Patent Publication Number: US-8113632-B2

Title: Liquid ejecting head, liquid ejecting head unit, and liquid ejecting apparatus

Description:
The entire disclosure of Japanese Patent Application No: 2010-073838, filed Mar. 26, 2010 are expressly incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid ejecting head which ejects liquid from nozzle orifices, a liquid ejecting head unit, and a liquid ejecting apparatus and, in particular, to an ink jet type recording head which discharges ink as liquid, an ink jet type recording head unit, and an ink jet type recording apparatus. 
     2. Related Art 
     As a representative example of a liquid ejecting head, for example, an ink jet type recording head is known which discharges ink droplets from nozzle orifices by using pressure occurring by displacement of piezoelectric elements. In the ink jet type recording head, a portion of a pressure generation chamber communicating with the nozzle orifice is constituted by a vibration plate and an ink droplet is discharged from the nozzle orifice by providing pressure to ink supplied to the pressure generation chamber, by deformation of the vibration plate by the piezoelectric element. 
     Also, with respect to such an ink jet type recording head, there is proposed an ink jet type recording head in which a piezoelectric element is fixed at one end portion thereof to a vibration plate and at the other end portion to a fixed plate, the fixed plate is fixed to a case, thereby holding the piezoelectric element, and an ink droplet is discharged by generating a pressure change in a pressure generation chamber by deforming the vibration plate by extension and contraction in the axial direction of the piezoelectric element. 
     In such an ink jet type recording head, since the case is formed by molding of a resin material, there is a problem such that rigidity is low, so that a repulsive force when driving the piezoelectric elements cannot be suppressed. In particular, in a case where the piezoelectric elements are fixed to a housing portion penetrating the case, since at both end portions in a juxtaposition direction of the piezoelectric elements of the case, rigidity is high due to wall surfaces of the housing portion and at the central portion in the juxtaposition direction thereof, rigidity is low, the repulsive force due to driving of the piezoelectric elements cannot be uniformly suppressed, so that the recording head cannot be driven with uniform ink discharge characteristics. 
     For this reason, there is proposed an ink jet type recording head in which a reinforcing plate made of metal is buried in a case made of a resin material over a juxtaposition direction of piezoelectric elements, whereby the case is reinforced by the reinforcing plate (refer to JP-A-2001-293862 and JP-A-2001-71486, for example). 
     In this manner, in a case where the reinforcing plate is buried in the case, the reinforcing plate must be positioned at a predetermined position of a mold which molds the case. For this reason, since the case is molded while a portion of the reinforcing plate is held for positioning, the reinforcing plate is provided in a state where the portion of the reinforcing plate is exposed from the case. Such exposed portions of the reinforcing plate exposed from the case are provided at four sides of the periphery of a plate-like member having a rectangular shape. However, since it is not preferable that the exposed portions be present at the adhesion surface side of the case to the flow path unit, the exposed portions are provided at two corner portions on the discharge face side of the side faces and one side on the opposite side to the discharge face. 
     However, since the two corner portions on the discharge face side are close to the discharge face, some ink discharged from the nozzle orifice adheres to the discharge face and the ink adhered to the discharge face creeps up to the corner portions. The ink which has crept to the corner portions in this manner reaches the exposed portion on the opposite side to the discharge face through an interface between the molded resin of the case and the reinforcing plate and then penetrates from the exposed portion on the opposite side to the discharge face into the housing portion in the case, in which the actuator unit is housed, consequently there is a problem in that the actuator unit is damaged by the penetrated ink. 
     In addition, such a problem is also similarly present in a liquid ejecting head, which ejects liquid other than ink, as well as the ink jet type recording head. 
     SUMMARY 
     An advantage of some aspects of the invention is that it provides a liquid ejecting head, in which penetration of liquid is suppressed, thereby allowing damage of an actuator to be suppressed, a liquid ejecting head unit, and a liquid ejecting apparatus. 
