Abstract:
A rotating table apparatus using a cam mechanism and having a higher precision than a conventional rotating table is realized. A rotating table apparatus having a driven shaft supported by a housing and driven by a driving device, and a rotating table which is rotatingly driven by said driven shaft using a cam and cam followers, wherein the rotating table apparatus has an opposing surface which opposes an end surface of the rotating table in a direction along a rotation shaft of said rotating table, and oil is intervened in between the opposing surface and said end surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/007,274 filed on Oct. 22, 2001, now U.S. Pat. No. 6,862,786, which claims the benefit of Japanese Patent Application No. 2000-325631 filed Oct. 25, 2000. The disclosure(s) of the above application(s) are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a rotating table apparatus, and particularly relates to a rotating table apparatus having a driven shaft supported by a housing and driven by a driving means, and a rotating table which is rotatingly driven by the driven shaft using a cam and cam followers. 
   2. Description of the Related Art 
   As a rotating table apparatus used for a conventional machine tool or the like, there is known a rotating table apparatus which attaches a worm wheel to a rotating table, gears a worm with this worm wheel, and rotatingly drives the rotating table by the rotation of the worm. 
   In such a rotating table apparatus, the worm deceleration mechanism has an inherent back-lash which may not be avoided due to its mechanism thereof. Therefore, various problems due to this back-lash, for example, when precise positioning of the rotating table is necessary, positioning is conducted by determining the rotation direction as one way, and further after the positioning there was a problem such as a clamp mechanism of a rotating table becoming separately needed. 
   SUMMARY OF THE INVENTION 
   In order to solve the above problems, there is proposed a rotating table apparatus using a cam mechanism. As the rotating table apparatus using the cam mechanism, for example there is a rotating table apparatus described in Japanese Utility Model Application No. Hei 3-126545. With this rotating table apparatus, by using the cam mechanism, various problems accompanying back-lash may be solved. 
   However, there is a large need for high precision of the rotating table apparatus, and a rotating table apparatus which may realize a higher precision is desired. 
   In the present invention, the object is to realize a rotating table apparatus with higher precision than a conventional rotating table. 
   A first invention in order to achieve the above object is a rotating table apparatus having a driven shaft supported by a housing and driven by a driving means, and a rotating table which is rotatingly driven by the driven shaft using a cam and cam followers; wherein 
   the rotating table apparatus has an opposing surface which opposes an end surface of the rotating table in a direction along the rotation shaft of the rotating table, and oil is intervened in between the opposing surface and the end surface. 
   A second invention in order to achieve the above object, in addition to the characteristics of the first invention, is a rotating table apparatus wherein there is provided a space in between the opposing surface and the end surface which is 0.005 mm or more and 0.2 mm or less. 
   A third invention in order to achieve the above object, in addition to the characteristics of the first and the second invention, is a rotating table apparatus wherein the opposing surface is a part of the housing. 
   A fourth invention in order to achieve the above object, in addition to the characteristics of any of the first to third inventions, is a rotating table apparatus wherein oil for lubricating the cam and the cam followers is provided in the housing, and a portion of oil intervenes in between the opposing surface and the end surface. 
   A fifth invention in order to achieve the above object, in addition to the characteristics of any of the first to fourth inventions, is a rotating table apparatus wherein the cam is a roller gear cam and the rotating table intermittently rotates. 
   A sixth invention in order to achieve the above object, in addition to the characteristics of any of the first to fifth inventions, is a rotating table apparatus wherein a tool is provided in the rotating table. 
   A seventh invention in order to achieve the above object, in addition to the characteristics of any of the first to fifth inventions, is a rotating table apparatus wherein the rotating table is provided with a chuck for chucking a workpiece to be a processing object. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a plan view showing a structure of a rotating table apparatus according to Embodiment 1; 
       FIG. 2  is a cross sectional view along the line X—X in  FIG. 1 ; 
       FIG. 3  is a cross sectional view showing a structure of a rotating table apparatus according to Embodiment 2; 
       FIG. 4  is a cross sectional view showing a structure of a table apparatus according to Embodiment 3; 
       FIG. 5  is a plan view showing a structure of a table apparatus according to Embodiment 4; 
       FIG. 6  is a cross sectional view along the line Y—Y in  FIG. 5 ; 
       FIG. 7  is a plan view showing a structure of a table apparatus according to Embodiment 5; 
       FIG. 8  is a cross sectional view along the line Z—Z in  FIG. 7 ; 
       FIG. 9  is a plan view showing an applied structure of a rotating table apparatus according to Embodiment 6; 
       FIG. 10  is a perspective view of  FIG. 9 ; 
       FIG. 11  is a view showing a structure of a rotating table apparatus according to Embodiment 7; and 
       FIG. 12  is a view showing a structure of a rotating table apparatus according to Embodiment 8. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   A first embodiment (Embodiment 1) of the present invention is with reference to  FIGS. 1 and 2  in which a structure of a rotating table apparatus  10  is described. 
