Abstract:
A machining device includes: a spindle unit including a spindle that rotates a workpiece; and a device base having the spindle unit mounted thereon. The spindle unit includes upper and lower rolls that rotate the workpiece by contacting the workpiece, upper and lower rotary shafts that rotate integrally with the upper and lower rolls and serves as the spindle, and a support member that supports the workpiece. The device base has mounted thereon the spindle unit, a motor that rotates the upper and lower rotary shafts, and a grindstone to be brought into contact with the workpiece. The spindle unit is detachably mounted on the device base.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2015-197393 filed on Oct. 5, 2015 including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to machining devices that machine a workpiece. 
         [0004]    2. Description of the Related Art 
         [0005]    Among machining devices that grind a workpiece of a cylindrical object such as a workpiece to be used as an inner ring or an outer ring of a rolling bearing, a machining device is known which uses a two-roll, one-shoe spindle mechanism as one type of spindle mechanism that rotates a workpiece when grinding of the workpiece is carried out (see, e.g., Japanese Patent Application Publication No. 2014-240094 (JP 2014-240094 A)). As shown in FIG. 10, the two-roll, one-shoe spindle mechanism has an upper roll 91 that contacts a workpiece W from above, a lower roll 92 that contacts the workpiece W from below, and a shoe 93 that prevents the workpiece W from falling off. 
         [0006]    The use of such a two-roll, one-shoe spindle mechanism is advantageous in that a workpiece can be loaded relatively quickly and idle time during operation can be reduced (the net operation rate can be improved). However, the two-roll, one-shoe spindle mechanism has the following disadvantages. In the two-roll, one-shoe spindle mechanism, components of the spindle mechanism such as the rolls are frequently required to be replaced or adjusted in position when the bearing number (specifications) of workpieces is changed. This work is complicated and increases the operation stop time of the machining device for changeover. As a result, the operation rate of the machining device is reduced, which results in reduction in productivity. 
         [0007]    A machining device (grinding machine) described in JP 2014-240094 A includes a position adjustment mechanism and an angle adjustment mechanism as a configuration that carries out changeover between workpieces. The position adjustment mechanism changes the positions in the up-down direction of the upper and lower rolls. The angle adjustment mechanism changes the tilt angles of the central axes of the upper and lower rolls with respect to the horizontal direction. 
         [0008]    In order to change the bearing number of workpieces (changeover), the position adjustment mechanism can adjust the positions of the upper and lower rolls 91, 92 and the angle adjustment mechanism can adjust the angle of the upper roll 91 by using a master workpiece. However, these adjustments need be made every time the bearing number is changed. In the case of machining many kinds of workpieces with different bearing numbers in small quantities, the operation of the machining device is stopped every time changeover is carried out, which may significantly reduce the operation rate of the machining device. Depending on the machining device, adjustment of a stopper for an upper frame (not shown) that is integral with the upper roll 91, adjustment of the position of a proximity switch for the rolls, etc. are required in addition to the above adjustments. This further increases the operation stop time. 
       SUMMARY OF THE INVENTION 
       [0009]    It is one object of the present invention to provide a machining device whose operation can be quickly resumed in the case of carrying out changeover between workpieces. 
         [0010]    According to one aspect of the present invention, a machining device includes: a spindle unit including a spindle that rotates a workpiece or a spindle that rotates a member for machining the workpiece; and a device base, on which the spindle unit is mounted. In the machining device, the spindle unit is detachably mounted on the device base. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    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: 
           [0012]      FIG. 1  is a perspective view showing a part of an embodiment of a machining device according to the present invention; 
           [0013]      FIG. 2  is a perspective view showing a device base having a spindle unit detached therefrom; 
           [0014]      FIG. 3  is a perspective view illustrating changeover that is carried by using a changeover cart; 
           [0015]      FIG. 4  is a sectional view of a lifting mechanism; 
           [0016]      FIG. 5  is a schematic view illustrating a connector structure for electrical wiring; 
           [0017]      FIG. 6  is a schematic view illustrating the connector structure for the electrical wiring; 
           [0018]      FIG. 7  is a schematic view of a connector unit mounted on the spindle unit; 
           [0019]      FIG. 8  is an illustration of the changeover cart; 
           [0020]      FIG. 9  is an illustration of a positioning mechanism and a fixing mechanism as viewed from above; and 
           [0021]      FIG. 10  is an illustration showing the general configuration of a conventional spindle mechanism. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    An embodiment of the present invention will be described below with reference to the accompanying drawings.  FIG. 1  is a perspective view showing a part of an embodiment of a machining device  1  according to the present invention. The machining device  1  is a device (grinding machine) that grinds a workpiece W. 
