JPH0221294A - How to drive an electronic clock - Google Patents

Abstract

PURPOSE:To achieve a lower power maintaining performance by employing a bipolar rotor type step motor as electromechanical conversion mechanism to improve the driving of the step motor. CONSTITUTION:A driving circuit of an electronic timepiece is made up of two P-channel MOS transistors 15 and 16. Gates of the respectively gates serve as input terminals 17, 18, 19 and 20 and when a rotor is not driven, the input terminals are all at a low level. Of course, no current flows through a coil 4. When the input terminals 17 and 19 are set high, current flows in the route indicated by the arrow 21. Then, when the input terminal 19 alone is returned to low, the current is shut off. Here, the supply of current is limited to the start of the rotor 1 and before and after the passage of a magnetic pole of the rotor 1 through a clearance between two stators 2 and 3 and otherwise, the current is cut off thereby achieving a lower power with a driving force working effectively on the rotor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic timepiece, and more particularly to improving a method for driving a step motor, which is an electromechanical conversion mechanism thereof.

Since so-called quartz wristwatches, which use a quartz crystal as the time standard, have been put into practical use, numerous technological innovations and improvements have led to increased production volume and lower prices, and these quartz wristwatches have now become widely used. Ta. However, in analog quartz wristwatches with pointer displays, the electromechanical conversion mechanism is clearly lagging behind technological innovations related to crystal oscillators and electronic circuits. In particular, the electromechanical conversion mechanism now consumes most of the power consumed by the entire watch, and the lifespan of quartz watches has been lengthened, or watch bodies have become smaller and thinner due to the miniaturization of batteries. This has become a major bottleneck.

In order to improve this point, the present invention employs a two-pole rotor type step motor as an electromechanical conversion mechanism, and improves the driving method of this step motor to reduce power consumption while maintaining performance.

FIG. 1 shows a two-pole low-coupled step motor, and this step motor has been in practical use for some time, and the present invention relates to a method of driving this step motor.
First, an overview of this step motor and a conventional driving method will be described, followed by a detailed description of the new driving method of the present invention.

In Fig. 1, 1 is a permanent magnet type rotor magnetized into two poles, and the stator 2.
are arranged facing each other, but these stators 2.
3 are each connected to a yoke 5 around which a coil 4 is wound to form a set of stators. The stator 2.3 has circular arc portions 2a and 3a eccentric to the center of the rotor 1 so that the rotor 1 can rotate in a fixed direction, so that the magnetic pole (N and S) positions when the rotor 1 is at rest are adjusted to the stator. It is shifted to one side of 2.3. Terminal 4a of coil 4
, 4b, the rotor 1 rotates 180°
Although the rotation of the rotor 1 is not shown in the drawings, it is configured as an electronic wristwatch that operates an indicating mechanism consisting of a clock, a minute hand, a second hand, a calendar mechanism, etc. through a gear train to display the time.

Figure 2 shows the conventional drive circuit for this step motor, and Figure 3 shows the conventional drive circuit for this step motor.
In the figure, the input signal 66.7 is a CMOS inverter whose output is connected to the terminals 4a and 4b of the coil 4. The input terminal 8.9 of this inverter 6.7 has a third
Signals as shown in Figures (A) and (B) are applied. Now, if the signal at input terminal 8 goes from Low to High, the arrow IO
When the other input terminal 9 becomes High, a current flows symmetrically to this. Two input terminals8.
9 alternately becomes High every second, and accordingly, a reverse pulse current flows through the coil 4, the direction of which changes every second. Therefore, stators 2.3 alternately N[! , the rotor 1 is energized to the south pole, and the rotor 1 is energized to the south pole.
It will be understood that the rotation is 80 degrees.

Figure 4 shows the waveform of the current flowing through the coil when rotor 1 is driven.The characteristic of this waveform is that there is a part in the middle where the current value decreases, which occurs when rotor 1 rotates. This is because the magnetic flux in the coil 4 changes due to the magnetic poles of the rotor 1, causing a reverse induced current to flow through the coil. It is time to pass through the gap between 3. Therefore, section 11 in FIG.
If you observe the operation of this step motor in the section until it starts and the magnetic pole of rotor 1 passes through the gap of stator 2.3, you will see that it operates sufficiently in section 11 just to operate rotor 1. . i.e. rotor 1
If the motor is started and driven until it passes through the gap of the stator 2.3, it will rotate by one step due to inertia and attraction with the stator 2.3. However, when a load is applied to the rotor 1, it takes time to pass through this gap, so the drive section 12 is provided as a margin to withstand the expected load. However, this margin section 12 has a small amount of reverse induced current, and as can be seen from the figure, the current consumption in this section is very large.

