GB2042796A - Piezo-electric vibrator - Google Patents
Piezo-electric vibrator Download PDFInfo
- Publication number
- GB2042796A GB2042796A GB7939802A GB7939802A GB2042796A GB 2042796 A GB2042796 A GB 2042796A GB 7939802 A GB7939802 A GB 7939802A GB 7939802 A GB7939802 A GB 7939802A GB 2042796 A GB2042796 A GB 2042796A
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- Prior art keywords
- vibrator
- frequency
- quartz crystal
- tuning fork
- fork type
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- 239000013078 crystal Substances 0.000 claims description 104
- 239000010453 quartz Substances 0.000 claims description 84
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 84
- 239000000463 material Substances 0.000 claims description 8
- 238000001259 photo etching Methods 0.000 claims description 2
- 238000005520 cutting process Methods 0.000 abstract description 20
- 230000008878 coupling Effects 0.000 abstract description 7
- 238000010168 coupling process Methods 0.000 abstract description 7
- 238000005859 coupling reaction Methods 0.000 abstract description 7
- 238000009826 distribution Methods 0.000 description 10
- 238000006073 displacement reaction Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 5
- 230000032683 aging Effects 0.000 description 5
- 229910052804 chromium Inorganic materials 0.000 description 5
- 239000011651 chromium Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 229910052737 gold Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000005484 gravity Effects 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 210000000707 wrist Anatomy 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/21—Crystal tuning forks
- H03H9/215—Crystal tuning forks consisting of quartz
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
A piezo-electric vibrator of the tuning fork type whose thickness is such that the difference between a fundamental or overtone frequency at which the vibrator vibrates in the flexural mode 25, 26 and a fundamental frequency at which the vibrator vibrates in the torsional mode 27, 28 does not exceed 15% of the first-mentioned frequency. The resulting coupling improves the frequency/temperature characteristic. The cutting angle is also selected with this aim, the vibrator being a Z-cut rotated about the X-axis or Y-axis. <IMAGE>
Description
SPECIFICATION
Piezo-electric vibrator
This invention relates to a quartz crystal or other piezo-electric vibrator of the tuning fork type.
The object of the present invention is to improve the accuracy of such a vibrator.
According to the present invention, there is provided a piezo-electric vibrator of the tuning fork
type whose thickness is such that the difference between a fundamental or overtone frequency at which
the vibrator vibrates in the flexural mode and a fundamental frequency at which the vibrator vibrates in
the torsional mode does not exceed 1 5% of the first-mentioned frequency.
Preferably, there are means for utilising the resonance frequency of the fundamental or overtone flexural vibration as a time reference signal.
The vibrator is preferably formed by photo-etching.
In one embodiment, the vibrator is formed from a sheet of quartz crystal material which has been
rotated through an angle in the range of 0 to --1 70 around an electrical axis thereof.
In another embodiment, the vibrator is formed from a sheet of quartz crystal material which has
been rotated through an angle in the range of +100 to +350 around an electrical axis thereof.
In still another embodiment, the vibrator is formed from a sheet of quartz crystal material which
has been rotated through an angle in the range of 250 to 55 around a mechanical axis thereof.
In yet a further embodiment, the vibrator is formed from a sheet of quartz crystal material which
has been rotated through an angle in the range of +250 to +550 around a mechanical axis thereof.