         [0023]    The machining device  1  rotates the workpiece W about its centerline and presses a grindstone  2  against the workpiece W to grind the workpiece W. The machining device  1  includes a spindle unit  10  and a device base  50 . 
         [0024]    The spindle unit  10  is mounted on a base platform  52  of the device base  50 . The spindle unit  10  has a frame body  20  assembled from a plurality of members. Components (rolls  11 ,  12 , a connector unit  24 , etc. described below) of the spindle unit  10  are supported by the frame body  20 . 
         [0025]    The spindle unit  10  has an upper roll  11  and a lower roll  12  which serve as rolls that rotates the workpiece W. The spindle unit  10  further has an upper rotary shaft  13  and a lower rotary shaft  14 . The upper rotary shaft  13  rotates integrally with the upper roll  11 , and the lower rotary shaft  14  rotates with the lower roll  12 . 
         [0026]    Each of the upper rotary shaft  13  and the lower rotary shaft  14  has a pulley, not shown, attached to its other end. Each of these pulleys is coupled to a pulley  17  (see  FIG. 2 ) via a drive belt (not shown). The pulley  17  is attached to an output shaft  15   a  of a motor  15 . As the motor  15  is rotated, the upper and lower rolls  11 ,  12  are rotated accordingly. These rolls  11 ,  12  contact the workpiece W, whereby the workpiece W can be rotated. 
         [0027]    The spindle unit  10  further has a support member (shoe)  16  that supports the workpiece W. The support member  16  prevents the workpiece W located between the rolls  11 ,  12  from falling off. The spindle unit  10  of the present embodiment is therefore a spindle unit including a two-roll, one-shoe spindle mechanism. 
         [0028]    The frame body  20  of the spindle unit  10  includes a base plate  21  in its lower part. The base plate  21  is a member that is placed horizontally over the base platform  52 . A guided portion  22  is disposed on a lower surface of the base plate  21 . The guided portion  22  is shaped to project so as to correspond to the shape of a dovetail groove  55  formed in the device base  50  described below. 
         [0029]    The device base  50  has a device stand  51  fixed to a floor and the base platform  52  fixed to the device stand  51 . The base platform  52  has a support plate  53  disposed horizontally in its upper part. The spindle unit  10  and the motor  15  are mounted on the support plate  53 . A grindstone unit including the grindstone  2  and a drive unit (not shown) that drives the grindstone  2  is a separate unit from the spindle unit  10 . In the present embodiment, the grindstone unit is mounted on the device stand  51 . However, the grindstone unit may be mounted on the base platform  52 . 
         [0030]    The base platform  52  of the device base  50  has a rail portion  54  and a clamp  56 . The rail portion  54  has the dovetail groove  55  and is fixed to the support plate  53 . The longitudinal direction of the dovetail groove  55  matches the front-rear direction of the machining device  1 . In the machining device  1 , the direction parallel to the centerline C 1  of the motor  15  is defined as the “right-left direction,” and the horizontal direction perpendicular to the right-left direction is defined as the “front-rear direction.” The direction perpendicular to the right-left direction and the front-rear direction is referred to as the up-down direction (vertical direction). 
         [0031]    The rail portion  54  has a rail plate  54   a  and a guide  54   b . The rail plate  54   a  is fixed to the support plate  53 , and the guide  54   b  can be displaced in the right-left direction with respect to the rail plate  54   a . The dovetail groove  55  extends between a sidewall  54   c  of the rail plate  54   a  and the guide  54   b  so that the width in the right-left direction of the dovetail groove  55  increases as closer to a bottom surface, or a lower surface, of the dovetail groove  55 . The clamp  56  of the present embodiment is formed by a clamp bolt and can clamp the guide  54   b  to the rail plate  54   a . The clamp  56  has a function to unclamp the guide  54   b  from the rail plate  54   a.    
         [0032]    As described above, the spindle unit  10  has the guided portion  22  at its lower surface, and the guided portion  22  is shaped to project so as to correspond to the shape of the dovetail groove  55 . With the guide  54   b  being unclamped from the rail plate  54   a  by the clamp  56 , the guided portion  22  can move in the front-rear direction along the rail portion  54 , namely the spindle unit  10  including the guided portion  22  can move in the front-rear direction along the rail portion  54 . 
