Abstract:
An electric actuator, which includes an exposed actuator terminal, for eliminating the need for insert molding and facilitating the manufacturing of a housing while preventing liquid from entering the housing. The actuator includes a motor. The housing is attached to the motor and includes an opening. A control circuit board accommodated in the housing controls the motor. An actuator terminal is arranged on the control circuit board and connected to an external terminal of an external connector through the opening. A terminal support arranged on the control circuit board supports the actuator terminal. A hollow fitting is attached to the terminal support and fitted into the opening so as to extend into the housing. A seal, arranged between the terminal support and the fitting, seals the housing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an electric actuator including a reduction gear and a control circuit board.  
         [0002]     In the prior art, an electric actuator for a power window device includes a motor and a housing. The motor has a rotary shaft. The housing houses a reduction gear, which reduces the rotation speed of the rotary shaft. Japanese Laid-Open Patent Publication No. 2000-220344 describes an electric actuator having an actuator terminal, which may be connected to an external terminal such as a power supply. The actuator terminal is insert-molded with the housing so that the end of the terminal is exposed from the housing. In such an electric actuator, the insert-molded actuator terminal is exposed only at its end. Thus, there is no gap formed between the inside and outside of the housing. This prevents liquids, such as moisture, from entering the housing.  
         [0003]     U.S. Pat. No. 5,245,258 describes another type of electric actuator including a housing that houses a control circuit board. The circuit board is arranged in a circuit board compartment. In addition to electric circuit components, an actuator terminal is arranged on the control circuit board. In such an electric actuator, insert molding is not performed. This facilitates the manufacturing of the housing.  
         [0004]     In the electric actuator of U.S. Pat. No. 5,245,258, the housing must have an opening to expose the actuator terminal, which is arranged on the control circuit board, from the housing. However, if a gap is formed between the actuator terminal and the wall defining the opening, liquid may enter the housing and reach the circuit board compartment. This may damage the electric circuit components and motor.  
       SUMMARY OF THE INVENTION  
       [0005]     It is an object of the present invention to provide an electric actuator, which includes an exposed actuator terminal, for eliminating the need for insert molding and facilitating the manufacturing of a housing while preventing liquid from entering the housing.  
         [0006]     One aspect of the present invention is an electric actuator for connection to an external terminal of an external connector. The electric actuator is provided with a motor including a rotary shaft. A housing is attached to the motor and includes an opening. A control circuit board is accommodated in the housing to control the motor. An actuator terminal is arranged on the control circuit board and connectable to the external terminal of the external connector through the opening. A terminal support is arranged on the control circuit board to support the actuator terminal. A hollow fitting is attached to the terminal support and fitted into the opening so as to extend into the housing. A seal is arranged between the terminal support and the fitting to seal the housing.  
         [0007]     Another aspect of the present invention is an electric actuator for connection to an external terminal of an external connector. The electric actuator is provided with a motor including a rotary shaft. A housing, attached to the motor and including an opening, accommodates a reduction gear mechanism for reducing rotation speed of the rotary shaft of the motor. A control circuit board is accommodated in the housing for controlling the motor. An actuator terminal is arranged on the control circuit board and connectable to the external terminal of the external connector through the opening. A terminal support is arranged on the control circuit board to support the actuator terminal. The terminal support includes a support flange extending around the external terminal. A hollow fitting is attached to the terminal support and fitted into the opening so as to extend into the housing. A seal is arranged between the support flange and the fitting to seal the housing.  
         [0008]     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
         [0010]      FIG. 1  is a plan view showing an electric actuator according to a preferred embodiment of the present invention;  
         [0011]      FIG. 2  is a partially exploded plan view showing the electric actuator of  FIG. 1 ;  
         [0012]      FIG. 3  is a cross-sectional view taken along line III-III in  FIG. 1 ; and  
         [0013]      FIG. 4  is a cross-sectional view taken along line IV-IV in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     An electric actuator  1  according to a preferred embodiment of the present invention will now be described with reference to FIGS.  1  to  4 . Referring to  FIGS. 1 and 2 , the electric actuator  1  includes a motor  2  and a reduction gear mechanism  3 .  
         [0015]     The motor  2  has a yoke  4 , which is generally cylindrical but has two opposed flat surfaces  4   a . The yoke  4  has a cavity for housing two magnets  5 , a rotatable armature  6 , and a brush holder  7  (see  FIG. 2 ). The magnets  5  are fixed to the surface of the yoke  4  in the cavity. The rotatable armature  6  includes a rotary shaft  6   a . The brush holder  7  holds two brushes (not shown).  
