Patent Publication Number: US-2009227412-A1

Title: Modular gear train mechanism with an internal motor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a train mechanism, especially to a train mechanism with an internal motor. 
     2. Description of Related Art 
     Mechanical control systems are widely used in production scheduling in factories, pull in scheduling of trains, antiskid designs for automobiles, temperature control for cold and warm air-conditioners, robots and so on. Train mechanisms are the necessary components in mechanical control systems. 
     As shown in  FIG. 1 , a conventional control system generally includes a sensor  1   a,  a controller  2   a,  a train mechanism  3   a  and a controlled field  4   a.  The controlled field  4   a  is a mechanical system or electronic system which needs to be controlled. The sensor  1   a  senses each output state  41   a  of the controlled field  4   a.  Each output state  41   a  and corresponding control commands  5   a  from a control end are input into the controller  2   a.  The controller  2   a  determines the error between the output state  41   a  and the control commands  5   a  and outputs a control signal  21   a  into the train mechanism  3   a,  so the train mechanism  3   a  can drive the controlled field  4   a  to execute the commands  5   a  from the control end. 
     Motor train mechanisms are usually used in the control systems. Generally, a motor train mechanism includes a motor and a retarding mechanism which coordinate with each other to reduce the rotary speed of the motor and improve the output torque force of the motor. However, in the conventional motor train mechanism, the motor is disposed outside, which causes that the whole volume of the motor train mechanism is very large. Besides, the space that some controlled fields can provide for connecting the motor train mechanism is limited, so it is inconvenience for mounting the motor train mechanism in the controlled fields. 
     Additionally, the retarding mechanism of the conventional motor train mechanism consists of a sun gear and a plurality of planet gears engaging with the sun gear and drives the motor to slow down according to different gear ratios of the sun gear and the planet gears, thereby improving the output torque force. Though achieving a desired output torque force, the conventional motor train mechanism has a complex structure, which causes a great friction force and high noise during operation. The greater the friction force is, the more the loss of the output torque force is. 
     Hence, the inventors of the present invention believe that the shortcomings described above are able to be improved and finally suggest the present invention which is of a reasonable design and is an effective improvement. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a modular gear train mechanism with an internal motor which has a small volume, simple components, low operation noise and low torque force loss. 
     To achieving the above-mentioned objects, a modular gear train mechanism with an internal motor in accordance with the present invention is provided. The modular gear train mechanism with an internal motor includes a hollow casing with an opening; a flywheel mounted in the casing, wherein a gear shaft is connected to an exterior of the flywheel and a first planet gear and a second planet gear are mounted on the gear shaft pivotally; a motor received in the flywheel and having a rotor shaft on which the flywheel is mounted pivotally; a fixing gear which is mounted between the exterior of the flywheel and an interior of the casing and fixed on an inner wall of the casing and engages with the first planet gear; a rotating gear rotatably surrounding the flywheel and engaging with the second planet gear; a top cap covering the casing and sealing the opening, the rotating gear connected to an inner wall of the top cap, wherein when the rotating gear turns, the rotating gear drives the top cap to turn; and a plurality of balls which are annularly distributed between the casing and the flywheel and between the casing and the top cap. 
     The efficacy of the present invention is as follows: since the motor is mounted in the casing, the train mechanism has a small volume, whereby it is convenient for mounting the train mechanism in a controlled field; furthermore, the internal components in the train mechanism have simple structures, so the noise and the friction force produced during the operation of the train mechanism is low, and the low friction force ensure that the loss of the output torque force decrease relatively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a conventional control system; 
         FIG. 2  is an assembled perspective view of a modular gear train mechanism with an internal motor according to the present invention; 
         FIG. 3  is an exploded perspective view of the modular gear train mechanism with an internal motor according to the present invention; 
         FIG. 4  is a cross-sectional view of the modular gear train mechanism with an internal motor according to the present invention; 
         FIG. 5  is an assembled view of a top cap of the present invention; 
         FIG. 6  is an exploded perspective view of another embodiment of the modular gear train mechanism with an internal motor according to the present invention; 
         FIG. 7  is a cross-sectional view of another embodiment of the modular gear train mechanism with an internal motor according to the present invention; 
         FIG. 8  is an assembled view of a bottom cap of the present invention; 
         FIG. 9  is a schematic view of the modular gear train mechanism with an internal motor according to the present invention, in motion; 
         FIG. 10  is a first schematic view showing the engagement of the first planet gears, the second planet gears, the rotating gear and the fixing gear of the present invention; 
         FIG. 11  is a second schematic view showing the engagement of the first planet gears, the second planet gears, the rotating gear and the fixing gear of the present invention; 
         FIG. 12  is a third schematic view showing the engagement of the first planet gears, the second planet gears, the rotating gear and the fixing gear of the present invention; and 
         FIG. 13  is a schematic view showing that the present invention is applied to a rotor. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 2  and  FIG. 3 , a modular gear train mechanism with an internal motor according to the present invention includes a hollow casing  1 , a flywheel  2 , a motor  3 , a fixing gear  4 , a rotating gear  5 , a top cap  6  and a plurality of balls  7 . The casing has an opening  11 , and the flywheel  2 , the motor  3 , the fixing gear  4  and the rotating gear  5  are received in the casing  1 . 
