JP3158771B2 - Inkjet print 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 print head for displacing a diaphragm forming a pressure chamber by a piezoelectric vibrator and compressing the pressure chamber by this displacement to eject ink droplets from nozzle openings. The present invention relates to a recording device used.

[0002]

2. Description of the Related Art Conventionally, a circular piezoelectric vibrator is fixed to a vibrating plate constituting a pressure chamber as shown in Japanese Patent Publication No. 24224/1990 as one of the ink jet print heads used in a recording apparatus. Things have been used for some time. This type of ink jet print head is
Since the displacement of the piezoelectric vibrator is small, the effective area needs to be large and the pressure chamber needs to have a large area. For this reason, a structure is required in which a pressure chamber is provided at a position distant from the nozzle opening where a relatively large area can be secured, and a connection is made between the nozzle opening and the nozzle opening by a flow path. In addition to the increase in size, there is a problem that adjustment for making the fluid resistance of each ink flow path uniform is necessary.

In order to solve such a problem, there has been proposed an ink jet print head using a piezoelectric vibrator that vibrates in a longitudinal vibration mode, wherein the tip of the vibrator is brought into contact with a diaphragm of a pressure chamber. ing. According to this print head, since the piezoelectric vibrator can be arranged to face the nozzle opening due to the use of the cross section of the vibrator, the flow path connecting the pressure chamber and the nozzle opening is unnecessary or extremely short. In addition to the above, the natural frequency of the piezoelectric vibrator itself is relatively large, so that high-speed driving can be performed and printing speed can be improved.

As disclosed in Japanese Patent Application Laid-Open No. Sho 58-119872, such an ink jet print head utilizing longitudinal vibration is such that a piezoelectric vibrator is pushed into a pressure chamber when no voltage is applied. It is configured such that a mechanical load is applied to the As a construction method, as shown in FIG. 8, an adhesive for fixing the vibration plate and the piezoelectric vibrator is used, or as shown in FIG. 9, the vibration plate and the piezoelectric vibrator are connected via protrusions. Was. A plurality of members are laminated between a vibrator fixing member that fixes the rear end of the vibration of the piezoelectric vibrator and the diaphragm, and they are fixed by fastening bolts.

[0005]

However, in the ink jet print head of the conventional configuration as described above, the vibration plate depends on the position of the vibrator fixing member and the piezoelectric vibrator and the thickness accuracy of the laminated members. However, there is a problem that the amount of the piezoelectric vibrator pushed into the pressure chamber varies for each print head or each pressure chamber. Due to the change in the amount of the diaphragm pushed in, the tension applied to the diaphragm changes, and the vibration state of the piezoelectric vibrator changes, and the shape of the pressure chamber, the behavior of the ink pressure change, etc. change. As a result, there is a problem that the ink ejection state changes. Further, when the pushing amount is in a range smaller than the desired amount, the joining state between the piezoelectric vibrator and the diaphragm is unstable, and when the pushing amount is large, the piezoelectric vibrating plate and the joining member joining the diaphragm are joined. There has been a problem that an excessive force is applied, and the diaphragm and the joint are broken, resulting in poor reliability. In particular, this problem becomes remarkable as the arrangement pitch of the nozzle openings is reduced. That is, by reducing the arrangement pitch, the width of the piezoelectric vibrator in the nozzle opening arrangement direction must be reduced, and the force generated by the piezoelectric vibrator is reduced. The vibrating plate works in a direction to reduce the vibration of the piezoelectric vibrator. However, unless the vibration is reduced as much as possible, the required deformation of the piezoelectric vibrator cannot be obtained.
For this reason, it is necessary to reduce the rigidity of the diaphragm. However, if the rigidity of the diaphragm is reduced, not only the diaphragm is easily broken, but also the amount of deformation of the diaphragm during manufacturing of the head increases, and the piezoelectric vibration increases. It will not be possible to reliably join the child.

[0006]

SUMMARY OF THE INVENTION Therefore, in the ink jet print head of the present invention, a flow path forming member forming a pressure chamber communicating with a nozzle opening and the flow path forming member forming one wall surface of the pressure chamber are provided. A vibrating plate formed thereon, and a plurality of longitudinal-vibration-mode piezoelectric vibrators arranged in a plurality of rows so that one end is fixed to a fixed member and the other end is in contact with the vibrating plate. A position of the front end, a positioning member having a front end at substantially the same position at both ends of the vibrator row, the front end of the positioning member through the diaphragm in a recess formed on the flow path forming member It is characterized by agreement.

