Patent Publication Number: US-2009231072-A1

Title: Stalk switch device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     The present invention contains subject matter related to and claims prior to Japanese Patent Application No. 2008-064607 filed in the Japanese Patent Office on Mar. 13, 2008, the entire contents of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a stalk switch device which is disposed near a steering wheel of a car to be used for switching of a headlamp, a windscreen wiper, or the like. 
     2. Related Art 
     In general, a pair of stalk switch devices is disposed on both sides, that is, left and right sides of a housing fixed to a steering column or the like, thereby constituting a combination switch. Particularly, a configuration in which switching of turn signals, beams of headlamps, a windscreen wiper, and the like is performed by moving a cylindrical housing of the stalk switch device upwards, downwards, forwards, or backwards, and on/off switching of the headlamps is performed by rotating about the housing an operating ring supported by the housing, has been widely known. 
     In order for the stalk switch device to be implemented with a miniaturization of the entire device and to simplify the structure, a configuration in which a circuit board, which extends in a longitudinal direction of a cylindrical housing, is disposed in the housing and a rotary switch mounted on the circuit board is rotated along with the rotation of an operating ring is known (for example, refer to U.S. Pat. No. 5,905,237 which corresponds to JP-A-10-269898). In this conventional example, a first gear having a number of teeth along a rotation direction of the operating ring is formed integrally with the operating ring, a spindle of a second gear engaged with the teeth of the first gear is perpendicular to an axial direction of the operating ring, and an end portion of the spindle is fitted on a rotation shaft of the rotary switch as a spline. When the operating ring is rotated, the first gear rotates the rotation shaft of the rotary switch with the second gear and the spindle interposed therebetween, and an electric signal corresponding to the rotation of the operating ring is output from the rotary switch. In addition, a push switch mounted on the circuit board of the housing is pressed by an operating key exposed from an opening of the housing in order to be operated. When the configuration in which the rotation of the operating ring is transmitted to the second gear with the first gear interposed therebetween, both of the rotary switch and the push switch and the like can be provided on the single circuit board extending in the longitudinal direction of the housing, so that the miniaturization of the entire device and the simplification of the structure can be easily achieved. 
     However, in the aforementioned stalk switch device, upon rotation of the operating ring, switching is performed by sliding a wiper (movable contact) mounted to a rotor portion formed integrally with the rotation shaft of the rotary switch with respect to a contact pattern of a stator. Therefore, the contact is abraded by the repeated rotation of the operating ring as time elapses, and there are concerns about conduction failures caused by oxidization or sulfurization of the contact. 
     SUMMARY 
     A stalk switch device includes: a cylindrical housing; an operating ring, which is supported to rotate with respect to the housing; a driven member, which is driven in the housing by the rotation of the operating ring; a permanent magnet fixed to the driven member; a circuit board disposed in the housing in a longitudinal direction of the housing; and a magnetic sensor mounted on the circuit board, wherein a change in magnetic field in the housing caused by the movement of the permanent magnet, which moves along with the driven member is detected by the magnetic sensor. 
     In the stalk switch device according to the aspect of the invention, when the operating ring is rotated, the driven member in the housing is driven, and the permanent magnet fixed to the driven member is moved. Therefore, the magnetic field in the housing generated by the movement of the permanent magnet is changed, and the change in magnetic field results in a change in electric resistance of the magnetic sensor. Accordingly, a rotation position of the operating ring can be detected on the basis of the change in resistance of the magnetic sensor, and upon the rotation of the operating ring, without sliding a wiper (movable contact) in a contact pattern, switching can be performed. As a result, a conduction failure (contact failure) caused by abrasion or oxidization of a contact point does not occur in the switching device of the operating ring, and a longer life-span of the stalk switch device can be implemented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view illustrating a stalk switch device according to a first embodiment of the invention. 
         FIG. 2  is a perspective view illustrating an internal structure of the stalk switch device according to the first embodiment, where portions thereof are omitted. 
         FIG. 3  is a sectional view illustrating a main portion of  FIG. 2 . 
         FIG. 4  is a plan view illustrating a cylindrical rotating member according to the first embodiment. 
