Patent Publication Number: US-11045920-B2

Title: Machining apparatus

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2017-038488 filed on Mar. 1, 2017 including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus configured to machine a workpiece with a grinding wheel. 
     2. Description of the Related Art 
     In the process of manufacturing, for example, a tapered roller to be used as a rolling element of a tapered roller bearing, the tapered roller is shaped by grinding, and then its end face (end face having a larger diameter) is finished. For example, Japanese Patent Application Publication No. 2003-300133 (JP 2003-300133 A) discloses an apparatus configured to perform the machining described above. In this machining apparatus, a rotating grinding wheel is brought into contact with the end face of the tapered roller supported by rolls. 
       FIG. 6  is a perspective view illustrating a part of a related-art machining apparatus configured to finish an end face  98  of a tapered roller  99 . The machining apparatus includes a support mechanism (not illustrated; for example, the rolls) and a wheel unit  90 . The support mechanism supports the tapered roller  99 . A grinding wheel  91  is mounted on the wheel unit  90 . The grinding wheel  91  rotates about a center line Ca in a horizontal direction by a motor  92 . The Wheel unit  90  is provided on a base  94  of the machining apparatus, and is swivelable (see  FIG. 7 ) about a center line C 0  in a vertical direction, which is located at a central part of the wheel unit  90 . The center line C 0  in the vertical direction is hereinafter referred to as a swivel center line C 0 . 
     In the apparatus configured to finish the end face  98  of the tapered roller  99 , the tapered roller  99  is supported while being positioned. Therefore, the tapered roller  99  (end face  98 ) is set as a reference of machining. Thus, the position of the wheel unit  90  (grinding wheel  91 ) needs to be adjusted to the tapered roller  99 . As illustrated in  FIG. 6 , the wheel unit  90  includes an upper unit  96  and a lower unit  97  for positional adjustment in a fore-and-aft direction. The grinding wheel  91  and the motor  92  are mounted on the upper unit  96 , and a dovetail groove  96   a  whose groove direction is the fore-and-aft direction is formed in the upper unit  96 . The lower unit  97  has a protruding bar  97   a  fitted to the dovetail groove  96   a . The wheel unit  90  includes a mechanism configured to move the upper unit  96  in the fore-and-aft direction relative to the lower unit  9 ′ through rotation of a handle  95 , and to position the upper unit  96  with a jig or the like (not illustrated) (this mechanism is hereinafter referred to as a fore-and-aft adjustment mechanism). Further, the machining apparatus includes a ball guide shaft (not illustrated) that is long in a lateral direction for positional adjustment of the grinding wheel  91  in the lateral direction. The wheel unit  90  is moved along the ball guide shaft by an air cylinder (not illustrated). Thus, the machining apparatus includes a mechanism configured to move the wheel unit  90  (grinding wheel  91 ) in the lateral direction relative to the base  94 , and to position the wheel unit  90  (grinding wheel  91 ) with a jig or the like (not illustrated) (hereinafter referred to as a lateral adjustment mechanism). 
     The end face  98  of the tapered roller  99  is finished into a shape conforming to a spherical surface having a predetermined curvature radius. When the curvature radius of the end face  98  is changed due to, for example, a change of the part number of the tapered roller  99 , the wheel unit  90  is swiveled about the swivel center line C 0  to change the direction of the grinding wheel  91  with respect to the tapered roller  99  (see  FIG. 7 ).  FIG. 8  is a plan view for describing the grinding wheel  91  and the tapered roller  99 . In  FIG. 8 , the grinding wheel  91  indicated by a long dashed double-short dashed line is in a reference state in which the center line Ca of the grinding wheel  91  coincides with the lateral direction. The grinding wheel  91  indicated by a continuous line is in a state in which the wheel unit  90  in the reference state is swiveled about the swivel center line C 0  by an angle A. 
