Abstract:
Provided is an ink detecting module ( 100 ) that detects the discharge state of a liquid droplet by receiving a light beam emitted to a flying path of the liquid droplet discharged from a nozzle row ( 103 ) of an inkjet printer, the ink detecting module including: a light emitting unit ( 104 ) that emits a light beam; a light receiving unit ( 105 ) that receives the emitted light beam; and a module base ( 108 ) that integrally supports the light emitting unit ( 104 ) and the light receiving unit ( 105 ), the module base ( 108 ) including: positioning pins ( 106, 107 ) that are engaged with the inkjet printer and determine the fastening position in the inkjet printer; and a fastening unit that is fastened to the inkjet printer, in which, in the state of being fastened to the inkjet printer, only the positioning pins ( 106, 107 ) and the fastening unit are in contact with the inkjet printer.

Description:
RELATED APPLICATIONS 
       [0001]    This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2010/050047, filed on Jan. 6, 2010, which in turn claims the benefit of Japanese Application No. 2009-007822, filed on Jan. 16, 2009, the disclosures of which applications are incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a droplet detecting device and an inkjet printer. 
       BACKGROUND 
       [0003]    Conventionally, there is disclosed an inkjet-type recording apparatus that performs optical position adjustment between a light emitting module and a light receiving module with respect to a base member (for example, see Patent Literature 1). In this inkjet-type recording apparatus, the light emitting module and the light receiving module are fixed to a casing as the base member by adjusting the optical axes thereof. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Patent Publication No. 3509706 
       
     
       SUMMARY 
     Technical Problem 
       [0005]    However, in regard to the conventional inkjet-type recording apparatuses described as above, disclosed is a technique of fixing the light emitting module and the light receiving module to the casing as the base member by adjusting the optical axes thereof. However, there is no consideration of maintenance of the accuracy, the stability, and the like in the optical axis adjustment when the modules are mounted in the main body (printer) after the adjustment. Accordingly, there is a problem in that the accuracy changes in the state in which a droplet detecting device configured to be integrated with a module base by adjusting the optical axes thereof is fixed to the main body (printer), and the function of the optical axis adjustment is not stable. 
       Solution to Problem 
       [0006]    The present invention is contrived in view of the above, and the object thereof is to allow a droplet detecting device, configured to be integrated with a module base by adjusting the optical axes of a light emitting unit and a light receiving unit used as detection modules, to function stably without variations in accuracy in the state of being fixed to a main body (printer). 
         [0007]    According to an aspect of the present invention, provided is a droplet detecting device that detects a discharge state of a liquid droplet by receiving a light beam emitted to a flying path of the liquid droplet discharged from a nozzle of an inkjet printer, the droplet detecting device including: a light emitting unit that emits the light beam; a light receiving unit that receives the emitted light beam; and a detection unit that includes a base unit integrally supporting the light emitting unit and the light receiving unit, wherein the base unit includes: at least two positioning units that are engaged with the inkjet printer and determine the fastening position onto the inkjet printer; and a first fastening unit that is fastened to the inkjet printer, and wherein, in the state of being fastened to the inkjet printer, only the positioning units and the first fastening unit are in contact with the inkjet printer. 
         [0008]    According to another aspect of the present invention, the first fastening unit may be arranged at an approximate center of the detection unit, or at a position close to the light receiving unit from the center. 
         [0009]    According to still another aspect of the present invention, the base unit may further include a second fastening unit that is fastened to the inkjet printer through an elastic member. 
         [0010]    According to still another aspect of the present invention, the light receiving unit may receive scattering light that is generated when the light beam collides with the liquid droplet, and the detection unit may detect the discharge state of the liquid droplet based on light intensity of the scattering light. 
         [0011]    According to still another aspect of the present invention, provided is an inkjet printer in which the droplet detecting device described above may be built. 
       Advantageous Effects of Invention 
       [0012]    According to the present invention, obtainable is an advantage of allowing a droplet detecting device, configured so as to be integrated with a module base by adjusting the optical axes of a light emitting unit and a light receiving unit used as detection modules, to function stably without variations in accuracy in the state of being fixed to a main body (printer). 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a plan view illustrating the configuration of a droplet detecting device according to this embodiment. 
           [0014]      FIG. 2  is a side view illustrating the configuration of the droplet detecting device of  FIG. 1 . 