   A driven shaft  20  is rotatably supported in respect to a housing  40 . This driven shaft  20  is provided with a roller gear cam  22  as a cam. 
   A rotating table  30  is rotatably supported in respect to the housing  40  by a second bearing  70 , with a rotation shaft  38  as the center. The second bearing  70  is structured by a first race  72 , a second race  74 , a roller  76 , and a V groove  36  formed in the rotating table  30 , and the second bearing  70  functions as a cross roller bearing. 
   Here, the first race  72  is fixed to the housing  40  by bolts, and the second race  74  is fixed to the first race  72  by bolts. Forming the V groove  36  in the rotating table  30  and structuring the second bearing  70  in this way is preferable in a view of increasing the supporting precision of the rotating table  30  in respect to the housing  40 . However, the rotating table  30  may be supported by using a general cross roller bearing or a bearing such as a ball bearing. 
   The rotating table  30  is provided with a plurality of cam followers  32  radially in the peripheral portion. These cam followers  32  gear with the roller gear cam  22  provided in the driven shaft  20 . 
   The gap portion  95  in the housing  40  is provided with oil for lubricating the roller gear cam  22  and the cam followers  32 . This oil is prevented from leaking outside of the rotating table apparatus  10  by a seal  90  and an O ring  80 . 
   An opposing surface  42 , opposing the end surface  34  along the direction of the rotation shaft  38  of the rotating table  30  is provided, and a space  50  is formed in between the end surface  34  and the opposing surface  42 . In this embodiment, the opposing surface  42  is formed by a portion of the housing  40  protruding in a direction along the rotation shaft  38 , but the opposing surface  42  may be formed by fixing a separate member to the housing  40 . However, it is more advantageous in view of cost, to form the opposing surface  42  from a portion of the housing  40  which protrudes in a direction along the rotation shaft  38 . Further, in order to realize the high precision of the rotating table apparatus, it is most preferable if the space  50  is 0.005 mm or more and 0.2 mm or less. 
   Further, this space  50  is linked with the gap portion  95 , so that a portion of oil provided in the gap portion  95  flows in to the space  50 . In this embodiment, by the space  50  being linked with the gap portion  95 , the rotating table apparatus  10  is simplified, but if it is such a structure that oil is present in the space  50 , the space and the gap portion do not necessarily have to be linked. 
   Operation of the rotating table apparatus  10  will now be described. 
   When the driven shaft  20  is driven by a driving means not shown such as a motor, the driven shaft  20  rotates in respect to the housing  40 . The roller gear cam  22  also rotates when the driven shaft  20  rotates, and via the cam followers  32  gearing with the roller gear cam  22 , the rotation driving force is transmitted to the rotating table  30 , and thus the rotating table  30  rotates with the rotation shaft  38  as the center. 
   In this way, when the driven shaft  20  is driven and the rotating table  30  rotates, the rotating table  30  conducts a slight oscillation. In this embodiment, as described above, oil is intervened in between the end surface  34  of the rotating table  30  and the opposing surface  42 , this oil functions as a damper, and swiftly decreases the oscillation generated in the rotating table  30 . As a result, the high precision of the rotating table apparatus  10  may be realized. 
   In particular, when the roller gear cam  22  and the cam followers  32  which gear therein are used to intermittently rotate the rotating table  30 , the oscillation when stopping and at time of stopping swiftly decreases as well as there being no deterioration of precision at stopping caused by back-lash. Thus, an intermittent rotating table apparatus with high precision may be realized, regardless of whether the rotating table  30  is rotating, is stopped or is at time of stopping, therefore it is extremely effective. 
   A second embodiment (Embodiment 2) of the present invention will now be described with reference to  FIG. 3 . 
   According to this embodiment, a positional relationship of cam followers  32  and a second bearing  70  in a direction of a rotation shaft  38  of a rotating table  30  differs to Embodiment 1, and other structures are similar to those in Embodiment 1. 
   In the above described Embodiment 1, the cam followers  32  are placed in a position nearer to a space  50  than the second bearing  70  in the direction of the rotation shaft  38  of the rotating table  30 . But in this embodiment, in a direction along the rotation shaft  38 , the second bearing  70  is in a position closer to the space  50  than the cam followers  32 . According to this embodiment, oil intervened between an end surface  34  of the rotating table  30  and an opposing surface  42  functions as a damper, and may swiftly decrease the oscillation generated in the rotating table  30 . As a result, the high precision of the rotating table apparatus  10  may be realized. 
