US3441753A

US3441753A - Electric timepiece regulator

Info

Publication number: US3441753A
Application number: US654570A
Authority: US
Inventors: Toshio Terayama
Original assignee: Seiko Instruments Inc
Current assignee: Seiko Instruments Inc
Priority date: 1966-07-26
Filing date: 1967-07-19
Publication date: 1969-04-29
Anticipated expiration: 1986-04-29

Description

April 1969 TOSHI TERAYAMA 3,441,753

ELECTRIC TIMEPIECE REGULATOR Filed July 19, 1967 Sheet of 2 TUNING FORK f 3 i l I f5 /6 r TRANSISTOR FREQUENCY ELECTRO- TIME AMPLIFIER DIVIDER MECHANICAL INDCATOR FLlP-FLOPS CONVERTER 4 SELF OSCILLATOR m II II I, p I 0 II 2 P 1 1 F D 0 Am I F R RI wwmwww A TTORNEY- April 1969 TOSHI TERAYAMA 3,441,753

ELECTRIC TIMEPIECE REGULATOR Sheet 3 of 2 Filed July 19, 1967 5 ilmg/w Aazaw ATTORNEY United States Patent US. Cl. BIO-8.2 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a regulator for an electric timepiece whereby the oscillation frequency of the frequency standard is selectively varied from the outside of the timepiece case by a variable resistor. Three piezoelectric electrode elements are secured to a tuning fork frequency standard. A transistor amplifier has its input connected to one of the electrodes and with its output fed back to a second of the electrodes. The variable resistor is connected between ground and the third electrode, whereby the oscillation frequency of the tuning fork is selectively varied in accordance with the resistance of the variable resistor.

Background of the invention The present invention generally relates to an electric timepiece regulator and more particularly to an electromechanical frequency standard regulator.

Presently, in order to adjust a mechanical timepiece oscillator such as a tuning fork or tuning bar, it was necessary to mechanically adjust the oscillator, such as by grinding away a portion of the oscillators top or base portion. Such methods of mechanical adjustment is unsatisfactory because of the change in the oscillator resonant frequency caused by aging.

Another presently used method for oscillator frequency adjustment required the adjustment of the center of gravity of the mechanical oscillator by shifting of oscillator mass distribution. Such an adjustment method was found to be undesirable since it required rendering the mechanical oscillator stationary in order to carry out the frequency adjustment process. This was found to be a serious drawback particularly in the case of highly accurate timepieces, since it precluded continuous frequency adjustment as well as frequency adjustment from the case interior.

Furthermore, the method of frequency adjustment by adjusting the negative electromagnetic stiffness of the oscillator by means of a magnet is disadvantageous since this adjustment has been found to atfect much the resonant frequency temperature coefiicient of the oscillator.

It is therefore an object of the present invention to provide an electric timepiece regulator which is relatively uncomplicated in construction whereby frequency adjustment may be accomplished from outside the timepiece case.

It is a further object of the present invention to provide an electric timepiece regulator which is operative to provide continuous frequency adjustment while the mechanical oscillator is in motion.

Another object of the present invention is to provide an electric timepiece regulator which is operative to provide continuous frequency adjustment without affecting the other timepiece parameters, such as, frequency-temperature coefficient, frequency-battery voltage, and power consumption characteristics.

Brief description of the invention In accordance with the principles of the present invention there is provided a timepiece regulator comprising mechanical oscillator means and a plurality of piezoelectric elements secured to the mechanical oscillator means. Electrical amplifier means has its input connected to one of the piezoelectric elements and its output connected to a second of the piezoelectric elements. There is further provided a varita'ble resistor which is connected to a third of the piezoelectric elements which is operative to selectively vary the oscillation frequency of the mechanical oscillator means in accordance with the resistance value of the variable resistor.

Brief description of the drawings For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a partial schematic diagram and partial functional block diagram depicting a preferred embodiment of the present invention.

FIG. 2 is a perspective view of a mechanical oscillator and regulator constructed in accordance with the principles of the present invention.

FIG. 3 is a perspective view of another mechanical oscillator and regulator constructed in accordance with the principles of the present invention.

FIG. 4 is a perspective view of yet another mechanical oscillator and regulator constructed in accordance with the principles of the present invention.

FIG. 5 is a schematic diagram depicting the electroacoustical equivalent circuit of preferred embodiments of FIGS. 24.

FIG. 6 is a schematic diagram of a simplified version of the equivalent circuit of FIG. 5.

FIG. 7 is a graphical representation depicting the variation of equivalent capacitance C and equivalent resistance R as a function of the variation of resistance R.