         FIGS. 5A to 5C  are explanatory views illustrating a change in position of a permanent magnet with a rotation of the cylindrical rotating member according to the first embodiment. 
         FIG. 6  is a circuit diagram illustrating a giant magnetoresistance (GMR) sensor illustrated in  FIG. 5 . 
         FIG. 7  is an explanatory view illustrating a relationship between a movement distance of the permanent magnet illustrated in  FIG. 5  and an output voltage of the GMR sensor. 
         FIG. 8  is an exploded perspective view illustrating a stalk switch device according to a second embodiment of the invention, where a housing and other portions are omitted. 
         FIGS. 9A to 9C  are explanatory views illustrating operations of a rotating driving member and a slider illustrated in  FIG. 8 . 
         FIGS. 10A to 10C  are explanatory views illustrating a change in position of a permanent magnet corresponding to  FIGS. 9A to 9C . 
         FIG. 11  is an explanatory view illustrating a relationship between a position of the permanent magnet illustrated in  FIGS. 10A to 10C  and an output voltage of a GMR sensor. 
         FIG. 12  is an explanatory view illustrating a modified example of an engagement groove provided to the rotating driving member according to the second embodiment. 
         FIG. 13  is an exploded perspective view illustrating a stalk switch device according to a third embodiment of the invention, where a housing and other portions are omitted. 
         FIG. 14  is an explanatory view illustrating a main portion of the stalk switch device according to the third embodiment. 
         FIG. 15  is an exploded perspective view illustrating a stalk switch device according to a fourth embodiment of the invention, where a housing and other portions are omitted. 
         FIG. 16  is an explanatory view illustrating a main portion of the stalk switch device according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the invention will now be described with reference to the accompanying drawings.  FIG. 1  is an exploded perspective view illustrating a stalk switch device according to a first embodiment of the invention. FIG.  2  is a perspective view illustrating an internal structure of the stalk switch device according to the first embodiment, where portions thereof are omitted.  FIG. 3  is a sectional view illustrating a main portion of  FIG. 2 .  FIG. 4  is a plan view illustrating a cylindrical rotating member according to the first embodiment.  FIGS. 5A to 5C  are explanatory views illustrating a change in position of a permanent magnet with a rotation of the cylindrical rotating member according to the first embodiment.  FIG. 6  is a circuit diagram illustrating a giant magnetoresistance (GMR) sensor illustrated in  FIG. 5 .  FIG. 7  is an explanatory view illustrating a relationship between a movement distance of the permanent magnet illustrated in  FIG. 5  and an output voltage of the GMR sensor. 
     The stalk switch device illustrated in  FIGS. 1 to 7  includes a cylindrical housing  1  constituting a portion of a combination switch, a holder  2  which is included and retained in the housing  1 , a circuit board  3  retained on the holder  2 , an operating knob  4  which is movably supported by the holder  2  to be moved at a front end of the housing  1 , a rotating member  5  to which a permanent magnet  6  is fixed to be rotatably supported by the holder  2 , an operating ring  7  of which a portion is exposed from the housing  1  to be rotatably operated, a cylindrical rotating member  8  which is rotatably supported by the holder  2  and formed integrally with the operating ring  7 , a permanent magnet  9  fixed to an outer peripheral surface of the cylindrical rotating member  8 , an operating key  10  which is liftably and lowerably supported by the housing  1  to be pushed, and the like. In addition, on the circuit board  3 , giant magnetoresistance sensors  11  and  12  as magnetic sensors for detecting a change in magnetic field inside the housing caused by movement of the permanent magnets  6  and  9 , and a push switch not shown which is driven at the time of pushing the operating key  10  are mounted. Hereinafter, the giant magnetoresistance sensor is abbreviated to the GMR sensor. 
     The housing  1  is shaped as a cylindrical member constituted by a casing  15  having a lower opening and a cover  16  for covering the lower opening of the casing  15 . The casing  15  and the cover  16  are integrated by snap-fastening. A longitudinal front end portion of the casing  15  is provided with an opening not shown, and the operating knob  4  is exposed from the opening. At portions of the casing  15  and the cover  16  facing each other, openings  15   a  and  16   a  are formed, respectively, and the openings  15   a  and  16   a  expose portions of the operating ring  7 . In addition to the opening  15   a,  the casing  15  is provided with an opening  15   b,  and the opening  15   b  exposes the operating key  10 . 
