Electric Timepiece

Abstract

An electric timepiece wherein a mechanical vibrator is synchronized with a signal which compares signals of a relatively high-frequency time standard with a relatively low-frequency mechanical vibrator. A first embodiment applies nonlinear characteristics of frequency in response to changes in vibrating amplitude of the mechanical vibrator. In a second embodiment, a time standard signal is utilized as a synchronizing signal to control the phase of the input signal for driving the mechanical vibrator and for synchronizing the mechanical vibrator.

Description

DETAILED DESCRIPTION OF INVENTION

The present invention relates to an electric timepiece, and more particularly to an electric timepiece comprising a time-keeping oscillator and a mechanical vibrator which drives the gear train to operate the indicators.

A primary object of the present invention is to provide a high-precision electric watch which is simple in construction and cheap in price, by synchronizing the mechanical vibrator of unstable low frequency with the time-keeping oscillator of high frequency, without using a frequency divider.

A further object of the invention is to provide a high-precision wristwatch controlled by a quartz crystal.

Various types of electric watches are known wherein the balance-spring oscillator of 2.5 Hz. or 5 Hz. is used as time base. However, in these types of watches it is impossible to make the daily rate within 2 seconds.

A watch using, as its time base, a tuning fork which vibrates at several hundred cycles is also known. In these watches the gear train is driven directly by the tuning fork. Though the daily rates of these watches are nearly 2 seconds, it is still impossible to attain a precision of 0.2 second per day or better. This is because the fluctuation of the torque for driving the gear train influences the frequency of the time-keeping oscillator, as the time-keeping oscillator and the oscillator for driving the gear train are the same. Besides, in the tuning fork there exists position error. And if one wants to make the daily rate less than 0.2 second it is necessary to make the resonance frequency of the tuning fork over several kHz. But it is very difficult to drive the gear train directly by a tuning fork having such high frequency.

Quartz crystal watches having quartz oscillator of several kHz. guarantee a daily rate within 0.2 second. Quartz crystal timepieces usually comprises quartz crystal oscillator, frequency divider, motor and gear train. The frequency divider is inevitable for dividing the frequency of the quartz oscillator of several kHz. into the response frequency of the motor, i.e., several Hz. to several 10 Hz.

This invention is particularly characterized in eliminating the frequency divider from quartz crystal timepieces. As a result, it is applicable to wristwatches requiring small space and a watch of low cost can be realized. Besides, a balance-spring oscillator or a synchronized tuning fork can be used instead of motor. As these are conventionally known oscillators which require only small power consumption, they are easy to manufacture it and with low cost. Thus it is very advantageous for making a quartz crystal timepiece compact enough as a wristwatch.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing one embodiment according to the present invention.

FIG. 2 is one embodiment of the block diagram in FIG. 1.

FIG. 3 is a cross-sectional view of FIG. 2.

FIGS. 4 and 5 are electric circuits of the embodiment shown in FIG. 2.

FIG. 6 is a waveform of the embodiment shown in FIG. 2.

FIG. 7 is another embodiment of the block diagram shown in FIG. 1.

FIG. 8 is a cross-sectional view of the embodiment of FIG. 7.

FIG. 9 is a tautochronous curve of the embodiment shown in FIG. 7.

FIG. 10 is a device for protecting the balance from outer disturbance.

FIG. 11 is another embodiment of the block diagram.

FIG. 12 is a frequency-amplitude curve of the tuning fork of the embodiment shown in FIG. 11.

FIG. 13 shows another embodiment of the block diagram.

FIG. 14 is an embodiment using the block diagram of FIG. 13.

FIG. 15 is a waveform of the embodiment shown in FIG. 14.

FIG. 1 is a block diagram showing one embodiment of an electric timepiece according to the present invention. 1 is a relatively high frequency oscillator as the time base. 2 is a relatively low frequency mechanical vibrator, the frequency of which is 1/n(n = integer) of that of said time keeping oscillator. 3 is means for maintaining the vibration of the mechanical vibrator 2. 4 is means for comparing the vibratory phase of the output from the time keeping oscillator 1 with that from the mechanical vibrator. 5 is a device which controls the frequency of mechanical vibrator 2 to be 1/n(n = integer) of that of the time-keeping oscillator 1. 6 is a converter which converts the vibratory motion of the mechanical vibrator into rotary motion to operate the indicators and the gear train. In other words, according to the present invention, the vibratory phase of the output from the time-keeping oscillator having relatively high frequency is compared directly with that from the low frequency mechanical vibrator, the frequency of which is as that of low as the ordinary electric watch and 1/n(n = integer) of that of said time-keeping oscillator, and said mechanical vibrator is synchronized with the time-keeping oscillator.

