Patent Publication Number: US-2015068876-A1

Title: Combination switch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2013-188934 filed in Japan on Sep. 12, 2013. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a combination switch disposed, for example, on the side of the steering column of a vehicle for use in switching the headlight and others. 
     2. Description of the Related Art 
     A variety of combination switches, for example, provided at the steering columns of automobiles are conventionally available. One of the combination switches known is described in Japanese Patent Application Laid-open No. 2012-221665. 
     As illustrated in  FIG. 4 , this combination switch includes a not-shown box-shaped switch case fixed to the side of a steering column and an operation lever  1  having a base end pivotally supported in the inside of the switch case so as to be swingable and a free front end provided with an operation unit  2 . The operation unit  2  has a disk-shaped fixed member  3  disposed at a predetermined position in an axial direction. A light switch knob  4  is disposed at the front end of the operation unit  2  with the fixed member  3  interposed. A fog switch knob  5  is disposed at the base end of the operation unit  2 . 
     As illustrated in  FIG. 5 , the fixed member  3  includes a cylindrical inner tube  3   b  integrally provided approximately at the central position on the front end surface of a disk-shaped opposing wall  3   a  facing the fog switch knob  5  and a pair of cams  3   c  integrally formed to project radially on the outer peripheral side of the inner tube  3   b.  A lever member  6  is inserted in the inner tube  3   b.  The cams  3   c  are each formed in an arc wall shape and each have a concave and convex cam surface  3   d  at the front end thereof. A cylindrical blocking wall  3   e  is integrally provided on the outside of the cams  3   c  on the opposing wall  3   a  of the fixed member  3 . 
     The fog switch knob  5  includes a cylindrical section  5   b  integrally provided on the inner periphery of a disk-shaped fixed wall  5   a  integrally provided inside and an outer tube  5   c  on the outer periphery. The lever member  6  is inserted in the cylindrical section  5   b.  The outer tube  5   c  is disposed to be fitted on the outer peripheral surface of the blocking wall  3   e.  A pair of elastic contact mechanisms  7  is provided on the inner periphery of the fixed wall  5   a.  Each elastic contact mechanism  7  includes a tubular holder  7   a,  a metal ball  7   b  disposed in the front end opening of the holder  7   a  in abutment with the cam surface  3   d,  and a coil spring  7   c  resiliently set in the inside of the holder  7   a  to bias the ball  7   b  in the direction of the cam surface  3   d.  The inside of each holder  7   a  is filled with grease  8  for keeping good rolling motion of the ball  7   b.    
     When the fog switch knob  5  is turned arbitrarily, the ball  7   b  in each elastic contact mechanism  7  comes into elastic contact with the concave and convex surface of each cam surface  3   d  by the spring force of the coil spring  7   c  to hold the operation position at a concave surface position and, for example, switch on and off the fog lamp. 
     In the conventional combination switch described above, the grease  8  in each holder  7   a  may be liquefied over repeated turning operations of the fog switch knob  5  to leak from the gap at the ball  7   b  to the outside and onto the outer surface of the operation unit  2 , as illustrated by the arrow in  FIG. 5 . 
     The cylindrical blocking wall  3   e  is therefore provided on the outside of the cams  3   c  on the opposing wall  3   a  of the fixed member  3  as described above thereby to increase the length of the leakage path of the grease  8  like a labyrinth. This labyrinth effect suppresses the leakage of the grease  8  to the outside of the combination switch. 
     The conventional technique described above, provides the cylindrical blocking wall  3   e  on the outer periphery of the fixed member  3  in order to block leakage of the grease  8 . However, the provision of the blocking wall  3   e  is not sufficient for blocking the leakage of the grease  8 . 
     Moreover, the outer diameter of the operation unit  2  is inevitably increased because the outer tube  5   c  of the fog switch knob  5  is disposed to be fitted on the outer peripheral side of the blocking wall  3   e.    
