Patent Publication Number: US-10790104-B2

Title: Rotary switch device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT application No. PCT/JP17/018385, which was filed on May 16, 2017 based on Japanese Patent Application (No. 2016-099040) filed on May 17, 2016, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a rotary switch device. 
     Description of Related Art 
     Patent literature 1 discloses a rotary switch device in which a movable contact member is rotated to be in contact with a fixed contact. In the rotary switch device of patent literature 1, a circular first fixed contact portion is exposed to be disposed at a center portion of a terminal base formed of an insulating material. Second and third fixed contact portions are disposed so as to surround the first fixed contact portion. 
     The movable contact member (contact plate) is urged to a terminal base side by a contact spring formed of a cylindrical coil spring held by a rotor, and a contact pressure with the fixed contact portion is secured. 
     [Patent Literature 1] JP-A-2015-103495 
     In the rotary switch device of patent literature 1, in order to hold the cylindrical coil spring in an upright state without falling down, a cylindrical hole for accommodating the cylindrical coil spring is required. However, an operation of inserting the cylindrical coil spring into the hole is troublesome because a coil center axis of the cylindrical coil spring has to be aligned with a center of the cylindrical hole and then the cylindrical coil spring is inserted. In particular, it is difficult to be inserted by an automatic machine and production efficiency is poor. 
     SUMMARY 
     One or more embodiments provide a rotary switch device in which a manufacturing efficiency is improved by improving an insertion operability of a compression coil spring. 
     According to one or more embodiments, a rotary switch device including a terminal base  3  to which a center portion contact  1  and a fixed contact  2  are fixed, a rotation operation member  4  which is operable to rotate around the center portion contact  1  with respect to the terminal base  3 , a plate-like movable contact member  7  which includes a contact protrusion part  5  which is pressed in contact with the center portion contact  1  at one end of one surface of plate thickness surfaces and a contact surface  6  which is in contact with the fixed contact  2  at another end of the one surface of the plate thickness surfaces, and which is held in the rotation operation member  4  so as to short-circuit between the center portion contact  1  and the fixed contact  2  at a conductive rotation position, and a compression coil spring  10  of a barrel type in which one end is supported by a bottom surface  9  of a spring accommodation hole  8  formed in the rotation operation member  4  and another end is pressed in contact with a back surface against the one surface of the plate thickness surfaces forming the contact protrusion part  5  and the contact surface  6  of the movable contact member  7  so as to urge the contact protrusion part  5  and the contact surface  6  to a side of the terminal base  3 . 
     In one or more embodiments, the compression coil spring of the barrel type is used for the compression coil spring  10  that presses the movable contact member  7  to apply a contact pressure with the contact on the terminal base  3  to the movable contact member  7 , and is inserted into the spring accommodation hole  8  of the rotation operation member  4 . The compression coil spring  10  of the barrel type has an outer shape in which a diameter is contracted at a tip and is gradually enlarged as going to a center portion, so that it is easy to introduce the reduced diameter portion of the tip into the spring accommodation hole  8  when the compression coil spring  10  is mounted on the spring accommodation hole  8 , and the gentle outer shape is guided to a predetermined position even when the compression coil spring  10  is introduced in an inclined shape. Therefore, an insertion operation is easy and an insertion operation by an automatic machine is also easy. 
     According to one or more embodiments, a coil inner diameter at a pressing end of the compression coil spring  10  to the movable contact member  7  may be formed smaller than a plate thickness of the movable contact member  7 . 
     In general, the contact pressure between the contacts pressed by the compression coil springs  10  is uniquely determined by a spring constant determined by the number of turns, a wire diameter, a coil diameter, or the like of the compression coil spring  10 , and a deflection amount. However, in a case where the coil diameter of the pressing end to the movable contact member  7  is larger than a dimension of the movable contact member  7  in a width direction, that is, a plate thickness, a wire end of the compression coil spring  10  protrudes from the movable contact member  7 . 
     If the wire end of the compression coil spring  10  protrudes from the movable contact member  7 , since an effective number of turns or a free length is decreased as compared to a case where a seat surface is fitted over the movable contact member  7 , the spring constant changes and a predetermined contact pressure cannot be obtained. However, whether or not protrusion of the wire end of the movable contact member  7  from the seat surface occurs is determined by a rotation angle around a coil center axis when mounting the compression coil spring  10 , and control is impossible, so that it is difficult to ensure a predetermined contact pressure. 
