JPS6313158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic timepiece, and more particularly to a motor drive system for an electronic timepiece that uses a pulse motor as an electromechanical conversion mechanism.

An object of the present invention is to increase the effective electromechanical conversion efficiency of such a pulse motor and to reliably reduce power consumption of a timepiece without impairing reliability.

A so-called crystal analog clock that uses a crystal oscillator as the time standard and mechanically displays seconds, minutes, hours, etc.
Particularly in the case of wristwatches, the time standard is extremely accurate, and the accuracy of the crystal oscillator serving as the time standard as well as the lifespan of the power source battery are major factors in the reliability of the displayed time. In the case of quartz watches that have an electromechanical conversion mechanism, the power consumption of the electromechanical conversion mechanism is larger than that of the electronic circuit including the oscillation circuit. It is expected to increase battery life. The total current consumption of a circuit using a crystal with an oscillation frequency of 10 KHz is currently less than 1 μA, and can be reduced further to 0.5 μA. On the other hand, the current consumption of the converter is 2 to 3.5 μA.
This is extremely common, and there is a noticeable imbalance in the current consumption between the circuit section and the conversion section. If the mechanical parts after the converter become larger, the current consumption in the converter will further increase.

The present invention reduces current consumption when a pulse motor is used as a conversion mechanism by controlling motor drive conditions, and the reliability of the watch is not compromised. The pulse motor drive conditions for a portable watch must take into account the load conditions and environmental resistance of the mechanical parts after the motor, as well as the drive voltage range. Here, in designing the conventional pulse motor and setting the driving conditions, the highest efficiency was obtained at the equivalent maximum load when all of the above-mentioned condition items were considered. Considering the actual motor load conditions, the load on the mechanism includes the constant load of the wheel train and a calendar mechanism that operates intermittently. Equivalent load increases due to disturbances during carrying include instantaneous large loads due to shocks and equivalent load increases due to external magnetic fields. When using a silver battery, silver oxide battery, etc., the drive voltage varies from approximately 1.6V to 1.3V due to an increase in internal resistance, including temperature changes.
However, in reality, the timepiece body is in the equivalently large load state described above only for a very short time in a day, and most of the time it is in a static state and under a very small load state. The present invention controls the drive conditions according to changes in the load value, and supplies narrow pulse width and small output drive energy to the motor during normal load,
If there is an equivalent increase in load compared to normal conditions due to disturbance or other effects, output commensurate with the increase in load, or wide pulse width high output drive energy equivalent to the maximum rated output in the conventional design. It is intended to supply Furthermore, in the present invention, in order to ensure stable and reliable operation, a signal with a slightly wider pulse width than the narrow pulse width signal is added once immediately after the transition from the wide pulse width signal to the narrow pulse width signal.

Therefore, it is clear that the driving method of the present invention can reduce the average current consumption compared to the current consumption when driving under a conventional constant driving condition, that is, the maximum rated driving condition. Moreover, the instability caused by adopting this drive method is also eliminated.

Examples of the present invention will be described below.

Figure 1 shows an example of a pulse motor for an electronic wristwatch, and the figure shows a two-pole magnetized permanent magnet rotor, with rotor 1 sandwiched between stator 2,
3 are placed facing each other. The stators 2 and 3 are actually one body and are connected by g ¹ and g ² , but since g ¹ and g ² are extremely thin, they have the same effect as if they were separated. The stators 2 and 3 are each connected to a yoke 5 around which a coil 4 is wound to form a set of stators. The stators 2 and 3 are arranged so that the rotor 1 can rotate in a fixed direction.
Notches 2a and 3a are provided in the stators 3 to shift the magnetic pole (N and S) positions of the rotor 1 to one of the stators 2 and 3 when the rotor 1 is at rest. The dashed line indicates the rest position of the rotor poles.

This type of pulse motor has been in practical use for some time, and was driven by a circuit block as shown in FIG. 10 is a crystal resonator, and an oscillation circuit 11
The frequency is divided by the frequency divider 12, and the waveform shaper 13 shapes two pulses having an appropriate time width and a phase difference of 180° at an appropriate time interval.

