Control device for stepping motor, control method for the same, and timing device

Abstract: This invention provides a control device and a control method for a wristwatch or the like in which a stepping motor for hand movement and an electricity generating device are used together. The effects of magnetic fields from the electricity generating device can be mitigated, thereby providing a timing device which operates hand movement without error and at high precision. In particular, a detecting pulse (SP1) is output to both the driving pole side and the reverse pole side. Thus, detection time is extended so that even in the event that a magnetic field with polarity is output as noise from the electricity generating device, the detection sensitivity is improved to a point where the magnetic field can be detected. Then, rotation detecting of the driving rotor is omitted by means of outputting an auxiliary pulse (P2) with great effective electric power instead of the normal driving pulse (P1) in the event that a magnetic field is detected. This prevents mistaken detection which could lead to error in the movement of the hands.

Description: The present invention relates to a control device for a stepping motor and a control method thereof, and particularly relates to a control device and a control method for an electronic timepiece which captures kinetic energy using a rotating weight or the like and drives a rotating electricity generating device, and uses that electric power to drive a stepping motor. Stepping motors are also referred to as pulse motors, or digital motors, and are motors which are driven by pulse signals and used widespread as actuators for digital control devices. In recent years, compact electronic devices and information equipment have been developed which are suitable in portability, and compact and lightweight stepping motors are in widespread use as the actuators for such equipment. Most representative of such electronic devices are timing devices such as electronic timepieces, time switches, chronographs, and so forth. Fig. 12 shows an example of a timing device such as a wristwatch or the like which uses a stepping motor. This timing device 9 is comprised of: a stepping motor 10; a driving device 20 for driving the stepping motor 10; a gear train 50 for transferring the movement of the stepping motor 10; and a second hand 61, minute hand 62, and hour hand 63 which are carried by the gear train 50. The stepping motor 10 is comprised of: a driving coil 11 which generates magnetic force by means of driving pulses supplied from a control device 20; a stator 12 which is excited by the driving coil 11; and a rotor 13 which rotates within the stator 12 by means of the excited magnetic field. The rotor 13 comprises a disk-shaped bipolar permanent magnet, thus forming a PM-type (Permanent Magnet rotational) stepping motor. The stator 12 is provided with a magnetism saturating unit 17 so that the different magnetic poles due to the magnetic force generated by the driving coil 11 are generated at the respective phases (poles) 15 and 16 surrounding the rotor 13. Also, internal notching 18 is provided at appropriate locations on the inner periphery of the stator 12, so that cogging torque is generated and the rotor 13 is stopped at the appropriate position. The rotation of the rotor 13 of the stepping motor 10 is transferred via a pinion to each of the hands by the gear train 50 comprised of: a fifth gear 51; a fourth gear 52; a third gear 53; a centre wheel 54; a minute wheel 55; and a hour wheel 56. The second hand 61 is connected to the axis of the fourth gear 52. The minute hand 62 is connected to the axis of the centre wheel 54, and the hour hand 63 is connected to the axis of the hour wheel 56. The time is displayed by means of each of the hands operating synchronously with the rotation of the rotor 13. Of course, a transfer system for displaying the year, month, and day (not shown) may also be connected to the gear train 50. In order for this timing device 9 to display the time by means of rotation of the stepping motor 10, the stepping motor 10 is supplied with driving pulses which comprise counting (timing) of signals of a reference frequency. The control device 20 according to the present example for controlling the stepping motor 10 is comprised of: a pulse synthesising circuit 22 for generating reference pulses of a standard frequency using a reference oscillator 21 such as a crystal oscillator, or pulse signals of different pulse width or timing; and also a control circuit 23 for controlling the stepping motor 10 based on the various pulse signals supplied from the pulse synthesising circuit 22. Further, the control circuit 23 has a driving control circuit 24 for controlling a later-described driving circuit, and a detecting circuit 25 for performing detection of rotation and so forth. The driving control circuit 24 is comprised of: a driving pulse supplying unit 24a for supplying driving pulses to the driving coil 11 via the driving circuit for driving the driving rotor 13 of the stepping motor 10; a rotation detection pulse supplying unit 24b for outputting rotation detecting pulses which induce induction voltage for rotation detection of the driving rotor 13 following the driving pulse; a magnetic detection pulse supplying unit 24c for outputting magnetic field detecting pulses, which induce induction voltage for detection of an external magnetic field, to the stepping motor before the driving pulse; an auxiliary pulse supplying unit 24d for auxiliary pulses of effective electric power greater than the driving pulse in the event that the driving rotor 13 does not rotate or when an external magnetic field has been detected; and a demagnetising pulse supplying unit 24e for providing demagnetising pulses of which the polarity is different to that of the auxiliary pulses following the auxiliary pulse, in order to perform demagnetising following the auxiliary pulse. Also, the detecting circuit 25 is comprised of a rotation judging unit 26 for comparing the rotation detecting induction voltage obtained by the rotation detecting pulse with a set value so as to detect whether or not there is rotation, and a magnetic field judging unit 27 for comparing magnetic field detecting induction voltage obtained by the magnetic field detecting pulse a set value so as to detect whether or not there is presence of a magnetic field. As shown in Fig. 13, the rotation judging unit 26 compares the value of the bi-directional excitation voltage generated in the driving coil 11 with a set value SV1 in the two comparators 29a and 29b so as to confirm whether or not the driving rotor 13 has rotated. Also, the magnetic field judging unit 27 uses the two inverters 28a and 28b and employs the threshold value of the inverters as a set value SV2 so as to confirm whether or not there is presence of a magnetic field. The judgement results of each are fed back to the driving control circuit 24 via OR gates 28c and 29c, and used for controlling the stepping motor. On the other hand, the driving circuit 30 which supplies various driving pulses to the stepping motor 10 based on the control of the driving control circuit 24 has a bridge circuit (see fig. 12) which is comprised of a serially connected p-channel MOS 33a and n-channel MOS 32b, and p-channel MOS 33b and n-channel MOS 32a; these being arranged so as to control the voltage supplied to the stepping motor from the battery 41. Further provided are rotation detecting resistors 35a and 35b respectively connected in parallel fashion to the p-channel MOS 33a and 33b, and sampling p-channel MOS 34a and 34b for supplying chopper pulses to the resistors 35a and 35b. Accordingly, the respective gate electrodes of each of the MOS 32a, 32b, 33a, 33b, 34a, and 34b are applied with control pulses of differing polarity and pulse widths from each supplying unit 24a through 24e of the driving control circuit 24 according to the respective timings. This provides the supply of driving pulses differing in polarity to the driving coil 11, or the supply of detecting pulses for inducing induction voltage for detection of rotation of the rotor 13, and magnetic detection of the field thereof. Fig. 14 is a timing chart illustrating the control signals supplied to the gates GP1, GN1, and GS1 of the p-channel MOS 33a, n-channel MOS 32a, and sampling p-channel MOS 34a for excitation of a magnetic field of one polarity. Fig. 14 also illustrates the control signals supply and to the gates GP2, GN2, and GS2 of the p-channel MOS 33b, n-channel MOS 32b, and sampling p-channel MOS 34b for excitation of a magnetic field of the reverse polarity. This excitation of the magnetic field with respect to the driving coil 11 rotationally drives the stepping motor 10. The control device of this stepping motor 20 operates so as to carry the timepiece hands each second, by controlling the stepping motor 10 of the timing device 9, and a series of control signals are supplied to the driving circuit 30. At the beginning of each cycle, noise is generated when performing rotation detection, and pulses SP0 and SP1 are output for detecting whether or not there is presence of a magnetic field which could cause erroneous detection. The pulse SP0 which is output at the time t1 is a pulse for detecting a noise magnetic field due to high-frequency noise. The control signals for outputting this magnetic field detecting pulse SP0 are supplied from the magnetic field detecting pulse supplying unit 24c of the driving control circuit 24 to the gate GP1 of the p-channel MOS 33a on the driving side (driving pole side) from which the driving pulse P1 is output. This magnetic field detecting pulse SP0 is a continuous control pulse of around 20 ms in width. It is used to detect noise magnetic fields caused by switching and the like of household electrical appliances such as electric blankets or infra-red foot-warmer tables (popular in Japan). Subsequently, a control signal for outputting the magnetic field detecting pulse SP1 for detecting alternating current magnetic fields of 50 to 60 Hz is output at time t2 to gate GP2 of the p-channel MOS 33b on the side opposite to the driving pole side (reverse pole) from the same magnetic detection pulse supplying unit 24c. This magnetic field detecting pulse SP1 is an intermittent chopper pulse with a duty ratio of around 1/8, thus sampling the electric current induced in the driving coil by the alternating current magnetic field in the form of voltage. This enables judgement thereof in the magnetic field judging unit 27 of the detecting circuit 25. Also, taking into consideration the fact that the driving side, i.e., the p-channel MOS 33a and the n-channel MOS 32a, deteriorates in magnetic field detecting capabilities in the event that an auxiliary pulse of great effective electric power is applied; the control pulse SP1 is supplied to the gate P2 so as to drive the p-channel MOS 33b which is at the reverse pole as the driving side. Such magnetic field detection is disclosed in detail in Japanese Examined Patent Publication No. 3-45798. Following the control pulses for outputting the magnetic field detecting pulses SP0 and SP1; control pulses for outputting the driving pulse P1 at the time t3 are supplied from the driving pulse supplying unit 24a of the driving pulse control circuit 24 to the gate GN1 of the n-channel MOS 32a and the gate GP1 of the p-channel MOS 33a of the driving pole side. The effective electric power of the driving pulse 1 is reduced to around the limit of rotation of the driving rotor 13, and is arranged such that, e.g., a driving pulse P1 of W10 in pulse width is supplied at time t3. The control signal for outputting the driving pulse P1 is such as can change the pulse width of the driving pulse and control the effective electric power thereof. In the event that the rotor 13 does not rotate and the auxiliary pulse P2 is output, the pulse width is widened and the effective electric power is raised. On the other hand, the arrangement is such that in the event that the rotor 13 can be continuously driven a certain number of times by pulses of the same width, the effective electric power can be reduced by narrowing the pulse width. Following the driving pulse P1, a control pulse for outputting a pulse SP2 for rotation detection, which performs detection of driving rotation of the rotor 13, at time t4 from the rotation detection pulse supplying unit 24b of the driving control circuit 24 to the gate GP1 of the p-channel MOS 33a on the driving side and sampling p-channel MOS 34a. This rotation detecting pulse SP2 is a chopper pulse with a duty ratio of around 1/2, thus obtaining the induction electric current induced in the driving coil when the rotor 13 rotates, in the form of output voltage from the rotation detecting resister 35a. Then, the voltage from the rotation detecting resister 35a is compared with a set value SV1 within the rotation detecting unit 26 of the detecting circuit 25, thereby judging whether or not the rotor 13 has rotated. In the event that the induction voltage induced by the rotation detecting pulse SP2 does not attain the set value SV1, the rotor 13 is judged to have not moved. A control signal for outputting an auxiliary pulse P2 at time t5 is output from the auxiliary pulse supplying unit 24d of the driving control circuit 24 to the gate GP1 of the n-channel MOS 32a on the driving side and also to the gate GP1 of the p-channel MOS 33a. The auxiliary pulse P2 is a driving pulse with a pulse width of W20, which is a greater effective electric power than the driving pulse P1, which has energy sufficient for the rotor 13 to rotate without fail. This auxiliary pulse P2 is output instead of the driving pulse P1 in the event that rotation of the rotor 13 is not detected, and also in cases wherein a magnetic field has been detected by either of the magnetic field