GB1593774A - Tuning fork-type quartz crystal vibrator - Google Patents
Tuning fork-type quartz crystal vibrator Download PDFInfo
- Publication number
- GB1593774A GB1593774A GB4701477A GB4701477A GB1593774A GB 1593774 A GB1593774 A GB 1593774A GB 4701477 A GB4701477 A GB 4701477A GB 4701477 A GB4701477 A GB 4701477A GB 1593774 A GB1593774 A GB 1593774A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lead terminals
- quartz crystal
- vibrator
- tuning fork
- terminal plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000013078 crystal Substances 0.000 title claims description 66
- 239000010453 quartz Substances 0.000 title claims description 54
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims description 54
- 238000012986 modification Methods 0.000 claims description 6
- 230000004048 modification Effects 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000000034 method Methods 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005304 joining Methods 0.000 description 2
- 229910000833 kovar Inorganic materials 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003534 oscillatory effect Effects 0.000 description 1
- 230000001151 other effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000005549 size reduction Methods 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 210000000707 wrist Anatomy 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
Landscapes
- 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)
Description
(54) TUNING FORK-TYPE QUARTZ CRYSTAL VIBRATOR
(71) We, CITIZEN WATCH COMPANY
LIMITED, a corporation organized under the laws of Japan, of No. 9-18, l-chome, Nishishinjuku, Shinjuku-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to
be particularly described in and by the following statement This invention relates to a tuning fork
type quartz crystal vibrator for use in a
quartz wristwatch.
In recent years turning fork-type quartz
crystal vibrators have come to be employed
as a time standard in quartz oscillator-type wristwatches due to their excellent properties
and reliability. However, their properties and
reliability are excellent only in so far as
compared to a free-free bar-type vibrator. In
terms of reliabilty, a frequency variation of at
most 3 ppm can be guaranteed based upon the results of shock and heat tests. The accuracy of a timepiece is generally expressed in terms
of time lost or gained per month, and quartz wristwatches which exhibit a monthly time variation of within 10 to 20 seconds are being
widely marketed.Even if a quartz wrist
watch is initially set to keep time with a
monthly time variation of zt0 seconds, the
effects of impact as well as high temperature
and humity and the like can eventually lead to a montlhy time variation of approximately 7
seconds when the tuning fork-type crystal vibrator exhibits the 3 ppm frequency variation as caused by said impact and temperature-humidity conditions. The factors which cause this variation in wristwatch timing are of course not limited to impact, temperature and humidity; frequency variation with the passage of time, frequency-temperature characteristics and the effects exerted by other components are also contributing factors.
Accordingly, even though a monthly variation of 10 seconds may be intended, there are actually many cases in which there can only be guaranteed an accuracy of from 2 to 2-5 times the standard deviation.
According to the present invention, there is provided a tuning fork-type quartz crystal vibrator comprising:
an elongate case of elliptical cross section with a major axis and a minor axis, said casing having a closed end and an open end;
an elliptical terminal plate mounted and hermetically sealed in the open end of said case and having first and second bores spaced from one another on the major axis of said terminal plate and extending in a direction parallel to the longitudinal axis of said case;
first and second lead terminals extending respectively through said first and second bores of said terminal plate, each of said lead terminals having at its inner end an enlarged portion having a flat surface which is perpendicular to the longitudinal axis of said lead terminal and has an area greater than the cross section of the portion of said lead terminal passing through said bore; and
a tuning fork type quartz crystal vibrating element having a flat base surface perpendicular to the longitudinal axis of said element, said vibrating element being disposed lengthwise in said case and rigidly supported therein by said flat base surface being bonded to said flat and surfaces of said first and second lead terminals such that the plane of the vibrating element remains parallel to and contains the major axis of said terminal plate.
The present invention will now be described by way of example only and with reference to the accompanying drawings, in which:
Figs. 1(a) and (b) show one example of a conventional tuning fork-type quartz crystal vibrator;
Figs. 2(a) and (b) show another example of the conventional quartz crystal vibrator;
Figs. 3(a) and (b) show a preferred embodiment of a quartz crystal vibrator according to the present invention for use in an electronic timepiece;
Figs. 4(a) and (b) show a modified form of the vibrator shown in Fig. 3; and
Figs. 5 (a) and (b) show a further modification of the vibrator shown in Fig. 3.
