EP4194960A1 - Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder - Google Patents

Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder Download PDF

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Publication number
EP4194960A1
EP4194960A1 EP21213832.5A EP21213832A EP4194960A1 EP 4194960 A1 EP4194960 A1 EP 4194960A1 EP 21213832 A EP21213832 A EP 21213832A EP 4194960 A1 EP4194960 A1 EP 4194960A1
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EP
European Patent Office
Prior art keywords
electrodes
piezoelectric
spiral spring
pair
electrode
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.)
Pending
Application number
EP21213832.5A
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English (en)
French (fr)
Inventor
Alexandre DIDIER
François Gueissaz
Elias Laforge
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Swatch Group Research and Development SA
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Swatch Group Research and Development SA
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 Swatch Group Research and Development SA filed Critical Swatch Group Research and Development SA
Priority to EP21213832.5A priority Critical patent/EP4194960A1/de
Priority to US17/939,511 priority patent/US20230185242A1/en
Priority to JP2022159274A priority patent/JP7499817B2/ja
Priority to CN202211296739.2A priority patent/CN116263572A/zh
Publication of EP4194960A1 publication Critical patent/EP4194960A1/de
Pending legal-status Critical Current

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    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/06—Oscillators with hairsprings, e.g. balance
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/06—Oscillators with hairsprings, e.g. balance
    • G04B17/063—Balance construction
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/04—Oscillators acting by spring tension
    • G04B17/06—Oscillators with hairsprings, e.g. balance
    • G04B17/066—Manufacture of the spiral spring
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/20—Compensation of mechanisms for stabilising frequency
    • G04B17/22—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature
    • G04B17/227—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature composition and manufacture of the material used
    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B17/00—Mechanisms for stabilising frequency
    • G04B17/32—Component parts or constructional details, e.g. collet, stud, virole or piton
    • G—PHYSICS
    • G04—HOROLOGY
    • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
    • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials
    • G04D3/0069—Watchmakers' or watch-repairers' machines or tools for working materials for working with non-mechanical means, e.g. chemical, electrochemical, metallising, vapourising; with electron beams, laser beams

