Patent Publication Number: US-9412538-B2

Title: Rotary operation type electronic component

Description:
TECHNICAL FIELD 
     The present invention relates to rotary operation type electronic components which are used mainly in portable electronic devices and allow the electrical resistance between terminals to be changed or allow electrical connection between terminals to be switched by rotation of a control shaft. 
     BACKGROUND ART 
     Rotary switches or rotary variable resistors (these components will be collectively referred to as rotary operation type electronic components) used, for example, in portable electronic devices may be operated by a gloved hand or in an environment where it is difficult to work with precision. Those portable electronic devices are accordingly required to have rotary operation type electronic components having a large rotary-operation knob for easier operation. The larger the operation knob becomes, however, the more the operation torque is applied to the control shaft. Therefore, an erroneous operation is likely to happen if the operation knob is turned excessively, or is turned unintentionally due to an unexpected force from the outside or when the operator is startled by a sudden sound or light. Rotary operation type electronic components reduced in size for miniaturized portable electronic devices have naturally reduced the operation torque required for rotary operation and have the problem of increasing the possibility of similar erroneous operation. Accordingly, a rotary operation type electronic component that requires a large torque for the turning operation is proposed in Patent literature 1. 
       FIG. 1  shows a sectional view of the rotary operation type electronic component disclosed in Patent literature 1, in which a thin resilient metal sheet  300  folded into a polygon (hereafter referred to as a polygonal leaf spring) is placed between the inner periphery of a through shaft hole  100   a  formed in a shaft supporter  100  and the outer periphery of a control shaft  200  inserted into the through shaft hole  100   a . The polygonal leaf spring  300  is held in such a bent state that the center of each folded side is pressed radially outward by the outer periphery of the control shaft  200 . When the control shaft  200  is going to be turned, a sliding frictional force is generated between the leaf spring  300  and the control shaft  200  and an amount of torque corresponding thereto is needed for the turning operation. By placing such a type of polygonal leaf spring  300  to increase the torque needed for the turning operation, the possibility of erroneous operation can be reduced. 
     PRIOR ART LITERATURE 
     Patent Literature 
     
         
         Patent literature 1: Japanese Patent Application Laid Open No. H11-329806 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the structure disclosed in Patent literature 1 as shown in  FIG. 1 , the amount of bending of each folded side must be increased to increase the operation torque, but the largest possible amount of bending (clearance that ensures the amount of bending) is structurally limited to r(1−cos π/N), where the inside diameter of the through shaft hole  100   a  is 2r, and the number of folded corners of the polygonal leaf spring  300  is N (the thickness of the leaf spring is ignored, and both ends of the polygonal leaf spring are considered to be connected to each other, forming a single folded corner), meaning that N must be reduced to increase the clearance. If N is reduced, the number of positions at which the polygonal leaf spring  300  and the control shaft  200  are in contact with each other decreases, increasing friction correspondingly at each of the positions where the leaf spring is in contact. If N is increased to decrease friction, the length of each folded side of the leaf spring is reduced correspondingly, and a slight change in the amount of bending would vary the operation torque greatly, so that the amount of bending of a folded side must be specified with a higher precision in order to obtain a desired torque. These problems make it difficult to manufacture small rotary operation type electronic components. 
     An object of the present invention is to provide a rotary operation type electronic component that can be designed and manufactured more easily than conventional ones. 
     Means to Solve the Problems 
     To solve the above-described problems, a rotary operation type electronic component according to the present invention includes a columnar control shaft; a shaft supporter having a circular through shaft hole into which the control shaft is inserted; an electrical signal control section which is attached to one end of the shaft supporter and allows an electrical signal to be controlled by rotary operation of the control shaft; and a cylindrical spring which is held to encircle the outer periphery of the control shaft, in a ring-shaped spring holding space formed between the outer periphery of the control shaft and the inner periphery of the through shaft hole, and has a ring shape with an opening cut in the direction of the central axis. The cylindrical spring includes a plurality of leaf spring portions which extend in the direction of the central axis of the control shaft, are connected together in the circumferential direction of the control shaft, and are arranged on the outer periphery of the control shaft. The plurality of leaf spring portions have curved projection portions formed by curving their central areas in the length direction to project toward the same side, which is the radially inner or outer side of the cylindrical spring, are placed resiliently between the outer periphery of the control shaft and the inner periphery of the through shaft hole, and are given radially opposite pressing forces at both end portions of the leaf spring portions and the curved projection portions. 