     Variation in the contact pressure changes a contact resistance between the contacts, so that it causes variation of an output potential and in a case where corrosion of the contact is prevented by applying corrosion resistant plating in the movable contact member  7  or the fixed contact  2  portion, an excessive increase in the contact pressure causes destruction of a corrosion resistant plating film, which in turn leads to an increase in contact resistance due to corrosion of the contact and also causes contact failure. 
     In one or more embodiments in which the inner diameter of the pressing end abutting against the movable contact member  7  is smaller than the plate thickness of the movable contact member  7 , the seat surface of the compression coil spring  10  can abut against the movable contact member  7  without protruding, so that the spring constant does not change depending on a mounted state and a stable contact pressure between the contacts can be provided. 
     As a result, for example, the corrosion resistant plating is applied to the movable contact member  7  and the fixed contact  2  to ensure conductivity by a low contact pressure, to prevent oxidation of the contact, and to eliminate the sliding contact between the contacts for removing an oxide film. Therefore, even in a case where the rotary switch device can be used in a low current specification, it is possible to reliably prevent peeling of the plating film due to an excessive increase in the contact pressure. 
     In addition, since the compression coil spring  10  of the barrel type has a coil portion having a diameter larger than that of the diameter-reduced end, an aspect ratio (L/D, where L is a free length and D is a coil average diameter) can be reduced compared to that of a cylindrical coil spring in which both ends are the coil diameter. Therefore, a buckling phenomenon during operation hardly occurs and a spring index (D/d, where d is a wire diameter) can be adjusted to a suitable value to maintain favorable workability. 
     According to one or more embodiments, the bottom surface may has a circular shape having substantially the same diameter as a coil outer diameter at a supported end of the compression coil spring  10  or a polygonal shape in which the circular shape is inscribed, and a cone-shaped portion  11  which gradually expands along an opening end is formed in a bottom portion  9  of the spring accommodation hole  8 . 
     In general, in the movable contact member  7  which is pressed by a single compression coil spring  10 , a rotational moment is generated except in a case where a pressing force acts in a moving direction passing through a center of gravity. Therefore, the contact pressure between the contact protrusion part  5  and the contact corresponding to the contact surface  6  changes depending on a position of an action point. 
     In addition, even in a case where the contact protrusion part  5  of the movable contact member  7  and a position corresponding to the contact surface  6  are respectively pressed by separate compression coil springs  10 , a reaction force from the center portion contact  1  or the fixed contact  2  is determined by a distance between action lines of a pressing force by the compression coil spring  10  and a distance between a reaction force action line from each contact and the action line of the pressing force by the compression coil spring  10 . Therefore, if a position of the action line of the compression coil spring  10  is not fixed, it causes variation of the contact pressure at each contact. 
     In one or more embodiments, the bottom surface  9  of the spring accommodation hole  8  which supports the supported end of the compression coil spring  10  is formed in the circular shape having substantially the same diameter as the coil outer diameter in the supported end of the compression coil spring  10  or in the polygonal shape having the circular shape inscribed therein, and the diameter is gradually expanded or enlarged along the opening end. Therefore, the compression coil spring  10  introduced into the cone-shaped portion  11  is naturally guided to a position at which the coil center axis is preset. 
     As a result, it is possible to precisely control the support position (base end position) of the compression coil spring  10 , so that no deviation of an action point of an urging force to the movable contact member  7  occurs and a stable contact pressure between the contacts can be provided. 
     In this case, the spring accommodation hole  8  may be formed so as to constrain a maximum coil diameter portion of the compression coil spring  10  and regulate falling of the compression coil spring  10 . In this case, since falling of the compression coil spring  10  can be effectively prevented, it is possible to further precisely determine the action position of the plating film to the movable contact member  7 . 
     According to one or more embodiments, a manufacturing efficiency can be improved by improving an insertion operability of the compression coil spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a steering lock apparatus. 
         FIG. 2  is an exploded perspective view of an ignition switch. 
         FIG. 3  is a view illustrating an arrangement of fixed contacts. 
         FIG. 4  is a view illustrating a position of a movable contact member at a LOCK position. 
         FIG. 5A  is a sectional view taken along line  5 A- 5 A of  FIG. 4 .  FIG. 5B  is an enlarged view of a  5 B portion of  FIG. 5A . 
         FIG. 6A  is a plan view illustrating a position of the movable contact member in an ON position.  FIG. 6B  is a sectional view taken along line  6 B- 6 B of  FIG. 6A . 
         FIG. 7A  is a view illustrating the movable contact member and illustrating a positional relationship of the movable contact member and compression coil springs.  FIG. 7B  is a view taken in direction of arrow  7 B in  FIG. 7A . 