The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a diagram showing a cutting angle of a quartz crystal plate for making a conventional tuning fork type quartz crystal vibrator,
Figure 2 is a diagram showing a vibration mode of a conventional tuning fork type quartz crystal vibrator,
Figure 3 shows a temperature-frequency characteristic of a conventional tuning fork type quartz -crystal vibrator,
Figure 4 is a diagram illustrating a cutting angle of a quartz crystal plate for making a tuning fork type quartz crystal vibrator according to the present invention,
Figure 5 is a diagram illustrating a vibration mode of a tuning fork type quartz crystal vibrator according to the present invention,
Figure 6 shows a temperature-frequency characteristic of a tuning fork type quartz crystal vibrator according to the present invention,
Figures 7 and 7a are graphs illustrating the distribution of a vibrational displacement (vibration
mode) of a fuming fork type quartz crystal vibrator according to the present invention,
Figure 8 is a graph illustrating a vibrational coupling between two modes found in a tuning fork type quartz crystal vibrator according to the present invention,
Figure 9 is a graph illustrating a frequency characteristic of a tuning fork type quartz crystal vibrator according to the present invention,
Figure 10 is a graph illustrating the temperature-frequency characteristic of a conventional tuning fork type quartz crystal vibrator,
Figure 11 is a graph illustrating the temperature-frequency characteristic of a tuning fork type quartz crystal vibrator according to the present invention,
Figure 1 2 shows an embodiment of an oscillation circuit in which a tuning fork type quartz crystal vibrator according to the present invention may be connected,
Figures 1 3(a) and 13(b) illustrate the frequency deviation due to a difference in the attitude of the vibrator,
Figures 14 and 1 5 are views illustrating an embodiment of a tuning fork type quartz crystal vibrator according to the present invention, Figure 14 being a perspective view indicating the external dimensions of the vibrator, and Figure 1 5 illustrating one step in the process for manufacturing the vibrator,
Figures 1 6 and 1 7 are diagrams showing another cutting angle for a tuning fork type crystal vibrator according to the present invention, and
Figures 18 and 1 9 are graphs illustrating the range of other cutting angles for a tuning fork type crystal vibrator according to the present invention.
In Figure 1 there is shown a tuning fork type quartz crystal vibrator which is to be used as a conventional time reference source for a watch. Figure 1 shows a cutting angle of a quartz crystal plate 11 cut away from a crystal ore in order to make the tuning fork type quartz crystal vibrator. The angle sb is in the range from substantially +20 to substantially +5 . The symbols X, Y and Z as used in the drawing show an electrical axis, a mechanical axis and an optical axis of the quartz crystal, respectively.
In Figure 2 there is shown a tuning fork type quartz crystal vibrator which is made from the quartz plate 11. 12 is the direction of displacement of the vibration and 13 indicates the extent of the displacement due to the vibration taken in the direction of the tuning fork arm. (The extent of the displacement due to the vibration in the direction of the tuning fork arm will hereinafter be referred to as the "vibrator mode").
The temperature characteristic at a resonant frequency of a conventional tuning fork type quartz
crystal vibrator having this vibration mode is shown in Figure 3.
Af f
of the ordinate shown in Figure 3 is defined as follows: Af f(T)f(20) (1)
f f(20)
where f(T) is the resonant frequency at any temperature T( C).
As is apparent from Figure 3, the resonant frequency of the conventional tuning fork type quartz
crystal vibrator varies in accordance with a parabolic curve with respect to temperature and thus is not stable with temperature. Further, since Q of a resonance is as low as 100,000, the secular variation of a
resonant frequency is high and has the disadvantage that the frequency varies in accordance with the
attitude of the vibrator i.e. in accordance with the direction of gravity. (This is referred to hereinafter as a frequency deviation due to the difference of attitude).An AT-cut quartz crystal vibrator which is
conventionally used in communication apparatus shows less frequency variation due to ageing or frequency deviation due to the difference of attitude, but the resonant frequency of such an AT-cut
vibrator is so high that much electric power is consumed when the vibrator is made. The AT-cut
vibrator, moreover, cannot easily be miniaturised or mass produced.
Vibrators made in accordance with the present invention, however, may have some or all of the following characteristics: (1) a resonance frequency which is stable with temperature,
(2) a low power consumption
(3) small size
(4) good mass production characteristics
(5) a high Q and little frequency variation due to ageing,
(6) small frequency variation due to difference of attitude.
