JP3213861B2 - Inkjet recording head - Google Patents

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 head for forming an ink image on a recording medium such as recording paper.

[0002]

2. Description of the Related Art In an ink jet recording head which pressurizes ink in a pressure chamber by utilizing the displacement of a piezoelectric element and discharges ink droplets from nozzles communicating with the pressure chamber, the pressure is increased by utilizing the contraction and expansion of the piezoelectric element. In an ink jet recording head that pressurizes a chamber and discharges ink, one end or a part of the surface of the piezoelectric element is bonded or fixed, and stable contraction and expansion is performed to obtain sufficient pressure in the pressure chamber to discharge ink. Need to be secured.

Generally, in an ink jet recording head, unless one end of a piezoelectric element is firmly joined to a supporting member, it is impossible to stably secure a target displacement. For this reason, the joining between the piezoelectric element and the member fixing the piezoelectric element has to be performed in as large an area as possible in order to strengthen the joining.

However, the piezoelectric element and the member that joins the piezoelectric element are not necessarily the same member. If the coefficients of thermal expansion of the two members are greatly different, the amount of thermal deformation is different, and the larger the area of the joint is, the more likely it is to cause warpage. Therefore, the members must be selected so that the thermal expansion coefficients of both members are substantially equal, and the degree of freedom of design is often narrowed.

For this reason, as shown in Japanese Patent Application Laid-Open No. 4-234661, it is necessary to join a piezoelectric element and its fixing member via a second fixing member having substantially the same coefficient of thermal expansion as that of the piezoelectric element. Was.

FIG. 7 is a sectional view schematically showing the structure of a conventional ink jet recording head disclosed in Japanese Patent Application Laid-Open No. Hei 4-234661.

In FIG. 1, a nozzle 10 is provided in a flow path substrate.
1, an ink flow path formed by communication between the pressure chamber 105 and the ink supply port 106 is formed. Further, the tip of the piezoelectric element 122 is fitted into the pressure chamber 105 of the flow path substrate 107, sealed by a sealing member 130, and sealed so that the piezoelectric element 122 can slide. The rear end of the piezoelectric element 122 is a support member 12 serving as a second fixing member.
1 and is fixed to the fixing member 111.

According to the above configuration, the tip of the piezoelectric element 122 expands and contracts by applying an electric field to the piezoelectric element 122, and pressurizes the ink in the pressure chamber 105 to form the nozzle 1.
02 ejects ink.

[0009]

FIG. 8 is a diagram showing a state of thermal expansion deformation of a conventional ink jet recording head.

As in the conventional ink jet recording head, a supporting member 121 and a piezoelectric element 122 which are second fixing members are provided.
Even if the members have substantially the same coefficient of thermal expansion, the warping problem cannot be solved unless the supporting members 121 and the fixing member 111 as the second fixing members have the same coefficient of thermal expansion. In the configuration where the support member 121 and the fixing member 111 as in the prior art are joined in its entire surface area to be bound to each other by bonding wide enough, and the thermal expansion coefficient of the two members are different as joint warping large There is a problem that it becomes easier.

When this warpage occurs, the support member 121
If the bonding strength between the fixing member 111 and the fixing member 111 is not sufficient, there is a possibility that the bonding may be peeled off, or even if the bonding strength is sufficient, the influence of the warpage may reach the flow path substrate 107 and the flow path substrate 107 may be warped or broken. is there. For this reason, the dimensions of the ink flow path in the flow path substrate 107 change, and the original ink discharge characteristics cannot be obtained, ink does not discharge in the original discharge direction, ink leaks from the ink flow path, and a discharge failure occurs. Or cause. As a result, there has been a problem that stable ink ejection characteristics cannot be secured and high print quality cannot be secured.

The longer the supporting length L of the piezoelectric element 122, the greater the amount of displacement when a voltage is applied. For this reason, the volume of the pressure chamber 105 can be changed more greatly, and an ink droplet with a larger amount of ink can be ejected.