     According to a first aspect of the invention, there is provided a liquid ejecting head including: a flow path unit in which nozzle orifices and flow paths communicating with the nozzle orifices are provided; a case fixed to the flow path unit; and an actuator unit which is fixed to the case and in which actuators that generate a pressure change in the flow paths are juxtaposed, wherein the case is formed by a resin molding material and also a reinforcing plate is buried in the case over a juxtaposition direction of the actuators, first exposed portions in which the reinforcing plate is exposed are provided at a face on the opposite side to a face of the case, which is fixed to the flow path unit, concave portions are provided at both side faces of the reinforcing plate in the juxtaposition direction of the actuators on a discharge face side in which the nozzle orifices are opened, and second exposed portions, in which corner portions that include the discharge face sides of convex portions formed by the concave portions and the side faces of the reinforcing plate are exposed, are provided at both side faces of the case in the juxtaposition direction of the actuators. 
     In such an aspect, since the concave portions are provided at the reinforcing plate, whereby the corner portions which are exposed by the second exposed portions are disposed at the opposite side to the discharge face, arrival of liquid or the like adhered to the discharge face at the reinforcing plate exposed by the second exposed portions can be suppressed. Accordingly, adhesion of liquid which has crept an interface between the reinforcing plate exposed by the second exposed portions and the case, to the actuator unit held by the case from the first exposed portions is suppressed, so that damage of the actuators by liquid can be suppressed. 
     Here, cutout portions which are opened to a face on the opposite side to the discharge face may be provided at both side faces of the reinforcing plate in the juxtaposition direction of the actuators on the opposite side to the concave portions, and the convex portion may be provided between the concave portion and the cutout portion. 
     Also, it is preferable that at a discharge face side of the flow path unit a cover head which covers the discharge face be provided and the corner portions be covered by the cover head. Accordingly, the discharge face side can be protected by the cover head. Also, even if liquid penetrates between the cover head, the flow path unit, and the case, since the reinforcing plate exposed by the second exposed portions is located away from the discharge face, contact of the penetrated liquid with the reinforcing plate can be suppressed. 
     Also, it is preferable that the cover head be provided such that a clearance between the cover head and the case gradually increases from the discharge face toward the case side. Accordingly, creeping of liquid penetrated between the case and the cover head to the opposite side to the flow path unit is suppressed, so that contact of the penetrated liquid with the reinforcing plate can be suppressed. 
     Also, according to a second aspect of the invention, there is provided a liquid ejecting head unit including a plurality of the liquid ejecting heads according to the first aspect. 
     In such an aspect, a liquid ejecting head unit can be realized in which damage of the actuators is suppressed, whereby reliability is improved. 
     Also, according to a third aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head according to the first aspect or the liquid ejecting head unit according to the second aspect. 
     In such an aspect, a liquid ejecting apparatus can be realized in which damage of the actuators is suppressed, whereby reliability is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is an exploded perspective view of a recording head related to Embodiment 1 of the invention. 
         FIG. 2  is a top view of the recording head related to Embodiment 1 of the invention. 
         FIG. 3  is a cross-sectional view of the recording head related to Embodiment 1 of the invention. 
         FIG. 4  is a cross-sectional view of the recording head related to Embodiment 1 of the invention. 
         FIG. 5  is a cross-sectional view of the recording head related to Embodiment 1 of the invention. 
         FIGS. 6A and 6B  are cross-sectional views showing a manufacturing method of a case related to Embodiment 1 of the invention. 
         FIG. 7  is a cross-sectional view showing the recording head related to Embodiment 1 of the invention. 
         FIG. 8  is a cross-sectional view showing a comparative example of the recording head related to Embodiment 1 of the invention. 
         FIG. 9  is a cross-sectional view showing a modified example of a reinforcing plate related to another embodiment of the invention. 
         FIG. 10  is a view showing a schematic configuration of a recording apparatus related to one embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, the invention will be described in detail on the basis of embodiments. 
     Embodiment 1 
       FIG. 1  is an exploded perspective view of an ink jet type recording head which is one example of a recording head related to Embodiment 1 of the invention,  FIG. 2  is a top view of the ink jet type recording head,  FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 ,  FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 2 , and  FIG. 5  is a cross-sectional view taken along line V-V of  FIG. 2 . 