A preferred embodiment of the present invention will now be described in detail. In Figure 6 there is shown one particular example of a temperature-frequency characteristic of a tuning fork type crystal vibrator according to the present invention. The ordinate of Figure 6 is as described above. As is apparent at a glance, the characteristic of the vibrator according to the present invention is much superior than that of the conventional type shown in Figure 3. The way in which the characteristic shown in Figure 6 may be achieved will now be described in detail.
In Figure 4 there is shown a quartz crystal plate 21 for use in making a tuning fork type quartz crystal vibrator according to the present invention from a crystal ore. The angle # is in a range of 0 to --150 when a counter-clockwise rotation around an electrical axis results in a positive angle. In Figure 4, reference letters X, Y and Z indicate an electrical axis, a mechanical axis and an optical axis, respectively.
In Figure 5 there is shown a perspective view of a tuning fork type quartz crystal vibrator 22 according to the present invention which is made from the quartz plate 21 of Figure 4. The vibrator 22 has arms or tines 23 and 24.
Reference numerals 25 and 26 indicate the displacement of the vibration qf a fundamental wave or of the first overtone of a flexural vibration in the quartz crystal plate. Reference numerals 27 and 28 indicate the vibration mode of the fundamental wave of a torsional vibration around a central axis of a tuning fork arm.
In Figure 7 there is shown a distribution at Ux along the axis Y' of a displacement of vibration in a direction X of the fundamental wave of the flexural vibration. In Figure 7 there is shown a distribution at t (a distribution of a twisting angle around a central axis) along the axis Y' of the fundamental wave of the torsional vibration. In Figure 7, A indicates a leading end of the vibrator and B indicates the root of a tine of the tuning fork. The fundamental wave mode of the flexural vibration which appears in the tuning fork type quartz crystal vibrator used in the present invention is generally called a distribution Ux.
Similarly, in Figure 7a there is shown a distribution at Ux along the axis Y' of a displacement of vibration in a direction X of the first overtone of the flexural vibration. In Figure 7 there is shown a distribution at T (a distribution of a twisting angle around a central axis) along the axis Y' of the fundamental wave of te torsional vibration. In Figure 7a, A indicates a leading end of the vibrator and B indicates a tine of the tuning fork. The overtone mode of the flexural vibration which appears in the tuning fork type quartz crystal vibrator used in the present invention is generally called a distribution Ux.
However, Ux in the embodiment shown in Figure 7a is an example of the first overtone (the frequency thereof is the lowest but one between A and B), and the first overtone and the overtones of the second and upward are generally called an overtone mode.
The fundamental wave mode of the torsional vibration of a vibrator according to the present invention is generally called a distribution or T. That is, it is a minimum torsional vibration mode found between A and B. The displacement values Ux and T are opposite to each other (the phase is opposite) at the tuning fork arms 23 and 24. The resonance frequency at the vibration mode Ux is made to be fF, and the resonance frequency fT at the vibration mode z is made to be fT. The shape of the tuning fork type quartz crystal vibrator 22 shown in Figure 5 has external dimensions and a thickness t such that the two frequencies fF and fT are closely related to each other.
In Figure 8 there is shown a graph illustrating the variation between the resonance frequencies fF and fT when the thickness t is varied. The ordinate corresponds to the frequency and the abscissa corresponds to the thickness t.
In figure 9 is shown the temperature characteristic of the frequency fF according to the thickness t when the cutting angle is in the range of 0 to --1 70. In Figure 9 reference numeral 91 indicates the temperature characteristic of the frequency fF when t = t, (t, being shown in Figure 8) and reference numeral 92 indicates a typical example of the temperature characteristic when t is also found in the range oft2 to t3 of Figure 8. Reference numeral 94 indicates the temperature characteristic of the frequency fF when t = t4 (t4 being shown in Figure 8).Thus, the cutting angle # is selected at a suitable value in the range of 0 to 170 and the thickness t is selected to show a value between t1 and t2, whereby the vibration of the frequency fF has a desired temperature characteristic.
