Patent Publication Number: US-6670567-B1

Title: Rotary switch mechanism for operation panel

Description:
TECHNICAL FIELD 
     The present invention relates to a rotary switch mechanism for an operation panel that may be utilized in, for instance, an air-conditioning system for vehicles. 
     BACKGROUND ART 
     A rotary switch in the related art disclosed in Japanese Unexamined Patent Publication No. H 9-288934 comprises a switch board having a plurality of switch contact points, an elastic pressure application plate that includes a plurality of arm units and holds contact portions provided at the individual arm units on the switch contact points and a rotating body that is rotatably provided on the switch board and includes depressing portions provided at the lower surface of the switch board to come in contact with the arm units and thus push down the arm units. 
     It is necessary to secure ample space in conjunction with a rotary switch utilized in an air-conditioning system for vehicles in the related art since push switches and the indicator light source are sometimes provided on the printed board where the contact points of the rotary switch are located. For this reason, a problem arises with regard to utilization of the rotary switch in the quoted reference above in that the space in which push switches, the indicator light source and the like can be provided becomes limited since a large area of the printed board is occupied by the contact points. In addition, since the knob of the rotary switch is firmly secured to the contact points, it is difficult to accurately align the position of the knob hole formed at the operation panel with the position of the knob secured to the printed board, which gives rise to a problem with regard to the installation at the printed board. 
     DISCLOSURE OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a rotary switch mechanism for an operation panel that allows ample space on a printed board, facilitates the design process for designing electronic parts and the like on the printed board and achieves good attachability for the switch knob. 
     In order to achieve the object described above, according to the present invention, on an operation panel with a plurality of mode settings, which allows one of the plurality of mode settings to be selected by selecting one of the positions corresponding to the plurality of mode settings, a cylindrical rotary knob that includes a portion projecting out at the front surface of the operation panel and is capable of stopping at each of the positions corresponding to the plurality of mode settings, drive pieces formed at specific phases at the circumferential edge at the end of the rotary knob located further inward at the operation panel that move along the circumference of the rotary knob as the rotary knob rotates and a detection switch that detects a passage of and the direction of the passage of the drive pieces are provided. 
     Thus, with the present invention, which simply requires the drive pieces to be provided over specific intervals at the circumferential edge at the end of the rotary knob located further inward at the operation panel and the detection switch for detecting a passage of and the direction of the passage of the drive pieces to be provided within or in the vicinity of the range of the movement of the drive pieces, e.g., on the printed board, ample space is assured on the printed board, thereby solving the problem discussed earlier. 
     In addition, the drive pieces formed at the rotary knob may project out along the radius of the rotary knob or they may project out along the axial direction from the external circumferential edge at the end of the rotary knob. It is desirable that the detection switch be constituted of a physical detection switch having a movable piece that is capable of moving along a direction corresponding to the direction of the passage of the drive pieces, and such a movable piece may be set either parallel to the drive pieces or perpendicular to the drive pieces. 
     The present invention is further characterized in that an intermediate transmission mechanism that converts the intervals between the individual drive pieces to a distance required for the movement of the movable piece is provided between the drive pieces and the movable piece. For instance, if the rotary knob has a smaller diameter and thus the intervals between the drive pieces, too, are smaller, the movement of the movable piece at the detection switch over such a small distance between the drive pieces cannot be detected. In such a case, by providing the intermediate transmission mechanism, it becomes possible to allow the movable piece of the detection switch to move over a large enough distance to allow a detection thereof. 
     In addition, the intermediate transmission mechanism should comprise a first arm that is caused to move by the drive pieces, a second arm that causes the movable piece to move and a supporting point portion provided between the first arm and the second arm, with the length of the first arm and the length of the second arm set in correspondence to the ratio of the interval between the drive pieces and the distance required for the movement of the movable piece. The first arm and the second arm may be set on a single straight line, may be set perpendicular to each other or may be set at a specific angle to each other. The drive pieces may each be constituted of a tooth of a drive gear formed at the end of the rotary knob and the intermediate transmission mechanism may be constituted of a working gear which interlocks with the drive gear and rotates as the drive pieces move and a working portion that is secured to the working gear and rotates as the working gear rotates to cause the movable piece to move, with the ratio of the number of teeth of the drive gear and the number of teeth of the drive gear and the number of the working portions set in correspondence to the ratio of the pitch at the drive gear and the distance required for the movement of the movable piece. 
