JPS5937680B2 - step motor - Google Patents

Description

[Detailed description of the invention] The present invention relates to a step motor for an electronic watch.

An object of the present invention is to realize an electronic wristwatch that is easier to use or an electronic wristwatch with expanded functionality by providing a drive electronic circuit that allows the rotor of a step motor to rotate in both forward and reverse directions. Electronic watches are ultra-compact electronic devices, and the batteries used are also very small, and there is a demand for the watch to operate for as long as possible with this small battery, so each device that makes up the watch is extremely Must operate with low power consumption.

In fact, one of the major pillars of technological innovation in electronic watches is reducing the power consumption of the watch body. The step motor, which is the electromechanical conversion mechanism of electronic wristwatches, is no exception to this example, and efforts have been made to improve efficiency and reduce power consumption. By the way, the basic function of a watch is to be able to read the time by rotating the hands in a fixed direction as time passes, so you can use a step motor that rotates in a fixed direction even if it is not a step motor that rotates both left and right. That was enough.

In fact, as mentioned above, there is a strong demand for a step motor that operates with as little power consumption as possible even when rotating only in a fixed direction. Therefore, a step motor that can rotate in both directions has not been put into practical use at all. Atodea has been proposed as a motor for electronic wristwatches that can rotate in both directions.

However, these methods are unrealistic and have complicated structures, require extremely high processing precision, and consume large amounts of power. In addition, with the recent spread of electronic wristwatches, the demand for dual-rotation motors has gradually become stronger due to demands for greater convenience, ease of use, and expanded functionality.
The present invention satisfies such demands and provides a new bidirectionally rotating step motor that does not have the defects of the conventional motors.

That is, a conventional one-way rotation motor, such as a step motor with high efficiency and low power consumption, can be rotated in the opposite direction by using a special drive circuit in which the drive circuit is slightly modified without changing the motor mechanism. Therefore, it is possible to achieve dual rotation only by changing the electronic circuit without sacrificing the conventional features such as high efficiency and low power consumption, and without changing the special structure. The present invention is applicable to step motors. The present invention will be explained below, but first an example of a step motor for an electronic wristwatch and a conventional idea for making it rotate in both directions will be explained.
Next, embodiments of the present invention will be described in detail.

Figure 1 shows an example of a step motor for an electronic wristwatch.
In the figure, 1 is a permanent magnet rotor that is magnetized with two poles in the radial direction.
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 stators 2 and 3 have circular arc portions 2a and 3a eccentrically opposite to each other with respect to the center of the rotor 1 so that the rotor 1 can rotate in a fixed direction. S) The position is shifted to one of stators 2 and 3. A step motor having this structure has been put into practical use for some time and has been driven by a circuit as shown in FIG. That is, 10 is a crystal oscillator, which is driven by an oscillation circuit 11. Its frequency is divided by a frequency divider 12, and a waveform shaper 13 generates two pulses having different phases at an appropriate time interval and an appropriate time width. molded. A typical example is two 7.8m pulses every 2 seconds, and this pulse will be explained below. This pulse is input to drivers 14 and 15 composed of CMOS inverters, and the output thereof is supplied to terminals 4a and 4b of the coil 4. Figure 3 is a detailed diagram of this driver section, and one inverter 1.
When the pulse 18 shown earlier is applied to the input terminal 16 of the inverter 4, a current flows as shown by the arrow 19, and when a pulse is then applied to the input terminal of the other inverter 15, the current flows in a route symmetrical to the previous one. flows. That is, by alternately applying pulses 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 for 7.8 msec, which is alternately reversed every second. It can be passed through the coil 4. With such a drive circuit, the stators 2 and 3 of the step motor shown in FIG.
S poles are generated alternately, and the rotor 1 can be rotated 1801 times 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, hour wheel, and calendar mechanism (not shown).
Operates the indicating mechanism consisting of the hour hand, minute hand, second hand, calendar, etc. This step motor has been used for a long time as a conversion mechanism for electronic watches, but optimization of the motor shape (inner diameter of the stator, eccentricity x, rotor diameter, etc.)
Improvements have been made through analyzes of motor operation and magnetic circuits, and efforts have been made to improve conversion efficiency and reduce power consumption.