     Effects of the Invention 
     Since the number of cylindrically arranged leaf spring portions and the largest amount of bending of the leaf spring portions can be specified independently of each other according to the present invention, it becomes easy to design rotary operation type electronic components and it becomes possible to reduce the size of those components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a rotary operation type electronic component disclosed in Patent literature 1; 
         FIG. 2  is an exploded perspective view of a rotary operation type electronic component according to an embodiment of the present invention; 
         FIG. 3  is a partial sectional view of the rotary operation type electronic component according to the embodiment of the present invention; 
         FIG. 4A  is a perspective view of a cylindrical spring used in the rotary operation type electronic component of the present invention; 
         FIG. 4B  is a perspective view showing a first modification of the cylindrical spring; 
         FIG. 4C  is a perspective view showing a second modification of the cylindrical spring; 
         FIG. 4D  is a perspective view showing a third modification of the cylindrical spring; 
         FIG. 5A  is a perspective view showing a fourth modification of the cylindrical spring; 
         FIG. 5B  is a perspective view showing a fifth modification of the cylindrical spring; 
         FIG. 5C  is a perspective view showing a sixth modification of the cylindrical spring; and 
         FIG. 5D  is a perspective view showing a seventh modification of the cylindrical spring. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Now, an embodiment of the present invention will be described in detail. 
     [Embodiment] 
       FIG. 2  is a perspective view of a rotary operation type electronic component according to the present invention, showing parts separated and arranged in the direction of the central axis X, and  FIG. 3  is a partial sectional view of an assembled rotary operation type electronic component along the central axis X. The rotary operation type electronic component of the present invention includes a columnar control shaft  10  made of metal, a cylindrical spring  20  which is formed by a metal sheet having spring characteristics and which has a ring shape with an opening cut in the direction of the axis, a shaft supporter  30  made of metal or resin, an electrical signal control section  40 , and a retaining ring  50  which is made of metal and which has an opening cut. 
     The columnar control shaft  10  includes a columnar control portion  11  with a flat face  11   a  formed by cutting off a portion of a desired length parallel to the central axis X, a columnar intermediate portion  12  extended coaxially from the control portion  11  and having a smaller diameter, a columnar retention portion  13  extended coaxially from the intermediate portion  12 , having a further smaller diameter, and having the cylindrical spring  20  around it, and a columnar drive portion  14  extended coaxially from the retention portion  13  and having a further smaller diameter. A step  13   s  is formed on the boundary between the intermediate portion  12  and the retention portion  13 . 
     The retention portion  13  has a ring-shaped groove  13   a  formed for the retaining ring  50  to be put on the outer periphery, near the edge on the side of the drive portion. The drive portion  14  has cut faces formed parallel to each other and parallel to the central axis X on both sides of the central axis X and engages with a turning mechanism, which is not shown in the figures, in a housing  41 . With the flat faces  11   a  formed on the control portion  11 , the relative rotational position of the mounting hole of an operation knob, which is not shown in the figures, to be mounted on the control portion  11  can be determined. 
     The cylindrical spring  20  has a plurality of rectangular leaf spring portions  20 A that are arranged at intervals in the circumferential direction on the periphery of a hidden virtual column, as shown in  FIG. 4A , for example, and that extend in the direction of the central axis X, and two connecting bands  20 B that connect the leaf spring portions  20 A at both ends in the circumferential direction. The central area in the direction of the central axis X of each of the leaf spring portions  20 A is curved to project radially outward, forming a curved projection portion  20 Aa. The connecting bands  20 B are separated between one pair of adjacent leaf spring portions  20 A among the plurality of rectangular leaf spring portions  20 A, forming an opening  20 C. 