Referring now to Figs. 1 and 2, there is shown prior art tuning fork-type quarz crystal vibrators. In Fig. 1, the quartz crystal vibrator 10 comprises a case 12 having a circular cross section with its open end sealed with a terminal tag or support member 14, which supports lead terminals 16, 18. The lead terminals 16, 18 support a foot portion 20a of a tuning fork-type quartz crystal element 20. The ends of the lead terminals 16, 18 are secured to both surfaces of the foot portion 20a by some suitable means such as soldering technique. In an example of Fig. 2, the ends of the lead terminals 16, 18 are secured to the foot portion 20a at one surface thereof.In both cases it can be seen from the positional relationships that there are no portions where lead terminals 16, 18 overlap respective projected planes 22 which are orthogonal to hermetically sealed terminal tag 14 in the planes 21 of the tuning fork-type quartz crystal elements 20. Referring to Figs.
l(b) and 2(b) which are cross-sectional views perpendicular to the longitudinal direction of the quartz crystal elements, the positional relationships indicate that the ratio of the area within the confines of cases 12 to the area of the quartz crystal elements cannot be increased beyond a given limit. Accordingly, the only way to reduce the overall size of the tuning fork-type vibrator is to reduce the size of the quartz crystal element itself. How evcr, the characteristics of the quartz crystal element diminish in proportion to a reduction in its size, and production costs naturally rise.
To overcome this drawback, this invention proposes a reduction in the size of a tuning fork-type quartz crystal vibrator without greatly increasing the cost of producing the quartz crystal element while at the same time holding the deterioration in crystal characteristics to an extremely low level.
One preferred embodiment to achieve the above concept is shown in Fig. 3. A tuning fork-type quartz crystal vibrator embodying the present invention comprises a case 32 having a elliptical cross section, an elliptical terminal plate or supporting member 34 hermetically mounted to an open end of the case 32. The terminal plate 34 has bores 34a and 34b formed on the major axis of the terminal plate 34. The lead terminals 36, 38 have flattened ends 36a, 36b, respectively, to which the flat base surface 40a of a quartz crystal vibrating element 40 is rigidly connected such that vibrating surfaces remain in parallel with the major axis of the terminal plate 34.In Fig. 3, the phantom line illustrates a projected plane orthongonal to the side of hermetically scaled terminal plate 34 in the plane of the flat base surface 40tri of the tuning fork-type quartz crystal element 40, the solid line depicts the portions where lead terminals 36, 38 are joined to the quartz crystal element, and the broken line indicates the portions where lead terminals 36, 38 pass through the hermetically sealed terminal plate 34. In this case, the major portion of lead terminals 36, 38 lie in the projected plane orthogonal to the plane af the flat base surface of the crystal element 40.In the present embodimcnt, the portion at which lead terminals 36, 38 are connected to crystal element 40, and the portion of the lead terminals 36, 38 lead to the outside of the case 35 may be separately provided and then interconnected in order to obtain the completed lead terminals 36, 38.
With reference to a modified form shown in Fig. 4, lead terminals 361, 381 are passed through hermetically sealed terminal plate 34 and are configured such that their ends are substantially bent at right angles at portions 361a, 381a where they are joined to the flat base surface 40a of the tuning fork-type quartz crystal element 40. The lead terminals are designed so as to assure an elongated joint at the portion where they are connected to the crystal element 40. In this modification, the joining portions 361a, 381a of lead terminals 361, 381 are flattened so as to enlarge their joining area.
In the embodiments illustrated in Figs. 3 and 4, the quartz crystal element is supported by the lead terminals which possess a small amount of resiliency. Thus when the tuning fork quartz crystal vibrator is subjected to an external force such as impact, the lead terminals and crystal element, including the portion where they are joined, experience stress. More specifically, a gradually increasing stress is generated beginning at the vibrating ends of the tunning fork and advancing toward the boundary of the lead terminals and the hermetically sealed portion. In particular, there is no concentration of stress at portions with little breaking strength as opposed to the concentration of comparatively large stress at the joint or adjacent to the boundary between the vibrating portion of the tuning fork and its foot portion.There is accordingly little tendency for the occurence of fatal flaws such as breakage, and almost no frequency varation. Although the portion where maximum stress develops is located adjacent the boundary between the portions where the lead terminals are and are not sealed within the hermetically sealed terminal plate, a material, such as that known by the registered trade mark kovar, which possesses neither the fragility of the quartz crystal nor the poor breaking strength of solder is made use of at this portion. Hence, it is possible to furnish sufficient resistance against impact so long as the impact is within the tolerance of the plastic deformation of the kovar material itself.
Fig. 5 shows another modified form of a tuning fork type quartz crystal vibrator.