Definitions

  • the invention relates to a piezoelectric spiral spring for a self-regulation circuit of the oscillation frequency of an oscillating mechanical system or an energy recovery circuit or a motor circuit for the actuation of the movement or its automatic maintenance.
  • the invention also relates to a method of manufacturing a piezoelectric spiral spring.
  • the oscillating mechanical system can be a balance wheel on which is mounted a spiral spring, one end of which is fixed to the axis of rotation of the balance wheel and the other end is fixed on a fixed element of a plate.
  • the mechanical system is maintained in oscillation by means of a generally mechanical source of energy, which may be a barrel driving a train of gears with an escape wheel cooperating with a rotary anchor.
  • the balance wheel with the spiral spring coupled to the escapement can thus form a regulating member of a timepiece movement.
  • the patent FR 2 119 482 describes an oscillating mechanical system of a piezoelectric element.
  • This piezoelectric element is preferably arranged on a spiral spring connected to a pendulum.
  • PZT piezoelectric material
  • a voltage converter makes it possible to supply an alternating voltage to the piezoelectric element to generate alternately a compression force and an extension force to the spring in order to adjust the oscillation of the balance wheel connected to the spiral spring.
  • THE figures 1 and 2 of the prior art represent a device 1, which comprises an oscillating mechanical system 2, 3 and a circuit 10 for self-regulation of the oscillation frequency fosc of the oscillating mechanical system as described in the patent EP 2 590 035 B1 .
  • the oscillating mechanical system comprises a balance wheel 2, which is formed of a metal ring connected for example by three arms 5 to an axis of rotation 6, and a spiral spring 3, on which is arranged a piezoelectric element or an electro-active polymer element.
  • a first end 3a of spiral spring 3 is held fixed by a peak 4 of a balance bridge. This balance bridge is attached to the watch movement plate.
  • a second end 3b of spiral spring 3 is fixed directly to axis of rotation 6 of the balance wheel.
  • Piezoelectric or electro-active polymer layers 23, 23' are deposited on two side faces of the metal strip 24, which can complicate its production.
  • the patent EP 3 629 103 B1 describes a piezoelectric spiral spring 70 of a timepiece.
  • the spiral spring 70 shown in cross section, comprises a central body 72 of silicon, a layer of silicon oxide 74 deposited on the surface of the central body to thermally compensate the spiral spring, a conductive layer 76 deposited on the oxide layer of silicon, and a piezoelectric material deposited in the form of a piezoelectric layer 78 on the conductive layer 76.
  • Two electrodes 20a and 22a are arranged on the piezoelectric layer 78 respectively on the two lateral sides of the spiral spring.
  • a first part 80a and a second part 80b of the piezoelectric layer respectively extend over two lateral sides of the central body 72 and have structures respective crystallographic which are symmetrical relative to a median plane 84 parallel to these two lateral sides.
  • the piezoelectric layer has two same axes of respective piezoelectric polarizations 82a, 82b which are perpendicular to the piezoelectric layer and in opposite directions.
  • the production of such a piezoelectric spiral spring structure is complicated and time-consuming to produce, which constitutes a drawback.
  • the piezoelectric layers can present a texturing deviated by an angle of several tens of degrees with respect to the normal to the flank.
  • the piezoelectric effect is lessened, because only the projection on the direction of the electric field contributes to it.
  • the resonance frequency of the spiral balance wheel is sensitive to the stiffness of the spiral spring, which depends on its thickness, cubed.
  • the typical reproducibility of a deposition imposes a final frequency setting state after the deposition of the piezoelectric layers.
  • material jet depositions have a thickness variation of several percent on the surface of the substrates, which complicates the precise correction of the thickness of a deposited layer.
  • the object of the invention is therefore to provide a piezoelectric spiral spring that is easy to produce for a circuit for self-regulating the oscillation frequency of an oscillating mechanical system to precisely regulate the oscillation frequency of the oscillating mechanical system, with a number limited number of components and to overcome the aforementioned drawbacks of the state of the art.
  • the piezoelectric spiral spring is also provided for an energy recovery circuit or for a motor circuit for actuating the movement or for its automatic maintenance.
  • the invention relates to a piezoelectric spiral spring for a circuit for self-regulation of the oscillation frequency of an oscillating mechanical system or an energy recovery circuit or a motor circuit for actuating the movement or its automatic maintenance, which includes the features mentioned in independent claim 1.
  • An advantage of such a piezoelectric spiral spring according to the invention lies in the fact that it can be produced easily, because the deposition of the piezoelectric layer is easily controllable if it is deposited on a face from above, or even from below. It is also easier to increase the thickness of the piezoelectric layers or to increase their length by depositing on the top or bottom faces.
