The present invention relates to an ink jet recording head to be suitably used for a printer or a plotter.
A related ink jet recording head comprises a vibrator unit bonding a piezoelectric vibrator group to the surface of a fixation base formed of stainless steel, a casing for accommodating the vibrator unit, and a channel unit bonded to the tip portion of the casing and provided with a pressure chamber and a nozzle orifice.
The casing is molded of a synthetic resin, for example, and is provided with a housing space for accommodating and fixing the vibrator unit therein. The housing space is provided every vibrator unit. In a recording head comprising a plurality of vibrator units, therefore, a bulkhead portion molded integrally with the casing is provided between the adjacent housing spaces. The vibrator unit is bonded to the bulkhead portion and is thereby accommodated and fixed into the housing space.
For example, as shown in FIG. 20, the back face of a fixation base 1 is bonded to a bulkhead portion 2 so that a pair of vibrator units 3 are accommodated and fixed into housing spaces 4. In such a fixing state, the tip end face of each of piezoelectric vibrators 5 is exposed to the outside of a casing 6 through an opening on the tip side of the housing space 4, and the tip end face is bonded to an island portion 7a of an elastic plate 7. The piezoelectric vibrator 5 is extended in the longitudinal direction of the vibrator depending on the supply of power to the piezoelectric vibrator 5 and the extension causes the elastic plate 7 to be deformed so that the volume of a pressure chamber 8 is changed. By the change in the volume of the pressure chamber 8, therefore, a pressure fluctuation is generated on an ink in the pressure chamber 8 and an ink drop is discharged from a nozzle orifice 9.
In the related recording head, thus, a plurality of housing spaces 4 are provided with the bulkhead portion 2 interposed therebetween and the vibrator unit 3 is accommodated and fixed every housing space 4. For this reason, when the number of the vibrator units 3 to be accommodated and fixed into one recording head is increased, the size of the casing 6 is to be increased correspondingly so that the size of the recording head is increased.
Moreover, since the vibrator unit 3 is bonded to the bulkhead portion 2, it is necessary to enhance the rigidity of the bulkhead portion 2. In order to obtain a requisite rigidity, it is necessary to increase the thickness of the bulkhead portion 2. Also in this respect, the size of the recording head is increased.
In a recent vibrator unit, particularly, the number of the piezoelectric vibrators provided in one vibrator unit tends to be increased. Therefore, a higher rigidity is required for the bulkhead portion. As a result, it is necessary to more increase the thickness of the bulkhead portion. Consequently, the size of the recording head is further increased.
Moreover, the casing 6 is generally formed of a synthetic resin. For this reason, in the case in which the recording head is put in a high humidity environment, the bulkhead portion 2 is swollen by moisture absorption as shown in FIG. 21. By the swelling, the piezoelectric vibrators 5 might be inclined toward the outside. If the piezoelectric vibrator 5 is inclined, a stress is applied to a bonding interface of the piezoelectric vibrator 5 and the island portion 7a so that the piezoelectric vibrator 5 is easily peeled from the island portion 7a. Moreover, since an unnatural stress is applied to the elastic plate 7, there is a possibility that a discharge characteristic might be adversely influenced.
The invention has been made in consideration of such circumstances and has a main object to provide an ink jet recording head which can be small-sized. Moreover, the invention has another object to provide an ink jet recording head capable of preventing drawbacks from being caused by the moisture absorption of a casing and ensuring workability and assembling properties and a method of manufacturing the ink jet recording head.
In order to achieve the above objects, according to the present invention, there is provided an ink jet recording head, comprising:
a channel forming substrate, in which a channel which extends from a common ink reservoir to nozzle orifices via pressure chambers associated with the respective nozzle orifices;
an elastic plate, a first surface thereof being bonded onto one surface of the channel forming substrate;
a supporting base formed with at least one through hole therein, a first face thereof being bonded onto a second surface of the elastic plate which is opposite to the first surface of the elastic plate;
a resin casing formed with an accommodation space therein, a first face thereof being bonded onto a second face of the supporting base which is opposite to the first face of the supporting base; and
at least one vibrator unit, including a fixation base, and piezoelectric vibrators arranged on a first face of the fixation base such that first ends of the piezoelectric vibrators are fixed thereon and opposite free ends overhang a second face of the fixation base, the vibrator unit accommodated in the accommodation space of the casing such that the piezoelectric vibrators extend through the through hole of the supporting base and the free ends thereof abut against the second surface of the elastic plate, and such that the second face of the fixation base is bonded onto the second face of the supporting base.