Each of the frequencies at the fundamental or overtone wave mode of the flexural vibration and the fundamental wave mode of the torsional vibration appearing in the tuning fork type quartz crystal vibration is defined as the above described fF and fT. A difference between each of the fundamental frequencies of the present invention is defined as fF-fT (herein after called Af). When we say herein that the plate has a thickness t such as to produce a difference between the frequencies of the fundamental wave mode of the flexural vibration of less than 1 5% of the frequency of the fundamental or overtone wave mode, what is meant is that
I~ 0.15 (2) fF fF That is, in Figure 8, when fF2-fT2 = = 0.15 (3)
fF2 the thickness t is more than t2 The reason is explained below why the superior frequency shown in figure 9 at 92 may be obtained by properly selecting a value of the thickness t between t2 and t3. The temperature-frequency characteristic shown in Figures 3, 6 and 9 may be defined as follows under a Taylor's expansion at
T = 200C by the use of the above described definition.
Af f(T)-f(20) a(T-20)+(T-20)2+}'(T-20)3 (4) f f(20) Under the third series, the value is an approximate one and the coefficients a,,3 and y are the first, second and third coefficients respectively.
As shown in Figure 8, when the values fF and ff are near to each other, they will interfere with each other. This interference between the frequencies is hereinafter referred to as a coupling. On the contrary, when the values fF and fT are sufficiently different from each other, they are not coupled to each other and thus the values fF and fT have an independent temperature-frequency characteristic.
In Figure 10 there is shown the temperature characteristic with respect to the frequency fF when the cutting angle 9 is varied under an independent action of the frequencies fF and fT by expanding the coefficients of a and p found in the above-mentioned equation (4).As can be understood from Figure 10, the value of a can be made zero by setting the cutting angle 4(1 at substantially +20 to +5 . At this time, since the value of y is low enough to be neglected, the temperature-frequency characteristic depends only on the value of p. That is, this value produces a parabolic curve of the temperature characteristic, and this one is a conventional tuning fork type quartz crystal vibrator, this conventional type of quartz crystal vibrator being shown in Figure 3.In turn, in the present invention, it is intended to provide a mutual interference (coupling) between the values fF and ff, and to improve the temperaturefrequency characteristic by closely correlating the resonant frequency fF of the fundamental wave or of the overtone of the flexural vibration and the resonant frequency fT of the fundamental wave of the torsional vibration (Figure 8). At first, it is arranged that the values fF and fT are closely related to each other, that is, the thickness is neariy the same value at that oft1, t2, t3 and t4 etc. Since the values fF and ff are closely related to each other as shown in Figure 8, the frequency fF is affected by the frequency fT. A greater effect may be achieved when t is equal to t2 than when t is equal to t,.Similarly, the effect may be increased in sequence from t2, t3 and t4 (hereinafter referred to as achieving a greater coupling).
Thus, it is apparent that the temperature characteristic at the value fF will be affected by the frequency ff and will further depend upon the thickness t.
Figure 18 shows graphs relating to vibrators in which the thickness t is adjusted so that the value of a always equals zero at various values of the cutting angle #, and the values oft and P are shown at these various thicknesses. When # = A and t = tA or + = {,bB and t = tB, p will be equal to zero.Figure 11 shows how, in relation to the values of a, p, y of equation (4), the temperature characteristic of the value fF of the vibrator (a resonant frequency of a fundamental wave or overtone of the flexural vibration) varies with reference to a variation of the thickness t when + equals NbA. In Figure 1 when t = tA, it is apparent that a equals zero and P equals zero, provided that the value tA is the same as that of tA in Figure 1 8. Thus, it is apparent that the temperature-frequency characteristic will depend only upon the third coefficient y and thus will thus be constituted by a cubic curve.This is the temperaturefrequency characteristic of the tuning fork type quartz crystal vibrator according to the present invention which is shown at 92 in Figure 9 and at 61 in Figure 6. The correct values of the cutting angle 0 and the thickness tA depend upon the shape of the tuning fork type quartz crystal vibrator and the frequencies of fF and fT. Thus, the quartz crystal plate is formed of a crystal ore by rotating it around an electrical axis in the range of 0 to 150, and by giving it a suitable cutting angle # in said range of about A with reference to the shape of the tuning fork type quartz crystal vibrator and to the frequencies fF or fT to be applied.
