Abstract:
Provided is a temperature sensitive actuator attaching structure wherein the ease of attachment is improved. A heat generating element ( 51 ) generates heat by energizing a temperature sensitive actuator ( 2 ) via conducting terminals ( 41, 42 ). The generated heat expands a wax (W) to project a piston ( 21 ), and an elastic member ( 23 ) biases the piston ( 21 ) in a direction opposite to the projecting direction. In order to attach the temperature sensitive actuator ( 2 ) to an attachment portion ( 11 ) of an object member ( 1 ), fixing protrusions ( 41   a ) are provided in the conducting terminal ( 41 ) of the temperature sensitive actuator ( 2 ), and receiving portions ( 14 ) which can receive the fixing protrusions ( 41   a ) in a direction perpendicular to the axis of the piston ( 21 ) are provided in the attachment portion ( 11 ). The temperature sensitive actuator ( 2 ) is attached to the object member ( 1 ) by inserting the fixing protrusions ( 41   a ) into the receiving portions ( 14 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to an attaching structure for attaching to a mounting member a temperature sensitive actuator that, by heating up a thermo-element, expands wax and projects a piston. 
         [0003]    2. Description of the Background Art 
         [0004]    Conventionally, there is known, attached to a mounting member composed of an automatic choke device, a temperature sensitive actuator comprised of a thermo-element that generates heat when energized by an electric current through terminals, wax that expands with the heating up of the thermo-element, a piston that projects through an aperture formed in the casing of the actuator as the wax expands, and an elastic member that biases the piston in a direction opposite to the direction in which it projects (for example, JP-2006-63864-A). 
         [0005]    In the device described in JP-2006-63864-A, a cylinder is formed on the mounting member and the temperature sensitive actuator is inserted into the cylinder. However, with such a configuration, the axis along which the piston of the temperature sensitive actuator moves during operation and the axis of the cylinder are the same, with the result that the temperature sensitive actuator easily falls out of the cylinder. For this reason, typically the temperature sensitive actuator is attached to the mounting member with screws, to prevent the temperature sensitive actuator from falling out of the cylinder. 
         [0006]    However, such an arrangement requires means for screwing the temperature sensitive actuator to the mounting member, necessitating time and trouble and increasing manufacturing costs. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has as its object to provide an attaching structure that improves the ease with which the temperature sensitive actuator is assembled. 
         [0008]    To achieve this object, the present invention provides an attaching structure for attaching to a mounting member a temperature sensitive actuator having a thermo-element that generates heats when energized through electrical terminals, wax that expands when heated by the heat from the thermo-element, a piston that projects as the wax expands, and a elastic member that biases the piston toward a non-projecting side, the attaching structure comprising fixing protrusions provided to the temperature sensitive actuator electrical terminals and openings provided to the mounting member that accommodate the fixing protrusions from a direction orthogonal to a longitudinal axis of the piston, wherein the temperature sensitive actuator is fixedly mounted in place by the fixing protrusions being accommodated within the openings. 
         [0009]    According to the present invention, fixing protrusions are provided to the electrical terminals, and these fixing protrusions are inserted into openings in the mounting member from a direction orthogonal to the long axis of the piston to fix the temperature sensitive actuator in place on the mounting member. As a result, it is possible to attach the temperature-sensitive actuator without screws, and compared to the conventional actuator it is possible to improve the ease with which the temperature sensitive actuator is assembled. 
         [0010]    Moreover, according to the present invention, a concave portion open to the direction in which the elastic member biases the piston is formed in the openings, and the fixing protrusions are biased by the elastic member against the concave portions to fix the temperature sensitive actuator in place. 
         [0011]    With such a structure, it is possible to fix the temperature sensitive actuator securely in place and it is possible to improve further the ease with which the temperature sensitive actuator is assembled using the biasing force of the elastic member that returns the piston of the temperature sensitive actuator to the non-projecting state as the temperature decreases. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]      FIG. 1A  is a plan view of a temperature sensitive actuator attaching structure according to a first embodiment of the present invention and  FIG. 1B  shows a front view of the first embodiment; 
           [0013]      FIG. 2  is a perspective view of a temperature sensitive actuator according to the first embodiment; 
           [0014]      FIG. 3  is an enlarged view of an attaching portion of a mounting member of  FIG. 1A ; 
           [0015]      FIG. 4  is a side view of the attaching portion shown in  FIG. 3 ; 
           [0016]      FIG. 5  is a perspective view of a temperature sensitive actuator according to a second embodiment; 
           [0017]      FIG. 6  is a cross-sectional view of an attaching portion of a mounting member of the second embodiment; 
           [0018]      FIG. 7  is a cross-sectional view along a line VII-VII in  FIG. 6 ; 
           [0019]      FIG. 8  is a cross-sectional view showing a piston of the temperature sensitive actuator of the second embodiment in a non-projecting state; 
           [0020]      FIG. 9  is a cross-sectional view showing a piston of the temperature sensitive actuator of the second embodiment in a projecting state; and 
           [0021]      FIG. 10  illustrates a temperature sensitive actuator attaching structure according to a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    With reference to  FIGS. 1-4 , a description is given of a temperature sensitive actuator attaching structure according to a first embodiment of the present invention, using an automatic choke device as the thing to which the actuator is to be attached. An automatic choke device  1  shown in  FIG. 1  is mounted on a carburetor installed in an ordinary engine, not shown, and is provided with a temperature sensitive actuator  2  enclosing an outwardly projectable piston  21 , and a butterfly-type choke valve  32  that closes an air intake path  31 . When the piston  21  of the temperature sensitive actuator  2  projects outward, it closes the choke valve  32  through a link mechanism  33 . 