FIG. 2 is one embodiment according to the invention wherein a balance-spring oscillator is used as the mechanical vibrator.

FIG. 3 is a cross-sectional view of said embodiment.

In FIGS. 2 and 3, 7 is a balance wheel and 8 is a hair spring. Both 7 and 8 form an oscillating system. This oscillating system corresponds to the mechanical vibrator 2 in FIG. 1. Double coil 9 comprising a detecting coil and a driving coil is fixed to the plate 10 and detects the variation in the magnetic flux which passes through the coil. That magnetic flux is generated from the magnets 11 and 12 provided in the neutral point of the oscillation of the balance where the vibration is in static condition. As a result of the flux, the pulsive current is applied to the driving coil. The balance is energized through the electric circuit 13, thus the self-oscillation is maintained.

FIG. 4 is one embodiment of the electric circuit 13. 19 is a detecting coil, 20 a driving coil. This type of electric circuit is well known in the electric timepiece using a balance-spring as mechanical vibrator.

Self-oscillating means comprising double coil 9, magnets 11 and 12 and electric circuit 13 in FIGS. 2 and 3 correspond to the means 3 for maintaining the oscillation in FIG. 1.

14 is a converter which converts the vibratory motion of the balance into rotary motion to operate the indicators. 15 is a part of the gear train 14. 15 corresponds to the converter and gear train 6 in FIG. 1. 16 is a double coil comprising a detecting coil and a control coil which is spaced by .DELTA. from the neutral point of the oscillation. 17 is an electric circuit for comparing the vibratory phase of the balance with that of the time-keeping oscillator. 18 is an input terminal from the time keeping oscillator.

FIG. 5 is one embodiment of an electric circuit 17 in FIG. 2. 21 is a control coil, 23 is an input terminal from the time-keeping oscillator, part A is an amplifier for the detecting signal, part B is a flip-flop which compares the vibratory phase of the output from the time-keeping oscillator with that from the balance. The power source is common with that for the self-oscillating circuit shown in FIG. 4

FIG. 6 shows a waveform of each point a,b,c in FIG. 5. (i) is a waveform of point a, that is an oscillating pulse series from the time-keeping oscillator. (ii) is a waveform of point b, that is pulse series for detecting the vibratory phase of the balance. (iii) is a waveform of point c, that is the electric waveform of the control pulse, the width of which is equal to the difference of vibratory phase between the output from the time-keeping oscillator and that from the balance. The frequency of the balance is compensated by applying the current through the control coil.

If the frequency of the time keeping oscillator is 2.5 kHz., the period of the pulse series of (i) is 0.4 m.sec. And if the frequency of the balance is 2.5 Hz., the pulse period of (ii) is 400 m.sec. As the frequency stability of the balance-spring system is usually less than 2.times.10.sup.- .sup.4, fluctuation of the pulse series is 0.08 msec. With this range, the mechanical vibrator can be easily synchronized. In other words, it is possible to divide it into 1/1,000, for the frequency of the time keeping oscillator is 2.5 kHz. and that of the balance is 2.5 Hz. So a frequency divider is unnecessary.

According to Airy's Theorem, the amount of compensation of the balance is nearly proportional to .alpha./A (A.gtoreq..alpha.). So if the driving pulse is applied far from the center of the balance, the amount of frequency compensation of the balance will become larger. The amount of frequency compensation of the balance in theory is maximum at the maximum amplitude A where the speed of the balance is zero. On the other hand, the larger the control power, the larger the amount of compensation will be. And the control power is determined by the pulse width proportional to the phase difference of vibration and by the peak value decided by the number of turns of control coil 22 and the wire diameter.

Now if the peak value applied on the control coil 22 is equal to the driving peak value applied on the self-oscillating driving coil, the ratio

.tau./.tau..omicron.(where .tau. = control pulse width, .tau..omicron. = driving pulse width)

is the ratio of control power and driving power.

Driving power is inversely proportional to the quality value of balance. The quality value is inversely proportional to the energy loss of the balance. Therefore the amount of compensation of the balance is proportional to:

l/Q.sup. . .tau./.tau..omicron..sup.. .alpha./.LAMBDA.

From the calculation, the proportional constant 1/2 is obtained. Therefore the variation of the frequency of the balance is:

.DELTA.f/f= 1/2 Q.sup. . .tau./.tau..omicron..sup.. .alpha./.LAMBDA.

