Abstract:
An actuator assembly for an electromechanical parking brake greatly reduces vibration and noise of the actuator so that a high-quality vehicle may be realized by removing one of factors causing vibration and noise in the vehicle and greatly improves the easiness of assembly and handling together with attenuating vibration and noise by maximizing the excellent vibration and noise attenuating function by means of modularization which allows the actuator assembly to be handled as a single element.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to an actuator assembly for operating an electromechanical parking brake, and more particularly, to an actuator assembly for an electromechanical parking brake which greatly reduces vibration and noise of an actuator so that a high-quality vehicle may be realized by removing one of factors causing vibration and noise in the vehicle. Further, the present disclosure relates to an actuator assembly for an electromechanical parking brake which may improve the easiness of assembly and handling together with attenuating vibration and noise by maximizing the excellent vibration and noise attenuating function by means of modularization which allows the actuator assembly to be handled as a single element. 
       BACKGROUND OF THE INVENTION 
       [0002]    An actuator of an electromechanical parking brake of a vehicle includes a motor and a power transmission unit for operating a friction pad installed at a caliper of a disc brake assembly during the vehicle parking. 
         [0003]    For example, if a driver pushes a parking brake switch, the rotating force of the motor of the actuator is transmitted to an input shaft of the caliper through a power transmission unit such as a reducing gear. The rotation of the input shaft allows a pressurizing junction sleeve to advance, and the advancing of the pressurizing junction sleeve allows a piston received therein and a caliper housing to move closer to each other, so that two friction pads mounted to the piston and the caliper housing press both sides of the disc so that the disc is restricted not to rotate. 
         [0004]    Patent documents 1 to 3 disclose various examples of the actuator of an electromechanical parking brake. 
         [0005]    A traditional parking brake uses a cable-operating manner in which a driver pulls a cable to operate a friction pad or a brake lining. 
         [0006]    In place of it, existing electromechanical parking brake actuators such as those disclosed in Patent documents 1 to 3 have been adopted to give convenience to a driver since a parking brake is operated by a motor. 
         [0007]    The electromechanical parking brake gives convenience to a driver as described above. However, since a device of a new type is mounted, a vehicle designer encounters unfamiliar vibration and noise caused by the device. For this reason, a high-quality vehicle which winds the confidence of drivers may be provided when a study for regulating or removing such vibration and noise is accompanied. 
         [0008]    For example, in an actuator for an electromechanical parking brake, the rotating force of a motor is transmitted to a planetary gear set through a power transmission gear or a power transmission belt, and the input shaft of a caliper rotates by the rotation of the output shaft of the planetary gear set. 
         [0009]    In this power transmission process, together with vibration and noise caused by the operating motor, there are generated vibration, noise and strange sound due to collision, friction or backlash between gear teeth surfaces, which are also propagated out of the housing. 
         [0010]    In addition, if the parking brake is not in operation, the vibration generated by an engine of a vehicle may be transferred to an actuator housing and cause resonance. The resonance of the actuator housing is harsh to the ear and may also be propagated to other surrounding elements to cause an unusual noise not experienced before. 
         [0011]    Meanwhile, in order to improve convenience in assembly or supply of components or in order to reduce costs or improve productivity in this connection, a so-called ‘modularized’ manufacturing method in which various components are assembled in a sub-assembly form in advance to be handled as a single element is recently introduced to a vehicle. 
         [0012]    If the parking brake actuator is modularized, a motor and a power transmission unit may be supplied as a single assembled module and thus they need not be newly assembled in a vehicle manufacturing factory. Therefore, this may give various advantages such as simplifying the vehicle assembling process and facilitating easier supply and management of components. 
         [0013]    However, as another purpose for modularizing the actuator, the processes of producing and assembling actuator components may be entrusted to a specialized company so that the study for improving quality may be intensively performed. 
         [0014]    The quality of the actuator naturally includes the quality in relation to vibration and noise as described above. Therefore, the study for minimizing vibration and noise and the study for designing a structure for modularization should be performed together and harmonized. 
       RELATED LITERATURES 
     Patent Document 
       [0000]    
       
         (Patent document 0001) Korean Patent Application Publication No. 10-2011-0093061 
         (Patent document 0002) Korean Patent Application Publication No. 10-2011-0011038 
         (Patent document 0003) Korean Patent Publication No. 10-0819087 
       
     
       SUMMARY OF THE INVENTION 
       [0018]    The present disclosure is directed to implementing a high-quality vehicle by greatly decreasing vibration and noise of an actuator for an electromechanical parking brake so that one of factors causing vibration and noise of a vehicle is removed. 
