JPS6137586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic wristwatch, and more particularly to an improvement of a step motor, which is an electromechanical conversion mechanism thereof.

Since the so-called quartz wristwatch, which uses a quartz oscillator as a time standard oscillator, was put into practical use, numerous technological innovations and improvements have gradually increased production volume and lowered prices, leading to the widespread use of quartz wristwatches today. However, in analog quartz wristwatches with pointer displays, technological innovations related to crystal oscillators and electronic circuits have been remarkable, but compared to this, electromechanical conversion mechanisms have lagged behind. In other words, from a cost standpoint, this component plays a large role among the components of a quartz wristwatch, and from a performance standpoint, most of the power consumption is consumed by this electromechanical conversion mechanism, which increases the lifespan of the quartz wristwatch or increases battery life. Due to miniaturization, watch bodies are becoming smaller and thinner, which is becoming a major problem.

In order to improve the above-mentioned drawbacks, the present invention employs a bipolar rotor type step motor as an electromechanical conversion mechanism, and by optimizing the shape of the step motor, it eliminates the need for adjustment and reduces costs. By adopting a drive system suitable for the motor, stable operation is possible with low power.Examples will be explained in detail below with reference to the drawings.

In Fig. 1, reference numeral 1 denotes a rotor made of a permanent magnet magnetized into two poles, and stators 2 and 3 are arranged facing each other with this rotor 1 in between.These stators 2 and 3 each have a coil 4 is connected to a wound yoke 5 to form a set of stators. The stators 2 and 3 are arranged so that the arcuate parts 2a and 3a of the stators 2 and 3 are eccentric by an amount X with respect to the center of the rotor 1 so that the rotor 1 can rotate in a fixed direction, and the magnetic poles (N and S) of the rotor 1 are positioned at rest. is shifted to one of stators 2 and 3. This type of step motor has been in practical use for some time and was driven by a circuit as shown in FIG. 1
0 is a crystal oscillator, which is driven by an oscillation circuit 11, whose frequency is divided by a frequency divider 12,
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 of this is a pulse of 7.8 msec every 2″.
4 and 15, and the output is sent to terminal 4 of coil 4.
a, 4b. FIG. 3 is a detailed diagram of this driver section, and when a signal 18 is applied to the input terminal 16 of one inverter 14, an arrow 19
A current flows as shown by arrow 19, and 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 arrow 19. 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, and more specifically, it can be caused to flow every second. Due to this drive current, N and S poles are generated alternately in the stators 2 and 3 of the step 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 transmitted to the third wheel 8, second wheel 9, and further to the cylinder pinion and hour wheel (not shown) to the calendar mechanism, and the hour hand. , operates an indicating mechanism consisting of a minute hand, second hand, calendar, etc.

The step motor shown in FIG. 1 operates in principle as explained above. However, such step motors that have been used in the past are unsuitable for controlling the drive pulse width as will be described in detail later. That is, curve A shown in FIG. 9 is the characteristic of drive pulse width versus output torque of the conventional step motor. In conventional step motors, the drive pulse width was constant, so it was only necessary to extract as much output torque as possible within that drive pulse width, so it was sufficient to have a characteristic with a steep slope as shown in curve A. It is. However, this does not allow the driving pulse width to be made very small, and even if pulse width control is performed, a significant reduction in power cannot be expected. In order to effectively control the pulse width, it is necessary to use a step motor with characteristics suitable for the purpose, and in the present invention, a step motor with characteristics as shown by curve B in FIG. 9 is used. In other words, for a step motor with characteristics like curve B, the minimum required torque F is
Although it is not possible to make the pulse width shorter than D, which is the pulse width that can be obtained by can be converted into In a step motor using a pulse width control circuit as described below, it is absolutely necessary to use a motor with such characteristics in order to effectively reduce power consumption. is 3/ compared to when under load.
Driving is possible with a pulse width of 5 or less.

