Abstract:
A twin rotation driving apparatus is provided, including a base body, an axle unit pivotally connected to the base body for carrying a workpiece, a first driving unit disposed on the base body and having a first gear set connected to the axle unit and a first motor coaxially connected to the first gear set, and a second driving unit disposed on the base body and having a second gear set connected to the axle unit and a second motor coaxially connected to the second gear set. The twin rotation driving apparatus includes two motors and two gear sets. Therefore, smaller motors can be included in the twin rotation driving apparatus, and the twin rotation driving apparatus is compact and can still generate great enough torques.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Taiwanese Patent Application No. 102140074, filed on Nov. 5, 2013, the disclosure of which is hereby incorporated by reference herein. 
         [0002]    1. Technical Field 
         [0003]    The present disclosure relates to rotatable machines, and, more particularly, to a twin rotation driving apparatus provided with a rotating body. 
         [0004]    2. Description of Related Art 
         [0005]    With the rapid increase of the operational speed of current computer numerical control (CNC) controllers as well as continuous advancement in computer-aided design (CAD) and computer-aided manufacturing (CAM), multi-axis machining technology has grown dramatically. 
         [0006]      FIG. 1  is a 3D schematic view of a conventional multi-axis machining apparatus  8 . The multi-axis machining apparatus  8  has a first track module  81  disposed on a machining platform  80  thereof, and an operation platform  82  disposed on the first track module  81 . Workpieces (not shown) are placed on the operation platform  82 . 
         [0007]    The machining platform  80  has a frame body  83  and a second track module  84  disposed on the frame body  83 . A third track module  85  is disposed on the second track module  84 . The first track module  81 , the second track module  84 , and the third track module  85  are aligned in a vertical line so that an operational system that is movable in X, Y and Z directions is formed. A supporting element  86  is disposed on the third track module  85 . The supporting element  86  has a rotary spindle head  1 . 
         [0008]    The rotary spindle head  1  comprises a fork base  10  and an axle unit  11 . The fork base  10  is rotational about the supporting element  86  (as indicated by an arrow direction C in  FIG. 1 ). A space  100  is between a left side  10   a  and a right side  10   b  of the shaft base body  10  for the axle unit  11  to be accommodated therein and axially connected to the fork base  10 . The axle unit  11  has a spindle  110  for clamping a cutter  9  and a rotatory base body  111  accommodated in the space  100  and driving the spindle  110 . The rotatory base body  111  swings in the space  100  (as indicated by an arrow direction A), and the cutter  9  is driven to swing and the fork base  10  is driven to rotate, so as to accomplish a multi-axis machining function. 
         [0009]    The rotary spindle head  1  can be driven by the servo motor provided with the gear reducer, driven by the torque motor, or driven by the torque motor provided with the gear reducer. 
         [0010]    U.S. Pat. Nos. 5,257,883 and 5,996,329 disclose the servo motor provided with the gear reducer. Since the servo motor outputs a torque that is small, the gear reducer has to have a reduction ratio as high as 10˜100, so as to amplify the torque and meet the work requirement for the rotary spindle head  1 . The gear reducer comprises worm wheels and belt wheels. However, the worm wheels are made of copper and are worn out easily, causing the gap between gear teeth to exceed a tolerate value. The drawbacks facilitate the disclosure of the torque motor that drives the rotary spindle head  1  directly. 
         [0011]    Taiwanese Patent No. 1314075 (the counterpart of U.S. Pat. No. 7,293,340) discloses the torque motors that drive the rotary spindle head  1  directly. The torque motor, though having a high torque value, a low power loss, and a high rotational speed, is costly and bulky as a higher torque is required. 
         [0012]    U.S. Pat. No. 7,470,095 discloses a torque motor provided with a gear reducer. The torque motor is not coaxially connected to the rotatory shaft of the rotary spindle head  1 . Therefore, the specificity of the torque motor and the disposing location of the transmission mechanism are limited. Moreover, inputs and outputs are not coaxial, thus achieving no dynamic equilibrium. 
         [0013]    Taiwanese Patent Publication No. 201204506 discloses a torque motor (not shown) and a planetary gear reducer (not shown) are disposed coaxially on the left side  10   a  (or the right side  10   b ) of the shaft base body  10  of the rotary spindle head  1 , so as to increase the torque density and distribute the loading evenly. 
