CH708212B1 - Microgenerator, especially for wristwatch. - Google Patents

Abstract

The invention relates to a microgenerator, in particular for a wristwatch, comprising an oscillating mass (1), an annular element of pulses (2) cooperating in rotation with the oscillating mass (1), a fixed support (3) mounted co-axially with the annular pulse element (2) and provided with a plurality of piezoelectric plates (4) extending radially from the fixed support (3) to the annular pulse element (2), in wherein the annular pulse element (2) comprises a plurality of teeth (8) arranged radially internally in the annular element and adapted to cooperate with the free ends of the piezoelectric blades (4) during the rotation of the annular element pulses (2). The invention also relates to a watch movement for a quartz watch comprising such a microgenerator, a watch comprising such a movement and a method of manufacturing such piezoelectric blades.

Description

TECHNICAL FIELD [0001] The present invention relates to a microgenerator, a watch movement for a quartz watch, and a watch comprising such a movement, in order to convert the kinetic energy into electrical energy useful for the operation of the watch. It also relates to a method of manufacturing piezoelectric blades for said microgenerator.

STATE OF THE ART [0002] The difficulties encountered in supplying energy to electronic wrist watches are well known. Replacing the battery is often a delicate operation that must be performed by a specialist. This type of intervention is restrictive and uneconomical for the user.

The change of the battery requires, for the manufacturer, to provide openings of the watch case for example to replace the spent battery, which often impairs the initial seal of the watch. These openings and additional parts are generating additional constraints and costs for the manufacturer.

[0004] Several watches incorporating autonomous generators of electrical energy have been proposed. For example, US Pat. No. 6,144,621 describes an oscillator-powered energy generator module, similar to those used in the winding of automatic mechanical watches, which charges an accumulator, the latter supplying a quartz watch movement of the same type. known.

EP 1 821 163 relates to a watch with generator powered by an oscillating mass actuated by the movements of the wearer of the watch.

However, this type of watch has a number of disadvantages, including a higher thickness than a conventional quartz watch and a complex electromechanical part, fragile and a high manufacturing cost.

BRIEF SUMMARY OF THE INVENTION [0007] To overcome these various disadvantages, the present invention provides for solving these difficulties and for providing a watch powered by a generator free from the inconveniences mentioned above.

Another object of the invention to provide a less fragile watch and simpler design.

Another object of the invention is to provide a manufacturing method adapted to the specifics of this watch.

To do this, the invention provides a microgenerator in particular for wristwatch, comprising an oscillating mass, an annular element of pulses cooperating in rotation with the oscillating mass, a fixed support, mounted co-axially with the annular pulse member and provided with a plurality of piezoelectric blades extending radially from the fixed support to the annular pulse member, wherein the annular pulse member comprises a plurality of teeth arranged radially internally. in the annular element and adapted to cooperate with the free ends of the piezoelectric blades during the rotation of the annular element of pulses.

Such architecture provides a compact and reliable microgenerator, easily adaptable depending on the volume available and the power required.

The fixed support serves as an electrical interface between the piezoelectric blades and an electrical circuit for transforming the current received from all the piezoelectric blades for storage in a battery provided for this purpose.

This mode of transmission is simple and causes negligible losses.

The piezoelectric blades consist of cantilever beams, preferably covered with a piezoelectric layer. Such a piezoelectric film may comprise a PZT thin film (Pb (Zr, Ti) 03), a film comprising a material of the ferroelectric perovskite family, or a film comprising a non-ferroelectric piezoelectric material such as AlN or ZnO.

The ferroelectric thin film such as PZT can be polarized using an interdigitated electrode so as to increase the harvested electrical voltage. The non-ferroelectric piezoelectric films must be combined with a planar electrode disposed on each side of the piezoelectric film.

With these beams, the behavioral characteristics such as vibration and attenuation modes can be adjusted according to the needs and uses.

The oscillating mass comprises a radially outer portion in the shape of a circular arc extending over approximately 180 °. Advantageously, this radially outer portion concentrates the greater part of the oscillating mass.

This mode of concentration of the mass optimizes the dynamic performance of the oscillating mass, while having a simple, effective and reliable arrangement.

A central half-disc provides the connection between the radially outer portion and the axis "A" at the fixed support.

The half-disc may be hollowed out if necessary and / or occupy a smaller or larger angular surface.