The ordinary value of the electric timepiece using the balance as the mechanical vibrator is:

.tau..omicron..apprxeq.5msec

Q.apprxeq. 100

Therefore, supposing that .alpha./.LAMBDA.=1/2 and .tau.=0.4 m.sec.(2.5kHz.):

.DELTA.f/f= 2.times.10.sup.- .sup.4

If the peak value of control coil is twice as much as that of the driving coil, the frequency range for synchronization is as follows:

.DELTA.f/f=4.times.10.sup.- .sup.4

This value corresponds to 35 seconds of daily rate. With this value it is easy the arrangement to a practical system.

The double coil 16, electric circuit 17 for comparing the phase difference of the vibration and the input terminal 18 in FIG. 2 correspond to the comparing means 4 and the control means 5 in FIG. 1 respectively.

The magnets 11 and 12 in FIGS. 2 and 3 pass over the controlling coil in the double coil 16 four times in one oscillation when the amplitude of the balance is above about 240.degree.. By selecting a triggering level of the transitor, the detection only once in one oscillation can be easily gained. We name the control system shown in FIGS. 2 and 3 "the phase-controlling system."

FIG. 7 is the other embodiment according to the invention wherein a balance-spring oscillator is used as a mechanical oscillator.

FIG. 8 is a sectional view of FIG. 7.

The difference from FIG. 2 is that the detecting coil for controlling and that for self-oscillation are the same, and that the control pulse is added at the neutral point of the balance where vibration is in static condition.

Generally, by adding the power at the neutral point of the oscillation, energy can be given to the balance to change the amplitude without causing variation in the frequency.

In contrast with this, adding the power to the balance at the maximum amplitude, the variation of the frequency is largest but energy cannot be given to the balance.

Therefore the coil 24 is a triple one and the detecting coils are included both in the self-oscillating electric circuit 25 and in the electric circuit 26 for comparing the phase of vibration.

An iron piece 27 is secured to a member made of Bakelite having weak magnetic permeability and also weak specific electric conductivity at the opposite position to the neutral point of oscillation. As a result, the tautochronism shows the characteristic as shown in FIG. 9 such that the watches lose abruptly if the amplitude of the balance increases. As the magnets 29,30 and the iron piece 27 act with each other at an amplitude of about 180.degree., the tautochronous curve as shown in FIG. 9 can be obtained.

In order to explain this control system it is supposed that in FIG. 9, the frequency of 1/ n(n:integer) of the time keeping oscillator equals to that shown by the dotted line crossing a point Q.sub.0, and further the pulse width of control as shown in FIG. 6 (iii) equals just a half of the period of the time-keeping oscillator pulse and under this condition the amplitude of the balance is just 207.degree. .

Now, if the watch loses due to disturbance, as can be seen in FIG. 6, the detecting pulse (ii) generates later and so the controlling pulse (iii) becomes smaller than in the steady state mentioned before. Therefore the energy to be added to the balance decreases and the amplitude of the balance becomes small. Then as can be seen from the tautochronous curve in FIG. 9, the operating point moves from the point Q.sub.0 to Q.sub.1 and the watch gain abruptly till the next detecting pulse (ii) generates and try to recover its time delay.

If the loss to be recovered is smaller than that due to disturbance, the width of the next control pulse is smaller than that in steady state but larger than this one. Therefore the operating point moves to the point Q.sub.2 between Q.sub.0 and Q.sub.1 , the watch gains further till the next detecting pulse (ii) generates and try to recover its time delay.

On the other hand, if the loss to be recovered is larger than that due to the disturbance, the watch gains and the width of the next control pulse is larger than that in the steady state and the energy to be added to the balance increases more than that in the steady state and the amplitude of the balance also increases. Now the operating point moves to the point Q.sub.3 and the watch loses till the next detecting pulse (ii) generates and try to make the difference from the standard equal to zero.

Repeating the above-mentioned operations, the operating point travels to the point Q.sub.0 and finally settles there. If the watch gains due to the disturbance, the operating point also settles on the point Q.sub.0 finally.

The frequency of the balance is synchronized with that of the time keeping oscillator by maintaining the operating point Q.sub.0 against disturbance and controlling the amplitude constant, at about 207.degree.. In this case, the efficiency of the control depends on the product of the gradient of the tautochronous curve and the control power. According to the result of an experiment, the frequency range of synchronization of about 30 seconds in daily rate could be obtained by using a time keeping oscillator of 2 kHz. Therefore it is understood that this system is easy for application.