     As shown in  FIG. 1 , an ink jet type recording head  1  (hereinafter also referred to as a recording head  1 ) of this embodiment includes a pair of actuator units  2 , a case  4  made of a resin material and provided with housing portions  3  capable of housing the actuator units  2  in the inside, a flow path unit  5  joined to a leading end face of the case  4 , and a cover head  6  which covers the flow path unit  5  side. 
     As shown in  FIGS. 3 and 4 , the actuator unit  2  of this embodiment includes a piezoelectric element forming member  13  in which a plurality of piezoelectric elements  11  that is an actuator of this embodiment is juxtaposed in the width direction thereof, and a fixed plate  14  in which a base end portion (the other end portion) side of the piezoelectric element forming member  13  is joined thereto as a fixed end such that a leading end portion (one end portion) side of the piezoelectric element forming member  13  becomes a free end. 
     The piezoelectric element forming member  13  is formed by alternately sandwiching and laminating a piezoelectric material layer  15  and internal electrodes constituting two poles of the piezoelectric element  11 , that is, an individual internal electrode  16  constituting an individual electrode electrically independent from an adjacent piezoelectric element  11 , and a common internal electrode  17  constituting a common electrode electrically common to an adjacent piezoelectric element  11 . 
     In the piezoelectric element forming member  13 , a plurality of slits  18  is formed, for example, by a wire saw or the like and the leading end portion side thereof is carved in a comb-teeth shape, so that a row of piezoelectric elements  11  is formed. In addition, positioning portions  19  having a width wider than that of each piezoelectric element  11  are provided at both outer sides of the row of piezoelectric elements  11 . Although the positioning portions  19  are formed by the piezoelectric element forming member  13  similarly to the piezoelectric elements  11 , the positioning portions are non-driven vibrators, which are not substantially driven, and are for positioning the actuator unit  2  with high precision by bringing the positioning portions  19  into contact with side surfaces of the housing portion  3  provided at the case  4 , when incorporating the actuator unit  2  into the recording head  1 . 
     Here, a region of the piezoelectric element  11 , which is joined to the fixed plate  14 , is an inactive region which does not contribute to vibration, and if voltage is applied between the individual internal electrode  16  and the common internal electrode  17 , which constitute the piezoelectric element  11 , only a region on the leading end portion side, which is not joined to the fixed plate  14 , vibrates. Then, the leading end face of the piezoelectric element  11  is fixed to an island portion  49  of a vibration plate  46 , which will be described later, through an adhesive agent or the like. 
     Also, a circuit substrate  30  such as a COF, on which a driving circuit  29  such as a driving IC for driving the piezoelectric element  11  is mounted, is connected to each piezoelectric element  11  of the actuator unit  2 . 
     The flow path unit  5  includes a flow path forming substrate  40 , the vibration plate  46 , and a nozzle plate  48 . 
     The flow path forming substrate  40  is composed of a silicon single crystal substrate, and at a surface layer portion on one face side thereof, pressure generation chambers  42  partitioned by a plurality of partition walls  41  are juxtaposed in the width direction (a short side direction) thereof. 
     Also, as shown in  FIG. 3 , a manifold  44  for supplying ink which is one example of a liquid to each pressure generation chamber  42  is communicated with one end portion side in the longitudinal direction of each pressure generation chamber  42  through an ink supply path  45  which is one example of a liquid supply path. Also, an opening face side of the pressure generation chamber  42  of the flow path forming substrate  40  is sealed by the vibration plate  46 , and to the other face side, the nozzle plate  48  which is one example of a nozzle forming member in which nozzle orifices  47  are perforated is adhered through an adhesive agent or a thermal welding film. The nozzle orifice  47  of the nozzle plate  48  and the pressure generation chamber  42  communicate with each other through a nozzle orifice communication hole  43  provided penetrating the flow path forming substrate  40 . 
     The vibration plate  46  is formed, for example, by a composite plate of an elastic film  46   a  which is a first member composed of an elastic member such as a resin film and a support plate  46   b  which is a second member supporting the elastic film  46   a  and made of a metal material or the like, for example, and the elastic film  46   a  side is joined to the flow path forming substrate  40 . For example, in this embodiment, the elastic film  46   a  which is the first member is composed of a PPS (polyphenylene sulfide) film having a thickness in the order of several μm and the support plate  46   b  which is the second member is composed of a stainless steel plate (SUS) having a thickness in the order of several tens of μm. 