The present invention aims at extremely low power consumption of this step motor by the drive method described below, and will be explained in detail below.

By the way, when signal 18 is applied to the terminal in the drive circuit shown in Fig. 3 and current flows as shown by arrow 19,
A voltage drop based on the drive current occurs due to the channel impedance of the MOS transistor 15, and a signal corresponding to this current can be detected at one end 4b of the coil. This current waveform becomes a waveform 20 shown by a solid line in FIG. This current waveform 2
As is clear from the diagram, the major feature of 0 is that there is a part (indentation) where the current value decreases in the middle, and the reason why the current changes so drastically is that the induced current in the coil is caused by the rotation of the driven rotor. To flow,
The dent in the current waveform is the part where this induced current is maximum, and this condition is met when the magnetic flux change in the coil is maximum, that is, when the rotor's magnetic pole crosses the gap between both stators (δ ₁ , δ ₂ part). It's time to pass.

The above description shows that the step motor operates under no-load conditions, but when a load is applied to the motor, the current waveform changes. This state is shown in waveform 2 by the dotted line in Figure 4.
1, and furthermore, the waveform becomes 22. This waveform 22 is the limit that can withstand the load, and if more load is applied, the rotor will stop. Observing this fact from the current waveform, the motor will operate while there is a dent in the current waveform within the drive pulse.In other words, if the current flows until the rotor's magnetic pole reaches the gap between both stators, the rotor will operate. be. Therefore, although the waveform 20 under load has a margin when a load is applied, a large amount of wasted current flows when no load is applied.

The drive method of the present invention focuses on this drawback, and detects the rotational state of the rotor from the waveform of the motor drive current, regardless of whether it is under no load or under load, and cuts off the drive current that is more than necessary, thereby adjusting to the size of the load. The drive pulse width is changed accordingly to always drive with the lowest power consumption, and one of the drive circuits
An example is shown in FIG. 5, and a time chart thereof is shown in FIG.

Terminals 23 and 24 correspond to terminals 16 and 17 in the conventional circuit diagram of FIG. 2, and apply signals A and B in FIG. 6. In other words, the phase differs by 180 degrees, but every 2 seconds
A 7.8 msec pulse is applied. Now terminal 23
When the signal changes from LOW to HIGH, the output of the NAND gate 25 changes from HIGH to LOW as shown in FIG. 6D. The output of the other NAND gate 26 is HIGH
Therefore, a current flows in the coil 4 from the terminal 4a to 4b, and as mentioned above, a voltage drop occurs based on the drive current due to the channel impedance of the MOS transistor, and the coil 4 is connected to the terminal 4a as shown in FIG. 6C. The waveform of the current flowing through is observed. This current waveform is alternately selected between terminals 4a and 4b by an analog switch constituted by a transmission gate, and is amplified by a CMOS amplifier 30 via a capacitor 29. Capacitor 29 is an AC coupling capacitor, and 4a or 4 to be detected.
Shift the signal level of b to the operating level of the CMOS inverter amplifier. The resistor 37 is a feedback resistor for using the CMOS inverter 30 as an amplifier, and together with the capacitor 29 forms a differentiating circuit for the input signal. capacitor 2
9 and the resistor 37 are therefore determined by the input signal and the characteristics of the amplifier 30. In the present invention, the values of the circuit shown in FIG.
In the figure, the capacitor 29 has a value of several hundred PF, and the resistor 37 has a value of several tens of MΩ. The operation of the amplifier 30 will be explained below.

FIG. 8I shows changes in potential that occur alternately at 4a and 4b, and corresponds to the drive current waveform. This signal is selected by transmission gates 27, 28 and applied to the input of capacitor 29. 8J is the output of the amplifier 30, and the output level in the standby state is at an intermediate value as shown at J, and does not take a logic level. At this time, amplifier 3
The output of the inverter buffer 38 which receives the output of 0 is at the logic level LOW as shown in FIG. 8K. When the current waveform signal shown in FIG. 8I is supplied through the capacitor 29, the capacitor 2
9 and a resistor 37, and the phase is inverted by an amplifier 30 to obtain a differential signal of J. gate 3
8 is LOW in the standby state as described above. When the differential output signal of the amplifier 30 is at the standby level and above the standby level, the output of the buffer 38 is LOW; when the differential output signal of the amplifier 30 is below the standby level, the output of the buffer 38 is LOW.
It becomes HIGH. 8K and 6E show the output of buffer 38. FIG.