     The shaft supporter  30  includes a base portion  31  having a square block shape and a cylindrical portion  32  rising at a right angle from the front face of the base portion. The cylindrical portion  32  has a circular through shaft hole  32 A around the central axis X, and a tapered face  32   d  the diameter of which increases outward is formed at the tip of the through shaft hole  32 A. The through shaft hole  32 A is formed at the tip of the cylindrical portion  32  and has a large-diameter shaft hole portion  32   a  the inside diameter of which is larger than the inside diameter of the area into which the intermediate portion  12  of the control shaft  10  is inserted so as to fit, or the outside diameter of the intermediate portion  12 , and a small-diameter shaft hole portion  32   b  with a further smaller inside diameter, into which the retention portion  13  of the control shaft  10  is inserted so as to fit, the inside diameter being larger than the outside diameter of the retention portion  13  and smaller than the outside diameter of the intermediate portion  12 , and a step  32   s  is formed on the boundary between the large-diameter shaft hole portion  32   a  and the small-diameter shaft hole portion  32   b . The back end of the small-diameter shaft hole portion  32   b  is placed next to the edge of the ring-shaped groove  13   a  on the side of the intermediate portion  12  in the state in which the control shaft  10  is attached to the shaft supporter  30 , and the inside diameter of the through shaft hole  32 A is enlarged from the back end of the small-diameter shaft hole portion  32   b  and provides an enlarged shaft hole portion  32   c . In the base portion  31 , a connection space  31 A is formed for connection to the back face, by enlarging the enlarged shaft hole portion  32   c  further. The length of the intermediate portion  12  in the direction of the central axis X is smaller than the length of the large-diameter shaft hole portion  32   a  in the direction of the central axis X, and a ring-shaped spring holding space  33  is formed between the inner periphery of the large-diameter shaft hole portion  32   a  and the outer periphery of the intermediate portion  12  in the state in which the control shaft  10  is inserted deepest into the through shaft hole  32 A. 
     The electrical signal control section  40  has a rectangular parallelepiped shape that includes a single face matching with the quadrilateral back face of the base portion  31 , and includes the housing  41 , which includes a variable resistor or a switch that is turned and driven by the drive portion  14 , a cover  42  that covers the opening of the housing, terminals  43  where electrical signals are input and output, and set screws  44  that secure the housing  41  to the base portion  31 . The cover  42  has a hole  42   a  from which the drive portion  14  is inserted into the housing  41 . An example of a rotary operation type electronic component having a switch as the electrical signal control section  40  is disclosed, for example, in Japanese Patent Application Laid Open No. 2010-218883. Examples of rotary operation type electronic components having a variable resistor as the electrical signal control section  40  are disclosed, for example, in Japanese Patent Application Laid Open No. 2010-186792 or Japanese Patent Application Laid Open No. 2006-147832. As an example of the electrical signal control section  40 , an angle sensor using a magnet and a magnetic sensor that can be turned relatively is disclosed in Japanese Patent Application Laid Open No. H8-236314. 
     The control shaft  10  is locked to the shaft supporter  30  when the ring-shaped groove  13   a  of the retention portion  13  is placed next to and outside the small-diameter shaft hole portion  32   b  and the retaining ring  50  is attached to the ring-shaped groove  13   a , in the state in which the cylindrical spring  20  shown in  FIG. 4A  is mounted to the outer periphery of the retention portion  13  of the control shaft  10  and the control shaft  10  is inserted into the shaft supporter  30 . In that locked state, the spring holding space  33  is formed between the outer periphery of the retention portion  13  and the inner periphery of the large-diameter shaft hole portion  32   a , and the position of the step  13   s  of the control shaft  10  in the direction of the central axis X and the position of the step  32   s  of the through shaft hole  32 A in the direction of the central axis X are determined such that the length of the space in the direction of the central axis X becomes greater than the length of the cylindrical spring  20  stretched flatways in the direction of the central axis X. The drive portion  14  of the control shaft  10  enters the housing  41  of the electrical signal control section  40  through the connection space  31 A in the base portion  31  of the shaft supporter  30 . 
     The cylindrical spring  20  is formed as described below. By forming at regular intervals, in a rectangular metal sheet having spring characteristics, an array of rectangular slits  20 D long in the direction of the shorter side of the metal sheet (hereafter width direction) and parallel to one another, a plurality of rectangular leaf spring portions  20 A connected by two connecting bands  20 B at both ends are formed. All the leaf spring portions  20 A are pressed together to be curved so that the central areas of the leaf spring portions  20 A in their length direction project to the same side with respect to the face of the original metal sheet. The cylindrical spring  20  is obtained by rolling the two connecting bands  20 B connecting the leaf spring portions  20 A in a direction such that the curved areas project radially outward, until the leaf spring portions  20 A located at both ends of the array of leaf spring portions  20 A connected by the two connecting bands  20 B become next to each other. 
