Patent Application
20180142749
The present invention relates to a spiral spring with at least one winding. The spiral spring consists of one solid core of a silicon material. The core comprises two long, parallel, and straight sides, and two short, parallel, and straight sides. The invention further relates to a method for the manufacturing of a spiral spring for mechanical clockworks. The invention similarly relates to a mechanical clockwork which has the inventive spiral spring installed.
Oscillation systems for mechanical clockworks, in particular for wrist watches, are referred to by experts as balance wheels. The balance wheel comprises an oscillation body, which can be rotated around an axis of rotation using a balance shaft. A spiral spring and balance spring are further provided, which, together with the mass of the oscillation body, form the rotatable and ticking system.
For the manufacturing of the spiral springs, tolerances cannot be ruled out. This is even more so the case for spiral springs made of silicon, which have a uniform coating of silicon oxide on their surfaces and exterior surfaces, in order to attain the necessary rigidity and/or temperature independence. As a rule, this coating is performed through thermal oxidation.
EP 1 422 436 A1 discloses a method for the manufacturing of spiral springs for the oscillation system of mechanical watches made of monocrystalline silicon. Here, the silicon core of the spiral spring is completely encased in silicon oxide.
The European patent application EP 2 284 628 A2 discloses a resonator (spiral spring), which is thermally compensated and possesses a core of monocrystalline silicon. In accordance with one embodiment, the thermal oxidation of the spiral springs is formed such that at least one exterior surface of the oscillation region of the core has a coating, and at least one other surface has no coating. In accordance with another embodiment, the oscillation region of the core has a coating on at least two adjacent exterior surfaces, where these coatings differ in their respective thickness.
The European patent application EP 2 589 568 A1 discloses a micro-mechanical part, which comprises a core of a semiconductor material and a coating of an electrically insulating material, such as diamond or silicon dioxide. The coating is formed on a surface of the core. The core features an inner layer and an outer layer, where the electrical conductivity of the outer layer is greater than that of the inner layer.
The Swiss patent application CH 699 780 A2 discloses a spring which consists of a silicon rod with an exterior surface. The silicon rod has a modulus of elasticity, and a thermal expansion coefficient. A material is provided, which partially compensates the thermal coefficient, where the material is Invar, Elinvar, Kovar, or silicon dioxide. The material is applied to the silicon rod in the form of a covering.
The international patent application WO 2011/7072960 A1 discloses a thermally compensated resonator. The body of the resonator has a core made of silicon material. The body of the core has at least a first and a second coating, which are selected such that the thermal expansion is essentially zero.
The U.S. Pat. No. 8,562,206 discloses a spiral spring. Each winding of the spiral spring has multiple openings that extend through the spirals of the spring.
The international patent application PCT/IB2015/054783 relates to a spiral spring and method for the manufacturing of a spiral spring. The spiral spring has a spiral spring mounting section, and a subsequent oscillation region, which possesses at least one winding. The core of the spiral spring is made of silicon. At least two long lateral surfaces of the core join at least two short lateral surfaces to one another. In at least one upper lateral surface, and along a winding of the oscillation region, at least one depression is formed in a second partial region in the SiO2 layer, whose depth extends at least to the core of the silicon.
The international patent application WO 2014/203086 A1 discloses an oscillation system for mechanical clockworks, a spiral spring, and a method for the manufacturing of a spiral spring. The spiral spring has a spiral spring mounting section, a subsequent oscillation region with at least one winding, and a stabilization region following the oscillation region. Before the thermal oxidation, a core of silicon possesses an essentially constant cross-section over the length of the oscillation region. After the thermal oxidation, the spiral spring features at least one first partial region with a first height, and at least one second partial region with a second height in the oscillation region. Here, the first height is greater than the second height.
The object of the invention is to provide a spiral spring that demonstrates a long-term excellent oscillation behavior, is free of warping in the plane of the spiral spring, and possesses stability against spring fractures. The spiral spring should also be reproducible in terms of its oscillation behavior, without neglecting the necessary temperature compensation.
A further object of the invention is to provide a method for the manufacturing of a spiral spring for mechanical clockworks, which can be performed simply and reliability, and results in a spiral spring with a long-term, excellent oscillation behavior, which also demonstrates the necessary temperature compensation, is free of warping in the plane of the spiral spring, and possesses stability against spring fractures.
