Abstract:
A mechanical time piece has a mainspring for generating a rotational force and a front train wheel for undergoing rotation in accordance with a rotational force generated by the mainspring. An escapement and speed control apparatus controls rotation of the front train wheel and has a timed annular balance for undergoing reciprocal rotational movement, an escape wheel and pinion for undergoing rotation in accordance with rotation of the front train wheel, and a pallet fork for controlling rotation of the escape wheel and pinion in accordance with rotational movement of the timed annular balance. A switch mechanism outputs an ON signal when a rotational angle of the timed annular balance becomes equal to or larger than a predetermined threshold angle and outputs an OFF signal when the rotational angle of the timed annular balance does not exceed the threshold angle. A balance rotational angle control mechanism applies a force to the timed annular balance to restrain rotation of the timed annular balance when the switch mechanism outputs the ON signal. The balance rotational angle control mechanism has a balance magnet disposed on the timed annular balance and a plurality of coils for exerting a magnetic force to the balance magnet to thereby restrain rotation of the timed annular balance when the switch mechanism outputs the ON signal and for not exerting a magnetic force to the balance magnet when the switch mechanism outputs the OFF signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national state application of copending International Application Ser. No. PCT/JP99/06292, filed Nov. 11, 1999 claiming a priority date of Nov. 11, 1999, and published in a non-English language. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mechanical time piece having a balance rotational angle control mechanism constituted to exert a force for restraining rotation of a balance with hairspring. 
     Particularly, the invention relates to a mechanical time piece having a balance rotational angle control mechanism including a balance magnet provided to a balance with hairspring and a coil arranged to be related to the balance magnet. 
     2. Background Information 
     According to a conventional mechanical time piece, as shown in FIG.  13  and FIG. 14, a movement (machine body)  1100  of a mechanical time piece is provided with a main plate  1102  constituting a base plate of the movement. A winding stem  1110  is rotatably integrated to a winding stem guide hole  1102   a  of the main plate  1102 . A dial  1104  (shown in FIG. 14 by an imaginary line) is attached to the movement  1100 . 
     Generally, in both sides of the main plate, a side thereof having the dial is referred to as “back side” of the movement and a side thereof opposed to the side having the dial is referred to as “front side” of the movement. A train wheel integrated to the “front side” of the movement is referred to as “front train wheel” and a train wheel integrated to the “back side” of the movement is referred to as “back train wheel”. 
     A position in the axis line direction of the winding stem  1110  is determined by a switch apparatus including a setting lever  1190 , a yoke  1192 , a yoke spring  1194  and a setting lever jumper  1196 . A winding pinion  1112  is provided rotatably at a guide shaft portion of the winding stem  1110 . When the winding stem  1110  is rotated in the state in which the winding stem  1110  is disposed at a first winding stem position (0-stage) on a side most proximate to the inner side of the movement along the rotational axis line, the winding pinion  1112  is rotated via rotation of a clutch wheel. A crown wheel  1114  is rotated by rotation of the winding pinion  1112 . A ratchet wheel  1116  is rotated by rotation of the crown wheel  1114 . By rotating the ratchet wheel  1116 , a mainspring  1122  contained in a barrel complete  1120  is wound up. A center wheel &amp; pinion  1124  is rotated by rotation of the barrel complete  1120 . An escape wheel &amp; pinion  1130  is rotated via rotation of a fourth wheel &amp; pinion  1128 , a third wheel &amp; pinion  1126  and the center wheel &amp; pinion  1124 . The barrel complete  1120 , the center wheel &amp; pinion  1124 , the third wheel &amp; pinion  1126  and the fourth wheel &amp; pinion  1128  constitute a front train wheel. 
     An escapement &amp; speed control apparatus for controlling rotation of the front train wheel includes a balance with hairspring  1140 , the escape wheel &amp; pinion  1130  and a pallet fork  1142 . The balance with hairspring  1140  includes a balance stem  1140   a,  a balance wheel  1140   b  and a hairspring  1140   c.  Based on rotation of the center wheel &amp; pinion  1124 , a cannon pinion  1150  is simultaneously rotated. A minute hand  1152  attached to the cannon pinion  1150  displays “minute”. The cannon pinion  1150  is provided with a slip mechanism relative to the center pinion &amp; wheel  1124 . Based on rotation of the cannon pinion  1150 , via rotation of a minute wheel, an hour wheel  1154  is rotated. An hour hand  1156  attached to the hour wheel  1154  displays “hour”. 
     The barrel complete  1120  is supported rotatably by the main plate  1102  and a barrel bridge  1160 . The center wheel &amp; pinion  1124 , the third wheel &amp; pinion  1126 , the fourth wheel &amp; pinion  1128  and the escape wheel &amp; pinion  1130  are supported rotatably by the main plate  1102  and a train wheel bridge  1162 . The pallet fork  1142  is supported rotatably by the main plate  1102  and a pallet bridge  1164 . The balance with hairspring  1140  is supported rotatably by the main plate  1102  and a balance bridge  1166 . 
     The hairspring  1140   c  is a leaf spring in a helical (spiral) shape having a plural turn number. An inner end portion of the hairspring  1140   c  is fixed to a hairspring holder  1140   d  fixed to the balance stem  1140   a  and an outer end portion of the hairspring  1140   c  is fixed via a hairspring stud  1170   a  attached to a stud support  1170  fixed to the balance bridge  1166  by fastening screws. 
     A regulator  1168  is attached rotatably to the balance bridge  1166 . A hairspring bridge  1168   a  and a hairspring rod  1168   b  are attached to the regulator  1168 . A portion of the hairspring  1140   c  proximate to the outer end portion is disposed between the hairspring bridge  1168   a  and the hairspring rod  1168   b.    
     Generally, according to a conventional representative mechanical timepiece, as shown by FIG. 8, with elapse of a duration time period of rewinding the mainspring from a state in which the mainspring has completely been wound up (fully wound state), mainspring torque is reduced. For example, in the case of FIG. 8, the mainspring torque is about 27 g.cm in the fully wound state, becomes about 23 g.cm after elapse of 20 hours from the fully wound state and becomes about 18 g.cm after elapse of 40 hours from the fully wound state. 
     Generally, according to a conventional representative mechanical time piece, as shown by FIG. 9, when the mainspring torque is reduced, the swing angle of the balance with hairspring is also reduced. For example, in the case of FIG. 9, when the mainspring torque is 25-28 g.cm, the swing angle of the balance with hairspring is about 240-270 degree and when the mainspring torque is 20-25 g.cm, the swing angle of the balance with hairspring is about 180-240 degree. 
     In reference to FIG. 10, there is shown a transitional change of instantaneous rate with regard to swing angle of a balance with hairspring according to a conventional representative mechanical time piece (numerical value indicating accuracy of time piece). In this case, the “instantaneous rate” is defined as “a value indicating gain or loss of a mechanical time piece after elapse of one day after the mechanical time piece is assumed to be left for one day while maintaining state or environment of swing angle of a balance with hairspring or the like when the rate is measured”. In the case of FIG. 10, when a swing angle of a balance with hairspring is equal to or larger than 240 degree or is equal to or smaller than 200 degree, the instantaneous rate is retarded. 
     For example, according to a conventional representative time piece, as shown by FIG. 10, when the swing angle of the balance with hairspring falls in a range of about 200 through 240 degree, the instantaneous rate is about 0 through 5 seconds/day (gain of 0 through 5 seconds per day), however, when the swing angle of the balance with hairspring is about 170 degree, the instantaneous rate becomes about −20 seconds/day (loss of about 20 seconds per day). 
     In reference to FIG. 12, there is shown a transitional change of elapse time and instantaneous rate when a mainspring is rewound from a fully wound state in a conventional representative mechanical time piece. In this case, in the conventional mechanical time piece, “rate” indicating gain of the timepiece or loss of the time piece per day, is provided by integrating instantaneous rate with regard to elapse time of rewinding the balance with hairspring from a fully wound state, which is indicated in FIG. 12 by an extremely slender line, over 24 hours. 
     Generally, according to the conventional mechanical timepiece, with elapse of duration time period of rewinding the mainspring from the fully wound state, the mainspring torque is reduced, the swing angle of the balance with hairspring is also reduced and accordingly, the instantaneous rate is retarded. Therefore, according to the conventional mechanical timepiece, by estimating loss of the time piece after elapse of the duration time period of 24 hours, instantaneous rate when the mainspring is brought into the fully wound state, is previously gained and previously adjusted such that the “rate” indicating gain of the time piece or loss of the time piece per day becomes positive. 
     For example, according to the conventional representative time piece, as shown by the extremely slender line in FIG. 12, although in the fully wound state, the instantaneous rate is about 3 seconds/day (gain of about 3 seconds per day), after elapse of 20 hours from the fully wound state, the instantaneous rate becomes about −3 seconds/day (loss of about 3 seconds per day), after elapse of 24 hours from the fully wound state, the instantaneous rate becomes about −8 seconds per day (loss of about 8 seconds per day) and after elapse of 30 hours from the fully wound state, the instantaneous rate becomes about −16 seconds/day (loss of about 16 seconds per day). 
     Further, as a conventional apparatus of adjusting a swing angle of a balance with hairspring, there is disclosed in Japanese Utility Model Laid-Open No. 41675/1979, a constitution having a swing angle adjusting plate exerting braking force to a balance with hairspring by generating eddy current at each time of pivotal approach of a magnet of the balance with hairspring. 
     Further, as shown by FIG. 36, a conventional coreless motor  2100  is provided with a shaft  2102 , a magnet yoke  2104  fixed to the shaft  2102  and a drive magnet  2106  fixed to the magnet yoke  2104 . A stator yoke  2110  is provided rotatably to the shaft  2102  via a bearing  2112 . A printed circuit board  2114  is fixed to the stator yoke  2110 . A drive coil  2116  is fixed to the printed circuit board  2114  to be opposed to the drive magnet  2106  and spaced apart therefrom. By applying current to the drive coil  2116 , the drive magnet  2106 , the magnet yoke  2104  and the shaft  2102  are constituted to rotate. 
     It is an object of the invention to provide a mechanical time piece having a balance rotational angle control mechanism capable of controlling a swing angle of a balance with hairspring to fall in a constant range. 
     Further, it is an object of the invention to provide a mechanical time piece having excellent accuracy in which a change in a rate is in considerable even after elapse of an elapse time period from a fully wound state of a mainspring by providing a novel balance rotational angle control mechanism. 
     Further, it is an object of the invention to provide a mechanical time piece constituted such that a balance rotational angle control mechanism includes a balance magnet provided at a balance with hairspring and a coil unit arranged to relate to the balance magnet and constituted such that fabrication and assembly of parts are facilitated. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided a mechanical time piece characterized in that in a mechanical time piece having a main plate constituting a base plate of the mechanical time piece, a mainspring constituting a power source of the mechanical time piece, a front train wheel rotated by a rotational force when the mainspring is rewound and an escapement &amp; speed control apparatus for controlling rotation of the front train wheel in which the escapement &amp; speed control apparatus includes a balance with hairspring alternately repeating right rotation and left rotation, an escape wheel &amp; pinion rotated based on the rotation of the front train wheel and a pallet fork for controlling rotation of the escape wheel &amp; pinion based on operation of the balance with hairspring, the mechanical time piece comprising a switch mechanism constituted to output a signal of ON when a rotational angle of the balance with hairspring becomes equal to or larger than a predetermined threshold and output a signal of OFF when the rotational angle of the balance with hairspring does not exceed the threshold, and a balance rotational angle control mechanism constituted to exert a force for restraining rotation of the balance with hairspring to the balance with hairspring when the switch mechanism outputs the signal of ON. 
     According to the mechanical time piece of the aspect of the invention, the switch mechanism is constituted to output the signal of ON when a hairspring provided at the balance with hairspring is brought into contact with terminal members constituting a switch lever. 
     Further, according to the mechanical time piece of the aspect of the invention, the balance rotational angle control mechanism includes a balance magnet provided to the balance with hairspring and a plurality of coils arranged to be capable of exerting a magnetic force to the balance magnet and the coils are constituted to exert the magnetic force to the balance magnet to thereby restrain the rotation of the balance with hairspring when the switch mechanism outputs the signal of ON and not to exert the magnetic force to the balance magnet when the switch mechanism outputs the signal of OFF. 
     Further, the mechanical time piece of the invention is provided with a circuit board having patterns for conducting the plurality of coils. 
     By using the balance rotational angle control mechanism constituted in this way, the rotational angle of the balance with hairspring of the mechanical time piece can effectively be controlled, thereby, accuracy of the mechanical time piece can be promoted. 
     Further, according to the mechanical time piece of the invention, it is preferable that wiring portions of the plurality of coils are arranged on a side of a main plate of the circuit board. 
     Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are attached to a coil bridge and the circuit board is attached to the coil bridge and the coil bridge is guided by a bearing member provided at the main plate. 
     Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are attached to coil bridges provided respectively separately, the coil bridges are respectively attached to the circuit board and the coil bridges are guided by the guide holes respectively provided at the main plate. 
     Further, according to the mechanical time piece of the invention, it is preferable that the circuit board is provided with patterns for conducting the plurality of coils on one side thereof and is provided with patterns for connecting lead wires for conducting the switch mechanism on other side thereof. 
     Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are connected in series by the patterns provided to the circuit board. 
     By constituting in this way, the plurality of coils can be arranged efficiently in a small space and the plurality of coils can firmly be conducted. 
     Further, according to the mechanical time piece of the invention, it is preferable that the switch mechanism includes a first terminal member and a second terminal member and is further provided with an adjusting apparatus for changing an interval between the first terminal member and the second terminal member. 
     Further, according to the mechanical time piece of the invention, it is preferable that the switch mechanism includes a first terminal member and a second terminal member and is further provided with an adjusting apparatus for simultaneously moving the first terminal member and the second terminal member relative to a rotational center of the balance with hairspring. 
     By constituting in this way, the positions of the first terminal member and the second terminal member relative to the portion proximate to the outer end portion of the hairspring and the interval between the first terminal member and the second terminal member can effectively be adjusted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plane view showing an outline shape of a front side of a movement according to Embodiment 1 of a mechanical time piece of the invention (in FIG. 1, portions of parts are omitted and bridge members are indicated by imaginary lines). 
     FIG. 2 is an outline partial sectional view of the movement according to Embodiment 1 of the mechanical time piece of the invention (in FIG. 2, portions of parts are omitted). 
     FIG. 3 is a plane view of an enlarged portion showing an outline shape of a portion of a balance with hairspring in a state in which a switch mechanism is made OFF according to Embodiment 1 of the mechanical time piece of the invention (in FIG. 3, a portion of a circuit board is shown to be broken to indicate portions of shapes of coils). 
     FIG. 4 is a sectional view of the enlarged portion showing the outline shape of the portion of the balance with hairspring in the state in which the switch mechanism is made OFF according to Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 5 is a plane view of the enlarged portion showing the outline shape of the portion of the balance with hairspring in the state in which the switch mechanism is made ON according to Embodiment 1 of the mechanical time piece of the invention (in FIG. 5, a portion of the circuit board is shown to be broken to indicate portions of shapes of coils). 
     FIG. 6 is a sectional view of the enlarged portion showing the outline shape of the portion of the balance with hairspring in a state in which the switch mechanism is made ON according to Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 7 is a perspective view showing an outline shape of a balance magnet used in a mechanical time piece of the invention. 
     FIG. 8 is a graph showing an outline relationship between an elapse time period of rewinding a mainspring from a fully wound state and mainspring torque in a mechanical time piece. 
     FIG. 9 is a graph showing an outline relationship between swing angle of a balance with hairspring and mainspring torque in a mechanical time piece. 
     FIG. 10 is a graph showing an outline relationship between swing angle of a balance with hairspring and instantaneous rate in a mechanical time piece. 
     FIG. 11 is a block diagram showing operation when a circuit is opened and operation when the circuit is closed in a mechanical time piece of the invention. 
     FIG. 12 is a graph showing an outline relationship between an elapse time period of rewinding a mainspring from a fully wound state and instantaneous rate according to a mechanical time piece of the invention and a conventional mechanical time piece. 
     FIG. 13 is a plane view showing an outline shape of a front side of a movement of a conventional mechanical time piece (in FIG. 13, portions of parts are omitted and bridge members are indicated by imaginary lines). 
     FIG. 14 is an outline partial sectional view of the movement of the mechanical time piece (in FIG. 14, portions of parts are omitted). 
     FIG. 15 is a plane view showing a switch adjusting apparatus used in a mechanical time piece according to the invention. 
     FIG. 16 is a sectional view showing the switch adjusting apparatus used in the mechanical time piece of the invention. 
     FIG. 17 is a plane view showing a state of rotating a switch position adjusting lever in the switch adjusting apparatus used in the mechanical time piece of the invention. 
     FIG. 18 is a sectional view showing a state of rotating the switch position adjusting lever in the switch adjusting apparatus used in the mechanical time piece of the invention. 
     FIG. 19 is a plane view showing a state of rotating a switch interval adjusting lever in the switch adjusting apparatus used in the mechanical time piece of the invention. 
     FIG. 20 is a sectional view showing the state of rotating the switch interval adjusting lever in the switch adjusting apparatus used in the mechanical time piece of the invention. 
     FIG. 21 is a front plane view showing an outline shape of a coil unit according to Embodiment 1 of a mechanical time piece of the invention. 
     FIG. 22 is a sectional view showing the outline shape of the coil unit according to Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 23 is a rear plane view showing an outline shape of a coil according to Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 24 is a sectional view showing the outline shape of the coil according to Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 25 is a front plane view showing an outline shape of a modified mode of a coil unit according to Embodiment 1 of a mechanical time piece of the invention. 
     FIG. 26 is a front plane view showing an outline shape of other modified mode of a coil unit according to Embodiment 1 of a mechanical time piece of the invention. 
     FIG. 27 is a plane view showing an outline shape of a front side of a movement according to Embodiment 2 of a mechanical time piece of the invention (in FIG. 27, portions of parts are omitted and bridge members are indicated by imaginary lines). 
     FIG. 28 is an outline partial sectional view of the movement according to Embodiment 2 of the mechanical time piece of the invention (in FIG. 28, portions of parts are omitted). 
     FIG. 29 is a plane view of an enlarged portion showing an outline shape of a portion of a balance with hairspring in a state in which a switch mechanism is made OFF according to Embodiment 2 of the mechanical time piece of the invention (in FIG. 29, a portion of a circuit board is shown to be broken to indicate portions of shapes of coils). 
     FIG. 30 is a sectional view of an enlarged portion showing an outline shape of a portion of a balance with hairspring in the state in which the switch mechanism is made OFF according to Embodiment 2 of the mechanical time piece of the invention. 
     FIG. 31 is a plane view of the enlarged portion showing the outline shape of the portion of the balance with hairspring in a state in which the switch mechanism is made ON according to Embodiment 2 of the mechanical time piece of the invention (in FIG. 31, a portion of the circuit board is shown to be broken to indicate portions of shapes of coils). 
     FIG. 32 is a sectional view of the enlarged portion showing the outline shape of the portion of the balance with hairspring in the state in which the switch mechanism is made ON according to Embodiment 2 of the mechanical time piece of the invention. 
     FIG. 33 is a front plane view showing the outline shape of the circuit board used in Embodiment 1 of the mechanical time piece of the invention. 
     FIG. 34 is a plane view showing an outline shape of a front side of a movement according to a modified example of Embodiment 1 of the mechanical time piece of the invention (in FIG. 34, portions of parts are omitted and bridge members are indicated by imaginary lines). 
     FIG. 35 is an outline partial sectional view of the movement according to the modified example of Embodiment 1 of the mechanical time piece of the invention (in FIG. 35, portions of parts are omitted). 
     FIG. 36 is a sectional view showing an outline shape of a conventional motor. 
     FIG. 37 is a front plane view showing an outline shape of a circuit board used in a modified example of Embodiment 1 of a mechanical time piece according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An explanation will be given of embodiments of a mechanical time piece according to the invention with reference to the drawings as follows. 
     (1) Embodiment 1 of Mechanical Time Piece According to the Invention 
     (1.1) Constitution of Movement of Mechanical Time Piece According to the Invention 
     In reference to. FIG.  1  and FIG. 2, according to an embodiment of a mechanical time piece of the invention, a movement (machine body)  600  of the mechanical time piece is provided with a main plate  102  constituting a base plate of the movement. A winding stem  110  is rotatably integrated to a winding stem guide hole  102   a  of the main plate  102 . A dial  104  (shown by FIG. 2 by imaginary line) is attached to the movement  600 . 
     The winding stem  110  is provided with a square portion and a guide shaft portion. A clutch wheel (not illustrated) is integrated to the square portion of the winding stem  110 . That is, the clutch wheel is provided with a rotational axis line the same as a rotational axis line of the winding stem  110 . That is, the clutch wheel is provided with a square hole and is provided to rotate based on rotation of the winding stem  110  by fitting the square hole to the square portion of the winding stem  110 . The clutch wheel is provided with tooth A and tooth B. The tooth A is provided at an end portion of the clutch wheel proximate to the center of the movement. The tooth B is provided at an end portion of the clutch wheel proximate to an outer side of the movement. 
     The movement  600  is provided with a switch apparatus for determining a position of the winding stem  110  in the axial line direction. The switch apparatus includes a setting lever  190 , a yoke  192 , a yoke spring  194  and a setting lever jumper  196 . Based on rotation of the clutch wheel, the position in the rotational axis line of the winding stem  110  is determined. Based on rotation of the yoke  192 , a position in the rotational axis line direction of the clutch wheel is determined. Based on rotation of the setting lever, the yoke is positioned to two positions in the rotational direction. 
     A winding pinion  112  is provided rotatably at the guide shaft portion of the winding stem  110 . When the winding stem  110  is rotated in a state in which the winding stem  110  is disposed at a first winding stem position (0-stage) most proximate to the inner side of the movement along the rotational axis line, the winding pinion  112  is constituted to rotate via rotation of the clutch wheel. A crown wheel  114  is constituted to rotate by rotation of the winding pinion  112 . A ratchet wheel  116  is constituted to rotate by rotation of the crown wheel  114 . 
     The movement  600  is provided with a mainspring  122  contained in a barrel complete  120  as its power source. The mainspring  122  is made of an elastic material having spring performance such as iron. By rotating the ratchet wheel  116 , the mainspring  122  is constituted to be capable of being wound up. 
     A center wheel &amp; pinion  124  is constituted to rotate by rotation of the barrel complete  120 . A third wheel &amp; pinion  126  is constituted to rotate based on rotation of the center wheel &amp; pinion  124 . A fourth wheel &amp; pinion  128  is constituted to rotate based on rotation of the third wheel &amp; pinion  126 . An escape wheel &amp; pinion  130  is constituted to rotate based on rotation of the fourth wheel &amp; pinion  128 . The barrel complete  120 , the center wheel &amp; pinion  124 , the third wheel &amp; pinion  126  and the fourth wheel &amp; pinion  128  constitute a front train wheel. 
     The movement  600  is provided with an escapement &amp; speed control apparatus for controlling rotation of the front train wheel. The escapement &amp; speed control apparatus includes a balance with hairspring  140  repeating right rotation and left rotation at a constant period, the escape wheel &amp; pinion  130  rotating based on rotation of the front train wheel and a pallet fork  142  for controlling rotation of the escape wheel &amp; pinion  130  based on operation of the balance with hairspring  140 . 
     The balance with hairspring  140  includes a balance stem  140   a,  a balance wheel  140   b  and a hairspring  140   c.  The hairspring  140   c  is made of an elastic material having spring performance such as “elinbar”. That is, the hairspring  140   c  is made of an electrically conducting material of metal. 
     Based on rotation of the center wheel &amp; pinion  124 , a cannon pinion  150  is simultaneously rotated. A minute hand  152  attached to the cannon pinion  150  is constituted to display “minute”. The cannon pinion  150  is provided with a slip mechanism having a predetermined slip torque relative to the center wheel &amp; pinion  124 . 
     Based on rotation of the cannon pinion  150 , a minute wheel (not illustrated) is rotated. Based on rotation of the minute wheel, an hour wheel  154  is rotated. An hour hand  156  attached to the hour wheel  154  is constituted to display “hour”. 
     The barrel complete  120  is supported rotatably by the main plate  102  and a barrel bridge  160 . The center wheel &amp; pinion  124 , the third wheel &amp; pinion  126 , the fourth wheel &amp; pinion  128  and the escape wheel &amp; pinion  130  are supported rotatably by the main plate  102  and a train wheel bridge  162 . The pallet fork  142  is supported rotatably by the main plate  102  and a pallet bridge  164 . 
     The balance with hairspring  140  is supported rotatably by the main plate  102  and a balance bridge  166 . That is, an upper mortise  140   a l of the balance stem  140   a  is supported rotatably by a balance upper bearing  166   a  fixed to the balance bridge  166 . The balance upper bearing  166   a  includes a balance upper hole jewel and a balance upper cap jewel. The balance upper hole jewel and the balance upper cap jewel are made of an insulating material such as ruby. 
     A lower mortise  140   a   2  of the balance stem  140   a  is supported rotatably by a balance lower bearing  102   b  fixed to the main plate  102 . The balance lower bearing  102   b  includes a balance lower hole jewel and a balance lower cap jewel. The balance lower hole jewel and the balance lower cap jewel are made of an insulating material such as ruby. 
     The hairspring  140   c  is a leaf spring in a helical (spiral) shape having a plural turn number. An inner end portion of the hairspring  140   c  is fixed to a hairspring holder  140   d  fixed to the balance stem  140   a  and an outer end portion of the hairspring  140   c  is fixed by screws via a hairspring holder  170   a  attached to a hairspring holder cap  170  rotatably fixed to the balance bridge  166 . The balance bridge  166  is made of an electrically conductive material of metal such as brass. The hairspring holder cap  170  is made of an eclectically conductive material of metal such as iron. 
     (1.2) Constitution of Switch Mechanism 
     Next, an explanation will be given of a switch mechanism of the mechanical time piece according to the invention. 
     In reference to FIG.  1  and FIG. 2, a switch lever  168  is rotatably attached to the balance bridge  166 . A first terminal member  168   a  and a second terminal member  168   b  are attached to the switch lever  168 . The switch lever  168  is attached to the balance bridge  166  and is rotatably attached thereto centering on the rotational center of the balance with hairspring  140 . The switch lever  168  is formed by an insulating material of plastic such as polycarbonate. The first terminal member  168   a  and the second terminal member  168   b  are fabricated by a conductive material of a metal such as brass. A portion of the hairspring  140   c  proximate to an outer end portion thereof is disposed between the first terminal member  168   a  and the second terminal member  168   b.    
     In reference to FIG.  1  through FIG. 4, a circuit unit  610  is attached to a face of a front side of the main plate  102 . The circuit unit  610  includes a circuit board  612  and a coil unit  614 . The coil unit  614  includes a coil bridge  616  and four coils  180 ,  180   a,    180   b  and  180   c.  In a state in which the coils  180 ,  180   a,    180   b  and  180   c  are arranged to be opposed to a face of the balance wheel  140   b  on the side of the main plate, the coil unit  614  is attached to the face of the main plate  102  on the front side. 
     Although a number of the coils is, for example, four as shown by FIG.  1  through FIG. 4, the number may be one, may be two, may be three or may be four or more. 
     The circuit board  612  is fixed to a face of the coil bridge  616  on the side opposed to the balance wheel  140   b  by circuit board fixing screws  618 . The circuit unit  610  is attached to the face on the front side of the main plate  102  by circuit unit fixing screws  620 . That is, as shown by FIG.  1  through FIG. 4, the coil unit  614  is attached to the face on the front side of the main plate  102  in a state in which the fourcoils  180 ,  180   a,    180   b  and  180   c  are respectively arranged on the side of the main plate  102  of the circuit board  612  and in a state in which the circuit board  612  is opposed to the face of the balance wheel  140   b  opposed to the main plate  102 . 
     In reference to FIG.  21  and FIG. 22, the coils  180 ,  180   a,    180   b  and  180   c  are respectively arranged to the coil bridge  616  such that wiring portions  180   m  are contained in opening portions  616   d,    616   a,    616   b  and  616   c  of the coil bridge  616 . 
     Four sets of guide pins  616   p   1  and  616   p   2  are provided at the coil bridge  616 . One set of the guide pins  616   p   1  and  616   p   2  guide the coil  180 , other set of the guide pins  616   p   1  and  616   p   2  guide the coil  180   a,  other set of the guide pins  616   p   1  and  616   p   2  guide the coil  180   b  and other set of the guide pins  616   p   1  and  616   p   2  guide the coil  180   c.    
     With reference to FIG.  23  and FIG. 24, each of the coils  180 ,  180   a,    180   b,    180   c  is provided with a coil stem  180   g  is constituted by a nonmagnetic material such as plastic or brass. The coil stem  180   g  is provided with a flange portion  180   f  at one end thereof, a front end portion  180   h  at other end thereof penetrates the coil board  180   k  and is fixed to the front side or the soil board  180   k  by caulking or the like. 
     The winding portion  180   m  is provided at an outer periphery of a shaft portion  180   j  of the coil stem  180   g.  Two terminals  180   e  of the winding portion  180   m  are fixed to back side patterns  180   s  arranged at the coil board  180   k  on the wiring side. Fixing of the terminal  180   e  of the wiring portion  180   m  may be carried out by welding, soldering adhering by using a conductive adhering agent or the like. The coil board  180   k  is provided with front side patterns  180   t.  The front side patterns  180   t  and the back side patterns  180   s  are respectively conducted individually by through holes  180   u.  Conduction of the front side pattern  180   t  and the backside pattern  180   s  may be carried out by through hole plating provided to the through hole  180   u.    
     In this case, in reference to FIG. 33, the back side of the circuit board  612  is provided with a first coil conducting pattern  612   a  provided for conducting in series the front side pattern  180   t  of the coil board  180   k  conducted to one terminal of the coil  180  and the front side pattern  180   t  of the coil board  180   k  conducted to one terminal of the coil  180   a,  a second coil conducting pattern  612   b  provided for conducting in series the front side pattern  180   t  of the coil board  180   k  conducted to other terminal of the coil  180   a  and the front side pattern  180   t  of the coil board  180   k  conducted to one terminal of the coil  180   b,  and a third coil conducting pattern  612   c  provided for conducting in series the front side pattern  180   t  of the coil board  180   k  conducted to other terminal of the coil  180   b  and the front side pattern  180   t  of the coil board  180   k  conducted to one terminal of the coil  180   c.    
     Therefore, according to the constitution shown by FIG.  1  through FIG. 4, the coils  180 ,  180   a,    180   b  and  180   c  are conducted in series by three of the coil conducting patterns  612   a,    612   b  and  612   c  provided at the circuit board  612 . 
     Further, the back side of the circuit board  612  is provided with a first coil contact pattern  612   d  for contacting the front side pattern  180   t  of the coil board  180   k  conducted to other terminal of the coil  180  and a second coil contact pattern  612   e  for contacting the front side pattern  180   t  of the coil board  180   k  conducted to other terminal of the coil  180   c.    
     The circuit board  612  is further provided with a first lead connecting pattern  612   f  and a second lead connecting pattern  612   g  on its front side. The first lead connecting pattern  612   f  and the first coil contact pattern  612   d  are conducted by a first through hole  612   h.  The second lead connecting pattern  612   g  and the second coil contact pattern  612   e  are conducted by a second through hole  612   j.  Conduction of the lead connecting pattern provided on the front side of the circuit board  612  and the coil contact pattern provided on the back side of the circuit board  612  may be carried out by through hole plating provided at the through hole. 
     When the circuit unit  610  is attached to the main plate  102 , the operation may be carried out by moving the circuit unit  610  in parallel with the surface of the main plate  102  such that a guiding semicircular arc portion  616   w  (refer to FIG. 21) of the coil bridge  616  is brought into contact with an outer peripheral portion of the balance lower bearing  102   b  fixed to the main plate  102 . The balance lower bearing  102   b  constitutes a bearing member provided at the main plate  102 . 
     According to the constitution, the circuit unit  610  can be attached to the main plate  102  after attaching the balance with hairspring  140  to the movement. 
     As a modified example, in reference to FIG. 25, a coil unit  630  includes a coil bridge  632  and the coil  180 . An outer peripheral shape of the coil bridge  632  is circular. 
     In this case, in reference to FIG.  34  and FIG. 35, according to a movement  690 , the circuit board  612  is fixed to faces of the respective coil bridges  632  of four of the coil units  630  opposed to the balance wheel  140   b  by the circuit board fixing screws  618 . The circuit unit  610  is attached to the face of the main plate  102  on the front side by the circuit unit fixing screws  620 . That is, four of the coil units  630  are attached to the face of the main plate  102  on the front side in the state in which four of the coils  180  are respectively arranged on the side of the main plate  102  of the circuit board  692  such that the circuit board  692  is opposed to the face of the balance wheel  140   b  opposed to the main plate  102 . 
     Attachment of the circuit unit to the main plate  102  can be carried out by, for example, providing four of coil guide holes (not illustrated) in a circular shape at the main plate  102  and arranging the circuit unit to the main plate  102  such that the coils  180  are contained in the respective coil guide holes. 
     According to such a constitution, by three of coil conducting patterns  692   a,    692   b  and  692   c  provided at a circuit board  692  (refer to FIG.  37 ), four of the coils  180  are conducted in series. 
     As other modified example, in reference to FIG. 26, a coil unit  636  includes a coil bridge  638  and the coil  180 . The outer peripheral shape of the coil bridge  638  is square. The circuit board  692  is fixed to faces of the respective coil bridges  638  of four of the coil units  636  opposed to the balance wheel  140   b  by the circuit board fixing screws  618 . The circuit unit is attached to the face of the front side of the main plate  102  by the circuit unit fixing screws  620 . That is, four of the coil units  636  are attached to the face of the front side of the main plate  102  in a state in which four of the coils  180  are respectively arranged on the side of the main plate  102  of the circuit board  692  such that the circuit board  692  is opposed to the face of the balance wheel  140   b  opposed to the main plate  102 . 
     Attachment of the circuit unit to the main plate  102  can be realized by, for example, providing four of coil guide holes (not illustrated) in a square shape at the main plate  102  and arranging the circuit unit to the main plate  102  such that the coils  180  are contained respectively in the coil guide holes. 
     Also according to the constitution, by three of the coil conducting patterns  692   a,    692   b  and  692   c  provided at the circuit board  692 , four of the coils  180  are conducted in series. 
     According to the constitutions of the two modified examples shown here, four of the same coils  180  are used and accordingly, when one of the coils  180  is destructed, only the coil can be interchanged. 
     A balance magnet  140   e  is attached to a side face of the balance wheel  140   b  on the main plate side to be opposed to the face of the main plate  102  on the front side. 
     Although it is preferable that as shown by FIG. 1, FIG.  3  and FIG. 5, an interval in a circumferential direction of the coil in the case of arranging the plurality of pieces of coils, is an interval in the circumferential direction of an S pole and an N pole of the balance magnet  140   e  arranged to be opposed to the coil multiplied by an integer, the interval may not be the same for all of the coils in the circumferential direction. Further, according to such structure of providing the plurality of pieces of coils, wirings among the respective coils may be wired in series such that currents generated at the respective coils by electromagnetic induction are not canceled by each other (refer to FIG.  1  through FIG.  4 ). 
     Alternatively, as a modified example, the wirings among the respective coils may be wired in parallel such that currents generated at the respective coils by electromagnetic induction are not canceled by each other (illustration is omitted for such constitution). 
     In reference to FIG. 7, the balance magnet  140   e  is provided with a mode in an annular shape (ring-like shape) and along its circumferential direction, for example, there are alternately provided magnet portions comprising 12 pieces of S poles  140   s   1  through  140   s   12  and 12 pieces of N poles  140   n   1  through  140   n   12  which are polarized in the up and down direction. Although a number of the magnet portions arranged in the annular shape (ring-like shape) in the balance magnet  140   e  is 12 in the example shown in FIG. 7, the number may be a plural number of 2 or more. In this case, it is preferable that a length of one chord of the magnet portion is substantially equal to an outer diameter of one coil provided to be opposed to the magnet portion. 
     A gap is provided between the balance magnet  140   e  and the coils  180 ,  180   a,    180   b  and  180   c.  The gap between the balance magnet  140   e  and the coils  180 ,  180   a,    180   b  and  180   c,  is determined such that magnetic force of the balance magnet  140   e  can effect influence on the coils  180 ,  180   a,    180   b  and  180   c  when the coils  180 ,  180   a,    180   b  and  180   c  are conducted. 
     When the coils  180 ,  180   a,    180   b  and  180   c  are not conducted, the magnetic force of the balance magnet  140   e  does not effect influence on the coils  180 ,  180   a,    180   b  and  180   c.  The balance magnet  140   e  is fixed to a face of the balance ring  140   b  on the side of the main plate by adhering or the like in a state in which one face of the balance magnet  140   e  is brought into contact with a ring-like rim portion of the balance wheel  140   b  and other face thereof is opposed to the face of the main plate  102  on the front side. 
     A first lead wire  182  is provided to conduct one terminal of the coil  180  and the first terminal member  168   a  and the second terminal member  168   b.  The first lead wire  182  is connected to a first lead connecting pattern of the circuit board  612  conducted to the one terminal of the coil  180 . 
     A second lead wire  184  is provided to conduct one terminal of the coil  180   c  and the hairspring holder  170 . The second lead wire  184  is connected to a second lead connecting pattern of the circuit board  612  conducted to the one terminal of the coil  180 c. 
     Further, although in FIG. 4, the thickness of the hairspring  140   c  (thickness in radius direction of balance with hairspring) is illustrated to exaggerate, the thickness is, for example, 0.021 millimeter. According to the balance magnet  140   e,  for example, an outer diameter thereof is about 9 millimeters, an inner diameter thereof ia bout 7 millimeters, a thickness thereof is about 1 millimeter and a magnetic flux density thereof is about 0.02 tesla. A turn number of each of the coils  180 ,  180   a,    180   b  and  180   c  is, for example, 8 turns and the coil wire diameter is about 25 micrometers. The gap STC between the balance magnet  140   e  and the coils  180 ,  180   a,    180   b  and  180   c  is, for example, about 0.4 millimeter. 
     (1.3) Operation of Balance with Hairspring when Circuit is opened. 
     An explanation will be given of operation of the balance with hairspring  140  when the coils  180 ,  180   a,    180   b  and  180   c  are not conducted, that is, when a circuit is opened in reference to FIG. 3, FIG.  4  and FIG.  11 . 
     The hairspring  140   c  is expanded and contracted in the radius direction of the hairspring  140   c  in accordance with rotational angle of rotating the balance with hairspring  140 . For example, in a state shown by FIG. 3, when the balance with hairspring  140  is rotated in the clockwise direction, the hairspring  140   c  is contracted in a direction toward the center of the balance with hairspring  140 , in contrast thereto, when the balance with hairspring  140  is rotated in the counterclockwise direction, the hairspring  140   c  is expanded in a direction remote from the center of the balance with hairspring  140 . 
     Therefore, in reference to FIG. 4, when the balance with hairspring  140  is rotated in the clockwise direction, the hairspring  140   c  is operated to approach the second terminal member  168   b.  In contrast thereto, when the balance with hairspring  140  is rotated in the counterclockwise direction, the hairspring  140   c  is operated to approach the first terminal member  168   a.    
     When the rotational angle (swing angle) of the balance with hairspring  140  is less than a constant threshold, for example, 180 degree, an amount of expanding and contracting the hairspring  140   c  in the radius direction is small and therefore, the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact also with the second terminal member  168   b.    
     When the rotational angle (swing angle) of the balance with hairspring  140  is equal to or larger than the constant threshold, for example, 180 degree, the amount of expanding and contracting the hairspring  140   c  in the radius direction becomes sufficiently large and accordingly, the hairspring  140   c  is brought into contact with both of the first terminal member  168   a  and the second terminal member  168   b.    
     For example, a portion  140   ct  of the hairspring  140   c  proximate to an outer end portion of the hairspring  140   c  is disposed in a clearance of about 0.04 millimeter between the first terminal member  168   a  and the second terminal member  168   b.  Therefore, in a state in which the swing angle of the balance with hairspring  140  falls in a range of exceeding 0 degree and less than 180 degree, the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact also with the second terminal member  168   b.  That is, the outer end portion of the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact also with the second terminal member  168   b  and accordingly, the coils  180 ,  180   a,    180   b  and  180   c  are not conducted and magnetic flux of the balance magnet  140   e  does not effect influence on the coils  180 ,  180   a,    180   b  and  180   c.  As a result, the swing angle of the balance with hairspring  140  is not attenuated by operation of the balance magnet  140   e  and the coils  180 ,  180   a,    180   b  and  180   c.    
     (1.4) Operation of Balance with Hairspring when Circuit is Closed 
     Next, an explanation will be given of operation of the balance with hairspring  140  when the coils  180 ,  180   a,    180   b  and  180   c  are conducted, that is, when the circuit is closed in reference to FIG. 5, FIG.  6  and FIG.  11 . That is, FIG.  5  and FIG. 6 show a case in which the swing angle of the balance with hairspring  140  is equal to or larger than 180 degree. 
     Further, in FIG. 6, the thickness of the hairspring  140   c  (thickness in radius direction of balance with hairspring) is illustrated to exaggerate. 
     When the swing angle of the balance with hairspring  140  becomes equal to or larger than 180 degree, the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  is brought into contact with the first terminal member  168   a  or the second terminal member  168   b.  Under the state, the coils  180 ,  180   a,    180   b  and  180   c  are conducted and a force for restraining rotational motion of the balance with hairspring  140  is exerted to the balance with hairspring  140  by induction current generated by a change in the magnetic flux of the balance magnet  140   e.  Further, by the operation, braking force for restraining rotation of the balance with hairspring  140  is exerted to the balance with hairspring  140  to thereby reduce the swing angle of the balance with hairspring  140 . 
     Further, when the swing angle of the balance with hairspring  140  is reduced to the range of exceeding 0 degree and less than 180 degree, there is brought about a state in which the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact with the second terminal member  168   b.  Therefore, as shown by FIG.  3  and FIG. 4, the outer end portion of the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact with the second terminal member  168   b  and accordingly, the coils  180 ,  180   a,    180   b  and  180   c  are not conducted and the magnetic flux of the balance magnet  140   e  does not effect influence on the coils  180 ,  180   a,    180   b  and  180   c.    
     (1.5) Effect of Balance Rotational Angle Control Mechanism 
     According to the mechanical time piece of the invention constituted in this way, the rotational angle of the balance with hairspring  140  can efficiently be controlled. 
     According to the invention, as explained above, there is constructed the constitution in which the balance rotational angle control mechanism is provided in the mechanical time piece constituted such that the escapement &amp; speed control apparatus includes the balance with hairspring repeating right rotation and left rotation, the escape wheel &amp; pinion rotated based on rotation of the front train wheel and the pallet fork for controlling rotation of the escape wheel &amp; pinion based on operation of the balance with hairspring and accordingly, accuracy of the mechanical time piece can be promoted without reducing a duration time period of the mechanical time piece. 
     That is, according to the invention, attention is paid to the correlation between the instantaneous rate and the swing angle by maintaining constant the swing angle, the change in the instantaneous rate is restrained and gain or loss of the time piece per day is adjusted to reduce. 
     In contrast thereto, according to the conventional mechanical time piece, by the relationship between the duration time period and the swing angle, the swing angle is changed with elapse of time. Further, by the relationship between the swing angle and the instantaneous rate, the instantaneous rate is changed with elapse of time. Therefore, it has been difficult to prolong the duration time period of the time piece capable of maintaining constant accuracy. 
     (2) Embodiment 2 of Mechanical Time Piece of the Invention 
     (2.1) Constitution of Embodiment 2 of Mechanical Time Piece of the Invention 
     Next, an explanation will be given of Embodiment 2 of a mechanical time piece according to the invention. In the following explanation, an explanation will be given mainly of a portion of Embodiment 2 of the mechanical time piece of the invention which is different from Embodiment 1 of the mechanical time piece of the invention. Therefore, content described below can be understood by referring to the explanation of Embodiment 1 of the mechanical time piece according to the invention. 
     With reference to FIG.  27  through FIG. 30, a circuit unit  660  is attached to the face of the front side of the main plate  102 . The circuit unit  660  includes the circuit board  612  and a coil unit  664 . The coil unit  664  includes a coil bridge  666  and four of the coils  180 ,  180   a,    180   b  and  180   c.  The coil unit  614  is attached to the face of the front side of the main plate  102  such that the coils  180 ,  180   a,    180   b  and  180   c  are opposed to the face of the balance wheel  140   b  on the side of the main plate. 
     The circuit board  612  is fixed to the face of the coil bridge  666  opposed to the balance wheel  140   b  by the circuit board fixing screws  618 . The circuit unit  660  is attached to the face of the front side of the main plate  102  by the circuit unit fixing screws  620 . That is, as shown by FIG.  1  through FIG. 4, the coil unit  664  is attached to the face of the main plate  102  on the front side in the state in which four of the coils  180 ,  180   a,    180   b  and  180   c  are respectively arranged to the circuit board  612  on the side of the main plate  102  such that the circuit board  612  is opposed to the face of the balance wheel  140   b  opposed to the main plate  102 . 
     The circuit board  612  is provided with three of coil conducting patterns (not illustrated) provided to conduct the coil  180 ,  180   a,    180   b  and  180   c  in series. 
     When the circuit unit  660  is attached to the main plate  102 , attachment may be carried out such that the circuit unit  660  is arranged to the surface of the main plate  102  such that a guiding circular arc portion  666   w  (refer to FIG. 30) of the coil bridge  666  matches the outer peripheral portion of the balance lower bearing  102   b  fixed to the main plate  102 . According to the constitution, the circuit unit  660  is attached to the main plate  102  before attaching the balance with hairspring  140  to the movement. 
     (2.2) Operation of Balance with Hairspring when Circuit Is Opened 
     As shown by FIG.  29  and FIG. 30, operation of the balance with hairspring when the circuit is opened, according to Embodiment 2 of the mechanical time piece of the invention, is similar to the above-described content explained in reference to FIG. 3, FIG.  4  and FIG.  11 . Therefore, a detailed explanation thereof will be omitted. 
     (2.3) Operation of Balance with Hairspring when Circuit Is Closed 
     As shown by FIG.  31  and FIG. 32, operation of the balance with hairspring when the circuit is closed, according to Embodiment 2 of the mechanical time piece of the invention, is similar to the above-described content explained in reference to FIG. 5, FIG.  6  and FIG.  11 . Therefore, a detailed explanation thereof will be omitted. 
     (3) Result of Simulation with Respect to Instantaneous Rate 
     Next, an explanation will be given of a result of a simulation with regard to the instantaneous rate which is carried out with regard to the mechanical time piece of the invention developed in order to resolve the problem of the conventional mechanical time piece. 
     In reference to FIG. 12, according to the mechanical time piece of the invention, first, as shown by plots of x marks and a slender line in FIG. 12, the time piece is adjusted in a state in which the instantaneous rate of the time piece is gained. According to the mechanical time piece of the invention, in the case in which the balance with hairspring  140  is rotated by a certain angle or more, when the outer end portion of the hairspring  140   c  is brought into contact with the first terminal member  168   a  or the second terminal member  168   b,  the effective length of the hairspring  140   c  is shortened and accordingly, the instantaneous rate is further gained. 
     That is, according to the mechanical time piece of the invention, in a state in which the outer end portion of the hairspring  140   c  is not brought into contact with the first terminal member  168   a  and is not brought into contact with the second terminal member  168   b,  as shown by the plots of x marks and the slender line in FIG. 12, in a state in which the main spring is completely wound up, the rate is about 18 seconds/day (gain of about 18 seconds per day), after elapse of 20 hours from the fully wound state, the instantaneous rate becomes about 13 seconds/day (gain of about 13 seconds/day) and after elapse of 30 hours from the fully wound state, the instantaneous rate becomes about −2 seconds/day (loss of 2 seconds per day). 
     Further, according to the mechanical time piece of the invention, when the balance rotational angle control mechanism is assumed not to operate, as shown by plots of triangle and a bold line in FIG. 12, in a state in which the outer end portion of the hairspring  140   c  is brought into contact with the first terminal member  168   a  or the second terminal member  168   b,  in the state in which the mainspring is completely wound up, the rate is about 25 seconds/day (gain of about 25 seconds per day), after elapse of 20 hours from the fully wound state, the instantaneous rate becomes about 20 seconds/day (gain of about 20 seconds per day) and after elapse of 30 hours from the fully wound state, the instantaneous rate becomes about 5 seconds/day (gain of about 5 seconds per day). 
     In contrast thereto, according to the mechanical time piece of the invention, when the balance rotational angle control mechanism is operated, as shown by plots of black circle and an extremely bold line in FIG. 12, the instantaneous rate can be maintained at about 5 seconds/day (state of gaining by about 5 seconds per day is maintained) in the state in which the balance rotational angle control mechanism is operated, that is, until elapse of 27 hours from the state in which the mainspring is completely wound up and after elapse of 30 hours from the fully wound state, the instantaneous rate becomes about −2 seconds/day (loss of about 2 seconds per day). 
     According to the mechanical time piece having the balance rotational angle control mechanism of the invention, by controlling the swing angle of the balance with hairspring, the change in the instantaneous rate of the time piece is restrained and accordingly, in comparison with the conventional mechanical time piece shown by plots of square and an imaginary line in FIG. 12, an elapse time period from the fully wound state in which the instantaneous rate is about 0 through 5 seconds/day can be prolonged. 
     That is, according to the mechanical time piece of the invention, a duration time period in which the instantaneous rate falls within about plus and minus 5 seconds/day is about 32 hours. A value of the duration time period is a duration time period in which the instantaneous rate in the conventional mechanical time piece falls within about plus and minus 5 seconds/day or about 22 hours multiplied by 1.45. 
     Therefore, according to the mechanical time piece of the invention, in comparison with the conventional mechanical time piece, there is achieved the result of the simulation in which accuracy is every excellent. 
     (4) Switch Adjusting Apparatus Used in Mechanical Time Piece of the Invention 
     Next, an explanation will be given of a switch adjusting apparatus used for adjusting positions of the first terminal member and the second terminal member relative to the portion  140  proximate to the outer end portion of the hairspring and an interval between the first terminal member and the second terminal member. 
     In reference to FIG.  15  and FIG. 16, a switch adjusting apparatus  200  includes a switch member  202 , a first guide pin  204  and a second guide pin  206  provided to the switch member  202 . The switch member  202  are formed by a metal such as iron or brass or plastic. The first guide pin  204  and the second guide pin  206  are formed by a metal such as iron or brass or plastic. The first guide pin  204  and the second guide pin  206  may be formed as members separate from the switch member  202  and fixed to the switch member  202  or the first guide pin  204  and the second guide pin  206  may be formed integrally with the switch member  202 . The switch member  202  is attached to the balance bridge (not illustrated) to be rotatable centering on the rotational center of the balance with hairspring  140 . 
     A switch insulating member  210  is arranged to a side of the switch member  202  opposed to a side thereof opposed to the balance with hairspring  140 . The switch insulating member  210  is formed by an insulating material of plastic or the like and is formed by an elastically deformable material. A first long hole  210   a  is provided to the switch insulating member  210 , the first guide pin  204  and the second guide pin  206  are fitted into the first long hole  210   a  and the switch insulating member  210  is arranged slidably to the switch member  202 . A direction of sliding the switch insulating member  210  coincides with a straight line passing through a center of the first guide pin  204  or the second guide pin  206  and the center of the balance with hairspring  140 . 
