GB2101367A - Improvements in or relating to stepping electric motor driven electronic timepieces - Google Patents

Abstract

In a stepping motor driven electronic timepiece a detection pulse is supplied to the motor coil to set up, across a detection resistance, a detection voltage the magnitude of which is indicative of whether the motor is in a rotation or a non-rotation condition. A path for the detection pulse current is established through the detection resistance and the coil in series only after establishment of a path which does not include said resistance. In Figure 8 the motor coil is shown at 7, and 40, 41, 42, 43, 44 and 45 represent electronic switches. 24 is the detection resistance. Figure 8a shows the switching state in which there is no detection current path; Figure 8b shows the path 46 in which the coil is included and the detection resistance is not; and Figure 8c shows the path 47 in which the coil and the detection resistance are in series. <IMAGE>

Description

SPECIFICATION Improvements in or relating to stepping electric motor driven electronic timepieces This invention relates to stepping electric motor driven electronic timepieces. More Bpecifically the invention relates to such timepieces in which what is herein termed automatic driving pulse width control is employed, that is to say to stepping motor driven electronic timepieces in which, in order to achieve economy in power consumption, the driving pulses fed to the motor are automatically changed in width so as to suit prevailing load and other circumstances, narrower driving pulses being used so long as the motor is in the rotation condition, i.e. able to develop, from the driving pulses being fed to it, sufficient torque to continue to rotate correctly against the load imposed on it at the time, but wider driving pulses (correction pulses) being used if, when a too narrow pulse is applied, the motor assumes the non-rotation condition, i.e. is unable to develop from the pulse sufficient torque to continue to rotate correctly against its load.

The invention is illustrated, in and explained with the aid of the accompanying drawings, in which: Figure 1 is a view showing a display mechanism of a known analogue display electronic timepiece, Figure 2 is a block diagram showing a conventional circuit construction of such a timepiece, Figure 3 is a view of a portion of the mechanism shown in Figure 1 to show the magnetic path inside the stepping motor when the coil is so energised as to drive the rotor, Figure 4 is a view similar to Figure 3 but showing the magnetic path inside the stepping motor when the coil is energised to attract the rotor, Figure 5 is a diagrammatic view of a known detection circuitry, Figure 6 is a view showing waveforms of the detection pulses produced by the known detection circuitry, Figure 7 is a graph to illustrate the onset of the detection current, Figures 8(a) (b) (c) are views illustrating an embodiment of this invention, Figures 9(a) (b) (c) show a detection pulse and current waveforms, Figure 10 is a diagram showing the waveform of pulses applied to a coil, Figures 11 and 12 are views illustrating the operation of a stepping motor, Figure 13 is a circuit diagram of a driver circuit and a detector circuit, Figures 14(a) and 20(a) show the waveforms of detection currents, Figures 14(b) and 20(b) show the waveforms of detection voltages, Figure 1 5 is a block diagram of a timepiece incorporating the detector circuit and driver circuit shown in Figure 13, Figure 1 6 is a diagram showing the waveforms of pulses produced by a pulse synthesiser shown in Figure 15, Figure 1 7 is a circuit diagram of a controller e.g. as shown in Figure 15, Figure 18 is a circuit diagram of a driver and detector e.g. as illustrated in Figure 15, Figure 1 9 is a timing chart of signals generated in a controller, and a driver and detector, Figure 21 is a circuit diagram of a driver and detector circuit according to an embodiment of the present invention, Figure 22 is a timing chart for operations of the circuit arrangement shown in Figure 21, Figure 23 shows a magnetic hysteresis curve, Figures 24, 25,26,28,29, 30, 31, 32 and 33 are views illustrating the operation of a stepping motor, Figure 27 is a diagram showing the waveforms of currents flowing through a motor coil upon application of pulses Pi, Figure 34 is a diagram showing the waveforms of detection voltages generated by detection pulses Ps1, Ps2... Psn, Figure 35 is a diagram showing the waveforms of detection voltages produced by a detection pulse Ps applied in a zone A", Figure 36 illustrates a circuit for producing a masking signal in a zone for setting a detection resistor, Figure 37 shows a circuit for generating detection signals, Figure 38 shows a circuit for establishing a detection resistor, Figure 39 illustrates a circuit for comparing detection voltages at Oi, 02 with a reference voltage, Figure 40 is a timing chart showing operations of the circuit of Figure 36, Figure 41 is a timing chart explanatory of the operation of the circuit of Figure 37, Figure 42 is a diagram illustrating the waveforms of detection voltages produced during normal operation, Figure 43 shows the waveforms of detection voltages generated by detection pulses upon setting of a detection resistor, and Figure 44 is a circuit diagram showing another circuit arrangement according to the present invention.

The accompanying Figure 1 shows schematically the pulse energised stepping motor and associated gearing of a typical analogue electronic timepiece displaying time by means of hands and also having a calendar mechanism. The motor, which is known per se, has a magnetically saturable stator 1, a driving coil 7 to which driving pulses are fed, and a permanently magnetised rotor 6 which drives, by means of a gear wheel system represented by gear wheels referenced 2 to 5, second, minute and hour hands (not shown) and the calendar mechanism (also not shown).

The accompanying Figure 2 shows in simplified block diagram form, what may be termed the electronic part of the timepiece. This consists of a relatively high frequency piezo-electric crystal controlled time-base oscillator 10, a multi stage frequency divider 11 and a pulse synthesiser 12 for producing pulses required by the motor (represented in Figure 2 by its coil 7) and supplying them to a motor driving circuit 1 3.

Successive driving pulses are of opposite polarities and, so long as the driving pulses supplied to the motor are wide enough to provide sufficient torque to overcome the load on the motor, each applied driving pulse will cause the rotor to rotate, always in the same direction, through a half revolution.

Until fairly recently, the driving pulses were always made of a constant width large enough to overcome any load which could reasonably be expected to be imposed on the motor-indeed such constant width driving pulses are used at the present time in large numbers of known timepieces. But the actual load on the motor is far from constant. Most of the time it is small enough for relatively narrow pulses to be sufficient to drive the motor properly but at other times, notably during the few hours out of the 24, during which the calendar mechanism is being driven to change the date and day displayed, the load may be several times greater.Again, in a watch in which the source of power is a battery, the internal resistance of the battery will be increased if the ambient temperature becomes low, its voltage will be decreased, the output torque of the motor will be reduced, and the motor will require wider driving pulses to drive it properly than it would do if the ambient temperature were normal and other circumstances were the same.

Further, the friction load may be increased by secular variations. Accordingly, the common present day practice of using constant width pulses adequately wide enough to keep the motor rotating correctly despite variations in the load thereon and in other prevailing circumstances, results in a very substantial waste of power-a very important defect in battery driven timepieces, and notably in wristwatches, since it prevents such a watch being operated by a longlife battery of desirably small physical size.

Automatic driving pulse width control is a fairly recent development by means of which this defect is avoided and which involves normally using relatively narrow driving pulses wide enough to drive the motor correctly for a large part of the time and, when the load or other circumstances become such that the motor assumes the non-rotation condition, detecting that such a condition exists and increasing the pulse width to meet the changed circumstances.

In this way it is possible, by detecting whether the rotation or the non-rotation condition exists, to change the applied pulse width to increase it or decrease it to suit the state of load or motor output torque prevailing at the time. Clearly the most important thing for determining the driving pulse width-the optimum pulse width-to be selected in any set of circumstances at a given time, lies in the detection of whether the motor is in the rotation condition or the non-rotation condition at that time. Various methods have been proposed for effecting such detection of the condition. These methods can be roughly classified as falling into one or other of two classes. In one class the voltage induced in the motor coil by transient oscillation of the rotor occurring after a driving pulse is detected. In the other the position in which the rotor stops (after a driving pulse) is detected.The first method has been put into practice but this method is delicate in operation and involves such accuracy of measurement to effect detection, and such practical difficulties in utilising the results of detection, that the method is not regarded as wholly satisfactory for, and of sufficient operating stability for, adoption in timepieces which are to be made by mass production methods.

