WO1995005654A1 - Vibreur - Google Patents

Vibreur Download PDF

Info

Publication number
WO1995005654A1
WO1995005654A1 PCT/GB1994/001792 GB9401792W WO9505654A1 WO 1995005654 A1 WO1995005654 A1 WO 1995005654A1 GB 9401792 W GB9401792 W GB 9401792W WO 9505654 A1 WO9505654 A1 WO 9505654A1
Authority
WO
WIPO (PCT)
Prior art keywords
coil
drive
sounder
current
armature
Prior art date
Application number
PCT/GB1994/001792
Other languages
English (en)
Inventor
Stephen Timothy Hughes
Original Assignee
Fulleon Synchrobell Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Fulleon Synchrobell Limited filed Critical Fulleon Synchrobell Limited
Priority to AU73891/94A priority Critical patent/AU7389194A/en
Priority to GB9603219A priority patent/GB2296365B/en
Publication of WO1995005654A1 publication Critical patent/WO1995005654A1/fr

Links

Classifications

    • 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
    • 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
    • B06B2201/52—Electrodynamic transducer
    • B06B2201/53—Electrodynamic transducer with vibrating magnet or coil

Definitions

  • the present invention relates to a sounder, which is a device for converting an oscillation in an electric signal to an acoustic output.
  • a loudspeaker for an audio system is one well known example of a sounder, but simpler, less bulky, sounders are needed e.g. in alarms such as fire alarms.
  • One known sounder involves an oscillating signal being fed to coils mounted on two generally parallel arms of a common core. The coils are wound on the core so that magnetic fields in opposite directions are generated, and the coils are driven so that those fields themselves alternate in direction.
  • a magnetic rocker arm is then mounted adjacent the core and coils, and a diaphragm is connected to one end of that rocker arm.
  • the end of the rocker arm will be alternately attracted to one or other of the coils.
  • the other end of the rocker arm will be alternately repelled and attracted to the other arm of the core.
  • the rocker arm will be caused to rock at a frequency determined by the alternation of the drive, thereby vibrating the diaphragm.
  • the present invention seeks to improve the efficiency of the sounder, i.e. the relationship between the electrical power input to the acoustic power output, as compared with such known sounders.
  • the present invention is concerned with the way that power is supplied to a drive coil to generate a magnetic field to cause vibration of an armature.
  • the drive coil has a second coil magnetically linked to it, e.g. by overwinding the second coil on the first or vice versa.
  • the coils are then electrically connected together, and a diode connected to the second coil such that the diode blocks current through the second coil when the drive signal (which has a predetermined polarity) is applied across to the drive coil.
  • the drive signal which has a predetermined polarity
  • the armature will be attracted to the core, and repeated application and cutting-off of that drive signal will cause the armature, and hence the diaphragm to vibrate.
  • the power stored in the magnetic system will cause a current to flow in the second coil.
  • the diode will not resist that current flow, since it is in the opposite sense to the polarity of the drive signal relative to the second coil.
  • the charge associated with that current may then be stored by a suitable storage means (e.g. a capacitor).
  • the charge stored may then be used subsequently to contribute to the drive current.
  • the majority of the energy supplied to the drive coil is returned to the supply via second coil, and thus efficient power usage can be achieved.
  • the drive and second coils are wound on a common pole piece, the drive on the armature will be the sum of the attractive effects of the drive and second coils.
  • a signal from a suitable oscillator may be used to switch the drive coil across the supply voltage so that the current in the drive coil increases approximately linearly. Then, when that current has reached a suitable level, the drive current can be cut-off, and the current in the second coil will then flow.
  • the system operates in a unipolar manner, so there is no need for the sounder to incorporate a bias magnet, as is necessary in some sounders.
  • non-conducting ferrites can be used, which is another factor contributing the efficiency of the present invention.
  • the present invention is concerned with the drive to a single drive coil.
  • the present invention is also applicable to arrangements with more than one drive coil, either by providing a second coil for each drive coil, or by providing a common second coil for all the drive coils.
  • the present invention starts from the principle that a force can be generated on an armature which extends between, but is separated from, one or more magnetic poles.
  • the present invention may use a core with first and second adjacent pole pieces, with an armature extending across the gap between those pole pieces.
  • a drive coil is mounted on one of the pole pieces.
  • a first one of the pole pieces is cylindrical and the second pole piece extends along the axis of the first pole piece.
  • the second pole piece may itself be cylindrical so that the cylindrical first and second pole pieces are concentric.
  • the drive coil may be mounted in the space between the two pole pieces and the armature be in the form of a disk with a diameter sufficiently large that it overlaps the first pole piece (it will necessarily overlap the second pole piece).
  • the first and second pole pieces thus form a common magnetic core for the drive coil.
  • a resilient diaphragm is then connected to the armature, and held so that the rest position of the diaphragm is such as to hold the armature spaced from the pole pieces, the application of the drive current will attract the armature towards the pole pieces and alternately application and removal of that drive current will cause the armature, and hence the diaphragm, to vibrate.
  • the armature and/or at least the parts of the pole pieces adjacent the armature are preferably of a ferrite material.