For example, the frequency of the fundamental wave of the flexural vibration may be substantially 100 KHz and one embodiment of the tuning fork type quartz crystal vibrator having the temperaturefrequency characteristic shown in Figure 6 may be provided when AF = fF - fT 1 to 10 KHz in the case that fF -- 100 KHz or so, the thickness t being t = 80 to 1 OOjum, and Si = 1 O or so.
In another example, the frequency of the fundamental wavepf the flexural vibration may be substantially 32 KHz and one embodiment of the tuning fork type quartz crystal vibrator having the temperature-frequency characteristic shown in Figure 6 may be provided AF = fF - fT ~ 5 to 1 5 KHz in the case that the frequency fF of the first overtone of the flexural vibration is fF -- 200 KKz or so, the thickness t being t = 130 to 180 ,um, and 0 = - 100 or so.
Other values of fF, fT, t, + may also be obtained by a theoretical analysis in reference to a coupling of two frequencies. And by experiment, a tuning fork type quartz crystal vibrator according to the present invention may be obtained having a temperature-frequency characteristic as shown in Figure 6 of less than 1.6 PPM in the range of OOC to 400C.
The vibrator of the present invention, may have been made by rotating it in the range of + t00 to 350 around an electrical axis. In this case, the cutting angle # = B or so in Figure 18. Even at this cutting angle, the value of a =0 may be changed to p = O by making t = tB and the temperaturefrequency characteristic will also depend only upon the value of y as indicated in Figure 6, Figure 16 shows this cutting angle.
Figure 19 shows graphs relating to the arrangement shown in Figure 17 when rotated around the axis Y by 0 (counter-clockwise rotation viewed from a positive side of the axis Y is a positive rotation).
The thickness t is adjusted so that the value of a is equal to zero and the value of P is equal to zero. The values of a and p are equal to zero when the value oft equals the value tA and when the value of 0 equals the value of BA, and thereby the result shown in Figure 6 may be obtained. Then the result shown in Figure 6 may be provided when the value oft equals the value of tB when 0= OB.
The vibrator may be made of a crystal ore by rotating it around a mechanical axis in the range of - 250 to - 350 and in this case a cutting angle of about 0= 0A as shown in Figure 19 is used.
The vibrator may be made of a crystal ore by rotating it around a mechanical axis in the range of +250 to +550, and in this case the cutting angle of about 0 = OB shown in Figure 19 is used.
The thickness of the vibrator is such that the difference between a fundamental or overtone frequency at which the vibrator vibrates in the flexural mode and a fundamental frequency at which the vibrator vibrates in the torsional mode does not exceed 1 5% of the first-mentioned frequency. Thus this
occurs at a thickness of about t = tA and t = tB in Figures 18 and 19. When the difference is less than 15%, the present effect may be achieved by reference to the influence caused by the coupling. The above described cutting angles SA sbA. ,bB 0A and OB are some practical examples. Even if the plate is rotated a little in any direction at about these cutting angles, the above described effect may be obtained on the same principle as above and thus it is not necessary to provide further description thereof.
Although a conventional tuning fork type quartz crystal vibrator has a temperature-frequency characteristic of 14 PPM (Figure 3) as will be appreciated from the above, it is possible in the case of the present invention to have the value of the characteristic to be improved to less than 1.6 PPM. This makes it possible to provide a tuning fork type quartz crystal vibrator having the very valuable feature of providing a resonance frequency which is stable to the temperature.
Compared with the conventional tuning fork type crystal vibrator wherein the fundamental vibration (13 in Figure 2) is used, Q of the resonance can be extremely high when the resonance frequency fH of the tuning fork type crystal vibrator is an overtone vibration (Ux in Figure 7).