     The holder  2  is a long member extending in a longitudinal direction of the housing  1  and fixed to the casing  15  by a screw  17 . The holder  2  is provided with a half-cylindrical portion  2   a,  and the cylindrical rotating member  8  is engaged with an outer surface of the half-cylindrical portion  2   a  to be rotatably retained. In the half-cylindrical portion  2   a,  a metallic ball  13  to be engaged with and released from a click recess  8   a  of the cylindrical rotating member  8 , and a spring  14  for elastically biasing the metallic ball  13 , are retained. The holder  2  is provided with locking protrusions  2   b.  As the locking protrusions  2   b  retain the circuit board  3 , the circuit board  3  can extend in the longitudinal direction of the housing  1 . 
     The operating knob  4  is attached to the front end portion of the holder  2  by snap-fastening to be movably supported. The operating knob  4  is provided with a cylindrical portion  4   a  protruding inside the housing  1  and a driving protrusion  4   b.  As a spring  18  stored in the cylindrical portion  4   a  elastically biases a pressing element  19 , the pressing element  19  elastically contacts to a cam face  5   a  of the rotating member  5 . In addition, the driving protrusion  4   b  of the operating knob  4  is engaged with a driven portion  5   b  of the rotating member  5 . The rotating member  5  is rotatably supported by the holder  2 , and to a shaft portion  5   c  of the rotating member  5 , the disc-shaped permanent magnet  6  facing the GMR sensor  11  with the circuit board  3  interposed therebetween, is fixed by press-fitting or adhesive-bonding. In addition, when the operating knob  4  is moved, the rotating member  5  is rotated with the driving protrusion  4   b  interposed therebetween, and the permanent magnet  6  formed integrally with the shaft portion  5   c  is correspondingly rotated. The rotation of the permanent magnet  6  results in a change in magnetic field in the housing  1 , and an electrical resistance of the GMR sensor  11  is correspondingly changed. 
     Therefore, on the basis of the change in resistance of the GMR sensor  11 , the moved position of the operating knob  4  can be detected. Accordingly, upon moving of the operating knob  4 , without sliding a wiper (movable contact) in a contact pattern, switching can be performed. The permanent magnet  6  is magnetized so that the one edge portion with respect to a bisector passing through the center as the axis of symmetry serves as a north pole, and the other edge portion serves as a south pole. In addition, when the operating knob  4  is moved, the pressing element  19  moves along the cam face  5   a  of the rotating member  5 . Here, when the pressing element  19  goes over a protruding surface of the cam face  5   a,  a click feel occurs. 
     The operating ring  7  is fitted to an outer surface of the cylindrical rotating member  8  to be integrated, and the cylindrical rotating member  8  is rotatably retained by the half-cylindrical portion  2   a  of the holder  2 . For a peripheral wall of the cylindrical rotating member  8 , an inner surface is provided with a click recess  8   a,  and an outer surface is provided with a notch  8   b.  The metallic ball  13  that is elastically biased by the spring  14  can be engaged with and disengaged from the click recess  8   a,  and the disc-shaped permanent magnet  9  is fixed to the notch  8 b by press-fitting or adhesive-bonding. The permanent magnet  9  is magnetized so that the planar section on the side facing the circuit board  3  serves as a north pole and the planar section on the other side serves as a south pole. In addition, as illustrated in  FIG. 3 , a side portion of the permanent magnet  9  faces the GMR sensor  12 . When the operating ring  7  is rotated, the cylindrical rotating member  8  driven by the operating ring  7  is integrally rotated. Therefore, as illustrated in  FIG. 5 , the permanent magnet  9  moves in an arc path with respect to the GMR sensor  12 . As a result, the movement of the permanent magnet  9  results in a change in magnetic field in the housing  1 , and an electrical resistance of the GMR sensor  12  is correspondingly changed. Therefore, on the basis of the change in resistance of the GMR sensor  12 , the rotation position of the operating ring  7  can be detected. Accordingly, upon the rotation of the operating ring  7 , without sliding the wiper (movable contact) in the contact pattern, switching can be performed. In addition, upon the rotation of the operating ring  7 , as the cylindrical rotating member  8  rotates, the metallic ball  13  is engaged with or disengaged from the click recess  8   a,  and a click feel occurs. 