     SUMMARY OF THE INVENTION 
     The present invention is devised in view of the technical problems of the conventional combination switch and aims to provide a combination switch that can effectively block leakage of grease to the outside without increasing the outer diameter of the operation unit. 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     According to one aspect of the present invention, a combination switch includes a fixed member provided in an operation unit of an operation lever, an operation knob disposed adjacent to the fixed member and having a plurality of switch positions, a cam having a concave and convex cam surface on an opposing surface of the fixed member that faces the operation knob in an axial direction; and an elastic contact mechanism provided at a part of the operation knob that faces the fixed member, the elastic contact mechanism coming into elastic contact with the cam surface to hold an operation position of the operation knob, inside of the elastic contact mechanism being filled with grease. The opposing surface of the fixed member and the surface of the cam are formed in a mirror surface state with a surface roughness higher than surface roughness of other general parts. 
     According to another aspect of the present invention, the fixed member and the cam are integrally formed of a synthetic resin material, and a mirror surface section including the opposing surface of the fixed member and the surface of the cam is formed from a cavity inner surface in a mirror surface state of a die for molding the resin. 
     According to still another aspect of the present invention, the cam projects in a direction of the elastic contact mechanism at approximately center of the opposing surface of the fixed member, and the opposing surface is flat as a whole. 
     According to still another aspect of the present invention, the elastic contact mechanism includes a tubular holder provided inside the operation knob, a detent member movably arranged in a front end opening of the holder, and a spring member accommodated inside the holder for biasing the detent member in a direction of the cam surface. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a fixed member for use in an embodiment of a combination switch according to the present invention; 
         FIG. 2  is an exploded perspective view of a main part of the combination switch of the present embodiment; 
         FIG. 3  is a longitudinal sectional view of the main part of the combination switch of the present embodiment; 
         FIG. 4  is a perspective view of a conventional combination switch; and 
         FIG. 5  is a cross-sectional view along line A-A in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of a combination switch according to the present invention will be described below with reference to the figures. This embodiment is applied to a combination switch provided on the side of the steering column of an automobile for, for example, use in switching the kinds of lights such as a headlight and a fog lamp or turning on/off the lights. 
     As illustrated in  FIG. 2  and  FIG. 3 , the combination switch includes a not-shown box-shaped switch case fixed to the side of a not-shown steering column and an operation lever  11  having a base end pivotally supported in the inside of the switch case so as to be swingable and a free front end provided with an operation unit  13 . 
     The operation lever  11  includes a tubular lever member  12  made of a synthetic resin material in an inner axial direction and the operation unit  13  provided on the outer periphery of a small-diameter lever portion  12   a  coupled to the front end of the lever member  12 . The operation lever  11  is swung as a whole on a support point in the switch case through the lever member  12 , whereby a movable switch member in the switch case is displaced to allow switch operations such as switching turn signals and headlight illumination directions. The lever member  12  has one end engaged with a not-shown movable contact member on the switch case side and the other end extending into a light switch knob  14  described later. 
     The operation unit  13  is fitted in the switch case at a base end side (base portion) thereof in the longitudinal direction and has, at a front end side thereof, the light switch knob  14 , a fixed knob  15 , which is a fixed member adjacent to the light switch knob  14  in the axial direction, a fog switch knob  16 , which is an operation knob adjacent to the light switch knob  14  on the other side with the fixed knob  15  interposed, and a cover knob  17  adjacent to the fog switch knob  16 . The light switch knob  14 , the fixed knob  15 , the fog switch knob  16 , and the cover knob  17  have a common axial center. The knobs  14 ,  15 ,  16 ,  17  are each formed of a synthetic resin material with an injection molding machine. 
     Turning the light switch knob  14  turns the lever member  12  to operate the movable contact member on the switch case side so that the tail light, the small light, and the headlight are switched on and off. 
