Patent Document

BACKGROUND OF THE INVENTION 
     The present invention relates to an ink jet recording head to be suitably used for a recording apparatus such as a printer or a plotter, and more particularly to an ink jet recording head comprising a case formed of resin which can accommodate a vibrator unit and a channel unit to be bonded to the distal end of the case. 
     A related ink jet recording head (which will be hereinafter referred to as a recording head) employs such a structure as to have a vibrator unit bonding a piezoelectric vibrator row to a fixation base, a case formed of resin which forms a housing space capable of accommodating the vibrator unit, and a channel unit to be bonded to the distal end portion of the case. 
     For example, the channel unit includes a nozzle plate having a plurality of nozzle orifices provided in a row, a channel forming substrate provided with an ink channel communicating with the nozzle orifice from a common ink reservoir via a pressure chamber, and an elastic plate for sealing one of the openings of the pressure chamber and the common ink reservoir, and is fabricated by integrating each of the members in a lamination state. The channel forming substrate is fabricated by etching a silicon wafer. A nozzle plate formed of stainless steel (SUS) is bonded to one face of the channel forming substrate, and the elastic plate is bonded to the other face thereof. The elastic plate is constituted by a composite plate member in which a support plate formed of stainless steel, in which a stainless layer is partially removed to form an island portion, is laminated on a resin film, for example. 
     Moreover, the free end of each piezoelectric vibrator is exposed to the outside of the case through an opening on the distal end side of the housing space. A distal end face of each piezoelectric vibrator is bonded to the island portion formed in the elastic plate. The free end is extendable to deform the elastic plate so that the volume of the pressure chamber is variable. Furthermore, the fixation base of the vibrator unit is formed of stainless steel and is bonded through adhesion to the internal wall face of the case formed of resin. 
     When a recording head having such a structure is placed for a long time in very, high humid environment the case is swelled. For example, as shown in FIG. 15, a case  1  is wholly swelled with the moisture absorption of the resin constituting the case  1 . As shown in FIG. 16, moreover, a channel unit  2  is bonded to the distal end face of the case  1 . Since the channel unit  2  has a channel forming substrate formed of silicon and a nozzle plate formed of stainless steel, the swelling is not caused by the moisture absorption. For this reason, the distal end side of the case  1  is constrained by the channel unit  2  so that the amount of deformation is decreased, and the amount of deformation is increased as being distant from the channel unit  2 . Accordingly, the proximal end side of the case  1  (that is, the attachment face side opposite to the channel unit  2 ) is greatly deformed. 
     Furthermore, since a fixation base  6  of a vibrator unit is also formed of metal such as stainless steel, the swelling is not caused by the moisture absorption. For this reason, the fixation base  6  and the case  1  which are bonded to each other deform due to the moisture absorption similarly to a bimetal phenomenon such that they are curved to be convex toward the outside of the case  1 . 
     As a result, mechanical stress is applied to the bonding interface of a piezoelectric vibrator  3  and an island portion  4  and that of a resin film portion  5  and the island portion  4 . More specifically, the fixation base  6  falls down toward the outside of the case  1  together with the case  1  so that the piezoelectric vibrator  3  also falls down. Consequently, mechanical stress is applied to the bonding interface. When the mechanical stress is excessively applied, the bonding interface is separated so that the recording head might be broken. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to enhance the connecting reliability of a piezoelectric vibrator unit. 
     In order to achieve the above object, according to the present inventions there is provided an ink jet recording head, comprising: 
     a vibrator unit, in which at least one piezoelectric vibrator is fixed on a base member in a cantilevered manner, such that a first region of the piezoelectric vibrator is fixed on a first face of the base member; and 
     a resin case, formed with a housing space extending through a first end face to a second end face thereof, the housing space including: 
     a first housing part, which opens to the first end face of the case, in which a part of the piezoelectric vibrator except for the first region is housed; 
     a second housing part, which continues to the first housing part, the second housing part defined by a first inner face extending in a first direction which is parallel with an extending direction of the piezoelectric vibrator, on which a first part of a second face of the base member which is opposite to the first face is bonded, and a second inner face extending in a second direction which is perpendicular to the first direction; on which a part of a third face which connects the first face and the first part of the second face is bonded; and 
     a third housing part, which continues to the second housing part, the third housing part being isolated from a part: of the base member which includes a second part of the second face. 
     Preferably, the recording head further comprises a channel unit which is provided on the first end face of the case such that free end face of the piezoelectric member is bonded thereon. 
     In the above configurations, the mechanical linkage of the base member and the case is eliminated in the third housing part, it is prevented the base member from inclining together with the swelling deformation of the resin case due to moisture absorption. Accordingly, it is possible to prevent the piezoelectric vibrator from separated from the base member due to mechanical stress application onto the bonding interface between the piezoelectric vibrator and the base member. As a result, it is possible to enhance the connecting reliability of the piezoelectric vibrator. 