         [0023]    As shown in  FIG. 2 , the temperature sensitive actuator  2  is provided with two electrical terminals, a first terminal  41  and a second terminal  42 , spaced apart at an interval along the longitudinal axis of the piston  2 . To each of the terminals  41 ,  42  are connected lead wires  43   a ,  43   b . The temperature sensitive actuator  2  is energized through the two terminals  41 ,  42 , a thermo-element composed of a PTC heater disposed within a casing  24  heats up, and the wax expands, projecting the piston  21 . 
         [0024]    A pair of fixing protrusions  41   a  is formed on the forward end electrical terminal  41 . An attaching portion  11  for attaching the temperature sensitive actuator  2  is provided to the automatic choke device  1 . The attaching portion  11  is configured as a substantially rectangular convex wall portion  12 , and inside this convex wall portion  12  is attached the temperature sensitive actuator  2 . 
         [0025]    A cutout  13  that accommodates the piston  21  is provided in the forward end of the convex wall portion  12 . In addition, openings  14  that accommodate the pair of fixing protrusions  41   a  are formed in the sides of the convex wall portion  12 . Each of the openings  14  is provided with a rearward facing concave portion  14   a . A cutout  16  that abuts the temperature sensitive actuator  2  casing  24  to position the temperature sensitive actuator  2  is provided in the rear end of the convex wall portion  12 . 
         [0026]    The tip of the piston  21  is formed with a reduced diameter, by which a stepped portion  21   a  is formed. In addition, attached to the piston  21  is a bearing member  22  that is engaged by the stepped portion  21   a  near the tip of the piston  21  and bears an elastic member  23  composed of a return spring via a flange  22   b  provided to the rear end of the piston  21 . 
         [0027]    The elastic member  23  composed of a return spring is disposed between the flange  22   b  and an inner face of the forward end of the convex wall portion  12 . The elastic member  23  biases the piston rearward to a non-projecting state through the bearing  22  that is engaged by the stepped portion of the piston  21 . 
         [0028]    The fixing protrusions  41   a  of the temperature sensitive actuator  2  are biased by the elastic member  23  and abut the read end face of the concave portions  14   a . By so doing, the temperature sensitive actuator  2  is prevented from moving axially with respect to the automatic choke device  1 . 
         [0029]    Moreover, by positioning the pair of fixing protrusions  41   a  of the temperature sensitive actuator  2  within the concave portions  14   a , the temperature sensitive actuator  2  is prevented from rotating within the convex wall portion  12  as well as from falling out of the convex wall portion  12 . 
         [0030]    With the temperature sensitive actuator  2  attaching structure of the first embodiment, the temperature sensitive actuator  2  is strongly fixedly mounted within the convex wall portion  12  by the elastic member  23 , the fixing protrusions  41   a ,  41   a , and the concave portions  14   a ,  14   a . As a result, the temperature sensitive actuator  2  is reliably prevented from falling out of the convex wall portion  12  due to vibration or the like, and further, compared to the conventional screw-stopped actuator, the ease with which it is possible to assemble the temperature sensitive actuator  2  is improved. 
         [0031]    Moreover, since there is no need for the space used for screwing the actuator in place as in the conventional case, there is greater range of choices available for the location of the temperature sensitive actuator  2  and at the same time it is possible to make the automatic choke device  1  more compact. In addition, because the casing  24  of the temperature sensitive actuator  2  abuts the cutout  16  in the rear end of the convex wall portion  12 , the temperature sensitive actuator  2  is positioned in place. This positioning, together with the fixing protrusions  41   a ,  41   a  and the concave portions  14   a ,  14   a , can prevent the temperature sensitive actuator  2  from tilting within the convex wall portion  12 . 
         [0032]    It is to be noted that although in the first embodiment a description is given of a case in which the thing to which the temperature sensitive actuator  2  is to be attached is the automatic choke device  1 , the thing to which the temperature sensitive actuator  2  is to be attached is not limited thereto. 