Accordingly the second method, that of effecting detection by determining the stable position in which the rotor stops after a driving pulse, offers substantial advantages over the first because it does not depend upon transient oscillation of the rotor and it is this second method which is used in carrying out the present invention.

One proposed way of detecting whether the rotation or the non-rotation condition exists by detecting the position in which the rotor stops after a driving pulse, will now be described. In accordance with this proposal the difference in the inductance presented by the coil in different positions of the rotor is made use of to determine the position of the rotor when it stops after a driving pulse has ceased. Referring to Figures 3 and 4, if a short detection pulse is passed through the coil 7, the direction of the produced magnetic flux passing through the saturable portions (recesses) 1 9-a, 1 9-b, of the stator illustrated (it is a one-piece stator) is different if the rotor 6 stops in the position shown in Figure 3 from what it is if the rotor stops in the position shown in Figure 4.

As illustrated by Figure 3, excitation of the coil 7 causes a magnetic flux represented at 22-a, 22-b to pass through the saturable portions 19-a, 1 9-b, but the passage of this flux is resisted because the said portions reach saturation or near saturation due to the combined effect of this flux and the rotor flux. The inductance presented by the coil is therefore small. As illustrated by Figure 4, however, because the polarity of the rotor is reversed (as compared with Figure 3), the inductance presented by the coil is larger than in the case of Figure 3. This difference in inductance values produces a difference in the onset of the detecting pulse current and this is utilisable for effecting detection.

Figure 5 shows, purely diagrammatically (the switches in the figure are represented as mechanical switches although in practice they would be electronic ones) circuitry by means of which detection can be effected. Referring to Figure 5, 7 is again the motor coil, 24 is a resistance-the detection resistance-and 25, 26, 27, 28, 29, 30 are switches controlling the passage of the detecting pulse. Figure 5(a) shows the state in which the rotor is stopped in a stable position and no pulse current flows through the coil.Figure 5(b) shows the state in which detection current begins to flow through the coil 7 and the resistance element 24 in series therewith as the result of closing the switches 25, 30. The different potentials Vs produced at the point x at the "live" end of the detection resistance 24 will have waveforms such as shown in Figure 6.

Figure 6(a) illustrates the detection pulse of width Ts and Figure 6(b) illustrates the detection current waveforms, waveform 32 illustrating the detection current waveform when the inductance presented by the coil is small and 33 illustrating the detection current waveform when the inductance presented by the coil is large. In Figure 6(c) Vsp is the detection voltage (potential at the point x) when the inductance of the coil is small and Vsq is the detection voltage when the inductance of the coil is large. Because it is necessary for reliable detection to have a threshold potential Vth about mid-way between the maximum values of Vsp and Vsq, these maximum values must differ from one another sufficiently to enable them to be distinguished from one another if reliable detection is to be achieved.In practice, however, with a circuit as shown in Figure 5, only a small difference between voltages Vsp and Vsq is readily attainable because resistance 24 is in series with the coil when the coil is excited. For this reason, the threshold potential value Vth and the circuit elements which determine Vsp and Vsq, must comply strictly with design requirements and little tolerance is permissible. Moreover, because the difference between Vsp and Vsq is small, any comparator used to determine Vsp and Vsq in relation to Vth will of necessity have numerous circuit elements of considerable current consumption and which, in a mass-produced wristwatch, must normally be incorporated in an l.C. structure. Of course it is very- difficult to achieve close tolerances in elements, e.g. the resistance 24, incorporated in an l.C. structure.

It would be possible, in order to reduce the practical difficulties occasioned by the smallness of the difference between Vsp and Vsq to use detection pulses in both directions, positive and negative, and to compare the difference between the two detection potentials thus obtained but this would involve additional problems very difficult of satisfactory practical solution-e.g. in the handling of analog signals-necessitating the use of undesirably complex circuit structures. In short, despite the advantages offered by detection of the rotation and non-rotation condition by the method of detecting the position in which, after a driving pulse, the rotor stops, these advantages are accompanied by practical difficulties, such as those above-mentioned, which are consequent upon the smallness of the difference between Vsp and Vsq.These difficulties have imposed serious obstacles in the way of the practical use of this method, especially for mass-produced battery driven wristwatches.

This present invention seeks to avoid the foregoing difficulties and disadvantages and to enable the position which the rotor has assumed after a driving pulse has ceased to be determined readily and reliably in order to determine whether the motor is in the rotation condition or in the non-rotation condition.

A feature of this invention resides in providing arrangements whereby the difference between Vsp and Vsq is increased substantially so that reliable detection of whether the motor is in the rotation condition or not can be readily effected by a detection pulse and the width of the new driving pulse increased, if necessary, without requiring the satisfaction of close tolerances in the circuit elements or in the motor and coil dimensions-indeed of tolerances closer than those readily attainable by mass production methods and the adoption of l.C. methods of manufacture for the circuit elements including those providing detection resistance.

According to this feature of the invention there is provided a stepping motor driven electronic timepiece having automatic driving pulse width control and in which determination of whether the motor has stopped, after an applied driving pulse has ceased, in a rotation condition or in a nonrotation condition, is effected by means of a detection pulse which is supplied to the motor coil to set up, across a detection resistance, a detection voltage the magnitude of which is indicative of which condition exists, characterised in that, at the commencement of the detection pulse, the detection pulse current path extends through the coil but not through the resistance, and that, at a time after the commencement of said detection pulse, the path is changed to include the detection resistance in series with the coil.

The detection pulse current path established at the commencement of the detection pulse may be arranged to extend from one terminal of a supply source, through the coil, and back to the other terminal of said source.

Preferably the polarity of each detection pulse is the same as that of the immediately preceding driving pulse.

Preferably also the width of the detection pulse does not exceed 1.0 m sec.

Referring now to Figure 7, this illustrates the onset of current in two cases in which the motor coil is excited by a detection pulse. Curve 36 shows the onset of current when the rotor is in such a position as in Figure 3 that the magnetic flux has,to pass through restricted stator portions which are saturated or nearly so. In this case the current onset is rapid because the magnetic reluctance is large, and the inductance presented by the coil is small. Curve 37 shows the onset of detection pulse current when the rotor is in such a position (as in Figure 4) that its magnetic flux passes in the direction opposite. In this case the current increases relatively slowly and gradually up to a point, such as the point r on the curve because, up to this point, the magnetic reluctance is small and the inductance presented by the coil is large.After the point r, however, the current increases rapidly because of saturation of the saturable portions of the stator. The presence of the phenomena illustrated by Figure 7 has been verified by experiment with a stepping motor as illustrated in Figures 3 and 4 and having a stator with an inside diameter of 2.1 mm (within which the rotor is situated); a stator thickness of 0.5 mm; a minimum width 8 of the saturable portions of 0.1 mm; a rotor with an inside diameter of 1.5 mm and a thickness of 0.5 mm and a coil (7) of 10000 turns and a direct current resistance of 2.7 kQ. The supply voltage used was 1.5V.The currents ip and iq at the points p and q in Figure 7 were found to be 97 ,uA and 50 flbA respectively and the times O-Ts and O-Tr were 0.25 m sec and 0.93 m sec respectively. It will be seen, therefore, that if current is passed through the coil from a detection pulse of width (Ts) of 0.25 m sec, it will assume either of the following values in dependence upon the position of the rotor:-- ip 97 ,uA, or iq 50 ,uA. So it is possible to determine whether the rotor position is that appropriate to the rotation condition or that appropriate to the non-rotation condition by distinguishing between the above well separated values.

Referring now to Figure 8, which is a three-part figure illustrating diagrammatically and in principle, an embodiment of this feature of the invention, 7 is the motor coil, 40,41,42,43, 44, 45 are switches and 24 is a detection resistance.