   A third embodiment (Embodiment 3) will now be described with reference to  FIG. 4 . According to this embodiment, a structure of a rotating table  30  and a structure of a second bearing  70  differ to that of Embodiment 1, and other structures are the same as those in Embodiment 1. In this embodiment, the rotating table  30  comprises a top rail body  30   a  and a bottom rail body  30   b , and both are held by bolts. Further, the second bearing  70  is structured by a V groove  36  formed in an inner surface of the  30   b , a first race  72  fixed to a housing  40  by bolts, a second race  72  fixed to the first race  72  by bolts, and a roller  76 . 
   This embodiment is a preferred embodiment in a case the rotating table  30  has a large diameter. Also in this embodiment, oil intervened between an end surface  34  of the rotating table  30  and an opposing surface  42  functions as a damper, and may swiftly decrease the oscillation generated in the rotating table  30 . As a result, a high precision of a rotating table apparatus  10  may be realized. 
   A fourth embodiment (Embodiment 4) will now be described with reference to  FIGS. 5 and 6 . This embodiment uses a rotating table apparatus  10  according to Embodiment 1 as a rotation moving apparatus of a tool. In this embodiment, at an end portion of a rotating table  30  opposite to an end surface  34  along the direction of the rotation shaft  38  are radially provided a plurality of tools  97   a ,  97   b ,  97   c ,  97   d ,  97   e , and  97   f  for processing or the like of a workpiece not shown. 
   As a tool, there are various tools such as a screw tightening tool, a cutting tool, and a polishing tool. When processing or the like of the workpiece is performed by these tools  97   a ,  97   b ,  97   c ,  97   d ,  97   e , and  97   f , the tool receives an external force from the workpiece which is to be a processing object. The rotating table  30  oscillates by an action of an external force, but in this embodiment, since oil is intervened between an end surface  34  of the rotating table  30  and an opposing surface  42 , and this oil functions as a damper, oscillation generated in the rotating table  30  may be swiftly dampened. Therefore, the processing precision of the workpiece may be increased. 
   Further, when an impact load is added during processing the workpiece, the end surface  34  of the rotating table  30  is displaced and abuts the opposing surface  42 . Therefore, since the impact load may be received by not only the second bearing  70 , but also by the opposing surface  42 , the safety is high regarding excess weight. 
   Note that, in this embodiment, a plurality of tools  97   a ,  97   b ,  97   c ,  97   d ,  97   e , and  97   f  are provided so the respective tips are faced radially outward, these tools may be provided so that the respective tips face the direction along the rotation shaft  38 . 
   Further, the rotating table apparatus  10  according to Embodiment 2 and Embodiment 3 may be used as a rotation moving apparatus of the tool. 
   In particular, when a roller gear cam  22  and cam followers  32  which gear thereto are used to intermittently rotate the rotating table  30 , oscillation may be swiftly dampened when the rotating table  30  is stopped and is at time of stopping, as well as no deterioration of precision in stopping caused by back-lash. Therefore, tools may be chosen with high precision, regardless of whether the rotating table  30  is rotating, is stopped and is at time of stopping, so that it is extremely effective. 
   A fifth embodiment (Embodiment 5) will now be described with reference to  FIGS. 7 and 8 . In this embodiment, a supporting method of a rotating table  30  in respect to a housing  40  differs to that of Embodiment 4, and other structures are the same as those in Embodiment 4. 
   In this embodiment, in order to support the rotating table  30  in respect to the housing  40 , a pair of bearings  78   a  and  78   b  is used. According to this embodiment, similarly to Embodiment 4, an oscillation generated in the rotating table  30  may be swiftly dampened when conducting processing of a workpiece. Therefore, the precision in processing of the workpiece may be increased. Further, the safety is also high regarding excess weight. 
   A sixth embodiment (Embodiment 6) will now be described with reference to  FIGS. 9 and 10 . This embodiment applies a rotating table apparatus  10  according to Embodiment 4 and Embodiment 5 to a machine tool  110 . 
   The rotating table apparatus  10  which comprises tools are driven by a first moving control motor  120  and a second moving control motor  130 , and are movable in a P direction in  FIG. 9  and a Q direction in  FIG. 10  respectively. 
   A workpiece processed by a tool provided in the rotating table apparatus  10  is centered by a centering portion  140 , and chucking is conducted by a chuck portion  150 . 
   With a tool which is made to rotate by the rotating table apparatus  10  and which is positioned to oppose the workpiece by the first moving control motor  120  and the second moving control motor  130 , the processing is conducted on the workpiece which is centered and chucked by a centering portion  140  and a chucking portion  150 . The precision in processing is higher than that conventionally due to the reasons explained in Embodiment 4 and Embodiment 5. 