In this configuration, since the fixation base of the vibrator unit is bonded onto the supporting base, the size of the recording head can be reduced.
Moreover, it is possible to eliminate the bond of the casing and the vibrator unit, and to more decrease the bonding area than that in the related configuration. Therefore, it is possible to reduce a mechanical stress received by the vibrator unit due to the moisture absorption of the casing. Consequently, it is possible to eliminate a drawback caused by the mechanical stress, for example, to prevent a fluctuation in the discharge characteristic and the peeling of the piezoelectric vibrator from the elastic plate.
Preferably, the supporting base is made of metal material.
Here, it is preferable that the supporting base is made of stainless steel.
Preferably, the fixation base is made of metal material.
Here, it is preferable that the supporting base is made of metal material identical with the metal material forming the fixation base.
In the above configurations, the supporting base and the fixation base can be formed of a member having a relatively high rigidity. Therefore, the rigidity of the recording head can be increased and the reaction force applied from the piezoelectric vibrator can be received sufficiently. Consequently, the discharge characteristic of the ink drop can be stabilized. Furthermore, a member having high dimensional precision is used for the supporting base. Therefore, it is also possible to prevent a positional shift of the piezoelectric vibrator and the channel unit after the bonding.
Preferably, at least one concave groove is formed on the second face of the supporting base in the vicinity of the through hole, to hold adhesive for bonding the fixation base.
In this configuration, the adhesive can be selectively injected between the supporting base and the fixation base.
Here, it is preferable that there is defined a first gap between the second face of the supporting base and the second face of the fixation base, into which the adhesive held in the concave groove enters.
Further, it is preferable that a dimension of the first gap is so determined as to establish a capillary attraction therein.
In the above configurations, the adhesive can be reliably prevented from spilling. Furthermore, it is possible to position the vibrator unit with very high positional precision while reliably causing the piezoelectric vibrator to abut on the elastic plate.
Besides, it is preferable that a plurality of concave grooves are formed on the fixation base.
Here, it is preferable that a width of the second face of the fixation base is wider than a width of an area on which the piezoelectric vibrators are arranged. The concave grooves are placed in the vicinity of both widthwise ends of the second face of the fixation base.
Besides, it is preferable that the concave groove is formed such that a first part thereof is situated outside of a bonding area onto which the fixation base is bonded. The adhesive is injected from the first part.
Here, it is preferable that the first part is directed to a thickness direction of the second face of the fixation base.
Alternatively, the first part may be directed to a widthwise direction of the second face of the fixation base.
Further, it is preferable that a width of the first part becomes wider as being away from the bonding area.
Preferably, a dimension of the through hole in a first direction in which the piezoelectric vibrators are arranged is wider than a width of the second face of the fixation base, so that both side ends of the through hole in the first direction is situated outside of an area for bonding the supporting base and the fixation base.
Preferably, side faces of the fixation base which are other than the first face and the second face are bonded onto an inner face of the accommodation space of the casing.
Here, it is preferable that there is defined a second gap between each side face of the fixation base and the inner face of the casing, to hold adhesive therein for bonding the fixation base and the casing.
Further, it is preferable that a dimension of the second gap is so determined as to establish a capillary attraction therein.
Besides, it is preferable that a guide passage is formed on the inner face of the casing such that a first end thereof opens at a second face of the casing which is opposite to the first face of the casing, and such that a second end thereof is placed at an area in which the side faces of the fixation base faces the inner face of the casing. Here, adhesive is injected from the first end of the guide passage to bond the fixation base onto the inner face of the casing.
In this configuration, the adhesive can be reliably injected between the inner face of the casing and the fixation base.
Here, it is preferable that a width of the guide passage becomes wider as closing to the first end thereof.
Preferably, a pair of vibrator units are accommodated in the casing while third faces of the fixation bases which are opposite to the respective first faces are faced with each other.
Preferably, an acoustic impedance of the fixation base is greater than that of the piezoelectric vibrator.
Here, it is preferable that a Young""s modulus of the fixation base is greater than that of the piezoelectric vibrator.
Alternatively, it is preferable that a density of the fixation base is greater than that of the piezoelectric vibrator.