In comparison to a value of Q of a conventional tuning fork type crystal vibrator which is in the range of 70,000 to 100,000, a vibrator according to the present invention may have a value of Q of the frequency fF of the tuning fork type crystal vibrator from about 100,000 to about 300,000. This value of
Q is used to evaluate the stability of the value of the frequency. Thus when a tuning fork type quartz crystal vibrator according to the present invention is oscillated, the stability of the oscillating frequency if further improved and a frequency variation due to the ageing is decreased.
Compared with the conventional fork type quartz crystal vibrator wherein the frequency deviation due to the ageing is 10-5 to 10-8 per year, the frequency deviation due to the ageing in the case of a vibrator according to the present invention can in some cases be 1 of6 to 10-7 per year and superior.
In a conventional tuning fork type quartz crystal vibrator, a difference of attitude causes the resonant frequency to vary in relation to the direction of gravity. As shown in Figure 13, it has been found that the resonant frequency was changed according to whether either one of the plate surfaces A or B of the tuning fork type quartz crystal vibrator was facing downwards. The arrow g shown in Figure 13 indicates the direction of the acceleration due to gravity and the direction g will be called the "lower" direction.Due to the fact that an elastic constant of a quartz crystal vibrator has anisotropy and due also to the fact that a quartz plate cut away from a quartz crystal ore is displaced from the X-Y plane (see
Figure 1), the effect of gravity depends upon which of the surfaces A, B or the quartz crystal vibrator shown in Figure 13(a) is facing downwards. Thus, it may also be said that the resonant frequency may be varied in dependence upon whether either one of the surfaces A or B faces downwards. It may also be said that when the vibrator is stood up as shown in Figure 13(b), the resonant frequency will be different from that obtained when it is dispersed as shown in Figure 1 3(a). In order to decrease such resonant frequency deviation due to a difference of attitude, the resonant frequency may be increased or an overtone may be used.In the latter case, the said deviation can be extremely small.
As already described, a tuning fork type quartz crystal vibrator according to the present invention may have such a relatively low deviation due to the difference of attitude by reason of having a high frequency of fF of about 100 KHz. In case of a conventional tuning fork type quartz crystal vibrator, the deviation due to the difference of attitude was about 0.2 PPM and by comparison the vibrator of the present invention has a lower value than this.
In Figure 12 there is shown a practical electrical block diagram indicating an arrangement of a quartz crystal oscillator provided with a tuning fork type quartz crystal vibrator according to the present invention. In this Figure, 121 is an inverter having a complementary MOS, 122 is a tuning fork type quartz crystal vibrator according to the present invention, both 123 and 124 are capacitors, and 125 is a frequency divider (for example, a flip-flop circuit) for dividing the output of the oscillator. 126 is a device for displaying time (for example, a time display device of a watch). It is not required to have a specific arrangement in the oscillator in order to cause a tuning fork type quartz crystal vibrator according to the present invention to be oscillated at about the fundamental wave mode or the overtone mode of the flexural vibration.Since the resonance resistance of the resonance mode of ff is usually higher than that of fF in the two resonance modes fF and fT which appear in a tuning fork type quartz crystal vibrator according to the present invention, this vibrator will oscillate only at about fF even if the oscillator is a normal one having no particular arrangement. Thus, in the various kinds of characteristics of the frequency of the oscillator (for example, the temperature characteristic with respect to the frequency) are the characteristic fF which has already been described. As will be appreciated in order to make the oscillation at fF easily achievable, particular arrangements may be provided for a pattern of electrodes to be affixed to the surface of the tuning fork type crystal vibrator and for increasing the resonance resistance.Further the oscillator 121 need not be an oscillator having a complementary MOS but may be a normal transistor type oscillator or a bulb type oscillator.
