This application claims priority from European Patent Application No. 13171268.9 filed Jun. 10, 2013, the entire disclosure of which is incorporated herein by reference.
The present invention concerns the field of electronic timepiece movements which include a motor for a timepiece.
There is known, particularly from EP Patent No 0848480, a single-phase motor whose stator is directly formed in a base plate or a main plate made of magnetic material (
However, the aforementioned timepiece movement raises a significant problem. It is difficult to machine the isthmuses separating the two stator poles at the periphery of the rotor hole with the conventional machining techniques used for plates or bridges of a timepiece movement. The isthmuses must be thin to ensure magnetic saturation between the two stator poles. Thus, low tolerance machining must be used to create isthmuses of very small width (in the central part thereof). In a conventional timepiece motor, these isthmuses are obtained by stamping. Stamping isthmuses in a main plate is not without problems and increases the production costs of the plates. Further, the plate has portions, formed by the inner poles located inside apertures, which are fragile and which can easily be bent or broken. A plate generally has to undergo several machining operations and treatments; which involve various manipulations, during which the inner poles risk being damaged. It will be noted that any problem in machining the isthmuses or any inner pole damaged during a manipulation will result in the plate becoming unusable. Plates are expensive. Thus, even for an average industrial yield, the financial loss is high.
It is an object of the present invention to overcome the drawbacks of the aforementioned prior art.
To this end, the present invention concerns an electronic timepiece movement provided with at least one motor including a stator and a rotor with a permanent magnet arranged in a stator hole, said stator defining at least two magnetic poles respectively including at least two pole shoes extending at the periphery of the hole. The pole shoes are connected to each other by at least one continuous isthmus. The motor further includes at least one coil respectively mounted around at least one core. The pole shoes and the core form together a first part made of ferromagnetic material, said first part being formed by or including a single-piece wafer forming both the pole shoes and the core. An end portion of each coil core is connected to a least one corresponding pole shoe by a second portion, defining a base plate or a main plate made of magnetic material, to which the first part is secured and on which the elements of the electronic timepiece movement are at least partially mounted.
Other particular features of the invention will be set out below in the detailed description of the invention.
The invention will be described below with reference to the annexed drawings, given by way of non-limiting example, and in which:
“Stator pole” means a portion of the stator, outside the coil core(s), which conveys a magnetic field generated by any one of the coils from one end of the core carrying said coil to a pole shoe which extends over an angular sector at the periphery of the hole for the permanent rotor magnet. A stator pole is thus associated here with a single pole shoe. The magnetic field may be a re-entrant or exiting field relative to said hole depending upon the polarity of the supply current of the coil. It will be noted that within the explanation of the present invention, the coil core(s) are not considered as being distinct element(s) relative to the stator, but as part of the stator.
In the first embodiment of
According to the invention, the first part 8 of the stator is formed by or includes a single-piece wafer forming both the two pole shoes and the core. In a variant embodiment, first part 8 is laminated; it then includes a stack of wafers, including at least one single-piece wafer, this latter wafer defining a rotor hole with a closed edge. It will be noted that aperture 36 in base plate or main plate 10 has a simple shape, for example rectangular. None of the areas of the base plate or main plate is made fragile by the incorporation of the motor in the timepiece movement by using the base plate or main plate to partially form a stator pole. Indeed, the isthmuses 20 and 22 are arranged in the first part 8 of the stator, said first part being secured to the base plate or main plate when the timepiece movement is assembled. Thus, the base plate or main plate is manufactured, at least in a preliminary step, separately from first part 8. This first part may be obtained in a conventional manner by stamping; which allows for easy control of the formation of the isthmuses and also of the positioning cells at the periphery of hole 24. The machining of aperture 36 does not cause any problems and can easily be performed during the ordinary manufacture of a timepiece main plate. Further, the two end portions 30 and 32 of first part 8 may be secured to rigid areas of the base plate or main plate.
In the variant shown in
Main plate 10A forms the main plate of electronic timepiece movement 40. Rotor 6 is coupled to a gear train 44 formed of several wheel sets whose arbors rotate in respective bearings arranged in main plate 10A. This main plate also carries various components of electronic circuit 46, which includes a printed circuit board (PCB) 48 with electrical paths and, in particular, two contact pads to which the two ends of coil 28A are electrically connected.
Number | Date | Country | Kind |
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13171268 | Jun 2013 | EP | regional |
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4249251 | Wuthrich | Feb 1981 | A |
4369385 | Malkin et al. | Jan 1983 | A |
4376996 | Wuthrich | Mar 1983 | A |
4382695 | Rinaldi et al. | May 1983 | A |
4392748 | Yoshino | Jul 1983 | A |
4725749 | Wuthrich | Feb 1988 | A |
4912832 | Egger et al. | Apr 1990 | A |
5059840 | Plancon | Oct 1991 | A |
5172349 | Triponez et al. | Dec 1992 | A |
6437466 | Taghezout | Aug 2002 | B1 |
Number | Date | Country |
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0 847 130 | Jun 1998 | EP |
0 848 480 | Jun 1998 | EP |
1 544 693 | Jun 2005 | EP |
2 532 444 | Mar 1984 | FR |
Entry |
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European Search Report issued Mar. 14, 2014, in European Application No. 13171268 filed Jun. 10, 2013 (with English Translation). |
Number | Date | Country | |
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20140362671 A1 | Dec 2014 | US |