Crystal vibrator element 40 is supported at its foot portion 40c by two lead terminals 361ill, 38111 having channel-shaped cross-sections
361"a, 381lea and being fabricated from two fine metal rods so as to individually embrace the foot portion 40c, the cross-section area of each lead terminal adjacent to the point where they are joined to the crystal vibrator element 40 being larger than the cross section area at all other portions of the terminals. Moreover, the crystal vibrator element 40 and lead terminals 36111, 38111 are secured to each other by an adhesive 42 along substantially the entire surface of both surfaces adjacent the lower end of the foot portion of the vibrator element.
With the use of this particular modification, there is very little frequency since the adhesive 42 absorbs stress transmitted across the lead terminals 35111, 381ill when an external force is app]ied. Furthermore, the crystal vibrator element 40 will not break since it is not subjected to maximum stress, even when an impact force is applied from the side of the case 32. Other effects of this modification may be summarized as follows:
(1) Both surfaces 40b at the end of the foot portion 40c of the vibrator element 40 are mechanically embraced so as to offset any deficiency which the adhesive may have with respect to shearing force. Accordingly, the lead terminals will not separate from the vibrator element.
(2) If the lead terminals are processed by a headder machine, the terminals can be processed in the same amount of time as fine rods which have uniform cross-sections and unchanged cross-sectional figuration at their ends.
The advantages of the present invention will now be described in consideration of the characteristics, production cost and sizereduction of the tuning fork-type quartz crystal vibrator.
It can be appreciated that the present invention allows the dimensions of the case to reduced with respect to the dimensions of the crystal element.
Advantages regarding characteristics are as follows. Although the characteristics of a tuning fork quartz crystal vibrator are in many cases generally typified by an equivalent series resistance, mechanical losses increase in proportion to the reduction in crystal element size; hence, there is a tendency for the equivalent series resistance to increase. This increase in resistance can of course be off-set by a higher level of production technique such as quartz crystal processing, electrode patterning and tuning fork crystal element assembly techniques; however, this requires higher expenditures for facilities and material and a higher level of skill. Accordingly, disadvantages with regard to production cost cannot be denied.On the other hand, since the maximum oscillatory displacement of the crystal element in a wristwatch equipped a tuning fork-type quartz crystal vibrator does not exceed 05 clam, the ratio of the crystal element volume to the internal space of the envelope can be brought close to unity if the acoustic resistance withing the envelope is held within a given limit (if., if a design is adopted in which there is no deterioration in the degree of vacuum within the envelope).
Generally speaking, time is a factor in the cost of producing a tuning fork-type quartz vibrator. The time prescribed for main line production including cutting of the crystal element from a quartz crystal, patterning, assembly, frequency adjustment and sealing, and the time prescribed for the parts production line including the construction of the envelope inclusive of the hermetically sealed terminals and case, is related by the approximate ratio 5:1-10:1. Rather than dealing with the difficulties which would be encountered by reducing the size of the tuning fork quartz element, it is more advantageous in terms of total cost even if fabrication is slightly more complicated, to maintain the dimensions of the tuning fork crystal element and instead adopt a main line process in which the configuration of the case and hermetically sealed terminals are altered.
Since the lead terminals are supported by the elliptical terminal plate on the major axis of the elliptical terminal plate, the distance between two lead terminals is maintained at a larger value, presenting an improved humiditiy characteristic in an oscillator circuit using a quartz crystal vibrator in an electronic timepiece. In cases were the humidity varies in environmental conditions of the watch, the suspended capacity such as the capacity between the two lead terminals of the quartz crystal vibrator varies, resulting in variations in an oscillating frequency of the oscillator circuit. These variations in the suspended capacity and the oscillating frequency increase in value as the distance between the two lead terminals of the vibrator decreases.In the present invention, the distance between the two lead terminals of the vibrator has the maximum value due to inherent arrangement of the lead terminals with respect to the terminal plate or the cross section of the case housing the vibrating element even though the vibrator is miniaturized. Therefore, the variations in the suspended capacity between the two lead terminals and the oscillating frequency are minimized in value so that the humidity characteristic of the oscillator circuit is improved.
Further, if the two lead terminals are not spaced from each other by a sufficient distance, an electrical leak will be caused therebetween. In general, the value of a feedback resistance in the oscillator circuit of the electronic timepiece is usually set to a value in the order of several MQ. Accordingly, if the distance between the two lead terminals is extremely small in value, the value of the resistance equivalently connected between the two lead terminals will decreases to a value in the order of several MQ, with a resultant increase in the power consumption of the oscillator circuit or the decrease in the Q value. The quartz crystal vibrator of the present invention has two lead terminals spaced from each other by a sufficient extent, so that various problem arising from the miniaturization of the vibrator can be solved.