Further, these improvements have been made to motors that rotate only in a fixed direction, and studies have been made to make it as easy as possible to rotate in a fixed direction. Therefore, it is impossible to reverse rotation using a normal driving method, and it has been thought that it is impossible to achieve both rotations with a single step motor of this type. As mentioned before, the stable position of the rotor 1 changes depending on the direction of eccentricity of both stators 2 and 3, and therefore the rotation direction is determined. If the eccentric direction is opposite to this, it will rotate in the direction opposite to the arrow. One of the conventional ideas for bidirectional rotation with this type of motor is to utilize this. That is, the eccentric direction of the stators 2 and 3 is changed by operating from the outside of the watch body, thereby allowing the rotor to rotate in both directions. Of course, if such a configuration is adopted, the motor can theoretically be rotated in both directions. However, in order to obtain high efficiency and low power performance, the amount of eccentricity of the stators 2 and 3 should be around 50μ, and the tolerance thereof is about 10μ. Because this requires high precision, the stator must be processed extremely carefully, and it cannot be achieved unless it is securely fixed to the main plate during assembly.With a configuration in which the stator is rotated by external operation, watch manufacturers This is impossible even with precision processing technology. Other conventional ideas for dual-rotation step motors include a step motor with two drive coils, one for forward rotation and one for reverse rotation, or a step motor with two drive coils, one for forward rotation and one for reverse rotation. Some have two sets of stators.

However, even in these watches, the size of the step motor cannot be ignored, and the coil in particular is extremely large. Therefore, there is a strong demand for miniaturization of motors, and under these circumstances, a motor requiring two drive coils is completely impractical. The ideas for dual-rotation step motors that have been proposed in the past have been briefly described above, but all of them are difficult to realize for electronic wristwatches and are no more than mere ideas. The present invention provides a dual-rotation motor that is free from such drawbacks and can be easily implemented.The present invention also provides a dual-rotation motor that is free from such drawbacks and can be used to analyze the operation of the rotor without changing the structure of the motor at all in the case of the step motor shown in Fig. 1. Among them, a reversible drive system was discovered.

Therefore, a dual-rotation motor can be realized by simply adding a few new drive circuits. An embodiment of the present invention will be explained in detail below.

FIG. 4 shows an example of a dual-rotation drive circuit for a step motor according to the present invention, and FIG. 5 is a time chart thereof.

In the figure, 20 is an oscillation circuit, and 21 is a frequency dividing circuit. The outputs of the NANDGATEs 22, 23, 24, and 25 are clocks for generating pulses for driving the motor, and are obtained by combining the outputs of the frequency dividing circuit 21. Please note that NA
NDGATE22 is the first pulse for reverse drive, NA
NDGATE23 and 24 also apply the second pulse to NDGATE23 and 24.
ANDGATE 25 is a gate for generating a pulse for normal rotation drive, and generates a clock pulse delayed by, for example, several Msec (Tl, T2, T3, T4) with respect to the falling edge of a one second signal.

At this time, day reflex flip-flops 26, 27, 28, 2
9 delays the input 1-second signal by Tl, T2, T3, and T4, and outputs a pulse with a width T1 at the output of the gate 30 (Fig. 5A), and a pulse with a width T3 at the output of the gate 31.
A pulse of -T2 and T3' is generated (FIG. 5B), and a pulse of width T4 is generated at the output of gate 32. Note that 33 is a forward/reverse rotation switch; when this is open, forward rotation and reverse rotation are performed.
When closed, it is driven in reverse. First, let us start with the case of open, ie, normal rotation drive. At this time, the output of the switch 33 is High, so the gate 36 is open and the output signal of the gate 32 is passed through, and the gates 34 and 35 are closed.