The waveform in Figure 8K shows that two pulses are generated for one motor drive, but the falling position of the first pulse is the position where the motor drive current decreases, that is, the magnetic pole of the rotor is closer to the stator. It can be seen that the position approximately corresponds to the position where the gap passes through the gap. After the magnetic poles of the rotor pass through the gap, it is safe to assume that the rotor achieves one-second steps due to its own inertia or magnetic force, so approximately the current after the fall of the first pulse is It can be considered as unnecessary current. As mentioned above, the waveform in Fig. 8 I changes depending on the load condition of the motor, so for each load condition, the falling position of the first pulse of K By cutting off the drive current, the motor can be driven efficiently according to the load. Specifically, when the flip-flop 31 is not generating a pulse signal, it is always kept in the reset state, and when the pulse signals A and B are generated, the reset state is released. The flip-flop 31 may be configured to be set. flipflop 31
Since the output of the inverter 33 is low in the reset release state and high in the set state, the output of the inverter 33 is used to determine the operating time of the NAND gates 25 and 26. In reality, it is possible to delay the cut-off position of the drive current to some extent depending on the characteristics of the amplifier circuit, the load, etc. with respect to the falling position of the pulse. Although the delay circuit is omitted in FIG. 5, this type of circuit is extremely common and is therefore omitted.
FIG. 5 31 shows a flip-flop, which is a circuit that generates a drive signal whose pulse width is limited according to the output of the buffer 38. This flip flop 3
The output of 1 is F in Figure 6, which is sent to inverter 3.
Block the NAND gate 25 with the inverted signal in step 3,
As shown in the output shown in FIG. 6G, the pulse is driven with a pulse shorter than the original applied pulse width (7.8 msec). If the rotor is loaded and its movement slows down, the pulse width will naturally expand accordingly.

However, the maximum driving pulse width is the pulse width applied to the terminals 23 and 24 (7.8 msec in this case). This is because a pulse width of this level is sufficient for the output torque of the motor, and if a pulse width greater than this is allowed, the current will increase when the rotor completely stops, resulting in little benefit.

Note that the CMOS amplifier 30 is a clocked gate.
It is composed of a CMOS inverter, and as shown in the figure, it is configured to operate only when the step motor is driven.
Cuts out unnecessary current.

By the way, FIG. 7 shows the current waveforms when driven by this drive circuit. Waveform 34 is the current waveform when there is no load, and 35 and 36 are the current waveforms when the load is on. If you do, the motor will stop working. Comparing this with Figure 4, there is no change in the output torque of the motor, but it is clear that the current has been reduced.

As described above, the present invention aims to reduce power consumption by cutting off unnecessary current to the step motor, and also uses a current detection element (for example, There is no need for a resistor (resistance), and there is no loss when inserting a resistor.Furthermore, the amplifier in the control circuit is also configured with CMOS, and the amplifier operates only when necessary, streamlining the control circuit and reducing power consumption. It is something that has been transformed.

The embodiments of the present invention have been described in detail above, and in this drive circuit, after the drive pulse is cut off, both ends of the coil are electrically short-circuited. When both ends of the coil are shorted, the coil absorbs the induced current generated by the subsequent movement of the rotor, which applies a brake to the rotor, which prevents the rotor from wobbling after operation and stabilizes its operation. However, if the short-circuit does not occur immediately after the driving pulse is cut off, but rather is short-circuited several milliseconds after the cut-off, the above effect can be achieved, and the output can be increased without unnecessary braking. Although changing to such a circuit requires a slight increase in the number of elements, it can be easily realized by slightly changing the circuit shown in FIG. 5.