         [0033]    With the guided portion  22  (spindle unit  10 ) being located at a predetermined position on the rail portion  54 , the clamp  56  clamps the guide  54   b  to the rail plate  54   a . The guided portion  22  (spindle unit  10 ) can thus be fixed to the rail portion  54  (base platform  52 ). The guided portion  22  (spindle unit  10 ) can be released from the rail portion  54  (base platform  52 ) by unclamping the guide  54   b  from the rail plate  54   a  by the clamp  56 . 
         [0034]    With the above configuration, the grindstone unit including the spindle unit  10 , the motor  15 , and the grindstone  2  is mounted on the device base  50 . The motor  15  is a drive source that rotates the upper rotary shaft  13  and the lower rotary shaft  14 . The grindstone  2  contacts the workpiece W. In order to machine the workpiece W, the spindle unit  10  is fixed at a predetermined position on the device base  50  (rail portion  54 ) (the state shown in  FIG. 1 ). The spindle unit  10  can be detached from the device base  50  by releasing the spindle unit  10  from the device base  50  (see  FIG. 2 ). The spindle unit  10  can thus be detachably mounted on the device base  50 . The component to be detached from the device base  50  is the spindle unit  10 , and as shown in  FIG. 2 , the motor  15  remains on the device base  50  (base platform  52 ). The drive belt (not shown) that connects the pulley  17  of the motor  15  to the upper rotary shaft  13  (see  FIG. 1 ) and the lower rotary shaft  14  is removed when the spindle unit  10  is detached from the device base  50 . In the present embodiment, in order to prevent interference between the spindle unit  10  and the motor  15  (pulley  17 ) when the spindle unit  10  is moved along the rail portion  54 , a motor base  18  having the motor  15  mounted thereon can be withdrawn by operating a lever  57 . 
         [0035]    As shown in  FIG. 3 , the spindle unit (first spindle unit)  10  detached from the device base  50  is placed on a changeover cart  70  (arrow G 1  in  FIG. 3 ). A second spindle unit  30  that has been placed on the changeover cart  70  can be placed on the device base  50  (rail portion  54 ) as shown by arrow G 2  in  FIG. 3 . In  FIG. 3 , each of the spindle units  10 ,  30  has a cover  19  attached thereto. 
         [0036]    The machining device  1  of the present embodiment further includes a lifting mechanism  35  (see  FIG. 1 ) in order to facilitate such attachment and detachment (replacement) of the spindle unit  10  to and from the device base  50 . The lifting mechanism  35  is a mechanism that makes the guided portion  22  float within the dovetail groove  55  by air. In the present embodiment, the spindle unit  10  is provided with the lifting mechanism  35 . That is, the lifting mechanism  35  is provided on the base plate  21  of the frame body  20  of the spindle unit  10 . The lifting mechanism  35  is placed in the four corners of the base plate  21  having a rectangular shape. The device base  50  is provided with an air supply unit (not shown) that generates pressurized air for the lifting mechanism  35 . The air supply unit is connected to the lifting mechanism  35  by an air pipe. 
         [0037]    The configuration of the lifting mechanism  35  will be specifically described. As shown in  FIG. 4 , the base plate  21  and the guided portion  22  located on the lower surface of the base plate  21  have a through hole  36  extending therethrough in the up-down direction. A lift-up head  37  (hereinafter referred to as the “head  37 ”) is disposed in the through hole  36  so as to be movable in the up-down direction. The through hole  36  has an enlarged space portion  36   a  and a small space portion  36   b . The enlarged space portion  36   a  is an upper part of the through hole  36  and the small space portion  36   b  is a lower part of the through hole  36 . A portion between the head  37  and the through hole  36  is sealed in the enlarged space portion  36   a . A lid  39  is placed over the through hole  36  to seal the through hole  36 . Air can be supplied to a space  38  created between the lid  39  and the head  37 . This air is supplied from the air pipe, not shown, via a nipple elbow  40  attached to the lid  39 . A ball support portion  41  is attached to a lower part of the head  37 . The ball support portion  41  has a ball element  41   a  that can roll on the rail plate  54   a  that forms the dovetail groove  55 . 
         [0038]    When air is supplied to the space  38 , the head  37  is moved downward and the ball support portion  41  in the lower part of the head  37  contacts and presses an upper surface of the rail plate  54   a . Since pressurized air is supplied, the guided portion  22  is made to float from the rail plate  54   a  by the pressure of the pressurized air. The ball support portion  41  can thus support the lifted spindle unit  10  including the floating guided portion  22 . Namely, the spindle unit  10  can float from the rail plate  54   a . In this state, the ball support portion  41  can be in rolling contact with the rail plate  54   a.    
