JPS6113191B2 - - 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, in terms of performance, most of the power consumption is consumed by this electromechanical conversion mechanism, which is becoming a major factor in extending the lifespan of quartz watches or making watch bodies smaller and thinner by making batteries smaller. .

In order to overcome these drawbacks, the present invention employs a bipolar rotor type step motor as an electromechanical conversion mechanism, and by adopting a drive system suitable for this step motor, stable operation with low power is possible. Examples are described 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. 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. 10 is a crystal resonator, which is driven by an oscillation circuit 11;
The frequency is divided by the frequency divider 12, and the waveform shaper 13 divides the frequency into 180
Two pulses with different phases are formed.

An example is a pulse of 7.8 seconds every 2″.
Driver 1 consisting of CMOS inverter
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. When a signal 18 is applied to the input terminal 16 of one inverter 14, a current flows as shown by an arrow 19, and conversely, a current flows to the input terminal 16 of one inverter 14.
When a similar signal is applied to the input terminal 17 of 5, 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. 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. Due to this drive current, the stators 2 and 3 of the step motor shown in Fig. 1 have an N pole and an S pole.
The poles are generated alternately, 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, and has also been used as a conversion mechanism for electronic wristwatches. The present invention aims at extremely low power consumption of this step motor by the drive method described below, and will be described 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. The current waveform becomes a waveform 20 shown by a solid line in FIG. This current waveform 20
As is clear from the diagram, the major feature of is that there is a part (indentation) where the current value decreases in the middle.The reason why the current changes so drastically is that an induced current flows in the coil due to the rotation of the driven rotor. Therefore, the dent in the current waveform is the part where this induced current is maximum, and this condition is satisfied when the magnetic flux change in the coil is maximum, that is, when the rotor's magnetic poles are in the gap between both stators (δ ₁ , δ It is time to pass part ₂ ).

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. The drive pulse width is changed according to the drive circuit to always drive with the lowest power consumption.
An example is shown in FIG. 5, and a time chart thereof is shown in FIG. Although not shown in FIG. 5, the crystal resonator 10, oscillation circuit 11, and frequency divider 1 shown in FIG.
2 is omitted because it is the same in the present invention. Further, the waveform shaping circuit 13 is also used in the same manner.

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 7.8
A pulse of msec is applied. Now terminal 23 is LOW
When the output goes from HIGH to HIGH, the output of the NAND gate 25 changes from HIGH to LOW as shown in FIG. 6D. the other
Since the output of the NAND gate 26 is HIGH, current flows in the coil 4 from terminal 4a to terminal 4b, and as described above, the waveform of the current flowing in the coil as shown in Figure 6C is observed due to the channel impedance of the MOS transistor. be done. 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 a 4C coupling capacitor that detects the signal level of 4a or 4b to be detected.
Shift 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 two-differential circuit for the input signal. Capacitor 29 and resistor 37
Therefore, the value of is determined by the input signal and the characteristics of the amplifier 30, but for the circuit diagram 5 and the waveform diagram 4 described as examples in the present invention, the capacitor 29 is several hundred PF, and the resistor 37 is several hundred PF. 10 MΩ was obtained. 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 terminal of capacitor 29. J in FIG. 8 is the output of the amplifier 30, and the output level in the standby state is at an intermediate value as shown in J,
The logic level is not taken. At this time, the output of the inverter buffer 38 which receives the output of the amplifier 30 is the eighth
As shown in FIG. K, the logic level is LOW.
When the current waveform signal shown in FIG. 8I is supplied through the capacitor 29, the capacitor 29 and the resistor 3
7, and the phase is inverted by an amplifier 30 to obtain a differential signal of J. Gate 38 is LOW in the standby state as described above. When the differential output signal of amplifier 30 is at the standby level and above the standby level, the output of buffer 38 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 rotor It can be seen that the magnetic pole approximately corresponds to the position where it passes through the gap in the stator. After the magnetic poles of the rotor pass through the gap, it is safe to assume that the rotor achieves a one-second walk due to its own inertia or magnetic force, so the current after the fall of the first pulse is approximately It can be considered as unnecessary current. As mentioned above, the waveform in Figure 8 I changes depending on the motor load condition, so the drive current is determined at the falling position of the first pulse of K for the signal waveform detected for each load condition. If it is shut off, the motor can be driven efficiently according to the load. In reality, it is possible to delay the cut-off position of the drive current to some extent with respect to the falling position of the pulse depending on the characteristics of the amplifier circuit, the load of the motor, etc. 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 controlled according to the output of the buffer 38. The output of this flip-flop 31 becomes the signal F shown in FIG.
5 is cut off, and as shown in FIG. 6G, the pulse is driven with a pulse width 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 comes to a complete stop, 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.