     The connecting bands  20 B serve as both end portions  20 Ab of the leaf spring portions  20 A. The ends of the leaf spring portions act as fulcrums, and the curved projecting central areas act as points of application. 
     Since the minimum inside diameter of the cylindrical spring  20  (inside diameter of the connecting bands  20 B) in a free state is set smaller than the outside diameter of the retention portion  13 , when the cylindrical spring  20  is mounted to the retention portion  13 , the opening  20 C between the adjacent leaf spring portions  20 A in both ends of the array is widened resiliently, and the cylindrical spring  20  is held onto the retention portion  13  by the spring force. It is designed that the maximum outside diameter (outside diameter in the central areas of the leaf spring portions  20 A) of the cylindrical spring  20  in that state becomes larger than the inside diameter of the large-diameter shaft hole portion  32   a  of the through shaft hole  32 A. Accordingly, when the control shaft  10  with the cylindrical spring  20  mounted thereto is inserted into the shaft supporter  30 , the leaf spring portions  20 A are deformed resiliently so as to be pressed radially inward by the inner periphery of the large-diameter shaft hole portion  32   a  such that the radial height of the leaf spring portions  20 A with respect to the retention portion  13  is lowered toward the central axis X, and so as to have an increased length of the leaf spring portions  20 A in the direction of the central axis X. This exerts radially opposite pressing forces on the curved projection portions  20 Aa and the both end portions  20 Ab of the leaf spring portions  20 A, generating pressure P 1  between the curved projection portions  20 Aa forming the outer periphery of the leaf spring portions  20 A and the inner periphery of the through shaft hole  32 A and pressure P 2  between the inner periphery of the connecting bands  20 B forming the both end portions  20 Ab of the leaf spring portions  20 A and the outer periphery of the retention portion  13 . Since the latter pressure P 2  includes a pressure at which the cylindrical spring  20  holds the retention portion  13  resiliently, P 1 &lt;P 2 . The connecting bands  20 B are deformed in a ring shape so that the surface of the inner periphery contracts, and the contraction increases the roughness of the surface. On the other hand, the surface of the outer periphery of the leaf spring portions  20 A is curved and expanded, decreasing the surface roughness. As a result, the static frictional force between the leaf spring portions  20 A and the inner periphery of the through shaft hole  32 A becomes smaller than the static frictional force between the connecting bands  20 B and the outer periphery of the retention portion  13 . When the control shaft  10  is rotated, the cylindrical spring  20  rotates together with the control shaft  10  (that is, the cylindrical spring  20  does not rotate relatively with respect to the control shaft  10 ) while rotating slidably on the inner periphery of the through shaft hole  32 A. 
     To increase the torque needed for the turning operation, the friction between the cylindrical spring  20  and the shaft supporter  30  should be increased. According to the present invention, the friction can be increased easily by increasing the number of leaf spring portions  20 A in the cylindrical spring  20  and by increasing the largest possible amount of resilient displacement of the leaf spring portions  20 A (height of the curves of the leaf spring portions  20 A). Since the number of leaf spring portions  20 A and the possible amount of displacement can be selected independently of each other, the high degree of freedom in design makes it easy to design and manufacture small rotary operation type electronic components. 
     [Modifications on Cylindrical Spring] 
       FIG. 4B  shows a first modification of the cylindrical spring  20  in the embodiment shown in  FIGS. 2 and 3 . This modification differs from the one shown in  FIG. 4A  in the following points: A connecting band  20 B is formed by connecting the curved, projecting central areas of leaf spring portions  20 A; and the both end portions  20 Ab of each of the leaf spring portions  20 A are separated from the both end portions  20 Ab of adjacent leaf spring portions  20 A. 
       FIG. 4C  shows a second modification of the cylindrical spring  20 , which differs from the one shown in  FIG. 4A  in the following structure: The connecting bands  20 B are cut off, at one end between one pair of two adjacent leaf spring portions  20 A, from every second pair of two adjacent leaf spring portions in the circumferential direction and are cut off, at another end between the next pair of two adjacent leaf spring portions  20 A, from every second pair of two adjacent leaf spring portions in the circumferential direction. In other words, each of the leaf spring portions  20 A is connected to an adjacent leaf spring portion by the connecting band  20 B alternately at one end or another in the circumferential direction. 
