GB1582507A - Piezoelectric vibrator driving circuit arrangements piezo-electrically driven sound generators and electronic timepieces including the same - Google Patents

Piezoelectric vibrator driving circuit arrangements piezo-electrically driven sound generators and electronic timepieces including the same Download PDF

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Publication number
GB1582507A
GB1582507A GB2190578A GB2190578A GB1582507A GB 1582507 A GB1582507 A GB 1582507A GB 2190578 A GB2190578 A GB 2190578A GB 2190578 A GB2190578 A GB 2190578A GB 1582507 A GB1582507 A GB 1582507A
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United Kingdom
Prior art keywords
circuit
sound
piezo
coil
vibrator
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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
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GB2190578A
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Seikosha KK
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Seikosha KK
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Publication date
Application filed by Seikosha KK filed Critical Seikosha KK
Priority to GB2190578A priority Critical patent/GB1582507A/en
Publication of GB1582507A publication Critical patent/GB1582507A/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B3/00—Audible signalling systems; Audible personal calling systems
    • G08B3/10—Audible signalling systems; Audible personal calling systems using electric transmission; using electromagnetic transmission
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B06B1/0223—Driving circuits for generating signals continuous in time
    • B06B1/023—Driving circuits for generating signals continuous in time and stepped in amplitude, e.g. square wave, 2-level signal
    • G—PHYSICS
    • G04—HOROLOGY
    • G04G—ELECTRONIC TIME-PIECES
    • G04G13/00—Producing acoustic time signals
    • G04G13/02—Producing acoustic time signals at preselected times, e.g. alarm clocks
    • G04G13/021—Details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/50—Application to a particular transducer type
    • B06B2201/55—Piezoelectric transducer