The inherent arrangement of the lead terminals with respect to the elliptical terminal plate makes it possible to provide a quartz crystal vibrator having the thickness of less than 1 5 mm in the direction of minor axis of the terminal plate. Another advantage is that the assembling of the vibrator is easy to perform and the rigidity of the supporting structure is increased because the lead terminals are arranged along the major axis of the terminal plate of the vibrator to provide a sufficient space therebetween.
While the present invention has been described with reference to particular embodiments by way of example, it should be noted that various other changes or modifications may be made without departing from the scope of the present invention.
WHAT WE CLAIM IS:-- 1. A tuning fork type quartz crystal vibrator comprising:
an elongate case of elliptical cross section with a major axis and a minor axis, said
casing having a closed end and an open end;
an elliptical terminal plate mounted and hermetically sealed in the open end of said
case and having first and second bores spaced
from one another on the major axis of said
terminal plate and extending in a direction
parallel to the longitudinal axis of said case;
first and second lead terminals extending respectively through said first and second bores of said terminal plate, each of said lead terminals having at its inner end an enlarged portion having a flat surface which is perpendicular to the longitudinal axis of said lead terminal and has an area greater than the cross section of the portion of said lead terminal passing through said bore; and
a tuning fork type quartz crystal vibrating element having a flat base surface perpendicular to the longitudinal axis of said element, said vibrating element being disposed lengthwise in said case and rigidly supported therein by said flat base surface being bonded to said flat end surfaces of said first and second lead terminals such that the plane of the vibrating element remains parallel to and contains the major axis of said terminal plate.
2. A tuning fork type quartz crystal vibrator as claimed in claim 1, in which each of said first and second lead terminals has an end bent at right angles to provide an elongaged joint at a portion where the first and second lead terminals are connected to the flat base surface of said vibrating element.
3. A tuning fork type quartz crystal vibrator as claimed in claim 1, in which said first and second lead terminals have channelshaped ends to embrace a foot portion of said vibrating element.
4. A tuning fork type quartz crystal vibrator substantially as shown and described with reference to Figures 3 to 5 of the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (4)
1. A tuning fork type quartz crystal vibrator comprising:
an elongate case of elliptical cross section with a major axis and a minor axis, said
casing having a closed end and an open end;
an elliptical terminal plate mounted and hermetically sealed in the open end of said
case and having first and second bores spaced
from one another on the major axis of said
terminal plate and extending in a direction
parallel to the longitudinal axis of said case;
first and second lead terminals extending respectively through said first and second bores of said terminal plate, each of said lead terminals having at its inner end an enlarged portion having a flat surface which is perpendicular to the longitudinal axis of said lead terminal and has an area greater than the cross section of the portion of said lead terminal passing through said bore; and
a tuning fork type quartz crystal vibrating element having a flat base surface perpendicular to the longitudinal axis of said element, said vibrating element being disposed lengthwise in said case and rigidly supported therein by said flat base surface being bonded to said flat end surfaces of said first and second lead terminals such that the plane of the vibrating element remains parallel to and contains the major axis of said terminal plate.
2. A tuning fork type quartz crystal vibrator as claimed in claim 1, in which each of said first and second lead terminals has an end bent at right angles to provide an elongaged joint at a portion where the first and second lead terminals are connected to the flat base surface of said vibrating element.
3. A tuning fork type quartz crystal vibrator as claimed in claim 1, in which said first and second lead terminals have channelshaped ends to embrace a foot portion of said vibrating element.
4. A tuning fork type quartz crystal vibrator substantially as shown and described with reference to Figures 3 to 5 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15173976U JPS5370166U (en) | 1976-11-12 | 1976-11-12 | |
| JP8514877A JPS5421187A (en) | 1977-07-18 | 1977-07-18 | Supporting construction of diapason type crystal oscillator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1593774A true GB1593774A (en) | 1981-07-22 |
Family
ID=26426175
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB4701477A Expired GB1593774A (en) | 1976-11-12 | 1977-11-11 | Tuning fork-type quartz crystal vibrator |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1593774A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2147456A (en) * | 1983-09-27 | 1985-05-09 | Matsushima Kogyo Kk | Piezo-electric vibrator assembly |
-
1977
- 1977-11-11 GB GB4701477A patent/GB1593774A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2147456A (en) * | 1983-09-27 | 1985-05-09 | Matsushima Kogyo Kk | Piezo-electric vibrator assembly |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |