Abstract:
A mechanical timepiece has a power source comprised of a mainspring for undergoing rewinding movement to generate a rotational force. A front train wheel undergoes rotation in accordance with a rotational force generated during rewinding movement of the mainspring. An escapement/speed-control device controls rotation of the front train wheel. The escapement/speed-control device has a balance with a hairspring for undergoing alternately repeating rotational movement in left and right directions. An escape wheel and pinion undergoes rotation in accordance with rotation of the front train wheel. A pallet fork controls rotation of the escape wheel and pinion in accordance with rotational movement of the balance. A switch mechanism outputs an ON signal when a rotation angle of the balance reaches a predetermined threshold angle or greater, outputs an OFF signal when the rotation angle of the balance does not exceed the predetermined threshold angle. A rotation angle control mechanism supresses rotation of the balance when the switch mechanism outputs an ON signal.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a mechanical timepiece having a mechanical timepiece having a balance-with-hairspring rotation angle control mechanism structured to apply to the balance with hairspring such a force as suppressing against rotation of the balance with hairspring. Also, the invention relates to a mechanical timepiece having a switch adjuster mechanism used to adjust positions of a first contact member and second contact member relative to a near-outer-end portion of the stud-mainspring and a spacing between the first contact member and the second contact member. Furthermore, the invention relates to a mechanical-timepiece adjuster device for adjusting positions of first contact and second contact members relative to a near-outer-portion of the stud mainspring. 
     Background Information 
     In the conventional mechanical timepiece, as shown in FIG.  13  and FIG. 14 the mechanical-timepiece movement  1100  (mechanical body) has a main plate  1102  constituting a base plate for the movement. A hand setting stem  1110  is rotatably assembled in a hand-setting-stem guide hole  1102   a  of the main plate  1102 . A dial  1104  (shown by the virtual line in FIG. 14) is attached to the movement  1100 . 
     Generally, a main plate has two opposite sides, one side having a dial is referred to as a “back side” of the movement and the opposite side to the side having the dial is referred to as a “front side”. The train wheel assembled on the “front side” of the movement is referred to as a “front train wheel” and the train wheel assembled on the “back side” of the movement is as a “back train wheel”. 
     The hand setting stem  1110  is determined in axial position by a switch device including a setting lever  1190 , a yoke  1192 , a yoke spring  1194  and a back holder  1196 . A winding pinion  1112  is rotatably provided on a guide axis portion of the hand setting stem  1110 . When rotating the hand setting stem  1110  in a state the hand setting stem  1110  is in a first hand-setting-stem position closest to an inward of the movement along a rotation axis direction (0 the stage), the winding pinion  1112  rotates through rotation of the clutch wheel. A crown wheel  1114  rotates due to rotation of the winding pinion  1112 . A ratchet wheel  1116  rotates due to rotation of the crown wheel  1114 . By rotating the ratchet wheel  1116 , a mainspring  1122  accommodated in a barrel complete  1120  is wound up. A center wheel and pinion  1124  rotates due to rotation of the barrel complete  1120 . An escape wheel and pinion  1130  rotates through rotation of a fourth wheel and pinion  1128 , third wheel and pinion  1126  and center wheel and pinion  1124 . The barrel complete  1120 , center wheel and pinion  1124 , third wheel and pinion  1126  and fourth wheel and pinion  1128  constitutes a front train wheel. 
     An escapement/speed-control device for controlling rotation of the front train wheel includes a balance with hairspring  1140 , an escape wheel and pinion  1130  and pallet fork  1142 . The balance with hairspring  1140  includes a balance stem  1140   a , a balance wheel  1140   b  and a stud mainspring  1140   c . Based on the center wheel and pinion  1124 , an hour pinion  1150  rotates simultaneously. A minute hand  1152  attached on the hour wheel  1150  indicates “minute”. The hour pinion  1150  is provided with a slip mechanism for the center wheel and pinion  1124 . Based on rotation of the hour pinion  1150 , an hour wheel  1154  rotates through rotation of a minute wheel. An hour hand  1156  attached on the hour wheel  1154  indicates “hour”. 
     The barrel complete  1120  is rotatably supported relative to the main plate  1102  and barrel bridge  1160 . The center wheel and pinion  1124 , the third wheel and pinion  1126 , the fourth wheel and pinion  1128  and the escape wheel and pinion  1130  are rotatably supported relative to the main plate  1102  and train wheel bridge  1162 . The pallet fork  1142  is rotatably supported relative to the main plate  1102  and pallet fork bridge  1164 . The balance with hair spring  1140  is rotatably supported relative to the main plate  1102  and balance bridge  1166 . 
     The stud mainspring  1140   c  is a thin leaf spring in a spiral (helical)form having a plurality of turns. The stud mainspring  1140   c  at an inner end is fixed to a stud ball  1140   d  fixed on the balance stem  1140   a , and the stud mainspring  1140   c  at an outer end is fixed by screwing through a stud support  1170   a  attached to a stud bridge  1170  fixed on the balance bridge  1166 . 
     A regulator  1168  is rotatably attached on the balance bridge  1166 . A stud bridge  1168   a  and a stud rod  1168   b  are attached on the regulator  1168 . The stud mainspring  1140   c  has a near-outer-end portion positioned between the stud bridge  1168   a  and the stud rod  1168   b.    