detecting pulses SP0 or SP1. In the event that a magnetic field which is noise is detected in the region of the stepping motor 10; there is the possibility that a magnetic field which is noise may be detected by the rotation detecting pulse SP2 even if the rotor 13 is not rotating. This can cause error in the movement of the hands. Accordingly, in the event that a magnetic field is detected, an unnecessary auxiliary pulse P2 is output for detecting rotation. This increases power consumption, but prevents error in the movement of the hands from occurring. In the event that the auxiliary pulse P2 is output, a control pulse for outputting a demagnetising pulse PE at time t6 is supplied to the gate GN2 of the n-channel MOS 32b, which is at the reverse pole from the demagnetising pulse supplying unit 24e of the driving control circuit 24. The control pulse is also supplied the gate GP2 of the p-channel MOS 33b. This demagnetising pulse PE is for reducing the residual magnetic flux of the driving coil 11 which has been generated by the auxiliary pulse P2. It is realised by means of supplying a pulse which is of reverse polarity to the auxiliary pulse P2. Supplying the demagnetising pulse PE completes one cycle of rotational driving of the stepping motor 10 by one step angle. The next cycle for performing another cycle of rotational driving of the stepping motor 10 by one step angle is started at time t11, which is following the lapse of one second from time t1. In this cycle, the MOS 32b, 33b, and 34b which were on the reverse side in the previous cycle become the driving pole side. As with the previous cycle; first, a pulse SP0 is output at time t11 for detecting magnetic flux noise due to high-frequency noise. Next, a pulse SP1 is output at time t12 for detecting noise due to low-frequency alternating current magnetic field. In the event that magnetic noise is not detected, the driving pulse P1 is output at time t13. Since an auxiliary pulse P2 has been output in the previous cycle, the effective electric power of the driving pulse P1 is increased. That is, a driving pulse P1 of a width W11 which is wider than that of the driving pulse of the previous cycle is output at time t13. Further, a rotation detecting pulse SP2 is output at time t14, and in the event that rotation of the rotor 13 is detected thereby, the cycle ends at this step. Fig. 15 shows the above-described operation of the control device 20 in a flowchart. First, in step ST1, a timing reference pulse is counted and one second is measured. When the one second elapses, in step ST2, high-frequency magnetic field is detected using the magnetic field detecting pulse SP0. In the event that a high-frequency magnetic field is detected; an auxiliary pulse P2 with a great effective electric power is output in step ST7 instead of the driving pulse P1. This prevents error in the movement of the hands from occurring due to mistaken detection. In the event that a high-frequency magnetic field is not detected, the presence of alternating current magnetic field which is low-frequency magnetic field may be detected in step ST3, using the magnetic field detecting pulse SP1. In the event that there is present an alternating current magnetic field; an auxiliary pulse P2 is output in step ST7 as with the above case, thus preventing prevents error in the movement of the hands from occurring. In the event that there is no detection of magnetic field in these steps, a driving pulse P1 is output in step ST4. Subsequently, a rotation detecting pulse SP2 is output in step ST5 to confirm whether or not there is rotation of the rotor 13. In the event that rotation is not confirmed, an auxiliary pulse P2 with a great effective electric power is output in step ST7 which rotates the rotor 13 without fail. Once the auxiliary pulse P2 is output, a demagnetising pulse PE is output in step ST 8. Further, in step ST10, adjustment of the level of the driving pulse P1 (first level adjustment) after the auxiliary pulse has been output is performed. In the event that there is defective rotation in step ST5, supplying a driving pulse P1 of the same effective electric power only means that the defective rotation will be repeated. Accordingly, the cause of output of the auxiliary pulse P2 is determined in step ST11, and setting is made in step ST12 so that output of the driving pulse P1 with a higher level of voltage can be made. The system then returns to step ST1 and performs timing operation. On the other hand, in step ST5, in the event that rotation of the rotor 13 by means of the driving pulse P1 has been discerned; level adjustment to lower the effective electric power of the driving pulse P1 (second level adjustment) is conducted in step ST6. In many cases, confirmation is made that the rotor 13 has rotated a plurality of times by a driving pulse P1 of the same effective electric power, and the effective electric power of the driving pulse is reduced. By means of performing such control, the power consumption of the pulse P1 can be reduced. At the same time, error in the movement of the hands can be prevented from occurring in areas where there are magnetic fields from electric and electronic appliances. Thus, a timing device with high reliability and low power consumption can be realised. In recent years, timing devices are being sold which serve as wristwatches or the like with electricity generators built in which the movement of the arm of the user or the like is captured and the generated electricity drives the stepping motor for movement of the hands of the watch. Such timing devices can be used without batteries, so there is no troublesome procedure of changing batteries. The timing device can continue to run whenever and wherever using energy such as the motion of the user's arm or natural energy surrounding the user. Further, there is no problem of pollution accompanying disposal of batteries. Thus, this is an art which is being closely monitored for future widespread use in wristwatches and the like. EPP 0679969A describes an analogue indication type electronic timepiece which can use kinetic energy produced by the user to generate electricity. However, with electricity generating devices which capture movement of the user to perform generation of electricity, a configuration is used which is almost the same as that of the stepping motor. That is, a generating rotor is rotated by means of energy transferring means such as a rotating weight, or the like, thus changing kinetic energy into electrical energy. Accordingly, the magnetic flux generated from this generator also becomes noise at the time of performing rotation detecting of the driving rotor of the stepping motor. This lowers the reliability of the timing device. The noise from the generator is of a frequency of 200 to 300 Hz. This frequency is not easily detected by the conventional magnetic field detecting pulse SP0 for detecting high frequency noise or the magnetic field detecting pulse SP1 for detecting alternating magnetic flux of 50 to 60 Hz. Further, the generator is not continuously generating. That is, generation of electricity is performed only when the rotating weight rotates due to the user's arm movement or so forth. Accordingly, the generation of the magnetic field which is noise is irregular, and further, often is as short as 100 ms. Hence, there is a great possibility that noise may be generated at the time that the rotation detecting pulse SP2 is output, even if there is no detection of magnetic flux by pulse SP0 or pulse SP1. Also, a half-wave rectification circuit which is easily reduced in size and is low in cost is generally used, so there is directionality in the magnetic noise. There is no guarantee with the above-described conventional detection method that an induction voltage due to magnetic noise which causes mistaken detection at the time of rotation is detected. Further, there is a problem that in the event that the magnetic noise is detected and the auxiliary pulse P2 is output, magnetic detection capabilities in the same direction deteriorate due to the effects of residual magnetism. In this way, in order to provide a highly reliable timing device, it is an urgent matter that control devices for stepping motors built in to timing devices along with alternating current electricity generating devices using magnetic fields be improved; such that the effects of external magnetic fields be done away with and also that the effects of the magnetic field generated by the generating device be inhibited. Accordingly, it is an object of the present invention to provide a control device and a control method for an arrangement in which a control device of a stepping motor is in proximity to an alternating current electricity generating device; whereby the effects of external magnetic fields and the effects of the magnetic field generated by the generating device are prevented, and control can be performed with high reliability and no errors in hand movement. It is another object of the present invention to realise a highly precise timing device having an electricity generating device therein and, further, to provide a highly reliable timing device which can be used with no worries of discarding batteries. In a first aspect of the present invention there is provided a control device for a stepping motor wherein a driving rotor is rotatably driven by driving pulses via a. driving coil, said stepping motor being subjected to an alternating magnetic field by electric power generated by an electricity generating device driven by kinetic energy transferring means; said control device comprising: driving means for supplying at least one driving pulse to said driving coil for driving said stepping motor, and characterised by: means for reducing the effects of magnetic fields external to said stepping motor upon the operation of said stepping motor. In a second aspect of the present invention there is provided a control method for a stepping motor wherein a driving rotor is rotatably driven by driving pulses via a driving coil, said stepping motor being subjected to an alternating magnetic field by electric power generated by an electricity generating device driven by kinetic energy transferring means; said control method comprising: a driving step for supplying at least one driving pulse to said driving coil for driving said stepping motor, and characterised by: a step for reducing the effects of magnetic fields external to said stepping motor upon the operation of said stepping motor. Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:- Fig. 1 is a diagram illustrating a schematic construction of a timing device, having a stepping motor and electricity generating device, to which the present invention relates. Fig. 2 is a diagram illustrating the schematic construction within the detecting circuit in the control circuit of the timing device shown in Fig. 1. Fig. 3 is a diagram illustrating increase in the charging voltage by means of operation of the electricity generating device, in the timing device shown in Fig. 1. Fig. 4 is a flowchart illustrating the control method of the control device relating to a first embodiment of the present invention. Fig. 5 is a timing chart illustrating the operation of the control device shown in Fig. 4. Fig. 6 is a flowchart illustrating the control method of the control device relating to a second embodiment of the present invention. Fig. 7 is a timing chart illustrating the operation of the control device shown in Fig. 6. Fig. 8 is a flowchart illustrating the control method of the control device relating to a third embodiment of the present invention. Fig. 9 is a timing chart illustrating the operation of the control device shown in Fig. 8. Fig. 10 is a flowchart illustrating the control method of the control device relating to a fourth embodiment of the present invention. Fig. 11 is a timing chart illustrating the operation of the control device shown in Fig. 10. Fig. 12 is a diagram illustrating the schematic construction of a conventional timing device. Fig. 13 is a diagram illustrating the schematic construction of the detecting circuit employed in the timing device shown in Fig. 12. Fig. 14 is a timing chart illustrating the operation of the control device employed in the timing device shown in Fig. 12. Fig. 15 is a flowchart illustrating the control method of the control device illustrated in Fig. 14. In order to inhibit effects of the magnetic field of the electricity generating device as much as possible; the present invention is arranged such that detection of the alternating current magnetic field can be made not only by the reverse pole side to the driving pole side, but also can be made by the driving pole side. This increases detection sensitivity of the magnetic field. That is, the present invention preferably consists of a control device for a stepping motor wherein a driving rotor is rotatably drivable within a driving stator having a driving coil, the driving rotor being subjected to multipolar magnetisation by electric power, the electric power being generated by an electricity generating device driven by kinetic energy transferring means; the control device comprising: driving means for supplying at least one driving pulse to the driving coil for driving the driving rotor; rotation detecting means for supplying at least one rotation detection pulse for induction of a rotation detection induction voltage for detection of rotation of the driving rotor, the rotation detection pulse being supplied following the driving pulse; magnetic field detecting means for supplying at least one magnetic field detection pulse for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, the magnetic field detection pulse being supplied prior to the driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values, thus judging whether or not there is roatation and whether or not