In the first switching position shown in Figure 8a switches 40, 41,44 and 45 are open; 42 and 43 are closed; and there is no flow of detection current. In the second switching position shown in Figure 8b, detection current flows as indicated by the arrow-headed line 46, through the now closed switch 40, the coil 7 and the switch 43, switches 42, 44 and 45 being open. In the third switching position shown in Figure 8(c), 40, 41, 43 and 44 are open and 42 and 45 are closed and the current flow initiated when the switches were in the positions shown in Figure 1 (b) now flows through the closed loop indicated by the arrowheaded line 47 and which includes the switch 42, the coil 7, switch 45 and the detecting resistance 24, now in circuit for the first time.A potential proportional to the current now flowing appears at the "live" end "y" of resistance 24 and, as will now be appreciated, the rotor position can be determined by determining the potential at this point "y". Figure 9 illustrates the current and voltage waveforms at the point "y" at this time.

Figure 9(a) shows the detection pulse of width Ts and Figure 9(b) shows the current waveforms. In Figure 9(b), 48 is the current waveform at y if the motor is in the rotation condition and 49 is the corresponding waveform if the motor is in the non-rotation condition. The maximum current values of 48 and 49 are ip and iq respectively.

Figure 9(c) shows the corresponding potentials at the point "y", the voltage waveforms 50 and 51 corresponding with the current waveforms 48, 49 respectively. In Figure 9(c), Vsp and Vsq show respectively voltages attained in the curves 50 and 51. A detector circuit such as a comparator (not shown) having a suitable threshold potential Vth can readily distinguish between these maximum values Vsp and Vsq. Figure 8 is, as above stated, diagrammatic, the switches being shown as mechanical switches though in practice they would be electronic switches.The threshold potential Vth should comply with the following relation: Vsq < Vth < Vsp In practice the difference between the detection voltages Vsp and Vsq obtainable with an improved arrangement as explained above with the aid of Figures 7, 8 and 9 is approximately twice as great as the difference obtainable (other things being equal) between the corresponding voltages obtainable with an arrangement as hereinbefore described with the aid of Figures 5 and 6 because, with the improved arrangement, the detecting resistance (24) is not in circuit with the coil at the onset of flow of the detection current.To give a practical example, the result obtained experimentally with a particular stepping motor dimensioned as hereinbefore specified, using a detection pulse width (Ts) of 0.25 m sec; a detection resistance (24) of 1 5 kQ; and a supply voltage of 1.5 V: the value of Vsp obtained was 1.45 V and that of Vsq was 0.7 V. The difference between these values is more than twice as large as was obtained with an arrangement as described with reference to Figures 5 and 6 when using the same motor and the same values of detection resistance, detection pulse width and supply voltage.This is a great improvement from the practical point of view, allowing of the adoption of much easier tolerances in circuit elements (including the detection resistance) and as regards threshold voltage, and enabling considerably cheaper, and simpler circuitry, of less current consumption to be used for distinguishing between the comparatively widely separated values of Vsp and Vsq. For example, instead of a sensitive complex and expensive comparator, the threshold potential of an inverter could, in many cases, be utilised for distinguishing between these voltages.

With regard to the short detection pulses each of which follows a driving pulse, there are two possibilities so far as polarity is concerned. One is that each detection pulse is of the same polarity as the immediately preceding driving pulse; the other is that each detector pulse is of opposite polarity to the immediately preceding driving pulse. In the latter case the detection voltage is affected by and varied as the result of magnetic hysteresis and residual magnetic flux in the stator due to the immediately preceding driving pulse. In the former case, the detection voltage is more stable because it is not influenced by magnetic hysteresis.The avoidance of influence on the detection voltage by magnetic hysteresis, and the consequent improved stability of that voltage is clearly of substantial advantage in practice, whatever the width of the relevant driving pulse may be and whatever transient oscillations the rotor may execute after the end of the driving pulse. Moreover the better the stability the easier it is to select the width required for the next driving pulse.

It is desirable to choose a detection pulse width which is less than O--Tr in Figure 7. If the detection pulse width is more than this, it becomes more difficult to detect the difference between the voltages Vsp and Vsq because, with such a wider detection pulse, the said difference becomes smaller. With the particular stepping motor dimensioned as herein stated in the description relating to Figure 7 and with which O-Tr was found to be 0.93 m. sec it is desirable that the detection pulse width should not exceed 1.0 m. sec as a maximum. The effect of increasing the detection pulse width beyond this value is to increase the current consumption and to make it more and more difficult to obtain a satisfactorily large difference between Vsp and Vsq.

So far the description has been rather general: the driving and detection pulses have not been illustrated and no detailed description of circuitry has been given. Figure 10 illustrates the pulse waveforms applied to the motor coil and shows driving pulses and detection pulses, the latter being used for determining whether, after cessation of a driving pulse fed to the motor, it is in the rotation or in the non-rotation condition.

The pulses DD and DD' are successive driving pulses, successively of opposite polarities, and the pulses DP and DP' are detection pulses shown in the case illustrated in Figure 10, as being each of the same polarity as the immediately preceding driving pulse. It is assumed in Figure 10 that the width of the driving pulse DD was previously selected to be the optimum for the then output torque of the motor and the then load imposed on it. The following detection pulse DP is used to detect whether the motor has stopped in the rotation or in the non-rotation condition. If it is in the non-rotation condition a wider driving pulse DD" (shown dotted and following pulse DP)-a correction pulses applied to cause the motor to execute the forward step it failed to take when fed with the pulse DD.

The accompanying Figures 11 and 12 which should be read in conjunction with Figures 3 and 4 illustrate rather more clearly than Figures 3 and 4 the principles underlying determination, by a detection pulse of the condition of the motor which as before, has a rotor permanently magnetised to have two magnetic poles S and N.

In Figure 11 the rotor is assumed to be in the position shown before the drive pulse DD arrives.

When this drive pulse is applied, the coil 7 (not shown in Figures 11 and 12) is energized to produce a magnetic flux 22. If the drive pulse DD is large enough, the rotor rotates through half a revolution to the position shown in Figure 12(a).

However, if the said drive pulse is not sufficiently large, the rotor fails to rotate through the half revolution and, when the detection pulse DP arrives, will be in the position shown in Figure 1 2b. If the rotor is in the position shown in Figure 12(a) the permanent magnetic fluxes from the rotor pass from left to right through the magnetically saturable regions of the stator 1 7 formed by the recesses or notches 18a,18b.

When the coil is energized by the detection pulse DP, it generates a magnetic flux 10 which passes through the saturable regions in opposing the permanent magnetic flux there so that reduced magnetic reluctance is manifested by the stator and the motor coil therefore presents a large inductance. The detection pulse current therefore increases only gradually. If, however, the rotor is in the position shown in Figure 12(b) the relations between the stator flux produced by the detection pulse and the permanent rotor fluxes are such that they aid one another in the saturable portions of the stator, the magnetic reluctance manifested by the stator is large, the inductance presented by the coil is small and the detection pulse current rises rapidly.Figure 12(a) illustrates what happens when the motor is in the rotation condition while Figure 1 2b illustrates the flux relations when the motor is in the non-rotation condition. Determination of the difference between the rate of detection pulse current growth present when the rotation condition exists from that present when the non-rotation exists provides a basis for determining which condition exists.

Refer now to Figure 13 which shows, in a diagrammatic manner similar to that adopted in Figures 5 and 8, a circuit for utilizing the foregoing principles to detect whether the motor is in the rotation or in the non-rotation condition when a detection pulse arrives. In Figure 1 3, 25, 26 are p-channel transistors and 27, 28, 29 and 30 are n-channel transistors. There are two similar detection resistances 24, 24' connected as shown and of value R,, when a detection pulse (of width designated P5 in Figure 20a) appears, current flows initially along a loop L, the transistors 25 and 28 initially are turned OFF and at the same time the transistors 27 and 30 are turned ON. This causes the detection pulse current now to flow through the detection resistance 24' producing across it a voltage proportional to the magnitude of the current flowing therethrough. Figure 14(b) shows potential waveforms produced at the point 02 at this time. Curve 26 shows the varying voltage produced if the motor is in the non-rotation condition and curve 27 shows the varying voltage produced if the motor is in the rotation condition.