     Generally, in the conventional representative mechanical timepiece, as shown in FIG. 8 the torque on the mainspring torque also decreases while being rewound as the sustaining time elapses from a state the mainspring is fully wound (full winding state). For example, in the case of FIG. 8, the mainspring torque in the full winding state is about 27 g·cm, which becomes about 23 g·cm at a lapse of 20 hours from the full winding state and about 18 g·cm at a lapse of 40 hours from the full winding state. 
     Generally, in the conventional representative mechanical timepiece, as shown in FIG. 9 the decrease of mainspring torque also decreases a swing angle of the balance with hairspring. For example, in the case of FIG. 9, the swing angle of the balance with hairspring is approximately 240 degrees to 270 degrees when the mainspring torque is 25 g·cm to 28 g·cm while the swing angle of the balance with hairspring is approximately 180 degrees to 240 degrees when the mainspring torque is 20 g·cm to 25 g·cm. 
     Referring to FIG. 10, there is shown transition of an instantaneous watch error (numeral value indicative of timepiece accuracy) against a swing angle of a balance with hairspring in the conventional representative mechanical timepiece. Here, “instantaneous watch error” refers to “a value representative of fast or slow of a mechanical timepiece at a lapse of one day on the assumption that the mechanical timepiece is allowed to stand while maintaining a state or environment of a swing angle of a balance with hairspring upon measuring a watch error”. In the case of FIG. 10, the instantaneous watch error delays when the swing angle of the balance with hairspring is 240 degrees or greater or 200 degrees or smaller. 
     For example, in the conventional representative mechanical timepiece, as shown in FIG. 10 the instantaneous watch error is about 0 degree to 5 seconds per day (about 0 degree to 5 seconds fast per day) when the swing angle of the balance with hairspring is about 200 degrees to 240 degrees while the instantaneous watch error becomes about −20 seconds per day (about 20 seconds slow per day) when the swing angle of the balance with hairspring is about 170 degrees. 
     Referring to FIG. 12, there is shown a transition of an instantaneous watch error and a lapse time upon rewinding the mainspring from a full winding state in the conventional representative mechanical timepiece. Here, in the conventional mechanical timepiece, the “watch error” indicative of timepiece advancement per day or timepiece delay per day is shown by an extremely thin line in FIG. 12, which is obtainable by integrating over 24 hours an instantaneous watch error against a lapse time of rewinding the mainspring from the full winding. 
     Generally, in the conventional mechanical timepiece, the instantaneous watch error slows down because the mainspring torque decreases and the balance-with-hairspring swing angle decreases as the sustaining time elapses with the mainspring being rewound from a full winding state. Due to this, in the conventional mechanical timepiece, the instantaneous watch error in a mainspring full winding state is previously put forward in expectation of timepiece delay after lapse of a sustaining time of 24 hours, thereby previously adjusting plus the “watch error” representative of timepiece advancement or delay per day. 
     For example, in the conventional representative mechanical timepiece, as shown by an extreme thin line in FIG. 12 the instantaneous watch error in a full winding state is about 3 seconds per day (3 seconds fast per day). However, when 20 hour elapses from the full winding state, the instantaneous watch error becomes about −3 seconds per day (about 3 seconds slow per day). When 24 hours elapses from the full winding state, the instantaneous watch error becomes about −8 seconds per day (about 8 seconds slow per day). When 30 hours elapses from the full winding state, the instantaneous watch error becomes about −16 seconds per day (about 16 seconds slow per day). 
     Incidentally, as a conventional balance-with-hairspring swing angle adjusting device there is a disclosure, for example, in Japanese Utility model Laid-open No. 41675/1979 of one having a swing angle adjusting plate to generate over-current each time a magnet of the balance with hairspring approaches by swinging and give brake force to the balance with hairspring. 
     It is an object of the invention to provide a mechanical timepiece having a balance-with-hairspring rotation angle control mechanism that can control the swing angle of the balance with hairspring to be fallen within a constant range. 
     Furthermore, an object of the invention is to provide a mechanical timepiece which is less changed in watch error and accurate even after lapse of time from the full winding state. 
     Furthermore, an object of the invention is to provide a mechanical timepiece having a switch adjuster device used to adjust positions of first contact and second contact members relative to a near-outer-end portion of the stud mainspring and a spacing between the first contact and second contact members. 
     Furthermore, an object of the invention is to provide a mechanical-timepiece adjuster device for adjusting positions of first contact and second contact members relative to a near-outer-end portion of the stud mainspring. 
     SUMMARY OF THE INVENTION 
     The present invention is, in a mechanical timepiece structured having a mainspring constituting a power source for the mechanical timepiece, a front train wheel rotating due to rotational force given upon rewinding the mainspring and an escapement/speed-control device for controlling rotation of the front train wheel, the escapement/speed-control device being structured including a balance with hairspring alternately repeating right and left rotation, an escape wheel and pinion rotating based on rotation of the front train wheel and a pallet fork controlling rotation of the escape wheel and pinion based on operation of the balance with hairspring, characterized by comprising: a switch mechanism structured to output an on signal when a rotation angle of the balance with hairspring becomes a predetermined threshold or greater, and an off signal when the rotation angle of the balance with hairspring is not excess of the predetermined threshold; and a balance-with-hairspring rotation angle control mechanism structured to apply such a force as suppressing against rotation of the balance with hairspring when the switch mechanism outputs an on signal. 
     In the mechanical timepiece of the invention, the switch mechanism is preferably structured to output an on signal when a stud mainspring provided on the balance with hairspring contacts a contact member constituting a switch lever. 
