Classifications

• • 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
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/004—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor characterised by the material used
  • G04B31/008—Jewel bearings
  • G04B31/0087—Jewel bearings with jewel hole only
• • 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
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/004—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor characterised by the material used
  • G04B31/012—Metallic bearings
  • G04B31/0126—Metallic step-bearings
• • 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
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/08—Lubrication

Definitions

• the present invention relates to a micromechanical bearing in which is pivotable an axis, the axis comprising at least one end a span via which the axis is in contact with a surface facing the bearing, said bearing being extended by a pivot engaged in a hole in the bearing.
• a bearing is particularly used in the field of watchmaking.
• the wheel To drive a wheel in rotation in a clockwork movement, it is known to fix the wheel on an axis comprising at least one of its ends a range extended by a pivot.
• the axis is positioned between two bearings each comprising a hole in which is housed a pivot axis. According to the chosen construction method, the range of one end of the axis or the range of each end of the axis comes into contact with a surface facing the associated bearing. Both bearings guide the axis in rotation while prohibiting its axial translation.
• the oil layer between the axis reach and the surface opposite the bearing is particularly fine so that there is a bonding effect between the axis of the bearing and the surface facing the bearing and, when the axis rotates, a shearing force of the oil layer comes oppose the rotation of the axis.
• the present invention aims at improving the known technique, by proposing a solution for reducing the shearing force at the level of the oil layer present between the bearing of an axis and the surface opposite a bearing in which the axis is rotated.
• the present invention relates to a micromechanical bearing in which an axis pivots, the axis comprising at one end a bearing surface via which the axis is in contact with a surface facing the bearing, said bearing being extended by a pivot engaged in a hole in the bearing, the bearing surface facing the axis of the bearing comprising at least one recess to reduce the contact area between the bearing axis and the bearing.
• the recess is in the form of a ring centered on the bearing hole.
• the effect ie the torque produced by the elementary shear force, is the product of this shearing force by the distance between the axis of rotation and the point of application of the elementary force.
• the surface facing the bearing by which the bearing surface of the shaft is in contact with the bearing is provided with a plurality of recesses distributed around the bearing hole. The reduction of the effect of the shearing force is thus more homogeneous between the bearing of the axis and the surface of the bearing opposite the span of the axis.
• FIG. 1 is a view of a wheel of a watch movement rotatably mounted between two bearings according to the invention
• FIG. 2 is a view from above of a bearing according to the invention.
• FIG. 3 is a top view of another bearing according to the invention.
• the present invention proceeds from the general inventive idea of limiting the contact surface between the range of an axis and the surface facing a bearing maintaining said axis.
• the invention proposes a new bearing whose general shape limits said contact surface.
• Figure 1 shows schematically the implementation of bearings according to the invention for driving in rotation of a toothed wheel of a watch movement.
• the toothed wheel 20 is fixed on an axis 30 comprising at each end a bearing 31a, 31b extended by a pivot 32a, 32b.
• the axis 30 is rotatably mounted between two bearings 10a, 10b according to the invention.
• the bearings 10a, 10b preferably of annular shape, are immobilized in a frame 21.
• These bearings 10a, 10b comprise, in known manner, a hole 1 1, preferably centered, which passes right through them. Note that the wall of the hole 1 1 may include an olivage to minimize contact with the pivots 32a, 32b and facilitate possible lubrication.
• a pivot 32a, 32b of the axis 30 guided in rotation by the corresponding bearing 10a or 10b is housed in the hole 1 1.
• the span 31a, 31b of the axis 30 comes into contact with a surface 12 facing the bearing 10a, 10b, so that the axis 30 is immobilized in axial translation, with a clearance, between the bearings 10a, 10b.
• the hole 1 1 opens into a recess 13 of preferentially conical shape.
• This hollow 13, commonly called oiler in the field of watchmaking, may be intended to receive a drop of oil.
• the other end of the hole 1 1 is slightly flared to facilitate the infiltration of the oil between the bearing 10a, 10b and the range 31a, 31b at the contact surface 12. It will be understood that this recess is optional and that it will be provided only in the case where it is desired to lubricate the pivoting of the axis 30 in the bearing 10a, 10b.