         [0014]    However, during the operation of the planetary gear reducer described in Taiwanese Patent Publication No. 201204506, the positioning accuracy and repeatability accuracy of the axle unit  11  (as shown in  FIG. 1 ) will be affected by the gaps resulted from the engagements of the teeth of the planetary gears, the sun gear and the ring gear. 
         [0015]    Thus, there is an urgent need to solve the problems experienced in the conventional technology. 
       SUMMARY 
       [0016]    In light of the foregoing drawbacks of the prior art, the present disclosure proposes twin rotation driving apparatus, comprising: a base body; an axle unit pivotally connected to the base body for carrying a workpiece; a first driving unit disposed on the base body and having a first gear set connected to the axle unit and a first motor coaxially connected to the first gear set; and a second driving unit disposed on the base body, being coaxial with the first driving unit, and having a second gear set connected to the axle unit and a second motor coaxially connected to the second gear set. 
         [0017]    In an embodiment, two driving units are connected to the opposite sides of the base body with the same axis, enabling the driving unit to drive from two sides of the base body which even out the torque generated, and moreover, the two motors are coordinated to control the drive, thereby eliminating the gaps between engaged gear teeth. 
         [0018]    In another embodiment, the two gear sets are planetary modules functioning as a speed reducing mechanism, and the design of two gear sets enables more planetary gears to be disposed so as to distribute the loading carried. 
         [0019]    In summary, the present disclosure utilizes two motors (torque motors or servo motors), along with different gear sets to generate torque, which not only enables larger torque to be exerted by motors that are smaller in scale, but the overall twin rotation driving apparatus has a smaller turning diameter and smaller size, allowing the operation machine to have better performance in machining. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]    The present disclosure can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein: 
           [0021]      FIG. 1  is a schematic view of a conventional multi-axis machining device; 
           [0022]      FIG. 2  is a schematic view of a twin rotation driving apparatus according to the present disclosure; 
           [0023]      FIG. 3  is a front cross-sectional view of the twin rotation driving apparatus according to the present disclosure; 
           [0024]      FIG. 4  is a lateral schematic view of the twin rotation driving apparatus disclosed according to the present disclosure; and 
           [0025]      FIG. 5  is a top schematic view of the twin rotation driving apparatus disclosed according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a through understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
         [0027]    It is to be understood that the scope of the present disclosure is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. In addition, words such as “on”, “top” and “a” are used to explain the preferred embodiment of the present disclosure only and should not limit the scope of the present disclosure. 
         [0028]      FIGS. 2 and 3  show a twin rotation driving apparatus  2  according to the present disclosure. The twin rotation driving apparatus  2  comprises a base body  20 , an axle unit  23 , a first driving unit  21 , and a second driving unit  22 . 
         [0029]    The base body  20  has a first side  20   a  (the left side, for example), and an opposing second side  20   b  (the right side, for example). A dent  200  is disposed on a bottom surface  20   c  of the base body  20  and between the first side  20   a  and the second side  20   b,  to form a reverse U-shaped fork structure. The machine table, rotary or stationary, of a machine, vertical or horizontal, can be disposed on a top surface  20   d  of the base body  20 . The first side  20   a  and the second side  20   b  of the base body  20  have hollow structures, for the first driving unit  21  and the second driving unit  22  to be accommodated therein, respectively. 
         [0030]    The axle unit  23  is pivotally connected between the first side  20   a  and the second side  20   b  of the base body  20  and can be accommodated in the dent  200 , for a workpiece to be carried thereon. The workpiece is, but not limited to a cutter  9  (as shown in  FIG. 4 ) or a mechanical limb (e.g., a mechanical arm). The axle unit  23  has a spindle  230  for clamping the workpiece, and rotatory base bodies  231  and  232  pivotally connected to a first gear set  21   b  and a second gear set  22   b,  respectively, for driving the spindle  230 , as shown in  FIG. 3 . A gap H exists between the axle unit  23  and a top surface of the dent  200 . As shown in  FIG. 3 , the spindle  230  swings within the dent  200  (indicated as an arrow direction B) to drive the workpiece to swing back and forth. 
         [0031]    The first driving unit  21  is disposed on the first side  20   a  of the base body  20 , and has a first motor  21   a  and the first gear set  21   b.  The first motor  21   a  is coaxially connected to the first gear set  21   b,  and the first gear set  21   b  is connected to the axle unit  23 . The first motor  21   a  is, but not limited to a torque motor or a servo motor. The first gear set  21   b  is a gear reducer, such as a planetary gear reducer, a cycloidal gear reducer, a pin gear cycloidal reducer, a cycloidal planetary gear reducer, a planetary cycloidal pin gear reducer, and a simple harmonic drive gear reducer. 