Figure 14(a) is a diagram of the corresponding detection currents which have peak values of iu and ir if the detection voltages have peak values of Vu and Vr respectively. These peak values have the following relationships:

Vu6,Rs x iu and (1) Vr=Rs x ir where Rs is the resistance of a detection resistor.

Accordingly, it can be determined whether the rotor is in the rotatable condition or not by determining whether the peak value of the detection voltage is larger or smaller than a reference potential Vth by means of a voltage comparing device such for example as a comparator. The rapid rise of current over the curve portion 24 and the slower rise over the curve portion 25 will be noted.

A simplified block diagram of a timepiece capable of operating with automatic driving pulse width control and in which detection of the rotation and non-rotation conditions of the motor in accordance with the principles so far described is provided by Figure 15. Here 135 is a time-base relatively high frequency piezo-electric crystal controlled oscillator, 136 is a multi-stage frequency divider driven thereby, 137 is a pulse synthesiser producing the various required pulses of the required widths, 1 38 is a controller, 1 39 is a driver and detector and M is the stepping motor.

The output from the oscillator, for example of 32768 Hz, is divided down to 1/2 Hz (for example) by the frequency divider 1 36. The pulse synthesiser 137 makes use of signals taken from various points in the frequency divider to form pulse waveforms S40 to S44 as shown in Figure 1 6 and feed them over the connections so referenced in Figure 1 5. The oscillator, frequency divider, and pulse synthesiser may all be as known per se and need not be described here.

They will normally be constructed of logic elements. Figure 17 shows a circuit arrangement which could be used as the controller 1 38. Figure 1 8 shows a circuit which could be used for the driver and detector 139, and Figure 1 9 is a timing chart for signals produced in the controller and in the driver and detector.

Figure 1 6 shows the pulse waveforms produced by the pulse synthesiser 1 38. S40 is the 1/2 Hz signal from the divider; S41 is a drive pulse signal with drive pulses 1 53-a, 1 53-b of pulse width P1 for use in normal operation of the timepiece (i.e. when the calendar is not being changed and the motor load can be expected to be light).Drive pulse width control is effected by signals S56, S57 which provide information indicative of whether the motor is in the rotation condition or not, and ensure that the width of the drive pulses delivered at any time will be suited to the prevailing circumstances-mainly the load imposed on the motor. S42 is a detection pulse signal having detection pulses 154-a, 1 54-b of a pulse width Ps. S43 is a signal providing detection zones 1 55-a, 1 55-b. And S44 is a signal having correction pulses 1 56-a, 1 56-b of a pulse width P2 greater than P1.

As shown in Figure 18, the driver and detector 139 comprises p-channel transistors 1 62, 1 63 and n-channel transistors 164,165 forming a motor driver; n-channel transistors 1 66, 1 67 for switching the detection resistor circuits; and comparators 1 72, 1 73 for producing an output signal of HIGH logic level when the potential at the point O1 (or 2) is larger than a reference potential Vth developed by voltage division by resistors 1 70, 1 71, or an output of LOW logic level when the potential at O1 (or 2) is smaller than the reference potential Vth.The points O1 and O2 are at the opposite ends of the motor coil 7.

The controller 138 produces signals S50 to S55 at the terminals so referenced for supply to the driver and detector as determined by the signals S56, S57 carrying information indicative of whether or not the motor is in the rotation condition and by the signals S40 to S44 produced by the pulse synthesiser 137.

Operation of the controller shown in Figure 1 7 will now be described with reference to the timing charts of Figures 1 6 and 1 9. Referring first to Figure 17, the output of an OR gate 148 becomes HIGH when it is supplied with a pulse 153-a of width P1 in the signal S41. At this time, the signal S40 is HIGH and hence an AND gate 150 opens, causing a NOT gate 1 57 to produce an output of LOW level. The signal S53 from NOT gate 158 also becomes LOW because of the signal received by 158 through an OR gate 1 55 and the AND gate 150.The signal S40 is HIGH and one of the inputs to AND gate 1 51 is LOW so that the pulse 153-a in the signal S41 cannot pass the AND gate 151. Thus, the signal S50 goes HIGH, as does the signal S52 whereupon a driving pulse of width P1 is applied to the motor coil. The detection pulse Ps in the signal S42 follows the pulse P1. Because the signals S41, S42, S43, S44 are all LOW during the interval between the pulses P1 and Ps, the signals S50, S51, S52, S53 all become HIGH. When the detection pulse 154-a in signal S42 appears, signal S50 becomes HIGH, signal S51 becomes LOW, signal S52 becomes HIGH, and signal S53 becomes LOW, and the pulse Ps is fed to the motor coil.Then, when the pulse 155-a in signal S43 arrives, AND gate 1 53 opens because signal S40 is HIGH, and signal S53 becomes LOW. Since AND gate 1 54 is closed, signal S52 becomes HIGH and detection of whether the motor is in the rotation condition or not is effected.

Delivery of the relatively wide correction pulse P2 in the signal S44 depends on whether the motor is in the rotation condition or not. If the motor is in the non-rotation condition, a pulse 1 76 in the signal S56 is applied in the detection interval, and a flip-flop consisting of NOR gates 140, 141, and a NOT gate 144 latches and produces an output signal S58 at HIGH logic level. This causes AND gate 146 to open and allow the pulse P2 in the signal S44 to pass through said AND gate 146. The signals S51, S53 become LOW and the signals S50, S52 become HIGH and the correction pulse P2 is applied to the coil.

If, on the other hand, the motor is in the rotation condition, signal S56 remains LOW during the detection interval and hence signal S58 remains LOW. Accordingly AND gate 146 remains closed, thus blocking passage therethrough of the correction pulse P2 in the signal S44. Therefore, no correction pulse is delivered.

In a timepiece constructed and operating as so far described with reference to Figure 10 to 19, the peak values vu, vr of the detection voltages are dependent on the detection resistance value Rs. Since differences in value of detection resistance will result in difference in value of the detection voltage produced it would be necessary to make the resistances 24 accurately to a predetermined design value and only very close tolerances would be permissible. In practice, it is desirable to incorporate the detection resistances in an I.C. structure and to make them by a method of P- diffusion, P+ diffusion, ion implantation, or the like in order to meet the onerous practical requirements in a timepiece-especially in a wrist watch-as regards smallness of size, thinness, and low manufacturing cost.However, it is impossible to make resistance by I.C. methods with the closeness of tolerance required, for resistors so made are subject to substantial variations in value in dependence upon manufacturing conditions. For example resistances manufactured by P- diffusion may vary in value over a range of about +100%, and even resistances manufactured by ion implantation may vary in value over a range of +20% or more.

The use of ordinary separately made detection resistances, external to an I.C. structure and connected thereto by leads is objectionable because such use is inconsistent with the satisfaction of requirements as regards smallness of size, thinness and low cost of manufacture.

There are also onerous requirements as regards permissible tolerances in the manufacture of the motor coil to specification and in the manufacture of the stator and rotor to specified mechanical dimensions, for departures from specification in these respects will affect the detection voltage as indicated by equation (1) because the detection resistances are of fixed value Rs. Figure 20 illustrates this. If, for some reason, the peak values of detection current were to be changed from iu to iu' and from ir to ir as shown in Figure 20(a), the-peak values of detection voltage would also change from Vu to Vu' and from Vr to Vr' as shown in Figure 20(b), and in this case the voltage Vu' when compared with the reference potential Vth might give a wrong indication of the condition in The motor.

Although the above example is:a rather extreme one and perhaps unlikely to be-encountered in practice, it does indicate the extent to which variations in detection currents due to.

departures from design specificatfons can make determination of whether the motor is in the rotation condition or not a more delicate and critical matter and more liable to error.