     Preferably, the first part of the second face of the base member opposes to at least the first region of the piezoelectric vibrator. 
     In this configuration, it is secured a bonding region necessitately required for receiving reaction force with the motion of the piezoelectric vibrator. Consequently, it is possible to enhance the connecting reliability of the piezoelectric vibrator without damaging the jetting characteristic of ink drops. 
     Preferably, the second part of the second face of the base member is larger than the first part of the second face of the base member. 
     In this configuration, the base member can be easily held by a jig for mounting the vibrator unit into the case. Further, heat radiating effect can also be enhanced. 
     Preferably, inner wall faces of the case defining the third housing part is not bonded to the base member. 
     Here, it is preferable that the third housing part is defined by a third inner face extending from a boundary of the first part and the second part of the second face of the base member in the second direction, and a fourth inner face extending in the first direction to the second end face of the case. 
     In the above configurations, a part of the case formed with the third inner wall face acts to restrict the inclination of the base member due to the swelling. Furthermore, the space formed by the third and the fourth inner wall faces can be utilized to arrange components of the recording head in the space or can be utilized as a heat radiating space. Consequently, the degree of freedom for the design of the recording head can be increased. 
     Further, it is preferable that the recording head further comprises a circuit board mounted on the second end face of the case. An area defined by the third inner wall face is larger than a size of the circuit board. 
     Still further, it is preferable that a groove for holding ink therein is formed at a boundary of the third inner wall face and the fourth inner wall face. 
     Preferably, the case includes a flange member extending from the second and face thereof in the second direction. A positioning member is formed on a distal end portion of the flange member, which is abutted on a carriage member on which the recording head is mounted. 
     Preferably, the recording head further comprises a reinforcing plate member provided on a first part of an outer wall of the case the first part of the outer wall being a part opposing to at least the third housing part. 
     In this configuration, the swelling of the case due to moisture absorption can be restricted by the base member and the reinforcing plate member sandwiching the case therebetween. Therefore, the inclination of the base member due to the swelling deformation can be prevented more reliably. 
     Here, it is preferable that the reinforcing plate member extends so as not to extend to the first end face of the case. 
     Here, it is preferable that the reinforcing plate member extends to a position opposing to the second inner wall face of the case. 
     In the above configurations, a part of the case which is not covered by the reinforcing plate member is allowed to be swelled. Due to this swelling deformation, it is possible to reliably prevent such a drawback that the channel unit and the vibrator unit are separated in the first direction, thereby the connecting reliability of the piezoelectric vibrator can be enhanced. 
     Further, it is preferable that a Young&#39;s modulus of the reinforcing plate member is higher than a Young&#39;s modulus of the base member. 
     In this case, the reinforcing plate can be thinly fabricated so that the size of the recording head can be reduced. 
     Further, it is preferable that the base member and the reinforcing plate member are made of the same material. 
     In this case, the material characteristics of the reinforcing plate and the fixation base are equal to each other. Consequently, the easiness of the design can be obtained. 
     Here, it is preferable that a thickness of the reinforcing plate member is identical with a thickness of the base member. 
     Further, it is preferable that the reinforcing plate member is made of metal. 
     Here, it is preferable that the reinforcing plate member is made of stainless steel. 
     In this case, a necessary rigidity can be obtained while a processing can easily be carried out. Furthermore, it is also possible to efficiently radiate the heat of the recording head through the reinforcing plate. Moreover, there is no moisture permeability. Therefore, it is possible to prevent the swelling deformation of the case due to moisture absorption more reliably. 
     Preferably, the case is made of thermosetting resin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, and wherein: 
     FIG. 1 is a perspective view showing a recording head according to a first embodiment of the invention, as seen from a nozzle plate; 
     FIG. 2 is a perspective view showing the recording head as seen from a flange portion; 
     FIG. 3 is a perspective view showing a vibrator unit; 
     FIG. 4 is an exploded perspective view showing the recording head; 
     FIG. 5 is an enlarged section view showing a part of a channel unit; 
     FIG. 6 is an enlarged perspective view showing a connecting portion of a piezoelectric vibrator and an island portion; 
     FIG. 7 is a plan view showing the recording head; 
     FIG. 8 is a section view showing the recording head; 
     FIG. 9 is a partial section view showing the recording head; 
     FIG. 10 is a section view illustrating a modified example of the recording head; 
     FIG. 11 is an exploded perspective view showing a recording head according to a second embodiment of the invention; 
     FIG. 12 is a perspective view showing the recording head of FIG. 11, as seen from the flange portion side, 
     FIG. 13 is a section view illustrating the recording head of FIG. 11; 
     FIG. 14 is a section view illustrating a modified example of the recording head of FIG. 11; 
     FIG. 15 is a plan view illustrating a related recording head and an expansion state thereof; and 
     FIG. 16 is a section view illustrating the related recording head and the expansion state thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the invention will be described below with reference to the accompanying drawings. First, the whole structure of a recording head will be described. 