  • edges of the edges of the coil of the spring are not touched, which are likely to cause problems of cracks in the piezoelectric layer, as everything is deposited on the top face, even from below, the problems of cracks are reduced.
  • Another advantage of carrying out the deposition of a piezoelectric layer on a top face is that one benefits from a better normally perpendicular crystalline orientation on the top face than on the side faces where the orientation is inclined.
  • the homogeneity of the deposit on the entire wafer (wafer) and on each turn is much greater. It does not depend on the space between the different coils of the spiral spring.
  • the deposition of a piezoelectric layer on the side faces the smaller the space between the turns, the more difficult it is to deposit such a layer on these side faces. In this case, there is a shadowing effect for the deposition of the layers on the side faces which may also be too thin in thickness and where short circuits may appear for a layer of insufficient thickness. It is therefore an advantage to carry out the deposition of a piezoelectric layer on a top face for the control of the accuracy of manufacture, and the difference between the designs and the reality is limited.
  • Another advantage is that it is now easier to deposit piezoelectric layers in materials that are difficult to structure on the top face compared to the side faces.
  • a global manufacturing process from above comprising the structuring of the layers and the etching and protection of the structures, is easier than a non-standard structuring of the sides of the turns.
  • the invention also relates to a method of manufacturing a piezoelectric spiral spring, which comprises the characteristics of one of independent claims 14 and 15.
  • a support in the form of a base plate for example made of SOI (Silicon-on-Insulator) as the first step.
  • SOI Silicon-on-Insulator
  • THE figures 4a and 4b represent a three-dimensional partial view of a portion of a turn of the piezoelectric spiral spring 3 and a cross section of this turn of a first embodiment of the piezoelectric spiral spring 3.
  • the spiral spring 3 comprises several turns and is connected to a pendulum not shown to form an oscillating mechanical system.
  • a first end of the spiral spring is fixed to a balance bridge, while the second end is fixed to the balance shaft.
  • the spiral spring 3 appears as in a plane between its two ends.
  • the piezoelectric spiral spring 3 comprises in this first embodiment, on a top face of the spiral spring, two pairs of electrodes 8a, 8b, 8c, 8d of which the first electrodes 8a and 8b of the two pairs of electrodes side by side are attached directly to the top face of the spiral spring.
  • the first piezoelectric layer 7 is fixed between the first electrode 8a and the second electrode 8c of the first pair of electrodes, whereas the second piezoelectric layer 7' distinct from the first layer is fixed between the first electrode 8b and the second electrode 8d of the second pair of electrodes.
  • the silicon is etched on an SOI (or Quartz) wafer to obtain the shape of the spiral spring 3 with the insulation underneath, which comprises on the one hand an oxide layer SiO2 and on the other share a base silicon wafer.
  • SOI or quartz wafer can advantageously be covered with an insulating layer of the SiO2 type, with a thickness of the order of 500 nm, to avoid any interference between the activation of the piezoelectric layers and the substrate used to produce the spiral spring 3.
  • the SOI wafer may have a thickness of around 500 ⁇ m.
  • the deposition and structuring of the electrodes 8a, 8b, 8c, 8d and of the piezoelectric layers can be carried out. 7, 7' on a top face of the spiral spring.
  • Other types of substrates can be envisaged, such as ceramics or composites by adapting the methods of manufacture of the spiral spring.
  • the first electrode 8a of the first pair of electrodes and the first electrode 8b of the second pair of electrodes are arranged or deposited on the top face 20 of the piezoelectric spiral spring 3 in plan.
  • the first electrodes 8a and 8b are regularly spaced from each other and each follow the shape of turns from a first end of the spiral spring and in the direction of the second end of the spiral spring.
  • the first electrodes 8a and 8b of the two pairs of electrodes are of a substantially equivalent length and over part of the length of the spiral spring from the first end of said spiral spring.
  • the length of the first electrodes 8a, 8b of the two pairs of electrodes extends from the first end to a second end of the piezoelectric spiral spring 3.
  • the first piezoelectric layer 7 is deposited directly on the first electrode 8a of the first pair and preferably of equivalent shape to said first electrode 8a over at least part of the length of the piezoelectric spiral spring 3.
  • the second piezoelectric layer 7' is deposited directly on the first electrode 8b of the second pair of electrodes and preferably of equivalent shape to said first electrode 8b over at least part of the length of the piezoelectric spiral spring 3.
