the flow path of the ink from the reservoir 2 to the nozzle holes 5 includes a flow path plate 4
5, that is, as shown in FIG. 5, from the vestibular section 2 b of the reservoir 2 to the pressure chamber 1 through the front supply path 3 a.
The front path leading to the nozzle hole 5 through the front groove 1b and the path passing through the groove on the back side of the flow path plate 4, that is, as shown in FIG. 6, the back supply path 3b from the back yard 2c of the reservoir 2. The back groove 1b of the pressure chamber 1 has a back side path leading to the nozzle hole 5 through the penetrating portion 1 through the back groove 1b. These two routes are
When comparing the flow path resistance (pressure loss) of the two, the front path has a slightly higher resistance than the back path. In other words, the front path has a slightly lower flow of ink than the back path. In order to make the flow resistance of the front path larger than that of the back path, the length of the front supply path 3a of the front path is much longer than that of the back supply path 3b of the back path.

According to the above-described flow path configuration, even in a low-temperature environment where the ink freezes, the ink corresponding to the volume expansion due to the freezing of the ink is effectively released from the pressure chamber 1 and the surroundings of the pressure chamber 1 are reduced. The destruction of the bonded portion between the flow path plate 4 and the nozzle plate 6 can be suppressed. That is, the freezing of the ink will start near the nozzle hole 5 which is most susceptible to the outside air temperature, and will spread into the pressure chamber 1, but in the process, the volume expanded by the freezing of the ink will occur. Ink escapes to the reservoir chamber 2 through the two paths, the front path and the back path. Therefore, even if freezing occurs, the internal pressure of the pressure chamber 1 is unlikely to rise,
The stress applied to the bonded portion is unlikely to be excessive.

As described above, according to the above-described channel structure,
By providing two ink flow paths, a front side path and a back side path, in the flow path plate 4, the problem of breakage of the bonded portion due to freezing is solved. However, when two flow paths are provided in the flow path plate 4, generally, the following two side effects may occur. First, there is a possibility that the volume of the pressure chamber 1 increases and it is difficult to cope with high-speed printing. Second,
There is a possibility that the flow rate of the ink in the flow path decreases, and the ability to remove bubbles from the flow path decreases.

However, according to the above-described flow path configuration, it is possible to maintain the high performance of the recording head while minimizing the above-mentioned side effects. That is, regarding the first point, in order to realize high-speed printing, it is necessary to drive the pressure chamber 1 at a high frequency, and therefore the volume of the pressure chamber 1 needs to be sufficiently small. Generally, since the size of the penetrating portion 1a and the back groove portion 1c of the pressure chamber 1 is determined depending on the size of the piezoelectric vibrator 7, the minimum size that the pressure chamber 1 can have under a given size of the piezoelectric vibrator is obtained. The volume is the penetration 1
a and the back groove 1c. According to the above-described flow path configuration, since the volume of the front groove 1b of the pressure chamber 1 is very small, the volume of the entire pressure chamber 1 is reduced by the penetration 1a.
It is a value close to the volume of the combination of the back groove 1c. That is,
Since the volume of the entire pressure chamber 1 is close to the minimum volume under the given size of the piezoelectric vibrator, it is easy to cope with high-speed driving.

Next, regarding the second side effect, bubbles are
In the flow path plate 4, it is easy to accumulate in the dorsal path located at the highest position. According to the above-described flow path configuration, the ink flows more easily in the back flow path than in the front flow path. Since the ink flows at a high speed in the path, the air bubbles trapped therein can be effectively removed.

As described above, one embodiment of the present invention has been described.
These embodiments are merely examples for describing the present invention, and are not intended to limit the present invention only to these embodiments. Therefore, the present invention can be implemented in various modes other than the above-described embodiment without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the overall configuration of a recording head used in an inkjet printer according to an embodiment of the present invention.

FIG. 2 is a plan view of the nozzle plate of the embodiment.

FIG. 3 is a plan view of another nozzle plate.

FIG. 4 is a sectional view of a portion centering on a flow path plate 4 of the recording head of the embodiment. .