Due to the fact that a normal oscillator may be formed with the vibrator of the present invention, a known crystal oscillator circuit may be used without any modification in an electronic wrist watch in which a low consumptive power has already been realized. Further, whilst a conventional AT-cut crystal vibrator having a good temperature-frequency characteristic oscillating frequency of some MHz, a vibrator according to the present invention may have a frequency of about 100 KHz or about 200 KHz and thus some tenth of the conventional value. Since the consumptive power of the oscillator is approximately proportional to the oscillation frequency when the crystal vibrator of the present invention is oscillated at about the value of fF as in the preferred embodiment shown in Figure 12, the consumption power is some tenth of that of a conventional AT-cut crystal vibrator.
In recent years, it has been proposed to obtain a time signal having a superior temperaturefrequency characteristic by using two conventional tuning fork type quartz crystal vibrators, though it has been found that this proposal would require some complicated electrical circuitry. In comparison to the prior art, the vibrator of the present invention may have a superior temperature characteristic while using only a single crystal vibrator, and also the oscillator circuit may be formed by a conventional simple circuit.
The resonance frequency of the fundamental wave mode or the overtome mode of the flexural vibration of the vibrator may be used as a time reference signal. In this case, a value of fF having a superior stability of frequency as described above is to be used in an oscillator etc., as a more stable time signal source. When a tuning fork type quartz crystal vibrator according to the present invention is used as described above, it is possible to achieve a low power consumption.
In Figure 14 there is shown a perspective view of a preferred embodiment of a tuning fork type quartz crystal vibrator according to the present invention. This vibrator may be so formed that the value of fF is substantially 100 KHz and the external dimensions of it, as shown in Figure 14 may, for example be 1 = 3 mm to 4 mm, w = 1.0 mm to 1.5 mm, and t = 50 um to 1 50 Mm. This crystal vibrator will be described hereinafter.Alternatively, fF may be substantially 1 50 to 200 KHz, and the external dimensions may be I = 4 mm to 5 mm, w = 0.8 mm to 1.0 mm, and t = 140 jum to 180 jum. In comparison to a conventional tuning fork type quartz crystal vibrator having I = 6 mm, w = 1.5 mm, and t = 500,um, the vibrations of the present invention may be small in size.
An AT-cut crystal vibrator which is conventionally known as a highly accurate crystal vibrator is formed of a circular flat plate or a rectangular flat plate, and its shape, viewed in top plan, has a diameter of 10 mm, a width of 3 mm and a length of 10 mm. Further, its thickness is extremely high, being 800,um when the frequency is 2 MHz. In comparison to this conventional type of vibrator, a tuning fork type quartz crystal vibrator according to the present invention is extremely small as described above. Thus, the vibrator of the present invention is suitable for use in an electronic wrist watch or in a small apparatus in which it is used as a time reference source.
In Figure 1 5 there is shown a stage in the manufacture of a tuning fork type quartz crystal vibrator according to the present invention. At first, films of chromium and gold are adhered to both the major surfaces of a thin quartz crystal plate by a vacuum depositing or spattering process which is ground to a thickness of 50 cm to 200,us. The films are exposed through a glass mask on which a number of cute shapes of the tuning fork type quartz crystal vibrator are printed for use in affixing a photo-resist. The resist which is not exposed is stripped off by using a solvent, and the remaining resist is used as a mask and then the above described films of chromium and gold are dissolved away where not required.Then the films of chromium and gold are used as a mask, and a plate or wafer of the crystal is dipped in an etching liquid of hydrofluoric acid. Thereby the non-required portions of the plate or wafer of the crystal are etched away, and a tuning fork type quartz crystal vibrator strictly corresponding to the shape of the mask may be provided. In Figure 1 5 151 indicates a frame, 1 52 shows a tuning fork type quartz crystal vibrator, 153 indicates a portion connecting the frame 1 51 with the quartz crystal vibrator 1 52, 1 54 indicates dual films of chromium and gold affixed to the front and back surfaces of the quartz crystal vibrator. The dual films of chromium and gold are used as an energizing electrode of the tuning fork type quartz crystal vibrator. As will be appreciated, the electrode films may be shaped to any pattern if a suitable glass mask for making the electrode film pattern is utilized. In the arrangement shown in Figure 1 5, a great number of tuning fork type quartz crystal vibrators may be. made by breaking the connections 1 53. Thus, since the tuning fork type quartz crystal vibrator may have a thickness and external dimensions as shown in Figure 14, it is possible to use a photo-lithographic manufacturing process, thus enabling mass-production to be effected. The reason why such photo-lithography may be used in making a tuning fork type quartz crystal vibrator according to the present invention is that the thickness of the vibrator may be in the range of 50 Mm to 200 Mm.