an external magnetic field is present; and auxiliary means for supplying an auxiliary pulse of effective electric power greater than the driving pulse in the event that the driving rotor does not rotate or when an external magnetic field has been detected; wherein the magnetic field detecting means is capable of supplying first and second magnetic field detecting pulses of differing polarity to the driving coil prior to the driving pulse, in order to detect magnetic fields of approximately the same frequency band. The present invention also preferably consists of a control method for a stepping motor wherein a driving rotor is rotatably drivable within a driving stator having a driving coil, the driving rotor being subjected to multipolar magnetisation by electric power, the electric power being generated by an electricity generating device driven by kinetic energy transferring means; the control method comprising: a driving step for supplying at least one driving pulse to the driving coil for driving the driving rotor; a rotation detecting step for outputting to the driving coil at least one rotation detection pulse following the driving pulse, and comparing the induction voltage thereof with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to the driving coil at least one magnetic field detection pulse for detection of an external magnetic field, the magnetic field detection pulse being output prior to the driving pulse, and comparing the induction voltage thereof with a second set value, thereby detecting the presence of an external magnetic field; and an auxiliary step for supplying an auxiliary pulse of effective electric power greater than the driving pulse in the event that the driving rotor does not rotate or when an external magnetic field has been detected; wherein the magnetic field detecting step outputs to the driving coil magnetic field detecting pulses of differing polarity in order to detect magnetic fields of approximately the same frequency band. Thus, by means of detecting alternating current magnetic flux on the side of the reverse pole to the driving pole side and also detecting alternating current magnetic flux on the driving pole side, even in cases where there is a magnetic field being output from the generator which would mainly effect the driving side and which is effecting the driving coil, there is a greater possibility that such a magnetic field can be detected. Particularly, there is the danger that a magnetic field which would effect the driving side might be detected at the time of rotation and lead to error in the movement of the hands. Accordingly, detecting magnetic fields which would affect the driving side greatly inhibits decrease of reliability of the stepping motor due to external magnetic fields. Conventionally, detection of alternating current magnetic fields on the driving side is not performed, giving thought to deterioration of sensitivity due to the residual magnetic field from the auxiliary pulse. However, the probability of detecting magnetic fields is improved in the present invention by performing detection of alternating current magnetic fields on the driving side as well; since magnetic fields can be detected at both poles and also the detection time is doubled. Accordingly, the advantages in improving the reliability of timing devices are immense regarding an arrangement in which an electricity generating device is used in proximity to a control device of a stepping motor, since the presence or absence of effects of a magnetic field of the electricity generating device can be detected with high sensitivity. Also, taking into consideration the fact that the generation of the magnetic field which is noise is irregular, and further is often as short as 100 ms, there is no way to know at what timing the magnetic field will be generated during the course of supplying magnetic field detection pulses, driving pulses, rotation detecting pulses, etc. Accordingly, it is also effective to supply magnetic field detecting pulses immediately after the rotation detecting pulse, to confirm the detection precision by means of rotation detecting pulses. That is, a control device for a stepping motor which has magnetic field detecting means supplying a magnetic field detecting pulse to the driving coil before the driving pulse and immediately following the rotation detecting pulse is effective in increasing reliability. Regarding the control method of the stepping motor, there is included a first magnetic field detecting step for outputting to the driving coil magnetic field detection pulses for detection of magnetic field external to the stepping motor. The magnetic field detection pulse is output prior to the driving pulse. The induction voltage thereof is compared with a second set value, thereby detecting the presence of a magnetic field. Additionally, there is also added a second magnetic field detecting step for outputting to the driving coil magnetic field detection pulses for detection of magnetic fields external to the stepping motor. The magnetic field detection pulse is output following the rotation detecting pulse, and the induction voltage thereof is compared with a second set value, thereby detecting the presence of a magnetic field. Electric power from the electricity generating device is supplied to the control device of the stepping motor via charging means. Thus, the voltage of the driving pulses and so forth supplied to the stepping motor changes according to the charging voltage of the charging means. Generally, there is a tendency for magnetic field detection capabilities to deteriorate in the event that the charging voltage rises, since the S/N ratio increases due to the voltage of the driving pulses and so forth rising. Thus, in the control device for a stepping motor according to the present invention, the set value for judging the induction voltage for detecting magnetic fields in the aforementioned judging means is made to be adjustable according to the charging voltage. For example, the probability of detection of magnetic fields is increased by means of lowering the set value whenever the charging voltage rises so that the sensitivity for detecting magnetic fields does not deteriorate. Also, in the control method, the probability of detection of magnetic fields can be increased by means of enabling adjustment of the second set value according to the charging voltage, in the above-described magnetic field detecting step. Instead of detecting the magnetic field of the electricity generating device, an arrangement is provided wherein the fact that the electricity generating device is generating electricity is detected. Control is then performed assuming that there is a magnetic field which affects rotation detection. That is, in the control device, it is also effective to supply auxiliary pulses by means of the aforementioned auxiliary means while the electricity generating device is generating electricity, regardless of whether a magnetic field is detected or not. Also, in the control method, it is also effective to supply auxiliary pulses in the aforementioned auxiliary step while the electricity generating device is generating electricity, regardless of whether a magnetic field is detected or not. Also, although it is known that magnetic field detection capabilities deteriorate in the event that an auxiliary pulse with a great effective electric power is supplied; there is no need to detect whether or not there is a magnetic field following the auxiliary pulse, by means of selecting the auxiliary pulse according to whether or not generating is being performed or not. Accordingly, the reliability of control of the stepping motor can be further improved. In the event that the device has short-pulse supplying means for supplying to the driving coil short-pulses which are shorter in cycle than the drive pulse, such as fast-forward pulses or reverse pulses; it is preferable that the short-pulse supplying means stops supplying the short-pulse when the generating device is generating electricity, in order to prevent error in the movement of the hands. In the same way, there may be effects of voltage fluctuation regarding pulses which drive the driving rotor in the reverse direction (reverse pulses) since such pulses are combinations of a plurality of short pulses, not to mention fast-forward pulses which are short in cycle. Accordingly, it is preferable that reverse driving during generating be forcibly terminated, as well. Also, in the event that the device has a short-pulse supplying step for supplying to the driving coil short-pulses which are shorter in cycle than the drive pulse, called fast-forward pulses or reverse pulses; it is preferable that the short-pulse supplying means stops supplying the short-pulse when the generating device is generating electricity. Further, in the event that a magnetic field is detected, or in the event that the generating device is generating electricity and auxiliary pulses have been output, there is a high possibility that there may be a residual magnetic field remaining. Accordingly, providing pulses with great effective electric power as driving pulses for a certain number of times following the auxiliary pulse does away with the need to detect whether or not there is rotation, and error in the movement of the hands can be prevented. In the event that the driving means can supply a plurality of effective electric power driving pulses, at least one driving pulse with greater effective electric power than the immediately preceding driving pulse can be supplied following the auxiliary pulse being supplied. The effective electric power can be adjusted by means of supplying driving pulses of differing pulse widths or driving pulses of differing voltages. Or, in the event that the device is provided with demagnetising means which supplies demagnetising pulses of differing polarity to the auxiliary pulse for demagnetising purposes following the auxiliary pulse; supplying the demagnetising pulse following the auxiliary pulse and immediately before the next driving pulse enables a substantial increase in the voltage of the driving pulse. On the other hand, regarding the control method, it is effective to have a second driving step for supplying at least one driving pulse which is of greater effective electric power than the immediately preceding driving pulse, following the auxiliary pulse being supplied. Also, in the event that the device has a demagnetising step for providing demagnetising pulses, of which the polarity is different to that of the auxiliary pulses, following the auxiliary pulse in order to perform demagnetising following said auxiliary pulses; it is effective that the demagnetising step provide the demagnetising pulse immediately prior to the driving pulse which follows the auxiliary pulse. As described above, a control device and a control method for a stepping motor are provided which are not easily affected by the magnetic field from the electricity generating device housed within the same device. This is achieved by means of improving the probability of detection of the magnetic field, and by means of judging whether or not a magnetic field is present according to whether or not the electricity generating device is generating electricity or not, instead of detecting the magnetic field. It is further achieved by means of supplying a driving pulse with great effective electric power following the auxiliary pulse. Thus, employing the control device or the control method according to the present invention results in a stepping motor which performs movement of the hands in a stable manner and with high reliability. Accordingly, a timing device comprising: the control device of the stepping motor according to the present invention; a stepping motor which moves the hands on the face of the timepiece using driving pulses; pulse synthesising means which outputs pulse signals of a plurality of frequencies; and an electricity generating device capable of supplying electrical power to these components as described above; is highly precise which can be used anytime and anywhere without the need for batteries. The control method for a stepping motor according to the present invention can be provided in the form of a computer-readable medium such as a control program of a logic circuit or a microprocessor. Thus, is not restricted to timing devices. It can be applied to motor devices which require intermittent and highly precise hand movement. Description of the Preferred Embodiments First Embodiment The present invention will be described in further detail below, with reference to the drawings. Fig. 1 illustrates a schematic construction of a timing device 1 relating to a first embodiment of the present invention. In the timing device 1, the stepping motor 10 is driven by a control device 20, and the movement of the stepping motor 10 is transferred via a gear train 50 to a second hand 61, minute hand 62, and hour hand 63. The main construction of the stepping motor 10, gear train 50, and control device 20 are the same as those described with reference to Fig. 12. Thus, the items which are in common will be denoted with the same reference numerals and detailed description thereof will be omitted below. The timing device 1 according to the present embodiment is provided with an electricity generating device 40 which supplies driving power under the control of the control device 20, for driving the stepping motor 10. The electricity generating device 40 is formed of an alternating current electricity generating device of an electromagnetic induction type. A generating rotor 43 rotates within a generating stator 42 and electricity is induced in a generating coil. The timing device 1 uses a rotating weight 45 as means for transferring kinetic energy to the generating rotor 43. The movement of this rotating weight 45 is transferred