JPH08118623A - Piezoelectric actuator of ink jet head - Google Patents

Abstract

PURPOSE: To eliminate the possibility of the damage to a piezoelectric element at the time of assembling work by cutting one piezoelectric element bonded to a substrate into a comb tooth shape and forming projections protruding in a wall shape on the surface to which the piezoelectric elements are bonded of the substrate along both side parts of the piezoelectric elements. CONSTITUTION: An ink jet head 10 is constituted, by arranging pressure chambers 13 receiving the supply of ink to the inside of a nozzle plate to which ink jet nozzles 11 are provided at a predetermined interval and attaching a vibration plate 14 to the rear surfaces of the pressure chambers 13. A piezoelectric actuator 20 wherein a plurality of piezoelectric elements 21 corresponding to the respective pressure chambers 13 are arranged in a comb shape is provided inside the vibration plate 14. In this case, the projections 23 protruding in a wall shape along both side parts of the first half parts of the piezoelectric elements 21 are formed to the surface to which the piezoelectric elements 21 are bonded of the substrate 22 made of ceramic. By this constitution, the piezoelectric elements 21 are protected from damage at the time of the assembling work of the piezoelectric actuator to a holder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet formed by cutting one piezoelectric element bonded to a substrate into a plurality of comb teeth in order to drive an ink jet head in which a plurality of ink jet nozzles are arranged. The present invention relates to a piezoelectric actuator for a head.

Piezoelectric elements are widely used as drive sources for ejecting ink droplets from ink jet nozzles, and such piezoelectric elements must be arranged corresponding to each nozzle.

However, since a large number of nozzles are arranged at narrow intervals in the ink jet head, it is not easy to arrange the piezoelectric elements one by one correspondingly. Therefore, one piezoelectric element bonded to the substrate is cut into a plurality of comb teeth according to the arrangement of the nozzles to form a piezoelectric actuator.

[0004]

2. Description of the Related Art In order to manufacture a piezoelectric actuator, conventionally, as shown in FIG. 15, the rear half of the back surface of a piezoelectric element 91 is bonded to a substrate 92, as shown in FIG. And the piezoelectric element 91
Was cut into a plurality of comb teeth.

At this time, the left and right portions 91b of the piezoelectric element 91 are formed thick in order to protect the inner thin comb tooth-shaped portion 91a, and this portion is called a reinforcing piezoelectric body 91b.

[0006]

However, since the material of the piezoelectric element 91 is generally very fragile, the comb-teeth portion 91a or the reinforcing piezoelectric body 91b is broken when the piezoelectric actuator is inserted into the slot of the holder. Things often happen.

The reinforcing piezoelectric members 91b formed at both ends of the piezoelectric actuator occupy a large volume in the piezoelectric element 91, which has a high material cost, although it is not used for driving the discharge. It is very wasteful in terms of cost.

Further, in the conventional piezoelectric actuator as described above, the adhesive for bonding the piezoelectric element 91 to the substrate 92 may stick out from the bonding surface to the side portion of the piezoelectric element 91. As a result, the piezoelectric actuator may not fit into the slot of the holder for holding the piezoelectric actuator, or even if it fits in, the ejection force may decrease due to misalignment.

When the piezoelectric element 91 is cut, a dummy substrate is tentatively attached with wax to the portion not received by the substrate 92 so that chipping (peeling of the electrode) does not occur. However, if the adhesive protrudes forward from the bonding surface, a gap is created between the dummy substrate 93 and the substrate 92 as shown in FIG. 17, and chipping occurs during cutting. Reference numeral 94 is a wax, 95 is a protruding adhesive, and 96 is a working table.

Therefore, according to the present invention, there is no risk of damaging the piezoelectric element during the assembling work of the piezoelectric actuator to the holder, and the piezoelectric element is cut into comb teeth over the entire width and is effectively utilized without waste for driving ejection. It is possible,
Another object of the present invention is to provide a piezoelectric actuator for an inkjet head, which can eliminate the inconvenience at the time of processing and assembling caused by the adhesive protruding.