An example is a 7.8 msec pulse every 2 seconds. This pulse is input to the drivers 14 and 15 composed of CMOS inverters, and the output is sent to the coil 4.
is supplied to terminals 4a and 4b. FIG. 3 is a detailed diagram of this driver section, and one inverter 14
When a signal 18 is applied to the input terminal 16 of the other inverter 15, a current flows as shown by an arrow 19. Conversely, when a similar signal is applied to the input terminal 17 of the other inverter 15, a current flows in a route symmetrical to the arrow 19. Inverters 14 and 15 are P channels as is well known.
It is composed of MOS transistors 14a and 15a and N-channel MOS transistors 14b and 15b. That is, by alternately applying signals to the input terminals 16 and 17 of both inverters, the current flowing through the coil 4 can be alternately reversed. Specifically, a current of 7.8 msec, which is alternately reversed every second, is applied to the coil 4. It can be passed to 4. With such a drive circuit, N and S poles are alternately generated in the stators 2 and 3 of the pulse motor shown in Figure 1, and the rotor 1 can be rotated 180 degrees by repulsion and attraction with the magnetic poles of the rotor 1. . The rotation of the rotor 1 is transmitted to the fourth wheel 7 via the intermediate wheel 6, and further to the third wheel, second wheel, cylinder pinion, hour wheel, and calendar mechanism (not shown), and is transmitted to the hour hand, minute hand, Operates an indicating mechanism consisting of a second hand, calendar, etc.

The pulse motor shown in FIG. 1 has been used as a conversion mechanism for electronic wristwatches.

In the drive circuit shown in FIG. 3, when a low level signal is applied to the terminal 17 and a signal 18 is applied to the terminal 16 to cause a current to flow as shown by an arrow 19, the MOS transistor 15 has a channel impedance that causes the drive current to flow. A signal waveform corresponding to this current generated by the voltage drop can be detected at the terminal 4b. The current waveform is as shown in FIG. 4, for example.

Now, point A in FIG. 4 is the point at which the application of the drive pulse has ended. Therefore, the current after point A is an induced current generated by the damped vibration rotation of the rotor. Waveform 20 and waveform 20' of FIG. 4 are a series of waveforms, which is the case when the load on the rotor is very light.
Waveform 22 and waveform 22' are also a series of waveforms, and in this case, the load on the rotor is large and the rotor is close to its operating limit, and waveform 21 and waveform 21' represent a load that is approximately 1/2 of the maximum allowable load. This is the case when it is multiplied. If you carefully observe the current waveform when the load is changed in this way, you will see that the waveform extends to the right as the load increases.

This is because the rotation of the rotor slows down as the load increases, and it has been experimentally confirmed that the rotor vibration frequency and amplitude become low until it stops at a stable position.

Next, a method for detecting this load will be described. Fifth
The figure shows the phase relationship between the coil current i and the rotor rotation angle θ. The lower middle curve in Figure 5 shows the rotor advancing one step by the drive pulse and reaching the next pulling position (180°).
The peak position of the coil current after application of the drive pulse approximately corresponds to when the rotor passes near the pulling position.
The correspondence of the waveforms shown in Fig. 5 is shown in Fig. 4 20', 21',
It has been confirmed that the same can be obtained for each waveform of 22'. This is because current is induced in the electromagnetic coil based on fluctuations in the magnetic field within the stator caused by the vibration of the rotor magnet, and when viewed from the rotation angle of the rotor, the center is at the pulling position (180°, 0°). Since the polarity of the rate of change of the stator internal magnetic field changes before and after that, the peak of the coil current corresponds to the pulling position. Also, since the relationship between motor load and coil induced current is as shown in Figure 4,
Motor load detection can be performed from the coil induced current waveform.

The configuration of the present invention is that the motor is normally driven with a narrow drive pulse assuming no load, the magnitude of the load is always detected from the induced voltage waveform after driving, and when the load is small, the initial narrow drive pulse width is used. Continue driving. When the load increases and approaches the limit of driving with a narrow drive pulse width, the next drive is driven with a wide drive pulse width for a certain period of time, and then the drive is returned to the original narrow drive pulse width. When returning from a wide drive pulse to a narrow drive pulse, Part 1
The narrow drive pulse applied for the second time is made slightly wider than the drive pulses applied for the second and subsequent times.

The present invention generally has such a structure, and will be explained in more detail with reference to the block diagram of FIG.