According to the present invention, there is also provided An ink jet recording head, comprising:
a channel unit including:
a channel forming substrate, in which a channel which extends from a common ink reservoir to nozzle orifices via pressure chambers associated with the respective nozzle orifices; and
an elastic plate, a first surface thereof being bonded onto one surface of the channel forming substrate; and
a pair of vibrator units, each including a fixation base, and piezoelectric vibrators arranged on a first face of the fixation base such that first ends of the piezoelectric vibrators are fixed thereon and opposite free ends overhang a second face of the fixation base, the vibrator units arranged such that the free ends of the piezoelectric vibrators abut against a second surface of the elastic plate which is opposite to the first surface of the elastic plate, and such that third faces of the fixation bases which are opposite to the respective first faces are faced with each other.
In this configuration, the resin bulkhead portion provided in the housing space of the related configuration can be eliminated. Therefore, it is possible to efficiently accommodate the vibrator units in the casing.
Preferably, the third faces are bonded with each other via an adhesive layer.
Here, it is preferable that the adhesive layer is placed so as to include a first area which is opposite to an area on which the first ends of the piezoelectric vibrators are fixed.
Here, it is preferable that a recessed portion is formed on the third face of the fixation base so as to open at a fourth face of the fixation base which is opposite to the second face of the fixation base.
Further, it is preferable that the fixation bases are integrated such that the respective recessed portions faces with each other.
Preferably, there is defined a first gap between the third faces of the fixation bases so as to become narrow at a first area which is opposite to an area on which the first ends of the piezoelectric vibrators are fixed.
Preferably, the recording head further comprises a resin casing formed with a space for accommodating the vibrator units therein, a first face thereof being bonded onto the second surface of the elastic plate.
Here, it is preferable that a guide face is formed on an inner face of the casing for guiding the fixation bases when the vibrator units are accommodated in the casing.
Further, it is preferable that both widthwise end portions of the fixation base is guided by the guide face.
Besides, the fixation base and the guide face are bonded with adhesive.
Here, it is preferable that the guide face and a portion of the fixation base facing the guide face are separated such an extent that the adhesive cannot enter a gap defined therebetween.
Here, it is preferable that a portion of the guide face which faces an outermost piezoelectric vibrator is notched such an extend that the adhesive cannot enter the notched portion.
Besides, it is preferable that the second face of the fixation base is bonded onto the casing.
Preferably, a coefficient of linear expansion of the fixation base is substantially identical with that of the channel unit.
Preferably, the fixation base is made of at least one of stainless steel, ceramics and piezoelectric material.
Preferably, the adhesive is epoxy based adhesive.
Since the epoxy based adhesive has a low viscosity, it can be caused to easily flow into the gap. Furthermore, the adhesive can be solidified after the positioning. Therefore, the alignment of the vibrator unit can be reliably carried out and yield can be enhanced. Furthermore, great bonding force can be obtained after the bonding.
According to the present invention, there is also provided a method of manufacturing an ink jet recording head, comprising the steps of:
providing a channel unit including: a channel forming substrate, in which a channel which extends from a common ink reservoir to nozzle orifices via pressure chambers associated with the respective nozzle orifices; and an elastic plate, a first surface thereof being bonded onto one surface of the channel forming substrate;
providing a resin casing formed with an accommodation space therein;
bonding a first face of the casing unit onto a second surface of the elastic plate which is opposite to the first surface;
providing a pair of vibrator units, each including a fixation base, and piezoelectric vibrators arranged on a first face of the fixation base such that first ends of the piezoelectric vibrators are fixed thereon and opposite free ends overhang a second face of the fixation base; and
inserting the vibrator units into the accommodation space in the casing such that the free ends of the piezoelectric vibrators abut against a second surface of the elastic plate, and such that third faces of the fixation bases which are opposite to the respective first faces are faced with each other.
Preferably, the method further comprises the steps of: applying adhesive into the third faces of the fixation bases, before the inserting step; and solidifying the adhesive after the vibrator units are placed in the casing.
Alternatively, it is preferable that the method further comprises the steps of: forming a guide face on an inner face of the accommodation space in the casing, which is used to guide the fixation bases when the vibrator units are inserted into the accommodation space; applying adhesive between the fixation bases and the guide face; and solidifying the adhesive after the vibrator units are placed in the casing.