     As shown in  FIG. 3  and  FIG. 4 , two gear shafts  21  are connected to the exterior of the flywheel  2 . A fastening ring  211  is mounted on one end of each gear shaft  21  to fasten the gear shaft  21  on the surface of the flywheel  2 , and a gear shaft base  212  is formed on the other end of each gear shaft  21  and embedded in the flywheel  2 . 
     As shown in  FIG. 3  and  FIG. 4 , a first planet gear  22  and a second planet gear  23 , which have the same number of teeth, are mounted on each gear shaft  21  pivotally. Two first bearings  24  are respectively mounted on two corresponding ends of each gear shaft  21 . The first planet gear  22  and the second planet gear  23  are located between the two first bearings  24 . The corresponding two ends of each gear shaft  21  further pass through two wear resistance pieces  25  which are located between the two first shafts  24  and the flywheel  2 , respectively. The flywheel  2  has a protruding portion  26  protruding from the exterior thereof. 
     As shown in  FIG. 3  and  FIG. 4 , the motor  3  is received in the flywheel  2  and includes a rotor shaft  31  extending out of the protruding portion  26  of the flywheel  2 . The rotor shaft  31  is pivotally connected with a second bearing  32  which is mounted on the top cap  6 . The flywheel  2  is mounted on the rotor shaft  31  pivotally via the second bearing  32 . The second bearing  32  abuts against the protruding portion  26 . The rotor shaft  31  further passes through a gasket  33  located between the interior of the flywheel  2  and the exterior of the motor  3 . 
     As shown in  FIG. 3  and  FIG. 4 , a plurality of long-strip-shaped grooves  12  is annularly arranged at intervals in the inner wall of the casing  1 . The fixing gear  4  surrounding the flywheel  2  has a plurality of protruding strips  41  which is formed at intervals in the outer wall of the fixing gear  4 , corresponding to the grooves  12 . The protruding strips  41  engages with the grooves  12  so that the fixing gear  4  is fixed in the casing  1  and engages with the two first planet gears  22 . The rotating gear  5  is rotatably mounted between the exterior of the flywheel  2  and the interior of the top cap  6  and engages with the two second planet gears  23 . When turning, the second planet gears  23  drive the rotating gear  5  to turn synchronously. The teeth of the fixing gear  4  must be less than that of the rotating gear  5  to produce a gear reduction ratio, thereby the rotor shaft  31  can decelerate. 
     As shown in  FIG. 3  and  FIG. 5 , the top cap  6  includes a first base portion  61  and a first plate body  62 . The first base portion  61  has two first tenons  611  which are jointed on two diagonal positions of the first plate body  62 , respectively. The first base portion  61  of the top cap  6  covers the casing  1  and seals the opening  11 . The first base portion  61  extends into the casing  1  and has a plurality of long-strip-shaped grooves  612  annularly arranged at intervals in the inner wall thereof. The rotating gear  5  has a plurality of protruding strips  51  formed at intervals in the outer wall thereof, corresponding to the grooves  612 . The protruding strips  51  engage with the grooves  612  so that the rotating gear  5  is connected to the inner wall of the top cap  6 . When the rotating gear  5  turns, it drives the top cap  6  to turn synchronously. 
     As shown in  FIG. 3  and  FIG. 4 , the casing  1 , the first planet gears  22 , the second planet gears  23 , the fixing gear  4 , the rotating gear  5  and the top cap  6  are made of engineering plastics. The balls  7  are made of steel and have great supporting forces and high reliability. The balls  7  are annularly distributed between the casing  1  and the flywheel  2  and between the casing  1  and the top cap  6 . The balls  7  are used as sliding mediums, which are coated with lubricating oil to reduce friction forces between the balls and the casing  1 , the flywheel  2  and the top cap  6 . The present invention further includes a fixing ring  8  which is locked on the exterior of the casing  1  via grub screws with hexagon holes to surround the top cap  6 , and the balls  7  are annularly distributed between the top cap  6  and the fixing ring  8 . 
     As shown in  FIGS. 6-8 , in another embodiment, the casing  1 ′ includes a hollow body  11 ′ and a bottom cap  12 ′. The hollow body  11 ′ has two openings  111 ′ respectively formed in two corresponding ends thereof. A plurality of long-strip-shaped grooves  112 ′ is annularly arranged at intervals in the inner wall of the hollow body  11 ′, corresponding to the protruding strips  41 . The protruding strips  41  of the fixing gear  4  engage with the grooves  112 ′ to fix the fixing gear  4  in the hollow body  11 ′. The bottom cap  12 ′ is fixed on one of the openings  111 ′ of the hollow body  11 ′ and seals the opening  111 ′. The bottom cap  12 ′ includes a second base portion  121 ′ and a second plate body  122 ′. The second base portion  121 ′ has two second tenons  1211 ′ which are jointed on two diagonal positions of the second plate body  122 ′, respectively. The motor  3  is locked on the other diagonal positions of the second plate body  122 ′ via screws. The balls  7  are annularly distributed between the hollow body  11 ′ and the top cap  6  and between the bottom cap  12 ′ and the flywheel  2 . The fixing ring  8  is locked on the exterior of the hollow body  11 ′ via grub screws with hexagon holes. 
