JPH09277527A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure adhesive and sealing properties even when the width of the top part of a partition of a pressure room is narrowed and to prevent pressure from leaking to the adjoining pressure room by dividing a piezoelectric element into a plurality of parts by the first wide and sharrow channels and the second narrow and deep channels. SOLUTION: A diaphragm 40 has an island 42 being an island-like thick part and the number of these islands is two-fold of pressure rooms 32 of a pressure room plate 30. The apex part of the even numbered island 42 is bonded to the free end part 22 of a piezoelectric element 20 and the back face of the odd numbered island 42 is bonded to the top part 36 of the partition 34 of a pressure room plate. The piezoelectric element 20 is divided into a plurality of parts by the first wide and shallow channels 24 and the second narrow and deep channels each with the same axial line as this channel 24. Practically, channel processing is performed by means of a wire saw in such a way that the first wide and shallow channels 24 with a channel width of approximately 100μm are processed by using a thick wire with a diameter of approximately 90μm. Strong tension is applicable to the thick wire to process a precise channel position.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement of an inkjet head.

[0002]

2. Description of the Related Art A conventional diaphragm is provided with islands which are island-shaped thick-walled parts in the same number as a plurality of divided piezoelectric elements. The island of the diaphragm faces and joins the free end of the piezoelectric element. The thin portion of the diaphragm is joined to the top of the partition wall of the pressure chamber plate.

The pressure chamber plate and the diaphragm are joined by pressing the diaphragm after applying an adhesive to the top of the partition wall of the pressure chamber plate. Since the top of the pressure chamber plate partition faces the thin portion of the diaphragm, the pressing force is not sufficiently applied to the adhesive between the top of the pressure chamber plate partition and the diaphragm.

The adhesive causes unevenness in thickness due to application.
The uneven adhesion thickness is a factor that hinders the adhesive sealing between the pressure chamber plate and the diaphragm. In order to reduce the thickness unevenness, it is important to apply a pressing force to the pressure chamber plate and the diaphragm to press the adhesive to reduce the unevenness. When the distance between the pressure chambers is wide and the width of the top of the partition wall of the pressure chamber can be sufficiently secured, the adhesive sealing property between the top portion of the partition wall of the pressure chamber and the diaphragm can be almost secured even with the conventional configuration.

Recently, there is a strong demand for higher resolution for improving image quality. The realization of this demand is to narrow the intervals between the pressure chambers and increase the number of pressure chambers provided within a unit length. As the space between the pressure chambers is halved, the width of the top of the partition wall is halved.

If the width of the top of the partition wall is reduced to about half with the conventional structure and bonding is performed, the adhesive sealing property cannot be ensured due to the slight remaining unevenness of the adhesive. As a result, there is a drawback that pressure leakage to the adjacent pressure chamber occurs and the ink ejection performance deteriorates.

Further, as the resolution is increased, the number of divisions of the piezoelectric element also increases. The land width of the piezoelectric element needs to be constant in order to obtain a predetermined driving force. Therefore, an increase in the number of divisions of the piezoelectric element requires a remarkable reduction in groove width.

Grooving is performed with a wire saw. A thin wire is used for narrow groove processing, but it is not possible to apply high tension because the thin wire is easily broken. For this reason, the wire interval is easily affected by slight scratches or chipping of the piezoelectric element at the time of contact with the piezoelectric element. Therefore, the addition of the narrow groove has a drawback that the deviation of the groove position becomes large.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to ensure adhesive sealability even if the width of the top of the pressure chamber partition wall is narrowed.
It is to eliminate the pressure leak to the adjacent pressure chamber. Further, it is necessary to ensure the groove position accuracy in the processing of the narrow groove as the number of divisions of the piezoelectric element increases. By achieving the objectives of both, the demand for increasing the number of pressure chambers provided within the unit length is achieved, and the demand for higher resolution of the inkjet head is met.

[0010]

In order to solve the above-mentioned problems, a nozzle plate having a plurality of nozzle holes for ejecting ink, a piezoelectric element that is an energy supply source for ink ejection divided into almost the same number as the number of nozzles, It has a pressure chamber plate having a number of grooves which is almost the same as the number of nozzles and which serves as a pressure chamber, and a diaphragm having an island that is an island-shaped thick portion, and the pressure chamber is formed by joining the pressure chamber plate and the diaphragm. An ink jet head that transfers the displacement of the piezoelectric element to the ink in the pressure chamber by joining the diaphragm and the piezoelectric element to each other, and the number of islands that are island-shaped thick portions of the diaphragm is equal to the pressure chamber of the pressure chamber plate. The tip of the even-numbered island is joined to the top of the piezoelectric element, the back of the odd-numbered island is joined to the top of the pressure chamber plate partition, and the piezoelectric element is wide and shallow. A groove, the width is narrow and deep second groove is divided into a plurality.

[0011]

1 is a sectional view showing an embodiment of an ink jet head according to the present invention. The nozzle plate 10 has a plurality of nozzle holes 12 for ejecting ink. The piezoelectric element 20 is an energy supply source for ejecting ink, and is divided by groove processing into almost the same number as the nozzle holes 12. The pressure chamber plate 30 has as many grooves as there are nozzle holes 12 and forms a pressure chamber that is also an ink flow path.

In FIG. 3, the diaphragm 40 has an island 42 which is an island-shaped thick portion. Diaphragm 4
The number of zero islands 42 is equal to the number of pressure chambers 32 of the pressure chamber plate 30.
2 times the number of The tip of the even-numbered island 42 is joined to the free end 22 of the piezoelectric element 20, and the back of the odd-numbered island 42 is joined to the top 36 of the pressure chamber plate partition 34.