     As illustrated in  FIG. 1  to  FIG. 3 , the fixed knob  15  includes a disk-shaped opposing wall  18  facing the inside of the fog switch knob  16 , an outer tube  19  integrally provided on the outer peripheral edge of the opposing wall  18 , a cylindrical inner tube  20  integrally provided at the inner peripheral center position of the opposing wall  18 , and a pair of arc wall-shaped cams  21 ,  22 . The lever member  12  is inserted in the inner tube  20 . The cams  21 ,  22  are arranged radially on the outer peripheral side of the inner tube  20  on an opposing surface  18   a  of the opposing wall  18  on the fog switch knob  16  side to project toward the inside of the fog switch knob  16 . On the back surface opposite to the opposing surface  18   a  of the opposing wall  18 , a pair of arch-shaped guide walls  23  pivotally guiding the light switch knob  14  is integrally provided to project at a position of 180° in the circumferential direction. 
     On both sides of the cams  21 ,  22 , four rectangular first reinforcing ribs  24   a  to  24   d  are integrally provided. A pair of arc-shaped second reinforcing ribs  25   a,    25   b  is integrally provided between the first reinforcing ribs  24   a  and  24   b  and between  24   c  and  24   d,  and their ends are integrally coupled. 
     The cam  21 ,  22  has two concave surfaces  21   a,    22   a  and three convex surfaces  21   b,    22   b  as a cam surface at the front end. 
     As illustrated in  FIG. 3 , the fog switch knob  16  includes a cylindrical section  27  integrally provided on the inner periphery of a disk-shaped fixed wall  26  provided inside and an outer tube  28  integrally provided on the outer periphery to face the outer tube  19  of the fixed knob  15  in the axial direction. The lever member  12  is inserted in the cylindrical section  27 . A pair of elastic contact mechanisms  29 ,  30  is provided on the inner periphery of the fixed wall  26 . The elastic contact mechanism  29 ,  30  includes a tubular holder  29   a,    30   a,  a metal ball  29   b,    30   b  disposed in the front end opening of the holder  29   a,    30   a  in abutment with the concave and convex surfaces  21   a,    22   a,    21   b,    22   b,  and a coil spring  29   c,    39   c  resiliently set in the inside of the holder  29   a,    30   a  to bias the ball  29   b,    30   b  in the direction of the concave and convex surfaces  21   a  to  22   b.  The inside of the holder  29   a,    30   a  is filled with grease  31  for keeping good rolling motion of the ball  29   b,    30   b.    
     When the fog switch knob  16  is turned arbitrarily, the ball  29   b,    30   b  of the elastic contact mechanism  29 ,  30  comes into elastic contact with the concave and convex surfaces  21   a  to  22   b  by the spring force of a coil spring  29   c,    30   c  to hold the operation position at the concave surface  21   a,    22   a  and, for example, switch on and off the fog lamp. 
     The opposing surface  18   a  of the opposing wall  18  of the fixed knob  15  and the outer peripheral surfaces  21   c,    22   c  and the concave and convex surfaces  21   a  to  22   b  of the cams  21 ,  22  are formed in a mirror surface state with a surface roughness higher than the surface roughness of general parts including the first and second reinforcing ribs  24   a  to  24   d,    25   a,    25   b.    
     More specifically, as shown by the dots in  FIG. 1 , the region of the mirror surface section as described above is formed throughout the entire outer peripheral section of the opposing surface  18   a  of the opposing wall  18  excluding the entire outer surfaces of the first and second reinforcing ribs  24   a  to  24   d,    25   a,    25   b  and the inside of the cams  21 ,  22 , and entirely on the concave and convex surfaces  21   a  to  22   b  and the outer peripheral surfaces  21   c,    22   c  of the surfaces of cams  21 ,  22  excluding the inner peripheral surface. 
     The mirror surface section including the opposing surface  18   a  and the surfaces of the cams  21 ,  22  is formed from the inner surface of the cavity formed in a mirror surface state of an injection molding die for resin molding the fixed knob  15 . 
     The surface roughness of the mirror surface section is set to such a roughness level that does not form minute lines or other marks on the surfaces such as the opposing surface  18   a  and the concave and convex surfaces  21   a,    22   b  and the outer peripheral surfaces  21   c,    22   c  of the cams  21 ,  22  and does not cause capillary action. 