[0011]

In order to achieve the above object, a piezoelectric actuator of an ink jet head according to the present invention, as shown in FIG. 1 for explaining an embodiment,
In order to drive an inkjet head in which a plurality of inkjet nozzles are arranged, in a piezoelectric actuator formed by cutting one piezoelectric element bonded to a substrate into a plurality of comb teeth, the piezoelectric elements of the substrate are bonded to each other. A protrusion protruding in a wall shape along both sides of the piezoelectric element is formed on the surface on the side of the piezoelectric element.

The projections may be provided on both sides of at least the portion to which the piezoelectric element is joined, and the projection height may be at least 10 μm or more. The outer surface of the projection may be the piezoelectric actuator. May be used as a reference surface for positioning when incorporated in the inkjet head.

A groove may be formed in the vicinity of the tip of the piezoelectric element bonding surface of the substrate in a direction intersecting the cutting direction of the piezoelectric element.

[0014]

With the projections protruding in a wall shape from the substrate along both sides of the piezoelectric element, the projections of the substrate come into contact with the surroundings when the piezoelectric actuator is assembled, so that the piezoelectric element can be prevented from contacting the surroundings. With such protrusions, the piezoelectric element can be thinly cut into comb teeth over the entire width up to both ends and used for ejection driving.

Also, the protrusion prevents the adhesive from protruding from the joint portion to the side of the piezoelectric element. In that case, protrusions are provided on both sides of the portion to which the piezoelectric element is joined, and the protrusion height is at least 10 μm.
If so, it is effective in preventing the adhesive from protruding.

By forming a groove near the tip of the piezoelectric element bonding surface of the substrate in a direction intersecting the cutting direction of the piezoelectric element, the adhesive is prevented from protruding forward from the bonding surface.

[0017]

Embodiments will be described with reference to the drawings. FIG. 2 shows the vicinity of the recording portion of the inkjet printer. The inkjet head 10 mounted on the carriage 2 that reciprocates along the stay shaft 1 faces the recording paper 100 that is wound around the platen roll 3 and conveyed. Are arranged.

A large number (for example, 64) of ink jet nozzles are arranged in the ink jet head 10 toward the paper surface of the recording paper 100, and the ink supplied from the ink tank 4 through the hose 5 is ejected from the nozzles. As a result, inkjet recording is performed on the surface of the recording paper 100.

FIG. 3 is a plan sectional view of the ink jet head 10. The ink jet nozzles 11 are formed on a nozzle plate 11 arranged on the front surface at predetermined intervals, and the ink is formed inside each ink jet nozzle 11. A pressure chamber 13 that receives the supply of ink from the tank 4 is arranged, and a vibration plate 14 is attached to the back surface of the pressure chamber 13.

A plurality of piezoelectric elements 21 are provided on the piezoelectric actuator 20 arranged on the back side of the vibrating plate 14 so as to abut the vibrating plate 14 corresponding to the positions of the pressure chambers 13.
Are arranged in a comb shape.

The piezoelectric element 21 is a ceramic substrate 22.
The substrate 22 is provided with the projections 23 protruding in a wall shape on both sides of the front half of the piezoelectric element 21 on the surface on the side to which the piezoelectric element 21 is bonded.

FIG. 1 is a perspective view of the piezoelectric actuator 20, and the protrusion height of the protrusion 23 from the surface of the substrate 22 is almost the same as the height of the piezoelectric element 21. A thin film flexible cable 24 for supplying drive power to each piezoelectric element 21 is connected to the rear end side of the piezoelectric element 21.

A guide surface 25, which serves as a guide when the piezoelectric actuator 20 is fitted into a slot of a holder to be described later, is formed on the outer side of the projection 23 provided on both sides of the substrate 22 so as to project laterally. ing. Reference numeral 26 is a processing groove generated when the side surface of the projection 23 is used as a reference surface for positioning.