     Furthermore, the rotary switch mechanism may include a plurality of detection switches positioned at phases different from the phases of the drive pieces and the individual detection switches may sequentially detect the passage of and the direction of the passage of the drive pieces while the drive pieces move over a distance equivalent to the interval between the individual drive pieces. By adopting this structure, in which a plurality of detection switches are positioned at phases different from the phases of the drive pieces, the individual detection switches can sequentially detect the passage of and the direction of the passage of the drive pieces while the drive pieces move over the distance equivalent to the interval between the drive pieces, i.e., while they pass over a single pitch of the drive pieces and a desired number of signals representing the rotational angle of the rotary knob corresponding to the number of drive pieces can be generated even when the intervals between the individual drive pieces is set large enough to allow the required movement of the movable piece. 
     While the detection switch is constituted of a physical detection switch that detects the passage of and the direction of the passage of the drive pieces by detecting the movement of the working piece in the example described above, the detection switch according to the present invention may be constituted of an optical detection switch having a light emitting element and a light receiving element, which detects the passage of and the direction of the passage of the drive pieces by detecting a change of light while the drive pieces pass between the light emitting element and the light receiving element instead. 
     Moreover, if a light emitting source for the indicator unit is provided at the center of the rotary knob, only the light receiving element may be provided to detect the passage of and the direction of the passage of the drive pieces. In addition, the detection switch may take on any structure as long as it is capable of detecting the passage of and the direction of the passage of the drive pieces through detection of a change occurring in an electromagnetic wave, an acoustic wave, an electrical field, a magnetic field or the like instead of a change of a visible light beam as described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial front view of an example of an operation panel achieved in an embodiment of the present invention; 
     FIG. 2 is a sectional view of the operation panel shown in FIG. 1; 
     FIG. 3 is a perspective showing the cylindrical drive unit and the detection switch achieved in a first embodiment; 
     FIG. 4 is a sectional view of the operation panel achieved in a second embodiment; 
     FIG. 5 is a perspective showing the cylindrical drive unit and the detection switch achieved in a third embodiment; 
     FIG. 6 is a sectional view of the operation panel achieved in the third embodiment; 
     FIG. 7 is a sectional view of the operation panel achieved in a fourth embodiment; 
     FIG. 8 is a perspective showing the cylindrical drive unit and the detection switch achieved in a fifth embodiment; 
     FIG. 9 is a perspective showing the cylindrical drive unit and the detection switch achieved in a sixth embodiment; 
     FIG. 10 is a perspective showing the cylindrical drive unit achieved in a seventh embodiment; 
     FIG. 11 is a perspective showing the cylindrical drive unit achieved in an eighth embodiment; 
     FIG. 12 illustrates the intermediate transmission unit achieved in a ninth embodiment; 
     FIG. 13 illustrates the intermediate transmission unit achieved in a tenth embodiment; 
     FIG. 14 illustrates the intermediate transmission unit achieved in an eleventh embodiment; 
     FIG. 15 illustrates the cylindrical drive unit, the first detection switch and the second detection switch achieved in a twelfth embodiment; and 
     FIG. 16 is a sectional view showing an example of a detection switch in the known art. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following is an explanation of the preferred embodiments of the present invention, given in reference to the drawings. 
     FIGS. 1 and 2 illustrate an example of an operation panel for an air-conditioning system. At this operation panel  1 , a rotary switch mechanism  3  projecting out at the front surface of a case  2  and a push switch mechanism  4  located on the inside of a dial unit  11  of the rotary switch mechanism  3 , for instance, are provided, with an indicator unit  13  provided at the center of the push switch mechanism  4 . In addition, a light emitting indicator unit  14  is provided at the front surface of the case  2 . 
     The push switch mechanism  4 , which may be, for instance, an auto switch for turning on/off the air-conditioning system, comprises a push knob  5  slidably mounted at a cylindrical mounting portion  7  provided continuously to the case  2  and a push switch  6  provided on a printed board  8  that is in contact with the circumferential edge of the push knob  5  at the inner end, and a specific space  10  is formed within the push switch mechanism  4 . 
     The rotary switch mechanism  3  comprises a rotary knob  16  constituted of the dial unit  11  projecting out at the surface of the case  2  and a cylindrical drive unit  12  interlocking with the dial unit  11 , and a detection switch  15 . In the first embodiment of the present invention, an interlocking piece  18  that interlocks with the dial unit  11  is formed at a circumferential edge  17 , as shown in FIG. 3, at one end of the cylindrical drive unit  12 , with drive pieces  20  which project out along the radius of the cylindrical drive unit  12  formed over a specific interval along the circumference at a circumferential edge  19  at the other end of the cylindrical drive unit  12 . 