  • Fig. 1 shows the drive components of a sounder according to the present invention
  • Fig. 2 is a circuit diagram for driving the sounder of the present invention.
  • Figs. 3(a) to 3(c) show the timing of signals in the circuit of Fig. 2.
  • a diaphragm 10 of circular shape is mounted so that its edge is clamped by a suitable clamp 11, and a ferrite disk 12 is mounted thereon.
  • the diaphragm 10 is mounted adjacent a magnetic core 14 which has a first pole piece 16 which is cylindrical, and a second pole piece 18 which extends within the first pole piece 16 along the axis thereof.
  • the second pole piece 18 terminates in a ferrite disk 20, and the first pole piece 16 terminate is a ferrite annulus 22.
  • the disk 20 and the annulus 22 may be bonded to the rest of the pole pieces, 16,18 by adhesive layers 24,26 respectively.
  • a coil 28 is mounted on the second pole piece 18. In fact, as will be described later, the coil 28 is composed of first and second coils one overwound on the other.
  • N is the number of turns on the drive coil and I the current through it.
  • the negative sign signifies that the force is in such a direction as to reduce x.
  • the inductance L of the drive coil is given by
  • the ferrite armature 12 has a diameter of 15 mm
  • the disk 20 has a diameter of 8.5 mm
  • the annular part 22 has an inner diameter of 10.5 mm and 12.5 mm.
  • A is 6 x 10 "5 m 2
  • x is 1 x 10 "4 m.
  • the typical force requirement is 2 N.
  • NI 32.6.
  • the coil 28 is, as has previously been mentioned, made up of a drive coil 40 and a return coil 42, with the return coil 42 being overwound on the drive coil 40.
  • the drive coil 40 and the return coil 42 are connected in series tapped configuration, between a power source V and earth.
  • a diode Dl is connected in series with the return coil 42, and a capacitor Cl is connected across the power source.
  • a transistor Tl is connected in series with the drive coil 40.
  • an alternating signal V A (which is preferably a fixed frequency drive signal with e.g. a rectangular waveform) is applied to a D- type flip-flop 44 via an input circuit comprising capacitor C2, resistor Rl and diode D2.
  • the flip-flop 44 triggers the turning on of transistor Tl, causing a current flow through the drive coil 40, which drive current increases approximately linearly.
  • the current through the drive coil 40 is monitored by a comparator 46 which compares the voltage produced across a resistor R9 in series with the drive coil with the voltage across a variable resistor VR, and generates a reset signal when the current through the resistor R9 and hence through the drive coil 40 has reached a suitable value.
  • Transistor Tl is then activated to cut-off that current. At this time, no current can flow through the return coil 42, due to the effect of diode Dl.
  • the energy stored in the magnetic system including drive coil 40 and return coil 42 causes a current to flow through return coil 42 in a direction which is permitted by diode Dl. This charges capacitor Cl.
  • the energy thus stored in capacitor Cl may be used in subsequent powering of the drive coil 40.
  • the capacitor Cl is connected between the power supply and earth, and therefore charge will be extracted from that capacitor when the transistor Tl is on. Similarly, charge will be returned to the capacitor Cl when current flow is returned to current 42.
  • the charge stored in the capacitor Cl may be sufficient to provide the power source for the current in the drive coil 40, over the period where that current arises linearly up to the value set by variable resistor VR.
  • the majority of that energy will be returned to the capacitor Cl, with losses due to losses within the circuit shown in Fig. 2, and also due to the acoustic power radiated by the sounder. In practice, such power loss represents only a small proportion of the power needed to drive drive coil 40. Hence, the power input needed from the power supply during normal operation of the circuit of Fig. 2 is small.
  • the energy utilization of the sounder has a high efficiency, because much of the energy supplied to the drive coil 40 is subsequently returned to the drive circuit and thus may be re-used to drive the drive coil 40 in the next cycle.
  • a 4mA power supply may maintain the circuit in a steady state in which 100mA is delivered to the drive coil 40.
  • the exact relationship will depend on the losses in the sounder, but it has been found that, for a given input power, the acoustic power output from the sounder is much greater than can be achieved in conventional sounders.
  • the drive circuit is not sensitive to changes in the power supply V (although a voltage regulator 47 is provided). As V increases, the current needed decreases and vice versa. Thus, the circuit is relatively insensitive to changes in the drive conditions.
  • the resistor network R 5 , R 3 and V R is designed to vary the current switching threshold to maintain constant acoustic output as the power supply varies. The system does not depend on circuit resonances, and so that frequency of the output of the sounder may be freely selected by suitable selection of the input oscillation A.
  • Figs. 3(a) to 3(c) show the timing of signals in the circuit of Fig. 2.
  • the current through drive coil 40 increases linearly up to a maximum value (the peak current shown in Fig. 3(b)) which is determined by the variable resistor VR.
  • the transistor Tl then turns off as shown in Fig. 3(a), and the return current flows through the return current 42 as shown in Fig. 3(c).
  • the drive coil 40 and the return coil 42 are coaxial and adjacent the armature 12, a force will be applied to the armature 12 during the time a current is passing through the drive coil, and the time a current is passing through the return coil.
  • efficient driving of the armature 12 is achieved.
  • the present invention permits a sufficient volume to be achieved with a relatively simple drive circuit and thus offers significant advantages over known sounders.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)