           [0015]      FIG. 3  is an explanatory diagram illustrating the configuration of a light emitting unit and a light receiving unit and illustrating an example in which a fastening member is disposed at one position on the light receiving unit side. 
           [0016]      FIG. 4  is an explanatory diagram illustrating the configuration of a light emitting unit and a light receiving unit and illustrating an example in which a fastening member is disposed at one position on the light emitting unit side. 
           [0017]      FIG. 5  is a plan view illustrating a fastening method in which an elastic member is arranged in the configuration of  FIG. 3 . 
           [0018]      FIG. 6  is a side view illustrating a fastening method in which an elastic member is arranged in the configuration of  FIG. 3 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]    Hereinafter, preferred embodiments of a droplet detecting device and an inkjet printer according to the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 
       [0020]      FIG. 1  is a plan view illustrating the configuration of a droplet detecting device according to this embodiment, and  FIG. 2  is a side view of  FIG. 1 . FIGS.  1  and  2  illustrate an example of the configuration of an inkjet printer in which an ink detecting module  100  is incorporated as a droplet detecting device. As shown in  FIGS. 1 and 2 , the inkjet printer includes a carriage  101 , a recording head  102 , a nozzle row  103 , an ink detecting module  100 , a mounting base  109 , and a fastening member  110  including a screw and the like. 
         [0021]    The ink detecting module  100  detects the discharge of liquid droplets by using a light emitting element and a light receiving element. The ink detecting module  100  includes a light emitting unit  104  having the light emitting element such as a laser diode, a light receiving unit  105  having the light receiving element such as a photodiode, and a module base  108  supporting the light emitting unit  104  and the light receiving unit  105 . In the module base  108 , positioning pins  106  and  107  are formed. The positioning pins  106  and  107  are pins that are used for determining the positions of the light emitting unit  104  side and the light receiving unit  105  side. A detection beam  111  is emitted from the light emitting unit  104  toward the light receiving unit  105 . 
         [0022]    The mounting base  109  is a base, on which the ink detecting module  100  is mounted, located on the inkjet printer main body side. The mounting base  109  includes a mounting face  109   a  having a convex face that gives a predetermined gap between the mounting base  109  and the ink detecting module  100  for screw fastening. 
         [0023]    As illustrated in  FIGS. 1 and 2 , the light emitting unit  104  and the light receiving unit  105  are integrated with the module base  108  by being adjusted of the optical axes with respect to the positioning pins  106  and  107 . Then, the module base  108  is arranged at a portion corresponding to the positioning pins  106  and  107  of the mounting base  109  and then is screw-fastened with a fastening member  110  to the mounting face  109   a  at one position. 
         [0024]    As above, by configuring the light emitting unit  104  and the light receiving unit  105  so as to be integrated with the module base  108 , the optical axis of the detection beam  111  is adjusted with respect to the positioning pins  106  and  107 . At this time, the light emitting unit  104  encases the light emitting element and a driving circuit thereof. The light receiving unit  105  encases the light receiving element and a detection circuit thereof. 
         [0025]    In addition, the module base  108  needs to have rigidity, taking deformation due to assembly or the like and the misalignment of the optical axis due to distortion into consideration. Particularly, regarding the mounting of the light emitting unit  104 , there is likelihood that distortion occurs when the light emitting unit is mounted on the module base  108 , distortion occurs when the optical axis is adjusted, distortion occurs when it is mounted on the main body, and the like. In order to avoid these problem, there may be considered a configuration of increasing the plate thickness of the module base  108  or a configuration using die casting or resin molding so as to improve the rigidity of the module base  108 . However, when taking the rigidity into consideration, the shape is enlarged. Accordingly, when a tradeoff with the cost is considered, a chassis structure acquired by bending a metal plate or the like is preferable. 
         [0026]    Next, a structure for minimizing the misalignment of the optical axis due to the mounting structure will be described. First, the mounting and the position determining structure of the ink detecting module  100  will be described. The detection beam  111  of a detection area that is located between the light emitting unit  104  and the light receiving unit  105  is positioned through adjustment of the optical axis, which is performed in advance, with respect to the positioning pins  106  and  107  of the module base  108 . In consideration of the misalignment of the optical axis attributable to the occurrence of distortion of the module base  108  that is caused by the bias of the weight balance of the ink detecting module  100 , the module base  108  is fastened to the mounting base  109  of the main body with the fastening member  110  that is disposed at an approximate center position of the ink detecting module  100 . As is obvious, it is preferable that the adjustment of the optical axis of the ink detecting module  100  is adjusted through a similar fixing structure. 