     As shown in FIGS. 1 and 2, a recording head  11  comprises: a vibrator unit  15  having a piezoelectric vibrator row  12 , a fixation base  13  and a flexible cable  14  which are integrated; a case  16  capable of accommodating the vibrator unit  15 ; and a channel unit  17  bonded to a distal end face of the case  16 . 
     The vibrator unit  15  will be described. As shown in FIG. 3, a piezoelectric vibrator  20  constituting the piezoelectric vibrator row  12  is formed like an elongated comb tooth in a vertical direction, and is separately cut to have a very small width of approximately 50 to 100 μm, for example. The piezoelectric vibrator  20  is constituted as a piezoelectric vibrator of a vertical oscillation type which can be extended in the vertical direction. In each of the piezoelectric vibrators  20 , a fixed end portion  21  is bonded onto the fixation base  13  so that a free end portion  22  is protruded outward from the distal end of the fixation base  13 . More specifically, the piezoelectric vibrator  20  is supported on the fixation base  13  in a cantilevered manner. Moreover, the length of the fixed end portion  21  is determined so as to be shorter than the length of the fixation base  13 . The fixed end portion  21  is bonded to the front portion (distal end portion) of the fixation base  13 . In other words, the rear side portion of the fixation base  13  is provided up to a portion provided behind the rear end of the fixed end portion  21 . 
     The distal end of the free end portion  22  in each of the piezoelectric vibrators  20  is bonded to an island portion  24  of the channel unit  17  as shown in FIG.  6 . 
     The flexible cable  14  is electrically connected to the piezoelectric vibrator  20  on the side face of the fixed end portion  21  which is opposite to the fixation base  13 . Moreover, the fixation base  13  supporting each of the piezoelectric vibrators  20  is constituted by a plate-shaped member including a rigidity capable of receiving reaction force from the piezoelectric vibrator  20 , preferably, metallic plate member. In the embodiment, the fixation base  13  is formed of a stainless steel plate having a thickness of approximately 1 mm and is provided to have a greater shape than that of the bonding region of the fixation base  13  and a non-bonded wall portion  46  which will be described below. 
     As shown in FIG. 8, the length of the fixation base  13  is determined such that a rear end face (proximal end side face) is positioned in the vicinity of a proximal end opening  23 A (which will be described below) of a housing space  23  when the vibrator unit  15  is placed therein. Consequently, the fixation base  13  can be held by a jig when the attachment of the vibrator unit  15  is performed. Further, heat radiation can also be enhanced. 
     Next, the channel unit  17  will be described. As shown in FIGS. 4 and 5, the channel unit  17  is constituted by a nozzle plate  25 , a channel forming substrate  26  and an elastic plate  27 . They are integrated through adhesion such that the nozzle plate  25  is provided on one side face of the channel forming substrate  26  and the elastic plate  27  is provided on the opposite side face thereof. 
     The nozzle plate  25  is a thin plate formed of stainless steel which has a plurality of nozzle orifices  28  provided in a row at a pitch corresponding to a dot formation density. In the embodiment, for example, 180 nozzle orifices are provided in a row, and two nozzle rows are arranged sideways. 
     The channel forming substrate  26  is a plate-shaped member in which a plurality of pressure chambers  33  are formed so as to be associated with the respective nozzle orifices  28 , while being divided by partition walls is formed in such a state that a space to be the pressure chamber  33  is divided by a partition wall. Further, a common ink reservoir  31  (see FIG. 8) and ink supply ports each of which is communicates the associated pressure chamber  33  with the common ink reservoir  31  are formed therein as hollowed spaces. The channel forming substrate  26  according to the embodiment is fabricated by etching a silicon wafer. 
     The pressure chamber  33  is formed to be an elongated chamber in a direction orthogonal to the direction in which the nozzle orifices  28  are arranged in a row. The ink supply port  32  is formed to be a constricted portion having a small passage width communicating between the pressure chamber  33  and the common ink reservoir  31 . Moreover, the common ink reservoir  31  serves to supply an ink stored in an ink cartridge (not shown) to each of the pressure chambers  33 . 
     The elastic plate  27  is a composite plate member having a double structure which is obtained by laminating a resin film  35  such as PPS (polyphenylene sulfide) on a support plate  34  formed of metal such as stainless steel, and serves as a diaphragm portion for sealing one of the open faces of the pressure chamber  33  and also serves as a compliance portion for sealing one of the open faces of the common ink reservoir  31 . As shown in FIG. 6, the support plate  34  in a portion serving as the diaphragm portion, that is, a portion corresponding to the pressure chamber  33  is subjected to etching to remove annularly, thereby forming the island portion  24  for bonding the distal end of the free end portion  22  of the piezoelectric vibrator  20 . The island portion  24  has the shape of an elongated block in a direction orthogonal to the direction of the arrangement of the nozzle orifices  28  in the same manner as the planar shape of the pressure chamber  33 . The resin film  35  provided around the island portion  24  serves as an elastic film. Referring to the portion serving as the compliance portion, that is, the portion corresponding to the common ink reservoir  31 , moreover, the support plate  34  portion is removed by the etching to leave only the resin film  35 . 