  • the second electrode 8c of the first pair of electrodes is arranged or deposited directly on the first piezoelectric layer 7 on a face opposite to that of the contact of the first electrode 8a with the first piezoelectric layer 7.
  • the second electrode 8d of the second pair of electrodes is arranged or deposited directly on the second piezoelectric layer 7' on a face opposite to that of the contact of the first electrode 8b with the second piezoelectric layer 7'.
  • the shape and length of each second electrode 8c, 8d are equivalent to the shape and length of each first electrode 8a, 8b in this first embodiment.
  • the spiral spring 3 comes from a silicon wafer (SOI) or a Quartz wafer, it can be envisaged first of all to etch the silicon or the quartz to obtain the base of the spiral spring 3. Subsequently , the electrodes 8a, 8b, 8c, 8d and the piezoelectric layers 7, 7' are deposited on a top or bottom face of the already structured spiral spring 3. In the case of a glass wafer, the base of the spiral spring 3 can first be cut by a chemically assisted laser or not from the top of the wafer.
  • the electrodes 8a, 8b, 8c, 8d and the piezoelectric layers 7, 7' can already be deposited on the silicon or quartz wafer before structuring, that is to say before etching by a DRIE process to obtain the spiral spring or before laser-assisted chemical etching from the top of the glass plate to obtain the spiral spring 3. More details will be given later in the description corresponding to the method of manufacturing the spiral spring piezoelectric 3 according to the two variants briefly presented.
  • the self-regulation circuit makes it possible to apply an adaptation voltage to generate a stress of compression -T1 on a piezoelectric layer 7 or an inverse matching voltage on the other piezoelectric layer 7' generating an extension stress T1 continuously or by determined time periods. This makes it possible to regulate the oscillation frequency of the oscillating mechanical system.
  • a first electrode 8a of a first pair of electrodes and a first electrode 8b of a second pair of electrodes are both arranged or structured on a top face 20 and preferably on a large part of the length of the spiral spring 3 at least half the length and for example over the entire length of the spiral spring 3 if it is already made on the base of the wafer.
  • the first electrodes 8a and 8b are arranged one beside the other with a predefined spacing, for example over the entire length of the spiral spring 3. No electrode is deposited on each side face 22.
  • a first piezoelectric layer 7 is subsequently deposited and then structured on the first electrode 8a of the first pair of electrodes.
  • the first piezoelectric layer is structured at the lateral dimension and at the length of the first electrode 8a of the first pair of electrodes.
  • a second piezoelectric layer 7' can be deposited or structured on the first electrode 8b of the second pair of electrodes at the same time as the first piezoelectric layer 7 or after the production of the first piezoelectric layer 7.
  • the second piezoelectric layer 7' is structured to the lateral dimension and to the length of the first electrode 8b of the second pair of electrodes.
  • a second electrode 8c of the first pair of electrodes is deposited or structured on the first piezoelectric layer 7 opposite the first electrode 8a of the first pair of electrodes.
  • the second electrode 8c is of shape and size equivalent to the first electrode 8a of the first pair of electrodes.
  • a second electrode 8d of the second pair of electrodes is deposited or structured on the second piezoelectric layer 7' facing the first electrode 8b of the second pair of electrodes.
  • the second electrode 8d is of shape and size equivalent to the first electrode 8b of the second pair of electrodes.
  • the piezoelectric spiral spring 3 can be mounted in an oscillating mechanical system.
  • the two pairs of electrodes in this embodiment are inversely polarized and alternately by a voltage source in particular to maintain a movement of the oscillating system for the oscillation of the piezoelectric spiral spring.
  • the first electrode 8a of the first pair of electrodes can be connected to the second electrode 8d of the second pair of electrodes.
  • the first electrode 8b of the second pair of electrodes can be connected to the second electrode 8c of the first pair of electrodes.
  • the first electrode 8a and the second electrode 8d can be connected to a first connection terminal arranged at a first end of the piezoelectric spiral spring 3.
  • the first electrode 8b and the second electrode 8c can be connected to a second connection terminal at the first end of the piezoelectric spiral spring 3.
  • connection terminals defined in particular at the same time as the deposits of the electrodes 8a, 8b, 8c, 8d and of the piezoelectric layer(s) 7, 7'.
  • connection terminals Preferably, two connection terminals at a first end of the piezoelectric spiral spring 3 are provided to be connected to the electrodes 8a, 8b, 8c, 8d of at least two pairs of electrodes.
  • the connection terminals are placed after the balance peak, so as not to affect the balance-spring mechanically.
  • a resistive layer of the SiO2 type is deposited at least locally on the zone where the hairspring is fixed to the eyebolt, so as to avoid any electrical short circuit.