         [0039]    The lifting mechanism  35  thus has a mechanism of an air cylinder using the head  37  as an air cylinder head. Moreover, the lifting mechanism  35  has the ball support portion  41  in the lower part of the head  37 . The lifting mechanism  35  can make the guided portion  22  float within the dovetail groove  55  (see  FIG. 1 ) by air. The ball support portion  41  can support the floating guided portion  22  while being in rolling contact with the rail plate  54   a  of the rail portion  54 . With the lifting mechanism  35 , the spindle unit  10  can be easily moved along the rail portion  54 . This further facilitates replacement of the spindle unit  10 . 
         [0040]    As described above, the spindle unit  10  can be attached to and detached from the device base  50  (see  FIGS. 1 and 2 ). The spindle unit  10  has a sensor  26  mounted thereon. The sensor  26  is an electrical device for control of the position of the upper roll  11  etc. with respect to the workpiece W. The device base  50  is provided with a power supply-side device  59  (see  FIG. 5 ) for the sensor  26 . Electrical wiring that connects the sensor  26  to the power supply-side device  59  has a connector structure J 1 . The power supply-side device  59  includes a power supply adapter, a control box, etc. for supplying electric power to the sensor  26  and receiving a signal from the sensor  26 . The electrical device may be a device other than the sensor  26  or may further include a device other than the sensor  26 . 
         [0041]      FIGS. 5 and 6  are schematic views illustrating the connector structure J 1  for the electrical wiring  49   a ,  49   b . The device base  50  has the power supply-side device  59  and a first connector (first electrical connector)  69 . As described above, the power supply-side device  59  is a power supply adapter etc. The first connector  69  is connected to the power supply-side device  59  via an electrical wire  49   a . The spindle unit  10  has a second connector (second electrical connector)  29  and the sensor  26  (electrical device). The second connector  29  can be attached to and detached from the first connector  69 . The sensor  26  is connected to the second connector  29  via an electrical wire  49   b .  FIG. 5  shows the first and second connectors  69 ,  29  connected together.  FIG. 6  shows the first and second connectors  69 ,  29  detached (disconnected) from each other. 
         [0042]    In this connector structure J 1 , the first connector  69  is disconnected from the second connector  29  when the (first) spindle unit  10  is detached from the device base  50 . When the second spindle unit  30  is mounted on the device base  50 , the first connector  69  of the device base  50  is connected to the second connector  29  of the second spindle unit  30 . These connectors  29 ,  69  are connected together by tightening a threaded member  69   a  of one connector  69  onto a threaded portion  29   a  of the other connector  29 . The connectors  29 ,  60  can thus be easily connected to and disconnected from each other. With the connector structure J 1 , connection of the electrical wiring etc. for changeover between workpieces W can be performed with high workability. 
         [0043]    As shown in  FIG. 7 , the second connector  29  of the spindle unit  10  is attached to the connector unit  24  disposed above the frame body  20 .  FIG. 7  is a schematic view of the connector unit  24  mounted on the spindle unit  10 . 
         [0044]    As described above, in the machining device  1  (see  FIG. 1 ), the spindle unit  10  is provided with the lifting mechanism  35 , whereas the device base  50  is provided with the air supply unit (not shown) that generates air flow to supply air to the lifting mechanism  35 . The air pipe that connects the lifting mechanism  35  to the air supply unit has a connector structure J 2  (see  FIG. 7 ). The connector structure J 2  has a connection structure similar to that shown in  FIGS. 5 and 6  (although the connector structure J 1  is for the electrical wiring and the connector structure J 2  is for the air pipe). As shown in  FIG. 7 , the connector structure J 2  has a pair of air connectors, namely a first connector (first air connector)  67  and a second connector (second air connector)  27 , which can be attached to and detached from each other. 
         [0045]    The spindle unit  10  (see  FIG. 1 ) further has a hydraulic cylinder  25  mounted thereon. The hydraulic cylinder  25  applies a force that presses the upper roll  11  against the workpiece W. The device base  50  is provided with a hydraulic unit (not shown) that generates an oil pressure to supply hydraulic oil to the hydraulic cylinder  25 . A hydraulic pipe that connects the hydraulic cylinder  25  to the hydraulic unit has a connector structure J 3  (see  FIG. 7 ). The connector structure J 3  has a connection structure similar to that shown in  FIGS. 5 and 6  (although the connector structure J 1  is for the electrical wiring and the connector structure J 3  is for the hydraulic pipe). As shown in  FIG. 7 , the connector structure J 3  has a pair of hydraulic oil connectors, namely a first connector (first hydraulic oil connector)  68  and a second connector (second hydraulic oil connector)  28 , which can be attached to and detached from each other. 