   In particular, in a case a rotating table  30  is intermittently rotated by using a roller gear cam  22  and cam followers  32  which gear thereto to choose a tool, and a workpiece W is processed by the chosen tool, the oscillation swiftly dampens when the rotating table  30  is stopped and is at time of stopping, as well as no deterioration of a precision in stopping of the rotating table  30  caused by back-lash. Thus, the tool may be chosen with high precision, and as a result the workpiece W may be processed with high precision. 
   A seventh embodiment (Embodiment 7) will now be described with reference to  FIG. 11 .  FIG. 11  is a diagram showing a structure of a rotating table apparatus according to Embodiment 7. 
   In the present embodiment, the rotating table apparatus  10  described in any of Embodiments 1 to 3 is provided with a chuck  160  for chucking a workpiece W which is to be a processing object. One end of the workpiece W to be the processing object is chucked by the chuck  160 , and the other end is abutted to a tail stock  170 , and when the rotating table apparatus  10  rotates, the chuck  160  and the workpiece W chucked by the chuck  160  also rotates. In this way processing is performed by an endmill  190  provided at an end portion of a spindle  180  to a rotating workpiece W. 
   When processing of the workpiece W is performed in this way, the rotating table apparatus  10  receives an external force via the chuck  160 . The rotating table  30  becomes easy to oscillate by receiving the external force, but in this embodiment, oil is intervened in between an end surface  34  of the rotating table  30  and an opposing surface  42 , and this oil functions as a damper, so that oscillation generated in the rotating table  30  may be swiftly dampened. 
   Therefore, the precision in processing of the workpiece W may be increased. Further, when an impact load is added during processing, an end surface  34  of the rotating table  30  is displaced and abuts the opposing surface  42 . Thus, the impact load is received not only by a second bearing  70 , but also by the opposing surface  42 , so that safety is also high regarding excess weight. 
   An eighth embodiment (Embodiment 8) will now be described with reference to  FIG. 12 . 
   This embodiment is a rotating table apparatus  10  described in any of Embodiments 1 to 3, attached with a workpiece W to be a processing object by bolts  200 , and the workpiece W also rotates when the rotating table apparatus  10  rotates. The workpiece W which rotates in this way, is processed by an end mill  190  provided at an end of a spindle  180 . 
   When processing of the workpiece W is conducted in this way, the rotating table apparatus  10  becomes easy to oscillate by receiving an external force. But in this embodiment, since oil is intervened between an end surface  34  of a rotating table  30  and an opposing surface  42 , this oil functions as a damper, and the oscillation generated in the rotating table  30  may be swiftly dampened. 
   Thus, precision in processing of the workpiece may be increased. Further, when an impact load is added during processing, an end surface  34  of the rotating table  30  is displaced and abuts the opposing surface  42 . Therefore, the impact load is received not only by the second bearing  70  but also by the opposing surface  42 , so that safety in regards to excess weight is also high. 
   According to a first invention, oil intervening between an end surface of a rotating table and an opposing surface functions as a damper, and swiftly decreases an oscillation generated in the rotating table. As a result, a high precision of a rotating table apparatus may be realized. 
   According to a second invention, oil intervening between an end surface of a rotating table and an opposing surface functions as a damper, and most swiftly dampens an oscillation generated in the rotating table. As a result, the high precision of the rotating table apparatus may be most appropriately realized. 
   According to a third invention, a rotating table apparatus having the effects of the first invention and the second invention may be realized at a low cost. 
   According to a fourth invention, a rotating table apparatus having any of the effects of the first to the third inventions may be realized with a simple structure. 
   According to a fifth invention, in addition to the effects of the invention described in any of the first to the fourth inventions, there is no deterioration of a precision in stopping due to back-lash, and the oscillation swiftly dampens when the rotating table is stopped or at time of stopping, so that an intermittent rotating table apparatus with a high precision may be realized, regardless of whether the rotating table is rotating, is stopped or is at time of stopping. 
   According to a sixth invention, in addition to the effects described in any of the first to the fifth inventions, the oscillation of the rotating table generated when such as a workpiece is processed by a tool is swiftly dampened, and the rotating table apparatus which may increase the processing precision of the workpiece may be realized. Further, a table apparatus may be realized which is hard to break even when an impact load is provided during processing by a tool, and which is highly safe in respect to an added weight. 
   According to a seventh invention, in addition to the effects described in any of the first to the fifth inventions, a workpiece to be a processing object is provided in the rotating table and an oscillation of a rotating table generated when processing of the workpiece is performed may be swiftly dampened, to realize the rotating table apparatus which may increase the processing precision of the workpiece. Further, a table apparatus may be realized which is hard to break even when an impact load is added whilst processing, and is highly safe regarding too much added weight.