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electromagnetism (AREA)
  • Electromechanical Clocks (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO PIEZO-ELECTRIC VIBRATOR DRIVING CIRCUIT ARRANGEMENTS, PIEZO-ELECTRICALLY DRIVEN SOUND GENERATORS AND ELECTRONIC TIMEPIECES INCLUDING THE SAME (71) We, KABUSHIKI KAISHA SEIKOSHA, a Japanese Company, of 6-21, 2-chome, Kyobashi, Chuo-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 piezo-electric vibrator driving circuit arrangements, piezoelectrically driven sound generators, and electronic timepieces including the same and has for its main object to provide improved and simple piezo-electrical vibrator driving circuits capable of driving a vibrator with more driving force than is obtainable with known comparable driving circuits as at present in common use.
Although the invention is not limited exclusively to its application thereto, it is particularly advantageous for and primarily intended for application to the sound alarms of wrist watches and similar small electronic timepieces fitted with sound alarms.
According to one aspect of this invention there is provided a piezo-electric vibrator driving circuit arrangement including, a piezo-electric vibrator; a circuit comprising a coil and a diode in series said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
According to another aspect of this invention there is provided a piezo-electrically driven sound generator arrangement including a piezo-electric vibrator driving the sound producing element of said generator; a circuit comprising a coil and a diode in series, said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
The invention is illustrated in and explained in connection with the accompanying drawings, in which: Figure 1 is a circuit diagram of one embodiment of the invention; Figures 2, 4 and 6 are explanatory graphical figures. In Figures 2 and 6 v is voltage and t is time; Figure 3 is a face view of a piezo-electric sound producer comprising a piezo-electric ceramic vibrator stuck on a metal sound producing vibration plate; and Figure 5 shows a known circuit in common use for driving a piezo-electric vibrator.
Referring first to Figure 5 which, as above stated, shows a transistor circuit for driving a piezo-electric vibrator (for example for providing operating power to the coil L of a sound generator). There is a transistor Tri to the base of which is applied through a resistor a pulsed wave form as shown at A in the upper part of Figure 6. P 1 is the piezo-electric vibrator across which occurs a damped oscillation voltage as shown at B in the lower part of Figure 6. The coil L1, assumed to be the coil of a sound generator, is connected across the vibrator P1 and between a point +E of positive potential and the collector of transistor Tri. The emitter of the transistor is'earthed.With this circuit, as will be apparent from Figure 6B, electric energy is given to the piezo-electric vibrator P, only during the narrow pulses occurring at the trailing edges of the pulses in Figure 6A and in consequence it is difficult to obtain much driving force for the vibrator. This is a serious defect in many cases; for example, if the driving circuit is to supply electric power to a sound generator, it is very difficult to obtain a desirably high level of sound.Of course if the number of turns of the coil L1 is increased the sound level will also be increased but the expedient of increasing the number of turns in order to increase the sound level is not a satisfactory one to adopt in cases in which the sound generator is required to be of very small size - for example in the case in which the sound generator is to be the source of the alarm sound in a wrist watch or other small timepiece fitted with an alarm. It is also possible to increase the sound level by using a transformer in the driving circuit for driving the piezo-electric vibrator, but this expedient also has the defect of involving the provision of more space than is desirable or available in many cases.
Referring now to Figure 1 which shows one embodiment of this invention, a pulsed signal as shown by the wave form A in the upper part of Figure 2 is applied at a terminal a and thence through a resistor R to the base of a transistor Tr2, the collector of which is connected through a coil L2 (assumed to be the coil of a sound generator) and a diode d, poled as shown, to the positive terminal +E of a potential source.
The emitter of the transistor is earthed. P2 is a piezo-electric vibrator which is connected across the series circuit of coil L7 and diode d. When the transistor Tr2 is switched ON by an applied pulse signal on its base, current flows through the coil L7 and diode d from the DC voltage source connected to terminal +E. When, however, the transistor Tr2 is turned OFF at the trailig edge of each pulse in the wave form A, reversed induced voltage represented by the wave form B of Figure 2, is produced in the coil L2 and forward biasses the diode d. Consequently an induced voltage is applied to the piezoelectric vibrator P2.As will be seen from a comparison of the wave forms B of Figures 2 and 6, the energy given to the piezo-electric vibrator by the circuit of Figure 1 is far more than that given to it by the known circuit of Figure 5.
Experiment has confirmed the substantial nature of the improvement obtainable with the invention. The experiments were performed with a sound generator (for the sound alarm of an electronic watch) as represented in Figure 3. This generator comprised a metal vibration plate ii on which a ceramic piezo-electric vibrator m was stuck. The plate n was made of stainless steel and had a diameter and thickness of 14 mm and 0.1 mm respectively. The ceramic piezo-electric vibrator in was of rectangular shape with a length. breadth and thickness of 10 mm, 2 mm and 0.2 mm respectively.
The results obtained when this sound generator was driven by the known circuit of Figure 5 were compared with those obtained when it was driven by the improved circuit of Figure 1. In both circuits the coils (Ll in Figure 5 and L2 in Figure 1) were alike, each having 1400 turns of wire of a diameter of 0.05 mm. In both circuits voltage at +E was 1.5 volts. In the tests the metal vibration plate n was put in the resonant condition and the sound levels produced over a range of input pulse frequencies to the transistors (Tri in the case of Figure 5 and Tr2 in the case of Figure 1) were measured at a distance of 10 cms from the face of the sound generator. The results are shown graphically in Figure 4 in which the ordinates p are sound pressure levels in decibels (dB) and the abscissae are input frequencies f in KHz.Curve A shows the results obtained when the improved driving circuit of Figure 1 was used and curve B shows the results obtained when the known circuit of Figure 5 was used. The improvement obtained by this invention will be at once apparent.