FIG. 6 is a block diagram showing the configuration of the present invention, where 25 is a time standard oscillator, 26 is a circuit including an oscillation circuit, a frequency dividing circuit, etc., 27 is a pulse motor drive circuit, and 28 is explained in FIG. The configuration up to this point with a pulse motor like this is the same as a conventional electronic wristwatch. Reference numeral 29 denotes a load detection circuit that detects a load based on the induced current waveform after application of a drive pulse, as explained in FIG. In this example of a load detection circuit, it is determined whether the load is larger or smaller than a predetermined value. In other words, the limiter 23 is set at an appropriate time position in FIG.
When the peak position is before the limiter 23 as shown in the induced current waveforms 20' and 21', it is determined that the load is 0 or small, and when the peak position is before the limiter 23 as shown in the induced current waveform 22'. When there is no peak, it is determined that the load is large. Note that peak detection can be extracted as an electrical signal using a well-known differentiation circuit. The limiter is also formed by a well-known two-input gate circuit, and by inputting a gate signal for a predetermined time to one side and inputting a peak detection signal from the above-mentioned differentiating circuit to the other, it is possible to generate a peak within the predetermined time. If the detection signal does not pass through the gate circuit, a heavy load state may be detected. The output of this gate circuit is then used as the detection output of the detection circuit. Reference numeral 30 denotes a control circuit that controls the drive of the pulse motor 28 according to the load condition detected by the load detection circuit 29. Normally, the control circuit supplies narrow drive pulses when there is no load and wide drive pulses when there is load. . However, a slightly wider narrow pulse is supplied only immediately after switching from a wide pulse to a narrow pulse. Control circuit 30
is at least a first output signal that applies a narrow drive pulse with a normal drive cycle under normal load, and a first output signal that has a cycle different from the first output signal when a heavy load state is detected by the load detection circuit 29. a second output signal that applies a drive pulse having the same polarity as the signal and a wide pulse width successively to the narrow drive pulse;
Based on the output signal of the frequency dividing circuit 26, a third output signal is output which applies a remanence erasing pulse successively to the wide drive pulse with a polarity opposite to that of the second output signal when the second output signal is output. It is configured like this. A selection circuit is configured in the control circuit 30 so that the selection between the first output signal, the second output signal, and the third output signal is made based on the detection signal from the load detection circuit. This control method will be explained with reference to FIG. FIG. 7 shows the state of the drive pulses, which are supplied as described above in the section regarding the pulse motor, and are shown as pulses 31 and 32. Pulses 31 and 32 are narrow pulse widths under no-load conditions. After applying the pulses 31 and 32, the detection circuit of FIG. 6 detects a load condition, which is either no load or a small load condition.

That is, since the load detection after pulse 31 was determined to be no load, the next pulse 32 has a narrow pulse width, and since the load detection after pulse 32 was also determined to be no load, the next pulse 33 also has a narrow pulse width. In load detection after pulse 33, it was determined that the vehicle was in a loaded state. In this case, after pulse 33, the second drive pulse 34 with a wide pulse width is applied several tens of milliseconds after pulse 3.
3 with the same polarity (ie, the same current direction). After that, pulses 35 and 36 with wide pulse widths are applied for a certain number of pulses, and then pulse 37 with a slightly wider pulse width than the initial narrow pulse width pulse is applied only once, and thereafter, the pulse width is again the same as the initial narrow pulse width. pulses 38 and 39 are applied. To explain the relationship between pulse 33 and pulse 34, when a large load is detected by driving pulse 33, the number
After 10 msec, a wide pulse 34 is applied. Although it is determined that the load is large when the load is detected after the pulse 33, it is difficult to determine whether the rotor has operated at this time. This is because the induced current waveform in FIG. 4 shifts to the right and attenuates as the load increases. When the rotor does not operate, no induced voltage is generated, but it is difficult to distinguish this from the situation in which the rotor operates smoothly when the load is close to its limit. If the load increases gradually, even if the load is determined to be large, the rotor will still be operating at the pulse 33 at that time, and if the load suddenly becomes too large to be driven by a narrow pulse width, the rotor will not operate at the pulse 33. It doesn't work. It is difficult to distinguish between the two. Therefore, it is easy to set the load detection after pulse application so that there is some margin. In this configuration, pulse 34 is applied.
When the rotor operates with pulse 33, pulse 3
Since pulse 4 is a pulse in the same direction as pulse 33, this pulse 34 is a pulse with an opposite phase, and the rotor does not rotate. Further, when the rotor is not operated by pulse 33, it is driven by pulse 34. At this time, the rotor is driven with a delay of several tens of milliseconds, but this is not visible to the eye as an operation of the second hand, and there is no need to worry about unsightliness caused by this. Next, after the load is detected, the reason why the wide pulse width pulses 35 and 36 are continued for a fixed number of pulses is because the calender mechanism has the largest load on the rotor, and this
Since it lasts for 4 hours, if the pulse width is immediately returned to a narrow pulse width, it will be determined that it is in a loaded state again, and if this is repeated, two pulses will be supplied for each operation, increasing power consumption and eliminating the significance of reducing power consumption. In addition, the load on the rotor is not limited to the calendar mechanism.
There are also isolated loads such as magnetic fields, low temperatures, and disturbances. In such a case, it is desirable that the number of continuous pulses with a wide pulse width be as small as possible. In consideration of such a phenomenon, it is desirable to set the number of continuous pulses to several tens of seconds to several hundreds of seconds. It is also possible to use another method, such as detecting the load each time, determining whether the load is large or small, and setting the pulse width each time.