         [0019]    Further, the present disclosure is directed to improving a vibration and noise attenuating function by modularizing an actuator assembly so that two design concepts may be mutually supplemented and enhanced. 
         [0020]    In one aspect, there is provided an actuator assembly for an electromechanical parking brake, wherein a casing of a motor and a gear housing of a planetary gear set are coupled to a lower surface of an inner housing in parallel, a reduction gear train having a pinion gear and a drive gear for transmitting a power from a rotary shaft of the motor to the planetary gear set is received in an upper surface of the inner housing, and an inner cap covering the outer portion of the reduction gear train is coupled to the upper surface of the inner housing, thereby configuring a primary module which is a single small independent assembly in which the motor, the reduction gear train, the planetary gear set, the inner housing and the inner cap are combined; wherein the primary module is inserted into an outer housing while keeping a gap at a circumference thereof, an outer cap is coupled to an upper portion of the outer housing to cover the primary module, and the primary module is surrounded by the outer housing and the outer cap, thereby configuring a final module which is a single large independent assembly in which inner components of the motor, the reduction gear train and the planetary gear set are surrounded doubly; and wherein a final output shaft of the planetary gear set is exposed from a lower through hole of the outer housing and connected to a parking brake. 
         [0021]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, the outer housing may have a bottom portion on which the lower surface of the inner housing is placed and a circumferential wall extending upwards at the circumference of the bottom portion to hide a side of the primary module, and a vibration-attenuating damper member may be installed in a space between a rim portion of the inner housing and the circumferential wall of the outer housing. 
         [0022]    The damper member may have a coupling groove formed in a circumferential inner wall thereof, and a rim portion of the inner housing may be fit into the coupling groove. 
         [0023]    The damper member may be assembled below the primary module to face upwards, a bottom portion may be formed at a lower end of the rim portion to closely adhere to the lower surface of the inner housing, and openings may be formed in the bottom portion to allow the casing of the motor and the gear housing of the planetary gear set to pass through. 
         [0024]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, the damper member may be made of an elastic flexible material, and an outer circumference thereof closely adhering to the inner side of the circumferential wall of the outer housing may have an uneven portion. 
         [0025]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, the outer housing may include a motor receiver extending downwards from the bottom portion and having a closed circumference and a closed bottom to accommodate the casing of the motor, and a planetary gear receiver extending downwards from the bottom portion and having a closed circumference and an open bottom to accommodate the gear housing of the planetary gear set. 
         [0026]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a vibration and noise attenuating pad may be interposed between the outer circumference of the casing of the motor and the inner circumference of the outer housing. 
         [0027]    The vibration and noise attenuating pad may be made of non-woven fabric, fiber, or pulp material. 
         [0028]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a vibration-attenuating and gap-maintaining elastic ring may be interposed between an end surface of the casing of the motor and a bottom surface of the outer housing. 
         [0029]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a shaft support for supporting the rotary shaft may protrude and extend from the lower portion of the casing of the motor, an accommodating unit for accommodating the shaft support may protrude and extend from the bottom of the outer housing, and a vibration-attenuating and gap-maintaining elastic ring for supporting the shaft support and the accommodating unit to keep a gap with each other in an axial direction and in a radial direction may be installed in a space between the shaft support and the accommodating unit. 
         [0030]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a snap-fit strip having a coupling protrusion may extend at an end of one of the inner cap and inner housing toward the other thereof, and a snap-fit groove may be formed at the other thereof so that the snap-fit strip is inserted thereto and the coupling protrusion is hooked thereto. 
         [0031]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, the inner housing may include a bottom portion having a rim portion at an outer circumference thereof and a first noise dam extending to surround a periphery of the reduction gear train having the pinion gear and the drive gear installed at the upper surface of the bottom portion, the inner cap may have a second noise dam corresponding to a circumferential contour of the first noise dam, and end surfaces of the first and second noise dams may closely adhere to each other to prevent an operation noise generated from the reduction gear train therein from being propagated outwards. 
         [0032]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a dowel plate for determining an assembling location may extend from one of the inner cap and the inner housing toward the other thereof, and a positioning groove may be formed in the other thereof so that the dowel plate is inserted thereto to take the position thereof. 
         [0033]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a snap-fit strip having a snap-fit hole may extend from one of the lower surface of the inner housing and the gear housing of the planetary gear set toward the other thereof, and a snap-fit protrusion may be formed at the other thereof so that the snap-fit hole of the snap-fit strip is inserted and hooked thereto. 
         [0034]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a skirt section may extend from the lower surface of the inner housing so that the gear housing of the planetary gear set is inserted thereto, and the gear housing of the planetary gear set may be inserted into the skirt section and snap-fit thereto. 