     Also, in the mechanical timepiece of the invention, the balance-with-hairspring rotation angle control mechanism preferably includes a balance magnet provided on the balance with hairspring and a coil arranged to exert a magnetic force to the balance magnet, and the coil being structured to apply a magnetic force to the balance magnet to suppress rotation of the balance with hairspring when the switch mechanism outputs an on signal, and not to apply a magnetic force to the balance magnet when the switch mechanism outputs an off signal. 
     By using a balance-with-hairspring rotation angle control mechanism thus structured, it is possible to effectively control the rotation angle of the balance with hairspring of the mechanical timepiece thereby improving accuracy for the mechanical timepiece. 
     Also, in the mechanical timepiece of the invention, the switch mechanism preferably includes a first contact member and a second contact member, and further comprising an adjuster device for changing a spacing between the first contact member and the second contact member. 
     Also, in the mechanical timepiece of the invention, the switch mechanism preferably includes a first contact member and a second contact member, and further comprising an adjuster device for simultaneously move the first contact member and the second contact member relative to a rotation center of the balance with hairspring. 
     Also, in the mechanical timepiece of the invention, the adjuster device preferably includes a switch body-provided rotatable about a rotation center of the balance with hairspring, a switch insulating member arranged slidable relative to the switch body, and a switch spacing adjusting lever having a first contact and a second contact. 
     Also, in the mechanical timepiece of the invention, the adjuster device preferably includes a switch body provided rotatable about a rotation center of the balance with hairspring, a switch insulating member arranged slidable relative to the switch body, and a switch position adjusting lever having an eccentric portion provided rotatable relative to the switch body and to be fit in an elongate hole of the switch insulating member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing a schematic form of a movement front side of a mechanical timepiece of the present invention (in FIG. 1, parts are partly omitted and bridge members are shown by virtual lines). 
     FIG. 2 is a schematic fragmentary sectional view showing the movement of the invention (in FIG. 2, parts are partly omitted). 
     FIG. 3 is a magnified fragmentary sectional view showing a schematic form of a balance with hairspring part of the mechanical timepiece of the invention in a state a switch mechanism is off. 
     FIG. 4 is a magnified fragmentary sectional view showing a schematic form of a balance with hairspring part of the mechanical timepiece of the invention in a state a switch mechanism is off. 
     FIG. 5 is a magnified fragmentary sectional view showing a schematic form of a balance with hairspring part of the mechanical timepiece of the invention in a state the switch mechanism is on. 
     FIG. 6 is a magnified fragmentary sectional view showing a schematic form of a balance with hairspring part of the mechanical timepiece of the invention in a state the switch mechanism is on. 
     FIG. 7 is a perspective view showing a schematic form of a balance magnet used in the mechanical timepiece of the invention. 
     FIG. 8 is a graph schematically showing a relationship between a lapse of time in rewinding from a full winding state and a mainspring torque in the mechanical timepiece. 
     FIG. 9 is a graph schematically showing a relationship between a swing angle of a balance with hairspring and a mainspring torque in the mechanical timepiece. 
     FIG. 10 is a graph schematically showing a relationship between a swing angle of a balance with hairspring and an instantaneous watch error in the mechanical timepiece. 
     FIG. 11 is a block diagram showing an operation when the circuit is open and an operation when the circuit is close in the mechanical timepiece of the invention. 
     FIG. 12 is a graph schematically showing a relationship between a lapse of time in rewinding from a full winding state and an instantaneous watch error in the mechanical timepiece of the invention and conventional mechanical timepiece. 
     FIG. 13 is a plan view showing a schematic form of a movement front side of a conventional mechanical timepiece (in FIG. 13, parts are partly omitted and bridge members are shown by virtual lines). 
     FIG. 14 is a schematic fragmentary sectional view of a movement of a conventional mechanical timepiece (in FIG. 14, parts are partly omitted). 
     FIG. 15 is a plan view showing a switch adjuster device used in the mechanical timepiece of the invention. 
     FIG. 16 is a sectional view showing a switch adjuster device used in the mechanical timepiece of the invention. 
     FIG. 17 is a plan view showing a state a switch position adjusting lever is rotated in the switch adjuster device used in the mechanical timepiece of the invention. 
     FIG. 18 is a sectional view showing a state a switch position-adjusting lever is rotated in the switch adjuster device used in the mechanical timepiece of the invention. 
     FIG. 19 is a plan view showing a state a switch space-adjusting lever is rotated in the switch adjuster device used in the mechanical timepiece of the invention. 
     FIG. 20 is a sectional view showing a state a switch space-adjusting lever is rotated in the switch adjuster device used in the mechanical timepiece of the invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereunder, embodiments of a mechanical timepiece of the present invention will be explained based on the drawings. 
     Referring to FIG.  1  and FIG. 2, in an embodiment of a mechanical timepiece of the invention, a movement (mechanical body)  100  of the mechanical timepiece has a main plate  102  structuring a base plate for the movement. A hand setting stem  110  is rotatably assembled in a winding-stem guide hole  102   a  of the main plate  102 . A dial  104  (shown by a virtual line in FIG. 2) is attached on the movement  100 . 
     The hand setting stem  110  has a squared portion and a guide shaft portion. A clutch wheel (not shown) is assembled on the square portion of the hand setting stem  110 . The clutch wheel has a same rotation axis as a rotation axis of the hand setting stem  110 . That is, the clutch wheel is provided having a squared hole and rotated based on rotation of the hand setting stem  110  by fitting the squared hole on the squared portion of the hand setting stem  110 . The clutch wheel has teeth A and teeth B. The teeth A are provided in the clutch wheel at an end close to a center of the movement. The teeth B are provided in the clutch wheel at an end close to an outside of the movement. 