         FIG. 8A  is a view illustrating a state where the compression coil spring in a free state is inserted into a spring accommodation hole.  FIG. 8B  is a sectional view taken along line  8 B- 8 B of  FIG. 5B .  FIG. 8C  is a sectional view taken along line  8 C- 8 C of  FIG. 5B . 
         FIG. 9  is a flowchart illustrating a conduction state of a contact of the ignition switch. 
         FIG. 10A  is a plan view illustrating a modification example of the movable contact member.  FIG. 10B  is a sectional view taken along line  10 B- 10 B of  FIG. 10A .  FIG. 10C  is a sectional view taken along line  10 C- 10 C of  FIG. 10B . 
     
    
    
     DETAILED DESCRIPTION 
     A rotary switch device of the present invention configured as an ignition switch used in a steering lock apparatus is illustrated in  FIG. 1  and the following. The steering lock apparatus of the example includes a cylinder lock  13  accommodated in a housing  12  and a cam member  14  connected to a terminal of a plug  13   a  of the cylinder lock  13 , and is fixed to a steering column (not illustrated). 
     The housing  12  is provided with a lock piece  15  which moves between a lock position which advances and retreats in a direction intersecting a rotation axis of the cam member  14  at a predetermined angle and protrudes into the steering column, and an unlock position which is accommodated in the housing. The lock piece  15  is urged to a direction of the lock position by a compression spring  15   a  and when the plug  13   a  of the cylinder lock  13  is rotatively operated from a lock rotation position, the lock piece  15  moves from the lock position where the lock piece  15  is locked to a steering shaft to the unlock position where the lock piece  15  is released, and the steering shaft can be operated. 
     In addition, the ignition switch is connected to the housing  12  to cause predetermined terminals to conduct in accordance with the rotation of the plug  13   a  and a power supply state to an electrical system of a vehicle to be changed. In order to transmit the rotational operation of the plug  13   a  to the ignition switch, a connecting bar  16  which meshes with the cam member  14  and rotates together with the cam member  14  is disposed in the housing  12 . 
     As illustrated in  FIG. 2 , the ignition switch includes a switch case  17  having a terminal base  3  having a circular shape in plan view, a rotation operation member  4  rotatable around a center of the terminal base  3  with respect to the switch case  17 , and a switch cover  18  connected to the switch case  17  to cover the rotation operation member  4 . A center portion contact  1  and a fixed contact  2  are disposed in the terminal base  3  formed by an insulating material in a state of being exposed to a rotation boundary surface with the rotation operation member  4 . 
     The center portion contact  1  and each fixed contact  2  are drawn into the switch case  17  via wiring. 
     The rotation operation member  4  is formed of an insulating material and the connecting bar  16  and a connecting hole  4   a  are formed at one end portion. The rotation operation member  4  is urged only when returning from a START position (described later) to an ON position by a torsion spring  19 , and moderately rotates at an appropriate connecting operation angle by fitting a click ball  21  urged by a click spring  20  into a groove of an inner wall of the switch cover  18 . 
     Furthermore, in rotation operation member  4 , a plate-like movable contact member  7  having a predetermined plate thickness is held toward the terminal base  3 . As illustrated in  FIGS. 7A and 7B , the movable contact member  7  includes a contact protrusion part  5  that is a V-shaped protrusion at one end and a flat contact surface  6  at the other end of the plate thickness surface, and a rounded chamfer is formed at a tip of the contact protrusion part  5  in order to keep a good contact state when the movable contact member  7  is pressed in contact with the center portion contact  1  which is described later. 
     Three of the flat movable contact members  7  formed as described above are used to correspond to the respective fixed contacts  2  which are described later. Silver plating as corrosion resistant conductive processing is applied to the surfaces of the movable contact member  7  and each fixed contact  2  in order to prevent occurrence of corrosion on the contact surface and enhance contact reliability without requiring a self-cleaning operation by a high contact pressure. 
     Each movable contact member  7  is held by the rotation operation member  4 , and is movable in a direction along a rotation axis (RA) in  FIG. 1 , and, as described below, is urged to a surface side of the terminal base  3  by compression coil springs  10  pressing the contact protrusion part  5  and a back surface of the contact surface  6 . 