     Also, in a region facing each pressure generation chamber  42  of the vibration plate  46 , the island portion  49  with which the leading end portion of the piezoelectric element  11  comes into contact is provided. That is, at a region facing a peripheral portion of each pressure generation chamber  42  of the vibration plate  46 , a thin-walled portion  50  which is thinner in thickness than other regions is formed, and in the inside of the thin-walled portion  50 , each island portion  49  is provided. To such an island portion  49 , the leading end portion of the piezoelectric element  11  of the above-mentioned actuator unit  2  is fixed through an adhesive agent or the like, for example. 
     Also, a compliance portion  54  which is substantially constituted only by the elastic film  46   a  by removing the support plate  46   b  by etching, similarly to the thin-walled portion  50 , is provided at a region facing the manifold  44  of the vibration plate  46 . In addition, the compliance portion  54  plays a role of normally maintaining constant pressure in the manifold  44  by absorbing a pressure change by deformation of the elastic film  46   a  of the compliance portion  54  when a pressure change occurs in the manifold  44 . 
     In addition, in this embodiment, the vibration plate  46  is constituted by the elastic film  46   a  and the support plate  46   b  and a surrounding portion of the island portion  49  and the compliance portion  54  are constituted only by the elastic film  46   a . However, it is not particularly limited thereto, and the island portion  49  and the compliance portion  54  may be formed, for example, by using a single plate-like member as the vibration plate and providing concave thin-walled portions  50  and  52  and the like, in which a portion in the thickness direction of the plate-like member is removed. 
     The case  4  is fixed onto the vibration plate  46  of the flow path forming substrate  40 , and a liquid storage section (not shown) such as an ink cartridge is connected thereto, whereby the ink supply path  45  which supplies ink to the manifold  44  is provided. 
     Also, at the case  4 , two housing portions  3  penetrating in the thickness direction are provided, and the actuator unit  2  is positioned and fixed to each housing portion  3 . 
     As shown in  FIG. 1 , the housing portion  3  of such a case  4  has a fixed plate holding portion  3   a  which is provided to have a width wider than that of the fixed plate  14  at a side in which the fixed plate  14  is fixed thereto, and a piezoelectric element holding portion  3   b  which is provided at the piezoelectric element forming member  13  side to have a width narrower than that of the fixed plate holding portion  3   a  and slightly wider than that of the piezoelectric element forming member  13 . In addition, the width as mentioned herein is a width in the juxtaposition direction of the piezoelectric elements  11  (the pressure generation chambers  42 ). Also, as shown in  FIG. 3 , at the fixed plate holding portion  3   a  of the housing portion  3 , a stepped portion  3   c  is provided such that a width on the vibration plate  46  side in a penetration direction becomes narrower, and the fixed plate  14  is fixed with an end surface thereof, in which the piezoelectric elements  11  protrude, come into contact with the stepped portion  3   c.    
     Also, at the case  4 , a compliance space  55  having a concave shape opening to a region facing the compliance portion  54  is provided. The compliance portion  54  is held to be deformable by the compliance space  55 . 
     Such a case  4  is formed by a resin material. Also, by molding the case  4 , the case can be manufactured at low cost and also easily mass-produced. 
     Further, in the case  4 , a reinforcing plate  60  is buried. In this embodiment, the reinforcing plate  60  is buried in a compartment wall  61  which is provided between two housing portions  3  of the case  4 , thereby dividing the housing portions  3 . 
     As shown in  FIG. 5 , the reinforcing plate  60  has a T shape in which a pair of corner portions of a plate-like member having a rectangular shape is cut away. Specifically, the reinforcing plate  60  is provided with concave portions  62  formed by cutting away corner portions on the flow path unit  5  side when it is buried in the case  4 , and by the concave portions  62 , convex portions  63  laterally protruding are provided at both side faces of the reinforcing plate  60  on the opposite side to the flow path unit  5 . 