[0007]

FIG. 1 is an exploded perspective view for explaining the structure of an embodiment of an ink jet type print head according to the present invention. FIG. 2 is a sectional view showing details of a joint between a positioning member and a diaphragm. 3 is an exploded perspective view showing details of a joint between the positioning member and the vibration plate. In the drawings, reference numeral 1 denotes a nozzle plate having a nozzle opening 2. Reference numeral 3 denotes a flow path forming member, and a pressure chamber 5 is formed by the vibration plate 4 and the nozzle plate 1. An ink supply channel 7 that connects the common ink channel 6 and the pressure chamber 5 is formed in the channel forming member 3. Reference numeral 18 denotes a frame in which an ink port 8 is formed, and an ink tank (not shown) communicates with the common ink flow path 6 by a supply pipe 19. Reference numeral 9 denotes a piezoelectric vibrator whose front end is coupled to a thick portion 10 formed at a position corresponding to the pressure chamber 5 of the diaphragm 4. The thick portion 10 is formed so as to increase the deformation amount of the axial displacement of the piezoelectric vibrator 9 and obtain a desired deformation volume. Also, there is an effect that the fixing of the piezoelectric vibrator 9 and the diaphragm 4 is facilitated. The thick portion 10 is formed of, for example, stainless steel having a thickness of 0.03 mm. A thin portion 11 is formed around the thick portion 10 of the diaphragm 4. Thin part 1
1 is formed of, for example, a 0.005 mm-thick polyimide film. The rear part of the piezoelectric vibrator 9 is fixed by a vibrator fixing member 12. The piezoelectric vibrator 9 is cut into a rod shape corresponding to the pressure chamber 5. The piezoelectric vibrator 9 uses a so-called laminated piezoelectric vibrator in which piezoelectric layers made of piezoelectric ceramics, for example, PZT, and conductive layers made of, for example, Ag-Pd are alternately laminated. By using such a laminated piezoelectric vibrator, the voltage applied to the piezoelectric vibrator can be reduced as much as possible, and an electric circuit, a power supply, and the like can be simplified. 13
Denotes a lead frame, which electrically connects a circuit (not shown) to the piezoelectric vibrator 9 via a vibrator fixing member 12.

When a signal is applied as a voltage to the piezoelectric vibrator 9 by a signal from a circuit (not shown), the piezoelectric vibrator 9 contracts along the axial direction of the rod. Thereby, the diaphragm 4 is deformed away from the nozzle plate 1,
The volume of the pressure chamber 5 expands. Then, after a predetermined time elapses, when the electric charge stored in the piezoelectric vibrator 9 is rapidly discharged, the piezoelectric vibrator 9 extends in the axial direction of the rod, and the vibrating plate 4 approaches the nozzle plate 1. As a result, the volume of the pressure chamber 5 contracts rapidly. As a result, the pressure of the ink in the pressure chamber 5 is increased, and the ink is jetted vigorously from the nozzle opening 2.

Dummy piezoelectric vibrators 14 as positioning members are arranged at both ends of the piezoelectric vibrators 9 in the arrangement direction. The rear part of the dummy piezoelectric vibrator 14 is fixed by the vibrator fixing member 12 similarly to the piezoelectric vibrator 9. The front end is fixed to a thick part 15 formed on the diaphragm 4. The periphery of the thick portion 15 is also a thin portion 11 like the periphery of the thick portion 10. The thick portion 15 to which the dummy piezoelectric vibrator 14 is fixed is the thick portion 1 to which the piezoelectric vibrator 9 is fixed.
It is formed to have the same thickness as 0.

A concave portion 16 is formed at a position corresponding to the thick portion 15 of the flow path forming member 3. In this embodiment,
The channel forming member 3 uses a material obtained by etching metal silicon. The position corresponding to the pressure chamber 5 and the common ink flow path of the flow path forming member 3 is formed as a hole through which metal silicon penetrates. The concave portion 16 is carved by, for example, 0.005 mm in depth by half etching of metal silicon. The etching depth of metal silicon can be precisely controlled by keeping the conditions constant.