A possible embodiment of the spiral spring is that at least one winding of the spiral spring comprises at least one winding, which consists of a solid core of a silicon material. The core has two long, parallel, straight sides, and two short, parallel, straight sides. In order to compensate the thermal expansion coefficient, at least the straight, long sides of the core that are opposite to one another are covered by a layer for the compensation of the thermal expansion coefficient. The layer is preferably a SiO2 layer.
A further embodiment for the spiral spring is that the upper short, straight sides, and the two opposing long sides are enclosed in a layer, preferably a SiO2 layer.
A further embodiment of the spiral spring is that it comprises at least one winding that consists of a solid core made of a silicon material. The core itself essentially comprises two long, parallel, straight sides, and two short, parallel, straight sides, among other things. The upper short, straight side is joined to the opposing long sides on both sides by an continuously differentiable upper section, respectively. The opposing long and straight sides, the continuously differentiable respective upper sections which join the upper short and straight sides to the opposing long and straight sides on both sides, and the upper short and straight sides are covered by a SiO2 layer.
The lower short, straight side is also joined to the opposing long, straight side on both sides by a continuously differentiable upper section, respectively. The core is covered by a SiO2 layer at least at the opposing long, straight sides, and at least partially at the respective, continuously differentiable upper section, and the respective, continuously differentiable lower section.
The spiral spring could be designed such that the two continuously differentiable upper sections differ from the continuously differentiable lower sections.
In accordance with a possible embodiment of the spiral spring, the short lower side and the short upper side have a SiO2 layer, such that the core is surrounded by a SiO2 layer. The thickness and/or form of the SiO2 layer differ at the lower short side and the upper short side. The thickness of the SiO2 layer can be between 2 μm and 5 μm.
The spiral spring itself comprises a spiral spring mounting section, a spiral spring end section, and at least one spiral spring ring section lying between them, which comprises the multiple windings of the spiral spring. The spiral spring can be installed in a mechanical watch.
The core of the spiral spring can consist of amorphous silicon, partially amorphous silicon, polysilicon, a monocrystalline silicon structure, or a silicon sintering material. The spiral spring preferably consists of a polycrystalline silicon material. The polycrystalline silicon material can be produced in various ways. A chemical vapor deposition (CVD) or an epitaxy deposition of the polycrystalline silicon may occur, for example, in that the resulting starting material forms a thin layer or a wafer, whose thickness is equal or essentially equal to the thickness corresponding to the height of the spiral springs to be manufactured. A CVD is also conceivable for the production of polycristalline silicon. In doing so, initial wafers or thin layers are obtained, from which the spiral springs can be manufactured. Similarly, polycristalline silicon can be obtained through sublimation with the Physical Vapor Transport (PVT) method. The polycristalline silicon is formed through sublimation of silicon, or silicon carbide on the barrier layer, with the thickness that is equal, or essentially equal to the thickness that the spiral spring to be manufactured should have. A casting of polycrystalline silicon is also possible. A further possibility for the production of polycrystalline silicon is the Siemens process. Wafers are cut and, if needed, the required thickness is lapped from the silicon hereby produced, the thickness being essentially equal in height to the spiral springs to be manufactured.
The inventive method for the manufacturing of a spiral spring from a silicon material is designed through the following steps, in accordance with a possible embodiment: provision of a support, where the support can have the form of a wafer; application of a silicon material to the support, where the silicon material forms a core of at least one winding of the spiral spring; etching of the at least one winding of the spiral spring, such that the core of the at least one winding of the spiral spring is formed, comprising two long, parallel, straight sides and two short, parallel, straight sides; performance of a thermal oxidation, where a layer of an oxide grows at least on the lateral surfaces of the spiral spring defined, and exposed by the long sides; and removal of the support from the silicon material.
In accordance with a possible embodiment of the method, during the performance of the thermal oxidation, the layer of the oxide grows on the lateral surfaces, defined and exposed by the long sides, and on the lateral surfaces of the spiral spring, defined and exposed by the upper, short, straight sides.
In a possible embodiment of the etching process of the at least one winding of the spiral spring, the core of the at least one winding of the spiral spring is formed. Two long, parallel, straight sides, and two short, parallel, straight sides are hereby created. The upper short, straight side is joined to the opposing long sides on both sides by a continuously differentiable upper section, respectively.