Therefore, the output of this gate 36 is divided in %Hz and becomes 0RCA.
At the outputs D and E of the TEs 39 and 40, signals D and E in FIG. 5 are obtained. This is input to driver inverters 42 and 43, and their outputs are connected to terminals 41a and 41b of the drive coil 41 of the step motor. This is essentially the same as the drive signal for the conventional step motor shown in FIGS. 2 and 3. That is, a pulsed current having a pulse width of T4 and inverted every second is supplied to the coil 41, which is the normal operation of the step motor. Next, switch 3
In the case of reverse drive when the switch 3 is closed, the output of the switch 33 becomes LOW, so that the gates 34, 35, and 36 are opened and the gate 36 is closed. Therefore NANDGA
Outputs A and B of SE3O and 3l are distributed at %Hz through gates 34 and 35, and the signals shown in FIG. 43, and its output is connected to terminals 41a and 41b of the drive coil 41. At this time, first, a pulse current with a width T1 flows from the terminal 41a of the coil 41 to the terminal 41b, and then a pulse current with a width T'3 flows in the opposite direction (from the terminal 41b to the terminal 41a).
flow to). Then, one second later, the pulse current of width T1 changes from 41b to 41a, and the pulse current of width T'3 changes to 41a.
The flow from a to 41b is repeated thereafter. Tl, T2,
When such a drive pulse with T'3 set at an appropriate value is supplied to the step motor, the rotor rotates in the reverse direction.
The reason for this and the operation of the rotor will be explained using the step motor shown in FIG. The driving pulse width T4 during forward rotation is necessary and sufficient for driving forward rotation, and was set to 7.8 msec in this example. The pulse width T1 is shorter than T4, that is, 7.8 msec, and is set slightly shorter than the operating limit pulse width of the rotor. As a specific example, it is assumed that T1'-3 msec. The rotor receives a driving force in the forward rotational direction by this T1 pulse, but the force is not enough to rotate one step, so the rotor rotates about 40 to 50 degrees and returns to its original position. In FIG. 1, the rotor 1 is located at a neutral point N at a position slightly less than 900 degrees from the static stable position (the direction of the magnetic poles when not driven).
P. There is.

Rourke-11 obtains driving force and returns to this neutral point N. P. If the rotor 1 is overcome, the rotor 1 will operate one step even if the driving force is lost. However, this neutral point N. P. If it cannot overcome this, it will return to its original statically stable position. Driving by the T1 pulse results in this latter operation. Figure 6 is a diagram showing the operating status of the rotor.
When ec is given, it rotates 180 kW in the forward direction and comes to rest. The mouth is at the neutral point N. when only the pulse of T1 (3 msec) is applied. P. It returns to its original position because it is unable to cross the threshold. By the way, in the drive shown in FIG. 4, following the pulse T1, a pulse with a width T' is applied in the opposite direction to the pulse T1. This pulse is a pulse T, which drives the rotor in the opposite direction when the rotor is slightly operated, that is, when the magnetic pole of rotor 1 reaches the vicinity of the gap between stators 2 and 3. It operates as shown in Figure C, rotates 180 degrees in the opposite direction, and comes to rest. Of course, T2 and T'3 shown in time chart B of FIG. 5 are set appropriately. A specific example is T2ζ4.5msec, T'
3'-4.5 msec. Incidentally, when the rotor 1 is in a statically stable position, it is driven in the opposite direction, but it does not reach the point where it rotates one step. The reason is rotor 1
Since the magnetic fields in the stators 2 and 3 surrounding the rotor 1 are almost parallel magnetic fields, the maximum driving torque is received when the magnetic poles of the rotor 1 are in the gear direction of the stators 2 and 3. Therefore, in the case of forward rotation, the rotor is driven from a static position. As the rotor 1 rotates in the direction of the arrow, it receives a larger torque, so the rotor 1 operates under a larger rotational torque as a whole. On the other hand, even if a drive pulse in the opposite direction is applied, the rotor 1 starts rotating in the opposite direction, but the rotational torque gradually decreases.
It does not complete one step of rotation and returns to its original position.
On the other hand, according to the drive method of the present invention, first the rotor 1
When the stators 2 and 3 are operated to near the gap, a driving pulse in the opposite direction is applied, so that a larger rotational torque is received than when the stators are in a static stable position, making it possible to rotate in the opposite direction. As is clear from FIG. 5, a period during which no pulse is applied to the drive coil may be provided between the first pulse T1 and the second pulse T'3. The rotor has inertia in the forward rotation direction due to the first pulse T1, but the first pulse T1
By providing a period in which no pulse is applied between the pulse and the second pulse, this inertia in the normal rotation direction is reduced, and the second pulse T
'3 allows a larger rotational torque in the opposite direction to be obtained, and reliable operation can be expected. Here, we will discuss the performance of the step motor 1 during reverse drive, which was obtained in this way with the step motor 1 shown in FIG.
6 msec, T'3: 3.5 to 6 msec, and the output torque during reverse rotation was % to % of the output torque during forward rotation. Also, the operating voltage range is slightly narrower than that for forward rotation. In this way, the performance is worse when rotating in reverse than when rotating forward. However, when using this as an electronic wristwatch, the step motor 1 rotates in the normal direction during normal hand movement, and rotates in the reverse direction when performing a special function or operation. At this time, when rotating in the forward direction, the watch is subject to all conditions (e.g. extremely low temperatures, in a magnetic field, strong disturbances, etc.)
It is necessary for the motor to operate normally, but when rotating in reverse, there is no need to take as much consideration under such harsh conditions. Therefore, sufficient performance is required when rotating in the forward direction, but it only needs to operate under normal conditions when rotating in the reverse direction.In this sense, the forward and reverse rotation drive system of the present invention is most suitable as a step motor for an electronic wristwatch. It has been confirmed that the drive method of the present invention can be applied not only to the step motor shown in FIG. 1, but also to all step motors that have been put into practical use for electronic wristwatches.