     The detection switch  15 , which is a so-called bidirectional three-contact point switch of the known art, may comprise a movable piece  21  the front end of which moves around a shaft  21   a  along the direction in which the drive pieces  20  move as the drive pieces  20  pass while maintaining contact, a cam portion  22  that communicates the movement of the movable piece  21 , a switch spring  24  that causes contact points  24   a  and  24   b  formed at the front end thereof as the cam portion  22  moves, contact points T 1 , T 2  and T 3  formed at the surface against which the contact points  24   a  and  24   b  slide, a case  23  at which the contact points T 1 , T 2  and T 3  are provided with the cam portion  22  and the switch spring  24  housed therein and the shaft  21   a  rotatably fixed thereto and a lid portion  23   a  that includes an opening through which the drive pieces  20  project out and hold arms  22   a  and  22   b  of the cam portion  22 . 
     In the structure described above, the movable piece  21  is pushed down along direction P 1  as the drive pieces  20  travel along direction P 1  and, as a result, the arm  22   a  of the cam portion  22  causes the switch spring  24  to move along direction A. Thus, the terminal  24   a  comes in contact with the contact point T 2  and the terminal  24   b  comes in contact with the contact point T 1 , thereby setting the terminals T 1  and T 2  in a state of contact. However, since the movable piece  21  becomes reset to its original position after one of the drive pieces  20  passes over, the switch spring  24 , too, returns to its original position, thereby cutting off the terminals T 1  and T 2  from each other again. In this manner, when the drive pieces  20  move along direction P 1  by one unit of pitch a single signal is generated at the T 2  terminal. Likewise, when the drive pieces  20  move along direction P 2  by one unit of pitch, the switch spring  24  moves along direction B and then returns to its original position to set the terminals T 1  and T 3  in a state of contact, thereby generating a single signal at the T 3  terminal. 
     Thus, when the driver rotates the dial unit  11  over a specific range, a specific number of drive pieces  20  sequentially pass over the detection switch  15  causing the movable piece  21  to move the specific number of times, which, in turn, causes the detection switch  15  to output the specific number of signals indicating the direction of the passage of the drive pieces. More specifically assuming that the drive pieces  20  are formed over intervals each corresponding to a 0.5° C. increment at the operation panel  1  in FIG. 1, for instance, if the dial unit  11  is rotated to change the temperature setting from 25° C. to 28° C., the contact point T 1  and the contact point T 3  that achieve contact when the temperature setting is raised (e.g., along direction P 2 ) enter a state of contact six times at the detection switch  15 , thereby generating six signals indicating direction P 2  at the terminal T 3  to allow the driver to verify that the temperature setting has been changed from 25° C. to 28° C. Likewise, when the temperature setting has been lowered from 28° C. to 24° C., the contact point T 1  and the contact point T 2  that achieve contact when lowering the temperature setting (e.g., along direction P 1 ) enter a contact state eight times thereby generating eight signals indicating direction P 1  at the terminal T 2  and making it possible to verify that the temperature setting has been changed from 28° C. to 24° C. 
     In addition, as illustrated in FIG. 2, adequate space for accommodating the push switch mechanism  4  is assured on the inside by employing the rotary switch mechanism  3  achieved in the first embodiment, and consequently, one of the light paths, i.e., a light path  26   a  of a light guide  26  can be housed within the push switch mechanism  4 , and the space for accommodating the light source for the indicator  13  of the push switch mechanism  4  can be assured with ease. Furthermore, since the drive pieces  20  of the rotary knob  16  and the movable piece  21  of the detection switch  15  are not fixed to each other in this embodiment, the function of the detection switch  15  is not compromised as long as the movable piece  21  is set intersecting the rotational range of the drive pieces  20  even if a slight dimensional misalignment occurs during the mounting process, and thus, the mounting process can be simplified. It is to be noted that reference numeral  26   b  indicates a light path through which light is provided to the indicator unit  14  and reference numeral  27  indicates a light bulb constituting a light source provided on the printed board  8 . While a light bulb is utilized as the light source in this embodiment, a light emitting diode may instead be employed. 