     The movement  100  is provided with a switch device to determine an axial position of the winding stem  110 . The switch device includes a setting lever  190 , a yoke  192 , a yoke spring  194  and a setting lever jumper  196 . The hand-setting stem  110  is determined in rotation-axis position based on rotation of the setting lever. The clutch wheel is determined in rotation-axis position based on rotation of the yoke. The yoke is to be determined at two positions in rotational direction. 
     A winding pinion  112  is rotatably provided on the guide shaft portion of the hand setting stem  110 . When the hand setting stem  110  is rotated in a state that the hand setting stem  110  is positioned at a first hand setting stem position closest to a movement inner side along the rotation axis direction (in a 0th stage), the winding pinion  112  is structurally rotated through rotation of the clutch wheel. A crown wheel  114  is structured to rotate due to rotation of the winding pinion  112 . A ratchet wheel  116  is structured to rotate due to rotation of the crown wheel  114 . 
     The movement  100  has as a power source a mainspring  122  accommodated in a barrel complete  120 . The mainspring  122  is made of an elastic material having springiness, such as iron. The mainspring  122  is structured for rotation due to rotation of the ratchet wheel  116 . 
     A center wheel and pinion  124  is structured for rotation due to rotation of the barrel complete  120 . A third wheel and pinion  126  is structured rotatable based on rotation of the center wheel and pinion  124 . A fourth wheel and pinion  128  is structured rotatable based on rotation of the third wheel and pinion  126 . An escape wheel and pinion  130  is structured for rotation due to rotation of the fourth wheel and pinion  128 . The barrel complete  120 , the center wheel and pinion  124 , the third wheel and pinion  126  and the fourth wheel and pinion  128  constitute a front train wheel. 
     The movement  100  has an escapement/governing device to control rotation of the front train wheel. The escapement/governing device includes a balance with hairspring  140  to repeat right and left rotation with a constant period, an escape wheel and pinion  130  to rotate based on rotation of the front train wheel, and pallet fork  142  to control rotation of the escape wheel and pinion  130  based on the operation of 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 stud mainspring  140   c . The stud mainspring  140   c  is made of an elastic material having springiness, such as “elinvar”. That is, the stud mainspring  140   c  is made of a metallic conductive material. 
     Based on rotation of the center wheel and pinion  124 , an hour pinion  150  simultaneously rotates. The hour pinion  150  is structured having a minute hand  152  to indicate “minute”. The hour pinion  150  is provided with a slip mechanism having predetermined slip torque to the center wheel and pinion  124 . 
     Based on rotation of the hour pinion  150 , a minute wheel (not shown) rotates. Based on rotation of the minute wheel, an hour wheel  154  rotates. The hour wheel  154  is structured having an hour hand  156  to indicate “hour”. 
     The barrel complete  120  is supported for rotation relative to the main plate  102  and barrel bridge  160 . The center wheel and pinion  124 , third wheel and pinion  126 , fourth wheel and pinion  128  and escape wheel and pinion  130  are supported for rotation relative to the main plate  102  and train wheel bridge  162 . The pallet fork  142  is supported for rotation relative to the main plate  102  and pallet bridge  164 . 
     The balance with hairspring  140  is supported for rotation relative to the main plate  102  and balance bridge  166 . That is, the balance stem  140   a  has an upper tenon  140   a   1  supported for rotation relative to a balance upper bearing  166   a  fixed on the balance bridge  166 . The balance upper bearing  166   a  includes a balance upper hole jewel and a balance upper bridge jewel. The balance upper hole jewel and the balance upper balance jewel are formed of an insulating material such as ruby. 
     The balance stem  140   a  has a lower tenon  140   a   2  supported for rotation relative to the balance lower bearing  102   b  fixed on the main plate  102 . The balance lower bearing  102   b  includes a balance lower hole jewel and a balance lower-bridge jewel. The balance lower hole jewel and the balance lower bridge jewel are made of an insulating material such as ruby. 
     The stud mainspring  140   c  is a thin leaf spring in a spiral (helical) form having a plurality of turns. The stud mainspring  140   c  at an inner end is fixed to a stud ball  140   d  fixed on the balance stem  140   a , and the stud mainspring  140   c  at an outer end is screwed through a stud support  170   a attached to a stud bridge  170  rotatably fixed on the balance bridge  166 . The balance bridge  166  is made of a metallic conductive material such as brass. The stud bridge  170  is made of a metallic conductive material such as iron. 
     Next, explanation will be made on a switch mechanism of the mechanical timepiece of the invention. 
     Referring to FIG.  1  and FIG. 2, a switch lever  168  is rotatably attached on the balance bridge  166 . A first contact member  168   a  and a second contact member  168   b  are attached on a switch lever  168 . The switch lever  168  is attached on the balance bridge  166  for rotation about a rotation center of the balance with hairspring  140 . The switch lever  168  is formed of a plastic insulating material such as polycarbonate. The first contact member  168   a  and the second contact member  168   b  are made of a metallic conductive material such as brass. The stud mainspring  140   c  at its near-outer-end portion is positioned between the first contact member  168   a  and the second contact member  168   b.    
     Coils  180 ,  180   a ,  180   b ,  180   c  are attached on a front surface of the main plate  102  in a manner facing to a main-plate-side surface of the balance wheel  140   b . The number of coils, as shown in FIG.  1  and FIG. 2, is for example four, but may be one, two, three or four or more. 