  • An insulated piton can also be used. However, it can also be imagined to use the peg of the balance wheel directly to make the electrical connections.
  • the electrodes 8a and 8d are connected to a first terminal, for example represented by Vo-, while the electrodes 8b and 8c are connected to a second terminal, for example represented by Vo+.
  • the voltages Vo+ and Vo- are alternating voltages inverse in time with rectangular or sinusoidal signals or pulse trains to maintain the oscillation of the piezoelectric spiral spring 3.
  • the piezoelectric spiral spring 3 which is shown in figure 5 , includes features similar to those shown in figure 4b .
  • a single piezoelectric layer 7 is deposited and maintained on the first two electrodes 8a, 8b.
  • a second electrode 8c, 8d for each pair of electrodes is deposited on the piezoelectric layer 7 facing each of the respective first electrode 8a, 8b of the pairs of electrodes.
  • the piezoelectric layer 7 is deposited both over the width of the first two electrodes 8a and 8b and also on the space separating them.
  • the shape and size of the piezoelectric layer 7 is equivalent to the combined shape of the two first electrodes 8a and 8b and including the space separating them.
  • the crystalline orientation of the piezoelectric layer 7 deposited on the top face 20 of the spiral spring 3 provides a much better result than layers deposited laterally on the side faces 22 of the spiral spring. As shown at figure 8 , the crystalline orientation of the layer deposited on the side faces 22 has an inclined crystalline orientation and therefore not perpendicular like the crystalline orientation of the piezoelectric layer deposited on the top face 20 of the spiral spring.
  • the second electrode 8c of the first pair of electrodes is arranged to receive the voltage Vo+, whereas the first electrode 8a of the first pair of electrodes is arranged to receive the voltage Vo inverse of the voltage Vo+.
  • the second pair of electrodes is arranged to be inversely biased to the first pair of electrodes with the voltage Vo+ supplied to the first electrode 8b of the second pair of electrodes, whereas the second electrode 8d of the second pair of electrodes is arranged to be biased by the voltage Vo-.
  • the bias voltage supplied to the electrodes 8a, 8b, 8c, 8d from the two connection terminals is alternate.
  • the electrodes 8b and 8c are therefore alternately polarized in time by the voltage Vo+, while the electrodes 8a and 8d are alternately polarized in time by the voltage Vo-, which is inverse to the voltage Vo+ to maintain a movement of the oscillating system for the oscillation of the piezoelectric spiral spring 3.
  • the bias voltages of the electrodes can vary by rectangular signals or sinusoidal signals.
  • Finite element calculations show that it is possible, with this configuration, to excite the spiral spring 3 in a manner analogous to that of the deposit on the side faces 22 of the spiral spring. Even if the piezoelectric effect achieved with this method is less than a deposit on the side faces 22, this can be compensated by the use of materials having greater piezoelectric factors, and which cannot necessarily be successfully deposited on the side faces 22 of the spiral spring 3.
  • the method is in particular compatible with all the piezoelectric materials which can be deposited by vacuum sputtering (AIN, AIScN, PZT , and lead-free piezoelectric materials). Two variants of the manufacturing process are contemplated and further described below.
  • FIG 6 represents a cross section of a turn of the piezoelectric spiral spring 3 according to a third embodiment.
  • the first embodiment at least two pairs of electrodes are provided, of which a first electrode 8a of the first pair of electrodes is placed in contact with the top face 20 of the piezoelectric spiral spring 3 and a second electrode 8c of the first pair of electrodes is arranged on a first set of composite layers 7, 17, 27 including at least one piezoelectric layer 7, which can be one of the layers of the first layer to the last layer of the first set of layers composites.
  • a first electrode 8b of the second pair of electrodes is placed on the top face 20 of the turn while the second electrode 8d of the second pair of electrodes is placed on a second set of composite layers 7', 17', 27' including at least one piezoelectric layer 7', which can be one of the layers from the first layer to the last layer of the second set of composite layers.
  • the first set of composite layers and the second set of composite layers can have the layers arranged in series or in parallel between the two electrodes 8a and 8c of the first pair of electrodes or the two electrodes 8b and 8d of the second pair of electrodes.
  • Intermediate electrodes can also be provided between each layer of the set of composite layers to connect the layers in series or in parallel or to short-circuit one or more layers according to the desired selection. It can also be a functional layer rather than a piezoelectric layer only each layer of the set of composite layers can be made in a different material from the next layer or other planned layers.
  • the fourth embodiment is shown in figure 7 and compared to the figure 4b .
  • Two pairs of electrodes are indeed provided, but oriented differently for the first and second electrodes 8a and 8c of the first pair of electrodes and for the first and second electrodes 8b and 8d of the second pair of electrodes.