Here, the current consumption values of one example to which the present invention is applied and a conventional one are shown. When a step motor with characteristics as shown in FIG. 9A is driven by a conventional drive circuit, the average current consumption in the step motor is approximately 1.8 μA (pulse width is 7.8 ms,
Figure 9C position). On the other hand, if this step motor is driven using a drive circuit that performs pulse width control, the drive time without load will be 18 hours in a day, and the time under load such as when changing the date or day of the week will be 6 hours. Under load, it is 1.8 as before.
μA, but when there is no load, it is driven with a pulse width of about 6.2 ms (Fig. 9 D), and the current consumption at this time is about 1.2
μA, which is a 33% decrease. Furthermore, according to the method of the present invention, if pulse width control is applied to a step motor with characteristics as shown in FIG. Even if it is driven, it is driven with a pulse width of about 4.5 ms (Fig. 9E) when there is no load, and the average current consumption at this time is about 0.7 μA.
Therefore, the average current consumption per day is less than 1.0 μA, and a further 20% reduction in power can be achieved.

According to the structure of the present application, the drive circuit is formed of a pair of CMOS transistors provided at both ends of the coil, and one transistor is used as an impedance for load detection, so the following effects are achieved.

(a) Since the electronic elements of the drive circuit and the electronic elements of the load detection means are shared as common parts, the number of parts can be reduced accordingly, and the construction can be simplified and costs can be reduced.

(b) Since the transistor of the drive circuit is used as the detection impedance of the load detection means,
It is easy to integrate it into an IC, and it is possible to provide a small and low-cost drive device as a whole.

Furthermore, since the amplifier section was formed from a clocked CMOS inverter, the clocked gate was activated only when there was a signal from the waveform shaping circuit, significantly reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a step motor and a wheel train according to an embodiment of the present invention. FIG. 2 is a block diagram of an electronic circuit of a conventional electronic wristwatch. Figure 3 is the second
FIG. 3 is a detailed view of the driver shown in FIG. FIG. 4 is a current waveform diagram thereof, FIG. 5 is a drive circuit showing an embodiment of the present invention, FIG. 6 is a time chart thereof, and FIG. 7 is a current waveform diagram thereof. FIG. 8 is a circuit waveform diagram of FIG. 6. FIG. 9 is a characteristic diagram of drive pulse width versus output torque of a conventional step motor and a step motor to which the present invention is applied. 1...Rotor, 2, 3...Stator, 4...
...Coil, 10...Crystal oscillator, 25, 26...
NAND gate, 30...amplifier, 34, 35, 3
6...Current waveform.

Claims (1)

[Scope of Claims] 1 (a) an oscillation circuit having a crystal resonator; (b) a frequency divider that divides the output from the oscillation circuit; and (c) an input circuit that receives the output from the frequency divider. (d) a drive circuit that inputs the output of the waveform shaper to drive a step motor having a permanent magnet rotor, a stator, and a coil; (e) the drive circuit comprises: an analog switch consisting of a NAND gate provided at both ends of the coil, a transmission gate that gates the output of the NAND gate with a signal from the waveform shaper, a capacitor AC coupled to the analog switch, and a capacitor connected to the capacitor. a buffer inverter that shapes the signal of the amplifier; a flip-flop whose set terminal inputs the output of the buffer inverter; and an inverter that controls the operation of the NAND gate accordingly, and the amplifier is a clocked gate CMOS clocked by the OR input of the signal from the waveform shaper.
The flip-flop is composed of an inverter, and the flip-flop has a reset terminal to which the OR input of the output signal from the waveform shaper is connected, and the output signal input to the reset terminal and the output signal of the buffer inverter input to the set terminal. An electronic timepiece characterized in that a time for the NAND gate to generate a driving current to the coil is set by an output signal.