     Referring to the diaphragm portion, the island portion  24  is provided and the free end portion  22  of the piezoelectric vibrator  20  is bonded to the island portion  24  in the embodiment while the free end portion  22  may be directly bonded to the face of the resin film  35 . In this case, the bonding portion in the resin film  35  to the free end portion  22  acts as a vibrator bonding portion in the invention. Moreover, while adhesion is suitably used for the bond of the piezoelectric vibrator  20  and the island portion  24  because of easiness and convenience, it is not restricted but brazing (for example, soldering) may be used. 
     Next, the case  16  will be described. As shown in FIGS. 7 to  9 , the case  16  is a member formed of resin which is schematically constituted by a block-shaped main body  40  and a flange portion  41  extended from a proximal end of the main body  40  laterally. For the resin constituting the case  16 , a thermosetting resin is suitably used because a molding property is excellent, high dimensional precision can be obtained and a necessary rigidity can also be acquired. In the embodiment, the case  16  is formed of epoxy resin. 
     As shown in FIG. 7, the main body  40  is formed to have an almost rectangular shape as seen from the flange portion  41  side, that is, the proximal end side. The main body  40  is provided with a housing space  23  capable of accommodating the vibrator unit  15 . The housing space  23  is so formed as to communicate the distal end face of the main body  40  with the proximal end face thereof. In other words, the housing space  23  is formed as a hollowed space penetrating from a distal end side opening  23 B to a proximal end side opening  23 A in the height direction of the case  16 . The housing space  23  is provided for each vibrator unit  15 . For example, the recording head  11  according to the embodiment has two nozzle rows. Each nozzle row is provided with one vibrator unit  15 . Therefore, two housing spaces  23  are provided sideways. More specifically; each housing space  23  is formed in positions which are laterally symmetrical with respect to a center line CL in the direction of the short side of the main body  40 . 
     The housing space  23  is a continuous space including a first housing space  42  in which the piezoelectric vibrator row  12  is inserted, a second housing space  43  in which the fixation base  13  is inserted, and a relief concave portion  44  for forming a non-bonding region situated in the rear face portion of the fixation base  13  which is inserted into the second housing space  43 . 
     The first housing space  42  has a flat and rectangular opening which is long in the direction of a long side of the attachment face (proximal end face) of the case  16  and is short in the direction of a short side of the attachment face. The first housing space  42  is continuously formed in the height direction of the case  16  from the distal end face of the case  16  to the attachment face. A long-side opening width of the first housing space  42  is determined to be slightly greater than a length of the piezoelectric vibrator row  12  in the direction in which the piezoelectric vibrators  20  are arranged, and a short-side opening width is determined to be a double of the thickness of each piezoelectric vibrator  20 . 
     The second housing space  43  has a rectangular opening shape which is long in the direction of the long side of the attachment face and is short in the direction of the short side of the attachment face. The second housing space  43  extends from the attachment face to a position which is closer to the attachment face than the distal end face of the case  16 . More specifically, a bottom face  43   a  of the second housing space  43  is provided in a position closer to the attachment face by a length which is slightly smaller than the length of the free end portion  22  of the piezoelectric vibrator  20  from the distal end face of the case  16 . A long-side opening width of the second housing space  43  is determined to be almost equal to the width of the fixation base  13 , and is slightly greater than the long-side opening length of the first housing space  42 . Moreover, a short-side opening width of the second housing space  43  is determined to be almost equal to the thickness of the fixation base  13 , more specifically, to be slightly smaller than the thickness of the fixation base  13 . 
     The second housing space  43  is provided on the outside of the first housing space  42 , that is, the side positioned apart from the center line CL in while communicating with the first housing space  42 . The wall face defining the second housing space  43  acts as a bonding face to which the fixation base  13  of the vibrator unit  15  is bonded as will be described below. In the main body  40 , accordingly, a portion positioned on the outside of the wall face, that is, a portion shown in hatching of a two-dotted line in FIG. 7 serves as a non-bonded wall portion  46 . 
     Moreover, since the centers in a longitudinal direction of the openings in the second housing space  43  and the first housing space  42  are aligned with each other, both ends in the longitudinal direction of the opening of the second housing space  43  are outwardly protruded in comparison with both ends of the first housing space  42 . In other words, the second housing space  43  is formed as a groove in the case  16  so as to define the protruded lateral ends. 