FIG. 8 is a graphical depiction of the variation in resonant frequency AW W0 Description of embodiments Referring to FIG. 1 there is shown partial schematic and partial functional block diagram of a self-excited oscillator 1 constructed in accordance with the principles of the present invention. Oscillator 1 comprises a tuning fork oscillator 2 whose output at piezoelectric element P is fed to transistor amplifier 3 whose output is fed back to tuning fork 2 via piezoelectric element D to provide an amount of electrical energy sufiicient to keep tuning fork 2 oscillating. A selectively variable resistor R is connnected between piezoelectric element F secured to the other leg of tuning fork 2 and ground, and is operative to selectively vary the frequency of the tuning fork output. The output of amplifier 3, which is an amplified electrical signal same as applied on piezoelectric element D is applied to frequency divider 5, which may suitably comprise a chain of flip-flop circuits.

The output of frequency divider 5 is applied to electromechanical converter 6, which may suitably comprise a pulsed motor, whose output is applied to time indicator 7 which may suitably comprise a gear train system in conjunction with suitable display means.

Referring to FIG. 2, there is shown a tuning fork 2 of a material having a substantially constant coeflicient or elasticity, such as Elinvar or Ni-Span C which is secured to its base plate by means of set screws through its support (not shown). Adhesively secured to the tuning fork bottom portion 2a are piezoelectric electrode elements P, D and F which are connected to their output terminals p, d and 1 respectively by lead wires as shown. Electrode elements P, D and F are made of piezoelectric material such as barium titanate or lead zirconatetitanate. Electrode P is operative to detect the mechanical motion of tuning fork 2 and to produce an electrical signal proportional thereto, while electrode D is operative to convert the electrical feedback signal from transistor amplifier 3 to mechanical driving motion which is applied to tuning fork 2.

Resistor R, which is connected between electrode F and ground terminal g, is selectively variable to thereby vary the equivalent capacity in the series resonant circuit representing the motional impedance, i.e., acoustical impedance of the mechanical oscillator to thereby selectively vary the resonant frequency of the mechanical oscillator of the present invention.

Referring to FIG. 3, there is depicted another embodiment of a mechanical oscillator constructed in accordance with the present invention whereby the piezoelectric electrode elements P and F are adhesively secured to one prong 2c of tuning fork 2, while the remaining piezoelectric electrode element D is secured to the opposite tuning fork leg 2b.

Referring to FIG. 4, there is shown yet another embodiment of a mechanical oscillator constructed in accordance with the principles of the present invention, whereby a tuning bar 2A is supported by wires W and W at its theoretical node points while having its ends free. Piezoelectric electrode elements P, D and F are adhesively secured to tuning bar 2A at its upper surface, and as in the embodiments of FIGS. 2 and 3 have leads extending therefrom to their respective terminals p, d and 1.

Referring to FIG. 5, there is shown an acoustic schematic diagram of the equivalent circuit of the mechanical oscillator of the present invention. It is noted that when terminals X-X are short-circuited, the circuit of FIG. 5 represents the equivalent circuit of a mechanical oscillator having no F electrode. A A and A are force factors representing the electro-mechanical conversion efficiency of the piezoelectric elements while C 1, C and C represent the electrostatic capacities thereof. The coefficient m, s, and r corresponding to the equivalent mass, stiffness (reciprocal of compliance or equivalent capacity) and the equivalent mechanical resistance of the oscillator respectively while terminal pairs p-p", d-d' and f-f' represent the piezoelectric element terminals respectively.

It is understood that the force factors A A and A and C01, C02: C03, are not necessarily equal to each other. However, to facilitate analysis of the circuit of FIG. 5 let A1=Az A3 A, and let C =C =C =C Then the equivalent circuit of FIG. 5 reduces to the circuit of FIG. 6. In FIG. 6, X-X' corresponds to terminals fand L=m/A C=A /s and R=r /A From the above it follows that where W is the angular frequency of the input signals.

When the oscillator is in self-oscillation in conjunction with amplifier 3, the oscillation frequency will be very close to the mechanical resonant frequency W i.e., W W

Referring to FIG. 6, when terminals p-p are short circuited, with terminals d-d being driven by a constant voltage source, the resonant frequency W may be expressed as and 1 oo V35 Referring to

Equations

1, 2 and 3 above, it is seen that the resonant frequency W will have a maximum value of when C =C with R'=oo, and W will have a minimum value W when Cx: 00 with R: O.