         [0027]    In addition, it is preferable to consider the area and the flatness of the mounting face  109   a  of the mounting base  109  of the main body for suppressing the occurrence of distortion at the time of the fastening to be minimal. In addition, units other than the fastening unit need to have a sufficient gap so as not to interfere with the ink detecting module  100 . In a case where other fastening units are arranged so as to protect the ink detecting module  100  from an unpredicted external force applied to the ink detecting module  100 , it is necessary to form a gap so as to prevent the interference by using a shoulder screw or the like. 
         [0028]    Through the fastening as above, the detection beam  111  and the nozzle row  103  are parallel to each other. In addition, the status of ink discharging can be checked by moving the carriage  101  so as to allow the nozzle row  103  and the detection beam  111  to match with each other and to allow ink from the nozzle row  103  to sequentially collide with the detection beam  111 . 
         [0029]    Next, the detection capability and the like based on the arrangement of the fastening member  110  in the above-described configuration will be described with reference to  FIGS. 3 and 4 .  FIG. 3  is an explanatory diagram illustrating the configuration of the light emitting unit  104  and the light receiving unit  105  and illustrating an example in which the fastening member  110  is disposed at one position on the light receiving unit  105  side. As illustrated in  FIG. 3 , the light emitting unit  104  includes an LD block  201 , a laser  202 , a light emitting point  203 , and a collimate lens  204 . The light receiving unit  105  includes a PD block  205 , a light receiving surface  206 , and a reflection surface  207 . 
         [0030]    As illustrated in  FIG. 3 , the detection beam  111 , which is diffused light whose light emitting point is the light emitting point  203  of the laser  202 , is formed as an approximately parallel beam through the collimate lens  204 . In this embodiment, in the state in which the detection beam  111  is detected, the adjustment of the optical axis and the focus detection are performed in such a manner that the beam waist of the detection beam  111  is positioned on the reflection surface  207  of the PD block  205 . Then, treatment of stray light is performed by guiding the beam reflected from the reflection surface  207  into the inside of the PD block  205 . Meanwhile, the light receiving surface  206  is light-shielded by the end surface of the reflection surface  207 , and through this configuration, the scattering light, generated when an ink droplet collides with the beam, can be detected. 
         [0031]    In such a configuration, for example, the output of scattering light from all the nozzle rows can be stably detected when the diameter of the beam on the reflection surface  207  is about 0.1 mm, and a distance between the center and the end surface is 0.4 mm. Accordingly, this state needs to be maintained also in the state of being built in the main body. However, the task of this is how to suppress the distortion occurring at the time of mounting, in a case where the above-described module base  108  has the metal-plate chassis structure described above, and the fastening position thereof becomes important. 
         [0032]    In  FIG. 3 , the fastening member  110  is disposed at one position on the light receiving unit  105  side. At this time, in a case where there is an abnormality such that a distortion θ occurs when mounting the module base to the mounting face  109   a , the light receiving surface  206  is influenced as inclination β. However, a distance Xa up to the fastening unit is short, and thus the amount of the position misalignment is such an extent as not to influence the detection capability. In addition, since the light emitting unit is separated therefrom by a distance Xb, the effect of the distortion on the light emitting unit  104  is not much. 
         [0033]      FIG. 4  is an explanatory diagram illustrating the configuration of the light emitting unit  104  and the light receiving unit  105  and illustrating an example in which the fastening member  110  is disposed at one position on the light emitting unit  104  side. In  FIG. 4 , in a case where there is an abnormality such that a distortion θ occurs when mounting the module base onto the mounting face  109   a , the inclination of the light emitting point  203  is β, and the detection beam  111  also inclines by the inclination β. In addition, at the leading end of the detection beam  111 , since the distance Xb is long, the amount α of beam inclination is created. In this example, the detection beam  111  enters up to the light receiving surface  206  due to the amount α of inclination of the beam, rendering the scattering light undetectable. 