In a further embodiment of the etching process of the at least one winding of the spiral spring, the core of the at least one winding of the spiral spring is formed. Two long, parallel, straight sides, and two short, parallel, straight sides are hereby created. The upper short, straight side is joined to the opposing long sides on both sides by a continuously differentiable upper section, respectively. Similarly, a lower short, straight side is joined to the opposing long sides on both sides by a continuously differentiable lower section, respectively.
In order to form the continuously differentiable lower section, the etching of the at least one winding of the spiral spring is performed, such that a rear etching is formed in the region of the lower side of the core. The rear etching is formed such that at least the continuously differentiable lower section which joins the opposing long sides with the lower short and straight sides on both sides, respectively, is spaced apart from the support.
A further embodiment of the etching process is that a separating layer is provided between the support and the silicon material for the core of the at least one winding of the spiral spring. The etching of the at least one winding of the spiral spring is performed such that in the region of the lower, short, straight side of the core, a rear etching is formed at least in the separating layer. Through the rear etching, at least the continuously differentiable lower section which joins the opposing long sides with the lower short and straight sides on both sides, respectively, is spaced apart from the support. Further, the parameters of the etching process can be adjusted such that etching is performed below an original level of the support. This means that material of the support is eroded in certain regions.
Subsequent to the etching process, a layer of a material for the compensation of the thermal expansion coefficient of the silicon material of the core of the windings is applied to the boundary surfaces—exposed by the etching process—of the at least one winding. The material for the compensation of the thermal expansion coefficient is preferably the same material as that of the separating layer. In accordance with an especially preferred embodiment, the material of the layer for the compensation of the thermal expansion coefficient of the silicon material is a SiO2 layer. The SiO2 layer is formed by way of thermal oxidation of the silicon material of the core. Finally, the removal of the support takes place, which can be performed mechanically and/or chemically.
The “active oscillation region” of the spiral spring extends from the inner end of the active oscillation region, which adjoins to the spiral spring mounting section of the spiral spring, to the outer spring holding point and spiral spring end section.
A further embodiment of the invention relates to a spiral spring with a spiral spring mounting section, a spiral spring end section, and at least one spiral spring ring section lying between them, which possesses at least one winding. As a rule, the spiral spring ring section has multiple windings. The spiral spring has a solid and polygonal core, made of silicon material with at least two long sides, and at least two short sides. Two opposing long sides, together with an upper short side, are coated in a SiO2 layer. At the respective transition points from the upper, short side to the long sides, the core has an upper round, and a continuously differentiable upper section. Further, at the respective transition points from the lower, short side to the long sides, the core has a lower round, and a continuously differentiable lower section. The upper round and lower round are similarly coated with the SiO2 layer.
The inventive spiral spring has the advantage that it possesses the mechanical stability required for a smooth oscillation behavior, the necessary temperature compensation, and absence of warping. Additionally, the inventive spiral spring, which has a reduced weight, also protects the bearings of the spiral spring, which has a positive effect on the accuracy of the watch, and an extension of the service intervals.
As a rule, the core of the spiral spring is rectangular, and thus possesses two long sides and two short sides, which at least form over the length of the oscillation region two long lateral surfaces through two long sides, and two short lateral surfaces through two short sides. The core thus has two opposing long lateral surfaces, and two opposing short lateral surfaces.
The rounds that are formed (continuously differentiable sections of the core) differ, for example, in the radii of the upper round and the radii of the lower round. It is the rounds on the corners of the core that prevent mechanical voltage peaks, which, in turn, reduces the risk of fracture of the spiral spring.
In accordance with a possible embodiment, the spiral spring can also have a SiO2 layer on the lower short side. The SiO2 layer on the lower side can have a lesser thickness than the SiO2 layer on the upper short side, or on both long, parallel sides. In this embodiment, the SiO2 layer is applied to the lower short side in a second step of thermal oxidation. The duration of the thermal oxidation of the lower short side is selected such that a SiO2 layer grows with a lesser thickness than the thickness of the SiO2 layer, on both lateral surfaces and the upper surfaces. The thickness of the SiO2 layer on the lower lateral surface formed by the lower short side is less than 2,000 nm. The preferred thickness is in the range of 750 mn to 500 nm. The core of the spiral spring is preferably made of polysilicon.
During the thermal oxidation of the core, upper rounds form at the respective transition points from the upper short side to the long sides, and lower rounds form at the respective transition points from the lower short side to the long sides.