     The GMR sensor  12  is described in detail. The GMR sensor  12  is configured such that  4  GMR elements each of which is formed by stacking a pinned magnetic layer and a free magnetic layer with a nonmagnetic intermediate layer interposed therebetween are connected to constitute a bridge circuit illustrated in  FIG. 6  as a package. Specifically, arrows in  FIG. 6  represent magnetization directions of the pinned magnetic layers of the GMR elements. Here, a side portion of the permanent magnet  9  faces the GMR sensor  12 . Therefore, when the permanent magnet  9  is moved in an arc path as illustrated in  FIG. 5 , an external magnetic field in the housing  1  is changed by the movement of the permanent magnet  9 , the magnetization direction of the free magnetic layer of each GMR element is changed, and correspondingly the electric resistance of the GMR sensor  12  is changed. As a result, in a state where a predetermined voltage Vdd is applied to the GMR sensor  12 , an output voltage (V 1 -V 2 ) is changed depending on a position of the permanent magnet  9 , and a relationship of “movement distance of permanent magnet-output voltage of GMR sensor” as illustrated in  FIG. 7  can be obtained. Therefore, on the basis of the output voltage shown as a substantially straight line enclosed by a dash line of  FIG. 7 , the rotation position of the operating ring  7  corresponding to each operating state of  FIGS. 5A to 5C  can be detected. 
     Specifically, when the operating ring  7  is not rotated, the permanent magnet  9  is disposed at a position illustrated in  FIG. 5B . Here, since the magnetization direction of the free magnetic layer is perpendicular to that of the pinned magnetic layer in each GMR element of the GMR sensor  12 , the electrical resistances of the GMR elements are equal to each other, and the output voltage from the GMR sensor  12  becomes zero. However, when the operating ring  7  is rotated such that the permanent magnet  9  is disposed at a position illustrated in  FIG. 5A  or  FIG. 5C , since the electrical resistance of each GMR element of the GMR sensor  12  is changed depending on the magnetization direction of the pinned magnetic layer, the output voltage from the GMR sensor  12  is also changed to a predetermined minus value or a predetermined plus value according to the rotation direction of the operating ring  7 . Therefore, the change in position of the permanent magnet  9  caused by the rotation of the operating ring  7  can be detected by the GMR sensor  12 , and switching according to the rotation of the operating ring  7  can be performed. 
     When the operating key  10  is pressed, a push switch not shown on the circuit board  3  is driven, and switching can be performed. However, the invention relates to the stalk switch device having the operating ring  8  that can be rotated with respect to the housing  1 , and a switching mechanism using the operating key  10  or the operating knob  4  is not directly related to the invention, so that a detailed description thereof is omitted. 
     As described above, in the stalk switch device according to the embodiment, the permanent magnet  9  is fixed to the cylindrical rotating member  8  which is rotated along with the operating ring  7 , and the change in magnetic field of the permanent magnet  9  caused by the rotation of the cylindrical rotating member  8  is detected by the GMR sensor  12 . Therefore, on the basis of the change in resistance of the GMR sensor  12 , the rotation position of the operating ring  7  can be detected. Accordingly, upon the rotation of the operating ring  7 , without sliding the wiper (movable contact) in a contact pattern, switching can be performed. As a result, a conduction failure (contact failure) caused by abrasion or oxidization of a contact point does not occur, and a longer life-span of the stalk switch device can be implemented. Moreover, according to the embodiment, the change in magnetic field of the permanent magnet  6  upon the moving of the operating knob  4  is detected by the GMR sensor  11  to perform switching. In this aspect, avoiding the contact failure and the longer life-span can be implemented. 
     In the stalk switch device according to the embodiment, after mounting the operating ring  7 , the cylindrical rotating member  8 , and the circuit board  3  to the holder  2  fixed to the casing  15 , this half-finished product is included in the housing  1  (the casing  15  and the cover  16 ) to assemble the stalk switch device. Therefore, the assembling process can be easily performed. 
