Patent Publication Number: US-6702432-B2

Title: Configuration of inkjet head realizing uniform ink ejection performance

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inkjet head for an office and industrial use. 
     2. Related Art 
     FIG. 1 is a cross-sectional view of a conventional inkjet head  200 . As shown in FIG. 1, the inkjet head  200  includes an orifice plate  2 , a chamber plate  4 , a restrictor plate  6 , a diaphragm plate  9 , a support plate  17 , and a housing  11 , which are all fixed one on the other in this order by adhesive. The inkjet head  200  further includes a plurality of laminated-type piezoelectric elements  12  and a fixing plate  13  for supporting the piezoelectric elements  12 . 
     As shown in FIGS. 1 to  3 , the orifice plate  2  is formed with a plurality of nozzles  1  through which ink droplets are ejected. The chamber plate  4  is formed with a plurality of pressure chambers  3  in fluid communication with the corresponding nozzles  1 . The restrictor plate  6  is formed with a plurality of restrictors  5  that regulate ink flow toward the pressure chambers  3 . The diaphragm plate  9  is integrally formed with a filter  8 . The support plate  17  is formed with a plurality of through holes  10 A and  10 B larger than a cross-sectional dimension of the piezoelectric element  12 . 
     The housing  11  is formed with a common ink chamber  16  and an opening  18 . The common ink chamber  16  is in fluid communication with all the restrictors  5  via the through holes  10 B and the filter  8 . The opening  18  is greater than a cross-sectional dimension of the fixing plate  13 . A pair of positioning holes  14  are formed through all the orifice plate  2 , the chamber plate  4 , the restrictor plate  6 , the diaphragm plate  9 , the support plate  17 , and the housing  11  for positioning these members when manufacturing the inkjet head  200 . Adhesive agent or the like (not shown) is filled in the positioning holes  14  to fix the members. 
     As shown in FIG. 2, portions of the diaphragm plate  9  corresponding to the through holes  10 A formed in the support plate  17  serve as diaphragms  7 . Each piezoelectric element  12  is attached to the corresponding diaphragm  7  through the through hole  10 A such that the piezoelectric element  12  confronts the pressure chamber  3  via the diaphragm  7 . 
     In this configuration, ink inside the common ink chamber  16  is distributed to the restrictors  5  and supplied into the pressure chambers  3 . Upon application of a driving voltage, the piezoelectric element  12  causes displacement in the diaphragm  7 , which in turn decreases the volume of the corresponding pressure chamber  3  with a resultant increase in the internal pressure thereof. This internal pressure ejects ink inside the pressure chamber  3  as an ink droplet through the nozzle  1 . 
     SUMMARY OF THE INVENTION 
     However, in the above configuration, when the inkjet head  200  is produced by adhering all the plates  2 ,  4 ,  6 ,  9 ,  17  at the same time, and adhered portion  9   e  of the diaphragm plate  9  (FIG. 4) is not securely adhered to the support plate  17  for the reason that a uniform pressing force is not applied to the adhered portion  9   e  in a direction indicated by an arrow in FIG. 4 due to the restrictor  5  located adjacent to the adhered portion  9   e . Accordingly, there is a danger that the diaphragm plate  9  is adhered to, for example, only a region between points P 2  and P 3  of the support plate  17 , although the diaphragm plate  9  must be adhered to a region between points P 1  and P 3 . This changes a fixed end of the diaphragm from the original point P 1  to the point P 2 , changing the dimension of the diaphragm  7 . Unevenness in the position of the fixed ends of the diaphragms  7  varies the deforming amount of the diaphragms  7 , and changes ink ejection performance of the nozzles  1 , whereby overall ink ejection performance of the inkjet head  200  is degraded. 
     Further, if adhesion between the adhered portion  9   e  and the support plate  17  is insecure, when the piezoelectric element  12  deforms the diaphragm  7  in response to a driving voltage, the adhered portion  9   e  will be easily peeled off the support plate  17 , further shifting the fixed end of the diaphragm  7  over a long time use. 