  • the top face 20 is made first of all of the first piezoelectric layer 7 and then or at the same time the second piezoelectric layer 7'. Thereafter, the first and second electrodes 8a, 8c, and 8b, 8d of the two pairs of electrodes are deposited on two opposite side faces of each piezoelectric layer 7, 7'.
  • a first piezoelectric layer 7 is arranged and biased by the first and second electrodes 8a, 8c of the first pair of electrodes vertically with respect to the top face 20. And also a second piezoelectric layer 7' is arranged and biased by the first and second electrodes 8b, 8d of the second pair of electrodes.
  • the crystalline orientation can be arranged parallel to the top face 20 unlike the second embodiment or the preceding embodiments.
  • the realization of the fourth embodiment is more complicated than the previous embodiments.
  • each piezoelectric layer or electrodes is performed on the top face 20, even if it can be performed on the bottom face, not shown.
  • other piezoelectric materials can be used, even if they do not lead to a satisfactory deposit on the side faces 22 as for the present invention the deposit is made on the top face of the wafer or directly on the face top 20 of the piezoelectric spiral spring 3.
  • the height of the spiral spring contributes to the resonance frequency of the balance-spring, in the same way as its length.
  • a deposit on the top, in particular the top face 20 is more easily controllable than on the side faces.
  • the base of the spiral spring 3 is first made by a DRIE etching operation from above the SOI wafer or quartz or chemical etching assisted by laser or pulsed laser of the glass plate. More conventionally, the spiral spring can be made first before depositing the piezoelectric layers or electrodes necessary to obtain the piezoelectric spiral spring.
  • piezoelectric layers 7, 7' (“sputtering" in English terminology), such as AIN or AIScN or PZT, as well as piezoelectric materials without lead such as KNN (solid solution formed from Potassium Niobate (KNbO3, KN) and Sodium Niobate (NaNbO3, NN), the piezoelectric layers can present a texture deviated from an angle of several tens of degrees with respect to normal to the side faces 22 of the spiral spring 3. The piezoelectric effect is thereby reduced, since only the projection onto the direction of the electric field contributes to it.
  • the use of the KNN piezoelectric material can be advantageous if it is deposited on the top face 20 of the spiral spring 3, because it can be deposited over a sufficient thickness, for example 5 ⁇ m, without great difficulty.
  • the spiral spring can be etched or structured, in particular up to a certain depth of spiral spring engraving.
  • the base of the SOI wafer is also removed by a DRIE type etching (deep reactive ion etching). From this moment the piezoelectric spiral spring is obtained with already the arrangement of the electrodes and the piezoelectric layers on the top face 20 of the spiral spring.
  • Another advantage is that one benefits from a better perpendicular crystalline orientation on the top face whereas on the side faces it is inclined. The homogeneity of the deposit on the whole of the wafer and on each turn is much greater.
  • the thickness of deposit on the side faces of the spiral spring also depends on the spacing between the coils of the spring as regards the shading effect described above. The closer the turns are, the smaller the thickness deposited on the side faces and the greater the thickness gradient on the side face. In the case of the deposition on top, the thickness of the piezoelectric layer will be almost identical on each turn. This is an advantage for controlling the accuracy of manufacture, and it limits the difference between the designs made and the reality.
  • the number of pairs of electrodes used is not limited to two. For example three or four pairs of electrodes could be used. With several pairs of electrodes, different voltage sequences can be applied to the layers, for example electrical excitation of the pairs units for the correction of the drift on the amplitude of the watch and energy recovery or capture on the two outer pairs.
  • the last step of the method may consist in removing the base silicon plate forming part of the insulator.
  • the silicon spiral spring can be connected to an oscillation frequency self-regulation circuit or to an energy recovery circuit or to a motor circuit for the actuation of the movement or its automatic maintenance. Additionally, it can be attached to a printed circuit board for connection to other system components.
  • the two connection terminals at one end of the piezoelectric spiral spring are connected to at least two pairs of electrodes 8a, 8b, 8c, 8d arranged on the top face 20 of the piezoelectric spiral spring 3.
  • the electrodes 8a and 8d are connected to a first connection terminal, while the electrodes 8b and 8c are connected to a second connection terminal.
  • the electrodes of the two pairs of electrodes and the piezoelectric layer may extend only over a first turn of the spiral spring from a first end of the spiral spring where the connection terminals are located. This is advantageous for a low power self-regulating circuit.
  • each first electrode deposited directly on the top face can be slightly wider than the second electrode deposited on the layer