     According to the first embodiment, the housing  1  is constituted by combining the casing  15  and the cover  16 . However, the housing  1  may also be formed in one body into a cylindrical shape in advance. 
     In addition, as described above, the invention relates to the stalk switch device having the operating ring  7  which can be rotated with respect to the housing  1 , so that the operating knob  4  and the operating key  10  can be properly omitted. 
       FIG. 8  is an exploded perspective view illustrating a stalk switch device according to a second embodiment of the invention, where a housing and other portions are omitted.  FIGS. 9A to 9C  are explanatory views illustrating operations of a rotating driving member and a slider illustrated in  FIG. 8 .  FIGS. 10A to 10C  are explanatory views illustrating a change in position of a permanent magnet corresponding to  FIGS. 9A to 9C .  FIG. 11  is an explanatory view illustrating a relationship between a moving stroke of the permanent magnet illustrated in  FIGS. 10A to 10C  and an output voltage of a GMR sensor.  FIG. 12  is an explanatory view illustrating a modified example of an engagement groove provided to the rotating driving member according to the second embodiment. Like reference numerals denote like elements corresponding to  FIG. 1 , so that a detailed description thereof is omitted. 
     The stalk switch device according to the second embodiment includes a cylindrical rotating driving member  20  which is rotated along with the operating ring  7 , and a slider  21  which is driven by the rotating driving member  20  to move linearly, instead of the aforementioned cylindrical rotating member  8 . The stalk switch device of the second embodiment is different from that of the first embodiment in that the change in magnetic field in the housing  1  caused by the movement of the permanent magnet  9  fixed to the slider  21  is detected by the GMR sensor  12 . A peripheral wall of the rotating driving member  20  is provided with an engagement groove  20   a  that is a long hole extending in a spirally inclined direction, and an inner surface of the rotating driving member  20  is provided with a click recess  20   b  having the same shape as the click recess  8   a.  In addition, the slider  21  is provided with an engagement protrusion  21   a  engaged with the engagement groove  20   a,  and as the rotating driving member  20  rotates along with the operating ring  7 , the engagement protrusion  21   a  slides along an inner wall of the engagement groove  20   a.  Accordingly, the rotation movement is translated to the linear movement, and the slider  21  moves along the longitudinal direction of the circuit board  3 . Therefore, as in the first embodiment, the change in magnetic field caused by the movement of the permanent magnet  9  is detected by the GMR sensor  12 , and therefore the rotation position of the operating ring  7  can be detected. 
     Specifically, when the operating ring  7  is not rotated, as illustrated in  FIG. 10B , a side portion of the permanent magnet  9  faces the GMR sensor  12 , and the output voltage from the GMR sensor  12  becomes zero. However, when the operating ring  7  is rotated and the permanent magnet  9  is moved to a position illustrated in  FIG. 10A  or  10 C, the output voltage from the GMR sensor  12  is changed to a predetermined minus value or a predetermined plus value depending on the rotation direction of the operating ring  7 . Therefore, the change in position of the permanent magnet  9  which moves linearly as the operating ring  7  is rotated can be detected by the GMR sensor  12 , and switching based on the rotation of the operating ring  7  can be performed. In addition,  FIGS. 9A ,  9 B, and  9 C correspond to  FIGS. 10A ,  10 B, and  10 C, respectively. Here, In  FIGS. 9A and 9C , the engagement protrusion  21   a  of the slider  21  is disposed at a different end of the engagement groove  20   a,  and the engagement protrusion  21   a  in  FIG. 10B  is disposed at the center position of the engagement groove  20   a.    