     Such a reinforcing plate  60  is buried in the compartment wall  61  of the case  4  in a state where the reinforcing plate is partially exposed to both side faces in the juxtaposition direction of the piezoelectric elements  11  of the case  4  and a face on the opposite side to the flow path unit  5  of the case  4 . Specifically, two first exposed portions  64  having a concave shape are provided at the compartment wall  61  of a face on the opposite side to a joint surface of the case  4  to the flow path unit  5 , and a side on the opposite side to the flow path unit  5  of the reinforcing plate  60  is partially exposed by first exposed portions  64 . 
     Also, second exposed portions  65  having a concave shape which opens to a side face and a face on the flow path unit  5  side are respectively provided at both side faces in the juxtaposition direction of the piezoelectric elements  11  of the case  4 . The second exposed portions  65  are provided at the side faces of the case  4  to have a depth deeper than a depth up to the convex portion  63  of the reinforcing plate  60  and shallower than the concave portion  62 . Corner portions  66  on the concave portion  62  side of the convex portions  63  of the reinforcing plate  60  are exposed by the second exposed portions  65 . That is, in the reinforcing plate  60 , the face on the opposite side to the flow path unit  5  is exposed by the first exposed portions  64  and the face on the flow path unit  5  side and both side faces (both sides in the juxtaposition direction of the piezoelectric elements  11 ) are exposed by the second exposed portions  65 . 
     As for such a reinforcing plate  60 , a material having strength higher than that of the case  4 , for example, a metal material such as stainless steel, a resin material having strength higher than that of the case, glass ceramics, or the like can be used. 
     Also, the reinforcing plate  60  is integrated by a so-called insert molding in which filling is performed by placing it in a mold, which molds the case  4  by using a resin material, in advance and injection-molding a resin material into the mold. Then, the above-described first and second exposed portions  64  and  65  are formed by support of holding jigs which perform positioning in the mold when molding the case  4 . 
     In addition, at the reinforcing plate  60 , a plurality of flow holes  67  which penetrates in the thickness direction is provided. By the flow holes  67 , it is possible to improve fluidity of a resin material, which is filled in the mold, thereby reliably filling the mold with the resin material. 
     Here, a manufacturing method of the case will be described in more detail with reference to  FIGS. 6A and 6B . In addition,  FIGS. 6A and 6B  are cross-sectional views showing the manufacturing method of the case. 
     As shown in  FIG. 6A , the reinforcing plate  60  is positioned and held in a mold  100 . Holding of the reinforcing plate  60  in the mold  100  is performed by pressing four places of an outer circumference of the reinforcing plate  60  by holding jigs  110  and  111 . The holding jigs  110  come into contact with the face on the opposite side to the flow path unit  5  of the reinforcing plate  60 . Also, the holding jigs  111  come into contact with the corner portions  66  on the concave portion  62  side of the convex portions  63  of the reinforcing plate  60 . In addition, the holding jigs  111  coming into contact with the corner portions  66  indicates that the holding jigs  111  come into contact with the face on the flow path unit  5  side of the reinforcing plate  60  and both side faces in the juxtaposition direction of the piezoelectric elements  11  of the reinforcing plate  60 . In this manner, the holding jigs  111  press side faces on both sides in the juxtaposition direction of the piezoelectric elements  11  among the corner portions  66  of the convex portions  63  provided at both side faces in the juxtaposition direction of the piezoelectric elements  11 , with respect to one another, thereby positioning the reinforcing plate  60  in the mold  100  in a state where movement of the reinforcing plate in an X direction is restricted. By clamping both side faces in the juxtaposition direction of the piezoelectric elements  11  of the reinforcing plate  60  by two holding jigs  111 , positioning in the X direction of the reinforcing plate  60  in the mold  100  is performed. Also, by pressing the faces on the flow path unit  5  side of the corner portions  66  of the convex portions  63  with respect to one another by the holding jigs  111  and pressing the face on the opposite side to the flow path unit  5  of the reinforcing plate  60  by the holding jigs  110 , positioning of the reinforcing plate  60  in the mold  100  is performed in a state where movement in a Y direction of the reinforcing plate is restricted. As a result, the reinforcing plate  60  is positioned and held in a state where movement of the reinforcing plate in the X direction and the Y direction with respect to the mold is restricted. 