The invention also provides a watch movement for quartz watch comprising an accumulator, for storing the received electrical energy, a microgenerator as above, electrically connected to the accumulator to recharge it, a micromotor , electrically connected to the microgenerator, a set of time indication, provided with a drive train rotated by the micromotor and cooperating with a plurality of needles indicating the time or an interval of time.

The invention also provides a watch, in particular a wristwatch, comprising a movement as previously described.

Such a watch has the advantages of precision, reliability and low cost inherent in quartz watches, and the advantages of an automatic watch, which does not need a battery change.

The invention finally provides a method of manufacturing piezoelectric blades of the microgenerator, comprising the steps of performing: the application of a SiO 2 layer by wet oxidation on a silicon wafer; sputtering application of a TiO 2 barrier layer; the application of a thin layer of piezoelectric; structuring an electrode structure; etching the piezoelectric layer with an aqueous solution of HF and HCl acid to define the blade; reactive ion etching of the barrier layer, SiO 2 and Si layer; and deep-ionization etching of the back of the SiO 2 layer and the SOI plate manipulator layer so as to define seismic mass and release the blade.

BRIEF DESCRIPTION OF THE FIGURES [0025] Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which: FIG. 1 illustrates, schematically and without limitation, a possible arrangement of internal organs of a watch according to the invention; fig. 2 illustrates an example of a piezoelectric generator comprising a plurality of piezoelectric blades, according to the invention;

Fig. 3 illustrates a plan view of a piezoelectric blade portion; and FIG. 4 illustrates the main steps of a method of manufacturing the piezoelectric blades according to the invention. Example (s) of Embodiment of the Invention [0026] FIG. 1 illustrates a watch according to the invention comprising, in a box 10, a movement 7 of quartz digital watch, an accumulator 6, and a rectifier 5. The electric energy useful for charging the accumulator is provided by a microgenerator , shown in more detail in plan view in FIG. 2. An oscillating mass 1, similar to that used on an automatic watch to reassemble, is rotatably mounted about an oscillation axis "A". In the example illustrated, the mass comprises a radially outer portion 11 in the shape of an arc extending approximately 180 °. The radially outer portion 11 may also extend over an angle smaller or greater than 180 °. A central half-disc 12 provides the connection between the radially outer portion 11 and the axis "A" at the fixed support 3.

The oscillating mass 1 carries an annular excitation element 2, mounted substantially co-axially, in the example shown, on the axis "A". In the example of FIG. 2, the annular element 2 has the shape of a complete ring. The annular element 2 may, however, form only a ring portion, for example, a circular arc subtending an angle smaller than 360 °. The annular element 2 is provided with a plurality of excitation teeth 8 distributed angularly in the radially inner zone of the annular element. According to the embodiments, the teeth are formed on the annular element itself or are reported thereon. In the example of FIG. 2, thirteen teeth are planned. This number varies (and may be lower or higher) depending on architectures, dimensions, number of piezoelectric blades, and electrical power required.

A plurality of piezoelectric plates 4 radiate from the fixed support 3 to the annular excitation element 2 of the microgenerator. The blades are distributed angularly around the support 3 on which they are fixed by a first end 9. In order to form cantilever beams, the second end 13 of the blades is free. This end is located near the teeth of the annular element, sufficiently close to the latter so that the rotation of the annular element 2 and teeth 8 can generate pulses on the free ends 13 of the blades. Due to the piezoelectric properties of the blades, the pulses enable the latter to generate electrical micro-currents transmitted by the connectors 14 to a rectifier 5. The sizing of the teeth 8 and the blades 4 is set up so as to enable the annular element 2 to rotate under the effect of the forces generated by the oscillating mass 1 subjected to the movements of the wearer of the watch. The blades 4 are sufficiently rigid to produce an oscillation frequency and a speed of attenuation sufficient on the one hand, without blocking the rotation of the annular element 2.

The rectifier 5, or electronic charger circuit, transforms the current from the generator into direct current suitable for charging a battery 6.

The accumulator 6 is for example a Li-ion battery, Li-Poly or NiMH, a supercapacitor or any other accumulator, depending on the desired architecture.

The movement 7 may be a quartz movement of known type.

In an advantageous embodiment, three elements of the watch, more particularly the generator module, the storage module 6 and the movement 7, are mechanically independent of each other and require only few electrical interconnections to ensure the operation of the watch. With this feature, the movement 7 and the generator module can be mounted in the box 1 independently and separately. The construction and design of the watch are thus simplified (compared to a conventional construction) thanks to these characteristics of separation between the generator module and the movement. The elements of the watch can thus be placed with great freedom; In this way, a rational and economical construction is achieved which makes the best use of the available volume.