         [0035]    A snap-fit strip having a snap-fit hole may extend from a skirt section of the inner housing, and a snap-fit protrusion may be formed at the outer circumferential surface of the gear housing of the planetary gear set to be inserted into and hooked by the snap-fit hole of the snap-fit strip. 
         [0036]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, a positioning groove for determining an assembling location of the gear housing of the planetary gear set may be formed at the skirt section of the inner housing, and a positioning protrusion may be formed at the outer circumferential surface of the gear housing of the planetary gear set to be inserted into the positioning groove to take the position thereof. 
         [0037]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, an outer terminal for supplying a power to the motor may include a horizontal portion connected to an outer connector, and a bent portion bent and extending from the horizontal portion, a terminal strip of the motor may include a bent portion closely adhering to the bent portion of the outer terminal in a surface-to-surface relation, and the bent portion of the outer terminal and the bent portion of the terminal strip may be joined by welding. 
         [0038]    A part of the outer terminal, which includes the horizontal portion, may be integrated with the outer housing by means of insert injection molding. 
         [0039]    In the actuator assembly for an electromechanical parking brake according to the present disclosure, the reduction gear train including the pinion gear and the drive gear may be made of a plastic injection molding product and may be configured with a helical gear. 
         [0040]    If the actuator assembly for an electromechanical parking brake according to the present disclosure is used, vibration and noise may be reduced since a motor and a power transmission unit are received and assembled in a single inner housing, and the inner housing is also accommodated in an outer housing to attenuate the vibration and noise, thereby greatly decreasing the propagation of vibration and noise to the outside. 
         [0041]    In addition, since vibration and noise is attenuated by the housing structure of the inner housing and the outer housing, the assembled structure of the inner housing and the outer housing and the assembled structure of the motor and the outer housing to the minimum, the propagation of vibration and noise to the outside may be minimized. 
         [0042]    Moreover, since a power supply connector is closely adhered to perform surface contact and then welded to prevent vibration and short circuit, it is possible to elongate the life span of the connector link and ensure easier assembling. 
         [0043]    In addition, the motor and the power transmission unit are primarily modularized together with the inner housing, which is also finally modularized with the outer housing, and also the vibration and noise attenuating structures are appropriately combined. By doing so, complex and synergistic effects of improving the quality of the overall actuator, reducing vibration and noise, and improving assembling and productivity may be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]    The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0045]      FIG. 1  is a perspective view showing a parking brake actuator assembly according to the present disclosure, observed from the above; 
           [0046]      FIG. 2  is a perspective view showing the parking brake actuator assembly according to the present disclosure, observed from the below; 
           [0047]      FIG. 3  is an exploded perspective view showing an overall parking brake actuator according to the present disclosure, observed from the above; 
           [0048]      FIG. 4  is an exploded perspective view showing the overall parking brake actuator according to the present disclosure, observed from the below; 
           [0049]      FIG. 5  is an exploded perspective view for illustrating an assembling process and a state of a primary module of the parking brake actuator according to the present disclosure; 
           [0050]      FIG. 6  is an exploded perspective view showing an assembled state of the primary module of the parking brake actuator according to the present disclosure; 
           [0051]      FIG. 7  is a perspective view of  FIG. 6 , observed from the below; 
           [0052]      FIG. 8  is an exploded perspective view showing the primary module of the actuator according to the present disclosure, which is assembled to an outer housing; 
           [0053]      FIG. 9  is a front sectional view showing the actuator according to the present disclosure, for illustrating a vibration and noise attenuating structure of the primary module and the outer housing; 
           [0054]      FIG. 10  is a sectional view, taken along the line A-A of  FIG. 9 ; 
           [0055]      FIG. 11  is a sectional view, taken along the line B-B of  FIG. 9 ; 
           [0056]      FIG. 12  is a perspective view for illustrating an assembled structure of an inner housing employed in the primary module of the actuator according to the present disclosure; 
           [0057]      FIG. 13  is a perspective view showing that the inner housing of  FIG. 12  is coupled to a cap; 
           [0058]      FIG. 14  is a front sectional view of  FIG. 13 ; 
           [0059]      FIG. 15  is a cross-sectional view of  FIG. 13 ; 
           [0060]      FIG. 16  is a perspective view for illustrating an assembled structure of the inner housing and the planetary gear set of the actuator according to the present disclosure; 
           [0061]      FIG. 17  is a sectional view showing a coupled state of the inner housing and the planetary gear set of  FIG. 16 ; 
           [0062]      FIG. 18  is a sectional view showing an essential part of a terminal connection structure of the actuator according to the present disclosure; and 
           [0063]      FIG. 19  is a perspective view showing an essential part of the terminal connection structure of the actuator according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0064]    Hereinafter, an actuator assembly for an electromechanical parking brake according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. 