     When the curvature radius of the end face  98  of the tapered roller  99  is changed as described above, the direction (angle) of the grinding wheel  91  needs to be adjusted in accordance with the change of the curvature radius. For example, as illustrated in  FIG. 8 , the wheel unit  90  is swiveled about the swivel center line C 0  by the angle A. Then, a machining point P 0  on the end face  98  of the tapered roller  99  that is the reference of machining and the grinding wheel  91  (indicated by the continuous line) are misaligned in the lateral direction and in the fore-and-aft direction because the swivel center line C 0  is located at the central part of the wheel unit  90 . In order to align the grinding wheel  91  with the machining point P 0 , the related-art machining apparatus needs to adjust the position of the wheel unit  90  by moving the wheel unit  90  in the lateral direction with the lateral adjustment mechanism, and also to adjust the position of the wheel unit  90  by moving the wheel unit  90  in the fore-and-aft direction with the fore-and-aft adjustment mechanism. 
     As described above, in the related-art machining apparatus, the swivel center line C 0  of the wheel unit  90  is located at the central part of the wheel unit  90 . Therefore, when the direction of the grinding wheel  91  is changed, the position of the wheel unit  90  (grinding wheel  91 ) needs to be adjusted again both in the fore-and-aft direction and in the lateral direction. For this reason, the machining is stopped, and therefore the production efficiency decreases. Both of the fore-and-aft adjustment mechanism and the lateral adjustment mechanism are necessary for this positional adjustment. This makes the machining apparatus complicated. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention to provide a machining apparatus in which a decrease in production efficiency can be suppressed and the structure is simplified. 
     A machining apparatus according to one aspect of the present invention is configured to machine a machining target face of a workpiece with a grinding wheel. The machining apparatus has the following features in its structure. That is, the machining apparatus includes a support mechanism, a wheel unit, and a base. The support mechanism is configured to support the workpiece. The grinding wheel is mounted on the wheel unit. The base is configured to support the wheel unit so that the wheel unit is swivelable about a center line in a vertical direction. A machining point where the grinding wheel is brought into contact with the machining target face of the workpiece supported by the support mechanism is located on an extension of the center line serving as a swivel center of the wheel unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: 
         FIG. 1  is a perspective view illustrating a part of a machining apparatus according to one embodiment of the present invention; 
         FIG. 2  is an explanatory view of a support mechanism; 
         FIG. 3  is a perspective view illustrating a part of the machining apparatus; 
         FIG. 4  is a plan view illustrating a part of the machining apparatus illustrated in  FIG. 1 ; 
         FIG. 5  is a plan view illustrating a part of the machining apparatus illustrated in FIG. 
         FIG. 6  is a perspective view illustrating a part of a related-art machining apparatus; 
         FIG. 7  is a perspective view illustrating a part of the related-art machining apparatus; and 
         FIG. 8  is a plan view for describing a grinding wheel and a tapered roller in the related-art machining apparatus. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a perspective view illustrating a part of a machining apparatus according to one embodiment of the present invention. A machining apparatus  5  of this embodiment is an apparatus configured to machine a machining target face of a workpiece with a grinding wheel  31 . The workpiece of this embodiment is a tapered roller  7  to be used as a rolling element of a tapered roller bearing. The machining target face is an end face  8  of the tapered roller  7 . The end face  8  is an end face having a larger diameter, and is a face to be brought into contact with a cone back face rib (large rib) of an inner ring of the tapered roller bearing. The machining apparatus  5  illustrated in  FIG. 1  functions as a lapping apparatus, which performs lapping as finishing for the end face  8 . 
     The machining apparatus  5  includes a support mechanism  10  (see  FIG. 2 ), a wheel unit  30 , and a base  20 . The support mechanism  10  supports the tapered roller  7 . The grinding wheel  31  is mounted on the wheel unit  30 .  FIG. 2  is an explanatory view of the support mechanism  10 . The support mechanism  10  of this embodiment includes two rolls (regulating wheels)  11  and  12  and a support member  13 . The pair of rolls  11  and  12  sandwich the tapered roller  7  from above and below, and the support member  13  is brought into sliding contact with the tapered roller  7 . The rolls  11  and  12  are in contact with an outer peripheral surface  9  of the tapered roller  7 . When the rolls  11  and  12  rotate, the tapered roller  7  rotates about a center line Cb of the tapered roller  7 . In the support mechanism  10 , the tapered roller  7  is positioned in a radial direction and also in an axial direction with respect to the center line Cb. Since the tapered roller  7  is supported while being positioned, the tapered roller  7  (end face  8 ) is a reference of machining. 