Again the specifications of timepiece movements for different timepieces may differ from one another as do, for example, those of watches for use by men from those for watches for use by women. Stepping motors in watches for men generally have different mechanical dimensions from those in watches for use by women. If, as is the case with a watch as so far described with reference to Figures 10 to 19, the value of the detection resistance has to be selected to suit the stepping motor employed, this imposes upon the manufacturer of a range of watches, severe and undesirable limitations as regards standardisation.

The object of a second feature of this invention, like the object of the first feature hereinbefore set forth, is also to achieve a satisfactorily wide difference, in a stepping motor driven electronic timepiece having automatic driving pulse width control, between the motor condition determining detection voltage obtained if the motor stops in the rotation condition after a driving pulse and the detection voltage obtained if the motor stops in the non-rotation condition after a driving pulse, and to achieve this without requiring the satisfaction of close tolerances in the circuit elements or in the motor and coil dimensions.The said second feature of invention, enables the watch manufacturer satisfactorily to use detection resistances made by i.C. methods, despite the far from close tolerances which such methods involve, and to accept, as regards the stepping motor and its coil, such easy tolerances that the same circuit structures may even be used in different watch models having different motors e.g. in watches for men and watches for women.

According to the second feature of this invention a battery powered stepping motor driven electronic timepiece having automatic driving pulse width control and in which determination of whether the motor has stopped, after an applied driving pulse has ceased, in a rotation condition or in a non-rotation condition is effected by means of a condition determining detection pulse which is supplied to the motor coil to set up, across a detection resistance, a detection voltage the magnitude of which is indicative of which condition exists is characterized in that said detection resistance is composed of a plurality of selectable resistor elements so that any of a plurality of values of detection resistance can be presented and further characterised by the provision of means providing a zone during which selection of said elements is effected by means of detection resistance determining detection pulses which successively change the elements selected and thereby change the value of detection resistance presented until a value is established at which the voltage produced by such a pulse reaches a predetermined threshold.

The zone may be established upon switching on the timepiece actuating battery or upon releasing the timepiece from time setting operation.

Preferably the arrangement is such that the value of detection resistance established is established within one second after time base oscillation commences in the timepiece as the result of switching on the battery or within one second of release of the timepiece from a timesetting operation.

The change of the elements selected may be effected by successively increasing in steps the number of elements effectively in series in said detection resistance or by decreasing said number in steps. In this case, preferably, the values of the individual elements are in binary relationship 1,2, 4,8...

Figure 21 shows a preferred driver and detector circuit which offers considerable advantages over that above described with reference to Figure 1 8. Referring to Figure 21, 135 and 136 are P-channel transistors, 137, 138, 139, 140 are N-channel transistors and instead of the fixed resistors 24 and 24' of Figure 18, there is provided a plurality of resistor elements 149 to 1 56 which are fabricated on an IC structure and have values indicated by the legends r, to r4. 141 to 148 are transmission gates by means of which the total value of detection resistance between points 0, and O,' and between points 02 and 0,' can be varied. The control terminals of these gates are referenced S, to S4.The arrowed line 133 indicates the path at first established for the detection current immediately a detection pulse appears, and 134 indicates the path which includes the detection resistance and is established later.

The relationship between signals supplied to the control terminals S, to S4 of the transmission gates and the value of detection resistance Rs connected between the points O, and 0,' and between the points'02 and 02' can be expressed by: Rs=51r +52r2+32r3+34r4 (2) if the resistances of the transmission gates themselves, when energized, are regarded as being negligible. When the control terminal (for example S,) of a gate is O (LOW logic level), the gate is turned OFF and the associated resistor element (for example of value r,) is effectively in circuit and contributes to the value of Rs. When the said control terminal is 1 (HIGH logic level), the transmission gate is turned ON and the said resistor element is effectively short circuited and does not so contribute.While it would be possible to provide for different values of detection resistance between the points 0, and 0,' and between the points 02 and 02', there is no appreciable advantage in so doing and the following description is based on the assumption that the values of detection resistance established between points 0, and 0,' are always the same as those between the points 02 and O2'.

There are various ways of choosing the resistance values r,, r2, r3, r4. In the arrangement now being described the following relationships are adopted: r4=2r3=4r2=8r, (3) With these relationships the detection resistance Rs available can be varied in steps of equal increments from 0 to (r,+r2+r3+r4). The optimum value of detection resistance Rs, in any particular case, is that in which the peak value Vr of detection voltage when the motor is in the rotation condition differs most widely from the peak value vu when the motor is in the non, rotation condition. Therefore, the value of detection resistance Rs should be so chosen that the peak voltage Vu is substantially equal to the power supply voltage (VDD).

With the foregoing presupposed, assume that the optimum detection resistance value Rs, making the peak voltage vu equal to VDD is 15 kQ.

On this assumption, the l.C. resistor elements 149 to 1 56 should be such that (r,+r2+r3+r4) is always 1 5 kQ or more when one takes into account the variations in resistance values to be expected in l.C. fabricated resistors.

Now assume the fabrication of I.C. resistor elements providing a detection resistance in the range 1 5 kQ to 30 kQ which is practically feasible by currently available IC fabrication methods. (In the case of resistors made by ion-implantation, it is practically feasible, with current methods, to achieve a smaller range of ~20%). Consideration will now be given to establishing a detection resistance value Rs in which r,+r2+r3+r4=30 kQ under the worst conditions.When the respective resistance values satisfy equation (3), r,=2 kQ, r2=4 kQ, r3=8 kQ, and r4=1 6 kQ. The relationships between the signals at the control terminals S1, S2, S3, S4 are given in Table 1, in which the detection resistance value Rs is shown as available in a range of from 0 kQ to 30 kQ in increments of 2 kS2.

Table 1

Detection Control signal resistor S4 53 52 5r Rs 11101010 kQ 1 1 1 1 2 1 1 0 0 6 1 0 0 0 14 O 1 1 1 16 0 0 0 1 28 0 0 0 0 . 30 The assumed "ideal" resistance is 1 5 kS2, and the resistance 14 kQ and 16 kS2 shown in Table 1, is close enough to this. As will be seen from the table, a resistance of 1 6 kQ can be established by making the control terminals S1, S2, S3, and S4 respectively LOW, HIGH, HIGH and HIGH.

Figure 22 is a timing chart showing the waveforms of signals at the gate terminals a, b, c, d, e, f of the transistors 135 to 140 and the control terminals S1, S2, S3, S4 of the transmission gates 141 to 148 in Figure 21. Interval A in Figure 22 is a zone in which the value of the detection resistance Rs, best suited to a particular individual stepping motor is established.

Subsequent to zone A is the normal operation period in which the motor is driven by driving pulses of width automatically varied to suit the motor load and other prevailing circumstances.

This normal operation has been fully described hereinbefore and need not, therefore, be described again here. Interval A commences immediately after the power supply battery of the timepiece has been switched on or the timepiece has been released after a time re-setting operation.

Pi1, Pi2 within the zone A of Figure 22 are relatively wide pulses (hereinafter called "initialization pulses"): Pe is a demagnetization pulse for controlling magnetic hysteresis in the stator due to application of an initialization pulse: Ps, Ps1, Ps2, Pus,... Psn~,, Psn are detection pulses for use in establishing the required detection resistance value Rs. Pulse widths successfully adopted experimentally were: Pi,=Pi,=6.8 msec, Pe=0.7 msec, Ps, Pisa, ..... . Psn=0.36 msec.

The purposes which the initialization pulses pi1, Pi2, the demagnetization pulse Pe, and the detection pulses Ps, Ps, . . . Psn serve will be described with reference to a typical magnetic hysteresis curve, shown in Figure 23, for the saturable regions of a stepping motor stator. In Figure 23, Ho and -Ho are the intensities of the permanent magnetic field produced by the rotor of the motor in a saturable region of the stator when the rotor is in a stationary stable position.