     In addition, a relationship between the position of the permanent magnet  9  with respect to the GMR sensor  12  and the output voltage from the GMR sensor  12  which detects the change in magnetic field caused by the movement of the permanent magnet  9  is shown as a curve having the same shape as the characteristic curve in  FIG. 7  used in the first embodiment. However, specifically, as illustrated in  FIG. 11 , although the positions of the permanent magnet  9  with respect to the GMR sensor  12  are the same, the output voltages have a width somehow and data spread is shown. The data spread is caused by an environmental temperature in use, a position deviation, a deviation in characteristics between the permanent magnet  9  and the GMR sensor  12 , and the like, and varies in the range from data Dmax to data Dmin. Therefore, according to the embodiment, by rotating the operating ring  7  that rotates along with the rotating driving member  20  to  3  positions disposed at a predetermined angle in a peripheral direction, switching can be performed. Specifically, when the operating ring  7  is rotated at the predetermined angle, the rotating driving member  20  is rotated from the state of  FIG. 9B  to the state of  FIG. 9A  or  9 C, and the permanent magnet  9  linearly moves from the position of  FIG. 10B  to the position of  FIG. 10A  or  10 C. When the positions of the permanent magnet  9  of  FIGS. 10A ,  10 B, and  10 C are denoted by S 1 , S 0  (the central position in the movement range of the permanent magnet), and S 2 , respectively, 
     the output voltage A (A is a value having a width) corresponding to the position S 1 , the output voltage B corresponding to the position S 0 , the output voltage C corresponding to the position S 2  do not overlap with each other as illustrated in  FIG. 11 . Accordingly, the 3 positions of the permanent magnet  9  can be identified on the basis of the output voltages, and the 3 rotation positions of the operating ring can be accurately detected. In addition, according to the embodiment, in the state of  FIG. 9B , the center of the GMR sensor  12  and the center of the permanent magnet  9  are aligned. In  FIGS. 10A ,  10 B, and  10 C, the positions S 0 , S 1 , S 2  of the permanent magnet are disposed at predetermined intervals, respectively. 
     However, when the operating ring  7  is rotated to  5  positions disposed at predetermined angles in the peripheral direction, as illustrated in  FIG. 11 , the permanent magnet  9  slidably moves to a position S 1 , a position X 1  (in the middle of the positions S 1  and S 0 ), a position S 0 , a position X 2  (in the middle of the positions S 0  and S 2 ), and a position S 2 , respectively. However, as the permanent magnet  9  becomes distant from the position S 0 , the rate of change of the output voltage of the GMR sensor  12  decreases. Accordingly, the output voltages at the positions partially overlap, the  5  positions of the permanent magnet  9  cannot be identified on the basis of the output voltages, and  5  rotation positions of the operating ring  7  cannot be detected. Specifically, in  FIG. 11 , the output voltage A corresponding to the position S 1  partially overlaps with the output voltage D corresponding to the position X 1 , and the output voltage E corresponding to the position X 2  partially overlaps with the output voltage C corresponding to the position S 2 . Therefore, the position of the permanent magnet  9  cannot be identified on the basis of the output voltages, and as a result, the 5 rotation positions of the operating ring  7  cannot be detected. 
     Therefore, as illustrated in a modified example of  FIG. 12 , angles of portions of the engagement groove  20   a  of the rotating driving member  20  with respect to the rotation axis Z of the operating ring  7  are set as follows. A region (central region) C 0  of a central portion corresponding to the position S 0  and the vicinities of the position S 0  is at an angle of θ 1 , and other regions, that is, regions (both side regions) C 1  and C 2  corresponding to the positions S 1  and S 2  and the vicinities of the positions S 1  and S 2  are at an angle of θ 2 . Here, the engagement groove  20   a  is formed such that the angle θ 1  corresponding to the region C 0  is greater than the angle θ 2  corresponding to the regions C 1  and C 2 . Accordingly, although there is a little spread of the output voltage from the GMR sensor  12 , switching can be performed at the 5 movement positions of the slider  21 . Specifically, the engagement groove  20   a  is formed such that the movement distance of the slider  21  in the region C 0  when the operating ring  8  is rotated at a predetermined angle is smaller than that (angle) in the regions C 1  and C 2 . Accordingly, as illustrated in  FIG. 11 , a position of the permanent magnet  9  disposed between the positions S 0  and S 2  when the operating ring  7  is rotated becomes a position S 4  closer to the position S 0  than the position X 2 , and a position of the permanent magnet  9  disposed between he positions S 0  and S 1  becomes a position S 3  closer to the position S 0  than the position X 1 . Therefore, in  FIG. 11 , the output voltage B corresponding to the position S 0 , the output voltage A corresponding to the position S 1 , the output voltage F corresponding to the position S 3 , the output voltage G corresponding to the position S 4 , and the output voltage C corresponding to the position S 2  can be set so as not to overlap with each other. In other words, by employing the construction of  FIG. 12 , as the position of the permanent magnet  9  when the operating ring  7  is rotated at the predetermined angles, among a plurality of positions which are in the regions C 1  and C 2  (both side regions) having smaller rates of change of the output voltage of the GMR sensor  12  and adjacent to the other sides, positions of the permanent magnet close to the central region C 0  are moved to the central region C 0  or to the vicinities, so that the output voltages of the GMR sensors at the positions do not overlap. Therefore, by using the engagement groove  20  in the modified example of  FIG. 12 , although there is the spread of the output voltage from the GMR sensor  12 , the permanent magnet  9  can be identified on the basis of the output voltages, and the  5  rotation positions of the operating ring  7  can be accurately detected. 