     In such a state, as shown in  FIG. 6B , by filling a melted resin material between the mold  100  and the reinforcing plate  60 , it is possible to form a case in which the reinforcing plate  60  is buried in the inside portion. At this time, two first exposed portions  64  and two second exposed portions  65 , which expose the reinforcing plate  60 , are formed by the holding jigs  110  and  111  positioning and holding the reinforcing plate  60 . 
     Further, as shown in  FIGS. 1 , and  3  to  5 , at the recording head  1 , the cover head  6  covering a discharge face side is provided at a face side, in which the nozzle orifices  47  open, in a state where the nozzle orifices  47  are exposed. 
     The cover head  6  includes an opening portion  70  exposing the nozzle orifices  47  and a frame portion  71  defining the opening portion  70 . 
     In this embodiment, the frame portion  71  is provided over the periphery of a discharge face, and a side wall portion  72  extended and provided so as to be bent over an outer circumferential edge portion of the discharge face is provided at the frame portion  71 . 
     Also, fixed portions  73  extended and provided at both sides in the juxtaposition direction of the nozzle orifices  47  are provided at the side wall portion  72 . The fixed portions  73  are provided being bent from the side wall portion  72  and are fixed to a flange portion  74 , which protrudes from a side face of the case  4 , through a fixing screw  75 . As a result, the cover head  6  is integrated with the recording head  1 . 
     The fixed portion  73  bent from such a side wall is provided in such a manner that a gap between it and the case  4  gradually increases toward the opposite side to the flow path unit  5 . Specifically, the side wall portion  72  is provided perpendicular to the flow path unit  5 , and a starting point of the fixed portion  73  with respect to the side wall portion  72  is located further on the flow path unit  5  side than the corner portion  66  of the reinforcing plate  60  exposed by the second exposed portion  65  of the case  4 . Then, the gap between the fixed portion  73  and the case  4  is provided so as to gradually increase from the starting point toward the flange portion  74  of the case  4 . 
     In this manner, by gradually increasing the gap between the fixed portion  73  and the case  4  toward the opposite side to the flow path unit  5  (the discharge face), even if ink penetrates between the cover head  6  and the flow path unit  5  or the case  4 , creeping of the penetrated ink to the opposite side to the flow path unit  5  of the case  4  due to capillarity can be suppressed. 
     In addition, as the cover head  6 , for example, a metal material such as stainless steel can be used. Also, the cover head  6  may be formed by press-working a metal plate or may be formed by molding. 
     In such a recording head  1 , when discharging an ink droplet, the ink droplet is discharged from a given nozzle orifice  47  by changing the volume of each pressure generation chamber  42  by deformation of the piezoelectric element  11  and the vibration plate  46 . Specifically, if ink is supplied from an ink cartridge (not shown) to the manifolds  44  through ink introduction holes  56  provided at the case  4 , the ink is distributed to each pressure generation chamber  42  through the ink supply path  45 . In fact, the piezoelectric element  11  contracts by applying voltage to the piezoelectric element  11 . Accordingly, the vibration plate  46  is deformed together with the piezoelectric element  11 , so that the volume of the pressure generation chamber  42  is expanded, whereby the ink is drawn into the pressure generation chamber  42 . Then, after the inner side up to the nozzle orifice  47  is filled with ink, the voltage applied to the electrodes  16  and  17  of the piezoelectric element  11  is released in accordance with a recording signal which is supplied through the circuit substrate  30 . Accordingly, the piezoelectric element  11  is extended, thereby returning to the original state, and the vibration plate  46  is also displaced, thereby returning to the original state. As a result, the volume of the pressure generation chamber  42  contracts, so that pressure in the pressure generation chamber  42  is increased, whereby an ink droplet is discharged from the nozzle orifice  47 . 