Claims (8)
1. A piezo-electric vibrator of the tuning fork type whose thickness is such that the difference between a fundamental or overtone frequency at which the vibrator vibrates in the flexural mode and a fundamental frequency at which the vibrator vibrates in the torsional mode does not exceed 1 5% of the first-mentioned frequency.
2. A vibrator as claimed in claim 1 in which there are means for utilising the resonance frequency of the fundamental or overtone flexural vibration as a time reference signal.
3. A vibrator as claimed in claim 1 or 2 in which the vibrator is formed by photo-etching.
4. A vibrator as claimed in any preceding claim in which the vibrator is formed from a sheet of quartz crystal material which has been rotated through an angle in the range of O to 170 around an electrical axis thereof.
5. A vibrator as claimed in any one of claims 1 to 3 in which the vibrator is formed from a sheet of quartz crystal material which has been rotated through an angle in the range of +100 to +350 around an electrical axis thereof.
6. A vibrator as claimed in any of claims 1 to 3 in which the vibrator is formed from a sheet of quartz crystal material which has been rotated through an angle in the range of -250 to --550 around a mechanical axis thereof.
7. A vibrator as claimed in any one of claims 1 to 3 in which the vibrator is formed from a sheet of quartz crystal material which has been rotated through an angle in the range of +25 to +55 around a mechanical axis thereof.
8. A piezo-electric vibrator of the tuning fork type substantially as hereinbefore described with reference to and as shown in Figures 4-9, 11-12 and 14-1 9 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14949978A JPS5575325A (en) | 1978-12-01 | 1978-12-01 | Tuning fork type crystal oscillator |
| JP14950078A JPS5575326A (en) | 1978-12-01 | 1978-12-01 | Tuning fork type crystal oscillator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2042796A true GB2042796A (en) | 1980-09-24 |
| GB2042796B GB2042796B (en) | 1983-01-19 |
Family
ID=26479373
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7939802A Expired GB2042796B (en) | 1978-12-01 | 1979-11-16 | Piezoelectric vibrator |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2042796B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2176892A (en) * | 1985-06-17 | 1987-01-07 | Yokogawa Hokushin Electric | Quartz resonator thermometer |
| EP1111770A1 (en) * | 1999-12-21 | 2001-06-27 | Eta SA Fabriques d'Ebauches | Oscillator arrangement for low-frequency quartz and having an improved temperature dependency |
| US6509804B2 (en) | 1999-12-21 | 2003-01-21 | Eta Sa Fabriques D'ebauches | Low frequency quartz oscillator device with improved thermal characteristics |
-
1979
- 1979-11-16 GB GB7939802A patent/GB2042796B/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2176892A (en) * | 1985-06-17 | 1987-01-07 | Yokogawa Hokushin Electric | Quartz resonator thermometer |
| GB2176892B (en) * | 1985-06-17 | 1989-05-10 | Yokogawa Hokushin Electric | Quartz thermometer |
| EP1111770A1 (en) * | 1999-12-21 | 2001-06-27 | Eta SA Fabriques d'Ebauches | Oscillator arrangement for low-frequency quartz and having an improved temperature dependency |
| US6509804B2 (en) | 1999-12-21 | 2003-01-21 | Eta Sa Fabriques D'ebauches | Low frequency quartz oscillator device with improved thermal characteristics |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2042796B (en) | 1983-01-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PE20 | Patent expired after termination of 20 years |
Effective date: 19991115 |