Assume that the magnetic poles of the rotor are positioned as shown in Figure 24 before the initialization pulse Pir is applied. If the arrow 266 in Figure 24 is regarded as defining the positive direction of the magnetic field, the saturable regions are subjected to a magnetic field of -Ho, taken on a line x'-y'. Which point on the line x'--y' is taken is dependent on the magnetic hysteresis.

Assume that the position x' is taken prior to application of the initialization pulse Pi,. When the initialization pulse Pi, is applied, a magnetic flux 268, as shown in Figure 25 is produced in a direction to rotate the rotor. Since Pi, is a wide pulse, the rotor is caused to rotate to the position illustrated in Figure 26. At this time, the magnetic hysteresis curve of Figure 23 is followed as indicated by the arrows 269 until a point on a line x-y is reached. Which position on the line x-y is taken depends on the magnitude of transient vibrations produced when the rotor rotates. Figure 27 shows the waveforms of currents flowing through a motor coil upon application of the pulse Pi,.If, as shown in Figure 27(a) the time Pi, following which relatively large currents are induced in the motor coil by transient rotor vibrations is relatively short, as illustrated in Figure 27(a), a point close to the point on the magnetic hysteresis curve is taken. Conversely, as shown in Figure 27(b), if the time Pi is relatively long and only relatively small currents are induced in the coil due to transient vibrations of the rotor, the point taken will be closer to the point y. Since the initialization pulse applied is a wide one in order to bring the rotor reliably to a desired position, a point fairly close to the point x will in all probability be taken.

The preceding description is based on the assumption that the rotor is positioned as shown in Figure 24 prior to application of the initialization pulse Pi1, and the magnetic fluxes due to application of the initialization pulse Pia are directed as illustrated in Figure 25, with the rotor being rotated by the initialization pulse Pi1. Since, however, it is necessary to prevent movement of the hands of a timepiece in the second immediately after it has been released from a time resetting operation, it should be arranged that current produced in the coil by the initialization pulse Pi1 should flow in the same direction at that in which current flowed just before resetting, if the zone in which the value of the detection resistance Rs is established is to follow just after the watch has been released from resetting.In this case (establishment of Rs after resetting) the pulse Pi, should be applied in a direction to attract back the rotor, instead of rotating it. The point x on the magnetic hysteresis curve of Figure 23 is taken both prior to and subsequent to application of the pulse Pi,. At any rate, the point x on the magnetic hysteresis curve is taken after the pulse Pi, has been supplied.

The action of the demagnetization pulse Pe will now be described. As shown in Figure 22, the demagnetization pulse Pe is applied in a direction opposite to that in which the initialization pulse Pi1 is applied. Figure 28 shows a magnetic flux 270 generated by the demagnetization pulse Pe and directed in the positive direction. The width of the demagnetization pulse Pe is too small (for example, 0.7 msec.) to rotate the rotor, which thus remains in the position shown in Figure 29.

At this time, the magnetic hysteresis curve of Figure 23 is followed from the point x in the direction of the arrows 271 to the point y.

The operation of the detection pulses Pus1, Pus,... Psn will now be described. These detection pulses Ps" Pus1, . .2... Psn are applied, as shown in Figure 22 in the direction in which the demagnetization pulse Pe are applied. Figure 30 shows the position of the rotor at this time, and the direction of the magnetic flux 272 produced by these detection pulses, the said direction being positive.The magnetic hysteresis curve of Figure 23 is followed as indicated by the arrow 273 from the point back to the point. Since the magnetic permeability ,u=dB/dH is small and the magnetic reluctance is large at the saturable regions of the stator, the inductance presented by the motor coil is small and the current generated by the detection pulses increases sharply.

The operation of the second initialization pulse Pi2 in zone A" (see Figure 22) will now be described. Figure 31 shows the position of the rotor when the initialization pulse Pi2 is applied, and the magnetic flux 274 generated by the pulse Pi2. Since the initialization pulse Pi2 is relatively wide (for example, the pulse width may be 6.8 msec), the rotor will certainly be caused to rotate to the position shown in Figure 32. At this time, the magnetic hysteresis curve of Figure 23 is followed as indicated by the arrows 275 to the point x'.

The operation of the detection pulse Ps in the zone A' will now be described. Figure 33 shows the position of the rotor when the detection pulse Ps is applied, and also the magnetic flux 277 produced by it. At this time, a minor hysteresis loop as indicated by the arrows 276 is followed from and to the point x'.

The operation of the detection pulse Ps in the zone A" will now be described. Figure 33 shows the position of the rotor when the detection pulse Ps is applied, and also the magnetic flux 277 produced by it. At this time, a minor hysteresis loop as indicated by the arrows 276 is followed from and to the point x'. As the magnetic permeability,u is large and the magnetic reluctance is small, the inductance presented by the motor coil is large so that the detection pulse current rises only slowly.

The way in which the value of the detection resistance Rs is established during the zone A will now be described with the aid of the timing chart of Figure 22.

When the detection pulse Ps1 is applied, the control terminals S1, S2, S3, and S4 (see Figure 21) of the transmission gates are at logic levels LOW, HIGH, HIGH and HIGH respectively, the resistor elements r1 are effectively in circuit and Rs is therefore equal to r1. Detection pulse current generated by the pulse flows in the loop 1 33 shown in Figure 21. After this current flows in the path 1 34 including the detection resistor and a voltage proportional to the magnitude of the current is developed at one end 02 of the coil 7.

The voltage thus generated is shown at 357 in line 02 of Figure 22. The detection voltage 257 has a peak value Vsi=Juxr1 where iu is the peak value of the detection current. When the second detection pulse Ps2 is applied, the control terminals S,, S2, S3, and S4 become HIGH, LOW, HIGH, and HIGH, respectively, whereupon the value of the detection resistance Rs becomes equal to r2 (=2r1). At this time, the detection voltage, indicated at 358 in line 02 of Figure 22 has a peak value Vs2=.iuxr2. Each time a detection pulse is applied, the value of the detection resistance R5 is increased stepwise, with the result that the detection voltages as indicated at 357, 358, 359 362, 363 increase in proportion.This process of step-by-step increase of the value of Rs continues until the detecting voltage reaches a peak-363 in Figure 22-at which Vsn > V'th where Vsn is the peak and V'th is a reference potential. By selecting Vth' to be equal or near to the power supply voltage VDD the value of Rs can be so established that the difference between the rotation condition determining detection voltages Vu, Vr generated, in normal operation of the timepiece, by a detection pulse Ps and indicative of whether the motor is in the rotation condition or not becomes large thus facilitating determination of which condition exists.The value of Rs for which one of the detection voltages 357, 358, 359 first exceeds the reference potential Vth' (6.VCD) is the value best suited to the characteristics of the particular stepping motor in the timepiece. Figure 34 shows how the voltage at the terminal Oi, incrementally increases as the value of the detection resistance R5 is increased in steps. In Figure 34 the voltage Vsn is the first voltage to exceed the reference potential (Vth'=.VDD), and the value of R5 which produces voltage Vsn is selected as the optimum value.

Operation in the zone A" of Figure 22 for establishing the best value of Rs will now be described with reference to that figure. The zone A" is that in which it is ascertained whether the value of R5 established in zone A' is appropriate for zone A" or not. As already stated, the second initialization pulse Pi2 is a wide one-certainly wide enough to cause the rotor to rotate.

Therefore the detection current produced by the detection pulse Ps will increase gradually. When this detection current flows through the detection resistance Rs established in the zone A', a detection voltage appears as a waveform having a small peak value 364 as shown in Figure 22.

Figure 35 shows the voltage waveform 364 drawn to an enlarged scale. If the peak value Vr of the detection voltage 364 is smaller than the reference potential Vth, the value of Rs detection resistor already selected in zone A' is suitable.

(The voltage waveform 363 shown in broken lines in Figure 35 is the waveform of a detection voltage generated by the detection pulse Psn in the zone A').

