Mode coupled tuning fork type quartz crystal vibrator and method of tuning
First Claim
1. A mode coupled quartz crystal vibrator coupling two different modes of vibration, comprising:
- a quartz crystal plate cut in the shape of a tuning fork having a base region, two coplanar tuning fork arms extending from the base for vibrating in a main vibrational mode and a different second vibrational mode and having excitation electrodes on the principal surfaces of said plate;
first adjust electrode means for adjusting the resonant frequency of the main vibration; and
second adjust electrode means for adjusting the difference (Δ
f) between the resonant frequency of the main vibration and the resonant frequency of the sub-vibration for adjusting the frequency-temperature characteristics of the vibrator,said first adjust and second adjust electrode means formed on the surface of the arms in the region near the top of the arms.
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Abstract
A mode coupled tuning fork type quartz crystal vibrator utilizing two different vibrational modes is provided. The vibrator includes at least one electrode on each tuning fork arm for adjusting the resonant frequency of the main vibration and an electrode for adjusting the frequency-temperature characteristic of the vibrator. The main vibration is in the flexural mode (F1) and the sub-vibration is in the torsional mode (T0). The resonant frequency of the first overtone in the flextural mode is designated by fF and the resonant frequency of the fundamental vibration in the torsional mode is denoted by fT. The difference between fF and fT defined as Δf=fF -fT determines the frequency-temperature characteristics of the mode coupled vibrator.
The electrodes for adjusting fF are substantially triangular in shape and the electrodes for adjusting fT are substantially rectangular in shape. These electrodes are disposed at positions near the top of each tuning fork arm and on both principal surfaces of the vibrators. The resonant frequencies are adjusted by removing a portion of electrode material or adding a strip of metal to the electrode. Preselected oscillation frequency and frequency-temperature characteristics in the form of a cubic curve at ambient temperatures are obtained by first adjusting Δf to a preselected value ΔfO and then adjusting fF to a preselected value fF0 at the same time maintaining Δf at the value Δf0.
49 Citations
33 Claims
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1. A mode coupled quartz crystal vibrator coupling two different modes of vibration, comprising:
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a quartz crystal plate cut in the shape of a tuning fork having a base region, two coplanar tuning fork arms extending from the base for vibrating in a main vibrational mode and a different second vibrational mode and having excitation electrodes on the principal surfaces of said plate; first adjust electrode means for adjusting the resonant frequency of the main vibration; and second adjust electrode means for adjusting the difference (Δ
f) between the resonant frequency of the main vibration and the resonant frequency of the sub-vibration for adjusting the frequency-temperature characteristics of the vibrator,said first adjust and second adjust electrode means formed on the surface of the arms in the region near the top of the arms. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A mode coupled quartz crystal vibrator coupling two different modes of vibration, comprising:
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a quartz crystal plate cut in the shape of a tuning fork having a base region and two coplanar tuning fork arms extending from the base for vibrating in a first flexural mode of vibration (F1) and a secondary torsional mode of vibration (T0), said vibrator utilizing the first overtone of the flexural mode and the fundamental vibration of the torsional mode and having excitation electrodes on both principal surfaces of said plate; first adjust electrode means for adjusting fF, the resonant frequency of the main vibration; and one of second adjust electrode means for adjuting Δ
f, the difference between the resonant frequency of the main vibration fF and the resonant frequency of the secondary vibration fT designated Δ
f=fF -fT and third adjust electrode means for adjusting R=fT /fF, wherein fF and fT are the resonant frequencies at 20°
C., for adjusting the frequency-temperature characteristics of the vibrator,said first electrode means and one of said second and third adjust electrode means are formed in the region near the top of the tuning fork arms. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method for forming a mode coupled tuning fork type quartz crystal vibration having two opposed principal planar surfaces, said vibrator coupling two different modes of vibration, the main vibration mode being the flexural mode (f1) with the resonant frequency of the first overtone of the flexural mode being designated fF, and the sub-vibrational mode being the torsional mode (T0), the resonant frequency of the fundamental vibration of the torsional mode being designated fT, comprising:
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forming first adjust electrode means for adjusting fF, by disposing first adjust electrodes at the region at the top of the tuning form arms and on both principal surfaces of the vibrator, said electrodes formed so as not to extend across the full width of the arms along the length of the electrode; and forming second adjust electrode means for adjusting Δ
f=fF -fT for adjusting the frequency-temperature characteristics of the vibrator, by disposing second adjust electrodes at the region of the top of the tuning fork arms, and electrodes formed on both principal surfaces of the vibrator. - View Dependent Claims (31, 32)
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33. A method for forming a mode coupled tuning fork type quartz crystal vibrator having two opposed principal planar surfaces, said vibrator coupling two different modes of vibration, the main vibration being the flexural mode (F1) with the resonant frequency of the first overtone of the flexural mode being designated fF, and the sub-vibrational mode being the torsional mode (T0), the resonant frequency of the fundamental vibration of the torsional mode being designated fT, comprising:
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forming first adjust electrode means for adjusting fF by disposing electrodes having a substantially triangular shape for finely adjusting fF and substantially rectangular electrodes roughly adjusting fF at the region of the top of the tuning fork arms on both principal surfaces of each arm; forming second adjust electrode means for adjusting one of Δ
f=fF -fT and R=fF /fT, (fF and fT being the resonant frequencies at 20°
C.), by disposing substantially rectangular electrodes at the region of the top of the tuning fork arms on both principal surfaces of each arm,roughly adjusting fF by one of the steps of removing a strip of electrode material from and adding a strip of metal to each rectangular electrode for roughly adjusting fF to a value of about 100 ppm lower than a preselected frequency fF0 ; adjusting one of Δ
f and R by one of the steps of removing a strip of electrode material from and adding a strip of metal to each rectangular electrode for adjusting Δ
f so that Δ
f is adjusted to a preselected value Δ
f0 ; andfinely adjusting fF to the preselected value fF0 and at the same time maintaining Δ
f at the preselected value Δ
f0 by one of the steps of removing a strip of electrode material from and adding a strip of electrode material to each triangular electrode for finely adjusting fF.
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Specification