       Second Embodiment 
       [0033]    Next, with reference to  FIGS. 5-9 , a description is given of a temperature sensitive actuator attaching structure according to a second embodiment of the present invention. As with the first embodiment, the temperature sensitive actuator  2  of the second embodiment is one that is attached to an automatic choke device  1 . Elements that are the same as those of the first embodiment are given the same reference numerals and a description thereof is omitted. 
         [0034]    It is to be noted that the temperature sensitive actuator  2  of the second embodiment, like the temperature sensitive actuator  2  of the first embodiment, is energized through two electrical terminals  41 ,  42 , a thermo-element  51  composed of a PTC heater disposed within a casing  24  (see  FIG. 8  and  FIG. 9 ) heats up, and wax W (see  FIG. 8  and  FIG. 9 ) expands, projecting the piston  21  outward. 
         [0035]    As shown in  FIG. 5 , in the temperature sensitive actuator  2  of the second embodiment a pair of fixing protrusions  42   a ,  42   a  is also provided on the rear end electrical terminal  42 . In addition, as shown in  FIGS. 6-9 , instead of the cutout  16  of the first embodiment a pair of openings  15 ,  15  that accommodate the fixing protrusions  42   a ,  42   a  are formed in the side wall of the convex wall portion  12  of the second embodiment. The openings  15 ,  15  are each provided with a rearward facing concave portion  15   a ,  15   a.    
         [0036]    The tip of the piston  21  is formed with a reduced diameter, thus forming a stepped portion  21   a . In addition, attached to the piston  21  is a bearing member  22  that is engaged by the stepped portion  21   a  near the tip of the piston  21  and bears an elastic member  23  composed of a return spring via a flange  22   b  provided to the rear end of the piston  21 . 
         [0037]    The elastic member  23  composed of a return spring is disposed between the flange  22   b  and an inner face of the forward end of the convex wall portion  12 . The elastic member  23  biases the piston rearward to a non-projecting state through the bearing  22 , which is engaged by the stepped portion of the piston  21 . 
         [0038]    The fixing protrusions  41   a  of the temperature sensitive actuator  2  are biased by the elastic member  23  and abutted against the rear end face of the concave portions  14   a . By so doing, the temperature sensitive actuator  2  is prevented from moving axially with respect to the automatic choke device  1 . 
         [0039]    The fixing protrusions  41   a ,  42   a  are positioned inside the openings  14   a ,  15   a , so that the temperature sensitive actuator  2  is prevented from rotating within the convex wall portion  12  as well as from falling out of the convex portion  12 . 
         [0040]    With the attaching structure of the temperature sensitive actuator  2  according to the second embodiment, the temperature sensitive actuator  2  is strongly fixedly mounted within the convex wall portion  12  by the elastic member  23 , the fixing protrusions  41   a ,  42   a , and the concave portions  14   a ,  15   a . As a result, the temperature sensitive actuator  2  is reliably prevented from falling out of the convex wall portion  12  due to vibration or the like, and further, compared to the conventional screw-stopped actuator, the ease with which it is possible to assemble the temperature sensitive actuator  2  is improved. Moreover, since there is no need for the space used for screwing the actuator in place as in the conventional case, there is greater range of choices available for the location of the temperature sensitive actuator  2  and at the same time it is possible to make the automatic choke device  1  more compact. 
         [0041]    In addition, the fixing protrusions  41   a  are abutted against the rear end faces of the concave portions  14   a  by the elastic member  23 , and the fixing projections  42   a  are spaced an interval apart from the rear end face of the concave portions  15   a . As a result, matters are arranged so that it is possible to accomplish accurate positioning with the rear end faces of the concave portions  14   a  alone, and not only is it possible to design the depth of the concave portions  15   a  so as to create a gap with respect to the fixing protrusions  42   a  but it is also possible to form the concave portions  15   a  with ease. 
         [0042]    It is to be noted that it is also possible to achieve the same effect with concave portions  14   a ,  15   a  formed so that the fixing protrusions  42   a  abut the rear end faces of the concave portions  15   a  while the fixing protrusions  41   a  are space an interval apart from the rear end faces of the concave portions  14   a.    
         [0043]    Moreover, although in the second embodiment a description is given of a case in which the thing to which the temperature sensitive actuator  2  is to be attached is the automatic choke device  1 , the thing to which the temperature sensitive actuator  2  is to be attached is not limited thereto. 
       Third Embodiment 
       [0044]    As a third embodiment, as shown in  FIG. 7 , the openings  14 ,  15  may be formed as slits and the fixing protrusions  41   a ,  42   a  simply pressed into the openings  14 ,  15  to fix the temperature sensitive actuator  2  in place. The concave portions  14   a ,  15   a  of the second embodiment are not provided to the openings  14 ,  15  of the third embodiment.