• a bearing 10a, 10b according to the invention is characterized by a recess 14 for reducing the contact surface 12 between the bearing 31a, 31b of the axis 30 and the bearing 10a, 10b.
• the recess 14 is made on the opposite side to the recess 13, in the contact surface 12 of the bearing 10a, 10b which is opposite the bearing surface 31a, 31b of the axis 30.
• the recess 14 has an annular shape.
• the residual contact surface 12 between the bearing surface 31a, 31b of the axis 30 and the bearing 10a, 10b thus has the shape of two concentric inner 12a and outer 12b rings.
• the inner radius R0 of the inner ring 12a is substantially equal to the radius of the hole 1 1, while the outer radius R1 of the inner ring 12a is equal to the inner radius of the recess 14.
• the outer concentric ring 12b it is between an inner radius R2 equal to the outer diameter of the recess 14, and an outer radius R3.
• the diameter R1 must be sufficient to ensure proper maintenance of the axis 30 in the hole 1 1.
• a plurality of recesses 14 are hollowed on the surface of the bearing 10a, 10b around the hole 1 1.
• six recesses 14 are regularly spaced, arranged concentrically around the pivot 32a, 32b of the axis 30 and opening into the flared end of the hole 1 1.
• the dimensions of the bearings are small, from less than 1 mm to a few millimeters for the largest dimension.
• the production of a bearing according to the invention is therefore delicate and requires specific tools.
• the bearing 10a, 10b is made of a monocrystalline hard material such as ruby, corundum, spinel or else cubic zirconia and the recesses 14 are machined by ablation of material by means of a laser beam, by electroerosion or by grinding.
• the bearing 10a, 10b is made of a hard sintered material such as corundum, ruby, ceramics, alumina, zirconia or even a hard metal and the recesses 14 are made by stamping or machined by ablation. This technique is described in particular in document EP 2 778 801 A1 in the name of the Applicant.
• the process includes a first step for forming a ceramic precursor from a ceramic-based powder taken in a binder.
• This ceramic-based powder may comprise at least one metal oxide, a metal nitride or a metal carbide.
• the ceramic-based powder may comprise aluminum oxide in order to form synthetic sapphire or a mixture of aluminum oxide and chromium oxide to form synthetic ruby.
• the binder it can be of the polymer type or of the organic type.
• the method comprises a second step intended to compress, with the aid of an upper die and a lower die which is brought closer to one another, the ceramic precursor to form a green body of the future bearing. 10a, 10b with upper and lower surfaces respectively comprising at least one recess 14 and, where appropriate, a recess 13. It is therefore understood that each green body thus formed already comprises the blanks of the recess 14 and the recess 13.
• each substantially planar matrix comprises at least one punch intended to form the recess 14 and, optionally, the recess 13.
• the upper die comprises a punch with a substantially annular surface for forming the recess 14
• the lower die comprises a punch with a substantially conical surface for forming the recess 13.
• the green body is sintered to form a ceramic bearing 10a, 10b and bore hole 11 to connect the upper surface and the lower surface of the bearing 10a, 10b.
• This step is preferably carried out using destructive radiation of the laser type in order to obtain a very precise etching. However, this step can be performed for example by mechanical drilling or etching with high pressure water.
• the present invention is not limited to the embodiments which have just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the appended claims. It will be noted in particular that in its basic embodiment, the present invention applies to the case in which only one of the two bearings 10a, 10b which guide the axis 30 is provided in its contact surface. 12 with the bearing 31a or 31b of the pivot 32a or 32b corresponding to a recess 14 according to the invention. The case in which the two bearings 10a, 10b each have a recess 14 for reducing the extent of the contact surface 12 with the bearing surfaces 31a and 31b of the pivots 32a and 32b is of course also considered.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Sliding-Contact Bearings (AREA)
• Braking Arrangements (AREA)
• Storage Of Web-Like Or Filamentary Materials (AREA)
• Mounting Of Bearings Or Others (AREA)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

Country Status (7)

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Family Cites Families (27)

• 2017
  • 2017-11-15 KR KR1020197012887A patent/KR102234880B1/ko active IP Right Grant
  • 2017-11-15 EP EP17808805.0A patent/EP3519902B1/de active Active
  • 2017-11-15 CN CN201780079616.4A patent/CN110114731B/zh active Active
  • 2017-11-15 US US16/344,237 patent/US11036186B2/en active Active
  • 2017-11-15 WO PCT/EP2017/079302 patent/WO2018114149A1/fr unknown
  • 2017-11-15 JP JP2019524233A patent/JP6901558B2/ja active Active
  • 2017-11-27 TW TW106141127A patent/TWI786075B/zh active

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