Patent Publication Number: US-2017370459-A1

Title: Power transmission device

Description:
TECHNICAL FIELD 
     The present inventive concept relates to a power transmission device, and more particularly, to a power transmission device which may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts because not only the overall height of a device, but also an exterior size thereof may be remarkably reduced. 
     BACKGROUND ART 
     Power transmission devices are a series of devices implementing a linear motion, a curved motion, a circular motion, etc. of a device by using rotational power of a motor. 
     The power transmission devices have been widely used for various industrial machines including semiconductor equipment, flat display equipment for LCDs, PDPs, OLEDs, etc. Such power transmission devices have been already filed by and registered to the present applicant. 
       FIG. 1  is a side view illustrating a configuration of a power transmission device according to the related art in a use state. 
     Referring to  FIG. 1 , the power transmission device  1  according to the related art may be partially coupled to a slider  3 , for example, to allow the slider  3  coupled to a base plate  2  in a structure of a rail  4  to have a linear motion. 
     For the linear motion of the slider  3  with respect to the base plate  2 , the power transmission device  1  connected to the slider  3  may include a pinion  6  or a pin gear that is engaged with a rack  5  fixed to an area of the base plate  2 . A separate motor  8  is provided outside the pinion  6  and connected to the pin gear  6 . 
     The pinion  6  is coupled to an end portion of a shaft  7  extending outwardly from the power transmission device  1  and engaged with the rack  5  during the assembly of the device of  FIG. 1 . 
     In the above structure, when a motor  8  is driven, the shaft  7  is rotated based on interactions of built-in parts of the power transmission device  1  and thus the pinion  6  is rotated. 
     As the pinion  6  is engaged with the rack  5  that is positionally fixed, the pinion  6  is consequently rotated, performing a linear motion along a lengthwise direction of the rack  5 , and thus the linear motion of the slider  3  with respect to the base plate  2  may be implemented. 
     Accordingly, when a desired part or apparatus is mounted on the slider  3 , the part or apparatus may perform a linear motion. 
     The structure of the power transmission device  1  of  FIG. 1  is one of the most used shapes at sites. Since the motor  8  is directly coupled to a rotation shaft of the pinion  6  with a decelerator  9 , the overall height H 1  of the power transmission device  1  may be increased. 
     When the overall height H 1  of the power transmission device  1  is increased as in the related art, the power transmission device  1  becomes huge in size accordingly and thus there may be some restrictions in the application of the power transmission device  1  to compact equipment such as an INDEX that is widely used for semiconductor or flat display equipment. In this regard, there is a demand for complementation for the structure of a power transmission device. 
     DETAILED DESCRIPTION OF THE INVENTIVE CONCEPT 
     Technical Problem 
     The present inventive concept provides a power transmission device which may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts because not only the overall height of a device, but also an exterior size thereof may be remarkably reduced. 
     Advantageous Effects 
     According to the present inventive concept, since not only the overall height of a device, but also an exterior size thereof may be remarkably reduced, the power transmission device may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating a configuration of a power transmission device according to the related art in a use state. 
         FIG. 2  is a power transmission device according to an embodiment of the present inventive concept. 
         FIG. 3  is a schematic structural view of the power transmission device of  FIG. 2 . 
         FIG. 4  is an exploded perspective view of a power transfer pin and a pin rotation support portion. 
         FIG. 5  is a cross-sectional view taken along a line A-A of  FIG. 3 . 
         FIG. 6  is an enlarged view of an external rotor motor portion of  FIG. 5 . 
         FIG. 7  illustrates a modified example of the power transfer pin. 
     
    
    
     BEST MODE 
     According to an aspect of the present inventive concept, a power transmission device includes a plurality of power transfer pins mutually corresponding to a tooth shape formed on an outer gear to move the outer gear and having an arrangement structure of a circular shape; a pin rotation support portion connected to the plurality of power transfer pins and rotatably supporting the plurality of power transfer pins; and an external rotor motor portion arranged inside in a radial direction of the pin rotation support portion and connected to the pin rotation support portion, and generating rotational power to rotate the pin rotation support portion arranged outside. 