     In the second embodiment shown in FIG. 4, a rotary knob  16 A in a rotary switch mechanism  3 A comprises a dial unit  11 A projecting out from the case  2 , a rod unit  29  mounted at a cylindrical fitting portion  28  provided at the center of the dial unit  11 A and a disk unit  30  provided at an end of the rod unit  29 . Drive pieces  20 A extending along the radius of the disk unit  30  are formed over specific intervals around the disk unit  30  to cause a movement of a movable piece  21  of the detection switch  15 . It is to be noted that in this embodiment and subsequent embodiments, the same reference numerals are assigned to components identical to or components achieving identical effects to those in the embodiment described above to preclude the necessity for a repeated explanation thereof. 
     Since this structure allows a specific space  31  to be secured between the rotary knob  16 A and the printed board  8 , an electronic part  32 , which may be a resistor, a capacitor or an IC, can be accommodated adjacent a light path  33  which guides the light from the light bulb  27  to achieve a light emission at the circumferential edge of the dial unit  11 A. 
     At a cylindrical drive unit  12 B in the third embodiment illustrated in FIG. 5, drive pieces  20 B are formed so as to project out along the axis of the cylindrical drive unit  12 B over a specific interval along the circumference from a circumferential edge  19 B at the other end of the cylindrical drive unit  12 B. Since the drive pieces  20 B do not project out along the radial direction in this embodiment, there is a likelihood of the measurement along the axial direction being greater than in the previous embodiments. However, a space is assured at the circumferential edge of the cylindrical drive unit  12 B along the radial direction. 
     A rotary switch mechanism  3 B shown in FIG. 6 includes a rotary knob  16 B achieved by forming a dial unit  11 B and the cylindrical drive unit  12 B in the third embodiment and as an integrated unit with a light source  27  provided on the printed board  8  at the center of the rotary knob  16 B. In addition, the rotary knob  16 B in the embodiment is constituted of a transparent resin, a colored transparent resin or a colored opaque resin such as a milk-white resin, and a light emission is achieved at the rotary knob  16 B itself by utilizing the light source  27 . A ring  36  constituted of a transparent resin, a colored transparent resin or a colored opaque resin such as a milk-white resin taking on a color different from the color of the rotary knob  16 B is provided at the external circumference of the rotary knob  16 B. This structure allows a plurality of indications to be produced with a single light source. It is to be noted that while the cylindrical drive unit  12 B and the rotary knob  16 B are formed as an integrated unit in the third embodiment, they may be formed as separate parts and then may be integrated with each other through fitting or the like, instead. 
     In a rotary switch mechanism  3 C in the fourth embodiment shown in FIG. 7 which is achieved by modifying the cylindrical drive unit  12 B in the third embodiment, a flange portion  42  distends outward along the radial direction from a specific position at the cylindrical drive unit  12 C, a groove portion  40  running along the flange portion  42  is formed at the lower side surface of the flange portion  42 , a part of the groove portion  40  has a greater depth for positioning purposes and the position is set as a ball  38  of a click mechanism  37  goes into the deeper part. This position corresponds to a position of the drive pieces  20 C. It is to be noted that while the click mechanism in the embodiment is constituted of the ball  38  pressed into the groove portion  40  by a spring  39 , the click mechanism may instead be constituted of a plate spring, for instance. In addition, the dial unit  11 C in the embodiment is constituted as a part separate from the cylindrical drive unit.  12 C by using a transparent resin or the like and a film  41  for blocking light is formed over the area where it is not necessary to emit light to ensure that light is emitted only where needed. 
     In the fifth embodiment shown in FIG. 8, drive pieces  20 D at a circumferential edge  19 D at the other end of a cylindrical drive unit  12 D constituting a rotary knob  16 D are formed as gear teeth and the detection switch  15  is provided along the radial direction. Since the detection switch  15  is provided along the radial direction in this case, adequate space is assured along the axial direction. 
     In the sixth embodiment shown in FIG. 9, drive pieces  20 E at a circumferential edge  19 E at the other end of a cylindrical drive unit  12 E constituting a rotary knob  16 E are formed as gear teeth and the detection switch  15  is provided on a sub-printed board  8 A set perpendicular to the main printed board  8  shown in the figures referred to earlier. Since this allows the detection switch  15  to be mounted at any position as long as it is provided in the vicinity of the cylindrical drive unit  12 E, a higher degree of freedom is afforded in design. 
     In the seventh embodiment shown in FIG. 10, drive pieces  20 F formed as gear teeth at a circumferential edge  19 F at the other end of a cylindrical drive unit  12 F are set within the range of the bottom surface of the cylindrical drive unit  12 F. By adopting this structure, the measurement along the radial direction is reduced compared to those in the fifth and sixth embodiments shown in FIGS. 8 and 9 respectively. 