       FIG. 13  is an exploded perspective view illustrating a stalk switch device according to a third embodiment of the invention, where a housing and other portions are omitted.  FIG. 14  is an explanatory view illustrating a main portion of the stalk switch device according to the third embodiment. Like reference numerals denote like elements corresponding to  FIG. 1 , so that a detailed description thereof is omitted. 
     The stalk switch device of the third embodiment is different from that of the first embodiment in that the stalk switch device of the third embodiment has instead of the cylindrical rotating member  8 , a driving gear  22  which rotates along with the operating ring  7 , and a rotation shaft member  23  which is driven to rotate by the driving gear  22 , and a change in magnetic field of the permanent magnet  24  fixed to the rotation shaft member  23  is detected by the GMR sensor  12 . The driving gear  22  has a number of teeth  22   a  along the rotation direction of the operating ring  7 , and the operating ring  7  is fitted to the driving gear  22 . The rotation shaft member  23  includes a spindle portion  23   a  which extends in a direction perpendicular to an axial direction of the operating ring  7  to have an end portion to which the permanent magnet  24  is fixed, and a gear portion  23   b  which is fitted to the spindle portion  23   a  and engaged with the teeth  22   a  of the driving gear  22 . As illustrated in  FIG. 14 , a planar section of the permanent magnet  24  faces the GMR sensor  12 , and the permanent magnet  24  is magnetized so that the one edge with respect to a bisector passing through the center as the axis of symmetry serves as a north pole, and the other edge serves as a south pole. When the driving gear  22  is rotated along with the operating ring  7 , the spindle portion  23   a  is rotated along with the gear portion  23   b  interposed therebetween, and a change in the magnetic field caused by the rotation of the permanent magnet  24  fixed to the spindle portion  23   a  is detected by the GMR sensor  12 , thereby detecting the rotation position of the operating ring  7 . 
       FIG. 15  is an exploded perspective view illustrating a stalk switch device according to a fourth embodiment of the invention, where a housing and other portions are omitted.  FIG. 16  is an explanatory view illustrating a main portion of the stalk switch device according to the fourth embodiment. Like reference numerals denote like elements corresponding to  FIGS. 13 and 14 , so that a detailed description thereof is omitted. 
     The stalk switch device of the fourth embodiment has a similar basic configuration to that of the third embodiment and is different therefrom in that the magnetization direction of the permanent magnet  25  fixed to the spindle portion  23   a  of the rotation shaft member  23  and the position of the GMR sensor  12  for detecting the change in magnetic field of the permanent magnet  25  are changed. Specifically, according to the embodiment, the north pole and the south pole are alternately magnetized in the peripheral direction of the permanent magnet  25 , and the GMR sensor  12  is disposed to be adjacent to an outer peripheral surface of the permanent magnet  25 . In addition, when the driving gear  22  is rotated along with the operating ring  7 , the spindle portion  23   a  is rotated along with the gear portion  23   b  interposed therebetween, and the change in magnetic field caused by the rotation of the permanent magnet  25  fixed to the spindle portion  23   a  is detected by the GMR sensor  12 , thereby detecting the rotation position of the operating ring  7 .