     It is an object of the present invention to overcome the above problems, and to provide an inkjet head realizing a uniform ink ejection performance. 
     In order to overcome the above and other object, there is provided an inkjet head including a diaphragm plate having a first surface and a second surface, a piezoelectric element attached to the first surface of the diaphragm plate for selectively deforming the diaphragm plate, a support plate attached to the second surface of the diaphragm plate and formed a first through hole and a second through hole, and a channel plate attached to the support plate in a manner that the support plate is interposed between the channel plate and the diaphragm plate, the channel plate being formed with a channel fluidly connecting the first through hole and the second through hole. 
     There is also provided an inkjet head including a pair of support plates formed with a through hole, a diaphragm plate interposed between and attached to the pair of support plates, and a piezoelectric element attached to the diaphragm through the through hole formed in one of the support plates. The support plates are substantially identical. 
     Further, there is provided an inkjet head including a support plate, a diaphragm plate, and a piezoelectric element. The support plate is formed with a through hole. The diaphragm plate is attached to the support plate. A portion of the diaphragm plate corresponding to the through hole serves as a diaphragm. The diaphragm has a first surface confronting the through hole and a second surface opposite to the first surface. The piezoelectric element is attached to the second surface of the diaphragm for selectively deforming the diaphragm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a cross-sectional view of a conventional inkjet head; 
     FIG. 2 is cross-sectional view of the conventional inkjet head taken along a line II—II of FIG. 1; 
     FIG. 3 is a plan view showing plates of the conventional inkjet head; 
     FIG. 4 is a cross-sectional view of the conventional inkjet head where a fixed end of a diaphragm is shifted from an original position; 
     FIG. 5 is a cross-sectional view of an inkjet head according to a first embodiment of the present invention; 
     FIG. 6 is a cross-sectional view of the inkjet head taken along a line VI—VI of FIG. 5; 
     FIG. 7 is an explanatory phantom view showing positional relationship among components of the inkjet head; 
     FIG. 8 is a plan view showing plates of the inkjet head of FIG. 5; 
     FIG. 9 is a cross-sectional view of an inkjet head according to a second embodiment of the present invention; 
     FIG. 10 is a cross-sectional view of the inkjet head taken along a line X—X of FIG. 9; and 
     FIG. 11 is a plan view showing plates of the inkjet head of FIG.  9 . 
    
    
     PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
     Next, inkjet heads according to preferred embodiments of the present invention will be described while referring to the attached drawings. 
     First, an inkjet head  100  according to a first embodiment of the present invention will be described. Components same as those of the above-described conventional inkjet head  200  will be assigned with the same numberings and description thereof will be omitted in order to avoid duplication in explanation. 
     As shown in FIGS. 5 and 6, the inkjet head  100  has the similar configuration as that of the conventional inkjet head  200  shown in FIGS. 1 and 2, except that a diaphragm plate  9  of the present embodiment is interposed between a pair of support plates  17 A,  17 B. The support plates  17 A,  17 B both have the same configuration as the support plate  17  of the conventional inkjet head  200  and are, as shown in FIG. 8, formed with a plurality of through holes  10 A,  10 B and a pair of positioning holes  14 . 
     Here, as shown in FIG. 7, the nozzle  1 , the pressure chamber  5 , and the piezoelectric element  12 , i.e., the diaphragm  7 , are all in alignment in a direction in which the plates  2 ,  4 ,  6 ,  17 A,  9 ,  17 B are laminated. 
     In the above configuration, because the adhered portion  9   e  of the diaphragm plate  9  is sandwiched between the support plates  17 A and  17 B, the rigidity of the diaphragm plate  9 , i.e., the adhered portion  9   e  increases with a resultant improvement in adhesion between the adhered portion  9   e  and the support plate  17 B. Also, even if the adhesion between the adhered portion  9   e  and the support plate  17 B is insecure, the support plate  17 A prevents the adhered portion  9   e  from peeling off the support plate  17 B. Accordingly, the fixed end of the diaphragm  7  is maintained at the original position P 1 . 