However, in that case, the constants of the width of the driving pulse and time interval (Tl, T2, T'3, etc.) described above vary slightly for each individual motor. That is, although the motor shown in Figure 1 has a rotor magnetized with two poles, it can also be applied to a six-pole rotor, and also to a step motor in which the rotor and stator are magnetically engaged in the axial direction. It can also be applied to a type of step motor that is surrounded by a coil.

In addition, all of these motors are inverted pulse motors in which the driving current alternately flows in the opposite direction for each step, but even in the case of step motors in which the driving current always flows in the same direction, the second pulse T' during reverse driving is normally driven. Reversal is possible by flowing in the opposite direction. Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described herein.

The dual-rotating step motor is expected to be used in various ways for electronic wristwatches. And it is possible to apply the present invention to these. For example, when setting the time,
When setting the second hand to the hour, if the second hand is past the hour,
This can be easily done by reversing the step motor and moving the second hand back. At this time, the correction can be made instantaneously by driving at a faster step number than when the needle is normally incorrect (generally 1 second steps). Although the structure is slightly different from the embodiment shown in FIG. 4, it goes without saying that it is possible with simple changes. Furthermore, various types of time adjustment, especially seconds adjustment methods, using dual rotational drives are conceivable, and the present invention can be applied to these.
It goes without saying that the dual-rotation step motor is also effective when adding functions such as multi-time and remaining time display to an electronic wristwatch.

Furthermore, the present invention can be applied not only to electronic wristwatches but also to electronic devices such as general measuring instruments.

[Brief explanation of drawings]

FIG. 1 shows an example of a step motor according to the present invention. FIGS. 2 and 3 show a conventional step motor drive circuit. FIG. 4 shows an embodiment of the dual-rotation drive circuit of the present invention, and FIG. 5 shows its time chart. FIG. 6 is a diagram showing the operation of the motor. 1...Rotor 2
, 3... Stator, 4... Coil,
10... Time standard oscillator, 11... Oscillation circuit, 12... Frequency dividing circuit, 13...
Waveform shaper, 14, 15...Inverter, 26
~29...Delay flip-flop, 33.
・・・・・・Choice switch.

Claims (1)

[Claims] 1. A step motor consisting of a rotor, a stator, and one drive coil, which provides a static stability point to the rotor due to the asymmetry of the stator.
a forward rotation drive circuit for supplying relatively short pulses of msec or less to rotate the rotor in a predetermined direction; and a first drive circuit that is set slightly shorter than the operating limit pulse width of the rotor and drives the rotor in the forward rotation direction. and a reversing drive circuit for subsequently supplying a second pulse of opposite polarity to rotate the rotor in a direction opposite to the predetermined direction; A step motor characterized in that a period in which no pulse is applied to the drive coil is provided between the first pulse and the second pulse.