     Then, in this embodiment, by providing the reinforcing plate  60  in the case  4 , even if the case  4  expands in accordance with a temperature change or a humidity change of a resin portion of the case  4 , deformation of the entire case  4  is suppressed, so that pull-up of the actuator unit  2  fixed to the case  4  to the opposite side to the vibration  46  can be reduced. Also, at the time of driving of the juxtaposed piezoelectric elements  11 , since floating due to a difference in rigidity of the case  4  at the piezoelectric elements  11  on both end portion sides in the juxtaposition direction and the piezoelectric element  11  on the central portion side can be suppressed, an improvement and homogenization of ink discharge characteristics can be attained. 
     Also, in this embodiment, the concave portions  62  are provided at the discharge face side of the reinforcing plate  60 , and the corner portions  66  on the flow path unit  5  side of the convex portions  63  formed by the concave portions  62  are made so as to be exposed by the second exposed portions  65 . For this reason, as shown in  FIG. 7 , since the regions (the corner portions  66 ) exposed by the second exposed portions  65  of the reinforcing plate  60  are separated from the discharge face, ink L penetrated between the cover head  6 , the flow path unit  5 , and the case  4  does not reach the reinforcing plate  60  exposed by the second exposed portions  65  and creeping of ink at an interface between the reinforcing plate  60  and the resin material from the second exposed portions  65  can be suppressed. Incidentally, as shown in  FIG. 8 , in the case of a reinforcing plate  160  in which concave portions are not provided, if corner portions  166  on the discharge face side are exposed by the second exposed portions  65 , the discharge face and the corner portions  166  of the reinforcing plate  160  exposed by the second exposed portions  65  become close to each other. Then, if the discharge face and the reinforcing plate  160  exposed by the second exposed portions  65  are close to each other, the ink L penetrated between the cover head  6 , the flow path unit  5 , and the case  4  reaches the reinforcing plate  160  exposed by the second exposed portions  65 , and the ink then creeps an interface between the reinforcing plate  160  and the resin material due to capillarity, so that the ink penetrates into the housing portions  3  from the first exposed portions  64  side on the opposite side to the discharge face, thereby damaging the piezoelectric elements  11 . 
     Further, in this embodiment, as shown in  FIG. 7 , since the fixed portions  73  of the cover head  6  are made such that the gap between it and the case  4  gradually increases toward the opposite side to the discharge face, it is difficult for ink to penetrate into a clearance between the cover head  6  and the case  4 , and since creeping of the penetrated ink L to the opposite side to the discharge face can be suppressed, arrival of ink at the reinforcing plate  60  exposed by the second exposed portions  65  can be suppressed. Also due to this, penetration of ink into the housing portions  3  is suppressed, so that damage of the piezoelectric elements  11  by ink can be suppressed. On the contrary, as shown in  FIG. 8 , if fixed portions  173  of a cover head  106  are vertically provided, since the ink L penetrated between the case  4  and the cover head  106  creeps due to capillarity, also due to this, the ink reaches the reinforcing plate  160  exposed by the second exposed portions  65 . 
     Other Embodiments 
     One embodiment of the invention has been described above. However, a basic configuration of the invention is not limited to the aforesaid. 
     For example, in Embodiment 1 described above, the convex portions  63  are formed by providing the concave portions  62  at the flow path unit  5  side of the reinforcing plate  60 . However, cutout portions each having the same concave shape as the concave portion  62  may be further provided at the opposite side to the flow path unit  5  side of the reinforcing plate. Such an example is shown in  FIG. 9 . In addition,  FIG. 9  is a cross-sectional view of a recording head showing a modified example of the reinforcing plate. 
     As shown in  FIG. 9 , at a reinforcing plate  60 A, the concave portions  62  on the flow path unit  5  side and cutout portions  68  on the opposite side to on the flow path unit  5  are provided, and a convex portion  63 A is provided between each concave portion  62  and each cutout portion  68 . Even at such a reinforcing plate  60 A, the same effects as those of Embodiment 1 described above can be displayed. 
     Also, for example, in Embodiment 1 described above, the reinforcing plate  60  is buried in the compartment wall  61  of the case  4 . However, a buried position of the reinforcing plate  60  is not particularly limited and, for example, the reinforcing plate  60  may be buried in the peripheral wall side of the case  4 , to which the fixed plate  14  is fixed. 