         [0016]     Referring to  FIG. 2 , the brush holder  7  is made of a resin material and includes a brush support  7   a  and a terminal support  7   b , which are formed integrally with each other. The brush support  7   a  holds the brushes in the cavity of the yoke  4 , and the terminal support  7   b  extends axially from the cavity of the yoke  4 . The terminal support  7   b  is located sideward (toward the left as viewed in  FIG. 2 ) from the rotary shaft  6   a . A plurality of terminals are insert-molded with the brush holder  7 . The terminals have basal portions, electrically connected to the brushes by a pigtail, and distal portions, which function as a motor terminal  11  (see  FIG. 2 ) and extends axially from the terminal support  7   b . A flange  4   b  is formed on the bottom of the yoke  4 , as viewed in  FIG. 2 . An elastomeric seal  12  is fixed to the flange  4   b  and closes the cavity of the yoke  4 . The rotary shaft  6   a  has a distal side (lower side as viewed in  FIGS. 1 and 2 ) to which a sensor magnet  6   b  is fixed to rotate integrally with the rotary shaft  6   a.    
         [0017]     The reduction gear mechanism  3  includes a housing  21 , a worm shaft  22 , a worm wheel  23 , a clutch  24 , control circuit board (see  FIG. 2 ), a cover  26 , a fastener  27 , and an output shaft (not shown). In the preferred embodiment, the worm shaft  22  and the worm wheel  23  form a reduction gear mechanism.  
         [0018]     The housing  21  is made of resin and includes a fastening plate  21   a , a worm retainer  21   b , a wheel retainer  21   c , and a circuit board retainer  21   d . The fastening plate  21   a , which is shaped in correspondence with the flange  4   b  of the yoke  4 , is fixed to the flange  4   b  by screws  29 .  
         [0019]     The worm retainer  21   b , which is sleeve-like and extends in alignment with the rotary shaft  6   a , retains and supports the worm shaft  22  in a rotatable manner. In the worm retainer  21   b , a clutch  24  connects the worm shaft  22  and the rotary shaft  6   a . The clutch  24  functions to transmit drive force from the rotary shaft  6   a  to the worm shaft  22 . Further, the clutch  24  functions to prevent force from being transmitted from the worm shaft  22  to the rotary shaft  6   a . That is, the clutch  24  prevents the force applied to a load (worm shaft  22 ) from rotating the rotary shaft  6   a.    
         [0020]     The wheel retainer  21   c , which is disk-shaped and hollow, retains and supports the worm wheel  23  in a rotatable manner. The interior of the worm retainer  21   b  and the interior of the wheel retainer  21   c  are partially connected with each other where the worm shaft  22  engages the worm wheel  23 . The wheel retainer  21   c  and the worm retainer  21   b  are located on opposite sides of the terminal support  7   b . The wheel retainer  21   c  has opposing flat surfaces  21   e , which extend parallel to the flat surfaces  4   a  of the yoke  4 . The output shaft, which is connected to and rotated integrally with the worm wheel  23 , projects from one of the flat surfaces  21   e  of the wheel retainer  21   c  (the flat surface  21   e  located opposite to the one shown in  FIG. 2 ).  
         [0021]     The circuit board retainer  21   d  is box-shaped and located at a position corresponding to the motor terminal  11  (terminal support  7   b ). That is, the circuit board retainer  21   d  and the wheel retainer  21   c  are located on opposite sides of the worm retainer  21   b . The circuit board retainer  21   d  has an interior extending to a portion corresponding to the sensor magnet  6   b . The circuit board retainer  21   d  includes a slot  21   f  into which the control circuit board  25  is inserted from the exterior in a direction diagonal to the rotary shaft  6   a . Further, the circuit board retainer  21   d  has a flat surface  21   g  formed on the side opposite to the side the output shaft extends from the wheel retainer  21   c . A generally rectangular inlet  21   h  extends through the flat surface  21   g . An annular positioning wall  21   i  extends about the inlet  21   h  on the outer side of the circuit board retainer  21   d.    
         [0022]     The control circuit board  25  is retained in the circuit board retainer  21   d . Referring to  FIG. 2 , the control circuit board  25  includes a generally rectangular main portion  25   a  and an extended portion  25   b . An integrated circuit  31 , Hall elements  32 , actuator terminals  33 , a terminal support  34 , a board terminal  35 , and a connector block  36  are arranged on the control circuit board  25 . The control circuit board  25  of the preferred embodiment incorporates a so-called jam protection circuit. The jam protection circuit detects the rotation speed of the sensor magnet  6   b , or rotary shaft  6   a , with the Hall elements  32  located on the distal end of the extended portion  25   b . When the IC  31  determines from the rotation speed that the window glass has been jammed, the jam protection circuit reverses the flow of current to the motor  2 .  