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a sectional view taken along the line BB of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure chamber 1a Penetration part of pressure chamber 1b Front groove part of pressure chamber 1c Back groove part of pressure chamber 2 Reservoir chamber 3 Ink supply path 3a Front side ink supply path 3b Back side ink supply path 4 Flow path plate (flow path module) 5 nozzle Hole 6 nozzle plate 7 piezoelectric vibrator 8 diaphragm

Claims (7)

[Claims] 1. A nozzle plate having nozzles for ink discharge, and a flow path module having an ink flow path adhered to the nozzle plate, wherein the nozzle plate has a planar shape having long and short outer dimensions. An ink jet recording head, which is a metal rolling plate, wherein a direction of a longer outer dimension of a planar shape of the nozzle plate is substantially orthogonal to a rolling direction. 2. The ink jet recording head according to claim 1, wherein said flow channel module is made of a silicon single crystal substrate. 3. An inkjet recording head, a carriage mechanism for moving the recording head, a paper transport mechanism for transporting the paper, a drive circuit for driving these mechanisms, and a print image receiving print data from a host device. And a control circuit for controlling the drive circuit.The recording head includes a nozzle plate having nozzles for ink ejection, and a flow path module having an ink flow path bonded to the nozzle plate. An ink jet printer in which the nozzle plate is a metal rolling plate having a planar shape with long and short outer dimensions, and the direction of the longer outer dimension of the planar shape of the nozzle plate is substantially orthogonal to the rolling direction. 4. The ink jet printer according to claim 3, wherein said flow channel module is made of a silicon single crystal substrate. 5. A flow path module having a front surface and a back surface, having a pressure chamber, a reservoir chamber, and an ink supply path for supplying ink from the reservoir chamber to the pressure chamber, A nozzle plate adhered to the front surface and having an ink discharge nozzle at a position corresponding to the pressure chamber; a diaphragm adhered to the back surface of the flow path module; and a diaphragm corresponding to the pressure chamber on the back surface of the diaphragm. A piezoelectric vibrator in contact with a place where the pressure chamber penetrates, and the pressure chamber communicates with the pressure chamber penetrating part on the back side of the flow path module. A pressure chamber back groove formed as a groove formed in the pressure chamber, wherein the ink supply path is formed as a groove connecting the pressure chamber back groove and the reservoir chamber on a back surface of the flow path module. Groove A thinner back-side ink supply path, formed on the front face of the flow path module as a groove connecting the pressure chamber and the reservoir chamber, and thinner than the back-side ink supply path of the pressure chamber and longer than the back-side ink supply path. An ink jet recording head having a front ink supply path. 6. An inkjet recording head, a carriage mechanism for moving the recording head, a paper transport mechanism for transporting the paper, a drive circuit for driving these mechanisms, and a print image receiving print data from a host device. And a control circuit for controlling the drive circuit, wherein the recording head has a front surface and a back surface, a pressure chamber, a reservoir chamber, and ink for supplying ink from the reservoir chamber to the pressure chamber. A flow path module having a supply path; a nozzle plate bonded to a front surface of the flow path module and having a nozzle for discharging ink at a position corresponding to the pressure chamber; and a flow path module bonded to a back surface of the flow path module. A vibration plate, and a piezoelectric vibrator in contact with a position corresponding to the pressure chamber on the back surface of the vibration plate, wherein the pressure chamber is in front of the flow path module. And a pressure chamber back groove formed as a groove communicating with the pressure chamber through section on the back of the flow path module, wherein the ink supply path is formed by a flow path module. A back side ink supply path formed as a groove connecting the pressure chamber back groove and the reservoir chamber on the back side of the pressure chamber; and a back side ink supply path smaller than the pressure chamber back groove, and the pressure chamber and the reservoir on the front side of the flow path module. An ink-jet printer having a front ink supply path formed as a groove connecting the chambers, the front ink supply path being thinner than the pressure chamber back groove and longer than the back ink supply path. 7. The ink jet printer according to claim 6, wherein the ink used for the recording head is an aqueous dye ink or an aqueous pigment ink.