In Figure 1 the switching element used was the transistor Tr2 but, as will be apparent to those skilled in the art, any similarly operating switching element known per se could be used.
As will now be appreciated the invention may be used to obtain an increased sound output from a sound generator having a given number of turns in its coil or it may be used to provide a given sound output from a sound generator having a reduced number of turns in its coil.
WHAT WE CLAIM IS: 1. A piezo-electric vibrator driving circuit arrangement including a piezo-electric vibrator; a circuit comprising a coil and a diode in series said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
2. A piezo-electrically driven sound generator arrangement including a piezoelectric vibrator driving the sound producing element of said generator; a circuit comprising a coil and a diode in series, said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
3. An arrangement as claimed in claim 1 or 2 wherein the diode is so connected as to be forwardly biased with respect to the voltage supply source.
4. An arrangement as claimed in any of the preceding claims wherein the switching means is constituted by a transistor.
5. An alarm type electronic timepiece
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. level of sound. Of course if the number of turns of the coil L1 is increased the sound level will also be increased but the expedient of increasing the number of turns in order to increase the sound level is not a satisfactory one to adopt in cases in which the sound generator is required to be of very small size - for example in the case in which the sound generator is to be the source of the alarm sound in a wrist watch or other small timepiece fitted with an alarm. It is also possible to increase the sound level by using a transformer in the driving circuit for driving the piezo-electric vibrator, but this expedient also has the defect of involving the provision of more space than is desirable or available in many cases. Referring now to Figure 1 which shows one embodiment of this invention, a pulsed signal as shown by the wave form A in the upper part of Figure 2 is applied at a terminal a and thence through a resistor R to the base of a transistor Tr2, the collector of which is connected through a coil L2 (assumed to be the coil of a sound generator) and a diode d, poled as shown, to the positive terminal +E of a potential source. The emitter of the transistor is earthed. P2 is a piezo-electric vibrator which is connected across the series circuit of coil L7 and diode d. When the transistor Tr2 is switched ON by an applied pulse signal on its base, current flows through the coil L7 and diode d from the DC voltage source connected to terminal +E. When, however, the transistor Tr2 is turned OFF at the trailig edge of each pulse in the wave form A, reversed induced voltage represented by the wave form B of Figure 2, is produced in the coil L2 and forward biasses the diode d. Consequently an induced voltage is applied to the piezoelectric vibrator P2.As will be seen from a comparison of the wave forms B of Figures 2 and 6, the energy given to the piezo-electric vibrator by the circuit of Figure 1 is far more than that given to it by the known circuit of Figure 5. Experiment has confirmed the substantial nature of the improvement obtainable with the invention. The experiments were performed with a sound generator (for the sound alarm of an electronic watch) as represented in Figure 3. This generator comprised a metal vibration plate ii on which a ceramic piezo-electric vibrator m was stuck. The plate n was made of stainless steel and had a diameter and thickness of 14 mm and 0.1 mm respectively. The ceramic piezo-electric vibrator in was of rectangular shape with a length. breadth and thickness of 10 mm, 2 mm and 0.2 mm respectively. The results obtained when this sound generator was driven by the known circuit of Figure 5 were compared with those obtained when it was driven by the improved circuit of Figure 1. In both circuits the coils (Ll in Figure 5 and L2 in Figure 1) were alike, each having 1400 turns of wire of a diameter of 0.05 mm. In both circuits voltage at +E was 1.5 volts. In the tests the metal vibration plate n was put in the resonant condition and the sound levels produced over a range of input pulse frequencies to the transistors (Tri in the case of Figure 5 and Tr2 in the case of Figure 1) were measured at a distance of 10 cms from the face of the sound generator. The results are shown graphically in Figure 4 in which the ordinates p are sound pressure levels in decibels (dB) and the abscissae are input frequencies f in KHz.Curve A shows the results obtained when the improved driving circuit of Figure 1 was used and curve B shows the results obtained when the known circuit of Figure 5 was used. The improvement obtained by this invention will be at once apparent. In Figure 1 the switching element used was the transistor Tr2 but, as will be apparent to those skilled in the art, any similarly operating switching element known per se could be used. As will now be appreciated the invention may be used to obtain an increased sound output from a sound generator having a given number of turns in its coil or it may be used to provide a given sound output from a sound generator having a reduced number of turns in its coil. WHAT WE CLAIM IS:
1. A piezo-electric vibrator driving circuit arrangement including a piezo-electric vibrator; a circuit comprising a coil and a diode in series said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
2. A piezo-electrically driven sound generator arrangement including a piezoelectric vibrator driving the sound producing element of said generator; a circuit comprising a coil and a diode in series, said circuit being connected in parallel with said vibrator; a connection between one end of said circuit and a voltage supply source; and pulse actuated switching means connected to the other end of said circuit and switching ON and OFF in response to pulse signals applied thereto.
3. An arrangement as claimed in claim 1 or 2 wherein the diode is so connected as to be forwardly biased with respect to the voltage supply source.
4. An arrangement as claimed in any of the preceding claims wherein the switching means is constituted by a transistor.
5. An alarm type electronic timepiece
having a sound generating alarm driven by a driving circuit arrangement as claimed in claim 1.
6. An alarm type electronic timepiece having a piezo-electrically driven alarm sound generator arrangement as claimed in claim 2.
7. A piezo-electric vibrator driving circuit arrangement substantially as herein described and illustrated in Figure 1 of the accompanying drawings.
GB2190578A 1978-05-24 1978-05-24 Piezoelectric vibrator driving circuit arrangements piezo-electrically driven sound generators and electronic timepieces including the same Expired GB1582507A (en)