     A balance magnet  140 e is attached on the main-plate-side surface of the balance wheel  140   b  in a manner facing to the front surface of the main plate  102 . 
     As shown in FIG. 1, FIG.  3  and FIG. 5, in the case of arranging a plurality of coils, a circumferential interval of the coils is preferably greater integer-times a circumferential interval between S and N poles of the balance magnet  140   e  arranged opposite to the coils. However, all the coils may not have a same interval in the circumferential direction. Furthermore, in such a structure as having a plurality of coils, the interconnections between the coils are preferably connected in series not to mutually cancel current generated on each coil due to electromagnetic induction. Otherwise, the interconnections between the coils may be connected in parallel not to mutually cancel current generated on each coil due to electromagnetic induction. 
     Referring to FIG. 7, the balance magnet  140   e  has an annular (ring-formed) shape and is alternately provided, along a circumferential direction, with magnet portions constituted, for example, by twelve S poles  140   s   1 - 140   s   12  and twelve N poles  140   n   1 - 140   n   12  that are vertically polarized. Although the number of magnet portions arranged annular (in a ring form) in the balance magnet  140   e  in the example shown in FIG. 10 is twelve, it may be in a plurality of two or more. Here, it is preferred to provide the magnet portion with one bowstring length nearly equal to an outer diameter of one coil provided opposite to the magnet portion. 
     A gap is provided between the balance magnet  140   e  and the coil  180 ,  180   a ,  180   b ,  180   c . The gap between the balance magnet  140   e  and the coil  180 ,  180   a ,  180   b ,  180   c  is determined such that the balance magnet  140   e  has a magnetic force capable of giving effects upon the coil  180 ,  180   a ,  180   b ,  180   c  when the coil  180 ,  180   a ,  180   b ,  180   c  is energized. 
     When the coil  180 ,  180   a ,  180   b ,  180   c  is not energized, the magnetic force on the balance magnet  140   e  will not have effects on the coil  180 ,  180   a ,  180   b ,  180   c . The balance magnet  140   e  is fixed, for example, through adhesion to the main-plate-side surface of the balance wheel  140   b  in such a state that one surface is in contact with a ring rim of the balance wheel  140   b  and the other surface facing to the front surface of the main plate  102 . 
     A first lead wire  182  is provided to connect between one terminal of the coil  180  and a first coil terminal  168   a  and second coil terminal  168   b . A second lead wire  184  is provided to connect between one terminal of the coil  180   c  and the stud bridge  170 . 
     Incidentally, the stud mainspring  140   c  although illustrated by exaggeration in FIG. 4 has a thickness (radial thickness of the balance with hairspring) of 0.021 millimeter, forexample. The balance magnet  140   e  has, forexample,an outer diameter of approximately 9 millimeters, an inner diameter of approximately 7 millimeters, a thickness of approximately 1 millimeter and a magnetic flux density of approximately 0.02 tesla. The coil  180 ,  180   a ,  180   b ,  180   c  respectively has the number of turns, for example, of 8 turns and a coil diameter of approximately 25 micrometers. The gap STC between the balance magnet  140   e  and the coil  180 ,  180   a ,  180   b ,  180   c  is, for example, approximately 0.4 millimeter. 
     Referring to FIG. 3, FIG.  4  and FIG. 11, explanation will be made on the operation of the balance with hairspring  140  when the coils  180 ,  180   a ,  180   b ,  180   c  are not energized, i.e. when the circuit is open. 
     The stud mainspring  140   c  expands and contracts radially of the stud mainspring  140   c  depending on a rotation angle of stud mainspring  140  rotation. For example, in the state shown in FIG. 3, when the balance with hairspring rotates clockwise, the stud mainspring  140   c  contracts in a direction toward a center of the balance with hairspring  140 . On the contrary, when the balance with hairspring  140  rotates counterclockwise, the balance with hairspring  140   c  expands in a direction away from the center of the balance with hairspring  140 . 
     Consequently, in FIG. 4, when the balance with hairspring  140  rotates clockwise, the balance with hairspring  140   c  operates in a manner approaching the second contact member  168   b . Contrary to this, when the balance with hairspring  140  rotates counterclockwise, the stud mainspring  140   c  operates in a manner approaching the first contact member  168   a.    
     Where the rotation angle of the balance with hairspring  140  (swing angle) is less than a constant threshold, e.g. 180 degrees, the stud mainspring  140   c  has a less expansion/contraction amount in the radial direction. Consequently, the stud mainspring  140   c  does not contact the first contact member  168   a , and does not contact the second contact member  168   b.    
     Where the rotation angle of the balance with hairspring  140  (swing angle) is equal to or greater than the constant threshold, e.g. 180 degrees, the stud mainspring  140   c  becomes great in expansion/contraction amount in the radial direction. Consequently, the stud mainspring  140   c  contacts both the first contact member  168   a , and the second contact member  168   b.    
     For example, the stud mainspring  140   c  at a near-outer-end portion  140   ct  positions in a gap of approximately 0.04 millimeter between the first contact member  168   a  and the second contact member  168   b . Consequently, in a state that the swing angle of the balance with hairspring  140  is in a range exceeding 0 degree but less than 180 degrees, the near-outer-end portion  140   ct  of the stud mainspring  140   c  does not contact the first contact member  168   a  and does not contact the second contact member  168   b . That is, the stud mainspring  140   c  at its outer end is out of contact with the first contact member  168   a  and out of contact with the second contact member  168   b . Accordingly, the coils  180 ,  180   a ,  180   b ,  180   c  are not energized so that the magnetic flux on the balance magnet  140   e  will not have an effect on the coils  180 ,  180   a ,  180   b ,  180   c . As a result, the swing angle of the balance with hairspring  140  is free from attenuation due to operation of the balance magnet  140   e  and coils  180 ,  180   a ,  180   b ,  180   c.    
     Next, with reference to FIG. 5, FIG.  6  and FIG. 11, explanation will be made on the operation of the balance with hairspring  140  when the coils  180 ,  180   a ,  180   b ,  180   c  are energized, i.e. when the circuit is close. That is, FIG.  5  and FIG. 6 show aces that the balance with hairspring  140  has a swing angle 180 degrees or greater. 
     Note that in FIG. 6 the thickness of the stud mainspring  140   c  (thickness in the radial direction of the balance with hairspring) is exaggeratedly shown. 
     When the swing angle of the balance with hairspring  140  becomes 180 degrees or greater, the stud mainspring at the near-outer-end portion  140   ct  contacts the first contact member  168   a  or the second contact member  168   b . In such a state, the coils  180 ,  180   a ,  180   b ,  180   c  are energized and exerts such a force as suppressing rotational motion of the balance with hairspring  140  due to induction current caused by change of magnetic flux on the balance magnet  140   e . Due to this action, a brake force to the balance with hairspring  140  is applied suppressing the balance with hairspring  140  from rotating thereby decreasing the swing angle of the balance with hairspring  140 . 
     When the swing angle of the balance with hairspring  140  decreases down to a range of exceeding 0 degree but less than 180 degrees, the near-outer-end portion  140   ct  of the stud mainspring  140   c  becomes a state of out of contact with the first contact member  168   a  and out of contact with the second contact member  168   b . Accordingly, as shown in FIG.  3  and FIG. 4, because the outer end of the stud mainspring  140   c  is out of contact with the first contact member  168   a  and out of contact with the second contact member  168   b , the coils  180 ,  180   a ,  180   b ,  180   c  are not energized so that the magnetic flux on the balance magnet  140   e  des not have an effect on the coil  180 ,  180   a ,  180   b ,  180   c.    
     In the mechanical timepiece of the invention thus structured, the swing angle of the balance with hairspring  140  is to be controlled effectively. 
     The invention, as explained above, is structured having a balance rotation angle control mechanism in a mechanical timepiece structured including a balance with hairspring that an escape/speed control device repeats right and left rotation, an escape wheel and pinion rotating based on rotation of a front train wheel, and a pallet fork controlling rotation of the escape wheel and pinion based on operation of the balance with hairspring. Accordingly, it is possible to improve the accuracy for the mechanical timepiece without reducing a sustaining time of the mechanical timepiece. 
     That is, in the invention, an eye is placed on the relationship between instantaneous watch error and swing angle. By keeping the swing angle constant, the watch error is suppressed from changing thus providing adjustment to lessen advancement or delay per day of the timepiece. 
     Contrary to this, in the conventional mechanical timepiece, swing angle changes with lapse of time due to the relationship between sustaining time and swing angle. Furthermore, instantaneous watch error changes with lapse of time due to the relationship between swing angle and instantaneous watch error. Due to this, it has been difficult to increase the sustaining time for a timepiece over which constant accuracy is maintained. 
     Next, explanation will be made on a result of simulation concerning watch error conducted on the mechanical timepiece of the invention developed to solve the problem with the conventional mechanical timepiece. 
     Referring to FIG. 12, in the mechanical timepiece, adjustment is first made to a state the timepiece is advanced in instantaneous watch error as shown by x-marked plotting and thin line. In the mechanical timepiece, where the balance with hairspring  140  rotates a certain angle or greater, if the stud mainspring  140   c  at the outer end contacts the first contact member  168   a  or second contact member  168   b , the stud mainspring  140   c  is shortened in effective length further advancing the instantaneous watch error. 
     That is in the mechanical timepiece in a state the stud mainspring  140   c  at the outer end is out of contact with the first contact member  168   a  and out of contact with the second contact member  168   b , the instantaneous watch error in a full winding state is about 18 seconds per day (about 18 seconds fast per day). When 20 hour elapses from the full winding state, the instantaneous watch error becomes about 13 seconds per day (about 13 seconds fast per day). When 30 hours elapses from the full winding state, the instantaneous watch error becomes about −2 seconds per day (about 2 seconds slow per day). 
     In the mechanical timepiece of the invention, if assuming the balance rotation-angle control mechanism is not operated, in a state the stud mainspring  140   c  at the outer end is in contact with the first contact member  168   a  or in contact with the second contact member  168   b , the instantaneous watch error in a full winding state is about 25 seconds per day (about 25 seconds fast per day) as shown in triangle plotting and bold line. When 20 hour elapses from the full winding state, the instantaneous watch error becomes about 20 seconds per day (about 20 seconds fast per day). When 30 hours elapses from the full winding state, the instantaneous watch error becomes about 5 seconds per day (about 5 seconds fast per day). 
     Contrary to this, in the mechanical timepiece of the invention, when the balance rotation-angle control mechanism is operated, in a state the balance rotation-angle control mechanism is operative, i.e. before lapse of 27 hours from the full winding state of the mainspring the instantaneous watch error can maintain about 5 seconds per day (maintains a state of about 25 seconds fast per day) as shown in black-circle plotting and extreme bold line. When 30 hours elapses from the full winding state, the instantaneous watch error becomes about −2 seconds per day (about 2 seconds slow per day). 
     The mechanical timepiece having the balance rotation-angle control mechanism of the invention controls swing angle of the balance with hairspring to thereby suppress the timepiece instantaneous watch error from changing. Accordingly, it is possible to increase the lapse of time from the full winding state wherein the instantaneous watch error is about 0 to 5 seconds per day, as compared to the conventional mechanical timepiece shown by square plotting and virtual line in FIG.  12 . 
     That is, the mechanical timepiece of the invention has a sustaining time of about 32 hours for which the instantaneous watch error is within about plus/minus 5 seconds per day. This sustaining time value is about 1.45 times a sustaining time of about 22 hours for the conventional mechanical timepiece having an instantaneous watch error within about plus/minus 5 seconds per day. 
     Accordingly, a simulation result was obtained that the mechanical timepiece of the invention is well accurate as compared to the conventional mechanical timepiece. 
     Next, explanations will be made on the positions of the first contact member and second contact member relative to the near-outer-end portion  140  of the stud mainspring as well as a switch adjusting device used for adjusting a gap between the first contact member and the second contact member. 
     Referring to FIG.  15  and FIG. 16, a switch adjuster device  200  includes a switch body  202  and a first guide pin  204  and second guide pin  206  provided on the switch body  202 . The switch body  202  is formed of metal, such as iron or brass, or plastic. The first guide pin  204  and the second guide pin  206  are formed of metal, such as iron or brass, or plastic. The first guide pin  204  and the second guide pin  206  may be formed as separate members from the switch body  202  and fixed on the switch body  202 . Otherwise, the first guide pin  204  and the second guide pin  206  may be formed integral with the switch boy  202 . The switch body  202  is mounted on a balance with hairspring (not shown), for rotation about a rotation center of the balance with hairspring. 
     A switch-insulating member  210  is arranged on the switch body  202  on a side opposite to a side facing the balance with hairspring  140 . The switch-insulating member  210  is formed of an insulative material, such as plastic, and of an elastically deformable material. A first elongate hole  210   a is provided in the switch insulating member  210 . In this first elongate hole  210   a , the first guide pin  204  and the second guide pin  206  are received. The switch-insulating member  210  is slidably arranged relative to the switch member  202 . The switch-insulating member  210  has a slide direction that is coincident with a straight line passing a center of the second guide pin  206  and center of the balance with hairspring  140 . 
     A switch spacing-adjusting lever  212  is rotatably provided in the switch-insulating member  210  by a slip mechanism. The switch spacing adjusting lever  212  at its cylindrical-portion outer periphery is assembled in a circular portion provided in part of the first elongate hole  210   a of the switch insulating member  210 . Because the circular portion partly provided in the first elongate hole  210   a of the switch insulating member  210  is structured to be fit in the cylindrical portion of the switch spacing adjusting lever  212  through elastic force, the switch spacing adjusting lever  212  can fix rotation in an arbitrary position. 
     A first contact  212   a  and a second contact  212   b  are provided on the switch spacing-adjusting lever  212  on a side facing the balance with hairspring  140 . The first contact  212   a  and the second contact  212   b  are provided in positions eccentric relative to a rotation enter of the switch spacing-adjusting lever  212 . The first contact  212   a  and the second contact  212   b  are formed in axis-symmetry to a straight line including the rotation center of the switch spacing-adjusting lever  212 . 
     The near-outer-end portion  140   ct  of the stud mainspring  140   c  is positioned in a gap SSW between the first contact  212   a  and the second contact  212   b . For example, the gap is approximately 0.06 millimeter. 
     By rotating the switch spacing adjusting lever  212  in a direction of an arrow  220  (clockwise in FIG. 15) or a direction of an arrow  222  (counterclockwise in FIG.  15 ), the first contact  212   a  and second contact  212   b  can be rotated. This allows for changing the distance between the first contact  212   a  and the second contact  212   b  in a direction of a straight line passing the center of the balance with hairspring  140 . 
     Furthermore, a switch position-adjusting lever  232  is provided rotatable by a slip mechanism relative to the switch body  202 , and to be fixed in an arbitrary position. The switch position-adjusting lever  232  has an eccentric portion  232   a  to be fitted in a second elongate hole  210   b  of the switch-insulating member  210 . The second elongate hole  210   b  has a lengthwise center axis directed perpendicular to a direction of a straight line passing a center of the second guide pin  206  and center of the balance with hairspring  140 . That is, the direction of the lengthwise center axis of the second elongate hole  210   b  is perpendicular to a lengthwise center axis of the first elongate hole  210   a . Elastically deformable portions  210   c  and  210   d  of the switch insulating member  210  forming elastically deformable widths are provided at lengthwise opposite ends of the second elongate hole  210   b . A rigid portion  210   e  of the switch insulating member  210  forming an elastically non-deformable width is provided on an outer side of the second elongate hole  210   b  (on a side remote from the outer end of the stud mainspring  140   c ). Consequently, the width of the rigid portion  210   e  is formed greater than the width of the elastically deformable portion  210   c  and  210   d . The rigid portion  210   e  at its inner side is arranged in 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  240  (clockwise in FIG.  15 ), the eccentric portion  232   a  can be rotated. Due to this, the switch insulating member  210  is allowed to move in a direction toward the center of the balance with hairspring  140  (in a direction of an arrow  242  in FIG.  15  and FIG. 16) in a direction of a straight line passing the center of the balance with hairspring  140 . As a result, the first contact  212   a  moves toward the near-outer-end portion  140   ct  of the stud mainspring  140   c  while the second contact  212   b  moves away from the near-outer-end portion  140   ct  of the stud mainspring  140   c.    
     By rotating the switch position-adjusting lever  232  in a direction of an arrow  244  (counterclockwise in FIG.  15 ), the eccentric portion  232   a  can be rotated. Due to this, the switch-insulating member  210  is allowed to move in a direction away from the center of the balance with hairspring  140  (in a direction of an arrow  246  in FIG.  15  and FIG.  16 ). As a result, the first contact  212   a  moves away from the near-outer-end portion  140   ct  of the stud mainspring  140   c  while the second contact  212   b  moves toward the near-outer-end portion  140   ct  of the stud mainspring  140   c.    
     FIG.  17  and FIG. 18 illustrates a state that in FIG.  15  and FIG. 16 the switch position adjusting lever  232  is rotated in a direction of the arrow  240  (clockwise in FIG.  15 ). By rotation of the switch position-adjusting lever  232 , the eccentric portion  232   a  is rotated. The switch-insulating member  210  moves in a direction toward the center of the balance with hairspring  140 . The first contact  212   a  moves toward the near-outer-end portion  140   ct  of the stud mainspring  140   c , and the second contact  212   b  moves away from the near-outer-end portion  140   ct  of the stud mainspring  140   c . In such operation of rotating the switch position-adjusting lever  232 , there is no change in the gap SSW between the first contact  212   a  and the second contact  212   b.    
     FIG.  19  and FIG. 20 illustrates a state that in FIG.  15  and FIG. 16 the switch spacing adjusting lever  212  is rotated in a direction of the arrow  222  (counterclockwise in FIG.  15 ). By rotation of the switch spacing adjusting lever  212 , the first contact  212   a  and the second contact  212   b  are rotated to decrease a distance in a direction of a straight line passing the center of the balance with hairspring  140  between the first contact  212   a  and the second contact  212   b . Consequently, the distance in the direction of the straight line passing the center of the balance with hairspring  140  between the first contact  212   a  and the second contact  212   b  changes to SSW 2  smaller than SSW. 
     As explained above, in the mechanical timepiece of the invention, the use of the switch adjuster device  200  makes it possible to adjust the positions of the first contact  212   a  and second contact  212   b  relative to the near-outer-end portion  140   ct  of the stud mainspring. By adjusting the gap between the first contact  212   a  and the second contact  212   b , it is possible to adjust a distance between the near-outer-end portion  140   ct  and the first contact  212   a  as well as a distance between the near-outer-end portion  140   ct  and the second contact  212   b.    
     By applying the two adjuster mechanism as explained above to a switch adjuster device, it is easily adjust a swing angle that the switch turns ON/OFF. 
     Accordingly, in the mechanical timepiece of the invention shown in FIG.  1  and FIG. 2, where using a switch adjuster device  200 , a first contact  212   a  may be arranged in place of the first contact member  168   a  and a second contact  212   b  in place of the second contact member  168   b.    
     The switch adjuster device for a mechanical timepiece of the invention is applicable to a conventional regulator device for a mechanical timepiece. In such a case, the first contact  212   a  corresponds to a regulator and the second contact  212   b  to a stud rod. 
     With such structure, it is possible to adjust a regulator and stud rod for a mechanical timepiece with accuracy and efficiency. 
     Industrial Applicability 
     The mechanical timepiece of the present invention has a simple structure and is suited for realizing an extreme accurate mechanical timepiece. 
     Furthermore, the mechanical timepiece of the invention has a switch adjuster device which enables an accurate mechanical timepiece with efficiency greater than the conventional mechanical timepiece to be manufactured. 
     FIG. 8 
     MAINSPRING TORQUE CURVE 
     MAINSPRING TORQUE 
     LAPSE OF TIME IN WINDING FROM FULL WINDING HOUR 
     FIG. 9 
     MAINSPRING TORQUE—SWING ANGLE 
     MAINSPRING TORQUE 
     SWING ANGLE DEGREE 
     FIG. 10 
     TRANSITION OF INSTANTANEOUS WATCH ERROR DUE TO SWING ANGLE 
     INSTANTANEOUS WATCH ERROR SECOND/DAY 
     SWING ANGLE DEGREE 
     FIG. 11 
     IN OPENING OF CIRCUIT 
       168   a ,  168   b  CONTACT MEMBER 
       140   c  STUD MAINSPRING 
       140   b  BALANCE WHEEL  140   e  (MAGNET) 
     MAGNETIC FLUX 
       180  COIL 
       170   e  STUD SUPPORT 
     IN CLOSING OF CIRCUIT 
       168   a ,  168   b  CONTACT MEMBER 
       140   c  STUD MAINSPRING 
       140   b  BALANCE WHEEL  140   e  (MAGNET) 
     BRAKE FORCE 
       180  COIL 
     STUD SUPPORT 
     FIG. 12 
     TRANSITION OF INSTANTANEOUS WATCH ERROR BY LAPSE OF TIME 
     INSTANTANEOUS WATCH ERROR SECONDS/DAY 
     STUD MAINSPRING NON-CONTACT 
     STUD MAINSPRING CONTACT/NO BRAKE 
     MECHANICAL TIMEPIECE OF THE INVENTION 
     CONVENTIONAL MECHANICAL TIMEPIECE 
     LAPSE OF TIME FROM REWINDING FROM FULL WINDING HOUR