         [0065]    Terms used in this specification are to illustrate embodiments and not intended to limit the present disclosure. 
         [0066]    In addition, spatially relative terms such as “below”, “beneath”, “lower”, “above”, “upper”, “bottom”, “ceiling” or the like may be used to explain correlations among components more easily as shown in the drawings. It should be understood that the spatially relative terms may include other directions of components in use or in operation in addition to those depicted in the drawings. For example, when a component depicted on a drawing is turned over, a component described as being “below” or “beneath” another component may be placed “above” the corresponding component. 
         [0067]      FIG. 1  is a perspective view showing a parking brake actuator assembly according to the present disclosure, observed from the above. FIG.  2  is a perspective view showing the parking brake actuator assembly according to the present disclosure, observed from the below. 
         [0068]    Referring to  FIGS. 1 and 2 , in a completed state, an actuator assembly is composed of a final module  50  which is a single large assembly. The final module  50  accommodates a primary module in which a motor, a reduction gear train and a planetary gear set for operating a parking brake are assembled to configure a single small independent assembly. 
         [0069]    The contour of the final module  50  is shaped to be surrounded by an outer housing  210  and an outer cap  220 . 
         [0070]    A junction sleeve  215  is provided at one side of the outer housing  210  to connect an external power connector. The motor is received in a motor receiver  213  of the outer housing  210 . A terminal connected to a connector to apply a current to the motor is installed in the junction sleeve  215 . 
         [0071]    A lower through hole  214   a  is formed in the other side of the outer housing  210 , namely in the lower portion of the planetary gear receiver  214 . A final output shaft  176  of the planetary gear set exposes through the lower through hole  214   a . A parking brake is connected to the final output shaft  176 . For example, an input shaft of a caliper of a disc-type parking brake is coupled to the final output shaft  176 . 
         [0072]    The actuator assembly of the present disclosure includes the primary module which is a single small assembly in which the motor, the reduction gear train, the planetary gear set, the inner housing and the inner cap are combined, and the primary module is accommodated again in the outer housing  210  and the outer cap  220 . Therefore, by using the structure in which inner components of the motor, the reduction gear train and the planetary gear set are surrounded by a double wall barrier or double wall noise dams, it is possible to attenuate vibration and noise and thus minimize propagation of the vibration and noise inwards or outwards. 
         [0073]    In addition, by combining the actuator assembly with the final module  50  which is a unit element for handling, the above vibration and noise attenuating function may give a synergistic effect, for example improvement in assembling and productivity. 
         [0074]    Hereinafter, a detailed embodiment of the actuator assembly of the present disclosure, namely the final module  50 , will be described. 
         [0075]      FIG. 3  is an exploded perspective view showing an overall parking brake actuator according to the present disclosure, observed from the above.  FIG. 4  is an exploded perspective view showing the overall parking brake actuator according to the present disclosure, observed from the below. 
         [0076]    Referring to  FIGS. 3 and 4 , a primary module  100  is configured by assembling an inner housing  110 , a motor  130 , a reduction gear train composed of a pinion gear  140 , an idle gear  150  and a drive gear  160 , a planetary gear set  170 , and an inner cap  120 . 
         [0077]    The assembled primary module  100  is inserted into the outer housing  210  and the outer cap  220  together with a vibration and noise attenuating pad  136 , a vibration-attenuating and gap-maintaining elastic ring  137  and a vibration-attenuating damper member  190 . 
         [0078]    A rotary shaft  131 , a terminal strip  133  and a coupling boss  134  are provided at the upper surface of the motor  130 . The pinion gear  140  is coupled to the rotary shaft  131 . 
         [0079]    A mount surface  114  closely adhering to the upper surface of the motor  130 , a through hole  115  for allowing the pinion gear  140  of the motor  130  to pass, and a coupling hole  116  for the insertion of the coupling boss  134  are formed at the inner housing  110 . 
         [0080]    The upper surface of the motor  130  closely adheres to the mount surface  114  of the inner housing  110 , the pinion gear  140  passes through the through hole  115  and protrudes on the upper surface of the inner housing  110 , and the coupling boss  134  is inserted into the coupling hole  116  and coupled by a screw  125  to be fixed to the inner housing  110 . 
         [0081]    The inner housing  110  has a bottom portion  111 . The outer circumference of the bottom portion  111  forms a rim portion  112 . A reduction gear train for transmitting a power of the pinion gear  140  to the planetary gear set  170  is installed at the upper surface of the inner housing  110 . 