     The relief concave portion  44  has a rectangular opening shape which is long in the direction of the long side of the attachment face, and is short in the direction of the short side of the attachment face. The relief concave portion  44  extends from the attachment face to a position which is slightly closer to the attachment face than the bottom face  43   a  of the second housing space  43 . More specifically, a bottom face  44   a  of the relieve concave portion  44  is positioned between a position at which is a half of a length in the height direction of the case  16  and a position at which is slightly closer to the attachment face than the bottom face  43   a  of the second housing space  43 . The long-side opening width of the relieve concave portion  44  is determined to be slightly smaller than the long-side opening width of the second housing space  43 , and is almost equal to the long-side opening width of the first housing space  42 . Moreover, the short-side opening width of the relieve concave portion  44  is determined such that a sufficient clearance can be formed with respect to the back face of the fixation base  13 , and is almost equal to the short-side opening width of the second housing space  43 . 
     The relief concave portion  44  is provided on the outside of the second housing space  43  (the side positioned apart from the center line CL) while communicating with the second housing space  43 . In other words, the relief concave portion  44  is fabricated by recessing or retracting backward most of the face of the non-bonded wall portion  46  in the thickness direction of the fixation base  13 . For this reason, a region in which the relief concave portion  44  on the internal wall of the case is provided acts as a non-bonding area which is apart from the fixation base  13 . Accordingly, the bonding face is formed by regions S 1  defined by the relief concave portion  44  (see FIGS. 7 and 9) and a region S 2  defined by the second housing space  43  (see FIG.  8 ). 
     The regions S 1  are determined to be a portion having a very small width (approximately 0.5 mm). Moreover, the region S 2  is a step wall face to be formed by a step of the bottom face  43   a  of the second housing space  43  and the bottom face  44   a  of the relief concave portion  44 . The height dimension of the region S 2  is approximately 2 to 3 mm. In connection with the height direction of the case  16 , the region S 2  is provided in a region corresponding to the bonding region of the fixed end portions  21  of the piezoelectric vibrators  20  and the fixation base  13  in the vibrator unit  15  (more specifically, the region S 2  opposed at least a part of the bonding region of the fixed end portions  21 ). In other words, the region S 2  is determined to a position and an area which are necessarily required to receive reaction force with the motion of the piezoelectric vibrator  20 . 
     In the embodiment, moreover, the bottom face  43   a  of the second housing space  43  also serves as the bonding region of the fixation base  13  (the region S 3 ) in addition to the bonding regions S 1  and S 2 . In other words, the distal end face of the fixation base  13  is bonded to the internal wall of the main body  40 . A clearance formed between the bottom face  43   a  and the distal end face of the fixation base  13  is determined to 0.04 mm, for example, and has such a size as to obtain capillary force for fluidizing an influent adhesive. 
     In order to attach the vibrator unit  15  to the housing space  23  having such a structure, first of all, the adhesive is thinly applied onto the distal end face of the free end portion  22  of the piezoelectric vibrator  20 . If the adhesive is applied, the fixation base  13  is held by a jig and the vibrator unit  15  is inserted from the proximal end side opening  23 A of the housing space  23  in such an attitude that the free end portion  22  is first inserted. The distal end of the free end portion  22  is caused to face the distal end side opening  23 B of the housing space  23  and is positioned in such a state as to abut on the face of the associated island portion  24 . In this state, the bonding regions S 1 , S 2  and S 3  between the fixation base  13  and the internal wall of the case are filled with the adhesive. For example, the adhesive having a fluidity is injected into the side edge region S 1  from the attachment face side of the case  16 , and the influent adhesive is filled in the side edge region S 1 , the distal end side region S 2  and the distal end face region S 3  by utilizing the capillarity. If each bonding region is filled with the adhesive, the adhesive on the distal end of the free end portion  22  and the adhesive in the bonding region are cured. For example, the adhesives are left for a proper time in such a state that they are heated to a predetermined temperature. Consequently, the fixation base  13  is bonded to the internal wall of the case (the bonding regions), while the distal end of the free end portion  22  is bonded to the island portion  24 . 
     Since the bottom face  43   a  is also used as a bonding region for the fixation base  13 , reaction force generated by the deformation of the piezoelectric vibrator  20  and transmitted from the channel unit  17  to the main body  40  can be received by the fixation base  13 . For this reason, the undesired vibration of the recording head  11  due to the deformation of the piezoelectric vibrator  20  can be more reduced in comparison with the case in which the distal end face of the fixation base  13  is provided apart from the main body  40  as shown in FIG.  16 . 
     Moreover, a reinforcing plate  45  is provided on an outer peripheral face of the main body  40  so as to extend from the flange portion  41  to a position where opposes the, bonding region of the fixed end portions  21  of the piezoelectric vibrators  20  and the fixation base  13 . Specifically, the reinforcing plate  45  extends to a position where is closer to the attachment face than the distal end face of the case  16 . More specifically, the reinforcing plate  45  extends to a position where is closer to the attachment face than a distal end face of the fixation base  13 . As shown in FIG. 7, the width of the reinforcing plate  45  is so determined as to be wide enough to cover the non-bonded wall portion  46 . 