In accordance with an embodiment of the method, a separating layer may be applied to the support, before the application of the material forming the core of the spiral spring on the support. Similarly, the material for the core of the spiral spring may have a separating layer. The wafer with the material for the windings of the spiral spring, and the separating layer are, for example, bonded to the support.
The spiral springs produced and exposed during the etching process are still connected to the material layer. The material layer with the spiral springs can be at least partially removed from the support, or from the support with the separating layer, through mechanical and/or chemical methods. In accordance with a possible embodiment, the support, or the support and the separating layer, can be removed in a region that is smaller than the diameter of the support. This has the advantage that sufficient material for manipulation is still available on the margin for the manipulation.
It is also possible that before the at least partial removal of the support, the separating layer, which is preferably also a SiO2 layer, is eroded in the free regions through an etching process. After the subsequent removal of the support, exposed cores of the spiral springs are obtained, which have the separating layer of SiO2 on the lower side.
After the support, or the support and the separating layer, have been removed, the further thermal oxidation can performed at the upper short side, and the opposing lower short side, provided it has no coating. The duration of the thermal oxidation is measured such that the thickness of the oxide layer applied (approximately 2,000 nm) is smaller than the thickness of the oxide layer on the lateral surfaces and the upper lateral surfaces of the spiral spring. The duration of the thermal oxidation is preferably less than 1.5 hours, and the especially preferred duration of the thermal oxidation is less than 1 hour.
These and other objects, features, and advantages of the present disclosure will become readily apparent upon a review of the following detailed description of the disclosure, in view of the drawings and appended claims.
Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements. It is to be understood that the claims are not limited to the disclosed aspects.
Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the example embodiments.
It should be appreciated that the term “substantially” is synonymous with terms such as “nearly,” “very nearly,” “about,” “approximately,” “around,” “bordering on,” “close to,” “essentially,” “in the neighborhood of,” “in the vicinity of,” etc., and such terms may be used interchangeably as appearing in the specification and claims. It should be appreciated that the term “proximate” is synonymous with terms such as “nearby,” “close,” “adjacent,” “neighboring,” “immediate,” “adjoining,” etc., and such terms may be used interchangeably as appearing in the specification and claims. The term “approximately” is intended to mean values within ten percent of the specified value.
In order to better understand the present invention and the technical environment in which the invention is used, an oscillation system for mechanical clockworks, which is known from the state of the art will be described in conjunction with
Oscillation system 1 comprises an oscillation body in the form of fly wheel 2, balance shaft 3, and spiral spring 4. Fly wheel 2 consists of outer annular ring section 2.1, which is joined with nave section 2.3 through several spokes 2.2. Nave section 2.3 features a central through-hole deviating from the annular form, in which allocated shaft section 3′ of balance shaft 3 is received, whose concentric exterior creates a tight fit with nave section 2.3 of fly wheel 2. Fly wheel 2 is thus connected to balance shaft 3 in a torque-proof manner. Further, several fly wheel masses 2.4 are attached to the interior of outer annular ring section 2.1, the interior facing the center of rotation of fly wheel 2.
Balance shaft 3 further features upper and lower free end 3.1, 3.2 which taper off, and are received in the correspondingly formed upper and lower bearing units for rotatable bearing of balance shaft 3 by axis UA.
Spiral spring 4 consists of a preferably ring-shaped, inner spiral spring mounting section 4.1 and outer spiral spring end section 4.2. In between these, there are several spiral spring ring sections 4.3, which run in a plane that is vertical and preferably concentric to the axis of spiral spring 4, which corresponds with axis UA of balance shaft 3.
The preferably ring-shaped inner spiral spring mounting section 4.1 is connected to balance shaft 3 in a torque-proof manner, preferably with adhesive and/or using tight fit. For this purpose, balance shaft 3 features shaft section 3″ which is formed for the reception of inner spiral spring mounting section 4.1, which is arranged above shaft section 3′ which receives fly wheel 2.
In order to provide the mounting of outer spiral spring end section 4.2, which is torque-proof with respect to balance shaft 3, holding arrangement 5 is provided for adjusting the center of spiral spring 4. Holding arrangement 5 comprises at least holding arm 6, and holding element 7, which is attached in a slidable manner in the region of the outer free end of holding arm 6 along longitudinal axis LHA of holding arm 6.