     According to the present embodiment, even when the grease  31  in the holders  29   a,    30   a  is liquefied over repeated turning operations of the fog switch knob  16  and leaks, though slightly, from the front end openings of the holders  29   a,    30   a  through the outer surfaces of the balls  29   b,    30   b  to the outside and adheres to the concave and convex surfaces  21   a  to  22   b  of the cams  21 ,  22  of the fixed knob  15 , the leakage from the outer peripheral surfaces  21   c,    22   c  of the cams  21 ,  22  to the outside can be blocked. 
     As previously mentioned, if the surface roughness of the opposing surface  18   a  and the cams  21 ,  22  is rough, the capillary action makes the grease  31  more likely to leak. However, the surface roughness of the opposing surface  18   a,  the concave and convex surfaces  21   a  to  22   b,  and the outer peripheral surfaces  21   c,    22   c  is set high in a mirror surface state, thereby avoiding capillary action. The leakage of the liquefied grease  31  thus can be suppressed. 
     Even if the liquefied grease adheres to the opposing surface  18   a  of the opposing wall  18  through the outer peripheral surfaces  21   c,    22   c  or other surfaces, spread and leakage can be suppressed sufficiently since the opposing surface  18   a  is also formed in a mirror surface state. The grease  31  thus no longer leaks onto the outer peripheral surface of the operation unit  13 . 
     Even if the liquefied grease  31  leaks from the concave and convex surfaces  21   a  to  22   b  or the outer peripheral surfaces  21   c,    22   c  toward the first reinforcing ribs  24   a  to  24   d  or the second reinforcing ribs  25   a,    25   b,  the leakage from the mirror-surface opposing surface  18   a  to the outer peripheral side can be sufficiently suppressed. 
     As described above, the present embodiment eliminates the need for providing a blocking wall for blocking external leakage of grease on the outer peripheral side of the fixed knob as in the conventional example described above and may reduce the outer diameter of the fixed knob  15  as much as possible. In this case, the diameter of the operation unit  13  can be reduced as a whole. 
     The present invention is not limited to the configuration of the foregoing embodiment. For example, in addition to the predetermined places such as the opposing surface  18   a  and the cams  21 ,  22 , for example, the surfaces of the first and second reinforcing ribs  24   a  to  24   d,    25   a,    25   b  may be formed in a mirror surface state. 
     The present invention is applicable to any part of a combination switch having a detent mechanism including the cams  21 ,  22  and the elastic contact mechanisms  29 ,  30 . The combination switch is applicable to devices or instruments other than vehicles. 
     The mirror finish of the opposing surface  18   a  of the fixed knob  15  and other parts may not be necessarily provided by the cavity surface of a molding die but may be provided by predetermined polishing after molding. 
     The inventor of the subject application has elaborately examined the cause of the leakage of liquefied grease from the elastic contact mechanisms to the outer surface of the operation unit along the surface of the fixed member or other parts, through experiments and other means. The inventor has noted the surface roughness of the opposing surface of the fixed member and found that coarse surface roughness causes capillary action to make the liquefied grease more likely to leak. 
     In the present invention, the opposing surface of the fixed member and the surfaces of the cams are formed in a mirror surface state with a surface roughness higher than the surface roughness of the other general parts, thereby suppressing the capillary action at the opposing surface and the cam surface. The leakage to the outside is thus blocked effectively. 
     In the combination switch according to one aspect of the present invention, the combination switch can effectively block leakage of grease to the outside. 
     In the combination switch according to another aspect of the present invention, the combination switch facilitates the operation of forming a mirror surface section when compared with polishing after molding, because the mirror surface section including the opposing surface of the fixed member and the surfaces of the cams are formed from the cavity inner surface of a molding die. 
     In the combination switch according to still another aspect of the present invention, the combination switch increases the grease leakage blocking effect owing to the mirror finish, because the opposing surface is flat as a whole. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.