     The reinforcing plate  45  serves as a member for restricting the swell of the case  16  due to moisture absorption and serves to prevent the moisture absorbing case  16  from being swelled outward. For this reason, a plate member which is more difficult to be swelled due to the moisture absorption than the resin case  16  is used for the reinforcing plate  46 . Moreover, the reinforcing plate  45  is provided in a region corresponding to the bonding region of the fixation base  13  and the internal wall of the case. In order to restrict the swell of the case  16 , it is desirable that the rigidity of the reinforcing plate  45  should be equal to or higher than that of the fixation base  13 . 
     Accordingly, a plate member formed of metal which is not swelled by the moisture absorption, has a high rigidity and can easily be processed is suitably used for the reinforcing plate  45 . In the embodiment, a stainless steel plate to be a plate member formed of the same material as that of the fixation base  13  is used, and the thickness of the reinforcing plate  45  is determined to be equal to that of the fixation base  13 . Thus, when a plate member formed of the same material is used for the reinforcing plate  45  and the fixation base  13 , the material characteristics of the reinforcing plate  45  and the fixation base  13  are equal to each other. Consequently, a design can easily be carried out. Moreover, if the reinforcing plate  45  is formed of metal, the heat of the recording head  11  can be discharged efficiently to the outside. 
     If the reinforcing plate  45  is constituted by a material having a higher rigidity than that of the fixation base  13  (that is, a greater Young&#39;s modulus), the reinforcing plate  45  can be formed thinly. Therefore, it is advantageous in that the size of the recording head  11  can be reduced. 
     Moreover, while the reinforcing plate  45  is fixed to the main body  40  by adhesion, the reinforcing plate  45  can be fixed to the main body  40  by any method if possible. For example, the reinforcing plate  45  may be fixed by calking or may be held in a holding groove provided in the main body  40 . Alternatively, the reinforcing plate  45  may be insert molded in the main body  40 , that is, be non-bonded wall portion  46 . In the case in which the reinforcing plate  45  is fixed by the adhesion, the adhesive of the reinforcing plate  45  can be cured at the step of curing the adhesive of the fixation base  13  so that the process can be simplified. 
     Next, description will be given to the advantages of the recording head  11  having the structure described above, more specifically, the advantages obtained when the recording head  11  is placed for a long time in very high humid environment. 
     Since the relief concave portion  44  is formed so that the non-bonded wall portion  46  is isolated from the fixation base  13  except for the bonding, regions S 1 , and the fixation base  13  is mainly bonded with the case  16  at the distal end side (the bonding region S 2 ), even in a case where the non-bonded wall portion  46  is swelled outwardly due to the moisture absorption, the fixation base  13  is prevented from inclining together with the non-bonded wall portion  46 . Accordingly, it is possible to prevent such a drawback that the bonding interface of the piezoelectric vibrator  20  and the island portion  24  is separated. As a result, the connecting reliability of the piezoelectric vibrator  20  can be enhanced. 
     Moreover, the bonding region S 2  is provided in a region corresponding to the bonding region of the fixed end portions  21  of the piezoelectric vibrators  20  and the fixation base  13 . Therefore, it is possible to maintain a region necessarily required for receiving reaction force generated by the motion of the piezoelectric vibrator  20 . Consequently, the connecting reliability of the piezoelectric vibrator  20  can be enhanced without damaging the jetting characteristic of ink drops. 
     Furthermore, since a part of the outer wall of the case  16  is sandwiched by the reinforcing plate  45  and the fixation base  13  as shown in FIG. 8, it is possible to restrict the swelling of the sandwiched portion of the case  16 . 
     Consequently, the proximal end portion of the case  16  is not expanded toward the side so that the fixation base  13  can be reliably prevented from inclining together with the non-bonded wall portion  46 . Accordingly, it is possible to prevent mechanical stress from being applied to, the bonding interface of the piezoelectric vibrator  20  and the island portion  24  due to the inclination of the vibrator unit  15 , and mechanical stress from being applied to the bonding interface of the resin film  35  and the island portion  24 . Further, it is possible to prevent such a drawback that these bonding interfaces are separated. As a result, the connecting reliability of the piezoelectric vibrator  20  can be enhanced. 
     Moreover, since both the fixation base  13  and the reinforcing plate  45  are formed of metal (stainless steel) which does not absorb moisture, it is also possible to cause the non-bonded wall portion  46  to absorb moisture with difficulty. 
     Since the distal end of the reinforcing plate  45  is situated at a position where is closer to the attachment face than the distal end face of the case  16 , the distal end portion of the case  16  is not restricted by the reinforcing plate  45 . Therefore, this portion is permitted to expand outwards as indicated by the dashed line of FIG.  8 . However, since the expanded portion is provided close to the bonding regions S 2  and S 3 , the swelling less influences the inclination of the vibrator unit  15 . 
     By allowing the distal end portion of the case to expand outward, the positional relationship between the channel unit  17  and the vibrator unit  15  in the height direction of the case  16  can be maintained even in the swelling is occurred. Consequently, it is also possible to reliably prevent such a drawback that the channel unit  17  and the vibrator unit  15  are separated from each other in the height direction of the case  16  by the swelling of the case  16 . Also in this respect, the connecting reliability of the piezoelectric vibrator  20  can be enhanced. 