         [0082]    The reduction gear train includes a drive gear  160  for receiving the rotating force of the pinion gear  140  to drive the planetary gear set  170 , and may additionally include an idle gear  150  between the pinion gear  140  and the drive gear  160 . The pinion gear  140 , the idle gear  150  and the drive gear  160  may be produced by injection-molding plastic material in order to reduce vibration and noise. In order to further improve the vibration and noise characteristics, a helical gear may be used instead of a general spur gear. 
         [0083]    The reduction gear train including the pinion gear  140 , the idle gear  150  and the drive gear  160  is installed on the upper surface of the inner housing  110  so that they are engaged while circumscribing with the central axes being arranged in parallel. 
         [0084]    The drive gear  160  is configured as a single body having an input gear  161  engaged with the idle gear  150  and a first sun gear  162  for driving the planetary gear set  170 . 
         [0085]    The planetary gear set  170  is a complex planetary gear set configured in two stages, and the planetary gear set  170  reduces the rotation input from the drive gear  160  through two stages and then drives the parking brake. 
         [0086]    The planetary gear set  170  includes a gear housing  180 , which has a plurality of first pinion gears  171  engaged with the first sun gear  162  of the drive gear  160 , a first carrier  172  for connecting the plurality of first pinion gears  171 , a second sun gear  173  integrally formed at the first carrier  172 , a plurality of second pinion gears  174  engaged with the second sun gear  173 , a second carrier  175  for connecting the plurality of second pinion gears  174 , a final output shaft  176  integrally formed at the second carrier  175 , and an internal gear  181  inscribed with the first pinion gear  171  and the second pinion gear  174  and protects the entire planetary gear set  170 . The gear housing  180  is fixed to the inner housing  110  not to rotate. 
         [0087]    The planetary gear set  170  is mounted to the inner housing  110  in parallel to the motor  130 . 
         [0088]    The planetary gear set  170  is snap-fit to the inner housing  110 . For this, a skirt section  117  extends from the lower surface of the inner housing  110 , and the gear housing  180  of the planetary gear set  170  is simply assembled to the skirt section  117  by means of snap-fitting. The snap-fitting of the gear housing  180  will be described later in detail. 
         [0089]    In addition, the inner housing  110  includes a first noise dam  113  extending upwards to surround the outer periphery of the reduction gear train installed at the upper surface of the bottom portion  111 . Therefore, the periphery of the reduction gear train including the pinion gear  140 , the idle gear  150  and the drive gear  160  is hidden and blocked by the first noise dam  113 . 
         [0090]    The inner cap  120  includes a second noise dam  120   a  which is shaped corresponding to the periphery contour of the first noise dam  113 . Since the end surfaces of the first and second noise dams  113 ,  120   a  closely adhere to each other, the reduction gear train therein is covered by the first and second noise dams  113 ,  120   a , thereby intercepting the propagation of operation noise of the reduction gear train to the outside. 
         [0091]    If the bottom portion  111  of the inner housing  110  and the ceiling surface  123  of the inner cap  120  are formed unevenly to have a lattice shape as shown in the figures, the soundproof or sound-isolating function may be enhanced. 
         [0092]    The outer housing  210  has a bottom portion  211  on which the lower surface of the inner housing  110  is placed. A circumferential wall  212  is formed above the bottom portion  211  to accommodate the inner housing  110 . A motor receiver  213  for receiving the casing  132  of the motor  130  and a planetary gear receiver  214  for receiving the gear housing  180  of the planetary gear set  170  are provided below the bottom portion  211 . 
         [0093]    The motor receiver  213  has a closed circumference and a closed bottom in order to block the circumference and bottom of the casing  132  of the motor  130 . In addition, the planetary gear receiver  214  has a closed circumference and an open bottom in order to block the circumference of the gear housing  180  of the planetary gear set  170  and draw the final output shaft  176 . 
         [0094]    A junction sleeve  215  for connecting an external power supply connector is formed at one side of the outer housing  210  in order to supply a power to the motor  130 . The motor is received in the motor receiver  213  of the outer housing  210 . An outer terminal  216  connected to an outer connector is installed in the junction sleeve  215 . 
         [0095]    The vibration-attenuating damper member  190  is installed in a space between the rim portion  112  of the inner housing  110  and the circumferential wall  212  of the outer housing  210 . By means of the vibration-attenuating damper member  190 , it is possible to attenuate or block the vibration and noise propagating between the inner housing  110  and the outer housing  210 . 
         [0096]    In addition, the vibration and noise attenuating pad  136  is interposed between the outer circumference of the casing  132  of the motor  130  and the inner circumference of the outer housing  210 . In addition, the vibration-attenuating and gap-maintaining elastic ring  137  is interposed between an end surface  132   b  of the casing  132  of the motor  130  and the bottom surface of the outer housing  210 . 