         [0023]     Referring to  FIGS. 3 and 4 , the actuator terminals  33  are located at a position corresponding to the inlet  21   h . A terminal support  34  supports the actuator terminals  33  so as to extend orthogonal to the control circuit board  25 . The terminal support  34 , which is generally box-shaped, is fixed to the control circuit board  25 . A connector socket  34   a  is defined in the terminal support  34 . The actuator terminals  33  project from the bottom of the connector socket  34   a . A support flange  34   b  extends around the actuator terminals  33 . The support flange  34   b  is formed at the middle of the side walls of the terminal support  34 . An outer frame  34   c , which is formed on the rim of the support flange  34   b , extends in a direction opposite to the bottom of the terminal support  34 . A groove  34   d  is defined between the side wall of the terminal support  34 , the support flange  34   b , and the outer frame  34   c . An annular seal  37 , which is made of an elastic material such as elastomer, is fitted in the groove  34   d . An external connector support  38  is attached to the terminal support  34  so as to lengthen and extend the side walls of the connector socket  34   a . The external connector support  38  is arranged in the inlet  21   h.    
         [0024]     Referring to  FIG. 2 , the board terminal  35  is located at a position corresponding to the motor terminal  11 . The board terminal  35 , which is a female terminal, receives the motor terminal  11 , which is a male terminal, in a direction parallel to the plane of the control circuit board  25 .  
         [0025]     The control circuit board  25  is inserted through the slot  21   f  and then retained in the circuit board retainer  21   d . Afterward, when attaching the motor  2  to the housing  21 , the motor terminal  11  is electrically connected to the board terminal  35 . Further, the external connector support  38  is attached to the terminal support  34  in a state in which the control circuit board  25  is retained in the circuit board retainer  21   d.    
         [0026]     The cover  26  is attached to the housing  21  to close the slot  21   f  of the circuit board retainer  21   d . The cover  26  is made of a metal plate having bent ends that are hooked to the housing  21 .  
         [0027]     The fastener  27  is attached to the housing  21  at the inlet  21   h  of the circuit board retainer  21   d . As shown in  FIGS. 3 and 4 , the housing  21  includes a hollow, pipe-shaped fitting  41  and a hollow, pipe-shaped sealing member  42 . The fitting  41  is made of a resin material and includes a rectangular sleeve  41   a , which is fitted into the inlet  21   h  of the circuit board retainer  21   d , a fitting flange  41   b , which extends outward from one end of the sleeve  41   a , and two fastening pieces  41   c , which extend outward from the fitting flange  41   b  (see  FIG. 4 ). The fitting flange  41   b  includes a positioning portion  41   d , which is fitted into the positioning wall  21   i . The pipe-shaped sealing member  42  includes a seal portion  42   a  and a cylindrical portion  42   b . The seal portion  42   a  covers the fitting flange  41   b , the fastening pieces  41   c , and the positioning portion  41   d  of the fitting  41 . The cylindrical portion  42   b  extends from the seal portion  42   a  in a direction opposite the extending direction of the sleeve  41   a . Further, a sealing flange  42   c  extends radially outward from a distal side of the cylindrical portion  42   b.    
         [0028]     The sleeve  41   a  of the fitting  41  is fitted in the inlet  21   h  of the circuit board retainer  21   d . In this state, screws  43  (see  FIG. 4 ) and inserted through the fastening pieces  41   c  and fastened to the circuit board retainer  21   d  to fix the fastener  27  to the circuit board retainer  21   d  of the housing  21 . When fastening the fastener  27  to the housing  21 , the sleeve  41   a  is received in the groove  34   d  of the terminal support  34  without directly contacting the walls of the groove  34   d . In this state, the seal  37  is held between the sleeve  41   a  and the support flange  34   b . Further, the positioning portion  41   d  is fitted into the positioning wall  21   i , and the seal portion  42   a  of the pipe-shaped sealing member  42  is held between the inlet  21   h  of the circuit board retainer  21   d  and the fitting  41  so as to seal the space therebetween. The end of the sleeve  41   a  in the fitting  41  is formed so that it is thinner than the groove  34   d  of the terminal support  34  (see  FIGS. 3 and 4 ). This guides the end of the sleeve  41   a  into the groove  34   d  even if the position of the control circuit board  25  relative to the housing body  21  is not constant (i.e., even if the control circuit board  25  is displaced).  
         [0029]     Referring to  FIG. 4 , the electric actuator  1  is arranged between an inner panel  51  and an outer panel (not shown) of a vehicle door and then fixed to the inner panel  51 . More specifically, an inner panel receptacle  51   a  is formed in the inner panel  51 . The cylindrical portion  42   b  of the pipe-shaped sealing member  42  is fitted into the inner panel receptacle  51   a  so that the sealing flange  42   c  is adhered to the surface of the inner panel  51  about the inner panel receptacle  51   a . In this state, the electric actuator  1  is fastened to the electric actuator  1  by bolts. Then, an external connector  52  is engaged with the female connector formed by the connector socket  34   a  of the terminal support  34  and the external connector support  38 . This electrically connects external terminals  52   a , which are arranged in the external connector  52 , with the actuator terminals  33 . The external terminals  52   a  are connected to a controller (not shown), which functions as a power supply.  