     In the machining apparatus  5  (see  FIG. 1 ), a direction of the center line Cb of the tapered roller  7  supported by the support mechanism  10  is defined as a lateral direction. The direction of the center line Cb (lateral direction) of this embodiment is a horizontal direction. A horizontal direction orthogonal to the lateral direction is defined as a fore-and-aft direction. The support mechanism  10  may have a structure other than the illustrated structure. The support mechanism  10  is mounted on an apparatus body (not illustrated) fixed to a work area. 
     The wheel unit  30  includes the grinding wheel  31 , a spindle  32 , a holder  33 , and a motor (motor equipped with a speed reducer)  35 . The grinding wheel  31  is attached to the spindle  32 . The holder  33  rotatably supports the spindle  32 . Rotation of the motor  35  is transmitted to the spindle  32 , and the grinding wheel  31  rotates about a center line Ca of the grinding wheel  31  through the rotation of the motor  35 . The grinding wheel  31  of this embodiment has a cup shape (bottomed cylindrical shape), and includes a cylindrical portion  31   a  to be brought into contact with the end face  8  of the tapered roller  7 . The holder  33  is provided on a support table  36  of the wheel unit  30 . The support table  36  includes a first plate portion  37  having a flat-plate shape. A lower face  38  of the first plate portion  37  is a leveled and smooth face. 
     The wheel unit  30  having the structure described above is provided on the base  20 . That is, the base  20  supports the wheel unit  30  from below. The base  20  is mounted on the apparatus body (not illustrated) fixed to the work area. 
     The base  20  includes a lower mechanism portion  21  and a second plate portion  22 . The second plate portion  22  is provided on the lower mechanism portion  21 . The lower mechanism portion  21  and the second plate portion  22  are provided integrally. In this embodiment, however, the second plate portion  22  is supported on the lower mechanism portion  21  so as to be movable in the fore-and-aft direction. The second plate portion  22  and the wheel unit  30  located on the second plate portion  22  can be oscillated in the fore-and-aft direction by an oscillation mechanism  50  described later. An upper face  23  of the second plate portion  22  is a leveled and smooth face. The first plate portion  37  is placed on the second plate portion  22  in a state in which the lower face  38  of the first plate portion  37  is in surface contact with the upper face  23 . 
     The first plate portion  37  and the second plate portion  22  are coupled to each other by a shaft  27  having an axial center line set in a vertical direction. A coupling portion  29  that includes the shaft  27  and couples the first plate portion  37  and the second plate portion  22  to each other is provided at the ends of the first plate portion  37  and the second plate portion  22  on one side in the lateral direction (right side in  FIG. 1 ). The shaft  27  is rotatably supported by a bearing portion (rolling bearing)  28 . One of the shaft  27  and the rolling bearing  28  is provided on the first plate portion  37 , and the other is provided on the second plate portion  22 . The second plate portion  22  is a member on a fixed side. Thus, as illustrated in  FIG. 3 , the first plate portion  37  is swivelable about a center line C 1  in the vertical direction relative to the second plate portion  22 . When the first plate portion  37  swivels, the wheel unit.  30  swivels about the center line C 1 . 
     With the structure described above (as illustrated in  FIG. 1  and  FIG. 3 ), the base  20  including the second plate portion  22  is configured to support the wheel unit  30  including the first plate portion  37  so that the wheel unit  30  is swivelable about the center line C 1  in the vertical direction. The lower face  38  of the first plate portion  37  and the upper face  23  of the second plate portion  22  are smooth faces. Thus, both the faces slide, so that the wheel unit  30  can be swiveled easily. An oil film is preferably formed between the lower face  38  of the first plate portion  37  and the upper face  23  of the second plate portion  22 . 
     As illustrated in  FIG. 3 , the operation of swiveling the wheel unit  30  about the center line C 1  is performed by an operation mechanism  55 . The operation mechanism  55  includes a handle  56 , a screw shaft  57 , a support bracket  59 , and a nut member  58 . The handle  56  is operated by an operator. The screw shaft  57  rotates through rotation of the handle  56 . The support bracket  59  rotatably supports the screw shaft  57 . The nut member  58  moves along the screw shaft  57  through the rotation of the screw shaft  57 . The support bracket  59  is attached to the base  20  (second plate portion  22 ). The support bracket  59  is constructed such that the nut member  58  is movable together with the first plate portion  37 . The nut member  58  moves through the rotation of the screw shaft  57 , so that the wheel unit  30  including the first plate portion  37  swivels about the center line C 1 . When the wheel unit  30  is swiveled to a predetermined position, the wheel unit  30  is locked by a lock mechanism  60 . Thus, the wheel unit  30  is not swivelable. 