     A switch interval adjusting lever  212  is provided to the switch insulating member  210  rotatably by a slip mechanism. An outer peripheral portion of a cylindrical portion of the switch interval adjusting lever  212  is integrated to a circular portion provided at a portion of the first long hole  210   a  of the switch insulating member  210 . The circular portion provided at the portion of the first long hole  210   a  of the switch insulating member  210 , is constituted to be fitted to the cylindrical portion of the switch interval adjusting lever  212  by way of elastic force and accordingly, rotation of the switch interval adjusting lever  212  can be fixed at an arbitrary position. 
     A first terminal portion  212   a  and a second terminal portion  212   b  are provided on a side of the switch interval adjusting lever  212  opposed to the balance with hairspring  140 . The first terminal portion  212   a  and the second terminal portion  212   b  are provided at positions eccentric to the rotational center of the switch interval adjusting lever  212 . The first terminal portion  212   a  and the second terminal portion  212   b  are formed to constitute line symmetry relative to a straight line including the rotational center of the switch interval adjusting lever  212 . 
     The portion  140   ct  proximate to the outer end portion of the hairspring  140   c  is disposed in a clearance SSW between the first terminal portion  212   a  and the second terminal portion  212   b.  For example, the clearance SSW is about 0.06 millimeter. 
     The first terminal portion  212   a  and the second terminal portion  212   b  can be rotated by rotating the switch interval adjusting lever  212  in a direction of a narrow mark  220  (clockwise direction in FIG. 15) or a direction of an arrow mark  222  (counterclockwise direction in FIG.  15 ). Thereby, the distance SSW between the first terminal portion  212   a  and the second terminal portion  212   b  in the direction of the straight line passing through the center of the balance with hairspring  140  can be changed. 
     Further, a switch position adjusting lever  232  is provided to the switch member  202  rotatably by a slip mechanism and can be fixed at an arbitrary position. An eccentric portion  232   a  of the switch position adjusting lever  232  is fitted to a second long hole  210   b  of the switch insulating member  210 . A direction of a central axis line in the longitudinal direction of the second long hole  210   b  is orthogonal to the direction of the straight line passing through the center of the first guide pin  204  or the second guide pin  206  and the center of the balance with hairspring  140 . That is, the direction of the central axis line in the longitudinal direction of the second long hole  210   b  is orthogonal to the direction of the central axis line in the longitudinal direction of the first long hole  210   a.  Elastic deformable portions  210   c  and  210   d  of the switch insulating member  210  the widths of which are formed to be elastically deformable, are provided at both end portions in the longitudinal direction of the second long hole  210   b.  A rigid portion  210   e  of the switch insulating member  210 , the width of which is formed not to be elastically deformable, is provided on an outer side (side remote from the outer end portion of the mainspring  140   c ) of the second long hole  210   b.  Therefore, the width of the rigid portion  210   e  is formed to be larger than the widths of the elastically deformable portions  210   c  and  210   d.  The inner side of the rigid portion  210   e  is arranged to be brought into contact with the eccentric portion  232   a  of the switch position adjusting lever  232 . 
     By rotating the switch position adjusting lever  232  in a direction of an arrow mark  240  (clockwise direction in FIG.  15 ), the eccentric portion  232   a  can be rotated. Thereby, the switch insulating member  210  can be moved in a direction toward the center of the balance with hairspring  140  (direction of arrow mark  242  in FIG.  15  and FIG. 16) in the direction of the straight line passing through the center of the balance with hairspring  140 . As a result, the first terminal portion  212   a  is moved to be proximate to the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  and the second terminal portion  212   b  is moved to be remote from the portion  140   ct  proximate to the outer end portion of the hairspring  140   c.    
     By rotating the switch position adjusting lever  232  in a direction of an arrow mark  244  (counterclockwise direction in FIG.  15 ), the eccentric portion  232   a  can be rotated. Thereby, the switch insulating member  210  can be moved in a direction remote from the center of the balance with hairspring  140  (direction of arrow mark  246  in FIG.  15  and FIG.  16 ). As a result, the first terminal portion  212   a  is moved to be remote from the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  and the second terminal portion  212   b  is moved to be proximate to the portion  140   ct  proximate to the outer end portion of the hairspring  140   c.    
     FIG.  17  and FIG. 18 illustrate a state in which the switch position adjusting lever  232  is rotated in the direction of the arrow mark  240  (clockwise direction in FIG. 15) in FIG.  15  and FIG.  16 . By rotating the switch position adjusting lever  232 , the eccentric portion  232   a  is rotated, the switch insulating member  210  is moved in the direction toward the center of the balance with hairspring  140 , the first terminal portion  212   a  becomes proximate to the portion  140   ct  proximate to the outer end portion of the hairspring  140   c  and the second terminal portion  212   b  becomes remote from the portion  140   ct  proximate to the outer end portion of the hairspring  140   c.  In such operation of rotating the switch position adjusting lever  232 , the clearance SSW between the first terminal portion  212   a  and the second terminal portion  212   b  remains unchanged. 
     FIG.  19  and FIG. 20 illustrate a state in which the switch interval adjusting lever  212  is rotated in the direction of the arrow mark  222  (counterclockwise direction in FIG. 15) in FIG.  15  and FIG.  16 . By rotating the switch interval adjusting lever  212 , the first terminal portion  212   a  and the second terminal portion  212   b  are rotated, the distance between the first terminal portion  212   a  and the second terminal portion  212   b  in the direction of the straight line passing through the center of the balance with hairspring  140 , is reduced. Therefore, the distance between the first terminal portion  212   a  and the second terminal portion  212   b  in the direction of the straight line passing through the center of the balance with hairspring  140  is changed to SSW2 smaller than SSW. 
     As has been explained, according to the mechanical time piece of the invention, by using the switch adjusting apparatus  200 , the positions of the first terminal portion  212   a  and the second terminal portion  212   b  relative to the portion  140   ct  proximate to the outer end portion of the hairspring can be adjusted and by adjusting the interval between the first terminal portion  212   a  and the second terminal portion  212   b,  the distance between the portion  140   ct  proximate to the outer end portion of the hairspring and the first terminal portion  212   a  and the distance between the portion  140   ct  proximate to the outer end portion of the hairspring and the second terminal portion  212   b  can be adjusted. 
     By applying the above-described two adjusting mechanisms to the switch adjusting apparatus, swing angles for making the switch ON/OFF can easily be adjusted. 
     Therefore, when the switch adjusting apparatus  200  is used in the mechanical time piece of the invention shown in FIG.  1  and FIG. 2, the first terminal portion  212   a  may be arranged in place of the first terminal member  168   a  and the second terminal portion  212   b  may be arranged in place of the second terminal member  168   b.    
     The switch adjusting apparatus for the mechanical time piece according to the invention is applicable to a regulating apparatus for an existing mechanical time piece. In such a case, the first terminal portion  212   a  corresponds to a regulator and the second terminal portion  212   b  corresponds to a hairspring rod. 
     By such a constitution, the regulator and the hairspring rod of the mechanical time piece can be adjusted accurately and efficiently. 
     INDUSTRIAL APPLICABILITY 
     The mechanical time piece of the invention is provided with the simple structure and is suitable for realizing a mechanical time piece having very excellent accuracy. 
     Further, the mechanical time piece of the invention is provided with the new balance rotational angle control mechanism and accordingly, a mechanical time piece having high accuracy can be fabricated further efficiently than a conventional time piece.