The piezoelectric vibrator 9 and the dummy piezoelectric vibrator 14
Is formed by fixing a plate-shaped piezoelectric vibrator to the vibrator fixing member 12 and then cutting it into a rod shape. Therefore, it is easy to substantially match the axial lengths of the piezoelectric vibrator 9 and the dummy piezoelectric vibrator 14. The dummy piezoelectric vibrator 14 is formed wider than the piezoelectric vibrator 9. With this configuration, it is possible to prevent the piezoelectric vibrator 9 from being erroneously brought into contact with another member or the like and damaged during the manufacture of the head. Reference numeral 18 denotes a frame, which is configured to cover the head. A through hole is formed in the frame 18 so that the piezoelectric vibrator 9 and the dummy piezoelectric vibrator 14
The piezoelectric vibrator 9 and the dummy piezoelectric vibrator 14 are positioned at the positions of the thick portions 10 and 15 of the vibrating plate 4 by inserting the vibrator fixing member 12 to which the piezoelectric vibrator 4 is fixed. I have.

The dummy piezoelectric vibrator 14 is fixed so as to be pressed against the bottom 17 of the recess 16 of the flow path forming member 3 via the vibration plate 4. As a result, the vibrating plate 4 at the portion where the piezoelectric vibrator 9 is fixed is deformed in the pressure chamber 5, that is, in the direction approaching the nozzle plate 1. If the concave portion is not formed in the flow path forming member 3, the dummy piezoelectric vibrator abuts on the flow path forming member via the vibration plate, and if the vibration plate is deformed inside the pressure chamber, In addition, the piezoelectric vibrator does not come into contact with the diaphragm. In such a case, the vibration of the piezoelectric vibrator is not transmitted to the vibrating plate, and the pressure in the pressure chamber does not change and the liquid is not discharged. Also, even if they are in contact with each other, pressure is hardly applied when the vibration plate and the piezoelectric vibrator are joined, so there is a high possibility that the connection state will be extremely low in reliability. There is a high risk that the vibration plate and the piezoelectric vibrator will peel off. Such a problem can be avoided by providing the recess 16 in the flow path forming member 3. On the other hand, the dummy piezoelectric vibrator 1
When there is no positioning member as in 4, it is possible to apply pressure to the connection between the piezoelectric vibrator and the diaphragm, but it is not possible to control the amount of deformation of the diaphragm into the pressure chamber, so There is a high possibility that an excessive force will be applied to the vibration plate or its joint or the piezoelectric vibrator, and there is a high risk that the vibration plate or its joint may break such as a crack or generate a crack in the piezoelectric vibrator. Such a problem can be avoided by providing a positioning member such as a dummy piezoelectric vibrator and fixing the positioning member against the bottom 17 of the concave portion 16. While the diaphragm is pressed against the piezoelectric vibrator 9, the diaphragm is pushed into the bottom surface portion 17 of the concave portion 16 carved with high precision until the dummy piezoelectric vibrator 14 abuts via the diaphragm 4. The amount of deformation of the diaphragm 4 into the interior can easily be controlled precisely without variation. For example, the recess 16
Is formed to a depth of 0.005 mm, the amount of deformation of the diaphragm 4 into the pressure chamber 5 can be made 0.005 mm, which is substantially equal to the depth of the recess 16. An appropriate value is selected for the depth of the concave portion 16 according to the rigidity of the diaphragm 4, particularly the rigidity of the thin portion 11, the arrangement pitch of the nozzle openings 2, the ink ejection amount, and the like.

With such a configuration, the diaphragm 4 can be formed while giving an appropriate tension. If the tension is not applied to the diaphragm 4, the diaphragm is likely to be slack and formed, and as a result, the ink pressure generated in the pressure chamber 5 is absorbed by the slack diaphragm, and the nozzle is deflected. Although there is a high risk that the ink ejection from the opening 2 does not achieve desired characteristics, such a problem can be solved. It is also possible to solve the problem that the vibration period of the diaphragm changes due to the tension and the ink ejection state varies.

More preferably, a thin portion is also formed around the thick portion of the diaphragm 4 to which the dummy piezoelectric vibrator 14 is pressed against as in this embodiment, so that the dummy piezoelectric vibrator 14 is , It is possible to relatively uniformly apply tension to the thin portion 11 of the diaphragm 4. As another effect, when the thin portion 11 is formed of an electrically insulating material such as polyimide, the dummy piezoelectric vibrator 14 and the vibrating plate 4 have a thickness that allows the dummy piezoelectric vibrator 14 to be fixed. Since it is possible to electrically insulate except for the meat portion 15, it is not necessary to consider electric leakage to other members via ink, and the head configuration and the head manufacturing method can be simplified.