Abstract

Un vibreur possède une bobine d'excitation (40) qui reçoit un signal d'excitation variable d'un circuit. Le champ magnétique résultant excite un induit (12) qui est monté sur une membrane (10) produisant un son par suite de sa vibration. Une seconde bobine (42) est connectée magnétiquement et électriquement à la bobine d'excitation (40). Une diode (D1) est connectée en série avec la seconde bobine et est disposée de sorte qu'il n'y ait pas de courant qui s'écoule dans la seconde bobine (42) lorsque le signal d'excitation (qui est unipolaire) génère un courant dans la bobine d'excitation (40). Lorsque le signal d'excitation est coupé, un courant s'écoule dans la seconde bobine (42) et une charge est emmagasinée dans un condensateur (C1). L'énergie ainsi emmagasinée peut être utilisée pour alimenter le circuit d'excitation. De cette façon, le courant utilisé par le vibreur correspond aux pertes dans le circuit et à celles qui sont dues à la puissance acoustique rayonnée par le vibreur. Etant donné que ces pertes ne représentent qu'une petite proportion du courant nécessaire pour exciter la bobine d'excitation (40), le vibreur fonctionne bien.
PCT/GB1994/001792 1993-08-16 1994-08-16 Vibreur WO1995005654A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU73891/94A AU7389194A (en) 1993-08-16 1994-08-16 Sounder
GB9603219A GB2296365B (en) 1993-08-16 1994-08-16 Sounder

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB939317012A GB9317012D0 (en) 1993-08-16 1993-08-16 Sounder
GB9317012.4 1993-08-16

Publications (1)

Publication Number Publication Date
WO1995005654A1 true WO1995005654A1 (fr) 1995-02-23

Family

ID=10740568

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/001792 WO1995005654A1 (fr) 1993-08-16 1994-08-16 Vibreur

Country Status (3)

Country Link
AU (1) AU7389194A (fr)
GB (1) GB9317012D0 (fr)
WO (1) WO1995005654A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916373A (en) * 1973-11-17 1975-10-28 Int Standard Electric Corp Ultrasonic transmitter for the remote control of radio and television receivers
DE2823155A1 (de) * 1977-05-26 1978-12-07 Seikosha Kk Elektrische steuerschaltung fuer einen piezoelektrischen schwinger
EP0054703A1 (fr) * 1980-12-23 1982-06-30 Siemens Aktiengesellschaft Circuit pour organe de positionnement piézo-électrique et analogue

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916373A (en) * 1973-11-17 1975-10-28 Int Standard Electric Corp Ultrasonic transmitter for the remote control of radio and television receivers
DE2823155A1 (de) * 1977-05-26 1978-12-07 Seikosha Kk Elektrische steuerschaltung fuer einen piezoelektrischen schwinger
EP0054703A1 (fr) * 1980-12-23 1982-06-30 Siemens Aktiengesellschaft Circuit pour organe de positionnement piézo-électrique et analogue

Also Published As

Publication number Publication date
AU7389194A (en) 1995-03-14
GB9317012D0 (en) 1993-09-29

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