         [0034]    An approximate calculation of the amount α of inclination of the beam is as below. The distortion of the fastening unit of 0.05 mm is increased up to 1 mm at the light receiving position based on “beam inclination amount α=distortion θ×distance Xb/fastening unit diameter (-=0.05×200/10=1)” when the distortion θ of 0.05 mm occurs with the diameter of the fastening unit=φ10 mm, and a distance from the light emitting point  203  to the light receiving surface  206  Xb=200 mm. 
         [0035]    Accordingly, it can be said that a fastening arrangement is more effective in an arrangement where the fastening position gets closer to the light receiving unit  105  side shown  FIG. 3  than in an arrangement where a fastening position is near the center as shown  FIG. 1 . Because the configuration does not likely to give the influence of the distortion to both side of the light emitting unit  104  and the light receiving unit  105  disposed on both sides. 
         [0036]    However, in the configuration of  FIG. 3 , a case is considered in which the detection range is long and there is a problem in the stability of the maintenance of the fastening due to the weight balance of the ink detecting module  100  or the like. A configuration example addressing such as case is illustrated in  FIGS. 5 and 6 . In the configuration as illustrated in  FIGS. 5 and 6 , by fastening the fastening member  110  through an elastic member  210  to the light emitting unit  104  side, the stability of the maintenance can be achieved while suppressing the distortion due to the fastening to be minimal. In addition, all the fastening units may be fastened through buffer members. 
         [0037]    As described above, the light emitting unit  104  and the light receiving unit  105  are integrated with the module base  108  and the optical axes thereof are adjusted with respect to the positioning pins  106  and  107 . Then, the module base  108  is disposed in portions of the mounting base  109  that correspond to the positioning pins  106  and  107  and thereafter is configured so as to be screw-fastened at one position on the mounting face  109   a  by the fastening member  110 . Accordingly, the distortion of the module base  108  at the time of fastening can be reduced to be minimal. In addition, since it is possible to suppress the occurrence of the deviation of the optical axes in the state where the optical axes are adjusted while the module base being mounted on the main body, it is possible to improve the assembly capability and the stability of the detection capability and to provide a low-cost base structure. 
         [0038]    In addition, by setting the above-described fastening position to a position near the center of the ink detecting module  100  or to a position near to the light receiving unit  105 , the influence of the distortion caused by the fastening of the light emitting unit  104  on the light emitting point  203  can be reduced; and the occurrence of the deviation of optical axes in the state where the optical axes have been adjusted in the detection state while the module base being mounted on the main body can be reduced, whereby it is possible to improve the assembly capability and the stability of the detection capability and to provide a low-cost base fastening configuration. 
         [0039]    In addition, by fastening through the elastic member  210  located at least at one position in a gap portion between the ink detecting module  100  and the mounting base  109  other than the fastening unit, the stability of the detection can be maintained even when the detection length is long, and accordingly, a long printing head can become also applicable. 
         [0040]    In addition, in a configuration where the optical axes of the light emitting device and the light receiving device are offset and where the scattering light is detected thereby, the deviation of the optical axes gives high influence over the detection capability. In the case of such a detection configuration, especially, by employing a technique of this embodiment that is capable of reducing the distortion of the module base  108  at the time of fastening to be minimal, it is possible to improve the assembly capability and the stability of the detection capability, and to provide a low-cost base structure. In addition, by mounting the droplet detecting device (for example, the configuration of  FIG. 1  or  5 ) represented by this embodiment into an inkjet printer, it is possible to provide a low-cost inkjet printer having stable printing capability. 
       INDUSTRIAL APPLICABILITY 
       [0041]    As described above, a droplet detecting device and an inkjet printer according to the present invention are useful for a droplet detecting device and an inkjet printer that detect the discharge of liquid droplets from a nozzle and, particularly, are suitable for a device or a system in which a light emitting device and a light receiving device are integrally mounted on a main body through adjustment of the optical axes thereof. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               100  INK DETECTING MODULE 
               101  CARRIAGE 
               102  RECORDING HEAD 
               103  NOZZLE ROW 
               104  LIGHT EMITTING UNIT 
               105  LIGHT RECEIVING UNIT 
               106 ,  107  POSITIONING PINS 
               108  MODULE BASE 
               109  MOUNTING BASE 
               109   a  MOUNTING FACE 
               110  FASTENING MEMBER 
               111  DETECTION BEAM 
               210  ELASTIC MEMBER