     The reinforcing plate  45  may be extended to the position indicated as a dashed line L in FIG. 8 so that the distal end of the reinforcing plate  45  is aligned with the distal end face of the fixation base  13  in the height direction of the case  16 , thereby covering a region corresponding to the bonding region of the fixation base  13  and the case  16 . 
     Moreover, the reinforcing plate  45  may be configured to surround the side faces of the main body  40 . With such a structure, the swelling of the case  16  can be more reliably prevented. 
     As shown in FIG. 10, moreover, it is also possible to employ such a structure that the reinforcing plate  45  is not provided but only the relief concave portion  44  is provided. Also in this configuration, the non-bonded wall portion  46  is substantially isolated from the fixation base  13 , and the fixation base is bonded with the case  16  only at the distal end portion thereof which is closer to the channel unit  17 . As shown in a dashed line, therefore, even if the case  16  is swelled outward, the fixation base  13  can be prevented from inclining together with the non-bonded wall portion  46  so that mechanical stress can be prevented from being applied to the bonding interface of the piezoelectric vibrator  20  and the island portion  24  due to the inclination of the vibrator unit  15 . 
     The invention is not restricted to the above configuration. Next, a second embodiment of the invention will be described with reference to FIGS. 11 to  14 . 
     As shown in FIGS. 11 and 12, a recording head  50  according to the second embodiment comprises a vibrator unit  15 ; a case  51  capable of accommodating the vibrator unit  15 ; and a channel unit  17  to be bonded to a distal end face of the case  51 . In the recording head  50  according to the embodiment, the shape of the case  51  is mainly different from that of the first embodiment. The difference will be mainly described below. 
     In the second embodiment, the same members as those in the first embodiment have the same reference numerals and description thereof will be omitted. 
     As shown in FIG. 13, the case  51  is roughly constituted by a main body  52  and a flange portion  53  and is formed of epoxy resin to be a kind of thermosetting resin. The main body  52  is constituted by a distal end portion  55  provided with a housing space  54  and a box-shaped proximal end portion  56  opened on an attachment face. The proximal end portion  56  is constituted by a bottom plate portion  64  extended laterally and an upright wall portion  65  upright from the outside edge portion of the bottom plate portion  64  toward the attachment face side of the case  51 . Moreover, the flange portion  53  is extended from the proximal end of the upright wall portion  65  laterally. A positioning projection  58  to abut on a carriage member  57  is formed on the lower face of the flange portion  53  (that is, a face on the channel unit  17  side). The positioning projection  58  serves as a positioning member and is constituted by a flat and circular projection, for example. Thus, the positioning projection  58  is provided on the flange portion  53  and a distance from the flange portion  53  on one of sides to the flange portion  53  on the opposite side can be set to be large by causing the positioning projection  58  to abut on the carriage member  57 , and positional precision in a horizontal direction can be enhanced when attaching the recording head  50  to the carriage member  57 . 
     The distal end portion  55  of the main body  52  has the shape of a rectangular parallelepiped which has a height slightly greater than the length of each piezoelectric vibrator  20 , and the distal end face having the channel unit  17  bonded thereto is a size larger than the channel unit  17 . Moreover, the housing space  54  is a through hole portion which is continuously formed to penetrate the inside of the distal end portion  55  in the height direction of the case  51 . The recording head  50  according to the embodiment also has two nozzle rows and each nozzle row is provided with one vibrator unit  15 . Therefore, two housing spaces  54  are provided sideways. 
     The housing space  54  is a continuous space including a first housing space  59  in which a piezoelectric vibrator row  12  is to be inserted and a second housing space  60  in which a fixation base  13  is to be inserted. The first housing space  59  has a flat and rectangular opening which is long in the direction of a long side of the distal end portion  55  and is short in the direction of a short side of the distal end portion  55 . The first housing space  59  is formed continuously in the height direction of the case  51  so as to extend from the distal end face of the distal end portion  55  to the bottom plate portion  64  of the proximal end portion  56 . The second housing space  60  also has a rectangular opening shape which is long in the direction of a long side of the distal end portion  55  and is short in the direction of a short side of the distal end portion  55 . The second housing space  60  is formed continuously so as to extend from the bottom face of the proximal end portion  56  to a position in the distal end portion  55  which is slightly closer to the bottom plate portion  64  than the distal end face of the distal end portion  55 . 
     The wall face defining the second housing space  60  also acts as a bonding face S 4  to which the fixation base  13  of the vibrator unit  15  is bonded. Accordingly, a wall portion of the main body  52  corresponding to the bonding face S 4  serves as a base-bonded wall portion  61 . 