         [0030]     The preferred embodiment has the advantages described below.  
         [0031]     (1) The electric actuator  1  includes the control circuit board  25 . The control circuit board  25  includes the terminal support  34  to support the actuator terminals  33 , which are connected to the external terminals  32   a . The housing  21  includes the inlet  21   h , which enables connection of the external terminals  52   a  from the outer side of the housing  21  to the actuator terminals  33 . Accordingly, the actuator terminals  33  are not insert-molded. This facilitates the manufacturing of the housing  21 .  
         [0032]     (2) Further, the sleeve  41   a  of the fitting  41  is arranged in the inlet  21   h  so as to extend into the circuit board retainer  21   d  of the housing  21 . Further, the seal  37  is arranged between the sleeve  41   a  and the terminal support  34 . Thus, even if liquid enters the fitting  41 , the liquid is prevented from entering the interior of the circuit board retainer  21   d , or the housing  21 . This prevents the electric circuit components and the motor  2  from being exposed to such liquids.  
         [0033]     (3) In a state in which the actuator terminals  33  are attached to the terminal support  34  but the external connector support  38  is not attached to the terminal support  34 , the control circuit board  25  is arranged in the circuit board retainer  21   d  in a direction orthogonal to the direction that the external connector  52  is connected to the external connector support  38 . This facilitates the assembly of the control circuit board  25 . Further, the stress produced by the connection of the external connector  52  is easily absorbed.  
         [0034]     Additionally, in a state in which the control circuit board  25  is attached to the housing  21  in the circuit board retainer  21   d , the external connector support  38  is attached to the terminal support and arranged in the inlet  21   h  to support the external connector  52  with the terminal support  34 . This facilitates the installation of the control circuit board  25  and has the external connector  52  securely supported by the external connector support  38 . In other words, when the control circuit board  25  is arranged in the inlet  21   h , the external connector support  38  lengthens the connector socket  34   a , which extends in the connection direction of the external connector  52 , to securely support the external connector  52 .  
         [0035]     (4) The fitting  41  is fixed to the pipe-shaped sealing member  42 , which includes the cylindrical portion  42   b  to form the fastener  27 . Then, the fitting  41  is engaged with the inlet  21   h  of the housing  21 . The cylindrical portion  42   b  of the pipe-shaped sealing member  42  prevents the external connector  52  and its wires from being exposed to liquids that enter the space between the inner panel  51  and the outer panel. Further, the pipe-shaped sealing member  42  includes the seal portion  42   a  to seal the space between the inlet  21   h  of the circuit board retainer  21   d . This decreases the number of components required to seal the space between the inlet  21   h  and the fitting  41 .  
         [0036]     (5) The terminal support  34  includes the groove  34   d , which surrounds the actuator terminals  33 , to receive the seal  37 . In this state, the sleeve  41   a  of the fitting  41  is fitted in the groove  34   d  so as to contact the seal  37 . This structure facilitates the arrangement of the seal  37 , prevents displacement of the seal  37 , and improves the reliability of the water resistant structure.  
         [0037]     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms.  
         [0038]     In the preferred embodiment, the control circuit board  25  is installed in the circuit board retainer  21   d  from a direction orthogonal to the connection direction of the external connector  52 . However, the installation direction is not restricted, and the control circuit board  25  may be installed in the circuit board retainer  21   d  from any direction.  
         [0039]     In the preferred embodiment, the external connector support  38  is attached to the terminal support  34  in a state arranged in the inlet  21   h  so as to support the external connector  52  with the terminal support  34 . However, the external connector support  38  may be eliminated, and the external connector  52  may be attached to only the terminal support  34 .  
         [0040]     In the preferred embodiment, the pipe-shaped sealing member  42  includes the seal portion  42   a  to seal the space between the inlet  21   h  of the circuit board retainer  21   d  and the fitting  41 . However, an independent component may be arranged between the inlet  21   h  and the fitting  41 .  
         [0041]     In the preferred embodiment, the terminal support  34  includes the groove  34   d , which surrounds the actuator terminals  33 . Further, the seal  37  is fitted in the groove  34   d . However, the groove  34   d  may be eliminated and another structure may be employed to hold a seal.  
         [0042]     The electric actuator  1  of the preferred embodiment is applied to a power window device. However, an electric actuator according to the present invention may be applied to any other types of devices. Further, the electric circuit components (jam prevention circuit) may be changed when necessary in accordance with the control circuit board.  
         [0043]     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.