     Moreover, even when the piezoelectric element  12  deforms the diaphragm  7  toward the pressure chamber  3 , that is, in a direction toward the support plate  17 A and away from the support plate  17 B, in response to a driving voltage for ejecting an ink droplet, the support plate  17 A prevents the adhered portion  9   e  from peeling off the support plate  17 B, and an edge of the support plate  17 A defining the through hole  10 A positions the fixed end in place at the original position P 1 . Accordingly, the deforming amount of the diaphragm  7  is maintained the same, realizing a uniform ink ejection performance over a long time use. 
     The inkjet head  100  having the above configuration is formed in the following manner. That is, first, the diaphragm plate  9  is positioned between and fixedly adhered to the support plates  17 A and  17 B. The relative position of the diaphragm plate  9  with respect to the support plates  17 A and  17 B is determined using the positioning holes  14 . Then, the rest of the plates  2 ,  4 ,  6  and the housing  11  are fixedly adhered to one on the other and also to the support plates  17 A and  17 B. By fixing the diaphragm plate  9  to the support plates  17 A and  17 B first, the fixing operation is facilitated, and the diaphragm plate  9  is securely fixed to the support plates  17 A and  17 B regardless of the existence of the restrictors  5 , which contrasts to the conventional inkjet head  200  where the plate members are all adhered one another at once. 
     It is preferable that the support plates  17 A,  17 B be formed by etching or the like in the same production lot so as to minimize variations in dimension of the support plates  17 A,  17 B. This further suppresses the variations in position of the fixed ends of the diaphragms  7 . It is preferable that the support plates  17 A and  17 B have exactly the same size and the same shape in order to suppress the fluctuation in ink ejection performance. However, the exact-same size and shape are not required. 
     As described above, according to the present embodiment, the adhered portion  9   e  is prevented from peeling off the support plate  17 B, and the fixed end of the diaphragm  7  is maintained at the original position. Accordingly, fluctuation in ink ejection performance is prevented, so that the inkjet head  100  capable of stable ink ejection can be provided. 
     Next, an inkjet head  100 A according to a second embodiment of the present invention will be described while referring to FIGS. 9,  10 , and  11 . Components that are the same as those of the first embodiment are assigned with the same numberings and their explanation will be omitted in order to above duplication in explanation. 
     As shown in FIG. 9, the inkjet head  100 A has the similar configuration as the inkjet head  100  of the first embodiment, except that the support plate  17 B is dispensed with in the second embodiment. This configuration also provides the same effect obtained in the configuration of the first embodiment. 
     That is, as shown in FIG. 10, the adhered portion  9   e  of the diaphragm plate  9  is interposed between and adhered to the support plate  17 A and the housing  11 . In this configuration, even when the adhesion between the adhered portion  9   e  and the housing  11  is insecure, and even when the piezoelectric element  12  deforms the diaphragm  7  toward the pressure chamber  3 , the support plate  17 A prevents the adhered portion  9   e  from peeling off the housing  11 , thereby maintaining the fixed end of the diaphragm  7  at the original position P 1 . Therefore, a uniform ink ejection performance is maintained. 
     In this embodiment also, the diaphragm plate  9  and the support plate  17 A are first fixed to each other, and then the rest of the plates and the housing are fixed. In this manner, the diaphragm plate  9  and the support plate  17 A are securely fixed in a stable manner, minimizing the variations in position of the fixed end of the diaphragms  7 . Hence, the inkjet head  100 A capable of uniform ink ejection without undesirable variation can be provided. 
     While some exemplary embodiments of this invention have been described in detail, those skilled in the art will recognize that there are many possible modifications and variations which may be made in these exemplary embodiments while yet retaining many of the novel features and advantages of the invention.