JPS6113192B2 - - 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 so-called quartz wristwatches were put into practical use using a quartz crystal as a time standard oscillator, 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 these drawbacks, the present invention adopts 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 a step motor, stable operation is possible with low power consumption.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. A set of stators is constructed by connecting yoke 5 wound with 4 stators. The stators 2 and 3 have their arcuate portions 2a and 3a eccentric by X with respect to the center of the rotor 1 so that the rotor 1 can rotate in a fixed direction.
The magnetic pole (N and S) positions of the rotor 1 when it is at rest are shifted to one of the 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 oscillator, which is driven by an oscillation circuit 11, whose frequency is divided by a frequency divider 12, and by a waveform shaper 13 at an appropriate time interval and with an appropriate time width.
Two pulses with a 180° phase difference are formed.

An example of this is a pulse of 7.8m _sec 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. 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, the other inverter 15
When a similar signal is applied to the input terminal 17 of the arrow 1
Current flows through 9 symmetrical routes. That is, by applying signals alternately to the input terminals 16 and 17 of both inverters, the current flowing through the coil 4 can be alternately reversed. Specifically, the current flowing through the coil 4 can be alternately reversed, and specifically, the current of 7.8 m _sec is reversed alternately every second. It can be passed through the coil 4. 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 7 can be rotated 180 degrees by repulsion and absorption with the magnetic poles of the rotor 1. . And the rotation of this rotor 1 is the intermediate wheel 6
is transmitted to the fourth wheel 6, and then to the third wheel 8,
The calendar mechanism is transmitted to the second wheel 9, and further to the cylinder pinion and hour wheel (not shown), and the hour hand, minute hand, second hand,
Activate an indicating mechanism consisting of a calendar or the like.

Since the step motor shown in FIG. 1 almost satisfies the performance requirements for electronic wristwatches, it has been widely used in conventional electronic wristwatches. However, as mentioned above, this step motor drive method is always driven by constant drive pulses, so when a disturbance is applied to the watch body, for example when operating a calendar mechanism, a load is applied to the rotor to prevent its operation. affect. Therefore, driving energy has been applied to ensure sufficient operation even under these expected loads. However, this kind of load is applied to the watch body only 5 times in a 24-hour day.
~6 hours, and for the remaining 17 to 18 hours it operates with almost no load. Therefore, at least a portion of the driving energy at this time is wasted.

The present invention aims to reduce this wasteful current and reduce the power consumption of the step motor, and a driving method for this purpose 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,
Due to the internal drop caused by the impedance of the MOS transistor 15, 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. The special feature of this current waveform 20 is that, as is clear from the figure, 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 coil is caused by the rotation of the driven rotor. This is because an induced current flows through the coil, and the dent in the current waveform is the part where the induced current is maximum.This condition is met 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 ₂
It is time to pass through the section).

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 system of the present invention focuses on this drawback and is designed to always drive with the lowest power consumption. An example of the circuit 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 12 shown in FIG. 2 are omitted because they are the same in the present invention.
A waveform shaping circuit 13 is also used.

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 m _sec 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, a current flows in the coil 4 from the terminals 4a to 4b, and as described above, the waveform of the current flowing in the coil is observed as shown in FIG. 6C of the MOS transistor. When this current waveform is alternately selected between terminals 4a and 4b by an analog switch constituted by a transmission gate and amplified by a CMOS amplifier 30 via a capacitor 29, it becomes as shown in FIG. 6E.

This figure 6E shows the current waveform increasing from LOW.
When it goes to HIGH and decreases, it goes from HIGH to LOW, and when it increases again, it goes from LOW to HIGH, resulting in a pulse that follows the increase and decrease of the current, and immediately after passing the dent in the current waveform mentioned above, if you cut off the drive pulse at this rising part, As mentioned above, the operation of the rotor is not affected. The output of this flip-flop 31 becomes the signal shown in FIG. 6F _, which is inverted by the inverter 33, and the NAND gate 25 is cut off. Driven by short pulses. 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 terminals 23 and 24 (7.8 m _sec 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.

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 inverter 33 outputs a detection signal according to the current waveform generated in the coil. Note that the detection signal of the inverter 33 is the inverted version of the output F of the flip-flop 31. 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 of the detection circuit (inverter 33 output) becomes L and gate 2
5 and 26 to stop the drive current. As a result, the drive current constantly changes and only the required amount is supplied. Note that the pulse width control circuit is used in combination with the waveform shaping circuit 13 shown in FIG. ing. Further, transmission gates 27 and 28 arranged between the coil ends 4a and 4b and the capacitor 29 constituting the load detection circuit are analog switches, and are turned on and off by signals A and B from terminals 23 and 24. Since the OFF state is controlled, the conductive state is maintained while the driving current is applied and an induced current for detection is generated, and subsequently the non-conductive state is maintained. As a result, the induced current generated in the coil when the drive current is not applied does not flow to the detection circuit at all, which is advantageous in terms of current consumption. Of course, it is more preferable to use the amplifier 30 as a clock gate type to achieve lower power consumption.

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) and there is no loss when inserting a resistor.
Furthermore, since the detection circuit, control circuit, etc. are all composed of C-MOS, they are identical to other clock circuits, such as crystal oscillation circuits, frequency dividing circuits, motor drive circuits, etc.
Can be configured with IC. In other words, it can be realized by making use of the C-MOS and IC technologies that have been conventionally used in clock circuits.

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 detects the induced current as a load. Since it is equipped with an analog switch that determines the operating state and non-operating state, it 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 impact, etc. Particularly in a vibrating circuit for a wristwatch in which the braking force of the rotor is achieved by short-circuiting both ends of the coil, this effect is large and there is a risk of unnecessary current consumption in the load detection circuit. However, according to the present invention, the analog switch connected between the end of the coil and the load detection circuit is kept inactive except when a pulse signal is applied and the load is being detected, so all of the above-mentioned problems are solved. Therefore, according to the present invention, a step motor drive device with extremely low power consumption can be provided.

As described above, the present invention provides a rational method for driving a step motor, and as a result, the life of an electronic wristwatch can be extended or the electronic wristwatch can be made smaller, and its industrial value is great.

[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. 1... Rotor, 2, 3... Stator, 4...
Coil, 10... Crystal oscillator, 25, 26...
NAND gate, 30...amplifier, 34, 35, 3
6...Current waveform.

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 wristwatch 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 connected between the frequency divider and the drive circuit, and a pulse width control circuit configured to form a drive pulse with a large pulse width during heavy loads using the output of the load detection circuit; An electronic wristwatch comprising an analog switch that is connected between a load detection circuit and becomes non-conductive after a load is detected by a pulse signal synchronized with the drive pulse.