FIG. 4 is an exploded sectional view showing an embodiment in which the flow path forming member is made of a photosensitive resin. In this embodiment, the flow path forming member includes a first flow path forming layer 1 formed of a film-shaped photosensitive resin on the nozzle plate 101 side.
02 and a second flow path forming layer 103 formed by applying and developing a liquid photosensitive resin with a uniform thickness using a spin coater or a roll coater on the vibration plate 104 side. A hole 106 is formed in a position of the second channel forming layer 103 corresponding to a portion where the dummy piezoelectric vibrator 114 is pressed. As a result, the first flow path forming layer 1
After laminating the second flow path forming layer 103 and the second flow path forming layer 103, a configuration similar to that of the above-described embodiment shown in FIG. 2 can be obtained.
The dummy piezoelectric vibrator 114 is pressed against the first channel forming layer at the bottom of the hole 106 penetrating through the diaphragm 104. Therefore, the piezoelectric vibrator 109 is pressed so as to deform the vibration plate 104 into the pressure chamber 105.

As the flow path forming member, the first flow path forming layer is formed of metal silicon, and the second flow path forming layer is formed on metal silicon with a photosensitive resin. Exactly the same effect can be obtained by using a laminated structure or the like.

FIG. 5 is a sectional view showing a second embodiment in which a transducer fixing member is used as a positioning member. In this embodiment, the piezoelectric vibrators 209 and 20
Positioning portions 214 are formed at both ends of the transducer fixing member 212 to which 9, 209... Are fixed. The front end of the positioning section 214 is configured to be substantially at the same position as the front end of the piezoelectric vibrator 209. Flow path forming member 203
A concave portion 206 is formed at a position corresponding to the positioning portion 214.
4 is pressed against the bottom 207 of the recess 206, and the piezoelectric vibrator 209 is fixed so as to push the vibration plate 204 into the pressure chamber 205. The vibrator fixing member 212 is made of a relatively strong material such as alumina or free-cutting ceramics, and does not break even when the positioning portion 214 is strongly pressed against the bottom of the concave portion 206, so that the vibrator fixing member 212 is easily broken. A head can be manufactured.

The positioning portion may be configured to sandwich the piezoelectric vibrator 309 as shown in a third embodiment of FIG. FIG. 6 is a sectional view in a direction perpendicular to the arrangement direction of the nozzle openings. The vibrator fixing members 312 and 313 are sandwiched between the piezoelectric vibrators 309 from both sides.
09 is fixed. The vibrator fixing members 312 and 313 have steps 314 and 315, and define the rear end of the vibration of the piezoelectric vibrator 309 at the start point of the steps. Steps 314, 3
The front end of the piezoelectric vibrator 309 is formed at substantially the same position as the front end of the piezoelectric vibrator 309.
6 is pressed against the bottom. The diaphragm 304 has a thick portion 31 corresponding to a portion where the piezoelectric element 309 is fixed.
0, a thick portion 311 is formed corresponding to a portion to which the positioning members 312 and 313 are fixed, and a periphery thereof is formed as a thin portion 307. Since the piezoelectric vibrator 309 is covered by the vibrator fixing members 312 and 313, the head can be easily manufactured without breaking the piezoelectric vibrator 309 during the manufacture of the head.
Further, the diaphragms 304 in the vicinity of each of the pressure chambers 305 in which the plurality of diaphragms 304 are arranged are positioned by the positioning members 314, 3
Since the tension acts on the diaphragm 15, the tension uniformly acts on the diaphragm 304 of each pressure chamber 305, and the diaphragm 304 can be securely pressed against and fixed to the diaphragm 304 without sagging.

The positioning member is formed not only by a dummy piezoelectric vibrator or a vibrator fixing member, but also by, for example, fixing separate members made of metal, ceramics or the like to the vibrator fixing member at both ends where the piezoelectric vibrators are arranged. However, it will be clear that the present invention is effective.