         [0097]    The vibration and noise attenuating pad  136  and the elastic ring  137  may be assembled with the motor  130  in advance to configure the primary module  100 . 
         [0098]      FIG. 5  is an exploded perspective view for illustrating an assembling process and a state of a primary module of the parking brake actuator according to the present disclosure.  FIG. 6  is an exploded perspective view showing an assembled state of the primary module of the parking brake actuator according to the present disclosure.  FIG. 7  is a perspective view of  FIG. 6 , observed from the below. 
         [0099]    Referring to  FIG. 5 , when assembling the primary module  100 , the reduction gear train including the pinion gear  140 , the idle gear  150  and the drive gear  160  is installed in the first noise dam  113  formed at the upper portion of the bottom surface  111  of the inner housing  110 . 
         [0100]    Referring to  FIG. 6  together with  FIG. 5 , the upper surface of the motor  130  closely adheres to the mount surface  114  (see  FIG. 4 ) of the inner housing  110 , the pinion gear  140  of the motor  130  passes through the through hole  115 , and the coupling boss  134  is inserted into the coupling hole  116 . Subsequently, the screw  125  is coupled to fix the coupling boss  134 . 
         [0101]    The gear housing  180  of the planetary gear set  170  is assembled to the skirt section  117  of the inner housing  110  by means of snap-fitting. 
         [0102]    The vibration and noise attenuating pad  136  and the vibration-attenuating and gap-maintaining elastic ring  137  may be inserted into the casing  132  of the motor  130  to serve as a component of the primary module  50  (see  FIGS. 5 and 7 ). 
         [0103]    The inner housing  110  includes the first noise dam  113  extending upwards to surround the periphery of the reduction gear train installed at the upper surface of the bottom portion  111 . Therefore, the periphery of the reduction gear train including the pinion gear  140 , the idle gear  150  and the drive gear  160  is hidden and blocked by the first noise dam  113 . 
         [0104]    The inner cap  120  is coupled by closely adhering the end surface of its second noise dam  120   a  to the end surface of the first noise dam  113  of the inner housing  110 . By doing so, the reduction gear train is covered by the first and second noise dams  113 ,  120   a  to block the propagation of operation noise of the reduction gear train to the outside. 
         [0105]    Referring to  FIG. 7 , the primary module  100  is configured as an assembly in which the inner housing  110 , the motor  130 , the reduction gear train, the planetary gear set  170 , the inner cap  120 , the vibration and noise attenuating pad  136  and the elastic ring  137  are combined as a single unit. 
         [0106]    In addition, the primary module  100  may be assembled as a single unit together with the vibration-attenuating damper member  190 . 
         [0107]    The vibration-attenuating damper member  190  is made of an elastic flexible material, for example a rubber with elasticity such as ethylene propylene diene monomer (EPDM). 
         [0108]    The outer circumference of the vibration-attenuating damper member  190  has an uneven portion  191 , and the uneven portion  191  closely adheres to the inner surface of the circumferential wall  212  of the outer housing  210  to enhance the vibration and noise attenuating function. 
         [0109]    In addition, the vibration-attenuating damper member  190  has a coupling groove  192  formed in the circumferential inner wall, and the rim portion  112  of the inner housing  110  is fit into the coupling groove  192 . 
         [0110]    Moreover, in order to assemble the vibration-attenuating damper member  190  from a lower portion of the primary module  100  upwards, a bottom portion  193  closely adhering to the lower surface of the inner housing  110  is formed at the lower end of the rim portion  112 , and openings  194 ,  195  are formed in the bottom portion  193  to allow the casing  132  of the motor  130  and the gear housing  180  of the planetary gear set  170  to pass through. 
         [0111]    The primary module  100  configured as above is inserted into the outer housing  210 , and finally the outer cap  220  is coupled thereto to completely make the final module  50  which is an actuator assembly. 
         [0112]    If the surface of the ceiling surface  223  in the outer cap  220  is formed unevenly to have a lattice shape as shown in  FIG. 7 , the soundproof or sound-isolating function may be enhanced. 
         [0113]    In addition, the outer cap  220  may have an inner wall  221  and an outer wall  222  which surround an inside and an outside of the circumferential wall  212  of the outer housing  210 . 
         [0114]    The inner wall  221  and the outer wall  222  of the outer cap  220  are closely adhered to the inner side and the outside of the circumferential wall  212  of the outer housing  210  by fitting and then joined thereto by ultrasonic welding, vibration welding or thermal welding. 