     Also, in Embodiment 1 described above, as a pressure generation section which generates a pressure change in the flow path (the pressure generation chamber  42 ), a longitudinal vibration type piezoelectric element  11  which is constituted by alternately laminating the piezoelectric material layer  15 , the individual internal electrode  16 , and the common internal electrode  17  and extends and contracts in an axial direction is illustrated. However, the pressure generation section is not particularly limited thereto and a lateral vibration type piezoelectric element may be used which is constituted by alternately laminating the piezoelectric material layer  15 , the individual internal electrode  16 , and the common internal electrode  17  and in which one end portion in a lamination direction comes into contact with an island portion. 
     Also, as the pressure generation section, for example, a thin-film type piezoelectric element may be used in which a lower electrode, a piezoelectric body layer composed of a piezoelectric material, and an upper electrode are formed by film formation and a lithography method, and a thick-film type piezoelectric element can also be used which is formed by a method such as adhesion of a green sheet. Also, as the pressure generation section, a pressure generation section in which a heat generation element is disposed in a pressure generation chamber and a liquid droplet is discharged from a nozzle orifice by a bubble which is generated by heat generation of the heat generation element, a pressure generation section in which static electricity is generated between a vibration plate and an electrode and a liquid droplet is discharged from a nozzle orifice by deforming the vibration plate by an electrostatic force, or the like can also be used. 
     Also, the ink jet type recording head  1  of each of the embodiments constitutes a portion of an ink jet type recording head unit, which is provided with an ink flow path communicating with an ink cartridge and the like, thereby being mounted on an ink jet type recording apparatus.  FIG. 10  is a schematic view showing one example of the ink jet type recording apparatus. 
     In an ink jet type recording apparatus  200  shown in  FIG. 10 , cartridges  202 A and  202 B constituting an ink supply section are detachably mounted on an ink jet type recording head unit  202  (hereinafter simply also referred to as a head unit  202 ) having a plurality of ink jet type recording heads  1 , and a carriage  203  with the head unit  202  mounted thereon is mounted on a carriage shaft  205  attached to an apparatus main body  204  so as to be movable in an axial direction. The head unit  202  is set to discharge a black ink composition and a color ink composition, for example. 
     Then, a driving force of a driving motor  206  is transmitted to the carriage  203  through a plurality of gears (not shown) and a timing belt  207 , whereby the carriage  203  with the head unit  202  mounted thereon is moved along the carriage shaft  205 . On the other hand, at the apparatus main body  204 , a platen  208  is provided along the carriage shaft  205 , and a recording sheet S which is a recording medium such as paper fed by a paper feed roller (not shown) and the like is wound around the platen  208  and transported. 
     Also, in the ink jet type recording apparatus  200  described above, a configuration is illustrated in which the head unit  202  having a plurality of recording heads  1  is mounted on the carriage  203  and moved in a main scanning direction. However, it is not particularly limited thereto and the invention can also be applied to, for example, a so-called line type recording apparatus in which the recording head  1  is fixed and printing is performed only by moving the recoding sheet S such as paper in a sub-scanning direction. 
     Also, in the example described above, a configuration is made such that the head unit  202  having a plurality of recording heads  1  is mounted on the ink jet type recording apparatus  200 . However, one recording head  1  may be mounted on the head unit  202  and single or a plurality of recording heads  1  may be directly mounted on the ink jet type recording apparatus  200 . 
     In addition, in the embodiments described above, the ink jet type recording head is taken and described as one example of the liquid ejecting head. However, the invention broadly targets liquid ejecting heads in general and, of course, can also be applied to a liquid ejecting head which ejects liquid other than ink. As other liquid ejecting heads, for example, various recording heads which are used in an image recording apparatus such as a printer, a color material ejecting head which is used for the manufacturing of a color filter of a liquid crystal display or the like, an electrode material ejecting head which is used for the electrode formation of an organic EL display, an FED (field emission display), or the like, a biological organic matter ejecting head used for the manufacturing of a biochip, and the like can be given as examples.