The characteristic of this system is to control the frequency of the balance at 1/ n(n: integer) of that of a time keeping oscillator by giving a nonlinear characteristic to the balance and keeping the oscillation of the balance always constant. We name this "Amplitude-controlling system."

Since the frequency of the balance shown in the above description as an example of the mechanical vibrator is extremely low compared with other mechanical vibrators wristwatches using the balance are apt to undergo disturbance.

In FIG. 10, in order to eliminate the influence of disturbance, two balances shaped into wheels form in their outer peripheries engage each other. As the rotary direction of the two balances is the same for the disturbance, if the moment of inertia and gear ratio of the two balances are properly selected respectively, the influence of disturbance is absorbed by each other. In this manner, the condition that there is no disturbance can be produced. Therefore concerning the balance, it is not necessary to pay attention to a large shift of phase owing to some disturbance shocks. A tuning fork having a frequency of several hundred Hz. may be used as a mechanical vibrator 2 in FIG. 1.

FIG. 11 shows the amplitude-controlling system applied to a tuning fork. This control device comprises the tuning fork 31, magnets 32,33 fixed to said tuning fork, coils 34,35 which act with said magnets, electric circuit 36 for self-oscillation of the tuning fork in which the voltage of the detecting coil forming a part of coil 34 is used as the input and the coil 35 is used as a driving coil, and electric circuit 38 for controlling the tuning fork by supplying an electric current to the controlling coil forming a part of coil 34 comparing the input 37 from a time-keeping oscillator with that from said detecting coil. In this case, the frequency of the tuning fork is also synchronized with a time-keeping oscillator in the same manner as the balance. The tuning fork has a nonlinear characteristic owing to the action of the other magnet 39 fixed to said tuning fork and the iron piece 40 secured on the baseplate.

FIG. 12 shows said nonlinear characteristic, and and a solid line being the tautochronous curve. A mixed line shows the frequency-amplitude curve of the tuning fork exciting. A dotted line shows the frequency of 1/ n(n: integer) of that of a time-keeping oscillator. Owing to the same operation as in the case of the balance, the amplitude of the tuning fork is kept constant. The magnet 39 may be used with the magnet 32 or the magnet 33. The process that the oscillation of the tuning fork is transmitted to the gear train and the indicators through the click 41 and the ratchet wheel 42 is exactly the same as conventional tuning fork watches. A converter such as a magnetic escapement may be used. When the tuning fork is used as a mechanical vibrator, the following characteristics can be found. First, there is no influence of disturbance, for the frequency of the tuning fork is about 400 Hz. Second, the mechanical vibrator can be easily controlled, for the dividing ratio of the frequency of the tuning fork and a time-keeping oscillator having the frequency of several kiloHertz becomes small.

FIG. 13 shows a block diagram of the other examples according to the present invention. The difference from FIG. 1 is that the comparing means, the operating means for self oscillations and the controlling means are united as shown 45. 43 is a time keeping oscillator. 44 is a mechanical vibrator having the frequency of 1/ n (n: integer) of that of a time-keeping oscillator 43. 46 is a converter and gear train through which the vibration of the mechanical vibrator 44 is transmitted to the indicators.

FIG. 14 shows one embodiment of FIG. 13. The voltage induced in a detecting and driving coil which interacts with the magnet 48 fixed on the tuning fork 47 is fed back to the base 52 of transistor 51 through the transformer 50. As the signal from a time-keeping oscillator has been added to the base 52 from the terminal 53, when the sum of said voltage and said signal attains the trigger level, the transistor is switched on and the current is applied to the coil 49. When the current begins to flow, it is applied increasingly owing to the feedback of the transformer 50 during the time of pulse width decided from the electric circuit.

FIG. 15 (1) shows the induced voltage wave form of the coil 49. Actually at driving the waveform is varied by the driving current, but for easier understanding the waveform at nondriving is shown here. This is not essential for the explanation of this phenomenon. The same may be said of (iii). Next (ii) is a signal from a time keeping oscillator. (iii) is a base waveform of the tuning fork at nondriving, which is the sum of (i) and (ii). Taking the trigger level on the position shown by the mixed line, the driving waveform is as shown in (IV). The pulse width .tau. is not changed as before mentioned, but it can be seen that the deviation between the neutral point of oscillation and that of the driving pulse changes according to the difference between the phase of vibration of the tuning fork and that of the time-keeping oscillator. The energy to be added to the tuning fork is changed according to the phase of the tuning fork when the driving pulse is added. The interaction between the magnet 54 secured on the tuning fork and the iron piece 55 fixed to the baseplate shown in FIG. 14 can give a nonlinear characteristic as shown in FIG. 12 to the tuning fork. So the frequency of the tuning fork can be controlled to be 1/ n(n : integer) of that of a time-keeping oscillator by keeping the amplitude constant, cooperating with the energy change before mentioned.