According to the present invention, it is possible to satisfactorily eject ink even if the piezoelectric vibrator is not fixed to the diaphragm. As shown by the solid line in FIG. 7, the diaphragm 404 is held while being tensioned so as to be pushed into the pressure chamber 405 by the piezoelectric vibrator 409 while the print signal is not input. When a print signal is applied as a voltage to the piezoelectric vibrator 409, the piezoelectric vibrator 409 contracts in the axial direction as shown by a two-dot chain line in FIG. Also, the pressure chamber 405 is deformed in a direction in which the pressure chamber 405 is enlarged substantially in synchronization with the contraction of the piezoelectric vibrator 409. Even when the piezoelectric vibrator 409 contracts most, the diaphragm 404 is formed to the depth of the concave portion where tension is still applied. After a certain period of time, the electric charge stored in the piezoelectric vibrator 409 is rapidly discharged, so that the piezoelectric vibrator 409 extends in the axial direction again as indicated by the solid line. Therefore, the vibration plate 404 is pressed by the piezoelectric vibrator 409 and deforms in a direction in which the pressure chamber 405 contracts.
5, the ink is ejected from the nozzle opening 402. In the case where the piezoelectric vibrator and the diaphragm are not fixed as described above, it is particularly necessary to precisely control the tension applied to the diaphragm, but according to the present invention, it is possible to easily and consistently manage the tension.

In the head in which the piezoelectric vibrator and the vibration plate are not fixed as described above, for example, an ink flow path portion such as a vibration plate, a flow path forming plate, a nozzle plate, an ink tank, etc. The vibrator, the vibrator fixing member, the frame, and the actuator unit serving as the signal transmission unit can be separately configured. For this reason, when the ink stored in the ink tank is completed or when ink of a different color is ejected, it is possible to replace only the ink channel portion without replacing the actuator portion. Can be made very inexpensive. Further, when the actuator section is broken due to fatigue or the like, or when the performance is deteriorated, it is possible to replace only the actuator section, and it is possible to maintain good printing quality for a long period of time.

[0022]

As described above, according to the present invention, the positioning member having the end at substantially the same position as the front end of the piezoelectric vibrator in the axial direction is provided. Since the concave portion is formed at the position corresponding to, the positioning member hits the concave portion, and the piezoelectric vibrator can be contacted and pressed against the vibration plate while managing the diaphragm reliably and with high accuracy, and the ink ejection is stable. In addition, a highly reliable ink jet print head can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a first embodiment of the present invention.

FIG. 2 is a partial sectional view of the first embodiment of the present invention.

FIG. 3 is a partially exploded perspective view of the first embodiment of the present invention.

FIG. 4 is an exploded cross-sectional view showing a configuration of another member of the present invention.

FIG. 5 is a sectional view of a second embodiment of the present invention.

FIG. 6 is a sectional view of a third embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating ink ejection according to a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a configuration of a conventional ink jet print head.

FIG. 9 is a sectional view showing another embodiment of a conventional ink jet print head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Nozzle opening 3 Flow path forming member 4 Vibration plate 5 Pressure chamber 6 Depression 7 Common ink flow path 8 Ink port 9 Piezoelectric vibrator 10 Thick part of diaphragm 11 Thin part of diaphragm 12 Vibrator fixing member 13 Lead frame 14 Dummy piezoelectric vibrator 15 Thick part of diaphragm corresponding to dummy piezoelectric vibrator 16 Depression 17 Bottom part of depression 18 Frame 19 Ink supply pipe

Claims (5)

(57) [Claims] 1. A flow path forming member forming a pressure chamber communicating with a nozzle opening, a diaphragm formed on the flow path forming member forming one wall surface of the pressure chamber, and one end fixed to a fixing member. A plurality of vertical-mode piezoelectric vibrators arranged in a plurality of rows so that the other end abuts on the diaphragm, and a front end portion at a position substantially equal to a position of a front end on the other end side of the vibrator. An ink jet print head having positioning members at both ends of the vibrator row, wherein a front end of the positioning member is engaged with a concave portion formed on the flow path forming member via the vibration plate. 2. The ink jet print head according to claim 1, wherein said positioning member is a dummy piezoelectric vibrator. 3. The ink jet print head according to claim 1, wherein the positioning member is a vibrator fixing member that defines a rear end of the vibration of the piezoelectric vibrator. 4. The diaphragm has a thin portion and a thick portion, and a portion corresponding to the positioning member is a thick portion.
2. The ink jet print head according to claim 1, wherein the periphery is a thin portion. 5. The concave portion is formed so as to press the positioning member through the vibration plate until the positioning member comes into contact with the positioning member, and presses the piezoelectric vibrator and the vibration plate without fixing them. The ink jet print head according to claim 1, wherein