Holding arm 6 features inner holding arm end 6.1, and outer holding arm end 6.2, where inner holding arm end 6.1 forms an open annular ring, and longitudinal guide groove 6.3 is provided in the region of outer holding arm end 6.2. Longitudinal guide groove 6.3 is provided for the variable mounting of holding element 7 on holding arm 6. Inner holding arm end 6.1 is attached in a torque-proof manner by way of a holding method, which will not be described in further detail, and which can also receive the upper and lower bearing units for the rotatable bearing of balance shaft 3, such that the open annular ring of inner holding arm 6.1 concentrically surrounds axis UA of balance shaft 3.
Holding element 7 features an essentially cylindrical, longitudinal base body 7.1, with upper and lower front face 7.11, 7.12, and longitudinal axis LHE, which features blind borehole 7.2 that is opened towards upper front face 7.11, and has an inner threading for receiving screw 8. Using screw 8, which is guided through longitudinal guide groove 6.3 of holding arm 6, holding element 7 can be screwed tight to holding arm 6, such that :longitudinal axis LHA of holding arm 6 and longitudinal axis LHE of holding element 7 run vertically to one another.
On opposing lower front face 7.12 of base body 7.1 of holding element 7, guide groove 7.3 extending vertically to longitudinal axis LHE of base body 7.1, and opening downwards, is provided, which is formed for the radially guiding reception of outer spiral spring end section 4.2. A plane receiving longitudinal axis LHE of base body 7.1 divides guide groove 7.3 into approximately two opposing, equal halves of the fork-like lower free end of holding element 7.
In the mounted state, by way of holding arrangement 5, radial distance A between axis UA of balance shaft 3, and longitudinal axis LHE of holding element 7, and thus outer spiral spring end section 4.2, are adjustable. Through a corresponding radial sliding of holding element 7, and thus of outer spiral spring end section 4.2, towards axis UA, the spiral spring center is adjustable, and preferably such that spiral spring ring sections 4.3 have the same distance from one another and run concentrically around axis UA.
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Similarly, in this embodiment, no material preventing the thermal oxidation is applied to the layer made of silicon material 32 for the spiral spring. After the etching and exposure of windings 9 for spiral springs 4, there occurs a first step of the thermal oxidation. Here, the layer made of silicon material 32, which surrounds spiral springs 4, is still connected to support 30. In the first step of the thermal oxidation, SiO2 layer 20 grows on the lateral surfaces defined by long and straight sides 22 (not shown here) and on the upper lateral surface of core 16 of the spiral spring defined by the upper, short, and straight side 24O. After the first step of the thermal oxidation, support 30 and here, too, separating layer 31, are mechanically and/or chemically eroded. A mechanical erosion can occur, for example, through grinding.
After the removal of support 30 the lower lateral surface of core 16 of spiral spring 4 defined by the lower, short, and straight side 24U is thus exposed. In a second step of the thermal oxidation, in one embodiment of the method, SiO2 layer 20 can also be applied to the lower lateral surface of core 16 of spiral spring 4. It is possible that SiO2 layer 20 on the lower lateral surface of core 16 possesses a lesser thickness than SiO2 layer 20 on the remaining lateral surfaces of core 16 of windings 9 of spiral spring 4.
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Windings 9 of spiral spring 4 formed out of silicon material 32 (see
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The manufacturing methods described here have the advantage that the spiral springs can be manufactured from silicon material (e.g. polycrystalline silicon) without warping. Further, the spiral springs manufactured in this way demonstrate a long-term excellent oscillation behavior and possess stability and resistance to spring fractures. The spiral spring is also reproducible in terms of its oscillation behavior, without neglecting the necessary temperature compensation.
It will be appreciated that various aspects of the disclosure above and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015110796.1 | Jul 2015 | DE | national |
| 102015111359.7 | Jul 2015 | DE | national |
| 102015111605.7 | Jul 2015 | DE | national |
| 102015112897.7 | Aug 2015 | DE | national |
The present application is filed under 35 U.S.C. §§ 111(a) and 365(c) as a continuation of International Patent Application No. PCT/IB2016/053970, filed on Jul. 1, 2016, which application claims priority from German Patent Application No. DE 10 2015 110 796.1, filed on Jul. 3, 2015, German Patent Application No. DE 10 2015 111 359.7, filed on Jul. 14, 2015, German Patent Application No. DE 10 2015 111 605.7, filed on Jul. 17, 2015, and German Patent Application No. DE 10 2015 112 897.7, filed Aug. 5, 2015, which applications are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IB2016/053970 | Jul 2016 | US |
| Child | 15860824 | US |