     The machining apparatus  5  includes the oscillation mechanism  50  for lapping. The oscillation mechanism  50  of this embodiment includes a ball screw apparatus and a linear guide (not illustrated). An axial direction of the ball screw apparatus and a guide direction of the linear guide correspond to the fore-and-aft direction. The ball screw apparatus and the linear guide are provided in the lower mechanism portion  21  of the base  20 . A moving element of the ball screw apparatus reciprocally moves with a small stroke, so that the wheel unit  30  can be oscillated in the fore-and-aft direction together with the second plate portion  22 . Thus, the machining apparatus  5  includes the oscillation mechanism  50  configured to linearly reciprocate the wheel unit  30  in the fore-and-aft direction. 
     In addition to the function of reciprocally moving the wheel unit  30  in the fore-and-aft direction with a small stroke as described above when lapping is performed on the tapered roller  7 , the oscillation mechanism  50  has a function of setting the position of the wheel unit  30  by moving the wheel unit  30  in the fore-and-aft direction (to be described later). That is, the position of the wheel unit  30  can be adjusted by moving the wheel unit  30  in the fore-and-aft direction with an increased movement stroke of the moving element of the ball screw apparatus. The moving element is movable together with the second plate portion  22 . The movement of the wheel unit  30  that is performed by the oscillation mechanism  50  is numerically controlled. Thus, the positional setting of the wheel unit  30  can be automated. 
     In a preparatory state in which the tapered roller  7  is moved to and from a machining position on the support mechanism  10  before and after the machining is performed by the grinding wheel  31 , the grinding wheel  31  is retreated to a retreat position. The retreat position is a position where the grinding wheel  31  is moved to one side in the lateral direction (left side in  FIG. 3 ). The machining apparatus  5  includes a mechanism configured to slide the grinding wheel  31  in the lateral direction (between the retreat position and the machining position) (this mechanism is referred to as a lateral movement mechanism  45 ). The lateral movement mechanism  45  has a function of restricting movement of the grinding wheel  31  in the lateral direction (that is, a function of locking the grinding wheel  31  at the machining position), and a function of pressing the grinding wheel  31  against the end face  8  of the tapered roller  7 . 
       FIG. 4  and  FIG. 5  are plan views illustrating a part of the machining apparatus  5  illustrated in  FIG. 1  and  FIG. 3 , respectively.  FIG. 1  illustrates a state in which the center line Ca of the grinding wheel  31  coincides with the lateral direction. This state is defined as a reference state.  FIG. 3  illustrates a state in which the wheel unit  30  in the reference state is swiveled clockwise in plan view about the center line C 1  by a predetermined angle.  FIG. 4  is a plan view of the reference state.  FIG. 5  is a plan view of the state in which the wheel unit  30  is swiveled (state of  FIG. 3 ). 
     As illustrated in  FIG. 5 , the grinding wheel  31  machines the end face  8  of the tapered roller  7  in contact with the end face  8 . As described above, the grinding wheel  31  of this embodiment has the cup shape, and includes the cylindrical portion  31   a  to be brought into contact with the end face  8 . The end face  8  is finished into a shape conforming to a spherical surface having a predetermined curvature radius. Therefore, the distal end face of the cylindrical portion  31   a  has a shape conforming to the target shape. The distal end face of the cylindrical portion  31   a  is partially brought into contact with the end face  8  of the tapered roller  7 . Since the grinding wheel  31  has the cup shape, the grinding wheel  31  is easily aligned with a machining point P 1 . 
     The tapered roller  7  is positioned by the support mechanism  10  (see  FIG. 2 ). The rotating grinding wheel  31  is brought into contact with the end face  8  of the rotating tapered roller  7 , and is reciprocally moved by the oscillation mechanism  50 . The center of an area where the grinding wheel  31  is brought into contact with the end face  8  is the machining point P 1 . The oscillation mechanism  50  performs the reciprocal movement in the fore-and-aft direction with the machining point P 1  set as the center. 
