Abstract:
A drive mechanism of an injection molding machine includes a position adjustment part capable of adjusting a relative position between a rear plate and a motor fixing member. The position adjustment part includes a plurality of screw holes formed in the motor fixing member, a plurality of bolts threadedly engaged with these screw holes, and an abutting part that abuts on these bolts. These bolts are rotated to abut on the abutting part, so that the relative position between the rear plate and the motor fixing member can be adjusted.

Description:
RELATED APPLICATIONS 
     The present application claims priority to Japanese Application Number 2014-204786, filed Oct. 3, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a drive mechanism of an injection molding machine, and more particularly to a drive mechanism of an injection molding machine having an adjustment function of the shaft centers of a ball screw shaft and a motor shaft. 
     Description of the Related Art 
     An example of a configuration of a conventional injection molding machine will be described with reference to  FIG. 4  and  FIG. 5 . 
     A movable plate  1  is supported by a guide member  2  to be movable in an axial direction. A ball screw nut  3  is fixed to this movable plate  1  in a manner such that it does not rotate, and a ball screw shaft  4  is engaged with the ball screw nut  3 . This ball screw shaft  4  is supported by a rear plate  5  through a bearing  21 , and is rotatable, but is unmovable in the axial direction. The ball screw shaft  4  thus configured is rotated, so that the ball screw nut  3  moves in the axial direction. Consequently, the movable plate  1  to which the ball screw nut  3  is fixed also moves. 
     The ball screw shaft  4  is rotationally driven by a ball screw driving motor  8 . The ball screw driving motor  8  is fixed to the rear plate  5 . A shaft of the driving motor  8  and the ball screw shaft  4  are coupled by a coupling member  6 , so that torque of the driving motor  8  can be transmitted to the ball screw shaft  4 . 
     In a ball screw drive mechanism of an injection molding machine, in a case where a ball screw shaft and a shaft of a ball screw driving motor are coupled with each other through a coupling member, the shaft center of ball screw shaft is preferably made to coincide with the shaft center of the motor shaft. In order to achieve this, it is necessary to improve the accuracy of the machining of each of a motor fixing part and a ball screw shaft fixing part. However, even when each machining accuracy is improved, it is necessary to provide a slight clearance in order to mount each member, and such a clearance could lead to deviation of the shaft centers. 
     As a conventional technology for solving such a problem, Japanese Patent Application Laid-Open No. 11-138599 discloses an in-line screw type electric injection molding machine in which a pair of injection motors are mounted on a rear surface of a pressure plate by using a bracket, respectively, and the output shafts of these motors are coupled to rear ends of ball screw shafts. Additionally, Japanese Patent Application Laid-Open No. 2013-984 discloses an injection apparatus in which the driving shaft center is aligned with the screw shaft center. 
     However, the above Japanese Patent Application Laid-Open No. 11-138599 discloses that the driving motor is fixed to the rear plate by means of the bracket, but does not disclose how to fix the bracket or does not disclose an adjustment mechanism for making the shaft center of the ball screw shaft coincide with the shaft center of the motor shaft. 
     Japanese Patent Application Laid-Open No. 2013-984, mentioned above, describes an adjustment mechanism for aligning the screw shaft center with the driving shaft center, wherein an adjustment protrusion is movable in an adjustment recess, but does not describe how to move the adjustment protrusion or how to adjust a slight deviation of the shaft centers. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a drive mechanism of an injection molding machine in which the shaft center of a ball screw shaft and the shaft center of a motor shaft can be suitably aligned with each other with a simple configuration. 
     A drive mechanism of an injection molding machine according to the present invention includes: a movable plate capable of advancing and retreating along a guide member; a rear plate provided in such a manner that it faces the movable plate; a ball screw including a ball screw nut and a ball screw shaft; a driving motor for driving the ball screw shaft through a coupling member; and a motor fixing member to which the driving motor is fixed. The ball screw nut is fixed to the movable plate, the ball screw shaft is rotatably supported by the rear plate so as not to be movable in an axial direction, and the motor fixing member is disposed such that a relative position thereof with respect to the rear plate is adjustable. This drive mechanism of an injection molding machine further includes a position adjustment part capable of adjusting the relative position between the rear plate and the motor fixing member. The position adjustment part includes: at least one screw hole that penetrates the motor fixing member or an extension member extending from the motor fixing member, and has a thread; a bolt of which thread is engaged with the thread of the screw hole; and an abutting part that abuts on the bolt. 
     The abutting part may be provided in the rear plate, or the abutting part may be provided in a motor-fixing-member supporting member that supports the motor fixing member. 
     The screw holes may be provided at two or more places in the motor fixing member or the extension member such that directions of center axes are different from each other. 