         [0115]      FIG. 8  is an exploded perspective view showing the primary module of the actuator according to the present disclosure, which is assembled to an outer housing. 
         [0116]    Referring to  FIGS. 7 and 8 , if the primary module  100  is inserted into the outer housing  210 , the vibration-attenuating damper member  190  is interposed between the rim portion  112  of the inner housing  110  and the inner surface of the circumferential wall  212  of the outer housing  210  to maintain a gap between them. In addition, the vibration and noise attenuating pad  136  is interposed between the outer circumference of the motor  130  and the inner wall of the motor receiver  213  to maintain a gap between them. Moreover, the vibration-attenuating and gap-maintaining elastic ring  137  is interposed between the lower end of the motor  130  and the accommodating unit  213   a  of the motor receiver  213  to maintain a gap between them. 
         [0117]      FIG. 9  is a front sectional view showing the actuator according to the present disclosure, for illustrating a vibration and noise attenuating structure of the primary module and the outer housing.  FIG. 10  is a sectional view, taken along the line A-A of  FIG. 9 .  FIG. 11  is a sectional view, taken along the line B-B of  FIG. 9 . 
         [0118]    Referring to  FIGS. 9 and 10 , the vibration and noise attenuating pad  136  is interposed between the outer circumference of the casing  132  of the motor  130  and the inner circumference of the outer housing  210 . 
         [0119]    The vibration and noise attenuating pad  136  is made of non-woven fabric, fiber, or pulp material and attenuates vibration and noise transferred between the motor  130  and the outer housing  210 . 
         [0120]    In addition, a shaft support  132   a  (see  FIG. 7  together) for supporting the rotary shaft  131  protrudes from the lower portion of the casing  132  of the motor  130 , an accommodating unit  213   a  (see  FIG. 7  together) for accommodating the shaft support  132   a  protrudes from the bottom of the outer housing  210 , and the vibration-attenuating and gap-maintaining elastic ring  137  is installed in a space between the shaft support  132   a  and the accommodating unit  213   a.    
         [0121]    The elastic ring  137  may be made of an elastic flexible material, for example a rubber with elasticity such as EPDM. 
         [0122]    The elastic ring  137  attenuates vibration and noise and prevents propagation of the vibration and noise while maintaining the gap between the outer circumference of the shaft support  132   a  and the inner circumference of the accommodating unit  213   a  in a radial direction, and also attenuates vibration and noise and prevents propagation of the vibration and noise while maintaining the gap between the end surface  132   b  of the casing  132  of the motor  130  and the bottom surface of the outer housing  210 . 
         [0123]      FIG. 11  is a sectional view, taken along the line B-B of  FIG. 9  and shows an installed state of the vibration-attenuating damper  190 .  FIG. 9  is also referred to together. 
         [0124]    Referring to  FIGS. 9 and 11 , the coupling groove  192  of the vibration-attenuating damper  190  is coupled to the rim portion  112  of the inner housing  110 . The vibration-attenuating damper member  190  attenuates vibration transferred between the inner housing  110  and the outer housing  210  while maintaining a gap between the rim portion  112  of the inner housing  110  and the circumferential wall  212  of the outer housing  210 . The vibration attenuating function is enhanced by the uneven portion  191  formed at the outer surface of the vibration-attenuating damper  190 . 
         [0125]      FIG. 12  is a perspective view for illustrating an assembled structure of an inner housing employed in the primary module of the actuator according to the present disclosure.  FIG. 13  is a perspective view showing that the inner housing of  FIG. 12  is coupled to a cap.  FIG. 14  is a front sectional view of  FIG. 13 .  FIG. 15  is a cross-sectional view of  FIG. 13 . 
         [0126]    As shown in  FIGS. 12 to 15 , a snap-fit strip  121  having a coupling protrusion  121   a  extends from an end of one of the inner cap  120  and the inner housing  110  (the inner cap  120  in the figures) toward the other thereof, and a snap-fit groove  112   a  is formed at the other thereof (the inner housing  110  in the figures) so that the snap-fit strip  121  is inserted thereto and the coupling protrusion  121   a  is hooked thereto. 
         [0127]    In addition, a dowel plate  122  for determining an assembling point extends from one of the inner cap  120  and the inner housing  110  (the inner cap  120  in the figures) toward the other thereof, and a positioning groove  112   b  is formed at the other thereof (the inner housing  110  in the figures) so that the dowel plate  122  is inserted thereto to take the position thereof. 
         [0128]    Therefore, if the inner cap  120  is coupled to the inner housing  110 , the dowel plate  122  is inserted into the positioning groove  112   b  to take the position thereof, and the coupling protrusion  121   a  of the snap-fit strip  121  is hooked and fixed to the snap-fit groove  112   a.    