       FIG. 4D  shows a third modification of the cylindrical spring  20 . This modification differs from the one shown in  FIG. 4C  in the following points: The leaf spring portions  20 A are placed diagonally with respect to the direction of the central axis X so that adjacent leaf spring portions  20 A form V shapes; the adjacent leaf spring portions  20 A are connected at one end or another directly, not by the connecting band  20 B. 
     In the embodiment using the cylindrical spring  20  as shown in  FIG. 4A , described with reference to  FIGS. 2 and 3 , the cylindrical spring  20  does not rotate relatively with respect to the control shaft  10  but rotates slidably on the shaft supporter  30 , but on the contrary, the cylindrical spring  20  may not rotate relatively with respect to the shaft supporter  30  and may rotate slidably on the control shaft  10 . This configuration can be implemented by forming fine irregularities on the curved faces of the radially outward projections of the leaf spring portions  20 A of the cylindrical spring  20  to increase the surface roughness, thereby increasing the frictional force between the cylindrical spring  20  and the inner periphery of the through shaft hole  32 A to exceed the frictional force between the cylindrical spring  20  and the control shaft  10 . The same applies to the modifications shown in  FIGS. 4B to 4D . 
       FIG. 5A  shows a fourth modification of the cylindrical spring  20 . This modification differs from the cylindrical spring  20  shown in  FIG. 4A  in that the central areas of the leaf spring portions  20 A of the cylindrical spring  20  are curved to project radially inward, contrary to the ones shown in  FIG. 4A . The rotary operation type electronic component using this modification of the spring is assembled by first placing the cylindrical spring  20  in the large-diameter shaft hole portion  32   a  of the shaft supporter  30  and then putting the control shaft  10  into the through shaft hole  32 A of the shaft supporter  30  so that the retention portion  13  of the control shaft  10  is inserted into the cylindrical spring  20 . Accordingly, the outer peripheries of the connecting bands  20 B of the cylindrical spring  20  resiliently come into contact with the inner periphery of the large-diameter shaft hole portion  32   a  of the shaft supporter  30 , and the curved projection portions  20 Aa resiliently come into contact with the outer periphery of the retention portion  13  of the control shaft  10 . 
       FIG. 5B  shows a fifth modification of the cylindrical spring  20 . This modification differs from the cylindrical spring  20  shown in  FIG. 4B  in that the central areas of the leaf spring portions  20 A connected by the connecting band  20 B are curved and project radially inward, contrary to the ones shown in  FIG. 4B . 
       FIG. 5C  shows a sixth modification of the cylindrical spring  20 . This modification differs from the cylindrical spring  20  shown in  FIG. 4C  in that the central areas of the leaf spring portions  20 A are curved and project radially inward, contrary to the ones shown in  FIG. 4C . 
       FIG. 5D  shows a seventh modification of the cylindrical spring  20 . This modification differs from the cylindrical spring  20  shown in  FIG. 4D  in that the central areas of the leaf spring portions  20 A are curved and project radially inward, contrary to the ones shown in  FIG. 4D . 
     In the modification shown in  FIG. 5A , to secure the cylindrical spring  20  to the control shaft  10  and to rotate the cylindrical spring  20  slidably on the inner periphery of the through shaft hole  32 A while the control shaft  10  is turning, the surface roughness of the inner peripheries of the curved radially inward projections of the leaf spring portions  20 A and/or the outer periphery of the retention portion  13  of the control shaft  10  should be increased. On the contrary, to secure the cylindrical spring  20  to the shaft supporter  30  and to rotate the retention portion  13  of the control shaft  10  slidably on the cylindrical spring  20 , the surface roughness of the outer peripheries of the connecting bands  20 B and/or the inner periphery of the large-diameter shaft hole portion  32   a  should be increased. The same applies to the modifications shown in  FIGS. 5B to 5D  (in  FIG. 5D , the mutually connected end portions of adjacent leaf spring portions  20 A correspond to the connecting bands  20 B in the other modifications). 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to variable resistors or switches in portable wireless devices, for example.