The characteristic according to this method is to unite the comparing means, self-oscillating driving means and control means and to make the whole composition very simple. According to the results of an experiment, when the crystal oscillator of 16 kHz. is used as a time-keeping oscillator and the tuning fork of 400 Hz. is used as a mechanical vibrator, the frequency range of synchronization, 7.times.10.sup.- .sup.4 Hz. corresponding to about 1 minute of daily rate could be obtained.

According to the present invention, a mechanical vibrator having a relatively low frequency such as the balance and the tuning fork etc., can be controlled directly by a time-keeping oscillator having a relatively high frequency such as a crystal oscillator of several kiloHertz. Thus it is not necessary to provide a divider. In this manner, we can obtain electric watches having simple constructions with low cost. Further the production of high-precision watches has been made possible by the adoption of a high frequency time-keeping oscillator. For a high frequency time-keeping oscillator has a high accuracy in general, for example, the daily rate of 0.2 second can be obtained by the crystal oscillator of several kiloHertz.

Claims

What is claimed is:

1. An electric timepiece comprising a time standard oscillator having a relatively high frequency, a mechanical vibrator having a frequency of about 1/ n(n=an integer) of said time standard oscillator; means for sustaining the oscillation of said mechanical vibrator; an indexing mechanism; means for transmitting the oscillation of said mechanical vibrator to said indexing mechanism; means for directly comparing the phase of said time standard oscillator with that of said mechanical vibrator to produce an output signal proportional to the difference therebetween; control means for controlling the frequency or the phase of said mechanical vibrator in response to said output signal of said comparing means for sustaining the frequency of said mechanical vibrator at 1/ n of the frequency of said time standard oscillator, said control means being adapted so that the magnitude of the input energy supplied to said mechanical vibrator is changed in response to said output signal; and permanent magnet means positioned adjacent said mechanical vibrator for cooperation therewith to cause the changes in the frequency of said mechanical vibrator in response to vibration amplitude changes to follow a nonlinear characteristic.

2. An electric timepiece comprising a time standard oscillator having a relatively high frequency including a quartz crystal vibrator, a tuning fork-type vibrator having a frequency of about 1/ n(n=an integer) of said time standard oscillator; electromagnetic means for sustaining the oscillation of said mechanical tuning-fork-type vibrator; an indexing mechanism; means for transmitting the oscillation of said tuning-fork-type vibrator to said indexing mechanism; means for directly comparing the phase of said time standard oscillator with that of said tuning-fork-type vibrator to produce an output signal proportional to the difference therebetween; and control means for controlling the frequency or the phase of said tuning-fork-type vibrator in response to said output signal of said comparing means for sustaining the frequency of said tuning fork type vibrator at 1/ n of the frequency of said time standard oscillator, said control means being adapted so that the phase or magnitude of the input energy supplied to said tuning-fork-type vibrator is changed in response to said output signal and permanent magnet means positioned adjacent said tuning fork vibrator for cooperation therewith to cause the changes in the frequency of said tuning fork vibrator in response to vibration amplitude changes to follow a nonlinear characteristic.

3. An electric timepiece comprising a time standard oscillator having a relatively high frequency, a mechanical vibrator having a frequency of about 1/ n(n=an integer) of said time standard oscillator, said mechanical vibrator having two balance wheels operatively coupled to each other and mounted for rotation in opposed directions whereby said vibrator is unaffected by external shock; means for sustaining the oscillation of said mechanical vibrator; an indexing mechanism; means for transmitting the oscillation of said mechanical vibrator to said indexing mechanism; means for directly comparing the phase of said time standard oscillator with that of said mechanical vibrator to produce an output signal proportional to the difference therebetween; and control means for controlling the frequency or the phase of said mechanical vibrator in response to said output signal of said comparing means for sustaining the frequency of said mechanical vibrator at 1/ n of the frequency of said time standard oscillator, said control means being adapted so that the phase or magnitude of the input energy supplied to said mechanical vibrator is changed in response to said output signal.