Piezoelectric element side portions 2 are provided on both sides of the piezoelectric element 20.
8 is provided, and diaphragm side portions 44, which are thick portions, are also provided on both sides of the diaphragm 40.

The pressure chamber plate 30 forms a pressure chamber 32 by joining the diaphragm 40. To bond the pressure chamber plate 30 and the diaphragm 40, after applying an epoxy adhesive by a screen printing method or a transfer method, the pressure chamber plate 30 and the diaphragm 40 are heated and cured while being pressed.

Since the islands 42 are provided corresponding to the tops 36 of the pressure chamber plates 30, and the respective islands 42 have almost the same height, the above pressing force also applies to the adhesive between the tops 36 and the islands 42. It can be added sufficiently to ensure reliable adhesive sealing.

After joining the pressure chamber plate 30 and the diaphragm 40, the frame 50 is joined. As a method of joining the frame 50, an epoxy adhesive is applied to the frame 50 by a screen printing method or a transfer method, and the pressure chamber plate 30 and the frame 50 are pressed while sandwiching the diaphragm 40. After that, it is heated to cure the adhesive.

With the pressure chamber plate 30, the diaphragm 40, and the frame 50 integrated, the surfaces for joining the nozzle plates 10 are finished to be the same surface. The nozzle plate 10 is bonded to the finished surface. To bond the nozzle plate 10, an epoxy adhesive is applied to the top portion 36 of the pressure chamber plate 30 by a screen printing method or a transfer method, and the nozzle plate 10 is heated and cured while being pressed.

The diaphragm 40 joins the island 42 and the free end 22 of the piezoelectric element 20 and transmits the displacement of the piezoelectric element 20 to the ink in the pressure chamber.

The diaphragm 40 and the free end portion 22 of the piezoelectric element 20 are joined by applying an epoxy adhesive to the free end portion 22 and the piezoelectric element side portion 28 by a screen printing method or a transfer method.
The diaphragm 40 joined to the pressure chamber plate 30 is pressed. At the same time, since the adhesive is applied to the piezoelectric element side portion 28 and pressed and cured, the piezoelectric element side portion 28 and the diaphragm side portion 44 are also joined.

The piezoelectric element 20 has a wide and shallow first groove 2
4 and the second groove 2 which is narrow and deep on the same axis as the first groove 2
It is divided into plural by 6 and 6. In the present embodiment, groove processing is performed with a wire saw. First, the diameter is about 90
A wide and shallow first groove 24 having a groove width of about 100 μm is processed using a thick wire of μm. Since a strong tension is applied to the thick wire, accurate groove position is possible without being affected by slight unevenness or chipping on the surface of the piezoelectric element 20.

Then, a narrow deep second groove 26 having a groove width of about 50 μm is processed using a thin wire having a diameter of about 40 μm.
The position of the thin wire is set according to the central portion of the first groove 24. Since the thin wire is guided in the first groove 24, an accurate groove position can be obtained.

Even when the piezoelectric element 20 and the diaphragm 40 are misaligned when they are joined to each other, the odd-numbered islands 42 have the free ends 22 of the piezoelectric element 20 because of the first groove 24. It is possible to prevent mechanical contact with.

[0023]

According to the present invention, the adhesive can be surely pressed by the back surface of the odd-numbered island and the top of the partition wall of the pressure chamber plate. As a result, even if the width of the top of the pressure chamber plate partition is narrow, the adhesive application unevenness can be homogenized with a certain pressing force, and the adhesive sealing property between the top of the pressure chamber plate partition and the diaphragm can be secured.

Further, according to the present invention, since the piezoelectric element is divided into a plurality of first grooves having a wide width and a shallow width and second grooves having a narrow width and a deep width, a high groove position accuracy can be obtained. Further, due to the shape effect of the first groove having a wide width and a shallow width, it is possible to prevent contact between the piezoelectric element and the diaphragm of odd number, and it is possible to increase the number of piezoelectric elements provided within the unit length. As a result, it is possible to increase the number of pressure chambers provided within a unit length in which the pressure chamber interval is narrowed.

[Brief description of drawings]

FIG. 1 is a main sectional view showing an embodiment of an inkjet head according to the present invention.

FIG. 2 is a horizontal partial vertical sectional view of the present embodiment.

FIG. 3 is a cross-sectional view of an essential part of this embodiment.

[Explanation of symbols]

 10 Nozzle Plate 20 Piezoelectric Element 30 Pressure Chamber Plate 40 Diaphragm 50 Frame

Claims (1)

[Claims] 1. A nozzle plate having a plurality of nozzle holes for ejecting ink, a piezoelectric element which is an energy supply source for ink ejection divided into substantially the same number as the number of nozzles, and a groove having substantially the same number as the number of nozzles. A pressure chamber plate having a pressure chamber as a pressure chamber, and a diaphragm having an island that is an island-shaped thick portion. The pressure chamber is formed by joining the pressure chamber plate and the diaphragm, and the diaphragm and the piezoelectric element are joined. This is an inkjet head that transfers the displacement of the piezoelectric element to the ink in the pressure chamber, and the number of islands, which are island-shaped thick portions of the diaphragm, is twice the number of pressure chambers in the pressure chamber plate, The tip is joined to the top of the piezoelectric element, the back surface of the odd numbered island is joined to the top of the pressure chamber plate partition, and the piezoelectric element is on the same axial line as the first groove that is wide and shallow and the first groove. Is narrow An inkjet head characterized by being divided into a plurality of parts by a deep second groove.