     As shown in  FIG. 4  and  FIG. 9 , when the motor  3  is electrically connected to an external power source (not shown), the rotor shaft  31  of the motor  3  starts to turn and drives the flywheel  2  to turn. When the fly wheel  2  turns, the first planet gear  22  and the second planet gear  23  respectively engaging with the fixing gear  4  and the rotating gear  5  will turn on the gear shaft  21 . At this time, the fixing gear  4  is stationary in the casing  1  and the second planet gear  23  drives the rotating gear  5  to turn. When the rotating gear  5  turns, it will drive the top cap  6  to turn synchronously. By the way, a screw may be connected with the output end (the top cap  6 ) of the train mechanism and driven to move linearly and telescopically (not shown) by the train mechanism. 
     It is worthwhile to mention that the two first planet gears  22 , the two second planet gears  23 , the fixing gear  4  and the rotating gear 5  have specially designed tooth shapes. Otherwise, when the first planet gears  22  and the second planet gears  23  turn, the fixing gear  4  and the rotating gear  5  cannot be in the correct states, that is, one gear is stationary and the other gear is in motion. The design for the tooth shapes of the gears is as follows: 
     1. The first planet gears  22  and the second planet gears  23  have convex teeth with the same tooth shape, of which side appearances are slightly shaped like an isosceles trapezoid. 
     2. Side appearances of convex teeth of the fixing gear  4  and the rotating gear  5  are slightly shaped like isosceles trapezoids, and the tooth width of the convex teeth of the fixing gear  4  is slightly greater than that of the convex teeth of the rotating gear  5 . 
     3. The maximum tooth width of the convex teeth of the fixing gear  4  and the rotating gear  5  is greater than that of the convex teeth of the first planet gears  22  and the second planet gears  23 . 
     As shown in  FIG. 10 , the convex teeth of the first planet gears  22  and the second planet gears  23  respectively extend into tooth seams between adjacent convex teeth of the fixing gear  4  and the rotating gear  5 . The tops of the convex teeth of the first planet gears  22  and the second planet gears  23  respectively collide with the bottoms of the tooth seams of the fixing gear  4  and the rotating gear  5 . As shown in  FIG. 11 , then the side portions of the convex teeth of the first planet gears  22  and the second planet gears  23  respectively collide with the side portions of the convex teeth of the fixing gear  4  and the rotating gear  5 . As shown in  FIG. 12 , finally, the side portions of the convex teeth of the first planet gears  22  and the second planet gears  23  respectively move to the tops of the convex teeth of the fixing gear  4  and the rotating gear  5  along the side portions of the convex teeth of the fixing gear  4  and the rotating gear  5 , thereby the convex teeth of the first planet gears  22  and the second planet gears  23  respectively extend into next tooth seams of the fixing gear  4  and the rotating gear  5 . 
     As shown in  FIG. 13 , the train mechanism of the present invention coordinates with a visual image unit  10  and a servo control unit  20  to control a robot  30 . The train mechanism of the present invention is mounted on each action joint of the robot  30 . The signal transmission between the visual image unit  10 , the servo control unit  20  and the modular train mechanism is achieved according to the RS-232 serial communication protocol or the RS-485 serial communication protocol. Assuming that the robot  30 &#39;s task is to move to a destination along the shortest path, the visual image unit  10  determines external image information and plans the shortest path to the destination, and the servo control unit  20  determines the information for the shortest path and outputs a proper control force to the train mechanisms mounted on the robot  30 , so that the train mechanisms drive the robot  30  to move along the shortest path planned by the visual image unit  10 . 
     Consequently, the advantages of the modular gear train mechanism with an internal motor of the present invention are as follows: 
     1. The motor  3  is mounted in the casing  1 , so the train mechanism has a small volume, whereby it is convenient for mounting the train mechanism in a controlled field. Furthermore, the internal components in the train mechanism have simple structures, so the noise and the friction force produced during the operation of the train mechanism is low, and the low friction force ensure that the loss of the output torque force decrease relatively. 
     2. The casing  1 , the first planet gears  22 , the second planet gears  23 , the fixing gear  4 , the rotating gear  5  and the top cap  6  are made of engineering plastics which has a low cost, high plasticity and high intensity and ensures that the noise cause by friction and collision of the components is low. 
     3. The protruding portion  26  is formed to avoid direction friction between the second bearing  32  and the flywheel  2 . 
     4. The wear resistance pieces  25  are mounted to reduce the friction force between the first bearing  24  and the flywheel  2 . 
     5. The gasket  33  reduces the friction force produced when the flywheel  2  and the rotor shaft  31  contact with each other. 
     What are disclosed above are only the specification and the drawings of the preferred embodiments of the present invention and it is therefore not intended that the present invention be limited to the particular embodiments disclosed. It will be understood by those skilled in the art that various equivalent changes may be made depending on the specification and the drawings of the present invention without departing from the scope of the present invention.