         [0032]    The first motor  21   a  has a motor base body  210  positioned on the base body  20 , a ring motor stator  211  at the inner periphery of the motor base body  210 , a motor rotor  212  pivotally connected inside the motor stator  211 , and a shaft  213  connected to the motor rotor  212 . The shaft  213  and the motor base body  210  are connected using a bearing  214 , so as to generate a torque under the electro-magnetic function so as to enable the shaft  213  to drive the first gear set  21   b.    
         [0033]    As shown in  FIG. 4 , the first gear set  21   b  comprises a sun gear  215 , a plurality of planetary gears  216 , a ring gear  217 , and a planetary frame  218 . The first motor  21   a  drives the sun gear  215 , such that the planetary gears  216  are engaged between and around the sun gear  215  and the ring gear  217 . The ring gear  217  and the sun gear  215  are coaxially disposed on the base body  20 . The planetary gears  216  are pivotally connected to the planetary frame  218  using shaft elements  216   a.  The planetary frame  218  is connected to the axle unit  23 . 
         [0034]    The second driving unit  22  is disposed on the second side  20   b  of the base body  20 , being coaxial with the first driving unit  21 , and has a second motor  22   a  and the second gear set  22   b.  The second motor  22   a  is coaxially connected to the second gear set  22   b,  and the second gear set  22   b  is connected to the axle unit  23 . The second motor  22   a  is, but not limited to a torque motor or a servo motor. The second gear set  22   b  is a gear reducer, such as a planetary gear reducer, a cycloidal gear reducer, a pin gear cycloidal reducer, a cycloidal planetary gear reducer, a planetary cycloidal pin gear reducer, and a simple harmonic drive gear reducer. 
         [0035]    The second motor  22   a  has a motor base body  220  positioned on the base body  20 , a ring motor stator  221  disposed at the inner periphery of the motor base body  220 , a motor rotor  222  pivotally connected inside the motor stator  221 , and a shaft  223  connected to the motor rotor  222 . The shaft  223  and the motor base body  220  are connected using a bearing  224 , so as to generate a torque under the electro-magnetic function so as to enable the shaft  223  to drive the second gear set  22   b.    
         [0036]    As shown in  FIG. 4 , the second gear set  22   b  comprises a sun gear  225 , a plurality of planetary gears  226 , a ring gear  227 , and a planetary frame  228 . The second motor  22   a  drives the sun gear  225 , such that the planetary gears  226  are engaged between and around the sun gear  225  and the ring gear  227 . The ring gear  227  and the sun gear are coaxially disposed on the base body  20 . The planetary gears  226  are pivotally connected to the planetary frame  228  using shaft elements  226   a.  The planetary frame  228  is connected to the axle unit  23 . 
         [0037]    When the shaft  213 ,  223  of the first and second motor  21   a,    22   a  drives the sun gear  215 ,  225 , the planetary gears  216 ,  226  not only rotate on its own, but also have revolution movement resulting in speed reduction, allowing the planetary frame  218 ,  228  to rotate and drive the rotatory base bodies  231  and  232  and the spindle  230  of the axle unit  23  to rotate (or to swing). 
         [0038]    In worm wheels or gear reducers, each of the gears has only a single tooth for engagement generally. Therefore, all the stresses will be concentrated on a single point, and the gear teeth are easily damaged, and the transmission efficiency is poor. In the planetary gear reducer, a plurality of contact points are available when the teeth of the planetary gears are engaged with the teeth of the sun gear and the ring gear. As a result, with regard to the same torque the damage caused for the teeth is much less. Since the planetary gear reducers are compactly configured in concentric circles, they have the advantages of smaller in size, lightweight, high transmission efficiency, evened loading, high structural stiffness and well dynamic balance. Therefore in the present embodiment of the present disclosure, the planetary gear set with a plurality of planetary gears is used for the first and second gear set  21   b,    22   b  as the gear reducer. 