Circuitry for automatically establishing the best values for R5 will now be described. Figure 36 shows a circuit for producing a masking signal in a detection resistor establishing or setting zone; Figure 37 shows a circuit for generating detection signals; Figure 38 shows a circuit for establishing or setting a detection resistor; and Figure 39 shows a circuit for comparing detection voltages at ,, 02 with the reference potential. Figure 40 is a timing chart explanatory of the operation of the circuit shown in Figure 36, and Figure 41 is a timing chart explanatory of the operation of the circuit shown in Figure 37.

Referring to Figure 36, 488 is a NOT circuit, and 489 and 490 are half-latch circuits with reset terminals. (A half-latch circuit is a circuit which allows data to pass when an applied clock signal-at Cl-is HIGH and to be held when said clock signal is LOW). 491 is a NAND gate; 492 is an OR gate; and 493 is another AND gate. Signals are indicated in Figure 36 by like references to those in the timing chart in Figure 40.At S7 is a signal which goes HIGH when the power supply is switched on and upon restting; at S8 is a signal which becomes HIGH when the detection voltage at the point O, or 2 is equal to the reference voltage; at Sg is a master signal which is supplied from a suitable point in the frequency divider following the time base oscillator of the timepiece; S,O is another master signal obtained from the frequency divider;S22 is a signal obtained by delaying the signal S7; S24 is a signal obtained by delaying the signal S22; and S23 is the clock signal. S25 is a signal for determining a zone for automatically establishing a value for R When the signal S25 is LOW, the circuit arrangement of Figure 36 comes into an automatic resistance establishing mode of operation.The signal S8 for determining the level of the detection voltage becomes HIGH when the voltage at Oi or 2 is greater than the reference potential. S" is a signal which combines the signals S25 and S8. When the signal S8 becomes HIGH, the signal S11 also becomes HIGH whereupon a value for R5 is established.

Referring now to Figure 37, 494 and 496 are NOT circuits; 495 is an AND gate; 497 and 498 are NAND gates; 499 is a NOR gate; 501 and 502 are OR gates; and 500 is a half-latch circuit.

Signals are denoted by the same reference characters as those used in the timing chart of Figure 41. Ss is a count-up signal for a counter in the establishment of values for R5; S6 is a sampling signal for use in detecting the value at which the detection resistance R5 is established; S15 is a current output signal for use in detecting the value at which R5 is established; S16 is a detection zone signal; S12 is a current setting signal for use in detecting the value at which R5 is established;; S,3 is period setting signal for use in detecting the value at which the detection resistance R5 is established; and S14 is a zone setting signal for use in detecting the setting of the detection signal.

Referring to Figure 38, 503 is a NOT circuit; 504, 505, 506 and 507 are frequency-divider circuits for producing Q outputs which change at the trailing edges of a clock signal, and S1, S2, S3, S4 are control signals for control of the resistance elements in the detection resistance.

Referring to Figure 39,508 is a p-channel MOS transistor; 509, 51 0 are resistors for producing a reference voltage; 511 is a p-channel transistor: 512 and 513 are NOT circuits; 514 is an OR gate; 51 5 and 520 are AND gates; 516, 517,518 and 519 are NOR gates cross connected in known manner to constitute two R5 latches; and 521 and 522 are comparator circuits. At S17 is a reset signal; at Sr8 is a rotation detecting signal; at S,g is a rotation detecting zone signal; at S20 is a signal from the terminal Oi, and at S2, is a signal from the terminal 02.

When the power supply is switched on or time setting of the timepiece occurs, the signal S7 becomes HIGH. At this time, the counter for setting the detection resistor is reset, with the result that S1, S2, S3 and 84 are all HIGH. (In accordance with normal logic nomenclature, 1 denotes HIGH level and 0 denotes LOW level).

When oscillation of the time base oscillator of the watch starts or the watch is released from resetting, the signal S7 becomes LOW. At the same time, the signals b, d (see Figures 21 and 22) become LOW causing a current to flow from point 01 to 03 for forced determination of the position of the rotor. This current flow constitutes the pulse Pi, shown in Figure 22. The current may flow either from the point Or to the point 02 or from the point 02 to the point O, when the power supply is switched on.However, when the watch is released from resetting, the current should flow in the direction in which it flowed just before releasing the watch from resetting, in order to prevent movement of the hands immediately after the watch has been released from resetting. The demagnetization pulse Pe is then applied in a direction opposite to that of the current produced by the drive pulse Pi1 in order to demagnetize the stator. Signal S" now becomes LOW in order to initiate a mode for automatically setting the value of the detection resistance R5. Signal Ss goes LOW and the detection resistor setting counter produces outputs: S=O, S2=1, S3=1, S4=l . At this time, the smallest detection resistor element is put in circuit.Signal S16 goes HIGH, and the pchannel transistor 511 is turned ON and the comparators receive a reference voltage of VDD.

Simultaneously, the signal S6 becomes LOW to cause a current as at 133 (see Figure 21) in the same direction as that in which the pulse Pe was applied. This current constitutes the pulse Ps, shown in Figure 22. When the signal S6 goes HIGH, the signal Sis goes LOW and the signal at a in Figure 21, is LOW, whereupon the n-channel transistor 38 is de-energized, and a detection voltage (Vs, of Figure 34) is delivered from the point 02 to the comparator 522 (Figure 39). Since R5 has its lowest value at this time, the detection voltage is lowest and, as it is smaller than Vth'(=.Vou), the comparator 522 produces a LOW output signal.Signal Sis becomes HIGH and the first step in the process of automatically setting R5 is completed.

When the signal S13 goes HIGH and then LOW, the detection resistor is checked in a process similar to the foregoing. When the detection voltage is smaller than the reference voltage Vth', the next step of detection resistance setting is checked. R5 is successively changed in stepwise manner until the detection voltage becomes greater than the reference voltage Vth'. When the comparator 522 finds the detection voltage to be larger than Vth', its output signal becomes HIGH and reaches the NOR gate 517, making the signal S8 high. The R5 latch circuit composed of the NOR gates 516 and 517 has been reset by the signal S7 which became HIGH when the power supply was switched on or when time resetting occurred.

When the signal S8 goes HIGH so does the signal S" setting the detection resistor. When signal S" goes HIGH so does signal Ss thereby inhibiting a count-up pulse for the detection resistor setting counter. When the signal S,6 goes LOW, application of the reference voltage for comparison is prevented, and the flow of detection current and detection sampling are also prevented.

Once the value of R5 is finally automatically set, it will remain unchanged unless the power supply is switched on again or the watch hands are again reset. Automatic final setting of the value of Rs is completed within one second after time base oscillation has started upon switching on the power supply or after a time resetting operation on the watch has been released. The value of Rs thus established is confirmed in one second. More specifically, a current is caused to flow from the point 0, to the point 03 to rotate the rotor one second after time base oscillation has begun upon turning on the power supply or after releasing the watch from a resetting operation.Current should flow from point 02 to the point O, if the pulse Pi, was formed by current flowing from the point O1 to the point 02. This current produces the pulse Pi2 (see Figure 22).

The pulse Pi2 causes the rotor to rotate. A condition detecting current is caused to flow in the same direction as that in which the current for the pulse Pi2 flowed, thereby detecting the condition of the rotor.

Referring again to Figure 39, when signal S19 goes HIGH, p-channel transistor 508 conducts causing a current to flow through the resistors 509, 510. The power supply voltage is divided by these two resistors 'acting as a potentiometer and the reference voltage Vth is applied to both the comparators 521 and 522. At the same time, the signals at a and c in Figure 21 become LOW to allow detection current to flow. The signals at a and c become HIGH, and simultaneously the signal at d goes LOW, whereupon detection voltage is delivered from the point 02 to the comparator 522. Since the rotor rotates at this time, the peak value of the detection voltage will normally be below the reference potential Vth.