In order for the mechanical oscillator to have a high Q factor, since c/c is generally quite small, i.e., 0/0 is in the range of 10- to 1O the maximum regulation range may be expressed as AW Wo tinuously varied from W... to (1+ while the resistance of resistor R which is connected across terminals fis varied from 0 to 00 with the maximum slope of the change in frequency occurring when 1 I R W 0 with no variations in the other timepiece parameters being experienced.

In one experiment, utilizing a tuning fork arrangement as shown in FIG. 2 the following results were achieved:

with the maximum regulation range being while the resistance of resistor R was varied from 0 to 2 megohms.

In another experiment using a similar sized tuning fork 2 but utilizing a larger F electrode, a maximum regulation range of was achieved.

It is understood that the tuning fork of FIG. 3 may be utilized 'where it is desired to obtain a larger regulation range. In such a case, since the force factor will be larger, c/c will be greater by providing a larger piezoelectric element at the point where the higher stress occurs, e.g., on the tuning fork leg near the yoke portion. These principles may also be applied to the tuning bar 2A shown in FIG. 4, where maximum regulation may be obtained by having piezoelectric electrode F secured to bar 2A at the center portion thereof, where the highest stress will occur during oscillation.

Referring to FIG. 1, it is understood that frequency divider 5 may be eliminated if electromechanical converter 6 is frequency matched with oscillator 1, and if necessary, a power amplifier may be provided between the output of oscillator '1 and the input to converter 6, if the power output of oscillator 1 is insufiicient.

It is further understood that the mechanical oscillator of the present invention is not necessarily limited to a piezoelectric driven system but may suitably incorporate an electromagnetic driven system.

In view of the above it is seen that the following advantages over conventional timepiece regulators are obtained with the timepiece regulator of the present invention, as follows. An electric timepiece may be easily and continuously regulated from outside the case over a range of :5 seconds or more a day merely by selectively varying regulating resistor R from outside of the timepiece case. There is completely avoided the heretofore common problems caused by regulation such as frequency shift due to aging, loss of balance of the tuning fork prongs, stopping of tuning fork oscillation, variation of the frequency-temperature characteristics as well as the frequency-battery terminal voltage characteristics. Furthermore, the maximum regulation range may be chosen by selecting the size of the piezoelectric element and by selectively locating the element on the mechanical oscillator.

While there have been shown particular embodiments of the present invention, it is understood that it is not wished to be limited therto, since modifications can be made thereto without departing from the spirit and scope of the present invention, and it is intended to cover such modifications in the claims appended hereto.

What is claimed is:

1. A timepiece regulator comprising, mechanical oscillator means, a plurality of piezoelectric electrode elements secured to said mechanical oscillator means, electrical amplifier means having its input connected to one of said piezoelectric electrode elements and its output connected to a second of said piezoelectric electrode elements, and a variable resistor connected to a third of said piezoelectric electrode elements, and the base of said mechanical oscillator means, said resistor being operative to selectively vary the oscillation frequency of said mechanical oscillator means at said one piezoelectric electrode element in accordance with the resistance value of said resistor.

2. A timepiece regulator as defined in claim 1 wherein said mechanical oscillator means is a tuning fork.

3. A timepiece regulator as defined in claim 1 wherein said mechanical oscillator means is a tuning bar.

4. A timepiece regulator as defined in claim 2 wherein said piezoelectric electrode elements are secured to the yoke of said tuning fork.

5. A timepiece regulator as defined in claim 2 wherein said piezoelectric electrode elements are secured to the prongs of said tuning fork.

6. A timepiece regulator as defined in claim 3 wherein said piezoelectric electrode elements are secured to one surface of said tuning bar.

7. A timepiece regulator as defined in claim 1 wherein said piezoelectric elements are three in number.

8. A timepiece regulator as defined in claim 7 wherein the output of said electrical amplifier means is connected to an electromechanical converter for driving time indicator means connected thereto.

9. A timepiece regulator as defined in claim 8 including frequency dividing means having its input connected to the output of said electrical ampli-fier means and its output connected to the input of said electromechanical converter. f

10. A timepiece regulator as defined in claim -8 including a power amplifier having its input connected between said electrical amplifier means and said electromechanical converter for driving said electromechanical converter.

References Cited UNITED STATES PATENTS 1,781,513 11/1930 Holweck 84-409 1,849,271 3/ 1932 Bower 58-23 2,747,090 5/1956 Cavalieki 331-156 3,024,429 3/1962 Cavalieki 331-156 3,243,951 4/ 1966 Kawakami 331-116 3,325,743 6/1967 Blum 310-83 3,336,529 8/1967 Tygart 310-82 3,343,365 9/1967 Vosseler 310-81 J. D. MILLER, Primary Examiner.

US. Cl. X.R.