It is also possible to use as a storage module a storage element occupying the housing provided for this purpose for the battery of the watch.

The generator module can be placed next to an existing movement in the case of the watch. The movement can be constituted by a known quartz electronic movement capable of functioning without the generator module, with, if necessary, an adaptation of the software. The only changes to this existing movement is to connect it electrically to the generator module to extend its reserve. You can also replace the battery with a rechargeable battery.

The watch may include input and control devices (not shown), for example a push button on the middle part, to allow the user control of the operation of the watch, the activation of various functions or the delivery on time, in a traditional way.

Other input devices (also not shown) may be provided and included within the scope of the present invention. As non-exhaustive examples of input devices such as buttons on the face, conventional type crowns, magnetic contacts or a touch screen.

According to another aspect of the invention, the state of charge of the battery can be converted into hours of operating autonomy, the latter being based, for example, on an average consumption forecast. Thus, it is possible to display numerically or graphically, the instantaneous power reserve of the watch or the autonomy of the watch in the absence of recharging by the generator module. Alternatively, one can also display (numerically or graphically) the charge of the battery as a percentage of a maximum charge.

So that the user can better appreciate the autonomy of the watch, the display of the generated and consumed powers can be useful. Preferably, the instantaneous powers, very variable, are not displayed, but rather displays an average power calculated on a suitable time base, a few hours for example.

FIG. 3 illustrates a plan view of a portion of one of the piezoelectric blades 4 having an interdigital electrode 19 and made from a silicon wafer and the method described below.

FIG. 4 (sub-Figs 4a to 4i) illustrates the main steps of the process for manufacturing piezoelectric blades 4 for a timepiece according to the invention. In particular, the piezoelectric blades 4 are formed of cantilever beams, preferably covered with a piezoelectric thin film 18 and having interdigital electrodes. Figures 4a to 4d and 4g, 4i show a view along the blade AB (see Fig. 3) while Figs. 4th 4f and 4h show a view across the CD blade (see Fig. 3) of said steps.

FIG. 4a shows the application of a Si0216 layer by wet oxidation on a silicon wafer 15 comprising a layer of Si 21; FIG. 4b illustrates the cathodic sputtering application of a TiO217 barrier layer; FIG. 4c shows the application of the piezoelectric thin film 18. The piezoelectric layer may comprise a PZT thin film (Pb (Zr, Ti) 03), a film comprising a material of the ferroelectric perovskite family, or a film comprising a non-ferroelectric piezoelectric material such as AIN or ZnO. The piezoelectric layer can be applied by sol-gel deposition; cathodic sputtering, laser pulsed laser deposition (PLD), chemical vapor deposition (CVD), or any other suitable method.

FIG. 4d shows the structuring of an interdigital electrode 19. The electrode 19, preferably platinum, can be structured using an evaporation step followed by a removal step (or lift-off), for example by etching, to remove a portion of the electrode and obtain the interdigitated geometry.

FIG. 4e shows the chemical etching of the piezoelectric layer 18 through a structured photoresist 22, using an aqueous solution of HF and HCl to define the blade 4; FIG. 4f shows the reactive ion etching of the barrier layer 17, the SiO 2 layer 16 and the Si layer 21.

Figures 4g and 4h illustrate the deep-ionization etching of the back of the Si0216 layer and the silicon plate 15 so as to define a seismic mass 23 and release the blade 4 thus formed.

FIG. 4i shows an alternative step to the steps of FIGS. 4b and 4d. In this embodiment, a first planar electrode 24 is structured on the SiO 2 layer 16 and a second planar electrode 25 is structured on the piezoelectric thin film 18. In this configuration, the planar electrodes 24, 25 are disposed on each of the faces of the piezoelectric layer 18. The first and second planar electrode 24, 25 is also preferably platinum. Still in this configuration, the piezoelectric thin film 18 preferably comprises a non-ferroelectric piezoelectric material such as AlN or ZnO.

Various variants of this method can be implemented without departing from the scope of the present invention.