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Springs (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
EP21213832.5A 2021-12-10 2021-12-10 Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder Pending EP4194960A1 (de)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP21213832.5A EP4194960A1 (de) 2021-12-10 2021-12-10 Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder
US17/939,511 US20230185242A1 (en) 2021-12-10 2022-09-07 Piezoelectric balance spring, and method for manufacturing the balance spring
JP2022159274A JP7499817B2 (ja) 2021-12-10 2022-10-03 圧電ひげぜんまい、及びひげぜんまいを製造する方法
CN202211296739.2A CN116263572A (zh) 2021-12-10 2022-10-20 压电式游丝和用于制造压电式游丝的方法

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EP21213832.5A EP4194960A1 (de) 2021-12-10 2021-12-10 Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder

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EP4194960A1 true EP4194960A1 (de) 2023-06-14

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EP21213832.5A Pending EP4194960A1 (de) 2021-12-10 2021-12-10 Piezoelektrische spiralfeder und verfahren zur herstellung dieser spiralfeder

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US (1) US20230185242A1 (de)
EP (1) EP4194960A1 (de)
JP (1) JP7499817B2 (de)
CN (1) CN116263572A (de)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2119482A5 (de) 1970-12-21 1972-08-04 Ki
CH714144A2 (fr) * 2017-09-14 2019-03-15 Swatch Group Res & Dev Ltd Elément piézoélectrique pour un circuit d'autorégulation de fréquence, système mécanique oscillant et dispositif le comprenant, et procédé de fabrication de l'élément piézoélectrique.
EP3457223A1 (de) * 2017-09-14 2019-03-20 The Swatch Group Research and Development Ltd Piezoelektrisches element für einen schaltkreis zur frequenzselbstregulierung, schwingendes mechanisches system und dieses umfassende vorrichtung
EP2590035B1 (de) 2011-11-01 2020-12-30 The Swatch Group Research and Development Ltd. Schaltkreis zur Selbstregulierung der Schwingungsfrequenz eines schwingenden mechanischen Systems, und diesen umfassende Vorrichtung
EP3629103B1 (de) 2018-09-28 2021-05-12 The Swatch Group Research and Development Ltd Uhr, die ein mechanisches uhrwerk umfasst, dessen ganggenauigkeit durch eine elektronische vorrichtung reguliert wird

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EP3457224B1 (de) 2017-09-14 2020-10-28 The Swatch Group Research and Development Ltd Piezoelektrisches element für einen schaltkreis zur frequenzselbstregulierung, schwingendes mechanisches system und dieses umfassende vorrichtung, und herstellungsverfahren eines solchen piezoelektrischen elements

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EP2590035B1 (de) 2011-11-01 2020-12-30 The Swatch Group Research and Development Ltd. Schaltkreis zur Selbstregulierung der Schwingungsfrequenz eines schwingenden mechanischen Systems, und diesen umfassende Vorrichtung
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EP3457223A1 (de) * 2017-09-14 2019-03-20 The Swatch Group Research and Development Ltd Piezoelektrisches element für einen schaltkreis zur frequenzselbstregulierung, schwingendes mechanisches system und dieses umfassende vorrichtung
EP3629103B1 (de) 2018-09-28 2021-05-12 The Swatch Group Research and Development Ltd Uhr, die ein mechanisches uhrwerk umfasst, dessen ganggenauigkeit durch eine elektronische vorrichtung reguliert wird

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