This is because a driving method is used that ignores the operation of the rotor 1 and performs a constant drive.The present invention takes the operation of the rotor 1 into account and reduces the current consumption in the wasted portion. , which provides a driving method that can reduce power consumption while maintaining performance, and examples thereof will be described in detail below.

FIG. 5 shows an embodiment of the drive circuit of the present invention, and FIG. 6 shows the large-power signal waveform and the current waveform flowing through the coil. The drive circuit in Fig. 5 has two P as shown in the figure.
It consists of a channel MO5I-Langius star 13.14 and two N-channel transistors 15.16. The gate of each transistor is the input terminal 17.1
8, 19, and 20, and these input terminals 17, 18, 19, and 20 are all LOW when the rotor is not driven. At this time, of course, no current flows through the coil 4.Now, when input terminals 17 and 19 are set to Hlgh, a current flows along the route indicated by the arrow 21 in the figure. Next, input terminal 19
If you return it to Low, there will be no route for current to flow,
The current is interrupted. Therefore, when the intermittent drive signals shown in FIGS. 6(A) and 6(B) are applied to the input terminals 17 and 19, respectively, the current flows along the route of the arrow 21 only in the high sections 22, 24, and 26 of FIG. 25, the current is cut off. However, rotor 1 is driven and coil 4
A current as shown in FIG. 6(C) flows through. In other words, current flows only when rotor 1 is started, before and after the 6R pole of rotor 1 passes through the gap between both stators 2 and 3, and in the margin part to withstand the load torque, and in other parts, current flows. By cutting, the driving force can be effectively reduced to 1.
Even if the current is cut in this way, there is almost no deterioration in performance such as the operation of the rotor l or the output torque.6 In other words, the conventional drive method that provides a constant driving force is Since there were parts of the rotor 1 that were loaded with driving force that was useless for operation, a driving method that only applies driving force to the parts where the driving force is sufficient for the operation of the rotor 1, as in this example, is optimal for a step motor. It can be said that this is the driving method.

As above, the present invention has been explained in detail in one embodiment, but the gist of the present invention is as described above (the driving force is applied only to at least three parts where the driving force sufficiently acts on the rotor, and the other parts are provided with driving transistors). 6 The present invention employs a drive system suitable for step motors and achieves low power consumption while maintaining performance. This means that the lifespan of an electronic watch can be extended or that the size of the electronic watch can be made smaller, and its utility value is great.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a step motor for electronic watches. Figure 2 shows a conventional drive circuit for a step motor. FIG. 3 is a second input signal waveform diagram. FIG. 4 is a waveform diagram of the current flowing through the coil due to the drive circuit shown in FIG. FIG. 5 shows a step motor drive circuit of the present invention. FIG. 6 is an input signal and current waveform diagram of FIG. 5. ■ ・ ・ ・ 2, 3 ・ 4 ・ ・ 13-16 21 ・ ・ ・ ・Rotor, stator, coil, MOS transistor, current route and above Applicant Seiko Epson Corporation Representative Patent attorney Kizobe Suzuki (and 1 others) Figure 1 Figure 2 Figure 3 Figure 4■ Figure 5

Claims (1)

[Claims] A drive circuit operated by a clock signal, at least a coil, a stator, and a permanent magnet rotor,
In the method for driving an electronic timepiece including a step motor driven by the drive circuit, the drive circuit for supplying a drive current to the coil has two first-type transistors connected to a first potential; A bridge circuit is configured in which a second type transistor is connected to a potential of , and both ends of the coil are connected to a series connection point of the first type transistor and the second type transistor, respectively, and the four The rotor is driven by selectively conducting a transistor by a drive signal and supplying a drive current to the coil, and the drive is applied to one of the transistors through which the drive current is flowing when the rotor is driven. A method for driving an electronic timepiece, characterized in that the transistor is intermittently cut off by using at least three intermittent signals.