The R5 latch circuit composed of the NOR gates 518 and 51 9 has been reset in advance by the HIGH signal S17 Therefore, the signal at S,8 remains LOW. The automatically established value of R5 resistor is now deemed correct and the watch enters at once into its normal mode of operation from the next movement of the hands onwards. If, on the other hand, the peak value of the detection voltage is higher than the reference potential Vth while the motor is in the rotation condition, the output of the comparator 522 goes HIGH, and the signal S,8 also goes HIGH.At this time, the automatic setting of R5 is deemed inappropriate, and the hands of the watch are prevented from moving, whereupon the user of the watch is made aware of the fact that the detection resistor has been set incorrectly. The user can obtain reliable correct automatic setting of Rs merely by resetting the watch.

As described above, the process of setting an optimum value of R5 best suited to the characteristics of the particular stepping motor provided in a watch is carried out during the detection resistor setting zone A. The value of detection resistor thus established remains during normal operation of the watch subsequent to zone A.

Figure 42 shows the detection voltage in the normal operation. Curve 623 shows the detection voltage produced when the motor is in the nonrotation condition, the peak value Vu being equal to the detection voltage Vsn obtained upon setting the value of R5. Curve 624 shows the detection voltage produced when the motor is in the rotation condition, Vr being the peak value.

The peak values Vu and Vr are compared with the reference potential Vth to decide whether or not the next drive pulse must be wider than the preceding one in order to keep the motor rotating correctly.

Although in the foregoing description an optimum value of detection resistance is reached by increasing R5 in steps, an optimum value can equally well be reached by an opposite procedure i.e. by reducing R5 in steps from a pre-determined maximum value. Figure 43 illustrates this sufficiently for an understanding of this procedure having regard to the description already given.

Figure 43 shows changes in the detection voltage obtained if this procedure is adopted. In Figure 43 the detection voltage changes as shown by curves 725, 726... 730,731 as R5 is reduced from its maximum. Vc is a clipped or limited voltage obtainable by using the diode characteristics of a P gate. The peak value of the detection voltage is limited by the voltage Vc. The first detection voltage to have a peak value below the reference potential Vth' (=.VDD) has a waveform as shown by 731. The value of R5 which gives this voltage waveform may be established as the detection resistance, or the value of R5 which results in the next lower detection voltage 730 (having a peak value Vsn~,), may be established as the detection resistor. . and so on.

While in the above description there are four values r,, r2, r3, r4 of series resistor elements employed (see Figure 21) any number of such elements in series may be used. The greater the number of such elements provided, the higher the precision attainable. Again, although selection of the resistor elements included in circuit is effected in Figure 21, by transmission gates in parallel with the individual elements, other arrangements capable of control by logic processing may be used for the purpose.

Figure 44 shows another arrangement which could be used instead of that shown in Figure 21.

In Figure 44 the detection resistor elements r,, r2, r3, r4 are connected in series with P gates 832, 833 coupled to the power supply terminal VDD.

From the standpoint of logic processing the circuit of Figure 44 operates similarly to that of Figure 21.

The practical advantages (especially from the viewpoint of ease and cheapness of manufacture by mass production methods and standardisation in manufacture by makers producing different models of watch with differently dimensioned motors in them) of using, instead of detection resistances of fixed value, detection resistances presenting a variable value which is automatically varied by a logic control process so as to be best suited to a particular watch, are very great indeed.

The resistance elements providing the detection resistance value do not have to be made to close tolerances; detection resistance elements made by IC methods and incorporated in the IC structure of the watch can be employed without difficulty; and the same wide tolerance detection resistance elements may be used even in watches having stepping motors made to different specifications including specification of mechanical dimensions and of coil resistance.

Moreover these advantages are obtained without involving any additions to the watch circuitry other than inexpensive and easily manufactured digital circuits which do not call for close tolerances.

Claims (13)

Claims

1. A stepping motor driven electronic timepiece having automatic driving pulse width control and in which determination of whether the motor has stopped, after an applied driving pulse has ceased, in a rotation condition or in a nonrotation condition, is effected by means of a detection pulse which is supplied to the motor coil to set up, across a detection resistance, a detection voltage the magnitude of which is indicative of which conditions exists, characterised in that, at the commencement of the detection pulse, the detection pulse current path extends through the coil but not through the resistance, and that, at a time after the commencement of said detection pulse, the path is changed to include the detection resistance in series with the coil.

2. A timepiece as claimed in claim 1 wherein the detection pulse current path established at the commencement of the detection pulse may be arranged to extend from one terminal of a supply source, through the coil, and back to the other terminal of said source.

3. A timepiece as claimed in claim 1 or 2 wherein the polarity of each detection pulse is the same as that of the immediately preceding driving pulse.

4. A timepiece as claimed in any of claims 1 to 3 wherein the width of the detection pulse is chosen at a value not exceeding 1.0 m. sec.

5. A battery powered stepping motor driven electronic timepiece having automatic driving pulse width control and in which determination of whether the motor has stopped, after an applied driving pulse has ceased, in a rotation condition or in a non-rotation condition is effected by means of a condition determining detection pulse which is supplied to the motor coil to set up, across a detection resistance, a detection voltage the magnitude of which is indicative of which condition exists characterised in that said detection resistance is composed of a plurality of selectable resistor elements so that any of a plurality of values of detection resistance can be presented and further characterised by the provision of means providing a zone during which selection of said elements is effected by means of detection resistance determining detection pulses which successively change the elements selected and thereby change the value of detection resistance presented until a value is established at which the voltage produced by such a pulse reaches a predetermined threshold.

6. A timepiece as claimed in claim 5 wherein the zone is established upon switching on the timepiece actuating battery or upon releasing the timepiece from a time setting operation.

7. A timepiece as claimed in claim 5 or 6 wherein the value of detection resistance established is established within one second after time base oscillation commences in the timepiece as the result of switching on the battery or within one second of release of the timepiece from a time-setting operation.

8. A timepiece as claimed in any of claims 5 to 7 wherein the change of the elements selected is effected by successively increasing in steps the number of elements effectively in series in said detection resistance or by decreasing said number in steps.

9. A timepiece as claimed in claim 8 wherein the values of the individual elements are in binary relation.

1 0. A battery powered stepping motor driven analogue electronic timepiece having automatic driving pulse width control and including a time base oscillator; a frequency divider driven thereby; a pulse synthesizer producing motor driving pulses and detection pulses; a reference voltage source; a plurality of resistor elements and means for selectively including the same in circuit to establish a detection resistance of selectable value dependent on the elements selected for inclusion in circuit; means for utilising, when the timepiece is in normal time-keeping operation, detection pulses from the synthesiser to produce in the detection resistance a detection voltage dependent upon whether the motor has stopped, after a driving pulse, in a rotation condition or in a non-rotation condition; means for providing a zone in which the timepiece is not in normal timekeeping operation and in which selection of the resistor elements can be effected; and means for utilizing, during said zone, detection to effect selection until a voltage produced in the detection resistance by such a pulse reaches the threshold voltage.

11. Battery powered stepping motor driven analog timepieces as claimed in any of the preceding claims and substantially as herein described with reference to the accompanying drawings.

12. An analogue display electronic timepiece comprising function that current is flowed through coil as detection pulse in order to detect rotor position, the rotor position is determined by the magnitude of the detection current and driving pulse width of stepmotor is controlled, characterized in that resistance element is connected in series with said coil after fixed time has passed upon starting to flow current, and rotor position is determined by taking out the current value at this time as voltage across said resistance element.

13. An analogue electronic timepiece comprising, at least, an oscillator circuit, a frequency divider circuit, a pulse-width synthesizer circuit, a rotation detector circuit, detection resistors, a reference voltage generator circuit, a stepper motor, and a small-size electric cell serving as a power supply, the arrangement being that said rotation detector circuit determines whether a rotor of said stepper motor rotates on the basis of the magnitude of a voltage generated across said detection resistor by a, detection current flowing through a coil of said stepper motor, characterized in that said detection resistors are available in a plurality of resistances and can selectively be established in a zone for setting the resistor.