     The reference symbol “C 1 ” in  FIG. 4  and  FIG. 5  represents the center line serving as a swivel center of the wheel unit  30 . As illustrated in  FIG. 4  and  FIG. 5  (and also in  FIG. 1  and  FIG. 3 ), the machining point P 1  where the grinding wheel  31  is brought into contact with the end face  8  of the tapered roller  7  supported by the support mechanism  10  (see  FIG. 2 ) is located on an extension of the center line C 1  serving as the swivel center of the wheel unit  30 . As described above, in the preparatory state in which the tapered roller  7  is moved to and from the machining position on the support mechanism  10 , the grinding wheel  31  is retreated to the retreat position by the lateral movement mechanism  45  (see  FIG. 3 ). The grinding wheel  31  is kept out of contact with the end face  8  of the tapered roller  7 . When the grinding wheel  31  is moved to the machining position, the machining point P 1  is located on the extension of the center line C 1  serving as the swivel center of the wheel unit  30 . At the machining point P 1 , the grinding wheel  31  is brought into contact with the end face  8 . 
     In the machining apparatus  5  having the structure described above, when the part number of the tapered roller  7  or the curvature radius of the end face  8  of the tapered roller  7  is changed, the angle of the grinding wheel  31  needs to be changed. In plan view (see  FIG. 5 ), this angle is an angle B formed between the center line Cb of the tapered roller  7  and the center line Ca of the grinding wheel  31 . Even when the angle of the grinding wheel  31  is changed as described above, in the machining apparatus  5  of this embodiment, the machining point P 1  is located on the extension of the swivel center of the wheel unit  30  (center line C 1 ). Therefore, even when the angle of the grinding wheel  31  is changed, misalignment in the lateral direction and in the fore-and-aft direction between the machining point P 1  and the grinding wheel  31  is (substantially) zero. Thus, it is possible to save time and effort for positional adjustment of the wheel unit  30  in the fore-and-aft direction and in the lateral direction, and to therefore suppress a decrease in production efficiency. As a result, it is possible to omit the fore-and-aft adjustment mechanism and the lateral adjustment mechanism for positional adjustment, which are necessary in the related art (see  FIG. 7 ). Accordingly, the structure of the machining apparatus  5  is simplified. 
     In the machining apparatus  5  of this embodiment, the size (diameter) of the grinding wheel  31  may be changed in accordance with the change of the part number of the tapered roller  7 . In this case, the position of the wheel unit  30  needs to be set by moving the wheel unit  30  in the fore-and-aft direction. For example, when the diameter (cup diameter) of the grinding wheel  31  is set smaller, the wheel unit  30  needs to be moved downward in  FIG. 4  and  FIG. 5  in order to align the grinding wheel  31  with the machining point P 1 . The machining apparatus  5  of this embodiment includes the oscillation mechanism  50  as a component for lapping. This oscillation mechanism  50  is used for setting the position of the wheel unit  30  in the fore-and-aft direction along with the change of the size of the grinding wheel  31 . Therefore, even when the size of the grinding wheel  31  needs to be changed, there is no need to additionally provide the fore-and-aft adjustment mechanism as in the related art (see  FIG. 7 ). Accordingly, the machining apparatus  5  is simplified. 
     The embodiment disclosed above is illustrative but is not limitative in all respects. That is, the machining apparatus of the present invention is not limited to the illustrated embodiment, and other embodiments may be employed within the scope of the present invention. For example, the embodiment described above is directed to the case where lapping is performed. Alternatively, the machining apparatus of the present invention may be an apparatus configured to perform grinding. The workpiece to be machined may be a workpiece other than the tapered roller. The support mechanism  10  only needs to position and hold the tapered roller  7 , and may have a structure other than the structure including the two upper and lower rolls  11  and  12  and the single support member  13  as illustrated in  FIG. 2 . 
     According to the machining apparatus of the present invention, it is possible to save time and effort for positional adjustment of the wheel unit in the fore-and-aft direction and in the lateral direction even when the angle of the grinding wheel is changed. This makes it possible to suppress a decrease in production efficiency, and to omit the mechanism for the positional adjustment. As a result, the structure of the machining apparatus is simplified.