     The ignition switch according to the example is formed to output a power supply voltage input from a power supply terminal to three output terminals of +IGN 1 , +IGN 2 , and START when the plug  13   a  is rotatively operated in the order of LOCK, ON, and START positions.  FIG. 9  illustrates a power supply operation to each terminal and power is supplied in the order of the +IGN 2  terminal and the +IGN 1  terminal by the movement of the plug from the LOCK position to the ON position. Thereafter, when the plug is rotated to the START position, first, the power supply to the +IGN 2  terminal is stopped, and then the power supply is started to the START terminal in addition to the +IGN 1  terminal where the power supply state is maintained. 
     The sequence described above is realized by short-circuiting the center portion contact  1  disposed at a center portion of the terminal base  3  and the fixed contact  2  disposed around the center portion contact  1  and connected to the +IGN 1  terminal, the +IGN 2  terminal, and the START terminal by the movable contact member  7  described above. 
     The three fixed contacts  2  are respectively disposed at terminal positions of three support portions  22  formed in the terminal base  3 . Each fixed contact  2  is formed in a rectangular shape intersecting the support portion  22 , the support portion  22  is disposed on two concentric circles with respect to the center of the terminal base  3 , and as illustrated in  FIGS. 5A and 5B , supports a corner portion of the contact surface  6  of the movable contact member  7  in a non-contact state with the fixed contact  2 . Moreover, in  FIG. 3 , the support portion  22  is indicated by hatching. 
     The contact surface  6  of the movable contact member  7  in a riding state on the support portion  22  is held at a position higher than a height of a center contact of the contact surface  6  in a state where the contact surface  6  illustrated in  FIG. 6B  rides on the fixed contact  2 . 
     As described above, in the non-contact state in which the movable contact member  7  is not in contact with the fixed contact  2 , the support portion  22  supports the end opposite to the contact protrusion part  5  of the movable contact member  7  and functions as a traveling path when the movable contact member  7  is horizontally and rotatively operated. 
     Furthermore, the center portion contact  1 , the fixed contact  2 , and the support portion  22  are formed in a floating island shape of which a periphery is surrounded by a recessed portion, and propagation of the abrasion powders between the fixed contacts  2 , and between the support portion  22  and the fixed contact  2 , and coagulated powder of molten splashes due to the arc discharge is regulated. 
     When the movable contact member  7  is operated to rotate in the clockwise direction in  FIG. 4  from a non-conductive state illustrated in  FIGS. 4 to 5B , the movable contact member  7  travels on the support portion  22  with the contact portion of the support portion  22  as the sliding portion, and then rides on an inclined surface  22   a  formed at a terminal of the support portion  22 . The inclined surface  22   a  is formed to gradually become a low back, the movable contact member  7  moved to the inclined surface  22   a  vertically rotates to a vicinity of a horizontal posture while reducing a vertical rotation angle, and lands on the fixed contact  2  as illustrated in  FIGS. 6A and 6B . 
     As illustrated in  FIG. 7B , the contact surface  6  of the movable contact member  7  is formed in a V shape in front view, so that landing to the fixed contact  2  or movement from the fixed contact  2  to the support portion  22  is smoothly performed. 
     If sliding loci of the movable contact members  7  in the center portion contact  1  overlap each other, a chance of wear at an overlapping portion increase. In order to prevent this, as illustrated by chain lines in  FIG. 6A , the movable contact member  7  that is in contact with and disconnected from the +IGN 1  terminal and the movable contact member  7  that is in contact with and disconnected from the +IGN 2  terminal of which rotation ranges overlap each other move along arcs (AC 1  and AC 2 ) having different diameters on the center portion contact  1 . 
     As illustrated in  FIGS. 8A to 8C , the movable contact member  7  is fitted into a contact mounting groove  23  formed in the rotation operation member  4 . The movable contact members  7  fitted into the contact mounting grooves  23  press the contact protrusion part  5  and a back surface with respect to a plate thickness surface on which the contact surface  6  is formed by the compression coil springs  10  inserted into the spring accommodation holes  8  penetrating the contact mounting grooves  23  to apply the contact pressure with the fixed contact  2  to the movable contact member  7 . 
     As illustrated in  FIG. 8A , the compression coil spring  10  is a compression coil spring of a barrel type having a coil diameter is large at a center portion and is gradually reduced as going to both ends, and the coil diameters at the both end are the same so as to be capable of being used in an inverted posture. 
     A spring constant of the compression coil spring  10  is adjusted to exceed the contact pressure so that a contact resistance value with respect for low current conduction is sufficiently low and to be equal to or less than a contact pressure at which peeling of the plating film during sliding occurs in a pressure contact state with the fixed contact  2  or the center portion contact  1  (the state in  FIG. 8B ). 