     The external rotor motor portion may include a rotor connected to the pin rotation support portion inside in the radial direction of the pin rotation support portion and rotating with the pin rotation support portion; and a stator fixedly arranged inside a radial direction of the rotor and rotating the rotor by an applied current. 
     The pin rotation support portion may rotatably support the power transfer pin and including a rotor connection body forming one body with the rotor. 
     The rotor connection body may be provided in a pair, each rotor connection body arranged at each of opposite end portions of the power transfer pins and connected to the plurality of power transfer pins. 
     The pin rotation support portion may further include a plurality of pin support bearings arranged at many as the number of the plurality of power transfer pins at equiangular intervals along a circumferential direction of the rotor connection body, and supporting a rotation motion of the plurality of power transfer pins. 
     The pin rotation support portion may further include a plurality of oil seals provided corresponding to the plurality of pin support bearings one by one and seals a pin insertion support hole in the rotor connection body in which the plurality of power transfer pins are inserted and supported. 
     The external rotor motor portion may further include a fixed shaft arranged inside the stator. 
     The power transmission device may further include an absolute position sensor coupled to an end portion of the fixed shaft and detecting absolute positions of the plurality of power transfer pins. 
     The power transmission device may further include a closing cap coupled to a periphery of the external rotor motor portion and protecting the external rotor motor portion. 
     The power transmission device may further include a heat sink arranged around the plurality of power transfer pins and radiating heat generated from the external rotor motor portion. 
     The power transmission device may further include a control circuit provided in the heat sink. 
     An air flow space portion for air flow may be formed between the external rotor motor portion and the control circuit in the heat sink. 
     The outer gear may be one of a rack, an external gear, and an internal gear. 
     MODE OF THE INVENTIVE CONCEPT 
     The attached drawings for illustrating preferred embodiments of the present inventive concept are referred to in order to gain a sufficient understanding of the present inventive concept, the merits thereof, and the objectives accomplished by the implementation of the present inventive concept. 
     Hereinafter, the present inventive concept will be described in detail by explaining preferred embodiments of the inventive concept with reference to the attached drawings. Like reference numerals in the drawings denote like elements. 
       FIG. 2  is a power transmission device according to an embodiment of the present inventive concept.  FIG. 3  is a schematic structural view of the power transmission device of  FIG. 2 .  FIG. 4  is an exploded perspective view of a power transfer pin and a pin rotation support portion.  FIG. 5  is a cross-sectional view taken along a line A-A of  FIG. 3 .  FIG. 6  is an enlarged view of an external rotor motor portion of  FIG. 5 . 
     Referring to these drawings, a power transmission device according to the present embodiment may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts because not only the overall height of a device, but also an exterior size thereof may be remarkably reduced. The power transmission device may include a plurality of power transfer pins  120  having an arrangement structure of a circular shape and moving a rack  110  as an output gear mutually engaged via a rack tooth shape  111  formed in the rack  110 , a pin rotation support portion  130  rotatably supporting the power transfer pins  120 , and an external rotor motor portion  160  arranged inside in a radial direction of the pin rotation support portion  130  and generating rotational power to rotate the pin rotation support portion  130 . 
     For reference, although the rack  110  is disclosed as an outer gear in the present embodiment, the outer gear may be an external gear or an internal gear having a circular shape. 
     For example, when the outer gear is the rack  110  as illustrated in  FIG. 2 , the rack  110  may perform a linear motion as the power transmission device  100  according to the present embodiment is driven. 
     In contrast, when the outer gear is an external gear or an internal gear, the external gear or the internal gear may perform a rotational motion as the power transmission device  100  according to the present embodiment is driven. 
     A rack tooth shape  111  is formed at one side of the rack  110 . The rack tooth shape  111  is continuously and uniformly formed at one side of the rack  110  along a lengthwise direction of the rack  110 . 
     The rack tooth shape  111  formed on the rack  110  may be any one of a trochoid tooth shape, a cycloid tooth shape, and an involute tooth shape. 
     As such, the power transfer pins  120  are provided such that the rack  110  may perform a linear motion. In the present embodiment, the power transfer pins  120 , as a power source for moving the rack  110 , performs a rotational motion in place corresponding to the rack tooth shape  111  of the rack  110 . The power transfer pins  120  may have an arrangement structure of a circular shape. 