However, the longer the supporting length L of the piezoelectric element 122 is, the more stress is applied to the piezoelectric element 122 under the influence of the warp when the supporting member and the fixing member warp, and the supporting of the piezoelectric element 122 There is a possibility that a predetermined amount of deformation may not be secured due to peeling from the member 111. Further, when the warpage increases and the stress applied to the piezoelectric element 122 increases, the piezoelectric element 122 may be broken.

For this reason, the support length L of the piezoelectric element 122 cannot be increased, and the length L is restricted. Therefore, the degree of freedom in design is lost, and the discharge characteristics of a predetermined amount of ink cannot be aimed at. There were also problems.

From the above problems, the above-described support substrate 1
In order to minimize the warpage of the fixing member 111 and the fixing member 111, there is a restriction that members having similar thermal expansion coefficients must be joined to each other, resulting in a problem that the degree of freedom of design is extremely reduced.

Accordingly, the present invention is to solve such a conventional problem. It is an object of the present invention to reduce the warpage caused by the difference in the coefficient of thermal expansion, to secure stable ejection characteristics, An object of the present invention is to provide an ink jet recording head that does not impair the degree of freedom in design.

[0017]

To achieve the above object, the present invention provides a piezoelectric element and a flow path substrate having a pressure chamber opposed to the piezoelectric element via a pressure plate,
An ink jet recording head for ejecting ink droplets from a nozzle communicating with the pressure chamber due to a change in volume of the pressure chamber due to displacement of the piezoelectric element, wherein the fixing member has the flow path substrate joined thereto, and is bonded to the fixing member. And a support substrate to which the rear end of the piezoelectric element is fixed in a state where the front end of the piezoelectric element is in contact with the pressure plate. A plurality of grooves are arranged in parallel, and a plurality of convex surfaces divided by the grooves are formed as the bonding surfaces.

A plurality of the grooves are arranged in a direction perpendicular to the piezoelectric element displacement direction.

A plurality of the grooves are arranged in a piezoelectric element displacement direction.

The grooves are arranged in a lattice shape in a direction perpendicular to the direction of displacement of the piezoelectric element.

[0021]

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an embodiment to which the present invention is applied. FIG. 2 is a partial sectional view showing this embodiment in detail.

In these figures, reference numeral 1 denotes a nozzle plate. The nozzle plate 1 has a plurality of nozzles 2. 3 is a wall member. The wall member 3 is sandwiched between the nozzle plate 1 and a pressure plate 8 serving as an elastic wall to form an ink supply chamber 4 and a pressure chamber 5. The pressure plate 8 includes a thin portion 8a and an island-shaped portion 8b. The flow path substrate 7, which is formed by laminating and joining the pressure plate 8, the wall member 3, and the nozzle plate 1, is tightly joined on the fixing member 11.

The laminated piezoelectric element 22 serving as a driving source for ejecting ink droplets is provided with a support substrate 2 so as to protrude L in the longitudinal direction.
1 is joined to the pressure plate 8 at the tip of the portion not fixed. The wiring pattern 24 is provided on the support substrate 21.
And an electric field controlled by the control board 13 is applied to the piezoelectric element 22 via the lead frame 25. Reference numeral 12 denotes a mounting hole that penetrates through the inside of the fixing member 11, and supports the support substrate 21 in order to determine the position of the piezoelectric element 22 in the X and Y directions (see XYZ coordinates in FIG. 1). Note that the Z of the piezoelectric element 22
After joining the pressure plate 8 to the fixing member 11, the direction is determined by contacting the tip of the piezoelectric element 22 with the island portion 8 b of the pressure plate 8.

Reference numeral 31 denotes an ink supply pipe for supplying ink from an ink tank (not shown). The ink supply pipe 31 is press-fitted and adhered to the fixing member 11. The ink flow path communicates with the ink supply chamber 4, the ink supply port 6, and the pressure chamber 5 of the wall member 3 through the ink connection port 32 of the fixing member 11 and the ink communication port 33 of the pressure plate 8. I have. The above is the schematic configuration.