     In the eighth embodiment shown in FIG. 11, plate like drive pieces  20 G at a circumferential edge  19 G at the other end of a cylindrical drive unit  12 G are formed within the range of the bottom surface of the cylindrical drive unit  12 G. In this case, too, the measurement along the radial direction can be reduced compared to those in the fifth and sixth embodiments shown in FIGS. 8 and 9 respectively, as in the seventh embodiment shown in FIG.  10 . 
     In the ninth embodiment shown in FIG. 12, an intermediate transmission mechanism  50  is provided between the drive pieces  20  and the movable piece  21  in a structure in which the pitch of the drive pieces  20  formed at the cylindrical drive unit  12  constituting the rotary knob  16  is not large enough to allow the required movement of the movable piece  21  at the detection switch  15 , i.e., in a structure in which the rotary knob  16  has a small radius. 
     The intermediate transmission mechanism  50  comprises a first arm  52  and a second arm  53  provided on the two opposite sides of a rotational support point  51  and a spring  55  constituting a holding mechanism  54  that holds the first and second arms  52  and  53  at specific positions. In addition, the front end of the first arm  52  is caused to move by the drive pieces  20 , whereas a working portion  56  that moves the movable piece  21  is provided at the front end of the second arm  53 . The working portion  56  includes an interlocking groove  57  that interlocks with the movable piece  21  and its side surface toward the detection switch  15  is formed in an arc extending over a specific length so as to ensure that the movable piece  21  is not allowed to disengage from the working portion  56 . In addition, the ratio of the length L 1  of the first arm  52  and the length L 2  of the second arm  53  should be set equal to or slightly larger than the ratio of the pitch P 1  of the drive pieces  20  and the operating pitch P 2  of the movable piece  21  (L 1 /L 2 ≧P 1 /P 2 ). 
     Under normal circumstances, the cylindrical drive unit  12  needs to have a minimum diameter of 46 mm to generate a single ON signal in correspondence to a rotational angle of 10° by which the cylindrical drive unit  12  is rotated since the movable piece  21  at the detection switch  15  requires an operating distance of 4 mm. However, if the diameter of the cylindrical drive unit  12  is smaller than 46 mm, e.g., 23 mm, the pitch of the drive pieces  20  is 2 mm and, accordingly, by setting the ratio of the lengths of the first and second arms  52  and  53  at the intermediate transmission, mechanism  50  equal to or larger than 1:2, the operating pitch P 2  of the detection switch  15  can be set equal to or larger than 4 mm, and thus, an ON signal can be generated at the detection switch  15  in correspondence to the rotational range of 10° over which the cylindrical drive unit  12  is rotated. 
     In addition, while the first arm  52  and the second arm  53  in the intermediate transmission mechanism  50  achieved in the ninth embodiment shown in FIG. 12 are provided on a single straight line and the detection switch  15  is provided on an extension of the straight line, the first arm  52  and the second arm  53  in the tenth embodiment shown in FIG. 13 are set perpendicular to each other extending from the rotational support point  51 , with the detection switch  15  provided at a position different from that assumed in the ninth embodiment. While the detection switch  15  is provided along the perpendicular direction in the embodiment, the position of the detection switch  15  can be varied freely by setting the second arm  53  at a specific angle relative to the position of the first arm  52 . 
     In the eleventh embodiment shown in FIG. 14, the drive pieces  20  are constituted of the teeth of a drive gear  60  formed at the cylindrical drive unit  12 , and an intermediate transmission mechanism  50 B is constituted of a working gear  61  that interlocks with the drive gear  60  and at least one working portion  62  that rotates together with the working gear  61 . 
     To explain the embodiment by assuming that four working portions  62  are formed over a uniform interval, if one ON signal is to be output through the detection switch  15  in correspondence to a rotational angle of 10° by which the cylindrical drive unit  12  is rotated, the ratio of the radius of the drive gear  60  and the radius of the working gear  61  and the gear ratio need to be set to 9:1 as there are four working portions  62 . In addition, since the ratio of the radii and the gear ratio can be reduced by increasing the number of working portions  62 , the ratio of the radius of the drive gear  60  and the radius of the working gear  61  and the gear ratio should be adjusted by taking into consideration the pitch of the working portions  62  to achieve further versatility. 