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Application Number Priority Date Filing Date Title
GB2190578A GB1582507A (en) 1978-05-24 1978-05-24 Piezoelectric vibrator driving circuit arrangements piezo-electrically driven sound generators and electronic timepieces including the same

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Application Number Priority Date Filing Date Title
GB2190578A GB1582507A (en) 1978-05-24 1978-05-24 Piezoelectric vibrator driving circuit arrangements piezo-electrically driven sound generators and electronic timepieces including the same

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GB1582507A true GB1582507A (en) 1981-01-07

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987001480A1 (en) * 1985-09-03 1987-03-12 Ncr Corporation Sound generating system for a keyboard
US4797932A (en) * 1987-11-23 1989-01-10 Ncr Corporation Speaker volume control apparatus and method
EP1036600A1 (en) * 1997-12-04 2000-09-20 Namiki Seimitsu Houseki Kabushiki Kaisha Device for driving vibration actuator
EP1128239A1 (en) * 2000-02-24 2001-08-29 Asulab S.A. Portable object, in particular time piece, incorporating a piezo-electric transducer for manually introducing data
SG96198A1 (en) * 2000-02-24 2003-05-23 Asulab Sa Portable object such as, in particular, a timepiece, including a piezoelectric transducer for entering data manually

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987001480A1 (en) * 1985-09-03 1987-03-12 Ncr Corporation Sound generating system for a keyboard
US4694725A (en) * 1985-09-03 1987-09-22 Ncr Corporation Sound generating system for a keyboard
US4797932A (en) * 1987-11-23 1989-01-10 Ncr Corporation Speaker volume control apparatus and method
EP1036600A1 (en) * 1997-12-04 2000-09-20 Namiki Seimitsu Houseki Kabushiki Kaisha Device for driving vibration actuator
EP1036600A4 (en) * 1997-12-04 2007-11-28 Namiki Precision Jewel Co Ltd Device for driving vibration actuator
EP1128239A1 (en) * 2000-02-24 2001-08-29 Asulab S.A. Portable object, in particular time piece, incorporating a piezo-electric transducer for manually introducing data
SG96198A1 (en) * 2000-02-24 2003-05-23 Asulab Sa Portable object such as, in particular, a timepiece, including a piezoelectric transducer for entering data manually
US6813223B1 (en) 2000-02-24 2004-11-02 Asulab S.A. Portable object such as, in particular, a timepiece, including a piezoelectric transducer for entering data manually

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PS Patent sealed
PE20 Patent expired after termination of 20 years

Effective date: 19980523