to the generating rotor 43 via a speed-increasing gear 46. In the timing device 1 which is in the form of a wristwatch, the rotating weight 45 is capable of capturing movement such as the movement of the arm of the user and rotating within the device, thus performing the generation of electricity using natural energy relating to the lifestyle of the user. The power output from the electricity generating device 40 is subjected to half-wave rectification by means of a diode 47, and is temporarily stored in a large capacity condenser 48 which serves as condenser means. The driving voltage is supplied from the large capacity condenser 48 to the driving circuit 30 of the control device 20 via a booster/reducer circuit 49, for driving the stepping motor 10. The booster/reducer circuit 49 according to the present embodiment uses a plurality of condensers 49a, 49b, and 49c, so that multi-step boosting and reduction can be performed. The voltage supplied to the driving circuit 30 from the driving control circuit 24 of the control device 20 can be adjusted by means of control signals 11. The output voltage of the booster/reducer circuit 49 is also supplied to the driving control circuit 24 in the form of a monitoring signal 12. This allows for monitoring of output voltage, and also allows for judgement on the side of the driving control circuit 24 whether or not the electricity generating device 40 is generating electricity, by means of minute increase or decrease in the output voltage. The control circuit 23 used in the control device 20 has a driving control circuit 24 and a detecting circuit 25. This driving control circuit 24 is comprised of: a driving pulse supplying unit 24a, which supplies driving pulses P1 to the driving coil 11 via the driving circuit 30; a rotation detecting pulse supplying unit 24b, which supplies rotation detecting pulses SP2 following the driving pulses; a magnetic field detecting pulse supplying unit 24c, which supplies magnetic field detecting pulses SP0 and SP1 for detecting magnetic field before the driving pulse; an auxiliary pulse supplying unit 24d, which supplies auxiliary pulses P2 of greater effective electric power than that of the driving pulses; and a demagnetising pulse supplying unit 24e for supplying demagnetising pulses PE following the auxiliary pulses. Regarding the driving pulse supplying unit 24a according to the present embodiment, controlling the booster/reducer circuit 49 enables the effective electric power of the driving pulse P1 to be adjusted. Accordingly, the effective electric power of the driving pulse P1 can be adjusted by the pulse width and the voltage. Fine control of the driving voltage thus becomes possible, thereby supplying driving pulses of voltage optimal for rotating the driving rotor 13 and realising conservation of electricity. Further, with the present embodiment, the driving pulse supplying unit 24a also serves as short-pulse supplying means for supplying fast-forward pulses and reverse pulses. It can thus supply such short-cycle driving pulses. The driving pulse for fast-forward (fast-forward pulse) must be output in short intervals before the driving rotor 13 comes to a stop. There is no timing for confirming whether or not there is rotation. Accordingly, there is a need to supply driving pulses of stable voltage. However, the voltage which is supplied to the driving circuit 30 during charging does not easily stabilise, easily causing error in the movement of the hands. Thus, in the present invention, there is a high possibility that there is electricity being generated in the event that an external magnetic field is detected. The fast-forward is therefore forcibly terminated, and the movement of the hands is resumed at a normal speed. Also, it is possible to directly find out whether or not the electricity generating device is generating electricity by means of the monitoring signal 12. The fast-forward can be terminated according to these judgement results. The driving pulse supplying unit 24a can also serve as driving pulses supplied to drive the rotor 13 in a reverse direction (reverse pulses). These pulses are also short pulses, since two or three of the reverse pulses need to be output in order to drive one step angle. Accordingly, the reverse pulse also needs stable voltage, as with the case of the fast-forward pulse. Hence, it is desirable that the arrangement be such that the reverse pulses can also be terminated during generating of electricity. The magnetic field detecting pulse supplying unit 24c according to the present embodiment is arranged to output pulses SP1 for detecting low-frequency alternating current magnetic fields from the pole side opposite to the driving side, as with conventional arrangements. It is also capable of outputting pulses SP1 for detecting the same frequency band magnetic fields from the driving side, as well, thereby greatly increasing the probability of detecting magnetic fields. The electricity generating device 40 stored within the timing device 1 according to the present embodiment generates electricity by means of movement of a rotating weight 45 rotating a generating rotor 43. The timing of generating electricity is thus intermittent, and the time that generating is continued is short, i.e., 100 ms. Accordingly, in the event that the magnetic field detecting pulse SP1 is output on the reverse side alone, as with conventional art, even if there is no magnetic field detected at that time, there is the possibility that generation of electricity may be performed during the outputting of the rotation detecting pulse P2. Detection errors thus occur due to the magnetic field of the electricity generating device 40. Further, with the timing device 1 of the present embodiment, the electric power from the electricity generating device 40 is subjected to half-wave rectification by means of the diode 47. There is thus the possibility that the alternating current magnetic field may not be detected on the reverse pole side, depending on the direction of rectification. On the other hand, the magnetic field detecting pulse supplying unit 24c extends the interval of detection of the magnetic field by means of outputting the alternating current magnetic field detecting pulses SP1 from both the driving pole side and the reverse pole side. It further allows detecting of the magnetic field caught on the driving side, which is greatly affected regarding rotation detecting. Accordingly, the probability of detecting the magnetic field increases greatly, and the error in movement of hands by mistaken detection at the time of rotation detection is prevented. There is little chance that alternating current magnetic field can be detected on the driving side, since there is residual magnetic field remaining from the auxiliary pulse P2 and so forth. This is the reason that this has not been performed conventionally. In regard to this, according to the present invention, the detecting probability may be reduced somewhat. That is, it is possible to detect magnetic fields which directly effect operation at the time of rotation detection by means of detecting the magnetic field with both sides. Also, the amount of time spent on detecting magnetic fields can be extended, thus greatly increasing the ability to detect magnetic fields. Accordingly, there is increased probability of detecting the magnetic field of the electricity generating device 40 which is of higher frequency than the conventional 50 to 60 Hz alternating current magnetic field, and which is also intermittent and thus difficult to detect. Thus, mistaken detection of rotation of the rotor can be prevented. In the timing device 1 according to the present embodiment, a setting unit 27b for controlling the set value SV2 used for judging is provided to the magnetic field judging unit 27 which judges the voltage inducted by the driving coil 11 by means of the magnetic field detecting pulses SP0 and SP1. This even further increases the sensitivity of detection of magnetic fields. As shown in Fig. 2, the judging unit 27a of the magnetic field judging unit 27 uses comparators 28d and 28e respectively for judging the voltage generated in the driving coil 11 in each direction. The set value SV2 to be compared in these comparators 28d and 28e can be controlled by a controlling circuit 28f which uses a variable resistor. As shown in Fig. 3, when the electricity generating device 40 operates and electric power is stored in the large-capacity condenser 48 serving as condenser means, the charging voltage Vc increases with the passage of time. Thus, the S/N ratio between the control signal and the noise increases, so the noise level Ln from the magnetic field or the like relatively decreases. Accordingly, there is a tendency for the detecting sensitivity of magnetic fields from the electricity generating device and the like which affect the stepping motor to decrease as the charging voltage Vc increases. However, the intensity of the magnetic field itself does not decrease. Accordingly, even if the magnetic field is not detected, there is a great chance that mistaken signal due to the magnetic field may be obtained from the rotation detection pulses. Accordingly, in the timing device 1 according to the present embodiment, a setting unit 27b is provided in the magnetic field judging unit 27, so as to set the setting value SV2 low when the charging voltage Vc increases; so as to maintain the magnetic field detecting sensitivity at a high level. Adjustment of the setting value SV2 accompanying rising of the charging voltage Vc can be made from the output voltage of the booster/reducer circuit 49, so the control signal f13 is supplied from the driving control circuit 24 to the setting unit 27b. With the present embodiment, the auxiliary pulse supplying unit 24d of the driving control circuit 24 is arranged to supply an auxiliary pulse P2 of a great effective electric power in the event that the driving rotor 13 is judged not to be rotating by the rotation judging unit 26 of the detection circuit 25. This is in the event that a magnetic field is detected by the magnetic field judging unit 27 and is the same as the conventional circuit described above. However, in the above-described timing device 1 according to the present embodiment, there is a greater probability that there will be detection of magnetic field in the magnetic field detecting unit 27. Thus, it is possible to effectively output auxiliary pulses P2 without requiring judgement of rotation. Further, the effect of the magnetic field of the electricity generating device 40 can be inhibited, as well as the effect of other external magnetic fields, thus enabling movement of the hands with very high reliability. Also, regarding the auxiliary pause supplying unit 24d according to the present embodiment, the arrangement is such that the following pulses are supplied: auxiliary pulses supplied when the driving rotor 13 does not rotate with the driving pulse P1; auxiliary pulses supplied when a high-frequency magnetic field has been detected by means of the magnetic field detecting pulse SP0; and auxiliary pulses P2 of the same effective electric power as the auxiliary pulses supplied when a low-frequency magnetic field has been detected by means of the magnetic field detecting pulse SP1. However, it is possible to have an arrangement wherein auxiliary pulses of differing effective electric powers are supplied for each case. Also, according to the present embodiment, the demagnetising pulse supplying unit 24e which controls the demagnetising pulses PE output following the auxiliary pulse P2 is arranged for the demagnetising pulse PE to be output at a slower timing than conventional. That is, immediately before the next driving pulse P1, thus raising the actual effective electric power of the next driving pulse P1 so that sufficient energy for rotating the rotor 13 is provided. Accordingly, the rotor 13 can be rotated in a sure manner without increasing the energy of the driving pulse P1. Errors in the movement of hands can thus be prevented while reducing the amount of power consumption in the presence of magnetic fields from the electricity generating device or external magnetic fields. The detection capabilities of magnetic fields decrease immediately following output of the auxiliary pulse P2. The rotor is rotated in a sure manner by means of supplying the driving pulse P1 with a substantially high effective electric power. There is no need to detect whether or not the rotor has rotated, thus omitting detection of the magnetic fields which easily becomes erroneous. Fig. 4 illustrates a schematic flowchart of the control method of the stepping motor employed in the timing device 1 according to the present embodiment. In this flowchart, the steps approximately corresponding with the aforementioned control method described with reference to Fig. 15 are denoted by the same reference numerals, and detailed description thereof will be omitted. First, in step ST1, one second is measured for movement of the hands. With the control device 20 according to the present embodiment, when one second elapses, judgement is made whether or not an auxiliary pulse P2 is output at the previous cycle in step ST21. As described above, in the event that the auxiliary pulse P2 has been output in the previous cycle, a demagnetising pulse PE of the same polarity is output immediately before the driving pulse P1. Thus, in the event that judgement is made that the auxiliary pulse P2 has been output in the previous cycle in step ST21, the system moves to step ST25 and outputs the demagnetising pulse PE. Immediately afterwards the system outputs the driving pulse P1 in step 26, and returns to step ST1. Accordingly, in the cycle following output of the auxiliary pulse P2, the electric power of the demagnetising pulse PE is used to increase the substantial effective electric power of the driving pulse P1. In the event that the auxiliary pulse P2 has not been output in the previous cycle, in step ST2, high-frequency magnetic field is detected using the magnetic field detecting pulse SP0, as with the conventional example. In this case, as described above, the present embodiment is arranged such that the magnetic field judging unit 27 is capable of changing the setting value SV2 according to the charging voltage. Thus, the detection sensitivity for magnetic fields is maintained at a high level even if the charging voltage rises. In the event that it has been judged that a high-frequency magnetic field has been detected, there is the possibility that electricity may be being generated within the electricity generating device 40. In the present embodiment, in the event that short pulses such as fast-forward pulses or reverse pulses are being supplied in step ST15, the job is forcibly terminated. Further, in step ST7, an auxiliary pulse P2 which is of great effective electric power is output instead of the driving pulse P1. This prevents error in the movement of the hands due to mistaken detection due to the magnetic field. In the event that no high-frequency magnetic field is detected, in steps ST23 and 24, two magnetic field detecting pulses SP1 are alternately output to the driving pole side and the reverse pole side. This confirms whether or not there is presence of an alternating current magnetic field which is a low-frequency magnetic field. Since the set value SV2 for comparison of the induction voltage due to the magnetic field is made to be variable in the steps ST 23 and 24, high detection capabilities can be maintained even in the event that the charging voltage changes due to the presence or absence of generating of electricity. In the event that an alternating current magnetic field is detected, there is the possibility that the electricity generating device 40 may be operating and electricity is being generated. This means that the voltage may not be stable, so supplying of short pulses is forcibly terminated in step ST15 as described above. Further, an auxiliary pulse P2 is output in step ST7 instead of the driving pulse P1, thus preventing error in the movement of the hands. In the event that there is no detection of a magnetic field in these steps, the driving pulse P1 is output in step ST4. Then in step ST5, the rotation detecting pulse SP2 is output and rotation of the rotor 13 is checked. In the event that no rotation can be confirmed, an auxiliary pulse P2 with a great effective electric power is output in step ST7, rotating the rotor 13 without fail. In the conventional control method, once the auxiliary pulse P2 is output, a demagnetising pulse PE is output. In the control device 20 according to the present embodiment, the arrangement is such that the demagnetising pulse PE is output in the step ST25 immediately before the driving pulse P1 of the next cycle, as described above. Thus, the process of outputting the demagnetising pulse PE is omitted. Then, in the event that the auxiliary pulse P1 has been output by means of defective rotation, level adjustment of the driving pulse P1 (first level adjustment) is performed in step ST10, and a driving pulse P1 with a great effective electric power is supplied in the next cycle. On the other hand, in step ST5, in the event that rotation of the rotor 13 by the rotation pulse has been confirmed, level adjustment for lowering the effective electric power of the driving pulse P1 (second level adjustment) is performed in step ST6. In many cases, the effective electric power of the driving pulse is lowered at certain cycles. By means of performing such control, the power consumption of the driving pulse P1 can be reduced. Also errors in the movement of the hands can be done away with in areas where there are magnetic fields from electric household appliances. Thus, a timing device with high reliability and low power consumption can be provided. Fig. 5 illustrates a timing chart showing an example of driving pulses and the like being supplied from the control device according to the present embodiment to the stepping motor 10, as with the above-described Fig. 14. Fig. 5 illustrates the control signals supplied to the gates GP1, GN1, and GS1 of the p-channel MOS 33a, n-channel MOS 32a, and sampling p-channel MOS 34a for excitation of the driving coil 11 of a magnetic field of one polarity. It also shows the signals supplied to the gates GP2, GN2, and GS2 of the p-channel MOS 33b, n-channel MOS 32b, and sampling p-channel MOS 34b for excitation of a magnetic field of the reverse polarity. The portions common with Fig. 14 are denoted by the same reference numerals and description thereof is omitted. First, when time elapses in step ST1, there has been no output of auxiliary pulse P2 in the previous cycle, so the operation moves from step ST21 to ST2. In step ST2, the magnetic field detecting pulse SP0 is output at time t21 for detecting high-frequency noise magnetic field, thus starting the first cycle. Next, in steps ST23 and 24, control signals are supplied to output magnetic field detecting pulses SP1, for detecting alternating current magnetic fields, to both pole gates GP1 and GP2 at time t22 and t23. If there is no detection of magnetic field in the steps ST23 and 24, a driving pulse P1 of e.g., W10 in pulse width, is supplied at time t24 in step ST4. Following this, a rotation detecting pulse SP2 is output at time t25 in step ST5. When rotation of the driving rotor 13 is detected, this cycle is completed, so the system returns to step ST1 and conducts timing. Once the next cycle is started at time t31, a control signal for output of the magnetic field detecting pulse SP0 for detecting high-frequency noise magnetic field is supplied to the driving pole side gate GP2 which is on the reverse side as compared to the previous cycle. Subsequently, control signals are supplied to output magnetic field detecting pulses SP1, for detecting alternating current magnetic fields, to each pole gate GP2 and GP1 at time t32 and t33. If the electricity generating device 40 has started generating electricity, induction voltage generated by the magnetic field is obtained by one of the two magnetic field detecting pulses SP1 output to both pole sides. This is so even in the event that the magnetic field is such that it has been subjected to half-wave rectification and has directionality. In the event that the value thereof reaches the set value SV2, the magnetic field is detected in step ST23 or 24. Once the presence of the magnetic field has been detected, the rotor 13 is rotated in step ST7 in a sure manner by means of outputting an auxiliary pulse P2 with a great effective electric power at time t34 instead of the driving pulse P1. When the next cycle is started at time t41, judgement is made immediately in step ST21 whether or not an auxiliary pulse P2 has been output in the previous cycle. In the event that the auxiliary pulse P2 has been output, a demagnetising pulse PE is output immediately in step ST25. Following this the driving pulse P1 is output at time t42 in step ST26. The demagnetising pulse PE is a pulse of reverse polarity to that of the auxiliary pulse P2. By means of supplying the driving pulse P1 of the next cycle immediately following the demagnetising pulse PE, the substantial effective electric power output of the driving pulse P1 can be increased. Accordingly, during the time that electric power generation is being conducted and a magnetic field is present, or a residual magnetic field is present, the rotor 13 can be rotated in a sure manner. Thus, the rotation detection can be omitted, and the probability of erroneous detection can be done away with. Since the magnetic field detection capabilities also deteriorate due to the output of the auxiliary pulse P2, the fact that magnetic field detection can be omitted is immensely advantageous. Accordingly movement of the hands can be conducted in a sure manner. Further, the energy of the demagnetising pulse PE can be used to move the rotor, so that electricity consumed in rotating the rotor can be reduced as well. Once the driving pulse P1 is output in the step ST26, the system returns to step ST1 and conducts timing. Then, when the next cycles comes, the magnetic field detecting pulse SP0 for detecting high-frequency magnetic field noise is output at time t51, in the same manner as with that described above. Subsequently, pulses SP1 for detecting alternating current magnetic fields are sequentially output from both pole sides at time t52 and 53. When the electricity generating device has stopped generating electricity and a magnetic field is not detected, a driving pulse P1 is output at time t54. Subsequently, a rotation detecting pulse SP2 is output. In the event that there is no detection of rotation of the rotor 13 in step ST5, an auxiliary pulse P2 is output in the step ST7. Then, in this case, the demagnetising pulse PE is not output immediately after the auxiliary pulse P2, and the cycle is completed. Once the next cycle begins at time t61, first, the demagnetising pulse PE is output at time t61, and following this, the driving pulse P1 is output at time t62. Accordingly, the effective power of the driving pulse P1 is substantially increased. Thus, the rotor can be rotated in a sure manner in this case, as well. The driving pulse P1 output at time t62 has the effective electric power thereof increased since rotation could not be detected in the previous cycle. In the present embodiment, a driving pulse P1 with a pulse width W11 which is greater than that of the previous cycle is output to the stepping motor. Arrangements may be made wherein the effective electricity of the driving pulse P1 is controlled using voltage as well as pulse width or instead of pulse width. The timing device 1 according to the present embodiment is capable of controlling voltage using the booster/reducer circuit 49. Second Embodiment Next, description will be made regarding a second embodiment of the timing device I according to the present invention. Since the timing device 1 according to the present embodiment is common with the timing device described above with reference to Fig. 1, detailed description thereof with reference to the drawings will be omitted. The control device 20 of the timing device 1 according to the present embodiment makes aggressive use of the fact that judgement can be made whether the electricity generating device 40 is generating electricity or not, by means of monitoring the output voltage f12 of the booster/reducer circuit 49. That is, in the event that electricity generating device 40 is generating electricity, any fast-forward being performed by the driving pulse supplying section 24a is forcibly terminated. At the same time, taking into consideration that detection of rotation is difficult in the event that generation of electricity is being performed, control signals SP0 and SP1 for outputting magnetic field are not output. An auxiliary pulse P2 which has a great effective electric power and does not require rotation detection is output. The effective energy of the auxiliary pulse P2 is selected to be such that the rotor rotates in a sure manner, so there is no need to detect rotation of the rotor. Accordingly, error in the movement of the hands such as caused by noise being generated by rotation detection and judgement being made that the rotor is rotating even through it is not, can be prevented. On the other hand, supplying the auxiliary pulse P2 also decreases the magnetic field detection capabilities. Thus, the present embodiment further improves reliability in control by means of judging whether or not there is generation of electricity. Fig. 6 shows a schematic flowchart of the control method of the stepping motor employed in the timing device 1 according to the present embodiment. In this flowchart, the portions approximately corresponding with the aforementioned control method are denoted by the same reference numerals, and detailed description thereof will be omitted. First, in step ST1, one second is measured for movement of the hands. With the control device 20 according to the present embodiment, when one second elapses, judgement is made whether or not the electricity generating device 40 is operating, in step ST31. In the event that the electricity generating device 40 is operating, there is high probability that the driving voltage fluctuates. Thus, error in the movement of the hands occurs easily. Accordingly, any fast-forward control or reverse control being performed by fast-forward pulses or reverse pulses being supplied from the driving pulse supplying section 24a is forcibly terminated. Further, taking into consideration that detection of rotation easily causes errors in the event that generation of electricity is being performed by the electricity generating device 40, control signals SP0 and SP1 for outputting magnetic field are not output. An auxiliary pulse P2 is output instead of the pulse P1 in step ST7, thus driving the rotor 13. Thus, the timing device 1 according to the present embodiment, upon detecting that electricity is being generated, omits output of the magnetic field detecting pulses SP0 and SP1, and further omits the rotation detecting pulse P2. Thereby the arrangement optimally reduces power consumption when driving the rotor 13 using the auxiliary pulse P2 which has great effective power. In the event that generation of electricity is not being performed by the electricity generating device 40 in step ST31, the magnetic field detecting pulse SP0 is used for detecting an external high-frequency magnetic field in step ST2. The magnetic field detecting pulse SP1 is used for detecting an external alternating current magnetic field (low-frequency noise) in step ST3, as described above. Then, in the event that there is no detection of magnetic fields which would interfere with rotation detection in these steps, a driving pulse P1 is output in step ST4. Subsequently, a rotation detecting pulse SP2 is output in step ST5, thus detecting whether or not there is rotation of the rotor 13. In the event that rotation cannot be detected, an auxiliary pulse P2 is output in step ST7, thereby rotating the rotor 13 in a sure manner. Subsequently, a demagnetising pulse PE is output at the step ST8, and further, the level of the driving pulse P1 is adjusted, if necessary. On the other hand, in step ST5, in the event that rotation of the rotor by the driving pulse P1 is discerned, level adjustment is performed in step ST6 to lower the effective electric power of the driving pulse P1, if the conditions are favourable. Fig. 7 illustrates a timing chart showing an example of driving pulses and the like being supplied from the control device according to the present embodiment to the stepping motor 10. As with the above-described Fig. 5, Fig. 7 illustrates the control signals supplied to the gates GP1, GN1, and GS1 of the p-channel MOS 33a, n-channel MOS 32a, and sampling p-channel MOS 34a, and to the gates GP2, GN2, and GS2 of the p-channel MOS 33b, n-channel MOS 32b, and sampling p-channel MOS 34b, comprising the driving circuit 30. The portions common with the above-described are denoted by the same reference numerals and description thereof is omitted. First, when a certain amount of time (one second) elapses in step ST1, in the event that there is no operation of the electricity generation device 40 in step ST31, the operation moves to ST 2. In step ST2, the magnetic field detecting pulse SP0 is output at time t7 for detecting high-frequency noise magnetic field, thus starting the first cycle. Next, in step ST3, a magnetic field detecting pulse SP1 which detects alternating current magnetic fields is output to the gate GP2 of the of the driving pole and the reverse pole side at time t72. In the present embodiment, the state of operation of the electricity generation device 40 is checked in step ST31. Processing is performed whenever the device is operating, regardless of whether a magnetic field exists or not. Accordingly, there is no need to check whether or not a magnetic field exists. Hence, the magnetic field detecting pulse SP1 which detects the alternating current magnetic field is output to the side opposite to the driving side alone. In the event that these steps ST2 and 3 do not detect a magnetic field, the driving pulse P1 is output at time t73 in step ST4. Subsequently, a rotation detecting pulse SP2 is output at time t74 in step ST5. Then, when rotation of the driving rotor 13 is detected, this cycle is completed, and the system returns to step ST1 and conducts timing. When the next cycle is started at time t81, first, confirmation is made whether there is operation of the electricity generation device 40 or not. In the event that the device is operating, the system proceeds to step ST7. Then, control pulses for output of auxiliary pulses P2 to the gates GP2 and GN2 of the driving pole side reversed from the previous cycle, are supplied. The driving rotor 13 completely rotates by means of the auxiliary pulse P2, so that rotation detecting is unnecessary. Subsequently, the demagnetising pulse PE is output from the reverse pole side at time t82 in step ST8, thus completing the cycle. When the next cycle is started at time t83, if it is judged that there is operation of the electricity generation device 40 in step ST31, a process which is the same as that of the previous cycle is performed. That is, the system proceeds to step ST7, and then, control pulses for output of auxiliary pulses P2 to the gates GP1 and GN1 of the driving pole side reversed from the previous cycle, are supplied. The driving rotor 13 completely rotates by means of the auxiliary pulse P2, so that rotation detecting is unnecessary. Subsequently, the demagnetising pulse PE is output from the reverse pole side at time t84 in step ST8, thus completing the cycle. When the next cycle is started at time t91, if it is judged that there is no operation of the electricity generation device 40 in step ST31, the system proceeds to the step of detecting magnetic field in steps ST2 and 3, and outputs both high-frequency detecting pulse SP0 and low-frequency detecting pulse SP1. Then, in the event that a magnetic field is not detected, driving pulse P1 is output at time t93 and rotation or the rotor 13 is confirmed at time t94. In the event that a magnetic field is detected by either of the detecting pulses SP0 or SP1, a driving pulse P2 is output instead of the driving pulse P1, as with the previous cycle, thus rotating the rotor 13 in a sure manner and thereby omitting the process of detecting rotation. Thus, with the timing device 1 according to the present embodiment, a control method is employed wherein it is assumed that there is being output a magnetic field which effects the rotation detection of the stepping motor while the built-in electricity generating device 40 is generating electricity. Accordingly, the not-so-easy process of detecting magnetic field from the electricity generating device 40 is omitted. This simplifies the control and does away with error in movement of the hands. On the other hand, the consumption of electricity does tend to decrease during generation of energy since movement of the hands is conducted using an auxiliary pulse P2 which has great effective power. The steps of detecting magnetic fields and detecting rotation of the rotor can be omitted, so that an increase in the consumed electricity can be inhibited. Further, taking into consideration the fact that there is the possibility that the driving voltage fluctuates during the generation of electricity, fast-forward is forcibly terminated. Thus, according to the present embodiment, a timing device can be provided with extremely high reliability, which does away with error in the movement of the hands, by means of performing control of the stepping motor 10 by aggressively using whether or not the device is generating electricity. Third Embodiment Next, description will be made regarding a third embodiment of the timing device 1 according to the present invention. Since the timing device 1 according to the present embodiment is common with the timing device described above with reference to Fig. 1, detailed description thereof with reference to the drawings will be omitted. The control device 20 of the timing device 1 according to the present embodiment focuses on the fact that once a magnetic field is detected and the auxiliary pulse P2 is output, the electricity generating device 40 continues to operate for a certain period. Thus, the present embodiment assumes that there is a magnetic field for a certain number of cycles and performs processing accordingly, thereby obtaining high reliability. The driving pulse supplying unit 24a of the driving control circuit 24 of the control unit 20 of the present embodiment is arranged such that in the event that an auxiliary pulse P2 is output, a driving pulse is supplied which is of a level several degrees greater in effective electric power than the driving pulse P1 being supplied at that time. Also, assuming that generating of electricity is occurring whenever a magnetic field is detected, fast-forward and reverse operations are forcibly terminated in order to prevent error in movement of the hands accompanying voltage fluctuation. The supply of the auxiliary pulses P2 tends to deteriorate the magnetic field detecting capabilities. Accordingly, an arrangement may be employed wherein detection of the magnetic field is not performed for a predetermined number of cycles and wherein driving pulses with great effective electrical power are output, in order to make up for the deterioration in the magnetic field detecting capabilities. Fig. 8 shows a schematic flowchart of the control method of the stepping motor employed in the timing device 1 according to the present embodiment. In this flowchart, the steps approximately corresponding with those of the aforementioned control method are denoted by the same reference numerals, and detailed description thereof will be omitted. First, in step ST1, one second is measured for movement of the hands. With the control device 20 according to the present embodiment, when one second elapses, judgement is made whether or not the preceding cycle is within a predetermined C number of cycles (certain time span) since the auxiliary pulse P2 was output in step ST41. In the control method according to the present embodiment, if the number of cycles from the most recent auxiliary pulse P2 output is within C number of cycles; this means that the state is such wherein it can be assumed that there may be a magnetic field continuing to be present, or effects of a residual magnetic field, meaning that this is a period wherein magnetic field detection capabilities would deteriorate. Accordingly, detection of the magnetic field was not performed within C number of cycles from the auxiliary pulse P2. Short pulses such as fast-forward and reverse pulses are forcibly terminated in step ST42. A driving pulse is supplied in step ST 43 which is of a level several degrees greater in effective electric power than the driving pulse P1 being supplied at that time, thus rotating the rotor 13 in a sure manner. Thus, rotation detection can be omitted, so error in the movement of the hands is done away with. Then, the system returns to step ST1 and conducts timing. On the other hand, in the event that the number of cycles from the output of the auxiliary pulse P2 exceed the C number of cycles, as described above, the magnetic field detecting pulse SP0 is used for detecting external high-frequency magnetic field in step ST2. Detection of alternating current magnetic field is conducted with both pole sides in step ST23 and step ST24. Thus, the magnetic field from the electricity generating device 40 can be caught with high frequency. In the event that there is detection of a magnetic field in these steps, mistaken detection can be easily made based on the judgement of whether or not there is rotation of the rotor 13. Thus, the system proceeds to step ST17 and supplies auxiliary pulses P2 with great effective electrical power. In the event that there is no detection of magnetic fields which might interfere with detection of rotation in these steps, the driving pulse P1 is output in step ST4. Subsequently, the rotation detecting pulse SP2 is output in the step ST5 to determine whether or not there is rotation of the rotor 13. In the event that rotation cannot be confirmed, an auxiliary pulse P2 with great effective electrical power is supplied in step ST7, thereby rotating the rotor 13 in a sure manner. Subsequently, a demagnetising pulse PE is output in step ST8, and further, the level of the driving pulse P1 is adjusted, if necessary. On the other hand, in step ST5, in the event that rotation of the rotor 13 by the driving pulse P1 is discerned, level adjustment is performed in step ST6 to lower the effective electric power of the driving pulse P1, if the conditions are favourable. Fig. 9 illustrates a timing chart showing an example of driving pulses and the like being supplied from the control device according to the present embodiment to the stepping motor 10. As with the above-described Fig. 7, Fig. 9 illustrates the control signals supplied to the gates GP1, GN1, and GS1 of the p-channel MOS 33a, n-channel MOS 32a, and sampling p-channel MOS 34a, and to the gates GP2, GN2, and GS2 of the p-channel MOS 33b, n-channel MOS 32b, and sampling p-channel MOS 34b, comprising the driving circuit 30. The portions common with above-described are denoted by the same reference numerals and description thereof is omitted. First, when a certain amount of time (one second) elapses in step ST1 shown in Fig. 8, in the event that C number of cycles have already elapsed from the auxiliary pulse P2 in step ST41, the operation proceeds to ST 2. In step ST2, the magnetic field detecting pulse SP0 is output at time t101 for detecting a high-frequency noise magnetic field, thus starting the first cycle. Next, in steps ST23 and 24, control signals for outputting magnetic field detecting pulses SP1 which detect alternating current magnetic fields are supplied in order to the reverse pole side gate GP2 and driving pole side gate GP1 at time t102 and t103. This outputs magnetic field detecting pulses SP1 of differing polarities for detecting alternating current magnetic fields. In the event that there is no detection of magnetic fields in these steps, a driving pulse P of V10 voltage is supplied at time t104 in step ST4. Then, in step ST5, the presence or absence of rotation of the driving rotor 13 is detected at time t105. In the event that the driving rotor 13 is rotated, the system returns to step ST1 and conducts timing. When the next cycle is started at time t111, a high-frequency magnetic field detecting pulse SP0 is output as described above. Subsequently, an alternating current magnetic field detecting pulse SP1 is output at time t112 and time t113. In the event that a magnetic field is detected by the magnetic field detecting pulse SP1 on the driving pole side which was output at time t113, the system proceeds to step ST7. An auxiliary pulse P2 with great effective electrical power is output in step ST7 at time t114. Subsequently, a demagnetising pulse PE is output at time t115, thus completing this cycle. When the next cycle starts at time t121, in step ST41, the value of C is set to 2, for example, so the present cycle is within the certain time period from the output of the auxiliary pulse P2 in the previous cycle. Accordingly, the system proceeds to step ST42, and the various steps of detecting magnetic fields are not performed. In the event that fast-forward is being performed, this is forcibly terminated in step ST42. In the case of normal driving, a driving pulse is selected and output in step ST43. This driving pulse is of a level several degrees greater in effective electric power than the driving pulse P1 which was supplied at time t104. With the timing device 1 according to the present embodiment, a booster/reducer circuit 49 can be used to change the voltage, so at time t121, a driving pulse having voltage of V11 greater in effective electric power than the driving pulse P1 output under the conditions in which the magnetic field was detected. Thus, errors in movement of the hands can be done away with, even under situations where there is presence of a noise magnetic field, even without performing rotation detection, thereby realising a timing device with high reliability. When the next following cycle is started at time t131, 2 is set for C in step ST41, so this cycle also is within the certain time period. Accordingly, a driving pulse P1 great in voltage and great in effective electric power is output in step ST43 at time t131. When the next cycle starts at time t141, the present cycle is out of the certain time period, so again the magnetic field detecting pulses SP0 and SP1 each are output at times t141, t142, and t143 so as to detect whether or not there is presence of a magnetic field. Then, in the event that presence of a magnetic field is not detected, a driving pulse P1 with the normal effective electrical power of voltage of V10 as that of time t104 is output at time t144. A rotation detecting pulse SP2 is output at time t145. On the other hand, if a magnetic field is detected at this time, an auxiliary pulse P2 is output again, and driving pulses P1 of a great effective electrical power are output from the predetermined two cycles. Further, although Fig. 9 illustrates employing of a pulse with great voltage as a driving pulse with great effective electrical power, it goes without saying that the effective electrical power may be controlled by pulse width, and both voltage and pulse width may be used for controlling the effective electrical power. Or, the driving pulse P1 and the auxiliary pulse P2 may be comprised of a plurality of sub-pulses, and control the effective electrical power according to the duty ratio thereof. Further, detection of magnetic fields may be conducted at each cycle even following output of the auxiliary pulse, in order to further increase magnetic field detecting capabilities during generation of electricity. Fourth Embodiment Next, description will be made regarding a fourth embodiment of the timing device 1 according to the present invention. Since the timing device 1 according to the present embodiment is common with the timing device described above with reference to Fig. 1, detailed description thereof with reference to the drawings will be omitted. The control device 20 of the timing device 1 according to the present embodiment is arranged so as to further improve the detection frequency of magnetic fields. This is to facilitate detection of noise magnetic fields and so forth generated at the electricity generating device 40 which are 100 ms or so in duration, i.e., short. Accordingly, the magnetic field detecting pulse supplying unit 24c of the driving control circuit 24 of the control unit 20 of the present embodiment supplies magnetic field detecting pulses SP1 before the driving pulse P1, and also supplies magnetic field detecting pulses SP1 again following the rotation detecting pulse SP2. Further, the polarity of the magnetic field detecting pulses SP1 are changed, in order to further improve the probability of detecting noise magnetic fields. Fig. 10 shows a schematic flowchart of the control method of the stepping motor employed in the timing device 1 according to the present embodiment. In this flowchart, the steps approximately corresponding with the those in the aforementioned control method are denoted by the same reference numerals, and detailed description thereof will be omitted. First, in step ST1, one second is measured for movement of the hands. Next, the magnetic field detecting pulse SP0 is used for detecting an external high-frequency magnetic field in step ST2. The magnetic field detecting pulse SP1 is used for detecting an external alternating current magnetic field (low-frequency noise) at one pole side in step ST23, as described above. In the event that there is detection of magnetic field in these steps, mistaken detection can be easily made based on the judgement of whether or not there is rotation of the rotor 13. Thus, the system proceeds to step ST17 and supplies auxiliary pulses P2 with great effective electrical power. At the same time, supplying of short pulses such as fast-forward pulses is forcibly terminated in step ST15. In the event that there is no detection of magnetic fields which might interfere with rotation detection in these steps, a driving pulse P1 is supplied in step ST4. Then, in step ST5, the presence or absence of rotation of the rotor 13 is detected by outputting a rotation detecting pulse SP2. In the event that rotation cannot be confirmed, an auxiliary pulse P2 with great effective electrical power is supplied in step ST7, thereby rotating the rotor 13 in a sure manner. Subsequently, a demagnetising pulse PE is output in step ST8, and further, the level of the driving pulse P1 is adjusted, if necessary. On the other hand, in step ST5, in the event that rotation of the rotor 13 by the driving pulse P1 is discerned, in the step ST24 immediately after the magnetic field detecting pulse SP1 is used for detecting external alternating current magnetic field (low-frequency magnetic field) at the pole side opposite to that of step ST23. In the event that an alternating current magnetic field is detected in step ST24, there is a high possibility that there has been a mistaken detection, so the auxiliary pulse P0 is supplied in step ST7 in the same way as with the above embodiment. Thus, the probability of detecting the magnetic field can be greatly improved, by means of detecting alternating current magnetic field by supplying magnetic field detecting pulses SP1 at two steps: the timing before supplying the driving pulse P1, and the timing following the rotation detecting pulse SP2. Particularly, the timing of the electricity generating device 40 generating electricity is irregular, and also the generating time is usually short. Accordingly even in the event that a noise magnetic field has not been generated at the timing before supplying the driving pulse P1, a noise magnetic field may have been generated at the timing of the rotation detecting pulse SP2 being supplied. The control device 20 and the control method according to the present embodiment deal with such noise by means of detecting magnetic fields at a timing following the rotation detecting pulse SP2 as well. Thus, the probability that noise magnetic fields generated either during supplying of the driving pulse P1 or during supplying of the rotation detecting pulse SP2 can be detected is high. Accordingly, confirmation can be made regarding whether or not there is mistaken detection of noise magnetic fields, and highly reliable judgement can be made regarding whether or not the rotor has rotated. Fig. 11 illustrates a timing chart showing an example of driving pulses and the like being supplied from the control device according to the present embodiment to the stepping motor 10. As with the above-described Fig. 7 and others, Fig. 11 illustrates the control signals supplied to the gates GP1, GN1, and GS1 of the p-channel MOS 33a, n-channel MOS 32a, and sampling p-channel MOS 34a, and to the gates GP2, GN2, and GS2 of the p-channel MOS 33b, n-channel MOS 32b, and sampling p-channel MOS 34b, comprising the driving circuit 30. The portions common with above-described are denoted by the same reference numerals and description thereof is omitted. When a certain amount of time (one second) elapses in step ST1 shown in Fig. 10, the magnetic field detecting pulse SP0 used for detecting high-frequency noise magnetic fields is output at time t151 and the first cycle is started. Next, in step ST23, a control signal to output a magnetic field detecting pulse SP1 which detects alternating current magnetic fields is supplied to the gate GP2 which is the reverse pole side. A magnetic field detecting pulse SP1 is output at time t152. In the event that magnetic fields are not detected in these steps, a driving pulse P1 of a pulse width W10 is supplied in step ST4 at time t153. Then in step ST5, the presence or absence of rotation of the driving rotor 13 is detected at time t154. Following this rotation detection, at time t155 a control signal, to output a magnetic field detecting pulse SP1 which detects alternating current magnetic fields, is supplied in step ST24 to the gate GP1 which is the driving side, and the second detection of low-frequency magnetic field is performed. Then, in the event that a magnetic field is detected by the second magnetic field detecting pulse SP1, the system proceeds to step ST7. A auxiliary pulse P2 with great effective electric power of a pulse width of W20 is output at time t156, and further, at time t157, a demagnetising pulse PE is output. Next, when the next cycle is started at time t161, a high-frequency magnetic field detecting pulse SP0 is output the same as above. Subsequently, a pulse SP1 which detects alternating current magnetic fields is output at time t162. In the event that a magnetic field is not detected at this timing, a driving pulse P1 is supplied at the time t163, and a rotation detecting pulse SP2 is supplied at time t164. Further, the second magnetic field detecting pulse SP1 is output at time t165. In the event that a magnetic field is not detected at this timing either and that rotation of the rotor has been detected by the rotation detecting pulse SP2, it is judged that the rotor has unmistakably rotated, and this cycle thus is completed. Also, as shown in Fig. 11, the arrangement is such that the reverse pole side magnetic field detecting pulse SP1 is output before the driving pulse P1. The driving pole side magnetic field detecting pulse SP1 is output following the rotation detecting pulse SP2, so as to allow detection of noise magnetic field on the side at which error occurs easily during rotation detection. Of course, the driving pole side magnetic field detecting pulse SP1 may be output first, and the reverse pole side magnetic field detecting pulse SP1 may be output later. Or, magnetic field detecting pulses SP1 of differing polarities may each be output first. Then, following the rotation detecting pulse SP2, once more output magnetic field detecting pulses SP1 of one pole or two field detecting pulses SP1 of differing poles. This thereby further increases the probability of detection of a magnetic field. As described above, the timing device 1 according to the present embodiment increases the probability of magnetic field detection so that magnetic fields from the built-in electricity generating device can be detected. It also avoids the effects of the magnetic field from the electricity generating device in addition to that of external magnetic fields. This is achieved by means of performing processes wherein it is assumed that a magnetic field is present during generating of electricity, and so forth. Thereby, hand movement can be conducted with high precision even in timing devices which have a built in electricity generating device which generates electricity irregularly. This vastly improves the precision of timing devices which can be used without a battery. Also, it is needless to say that the present invention is by no means limited to timing devices such as wristwatches or the like. It can be provided for multiple-function timepieces such as chronographs or other generating devices, and also other devices and apparatuses with stepping motors built in. Incidentally, the waveform of the pulses described above, i.e., the driving pulse P1, auxiliary pulse P2, magnetic field detecting pulses SP0 and SP1, and rotation detecting pulse SP2, etc. are illustrated as examples. It goes without saying that the waveforms can be set according to the properties of the stepping motor 10 employed in the timing device. Also, in the above example, the present invention has been described with an example of a two-phase stepping motor which is favourably used in timing devices. The present invention can be also applied to stepping motors of three-phase and higher, in the same manner. Also, instead of performing common control of each phase, the driving pulses may be provided at pulse widths and timing appropriate for each phase. The stepping motor is by no means restricted to single-phase excitation, and may employ two-phase excitation or 1-2 phase excitation. As described above, the control method and the control device according to the present invention increases the probability of magnetic field detection so that magnetic fields from the electricity generating device can be detected. It performs processes wherein it is assumed that there is presence of a magnetic field during generation of electricity and a driving pulse with great effective electric power or an auxiliary pulse is applied. The invention performs processes wherein it is assumed that there is a detected magnetic field which is a magnetic field from the electricity generating device. Accordingly, the effects of a magnetic field from an electricity generating device in a timing device or the like with a stepping motor can be greatly inhibited. Thus, a timing device can be provided which can be used anytime and anywhere without a battery and which operates hand movement without error and at high precision. This is achieved by means of employing the control device and the control method according to the present invention.

Claims: A control device (20) for a stepping motor (10) wherein a driving rotor (13) is rotatably driven by driving pulses via a driving coil (11), said stepping motor (10) being subjected to an alternating magnetic field by electric power generated by an electricity generating device (40) driven by kinetic energy transferring means (45); said control device comprising: driving means (24a) for supplying at least one driving pulse (P1) to said driving coil (11) for driving said stepping motor (10), and characterised by : means (24, 25) for reducing the effects of magnetic fields external to said stepping motor (10) upon the operation of said stepping motor (10). A control device as claimed in claim 1 characterised in that said means (24,25) comprises: rotation detecting means (24b) for supplying at least one rotation detection pulse (SP2) for induction of a rotation detecting induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means (24c) for supplying at least one magnetic field detection pulse (SP0, SP1) for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means (25) for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values (SV2), thus judging whether or not there is rotation and whether or not an external magnetic field is present; and auxiliary means (24d) for supplying an auxiliary pulse (P2) of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said magnetic field detecting means is capable of supplying first and second magnetic field detecting pulses of differing polarity to said driving coil prior to said driving pulse, the first and second magnetic field detecting pulses being capable of detecting magnetic fields in approximately the same frequency band as each other. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: rotation detecting means for supplying at least one rotation detection pulse for induction of a rotation detecting induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means for supplying at least one magnetic field detection pulse for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values, thus judging whether or not there is rotation and whether or not an external magnetic field is present; and auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said magnetic field detecting means is capable of supplying said magnetic field detecting pulse to said driving coil prior to said driving pulse and immediately following said rotation detecting pulse. A control device as claimed in claim 1, wherein said electric power is supplied via condenser means (48), and characterised in that said means (24, 25) comprises: rotation detecting means for supplying rotation at least one detection pulse for induction of a rotation detecting induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means for supplying magnetic field detection pulses for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values, thus judging whether or not there is rotation and whether or not an external magnetic field is present; and auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said judging means is capable of adjusting said set value used for judging said magnetic field detecting induction voltage, by means of the charged voltage of said condenser means. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: rotation detecting means for supplying at least one rotation detection pulse for induction of a rotation detecting induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means for supplying at least one magnetic field detection pulse for induction of a magnetic field detecting induction voltage for detection of external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values, thus judging whether or not there is rotation and whether or not an external magnetic field is present; and auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said auxiliary means provides said auxiliary pulse when said generating device is generating electricity. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse when said generating device (40) is generating electricity. A control device as claimed in claim 6 characterised in that said auxiliary means supplies said auxiliary pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: short-pulse supplying means (24a) for supplying to said driving coil short-pulse pulses which are shorter in cycle that said driving pulses; and wherein said short-pulse supplying means stops supplying said short-pulse pulses when said generating device is generating electricity. A control device for a stepping motor according to Claim 8, characterised in that a short-pulse pulse is at least one of either a fast-forward pulse or a reverse pulse. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: rotation detecting means for supplying at least one rotation detection pulse for induction of a rotation detection induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means for supplying at least one magnetic field detection pulse for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage respectively with respective set values, thus judging whether or not there is rotation and whether or not an external magnetic field is present; and auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said driving means is capable of supplying driving pulses of a plurality of effective electric powers, and supplies at least one driving pulse which is of greater effective electric power than an immediately preceding driving pulse, following said auxiliary pulse being supplied. A control device for a stepping motor according to Claim 10, characterised in that said driving means (24) is capable of supplying driving pulses (P1) with differing pulse widths. A control device for a stepping motor according to Claim 10, characterised in that said driving means (24) is capable of supplying driving pulses (P1) with differing voltages. A control device as claimed in claim 1, characterised in that said means (24, 25) comprises: rotation detecting means for supplying at least one rotation detection pulse for induction of a rotation detecting induction voltage for detection of rotation of said driving rotor, said rotation detection pulse being supplied following said driving pulse; magnetic field detecting means for supplying at least one magnetic field detection pulse for induction of a magnetic field detecting induction voltage for detection of an external magnetic field, said magnetic field detection pulse being supplied prior to said driving pulse; judging means for comparing the rotation detecting induction voltage and magnetic field detecting induction voltage with respective set values, thus judging whether or not there is rotation and whether or not an external magnetic field is present; auxiliary means for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and demagnetising means (24e) for providing following said auxiliary pulse at least one demagnetising pulse (PE) of which the polarity is different to that of said auxiliary pulse, in order to perform demagnetising following said auxiliary pulse; and wherein said demagnetising means (24e) provides said demagnetising pulse (PE) immediately prior to a driving pulse (P1) which follows said auxiliary pulse (P2). A control method for a stepping motor (10) wherein a driving rotor (13) is rotatably driven by driving pulses via a driving coil (11), said stepping motor being subjected to an alternating magnetic field by electric power generated by an electricity generating device (40) driven by kinetic energy transferring means (45); said control method comprising: a driving step for supplying at least one driving pulse (P1) to said driving coil (11) for driving said stepping motor (10), and characterised by : a step for reducing the effects of magnetic fields external to said stepping motor (10) upon the operation of said stepping motor (10). A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a rotation detecting step for outputting to said driving coil at least one rotation detection pulse (SP2) following said driving pulse (P1), and comparing the induction voltage of the rotation detection pulse with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to said driving coil at least one magnetic field detection pulse (SP0, SP1) for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; and an auxiliary step for supplying an auxiliary pulse (P2) of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein the magnetic field detecting pulse (SP0, SP1) is of differing polarity to said driving pulse (P1) in order to detect a magnetic field of approximately the same frequency band as pulses applied to said driving coil (11). A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a rotation detecting step for outputting to said driving coil at least one rotation detection pulse following said driving pulse, and comparing the induction voltage of the rotation detection pulse with a first set value, thereby detecting whether or not there is rotation; a first magnetic field detecting step for outputting to said driving coil at least one first magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the first magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; a second magnetic field detecting step for outputting to said driving coil at least one second magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output following said rotation detecting pulse, and comparing the induction voltage of the second magnetic field detection pulse with a set value, to detect whether or not an external magnetic field is present; and an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected. A control method as claimed in claim 14, wherein said electric power is supplied via condenser means (48), characterised in that said step for reducing the effects of magnetic fields comprises: a driving step for supplying at least one driving pulse to said driving coil for driving said driving rotor; a rotation detecting step for outputting to said driving coil at least one rotation detection pulse following said driving pulse, and comparing the induction voltage of the rotation detection pulse with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to said driving coil at least one magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; and an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said magnetic field detecting step allows adjustment of said second set value by means of the charged voltage of said condenser means. A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a rotation detecting step for outputting to said driving coil at least one rotation detection pulse following said driving pulse, and comparing the induction voltage of the rotation detection pulse with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to said driving coil at least one magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; and an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and wherein said auxiliary step supplies said auxiliary pulse when said generating device is generating electricity. A control method as claimed in claim 14, characterised in that said means (24, 25) comprises: an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse characterised in that said auxiliary step provides said auxiliary pulse when said generating device is generating electricity. A control method as claimed in claim 19 characterised in that said auxiliary pulse is provided in the event that said driving rotor does not rotate or when an external magnetic field has been detected. A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a driving step for supplying driving pulses to said driving coil for driving said driving rotor; and a short-pulse supplying step for supplying to said driving coil short-pulse pulses which are shorter in cycle that said driving pulses; characterised in that said short-pulse supplying step stops supplying said short-pulse pulses when said generating device is generating electricity. A control method for a stepping motor according to Claim 21, characterised in that a short-pulse pulse is at least one of either a fast-forward pulse or a reverse pulse. A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a rotation detecting step for outputting to said driving coil at least one rotation detection pulse following said driving pulse, and comparing the induction voltage of the rotation detection pulse with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to said driving coil at least one magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and a second driving step for supplying at least one driving pulse which is of greater effective electric power than an immediately preceding driving pulse, following said auxiliary pulse being supplied. A control method for a stepping motor according to Claim 23, characterised in that said second driving step supplies driving pulses with differing pulse widths. A control method for a stepping motor according to Claim 23, characterised in that said second driving step supplies driving pulses with differing pulse voltages. A control method as claimed in claim 14, characterised in that said step for reducing the effects of magnetic fields comprises: a rotation detecting step for outputting to said driving coil at least one rotation detection pulse following said driving pulse, and comparing the induction voltage of the rotation detecting pulse with a first set value, thereby detecting whether or not there is rotation; a magnetic field detecting step for outputting to said driving coil at least one magnetic field detection pulse for detection of an external magnetic field, said magnetic field detection pulse being output prior to said driving pulse, and comparing the induction voltage of the magnetic field detection pulse with a second set value, to detect whether or not an external magnetic field is present; an auxiliary step for supplying an auxiliary pulse of effective electric power greater than said driving pulse in the event that said driving rotor does not rotate or when an external magnetic field has been detected; and a demagnetising step for providing following said auxiliary pulse at least one demagnetising pulse (PE) of which the polarity is different to that of said auxiliary pulse, in order to perform demagnetising following said auxiliary pulse; and wherein said demagnetising step provides said demagnetising pulse immediately prior to a driving pulse which follows said auxiliary pulse. A timepiece apparatus, comprising: a control device for a stepping motor according to any of Claims 1 to13; a stepping motor which transports timepiece hands by means of said driving pulse; and said electricity generating device.

Inventors: HARA TATSUO, HARA, TATSUO
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1998
Main classification: G04C3
IPC codes: G04C3, H02P8, H02K37