     In order to attach the vibrator unit  15  to the housing space  54  having such a structure, first of all, an adhesive is thinly applied onto the distal end face of a free end portion  22  of the piezoelectric vibrator  20 , and the vibrator unit  15  is inserted in the housing space  54  such that the free end portion  22  is first inserted. Then, the distal end of the free end portion  22  is positioned in such a state as to abut on the face of a corresponding island portion  24  and bonding faces S 3  and S 4  provided between the fixation base  13  and the internal wall of the case are filled with the adhesive. Consequently, the distal end portion of the fixation base  13  is bonded to the internal wall of the case and the distal end of the free end portion  22  is bonded to the island portion  24 . 
     In the proximal end portion  56 , a space  66  is defined by the bottom plate portion  64  and the upright wall portion  65 . The opening area of the space  66  is defined depending on the size of the bottom plate portion  64  and a volume is defined by the size of the bottom plate portion  64  and the height of the upright wall portion  65 . The inside of the space  66  can be used for various purposes, for example, accommodates the components of the recording head  50 . 
     In the embodiment, the space  66  is used as a space for accommodating the upper half portion of the vibrator unit  15  and is also used as a heat radiating space for discharging heat from the piezoelectric vibrator  20 . For this reason, the height of the upright wall portion  65  is determined to be slightly greater than that of the fixation base  13  which is disposed state. As shown in FIGS. 12 and 13, moreover, the opening area of the space  66  is determined to be larger than the area of a circuit board  67  provided on the attachment face side of the case  51 , and a clearance  66   a  which is not covered with the circuit board  67  but communicates with the outside is formed on the opening of the space  66 . With such a structure, the heat generated from the piezoelectric vibrator  20  is transmitted through the fixation base  13  and is discharged into the space  66  of the proximal end portion  56 , and furthermore, is discharged to the outside of the case  51  through the clearance  66   a  with the circuit board  67 . 
     Also in the second embodiment having such a structure, it is possible to prevent the vibrator unit  15  from inclining due to the swell of the case  51  and to enhance the connecting reliability of the piezoelectric vibrator  20 . 
     More specifically, when the case  51  is placed for a tong time in very high humid environment, it absorbs a moisture and is swelled. However, since the proximal end portion  56  serving as a non-bonded wall portion is isolated from the fixation base  13 , the vibrator unit  15  can be prevented from inclining. 
     Moreover, the bottom plate portion  64  extending laterally acts so as to restrict the inclination of the fixation base  13  due to the swelling of the case  51 . Specifically, although the bottom portion  64  is also swelled due to the moisture absorption, the swelling restricts the inclination of the fixation base  13  because the swelling direction of the bottom plate portion  64  is opposite to the inclining direction. 
     In the embodiment furthermore, the space  66  is formed by the bottom plate portion  64  and the upright wall portion  65 . Therefore, the components of the recording head  50  can be provided in the space  66 . Consequently, the degree of freedom for the design of the recording head  50  can be increased. 
     As shown in FIG. 14, moreover, an ink holding groove  68  capable of holding an ink may be provided in the space  66 , specifically, in the boundary portion of the bottom plate portion  64  and the upright wall portion  65 . 
     In a recording apparatus comprising the ink jet recording head  50  of this kind, there is a problem in that an ink drop is caused to fly in a very small amount and is therefore changed into mist. The ink mist floats in the apparatus. Therefore, if the ink mist sticks to a carriage or a housing, it might be changed into a large ink drop. The large ink drop thus generated might enter a clearance between the recording head  50  and the carriage by capillary force, thereby contaminating and damaging the recording head  50 . 
     When the ink holding groove  68  is provided in the boundary portion of the bottom plate portion  64  and the upright wall portion  65 , the ink entering from the outside and flowing down through the upright wall portion  65  can be held in the ink holding groove  68 . Consequently, it is possible to prevent such a drawback that the ink reaches the vibrator unit  15 . 
     Referring to the ink holding groove  68 , the inside edge portion of the bottom plate portion  64  is scraped in the direction of a thickness to provide a concave groove  69  and a rib  70  is protruded to form a relatively deep groove in FIG. 14, while only the concave groove  69  may be provided or only the rib  70  may be protruded. 
     The invention is not restricted to the embodiments described above but may be variously changed based on the appended claims. 
     For example, while the non-bonded wall portion  46  is concaved to partially bond the fixation base  13  in the first embodiment, the thickness of the fixation base  13  in the portion corresponding to the bonding region may be set to be greater than that of other portions to partially bond the fixation base  13 . In the case in which the non-bonded wall portion  46  is concaved to form a non-bonding region to the fixation base  13 , the relief concave portion  44  can easily be fabricated by molding. 
     In the recording head  11  having three or more vibrator units  15 , moreover, a partitioning wall portion formed between the housing spaces  23  also serves as the base-bonded wall portion. In such a structure that the reinforcing plate  45  is provided, the same advantageous effects as described in the first embodiment can be obtained by insert molding the reinforcing plate  45  in the partitioning wall portion.

Technology Category: 7