FIG. 4 shows a state before the substrate 22 and the piezoelectric element 21 are bonded to each other when the piezoelectric actuator 20 is manufactured. A single block material is used for the piezoelectric element 21 as a whole, and the substrate 22 is formed by cutting a plate material as indicated by a broken line so that the projections 23 project upward.

On the front side of the substrate 22, there are formed recesses 27 having a width for fitting the piezoelectric element 21 and having a depth of about half the length of the piezoelectric element 21, and the left and right sides of the recess 27 are formed. The protrusion 23 projects.

Then, the rear half of the back surface of the piezoelectric element 21 is bonded to the upper surface of the substrate 22 so that the front end surfaces of the piezoelectric element 21 and the substrate 22 are flush with each other. The shaded portions 40, 40 in FIG. 4 are the adhesive portions.

After that, when the adhesive hardens, the piezoelectric element 2
1 is cut into a plurality of comb teeth from the front side with a dicing saw. At that time, the portion of the substrate 22 that is joined to the piezoelectric element 21 is cut into a comb shape together with the piezoelectric element 21.

As described above, the protrusions 23 protruding from the substrate 22 along the left and right side portions of the piezoelectric element 21 protect the piezoelectric element 21 inside thereof, so that the piezoelectric element 21 is protected as shown in FIG. It is possible to cut into uniform comb teeth over the entire width up to the left and right ends and use them for ejection drive. Therefore, the material of the piezoelectric element 21 is not wasted, and the material cost is considerably reduced.

The substrate 22 is, as shown in FIG.
The protrusions 23 may be formed separately from the substrate 22 and joined together, or may be molded integrally with the protrusions 23 by the molds 221 and 222 as shown in FIG.

As shown in FIG. 7, the piezoelectric actuator 20 formed as described above is attached to the ink jet head 10 by being fitted in the slot 31 formed in the holder 30 in a convex cross section. To be

When the piezoelectric actuator 20 is fitted into the slot 31 as described above, the piezoelectric element 21 is used in this embodiment.
Since the projections 23 are projected from the substrate 22 on both left and right sides of the piezoelectric element 21 to protect the piezoelectric element 21, there is no possibility of damaging the piezoelectric element 21.

In order to play such a role, the projection 23 does not necessarily have to project at the same height as the piezoelectric element 21, and it is sufficient that it projects at least at a height of at least half of the piezoelectric element 21.

The piezoelectric actuator 20 has a slot 31.
Once fitted, it must be accurately positioned with respect to slot 31. As for the positioning in the width direction, as shown in FIG.
The outer surface of the projection 23 may be the reference surface for positioning, or, as shown in FIG. 9, the outer surface of one of the protrusions 23 may be the reference surface.

Further, as shown in FIG. 10, the key 32 and the key groove 2 which engage with each other in the slot 31 and the base plate 22.
8 may be provided, and positioning may be performed by the engagement. In either case, for the height direction,
The narrow portion of the slot 31 and the guide surface 25 of the substrate 22 are engaged with each other for positioning.

FIG. 11 shows a second embodiment, in which the position of the front end face of the protrusion 23 provided on the substrate 22 is set to the piezoelectric element 2.
The position is slightly rearward of the position of the front end face of No. 1 so as not to come into contact with the diaphragm 14. The interval is, for example, 5
Since it is about 1000 μm, it is possible to prevent the occurrence of damage due to contact between both members.

FIG. 12 shows a third embodiment, in which a part of the piezoelectric elements 21 arranged in a comb shape is omitted. In this embodiment, the protrusions 23 are formed so as to extend rearward along both sides of the bonding portion 40 between the substrate 22 and the piezoelectric element 21.

As a result, the protrusion of the adhesive from the adhesive portion 40 to the lateral guide surface 25 is blocked by the protrusion 23, so that when the piezoelectric actuator 20 is fitted into the slot 31 of the holder 30, the adhesive is not exposed. It can be fitted in the correct position without hindrance. In order to obtain the effect, it is sufficient that the protrusion 23 protrudes from the surface of the substrate 22 by at least about 10 μm or more.