The structure will be described in more detail with reference to FIG. The positive electrode 41 and the negative electrode 42 of the piezoelectric element 22 face each other. The positive electrode 41 is connected to the wiring pattern 24 on the support substrate 21.
And are electrically connected at the same time. The negative electrode 42 is electrically connected to the wiring pattern 24 on the support substrate 21 by the common electrode plate 23. The wiring pattern 24 and the control board 13 are connected by a lead frame 25, and the connection portions are fixed by solder.

The support substrate 21 is bonded and fixed to the fixing member 11 with the piezoelectric element 22 in contact with the island portion 8a of the pressure plate 8. The bonding surface of the fixing member 11 of the support substrate 21 is
Parallel to the direction of displacement of the
A plurality of characteristic grooves 26 are arranged.
Therefore, the plurality of divided convex surfaces 21 a and the surface of the fixing member 11 are fixed by the adhesive 10.

The pressure chamber 5, the ink supply port 6, and the common ink chamber 4, which are filled with ink, are formed by joining the wall member 3, the nozzle plate 1, and the pressure plate 8. The wall member 3 is formed by exposing a photosensitive resin. The nozzle plate 1 covering the upper surface of the wall member 3 has a plurality of pressure chambers 5 formed by pressing or the like.
And a stainless steel plate in which one nozzle 2 is opened.

The pressure plate 8 covering the lower surface of the wall member 3
Is formed by forming a thin portion 8a and an island-shaped portion 8b formed to a thickness of 5 μm or less by a nickel electroforming method. As shown in FIG. 2, the tip of the piezoelectric element 22 is joined to the island portion 8b. The island portion 8b is designed to be slightly smaller than the projection surface of the pressure chamber 5.

With the above configuration, the following ink droplet discharging operation is performed. This will be described below.

In response to the print signal, the piezoelectric element 22 is passed from the control board 13 through the lead frame 25 and the wiring pattern 24.
An electric field is applied to the positive electrode 41 and the negative electrode 42. The piezoelectric element 22 to which the electric field is applied tends to contract in the longitudinal direction (vertical direction in the figure). At this time, since the lower portion of the piezoelectric element 22 is fixed to the support member 21 fixed to the fixing member 11, the piezoelectric element 22 cannot be contracted and displaced. On the other hand, the length L of the piezoelectric element 22
Is contracted and displaced without being restrained, and the contraction force pulls the pressure plate 8. As a result, the pressure plate 8 pulled by the piezoelectric element bends downward, and as a result, the volume of the pressure chamber 5 expands. When the ink chamber expands, ink flows from the common ink chamber 4 through the ink supply port 6.
Next, when the electric field of the piezoelectric element 22 is released, the piezoelectric element 2
2 compresses the pressure chamber 5 by expanding displaced to its original length. An ink droplet is ejected from the nozzle 2 at this pressure. Piezoelectric element 22
Since the island portion 8b of the pressure plate 8 which transmits the displacement of the pressure chamber 8 to the pressure chamber is slightly smaller than the projection surface of the pressure chamber 5 as described above,
The pressure chamber is uniformly pressurized and depressurized while leaving the bent portion of the thin portion 8a.

FIG. 3 is an enlarged sectional view showing a first joining state of the supporting substrate and the fixing member.

In the figure, the convex surface 21 a of the support substrate 21 and the surface of the fixing member 11 are joined via an adhesive 10.

According to the above configuration, since the joining is performed at the convex surface 21a, the joining area can be reduced as compared with the conventional entire surface by adhesive joining. For this reason, the portion where the support substrate 21 and the fixing member 11 are restrained by bonding can be reduced, and even if the difference in thermal expansion coefficient between the support substrate 21 and the fixing member 11 is large, the
Then, the warpage of the fixing member 11 becomes minute, and peeling at the bonding portion can be suppressed.

Further, since the warp between the support substrate 21 and the fixing member 11 is very small, the influence of the warp does not affect the flow path substrate 7 formed by joining the nozzle plate 1, the wall member 2, and the pressure plate 8. In addition, the deformation and destruction of the flow path substrate 7 do not occur.