Reference numbers used in the figures [0050] 1 oscillating mass 2 annular element of pulses 3 fixed support 4 piezoelectric blade 5 rectifier 6 accumulator 7 movement 8 teeth 9 fixed end of the piezoelectric blade 10 watch case 11 radially outer portion 12 half -central disk 13 free end of the piezoelectric blade 14 blade connector 15 silicon wafer 16 SiO 2 layer 17 TI02 barrier layer

18 thin layer of PZT 19 interdigitated Pt electrode 21 Si layer 22 structured photoresist 23 seismic mass 24 first planar electrode 25 second planar electrode A rotation axis of the oscillating mass

Claims (18)

claims Microgenerator, in particular for a wristwatch, comprising an oscillating mass (1), an annular element of pulses (2) cooperating in rotation with the oscillating mass (1), a fixed support (3), mounted co-axially with the annular pulse element (2) and provided with a plurality of piezoelectric blades (4) extending radially from the fixed support (3) to the annular pulse element (2), characterized in that the annular pulse element (2) comprises a plurality of teeth (8) arranged radially internally in the annular element and able to cooperate with the free ends of the piezoelectric blades (4) during the rotation of the annular element of the annular element. pulses (2). 2. Microgenerator according to claim 1, wherein the fixed support (3) is intended to serve as an electrical interface between the piezoelectric blades (4) and an electrical circuit for transforming the current received from all the blades (4). for storage in a battery (6) provided for this purpose. 3. Microgenerator according to claim 1 or 2, wherein the piezoelectric blades (4) consist of cantilever beams covered with a piezoelectric layer. 4. Microgenerator according to one of claims 1 to 3, comprising six piezoelectric blades (4). 5. Microgenerator according to one of claims 1 to 4, wherein the annular element of pulses (2) comprises thirteen teeth (8). 6. Microgenerator according to one of claims 1 to 5, wherein the oscillating mass comprises a radially outer portion (11) shaped circular arc extending over an angular range of substantially 180 °. 7. Microgenerator according to claim 6, wherein a central half-disc (12) provides the connection between the radially outer portion (11) and an oscillation axis (A) of the mass (1), at the fixed support (3). 8. Microgenerator according to one of claims 1 to 7, wherein the piezoelectric blades (4) comprise a piezoelectric layer (18) and an electrode structure (19, 25). The microgenerator of claim 8, wherein the electrode structure comprises an interdigitated electrode (19) on the piezoelectric layer (18). The microgenerator according to claim 8, wherein the electrode structure comprises a first planar electrode (24) and a second planar electrode (25), the planar electrodes (24, 25) are disposed on each of the faces of the piezoelectric layer. (18). 11. Watch movement for a quartz watch comprising an accumulator (6), for storing the received electrical energy, a microgenerator according to one of claims 1 to 10, electrically connected to the accumulator (6) in order to recharge the latter , a micromotor, electrically connected to the accumulator, a set of time indication, provided with a drive train rotated by the micromotor and cooperating with a plurality of needles indicating the time or a time interval. 12. Watch movement according to claim 11, further comprising a rectifier (5), electrically cooperating with the microgenerator and the accumulator (6), and for rectifying the current supplied by the microgenerator for storage in the accumulator (6). ). 13. Watch, in particular a wristwatch, comprising a movement according to one of claims 11 or 12. 14. A method of manufacturing piezoelectric blades (4) for a microgenerator according to one of claims 1 to 10, comprising the steps of: applying a layer of SiO2 (16) by wet oxidation on a silicon wafer (15). ) comprising an Si layer (21); sputtering application of a barrier layer (17); applying a piezoelectric layer (18); structuring an electrode structure (19, 25); etching the piezoelectric layer (18) with an aqueous solution of HF and HCl acid to define a blade (4); reactive ion etching of the barrier layer (17), the SiO 2 layer (16) and the Si layer (21); and deep-ionization etching of the back of the SiO 2 layer (16) and the silicon wafer (15) so as to define a seismic mass (23) and release the blade (4). The method of claim 14, wherein the barrier layer (17) comprises TiO2. The method according to claim 14 or 15, wherein the piezoelectric layer (18) comprises a PZT thin film, abbreviated to Pb (Zr, Ti) 03, a film comprising a material of the ferroelectric perovskite family, or a film comprising a non-ferroelectric piezoelectric material such as AIN or ZnO. The method of claim 16, wherein the piezoelectric thin film (18) comprises a non-ferroelectric piezoelectric material such as AIN or ZnO. 18. Method according to one of claims 14 to 17, wherein the application of the piezoelectric thin film is performed by sol-gel deposition, sputtering, laser ablation or chemical vapor deposition.