     Next, as illustrated in detail in  FIG. 4 , the pin rotation support portion  130 , as a structure connected to the power transfer pins  120  having an arrangement structure of a circular shape, rotatably support the power transfer pins  120 . 
     The pin rotation support portion  130  may include a rotor connection body  140 , a pin support bearing  151 , and an oil seal  152 . 
     The rotor connection body  140  is a structure rotatably supporting the power transfer pins  120  and forming one body with a rotor  161 . 
     The rotor connection body  140  is arranged in a pair at opposite end portions of the power transfer pins  120  and connected to the power transfer pins  120 . 
     In other words, the rotor connection body  140  is arranged in a pair spaced apart in parallel from each other by a length of the power transfer pins  120  or less. The pair of rotor connection bodies  140  are connected to the opposite end portions of the power transfer pins  120  and rotatably supporting the power transfer pins  120 . 
     A plurality of pin insertion support holes  141 , in which the power transfer pins  120  are inserted and supported, are provided in the rotor connection body  140  at equiangular intervals along a circumferential direction. 
     The pin support bearing  151  is arranged as many as the number of the power transfer pins  120  at the equiangular intervals along the circumferential direction of the rotor connection body  140 , and support a rotation motion of the power transfer pins  120 . 
     The pin support bearing  151  may employ various rolling bearings having superior rigidity including a ball bearing. 
     The oil seal  152  is provided corresponding to the pin support bearing  151  one by one and seals the pin insertion support hole  141  in the rotor connection body  140  in which the power transfer pins  120  are inserted and supported. 
     In the present embodiment, since the rotor connection body  140  is provided in a pair, the pin support bearing  151  and the oil seal  152  are applied to each of the pair of the rotor connection bodies  140 . 
     In other words, the rotor connection body  140 , the pin support bearing  151 , and the oil seal  152  may form a symmetric structure with respect to the power transfer pins  120 . Accordingly, an assembly work may be easy. 
     The external rotor motor portion  160  is arranged inside in the radial direction of arranged inside in the radial direction of the pin rotation support portion  130  and connected to the pin rotation support portion  130 , and generates rotational power to rotate the pin rotation support portion  130  arranged outside the external rotor motor portion  160 . 
     In other words, in the power transmission device  100  of the present embodiment, while the external rotor motor portion  160  is arranged inside the pin rotation support portion  130 , the external rotor motor portion  160  rotates the pin rotation support portion  130  and the power transfer pins  120  that are structures arranged outside the external rotor motor portion  160 . 
     In this case, not only a complicated structure of directly connecting the separate motor  8  as illustrated in  FIG. 1  is not needed, but also the overall height of a device as well as the exterior size thereof may be remarkably reduced and thus the power transmission device may be easily applied to semiconductor or flat display equipment requiring compact parts, in particular to compact equipment such as an INDEX. 
     The external rotor motor portion  160  is connected to the pin rotation support portion  130  inside in the radial direction of the pin rotation support portion  130 , and may include the rotor  161  rotated with the pin rotation support portion  130  and a stator  162  fixedly arranged inside in a radial direction of the rotor  161  and rotating the rotor  161  by an applied current. 
     The rotor  161  is provided as a magnet, and the stator  162  is provided as a coil structure with an electric line wound therearound. 
     Accordingly, as illustrated in  FIG. 6 , when current is applied to the stator  162 , a magnetic force is generated according to the Fleming&#39;s law. By alternately changing the polarity of current, the rotor  161  that is a magnet is rotated according to the polarity of induced magnetism. 
     Since the rotor connection body  140  is coupled to the rotor  161 , as the rotor  161  rotates, the rotor connection body  140  rotates together and thus the power transfer pins  120  may be induced to be rotated. 
     A fixed shaft  163  is provided inside the stator  162 . Unlike the rotor  161  that is rotatable, the fixed shaft  163  is fixed without being rotated. 
     Accordingly, the fixed shaft  163  may be provided with a sensor such as an absolute position sensor  170 . In the present embodiment, the absolute position sensor  170  is coupled to an end of the fixed shaft  163  and senses absolute positions of the power transfer pins  120 . For example, the absolute positions are misaligned, a control of, for example, forcibly stopping the motion of the external rotor motor portion  160  may be performed. 