That is, according to this embodiment, as clearly shown in FIG. 5, the capacitor 29, amplifier 30, inverter 38, flip-flop 31, and inverter 33 connected to the ends 4a and 4b of the coil 4 function as a rotor load detection circuit. The detection signal F is output from the inverter 33 as described above. Gates 26 and 25 also form a pulse width control circuit and a drive circuit. That is, when input signals A and B are applied to one of the terminals 23 and 24, one output terminal of the gate becomes L, and a drive current flows through the coil, and when a predetermined induced current is generated in the coil, the output inverter 33 of the detection circuit changes. The output becomes L, cutting off the gates 25 and 26 and stopping the drive current. This causes the drive current to constantly vary and only the required amount to be supplied. Note that the pulse width control circuit is used in combination with the waveform shaping circuit 13 shown in FIG. Ru. Furthermore, in the load detection circuit described above, the amplifier 30 that amplifies the output obtained by differentiating the induced current component by the capacitor uses a clocked gate type CMOS inverter, and the input signals A and B are used as the clock via the OR gate 45. is used. As a result, the amplifier 30 operates only during the detection period of the induced current component, so there is an advantage that no extra power is consumed.

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, it is clear that although there is no change in the output torque of the motor, a small change in current is being measured.

Since the capacitor 29 requires a capacity of several tens of PF to several thousand PF, it is difficult to incorporate it into an IC, and the conventional mounting method is to solder it to a circuit board as shown in FIG. However, this method has drawbacks such as a large mounting area and an increase in the number of soldering points. The present invention overcomes these drawbacks by improving the mounting method. That is, as shown in FIG. 10, a chip-type capacitor 29 is built into the IC package, and wiring is performed simultaneously with bonding of the IC chip.

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 control circuit is streamlined and low-cost so that the amplifier operates only when necessary. It is intended to be electrified.

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.

According to the configuration of the present invention, there is provided a load detection circuit that detects the induced current generated in the coil as a load and changes the pulse width of the pulse signal, and the load detection circuit is connected to the end of the coil and This control is performed so that the amplifier for amplifying the current component operates only during the induced current detection period, and then has a period in which it remains inactive, and has the following effects.

(a) The induced current generated in the coil occurs not only when a pulse signal is applied, but also when the rotor undergoes rapid vibration due to an impact or the like.

In the present invention, the amplifier constituting the load detection circuit is activated only during the induced current detection period, so that unnecessary current consumption due to such external shocks can be prevented.

[Brief explanation of drawings]

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 schematic diagram showing a conventional method of mounting a capacitor. FIG. 10 is a schematic diagram showing a method of mounting a capacitor according to the present invention. 1... Rotor, 2, 3... Stator, 4...
Coil, 10... Crystal oscillator, 25, 26...
NAND gate, 30...amplifier, 34, 35, 3
6...Current waveform, 39...Circuit board, 40...
I, C package, 41...solder, 42...lead, 43...I, C chip, 44...bonding wire.

Claims (1)

[Claims] 1. an oscillator, a frequency divider that divides the output of the oscillator, a drive circuit operated by the output of the frequency divider,
In an electronic watch equipped with a step motor consisting of a coil, a stator, and a permanent magnet rotor and driven by the drive circuit, the rotor load is detected from the induced current connected to the end of the coil and generated in the coil by driving the rotor. a load detection circuit for detecting the load, a pulse width control circuit connected between the frequency divider and the drive circuit, and forming a drive pulse with a large pulse width when the load is heavy based on the output of the load detection circuit; An electronic wristwatch characterized in that the circuit includes an amplifier that amplifies the current input from the end of the coil, is controlled by a pulse signal synchronized with the drive pulse, and becomes inactive after detecting a load.