     In addition, the spring constant of the compression coil spring  10  of the barrel type is nonlinear because the coil diameter is changed, but a flexure region in the vicinity of the center portion having a large coil diameter substantially exhibiting linearity is used. 
     As illustrated in  FIG. 7A , the coil inner diameter at a tip portion of the compression coil spring  10  is formed to be smaller than a plate thickness of the movable contact member  7  and a pressing end with respect to the movable contact member  7  is held without protruding onto the plate thickness surface of the movable contact member  7 . 
     As a result, when the movable contact member  7  is pressed, a factor of changing the spring constant such as a loss of an effective number of turns caused by a wire end of the pressing end protruding from the plate thickness surface of the movable contact is eliminated. 
     As illustrated in  FIGS. 8A to 8C , the cone-shaped portion  11  is formed at the bottom portion of the spring accommodation hole  8  and the end portion (supported end) on the other side of the compression coil spring  10  is supported on the bottom surface  9 . The bottom surface  9  is formed in the same circular shape as the supported end of the compression coil spring  10  having a substantially same diameter as the coil outer diameter of the supported end thereof. 
     In addition, a wall surface of the cone-shaped portion  11  is formed by a conical surface that gradually expands in diameter as going to an opening end, and a diameter of an upper end, that is, the spring accommodation hole  8  is slightly larger than a maximum outer diameter of the compression coil spring  10 . 
     Furthermore, as illustrated in  FIG. 8B , a depth of the cone-shaped portion  11  is set to an extend in which a side wall is not in contact with an outer periphery of the compression coil spring  10  when an amount of deflection of the compression coil spring  10  becomes a maximum and the maximum outer diameter and the vicinity region thereof approach the bottom surface  9 . 
     Therefore, in the example, when the compression coil spring  10  is inserted into the spring accommodation hole  8 , the compression coil spring  10  is guided by the side wall of the cone-shaped portion  11  and the supported end is guided to the center position of the spring accommodation hole  8  which is set in advance. In this state, since the movement of the maximum diameter portion in a lateral direction is regulated by the side wall of the spring accommodation hole  8 , excessive inclination is prevented. 
     As a result, positions of an abutting portion of the compression coil spring  10  against the movable contact member  7  and the supporting end to the rotation operation member  4  are constant, so that the deflection amount of the compression coil spring  10 , that is, a size of the urging force can be precisely controlled. 
     In the example, the pressing force by the compression coil spring  10  is applied to two positions corresponding to the contact protrusion part  5  and the contact surface  6  of the movable contact member  7 , so that when an action position of the urging force by each compression coil spring  10  varies, distribution of the contact pressure between the center portion contact  1  and the fixed contact  2  varies, and on the other hand, there is a possibility to cause peeling of the plating film due to an excessive contact pressure and to cause conduction failure or the like due to an insufficient contact pressure. 
     On the other hand, in the example, since a load point and a size of load with respect to the movable contact member  7  are constant, it is possible to obtain the contact pressure which is set in advance at the contact. 
     In addition, in a case where the compression coil spring  10  is inserted into the spring accommodation hole  8 , since the coil diameter of the end portion is smaller than the diameter of the spring accommodation hole  8  and the compression coil spring  10  is guided during insertion, the insertion operation is easily performed. 
     Moreover, in the above description, a case where the bottom surface  9  of the spring accommodation hole  8  is formed in the circular shape is illustrated. Alternately, a polygonal shape circumscribing the coil outer diameter at the supporting end of the compression coil spring  10  is provided, or a rib or the like is protruded at a contact point position between a circumscribed polygonal shape and a coil outer periphery from the bottom surface  9  which is larger than in diameter the coil outer diameter, that is, a vertex position of an inscribed polygonal shape, so that the movement of the supporting end can be regulated by a rib tip. 
     In addition, in the above description, a case where the portion of the movable contact member  7  pressed by the compression coil spring  10  is formed to be a flat surface is illustrated. However, as illustrated in  FIGS. 10A to 10C , a fitting recessed portion  24  for the pressing end of the compression coil spring  10  to fit in can also be formed. In this case, in addition to a curved conical surface, the fitting recessed portion  24  can also be a linear inclined surface as illustrated by chain lines in  FIG. 10A . 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  center portion contact 
               2  fixed contact 
               3  terminal base 
               4  rotation operation member 
               5  contact protrusion part 
               6  contact surface 
               7  movable contact member 
               8  spring accommodation hole 
               9  bottom surface 
               10  compression coil spring 
               11  cone-shaped portion