     According to the present invention, it is possible to provide a drive mechanism of an injection molding machine in which the shaft center of the ball screw shaft and the shaft center of the motor shaft can be suitably aligned with each other with a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will be apparent from the following description of embodiments with reference to the accompanying drawings, in which: 
         FIG. 1  is a plan view of a first embodiment of a drive mechanism of an injection molding machine according to the present invention; 
         FIG. 2  is a front view of the drive mechanism of the injection molding machine in  FIG. 1 ; 
         FIG. 3  is a front view of a second embodiment of a drive mechanism of an injection molding machine according to the present invention; 
         FIG. 4  is a plan view of a drive mechanism of a conventional injection molding machine; and 
         FIG. 5  is a front view of the drive mechanism of the injection molding machine in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First, a first embodiment of a drive mechanism of an injection molding machine according to the present invention will be described with reference to  FIG. 1  and  FIG. 2 . Components similar to the components of the conventional technologies illustrated in  FIG. 4  and  FIG. 5  are denoted by the same reference numerals, and descriptions thereof are omitted. 
     In a motor fixing member  7  that fixes a ball screw driving motor  8  for rotationally driving a ball screw shaft  4 , first, second and third screw holes  9   a ,  9   b  and  9   c  are provided so as to penetrate the motor fixing member  7 . These screw holes  9   a ,  9   b  and  9   c  are formed with respective female screws. The shaft centers of first and second bolts  10   a  and  10   b  engaged with the first and second screw holes  9   a  and  9   b  are directed to a horizontal direction, and face each other, as illustrated in the plan view of  FIG. 1 . On the other hand, as illustrated in the front view of  FIG. 2 , the shaft center of a third bolt  10   c  engaged with third screw hole  9   c  is directed in a vertical direction. 
     A distal end of a first bolt  10   a  engaged with the first screw hole  9   a  abuts on (an abutting part  15   a  of) an outer wall surface of a rear plate  5 . Additionally, while a distal end of a second bolt  10   b  engaged with the second screw hole  9   b  faces the outer wall surface of the rear plate  5 , the second bolt  10   b  is installed such that the distal end is in a non-contact state with the rear plate  5 . Consequently, the motor fixing member  7  is movable in the horizontal direction in a section until contact with second bolt  10   b , by pressing by the first bolt  10   a.    
     In  FIG. 1 , the distal end of the first bolt  10   a  directly abuts on (an abutting part  15   a  of) an outer wall surface of the rear plate  5 . However, an abutting member (not illustrated) may be separately provided at a part of the rear plate  5  which is in contact with the first bolt  10   a , as the abutting part  15   a , and the distal end of the first bolt  10   a  may abut on the abutting member. 
     On the other hand, (an abutting part  15   c  of) a motor-fixing-member supporting member  14  for supporting the motor fixing member  7  abuts on the third bolt  10   c  engaged with the third screw hole  9   c , as illustrated in  FIG. 2 . This motor-fixing-member supporting member  14  is a separate member from the rear plate  5 . This pressing force of third bolt  10   c  makes the motor fixing member  7  movable in the vertical direction. 
     In  FIG. 2 , the distal end of the third bolt  10   c  directly abuts on (an abutting part  15   c  of) an outer wall surface of the motor-fixing-member supporting member  14 . However, an abutting member (not illustrated) may be separately provided at a part of the motor-fixing-member supporting member  14  which is in contact with the third bolt  10   c , as the abutting part  15   c , and the distal end of the third bolt  10   c  may abut on the abutting member. 
     Now, a second embodiment of the drive mechanism of the injection molding machine according to the present invention will be described with reference to  FIG. 3 . 
     In the afore-mentioned first embodiment, the third screw hole  9   c  is provided in the motor fixing member  7 , and the distal end of the third bolt  10   c  engaged with the third screw hole  9   c  abuts on the motor-fixing-member supporting member  14 . In this second embodiment, instead, an extension member  16  integrated with a motor fixing member  7  is provided in the motor fixing member  7 , a fourth screw hole  9   d  is provided in the extension member  16 , and a distal end of a fourth bolt  10   d  engaged with the fourth screw hole  9   d  abuts on (an abutting part  15   d  of) an outer wall surface of a rear plate  5 , in place of the above. 
     Striking the distal end of the fourth bolt  10   d  engaged with the fourth screw hole  9   d  against (an abutting part  15   d  of) an outer wall surface of the rear plate  5 , the motor fixing member  7  moves in a vertical direction. In  FIG. 3 , the distal end of the fourth bolt  10   d  directly strikes against (the abutting part  15   d  of) the outer wall surface of the rear plate  5 . However, an abutting member (not illustrated) may be separately provided at a part of the rear plate  5  which is in contact with the fourth bolt  10   d , as the abutting part  15   d , and the abutting member may strikes against the distal end of the fourth bolt  10   d.    
     In  FIG. 2 , the extension member  16  is a member that extends from the motor fixing member  7  and is integrated with the motor fixing member  7 . However, the extension member  16  may not be necessarily integrated with the motor fixing member  7 , and the extension member  16  may be configured by fixing a separate member to the motor fixing member  7  with bolts or the like. Additionally, the shape of the extension member  16  in this embodiment is merely an example, and can be a shape other than a shape illustrated in  FIG. 3 . 
     Furthermore, in the example illustrated in  FIG. 3 , the extension member  16  provided in the motor fixing member  7  is a single member. But, it is possible that two or more extension members are provided, respective screw holes are formed in the extension members, respective bolts are engaged with the screw holes, and the ends of the bolts are caused to abut on respective abutting parts of the outer wall surface of the rear plate  5 , thereby enabling positional adjustment in a direction different from a vertical direction (e.g., horizontal direction).