         [0039]    The first motor  21  a and the second motor  22   a  rotate in the same or opposite direction. During operation, the first motor  21   a  and the second motor  22   a  are coordinated to control the drive, allowing the torque exerted by the first motor  21   a  against the first gear set  21   b  and the axle unit  23 , and the torque exerted by the second motor against the second gear set  22   b  and the axle unit  23  will never be less than the static friction torque at the same time. Therefore, a torque exerted by at least one of the first and second motors  21   a  and  21   b  against the gear set and the axle unit  23  connected therewith will always greater than the static friction torque, and, as a result, any gaps between engaged teeth of the active gears (e.g., the sun gears  215 ,  225 ) and the passive gears (e.g., the planetary gears  216 ,  226  and the ring gears  217 ,  227 ) can be desirably eliminated. 
         [0040]    When the torques exerted by the two motors are at opposite directions, the overall torque exerted will be zero, which makes the axle unit  23  to be in a stationary state. 
         [0041]    When the toques exerted by the two motors are at the same direction, the overall torque exerted will be the sum of the torques exerted by the two motors, so as to increase the running torque and speed of the axle unit  23 , as well as the carrier cutting ability or increase the loading of the mechanical arms. For instance, when the same amount of torques exerted by the first driving unit  21  and the second driving unit  22  are at the same direction, the axle unit  23  is able to generate two times of running torque. 
         [0042]    The twin rotation driving apparatus  2  disclosed by the present disclosure utilizes the design of driving units  21 ,  22  on the inner side of the base body  20 , to produce much greater torque for torque motors that are much smaller in scale. For instance, in one preferred embodiment, with the driving units  21 ,  22  that is completely the same, when the maximum torque that the single torque motor can generate is 38.2 Nm, the maximum speed that the torque motor can generate is 4500 rpm, and the reduction ratio of the gear reducer is 57, the maximum torque to drive the axle unit  23  is 2177 Nm (38.2×57×1=2177.4 Nm), the swing movement speed is 79 rpm (4500÷57=78.95 rpm), and the turning diameter D (as shown in  FIG. 5 ) of the twin rotation driving apparatus  2  is 697 mm. Compared with conventional rotatory drive apparatus in which two torque motors directly drive the axle unit, the maximum torque of a single torque motor is 680 Nm, the maximum overall torque that the two torque motors can generate to drive the axle unit is 1360 Nm (680 Nm×2=1360 Nm), the swing movement speed is 60 rpm, and the turning diameter D is 780 mm, the present disclosure is smaller in size (smaller turning diameter), has a greater torque to drive the axle unit, and has a higher swing speed. 
         [0043]    Moreover, since the twin rotation driving apparatus  2  has a smaller turning diameter D (as shown in  FIG. 5 ) and a smaller size, a working machine having the twin rotation driving apparatus  2  has stronger machining capability (such as cutting) and larger working space and higher machining flexibility. 
         [0044]    In an embodiment, the base body  20  further has a brake  24  (including a brake disk  240 ), an angle encoder  25 , and a rotary encoder  26 , as shown in  FIG. 3 , to provide clamping, accurate positioning and speed control. In an embodiment, the brake  24 , the angle encoder  25 , and the rotary encoder  26  are installed on the inner part of the first side  20   a  and the second side  20   b  of the base body  20  according to the practical requirement, to effectively utilize the hollow space of the base body. The brake  24 , the angle encoder  25 , and the rotary encoder  26  in the present disclosure can be of many different variations and are not limited to any particular kind. 
         [0045]    In an embodiment, the first motor  21   a  and/or second motor  22   a  has a cooling passage  219 , 229 , as shown in  FIG. 3 , allowing a cooling fluid to pass therethrough. The cooling passage  219 ,  229  is located between the outer periphery of the motor stator  211 ,  221  and the motor base body  210 , 220 . 
         [0046]    The twin rotation driving apparatus disclosed by the present disclosure utilizes a fork structure to symmetrically dispose one motor and one gear reducer on each side of the two sides with the same axis, to drive the spindle to have swing movement. This design enables a plurality of gears (such as planetary gears) to be disposed in order to increase the area for carrying loading and also even out the distribution of loading. 
         [0047]    Moreover, the driving units on the two sides providing power to the axle unit to drive the spindle to swing have the advantage of evening out the torque driving the swing movement of the spindle, and thus providing a higher structural stiffness and better dynamic balance. 
         [0048]    In addition, the heat produced by the two motors are distributed in a symmetrical way against two sides of the base body, therefore is beneficial for the thermal deformation compensation of the spindle, so as to increase the accuracy in machining. 
         [0049]    Furthermore, two motors which are coordinated to control the drive eliminate the gaps between the engaged teeth of the planetary gears, sun gears, and the ring gears. 
         [0050]    It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.