     As explained above, when the cylindrical drive unit  12  has a smaller diameter, the pitch of the drive pieces  20  becomes smaller than the operating pitch of the movable piece  21 , and accordingly, the angle (phase) α 1  of the drive pieces  20  formed around the cylindrical drive unit  12  is set larger than the minimum angle requirement (phase) and detection switches  15  are each provided at a phase α 2  which is different from the phase α 1  in the twelfth embodiment so as to allow the individual detection switches  15  to sequentially output signals when the drive pieces  20  move over a specific range. 
     For instance, if the angle (phase) α 1  formed by adjacent drive pieces  20  is 20° as shown in FIG.  15  and two detection switches are provided in conjunction with this structure, the angle (phase) α 2  formed by a movable piece  21 A of a first detection switch  15 A and a movable piece of  21 B of a second detection switch  15 B is set through a formula; 20n+C (C=10). In more specific terms, the position of the second detection switch  15 B is set at a position at a 30° phase, a 50° phase, a 70° phase . . . or a 330° phase relative to the position of the first detection switch  15 A. Thus, if the drive pieces  20  move by 10°, the drive pieces  20  cause either the movable piece  21 A or the movable piece  21  B of the first detection switch  15 A or the second detection switch  15 B to move, and when the drive pieces  20  move by another 10°, the other movable piece  21 A or  2   1 B is caused to move. As a result, even though the drive pieces  20  are set over 20° intervals, the first detection switch  15 A and the second detection switch  15 B each output a signal as the cylindrical drive unit  12  is rotated by 20° and, consequently, two signals are obtained in correspondence to a 20° rotation of the cylindrical drive unit  12 . If, on the other hand, the drive pieces  20  are each set at a 30° phase, a second detection switch should be provided at a 30n+10 phase and a third detection switch should be provided at a 30n+20 phase relative to the position of a first detection switch, to obtain a signal in correspondence to every 10° rotation of the cylindrical drive unit  12  even though the drive pieces  20  are formed over 30° intervals. 
     By forming the drive pieces  20  over a distance from each other that allows the minimum operating pitch (approximately 4 mm) for the movable pieces  21  and providing the plurality of detection switches  15  at specific phases (central angles) different from the phases (central angles) of the drive pieces  20 , as described above, an ON signal can be obtained through one of the detection switches in correspondence to a specific angle by which the rotary knob  16  is rotated. Thus, with al representing the phase of the drive pieces  20  and M representing the number of detection switches provided, the phase α 2  at which an Fth detection switch should be set can be determined through the following formula (1). It is to be noted that n is a natural number and 0&lt;α 2 &lt;360. 
     
       
         α 2 = n ·α 1 + F (α 1 / M )  (1) 
       
     
     While the detection switch  15  is constituted of a physical detection switch that detects the passage of the drive pieces in the structures described above, the detection switches in the embodiments may each be constituted of an optical detection switch having a light emitting element and a light receiving element, which detects the passage of and the direction of the passage of the drive pieces by detecting a change of light manifesting while the drive pieces pass between the light emitting element and the light receiving element, instead. Moreover, if a light emitting source for the indicator unit is provided at the center of the rotary knob, only the light receiving element may be provided to detect the passage of and the direction of the passage of the drive pieces. In addition, a detection switch utilized in the present invention may take on any structure as long as it is capable of detecting the passage of and the direction of the passage of the drive pieces through detection of a change occurring in an electromagnetic wave, an acoustic wave or the like instead of a change of a visible light beam described above. However, at present, it is most desirable to utilize physical detection switches since they are the least costly. 
     INDUSTRIAL APPLICABILITY 
     As explained above, according to the present invention in which the passage of and the direction of the passage of drive pieces formed over specific intervals at the circumferential edge of a rotary knob at one end further inward at an operation panel are detected by utilizing a detection switch, the detection switch needs only to be provided within the range of movement of the drive pieces or in the vicinity of the range of their movement, e.g., on a printed board, and thus, ample space is assured on the printed board to improve the degree of freedom with regard to the layout of the parts on the printed board. Since this allows the path of light emitted from the light source on the printed board to be designed with freedom, the degree of design freedom is further improved. 
     In addition, since the drive pieces at the rotary knob and the movable piece of the detection switch are not fixed to each other, it is not necessary to align the rotary knob with the detection switch with absolute precision, and thus, the rotary switch mechanism can be mounted with ease. Moreover, since the detection switch can be constituted of an inexpensive switch, the production cost can be reduced.