         [0046]    As shown in  FIG. 7 , all of the second connectors  27 ,  28 ,  29  are provided on the connector unit  24  of the spindle unit  10 . This further facilitates disconnection and connection of the first connectors  67 ,  68 ,  69  from and to the second connectors  27 ,  28 ,  29  between the spindle unit  10  and the device base  50  when the spindle unit  10  is replaced for changeover. 
         [0047]      FIG. 8  is an illustration of the changeover cart  70 . The machining device  1  includes the changeover cart  70 . The changeover cart  70  has wheels  80  and thus can be moved independently. While the first spindle unit  10  mounted on the device base  50  is machining the workpiece W, positioning adjustment of the second spindle unit  30  mounted on the changeover cart  70 , such as adjustment of the positions, tilts, etc. of the components like the upper and lower rolls  11 ,  12 , is made for changeover to the subsequent workpiece W of a different bearing number. The cover  19  is removed when the positioning adjustment is made. 
         [0048]    Since the changeover cart  70  can be moved independently, this positioning adjustment can be made in a place far from the device base  50 , where high workability is ensured. The changeover cart  70  is connected to the device base  50  when changeover is carried out (see  FIG. 3 ). As shown in  FIG. 3 , the first spindle unit  10  moved along the rail portion  54  and detached from the device base  50  can be mounted on the changeover cart  70 , and the second spindle unit  30  different from the first spindle unit  10  can also be mounted on the changeover cart  70 . 
         [0049]    As shown by arrow G 1  in  FIG. 3 , the first spindle unit  10  is detached from the device base  50  and mounted on the changeover cart  70 . Subsequently, as shown by arrow G 2  in  FIG. 3 , the second spindle unit  10  is moved from the changeover cart  70  onto the device base  50 . The spindle units  10 ,  30  have the same configuration (although the positions of the components such as the rolls  11 ,  12  are different between the spindle units  10 ,  30  as the positioning adjustment is made). As described above, the first spindle unit  10  can be detached from the device base  50  by moving the first spindle unit  10  along the rail portion  54  having the dovetail groove  55 . The second spindle unit  30  can also be mounted at a predetermined position on the device base  50  by moving the second spindle unit  30  along the rail portion  54 . 
         [0050]    The changeover cart  70  has a connection rail  71  that connects a body  81  of the changeover cart  70  to the device base  50  (device stand  51 ) as shown in  FIGS. 3 and 8  in order to replace the spindle unit  10  with the spindle unit  30 . The connection rail  71  can be located on the extension of the rail portion  54  when in use. The spindle units  10 ,  30  can be switched by operating the lifting mechanism  35  (see  FIGS. 1 and 4 ) and moving the spindle units  10 ,  30  along the connection rail  71 . The connection rail  71  can be folded downward for storage when not in use. 
         [0051]    In order to place the connection rail  71  on the extension of the rail portion  54  as described above, the changeover cart  70  is fixed at a predetermined position to the device base  50 . The machining device  1  (see  FIG. 8 ) further includes a positioning mechanism  72  and a fixing mechanism  75 . The positioning mechanism  72  positions the changeover cart  70  with respect to the device base  50 . The fixing mechanism  75  fixes the changeover cart  70  to the device base  50 . 
         [0052]      FIG. 9  is an illustration of the positioning mechanism  72  and the fixing mechanism  75  as viewed from above. The positioning mechanism  72  has a recessed fitting portion  73  and a projecting fitting portion  74 . Movement in the right-left direction of the changeover cart  70  is restricted when the projecting fitting portion  74  is fitted in the recessed fitting portion  73 . In the present embodiment, the recessed fitting portion  73  is fixed to the changeover cart  70 , and the projecting fitting portion  74  is fixed to the device base  50 . The changeover cart  70  is moved toward the device base  50  so that the recessed fitting portion  73  is fitted on the projecting fitting portion  74 , and in this state, the connection rail  71  can be located on the extension of the rail portion  54 . 