Further, even if the amount of the adhesive 10 is larger than a predetermined amount sufficient for bonding the convex surface 21a, an extra amount of the adhesive 10 escapes into the groove 26, so that the bonding surface is limited to the convex surface 21a only. it can. Therefore, the bonding area is controlled by the convex surface 21.
Only the area of “a” needs to be managed, and the support substrate 21 and the fixing member 1
Measures for warpage can be easily made according to the shape, material, etc. of (1).

On the other hand, with respect to the piezoelectric element 22, the warpage between the support substrate 21 and the fixing member 11 becomes very small, and the warpage of the flow path substrate 7 is eliminated, so that unnecessary stress is not generated in the piezoelectric element 22. There is no problem even if the supporting length L of the above is increased by a predetermined length. Therefore, you to ensure a more deformation of the large piezoelectric element 22, it is possible to eject the required amount of ink.

The applicant has joined members shown in Table 1 having different coefficients of thermal expansion α using an epoxy adhesive, and can be used under high temperature (40 ° C.) and low temperature (−20 ° C.), which can be considered in the actual specifications of the printer.
Warp of the supporting substrate 21 and the fixing member 11 with and adhesive 1
The presence or absence of 0 peeling was confirmed.

Supporting substrate: Free-cutting ceramic (α = 0.85 × 10 ⁻⁵ ) Fixing member: Plastic resin (α = 4.4 × 10 ⁻⁵ ) Stainless steel (α = 1.6 × 10 ⁻⁵ ) In each combination of the above, good results were obtained without peeling off the adhesive and without warping of both members. Further, the piezoelectric element 22 peels off or breaks from the support substrate,
No warpage or destruction of the flow path substrate 7 was caused.

FIG. 4 is a cross-sectional view showing a second bonding state between the support substrate and the fixing member.

In the figure, the supporting substrate 21 and the fixing member 11 are joined via the adhesive 10 as in FIG. The difference is that the adhesive 10 extends all over the groove 26.

The adhesive has high elasticity even when cured, and
Since the apparent thickness of the adhesive 10 is increased by the thickness of the adhesive 10 that has entered the groove 26, the configuration is the same as that in the case where the adhesive is bonded between the support substrate 21 and the fixing member 11 via an elastic body. Therefore, the supporting substrate 21 and the fixed member 1
1 can be suppressed.

Further, the adhesive 10 becomes wedges and
This also has the effect of increasing the shearing force in the arrangement direction.

Further, the following effects are also obtained.

FIG. 5 is a schematic diagram showing the propagation of vibration between the support substrate and the fixing member.

In general, when two members are joined, the reflectance r representing the degree of propagation of vibration of one member to the other member is represented by a suffix 1 on the oscillation side and a suffix 2 on the other member side. R = {(z ₁ −z ₂ ) / (z ₁ + z ₂ )} ² Here, Z is the acoustic impedance of each member, and for a member having a specific gravity ρ and a longitudinal elasticity coefficient E, z = (ρE) ^1/2 .

This reflectance indicates that the closer the value is to 1, the more easily the vibration is reflected at the boundary, that is, the more the vibration returns to the oscillation side.

When the oscillation side (subscript 1) is the support substrate 21 joined to the piezoelectric element 22 and the vibration receiving side (subscript 2) is the adhesive 10, the longitudinal elastic modulus of the adhesive 10 is generally large as described above. Therefore, the acoustic Pitan scan Z ₂ easily r becomes sufficiently large with respect to Z ₁ is close to the value 1. That is, the vibration transmitted from the support substrate 21 side is easily reflected on the support substrate 21.

As a result, unnecessary vibrations other than for the purpose of ink ejection are not transmitted to the piezoelectric element 22 bonded to the support substrate 21, and more stable driving of the piezoelectric element 22 can be realized.

FIG. 6 is a perspective view showing the shape and arrangement of the grooves of the support substrate in this embodiment.