     A closing cap  175  for protecting the external rotor motor portion  160  is provided around the external rotor motor portion  160 . The closing cap  175  may protect the external rotor motor portion  160 . When the closing cap  175  is open, a path for maintenance and repair of the external rotor motor portion  160  may be formed. 
     A heat sink  178  for radiating heat generated from the external rotor motor portion  160  is provided around the power transfer pins  120  at an opposite side of the closing cap  175 . 
     The heat sink  178  may have a housing structure in which various control circuits  180  for controlling the power transmission device  100  according to the present embodiment are provided. 
     The control circuits  180  may include a power circuit  181 , a wireless communication circuit  182 , an MCU circuit  183 , and an external rotor motor portion drive circuit  184 . 
     In the present embodiment, the power circuit  181 , the wireless communication circuit  182 , the MCU circuit  183 , and the external rotor motor portion drive circuit  184  are all illustrated to be included, but some of them may be excluded in the application. 
     An air flow space portion  179  for air flow is formed in the heat sink  178  between the external rotor motor portion  160  and the control circuits  180 . The air flow space portion  179  may prevent a phenomenon that the heat generated from the external rotor motor portion  160  is directly transferred to the control circuits  180  and thus the control circuits  180  is damaged. 
     The operation of the power transmission device  100  configured as above is described below. 
     Current is applied to the stator  162  when the power transmission device  100  is assembled as illustrated in  FIG. 2 , that is, to the rack  110 . 
     When current is applied to the stator  162 , a magnetic force is generated according to the Fleming&#39;s law. By alternately changing the polarity of current, the rotor  161  that is a magnet is rotated according to the polarity of induced magnetism. 
     Since the rotor connection body  140  is coupled to the rotor  161 , as the rotor  161  rotates, the rotor connection body  140  rotates together and thus the power transfer pins  120  may be induced to be rotated. 
     Accordingly, as the power transfer pins  120  rotate, each of the power transfer pins  120  is engaged with the rack tooth shape  111  of the rack  110  performing interaction therebetween, and thus the rack  110  may perform a linear motion. 
     According to the power transmission device  100  of the present embodiment having the above structure and operation, since not only the overall height of a device, but also an exterior size thereof may be remarkably reduced, the power transmission device  100  may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts. 
       FIG. 7  illustrates a modified example of the power transfer pin. 
     Unlike the above-described embodiments, a power transfer pin  220  may be applied in a structure of capable of lubricating as illustrated in  FIG. 7 . 
     In other words, a lubricant flow hole  221  in which a lubricant flows in a lengthwise direction of the power transfer pin  220  may be provided in the power transfer pin  220 . 
     A lubricant outlet  222  and a lubricant inlet  223  connected to the lubricant flow hole  221 , through which the lubricant enters or exits, may be provide in a side wall of the power transfer pin  220 . 
     The lubricant outlet  222  and the lubricant inlet  223  may be arranged in opposite directions along a radial direction of the power transfer pin  220  in areas at opposite ends of the lubricant flow hole  221 . Since the present disclosure is not limited thereto, the lubricant outlet  222  and the lubricant inlet  223  may be arranged in the same direction. 
     When the power transfer pin  220  having the above-described lubrication structure is employed, the power transfer pin  220  may be smoothly rotated, which may be helpful for the movement of equipment. 
     According to the present embodiment, even when the power transfer pins  220  are employed, since not only the overall height of a device, but also an exterior size thereof may be remarkably reduced, the power transmission device may be easily applied with no restriction to semiconductor or flat display equipment requiring compact parts. 
     While this inventive concept has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as defined by the appended claims. Therefore, the scope of the inventive concept is defined not by the detailed description of the inventive concept but by the appended claims, and all differences within the scope will be construed as being included in the present inventive concept. 
     INDUSTRIAL APPLICABILITY 
     The power transmission device according to the present inventive concept may be used for various machine tools requiring a rotational motion or a linear motion, industrial machinery, semiconductor or flat display manufacturing facilities, and various kinds of logistics transfer facilities.