         [0053]    With the recessed fitting portion  73  and the projecting fitting portion  74  being fitted together, the changeover cart  70  is fixed to the device base  50  by the fixing mechanism  75 . The fixing mechanism  75  has a hook  76  and a projection  77  that can be engaged with the hook  76 . The changeover cart  70  is not allowed to move relative to the device base  50  in the front-rear direction when the hook  76  is engaged with the projection  77 . In the present embodiment, the fixing mechanism  75  has two sets of the hooks  76  and the projections  77 . The two sets of the hooks  76  and the projections  77  are placed on both the right and left sides of the positioning mechanism  72 . 
         [0054]    According to the machining device  1  having the above configuration, the first spindle unit  10  mounted on the device base  50  machines the workpiece W. While the first spindle unit  10  is machining the workpiece W, positioning adjustment of another spindle unit, or the second spindle unit  30  placed on the changeover cart  70 , such as adjustment of the positions, tilts, etc. of the components like the upper and lower rolls  11 ,  12 , can be made for a workpiece W of the subsequent bearing number. When changeover is carried out, the changeover cart  70  is positioned with respect to the device base  50  and fixed to the device base  50  by the positioning mechanism  72  and the fixing mechanism  75 . The first spindle unit  10  mounted on the device base  50  can thus be moved onto the changeover cart  70 , and the adjusted second spindle unit  30  mounted on the changeover cart  70  can be moved onto the device base  50 . Changeover is thus facilitated. When changeover between workpieces W is carried out, the spindle unit  10  on the device base  50  is replaced with the spindle unit  30  in this manner. Machining can thus be quickly resumed for the workpiece W of the subsequent bearing number. 
         [0055]    The device base  50  of the present embodiment ( FIG. 1 ) has the rail portion  54  having the dovetail groove  55 , and the clamp  56 . The guided portion  22  of the spindle unit  10  is shaped to project so as to correspond to the shape of the dovetail groove  55  and can be moved along the rail portion  54 . The clamp  56  has a configuration that can fix the guided portion  22  to the rail portion  54  with the guided portion  22  being located at the predetermined position on the rail portion  54  and that can release the guided portion  22  from the rail portion  54 . In this configuration, when the guided portion  22  is released from the rail portion  54  by the clamp  56 , the spindle unit  10  can be moved along the rail portion  54  having the dovetail groove  55 . This facilitates replacement of the spindle unit  10 . With the guided portion  22  being fixed to the rail portion  54  by the clamp  56 , the spindle unit  10  ( 30 ) is fixed to the device base  50 . In this state, the spindle unit  10  ( 30 ) can grind the workpiece W. 
         [0056]    With the lifting mechanism  35 , even if the spindle unit  10  ( 30 ) is heavy, the spindle unit  10  ( 30 ) can be easily moved along the rail portion  54  as the ball support portion  41  is in rolling contact with the rail portion  54 . This further facilitates replacement of the spindle unit  10  ( 30 ). As described above with reference to  FIGS. 5 and 6 , the use of the connector structure (J 1 ) facilitates connection and disconnection of the electrical wiring, etc. between the spindle unit  10  and the device base  50 . As a result, the operation stop time of the machining device  1  for changeover (changeover time) is reduced, which leads to improvement in productivity. 
         [0057]    The embodiment disclosed above is by way of example in all respects and is not restrictive. That is, the machining device of the present invention is not limited to the illustrated embodiment and may be embodied in other forms without departing from the spirit and scope of the present invention. The present invention is applicable to machining devices having a spindle unit including a spindle that rotates a supported workpiece. In particular, the present invention is effectively applicable to the case where adjustment of members of the spindle unit is required for changeover to a workpiece to be machined. For example, the present invention is applicable to a two-shoe device including a magnet chuck or a diaphragm chuck, or various other devices. The present invention is not limited to this and may be applied to machining devices including a spindle unit that rotates a member (tool) for machining a workpiece. For example, the present invention may be applied to a lathe, a milling machine, a drilling machine, a grinding machine using a grinding wheel, etc. The above embodiment is described with respect to the machining device that grinds a workpiece. However, the present invention may be applied to machining devices that perform other machining such as polishing and cutting. The workpiece is not limited to the one described in the above embodiment and may be other workpieces. 
         [0058]    According to the present invention, when changeover between workpieces is carried out, the spindle unit on the device base is replaced with another spindle unit. Machining can thus be quickly resumed for a workpiece of the subsequent bearing number. As a result, the operation stop time of the machining device  1  is reduced, which leads to improvement in productivity.