FIG. 6A shows a case in which a plurality of grooves 26 are arranged in the direction of expansion and contraction of the piezoelectric element 22 (Z direction). FIG. In the case where a plurality of grooves 26 are arranged in the (X direction), FIG. 6C shows a case where the grooves 26 are arranged in a lattice shape by combining FIGS. 6A and 6B. (Both X and Z directions) In FIG. 6A, warpage due to the support substrate 21 and the fixing member 11 being restrained in the Z direction is reduced. In FIG. 6B, warpage can be reduced by being restrained in the X direction. In FIG. 6C, warpage can be reduced by restraining in both directions.

In FIG. 6, the grooves are arranged at equal intervals, but the intervals may be changed as necessary. The grooves need not be regularly arranged, but may be arbitrarily provided according to the purpose.

[0054]

According to the present invention, the supporting member can be fixed to the fixing member.
Of the piezoelectric element is parallel to the displacement direction of the piezoelectric element.
A plurality of grooves are arranged, and a plurality of convex surfaces between the grooves are joined to each other.
By forming the surface, warpage due to a difference in thermal deformation between the support substrate and the fixing member can be suppressed, so that stable ink ejection can be ensured, and an ink jet recording head of high print quality can be provided. In addition, since a material that could not be used due to the difference in thermal expansion coefficient can be used without any problem, the range of material selection can be expanded, and the degree of freedom in design can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment to which the present invention is applied.

FIG. 2 is a partial sectional view of an embodiment to which the present invention is applied.

FIG. 3 is an enlarged cross-sectional view showing a first bonding state between a support substrate and a fixing member.

FIG. 4 is an enlarged cross-sectional view showing a second bonding state between the support substrate and the fixing member.

FIG. 5 is a schematic diagram showing vibration propagation between a support substrate and a fixing member.

FIG. 6 is a perspective view showing the shape and arrangement of grooves of a support substrate in the present embodiment.

FIG. 7 is a cross-sectional view schematically showing the structure of a conventional inkjet recording head.

FIG. 8 is a diagram showing a state of thermal expansion deformation of a conventional ink jet recording head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Nozzle 3 Wall member 4 Ink common chamber 5 Pressure chamber 6 Ink supply port 7 Flow path board 8 Pressure plate 8a thin part 8b island part 10 Adhesive 11 Fixing member 12 Mounting hole 13 Control substrate 21 Support substrate 21a convex surface Reference Signs List 22 piezoelectric element 23 common electrode plate 24 wiring pattern 25 lead frame 26 groove 31 ink supply tube 101 nozzle plate 102 nozzle 105 pressure chamber 106 ink supply port 107 flow path substrate 108 pressure plate 111 fixing member 121 support substrate 122 piezoelectric element 130 sealing Element

Claims (4)

(57) [Claims] 1. A piezoelectric device comprising: a piezoelectric element; and a flow path substrate having a pressure chamber opposed to the piezoelectric element via a pressure plate,
An ink jet recording head for discharging ink droplets from a nozzle communicating with the pressure chamber due to a change in volume of the pressure chamber due to displacement of the piezoelectric element, wherein: a fixing member to which the flow path substrate is joined; A support substrate to which a rear end of the piezoelectric element is fixed in a state where the front end of the piezoelectric element is in contact with the pressure plate, and a bonding surface of the support substrate to a fixing member, An ink jet recording head, wherein a plurality of grooves are arranged in parallel with the displacement direction of the piezoelectric element, and a plurality of convex surfaces divided by the grooves are formed as the bonding surface. 2. The ink jet recording head according to claim 1, wherein a plurality of the grooves are arranged in a direction perpendicular to a direction in which the piezoelectric element is displaced. 3. The ink jet recording head according to claim 1, wherein a plurality of the grooves are arranged in a direction in which the piezoelectric element is displaced. 4. The ink jet recording head according to claim 1, wherein said grooves are arranged in a grid pattern in a direction perpendicular to the direction in which the piezoelectric element is displaced.