         [0129]    As described above, the inner housing  110  and the inner cap  120  are easily and conveniently assembled by means of snap-fitting. Therefore, the primary module  100  may be assembled very easily. 
         [0130]      FIG. 16  is a perspective view for illustrating an assembled structure of the inner housing  110  and the planetary gear set  170  of the actuator according to the present disclosure.  FIG. 17  is a sectional view showing a coupled state of the inner housing  110  and the planetary gear set  170  of  FIG. 16 . 
         [0131]    Referring to  FIGS. 16 and 17 , a snap-fit strip  117   a  having a snap-fit hole  117   b  extends from one of the lower surface of the inner housing  110  and the gear housing  180  of the planetary gear set  170  (the inner housing  110  in the figures) toward the other thereof, and a snap-fit protrusion  182  is formed at the other thereof (the gear housing  180  in the figures) so that the snap-fit hole  117   b  of the snap-fit strip  117   a  is inserted and hooked thereto. 
         [0132]    In order to easily form the snap-fit strip  117   a  and firmly couple the gear housing  180 , the skirt section  117  extends from the lower surface of the inner housing  110  so that the gear housing  180  of the planetary gear set  170  is inserted thereto. Therefore, the gear housing  180  of the planetary gear set  170  is inserted into the skirt section  117  and snap-fit thereto. 
         [0133]    When the skirt section  117  is provided (in the embodiment depicted in the figures), the snap-fit strip  117   a  extends from the skirt section  117 . 
         [0134]    In other words, the snap-fit strip  117   a  having the snap-fit hole  117   b  extends from the skirt section  117  of the inner housing  110 , and the snap-fit protrusion  182  is formed on the outer circumferential surface of the gear housing  180  of the planetary gear set  170  so as to be inserted and hooked to the snap-fit hole  117   b  of the snap-fit strip  117   a.    
         [0135]    Meanwhile, a positioning groove  117   c  for determining an assembling location of the gear housing  180  of the planetary gear set  170  is formed in the skirt section  117  of the inner housing  110 , and a positioning protrusion  183  inserted into the positioning groove  117   c  to take the position thereof is formed at the outer circumferential surface of the gear housing  180  of the planetary gear set  170 . 
         [0136]    Therefore, if the gear housing  180  of the planetary gear set  170  is coupled to the inner housing  110 , the positioning protrusion  183  is inserted into the positioning groove  117   c  to take the position thereof, and the snap-fit protrusion  182  is inserted and hooked to the snap-fit hole  117   b  of the snap-fit strip  117   a.    
         [0137]    As described above, the gear housing  180  of the planetary gear set  170  and the inner housing  110  are assembled easily and conveniently by means of snap-fitting. Therefore, the primary module  100  may be assembled very easily. 
         [0138]      FIGS. 18 and 19  are diagrams for illustrating a terminal connecting structure of the actuator according to the present disclosure. FIG.  18  is a sectional view of an essential part, and  FIG. 19  is a perspective view of an essential part. 
         [0139]    Referring to  FIGS. 18 and 19 , the outer terminal  216  for supplying power to the motor  130  includes a horizontal portion  216   a  connected to an outer connector and a bent portion  216   b  bent and extending from the horizontal portion  216   a.    
         [0140]    Along with it, the terminal strip  133  of the motor  130  has a bent portion  133   b  corresponding to the bent portion  216   b  of the outer terminal  216 . 
         [0141]    The bent portion  216   b  of the outer terminal  216  and the terminal strip  133  of the motor  130  are adhered in a surface-to-surface relation and joined to each other by a welding portion w 1 . 
         [0142]    In a general terminal connecting structure, the outer terminal  216  and the terminal strip  133  are connected using a wire while maintaining a certain gap, which may be short-circuited or cause unstable electric connection due to vibration of a vehicle. In addition, noise may also be generated by a shaking wiper due to vibration of a vehicle engine. 
         [0143]    In the present disclosure, since the outer terminal  216  and the terminal strip  133  are adhered in a surface-to-surface relation and joined by welding, the influence of noise is reduced, and short-circuiting is prevented, thereby improving durability and noise characteristics. 
         [0144]    Further, a part of the outer terminal  216  including the horizontal portion  216   a  may be integrated with the outer housing  210  by means of insert injection molding. 
         [0145]    By doing so, the final module  50  serving as an actuator assembly may be assembled more conveniently. 
         [0146]    The exemplary embodiments of the present disclosure have been shown and described. However, the present disclosure is not limited thereto, and it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of the present disclosure as defined by the appended claims.