FIG. 13 shows the substrate 22 of the fourth embodiment. A groove 29 is formed in the substrate 22 in the vicinity of the tip of the piezoelectric element bonding portion 40 in the direction orthogonal to the cutting direction of the piezoelectric element 21. It is a thing.

By forming such a groove 29,
The piezoelectric element 21 and the substrate 22 can be bonded together so that the adhesive in the adhesive section 40 does not flow forward. For that purpose, the depth of the groove 29 may be about 120 μm, for example.

As a result, as shown in FIG. 14, the dummy substrate 9 is formed so that no space is formed on the lower surface of the piezoelectric element 21.
Since the end face of 3 can be pressed against the substrate 22 and fixed to the piezoelectric element 21 with the wax 94, chipping does not occur when the piezoelectric element 21 is cut by a dicing saw.

[0041]

According to the present invention, when the piezoelectric actuator is assembled to the holder or the like by the projections protruding from the substrate along the both sides of the piezoelectric element in a wall shape, the projections come into contact with the surroundings and the piezoelectric element is surrounded. Since it can be protected so as not to come into contact with the piezoelectric element, there is no risk of damaging the piezoelectric element, and the piezoelectric element can be cut into comb teeth over the entire width and effectively used for ejection drive without waste. .

Further, since the protrusion of the adhesive, which tends to protrude laterally from the joint portion between the piezoelectric element and the substrate, can be prevented by the protrusion, it is possible to prevent the defective assembly of the holder, etc. By forming a groove near the tip of the piezoelectric element bonding surface in a direction intersecting the piezoelectric element cutting direction, it is possible to prevent the adhesive from protruding to the front and prevent chipping during cutting.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 is a partial perspective view of a recording unit of the inkjet printer.

FIG. 3 is a plan sectional view of the first embodiment.

FIG. 4 is a partial perspective view of the first embodiment before assembly.

FIG. 5 is a perspective view showing another example of the method for manufacturing the substrate of the first embodiment.

FIG. 6 is a perspective view showing another example of the method for manufacturing the substrate of the first embodiment.

FIG. 7 is a perspective view showing an assembled state of the first embodiment.

FIG. 8 is a front view showing a first example of an assembled state of the first embodiment.

FIG. 9 is a front view showing a second example of the assembled state of the first embodiment.

FIG. 10 is a front view showing a third example of the assembled state of the first embodiment.

FIG. 11 is a plan sectional view of a second embodiment.

FIG. 12 is a partial perspective view of the third embodiment.

FIG. 13 is a perspective view of a substrate according to a fourth embodiment.

FIG. 14 is a side sectional view of the fourth embodiment during a cutting process.

FIG. 15 is a perspective view of a conventional example before cutting.

FIG. 16 is a perspective view of a conventional example after cutting.

FIG. 17 is a side sectional view of a conventional example during cutting.

[Explanation of symbols]

 20 Piezoelectric actuator 21 Piezoelectric element 22 Substrate 23 Protrusion

Claims (4)

[Claims] 1. A piezoelectric actuator formed by cutting a single piezoelectric element bonded to a substrate into a plurality of comb teeth to drive an inkjet head in which a plurality of inkjet nozzles are arranged. A piezoelectric actuator for an ink jet head, characterized in that projections protruding in a wall shape are formed along both sides of the piezoelectric element on a surface on which the piezoelectric element is bonded. 2. The piezoelectric actuator for an ink jet head according to claim 1, wherein the projections are provided on both sides of at least the portion to which the piezoelectric element is joined, and the projection height is at least 10 μm or more. 3. The piezoelectric actuator for an inkjet head according to claim 1, wherein an outer surface of the protrusion serves as a reference surface for positioning when the piezoelectric actuator is incorporated in the inkjet head. 4. A piezoelectric element bonding surface of the substrate, near the tip thereof,
The piezoelectric actuator for an ink jet head according to claim 1, 2 or 3, wherein a groove is formed in a direction intersecting a cutting direction of the piezoelectric element.