Next, after continuing a certain number of wide pulse width pulses, instead of immediately returning to the original narrow pulse width pulse, one pulse with a slightly longer pulse width is added.
The reason why it is supplied only once is as follows. As explained in FIG. 4, the peak position of the induced current moves depending on the magnitude of the load. For example, waveforms 20 and 20' are when there is no load. However, this is the waveform when pulses with a constant width are continuously supplied, and immediately after changing back from a wide pulse width to a narrow pulse width pulse, even if there is no load, the current waveform becomes 24, 24', and the peak position also appears at a later position. Even though there is no load, a current waveform appears as if there is a load, and if the peak position is at the limiter 23.
If it happens later, it may be determined that the load is large. A peak appears at the position from the second narrow pulse, but if it is determined that the load is large with the first pulse, the drive switches to a wide pulse width again, and the drive will never return to narrow pulse width driving. This peak delay phenomenon, which makes it impossible to achieve low power consumption in such a state, is thought to be due to the residual magnetic flux within the stator.
In other words, the stator that has been magnetized by a pulse with a wide pulse width cannot be completely magnetized in the opposite direction even if a pulse with a narrow pulse width in the opposite direction with a weaker magnetizing force is applied. Since the output torque is also lower than that of the second and subsequent pulses with the same narrow pulse width, it is considered that the state appears to be under load. This peak delay becomes smaller as the difference between the wide pulse width and the narrow pulse width becomes smaller. Therefore, rather than suddenly changing from a wide pulse width (e.g. 7.8ms) to a narrow pulse width pulse (e.g. 3.9ms), a pulse with a width of 7.8ms is followed by a pulse slightly wider than 3.9ms (about 0.5ms wider). (The effect is sufficient depending on the pulse width.) Supply only one pulse for residual magnetism erasing,
From then on, it is sufficient to supply pulses with a width of 3.9 ms. By adopting such a control method, it is possible to reliably reduce power consumption.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described here, and various improvements, changes, and applications are possible.

[Brief explanation of the drawing]

FIG. 1 shows an example of a pulse motor for an electronic wristwatch according to the present invention. FIGS. 2 and 3 show conventional circuit configurations. FIG. 4 shows the current waveform of the pulse motor drive coil. FIG. 5 shows the correlation between the detected waveform and the rotor rotation phase. FIG. 6 shows a circuit block of a timepiece according to the invention. FIG. 7 is an example of a time chart of motor drive pulses by the circuit according to the present invention. 25... Oscillation circuit, 26... Frequency dividing circuit, 27...
... Drive circuit, 28 ... Motor, 29 ... Motor load detection judgment circuit, 30 ... Control circuit, 31 to 33
... Narrow pulse drive signal, 34 ... Correction signal, 35
~36... Wide pulse drive signal, 37... Narrow pulse drive signal with a slightly wider width.

Claims (1)

[Claims] 1 Frequency dividing circuit 2 that divides the output of the oscillation circuit 25
6. A drive circuit 27 that operates based on the output signal of the frequency dividing circuit 25; a pulse motor 28 that is composed of a coil, a stator, and a permanent magnet rotor and is driven by the drive circuit; and a pulse motor 28 that is connected to the coil and operates after applying a drive voltage. a load detection circuit 29 that detects the load state of the rotor based on the induced current generated in the load detection circuit 29; a control circuit 30 that is connected between the frequency dividing circuit and the drive circuit and controlled by the output signal of the load detection circuit;
The drive circuit includes a first transistor 15a and a second transistor 14a that connect each end of the coil to one pole of the power source, and a second transistor 14a that connects each end of the coil to the other pole of the power source. and a third transistor 15b and a fourth transistor 14b, and the first and fourth transistors or the second and third transistors are alternately brought into conduction based on an output signal from the control circuit to connect the coil to the coil. The control circuit outputs first output signals 31 and 32 having a first pulse width in a first cycle when the load is normal according to the output of the load detection circuit, and detects a heavy load state, a second drive signal having a cycle different from that of the first drive signal, the same polarity as the first drive signal, and a pulse width larger than the first pulse width is generated.
outputting an output signal following the first drive signal, and when the second output signal is output, the second drive signal is outputted.
An electronic timepiece characterized in that a third output signal having a polarity opposite to that of the output signal and serving as a pulse for erasing residual magnetism is outputted in succession to the second output signal.