Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F7/00—Magnets
  • H01F7/06—Electromagnets; Actuators including electromagnets
  • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
  • H01F7/081—Magnetic constructions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F7/00—Magnets
  • H01F7/06—Electromagnets; Actuators including electromagnets
  • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
  • H01F7/18—Circuit arrangements for obtaining desired operating characteristics, e.g. for slow operation, for sequential energisation of windings, for high-speed energisation of windings
  • H01F7/1872—Bistable or bidirectional current devices
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
  • H01H2001/0042—Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H50/00—Details of electromagnetic relays
  • H01H50/005—Details of electromagnetic relays using micromechanics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H51/00—Electromagnetic relays
  • H01H51/22—Polarised relays

Definitions

• the present invention relates to a bistable magnetic actuator and in particular a microactuator.
• microrelays electrical or optical
• microvalves microvalves
• micropumps etc.
• FIG. 1 Document WO 97/39468 describes a magnetic actuator which can take the form illustrated in FIG. 1 attached. As shown, this actuator comprises a magnetic circuit consisting of a central pole piece 12 surrounded by a conductive coil 14 and two symmetrical pole pieces 16. A movable magnetic piece 18 is arranged opposite the central pole piece 12.
• Such an actuator is unidirectional in the sense that the force F exerted on the moving part can only be directed in one direction.
• This actuator is therefore not bistable, but monostable, the only stable working position being that in which the moving part 18 is pressed against the contact 19.
• Bistable magnetic actuators are known, however.
• the article by M. Se. H. Ren et al. entitled “A Bistable Microfabricated Magnetic Cantilever Microactuator with Permanent Magnet” published in the Proceedings of the 5th International Conference Microsystem Technologies 96, Potsdam, September 17-19, 1996, pages 799 to 801 describes an actuator shown in Figure 2 attached.
• This actuator comprises a permanent magnet 20 extended by two magnetic branches 22, 24 each surrounded by a conductive winding, respectively 23, 25.
• the magnetic flux present in each of these air gaps results from the sum of the fluxes due to the permanent magnet 20 and to the currents possibly circulating in one or the other of the windings 23 and 25.
• the magnetic forces FI and F2 applied to the end of the beam 26 are exerted either in one direction or in the other depending on whether one or the other of the conductive windings 23, 25 is traversed by a current.
• Such an actuator is therefore bidirectional or, if you like, bistable.
• This bistable actuator has a drawback. Indeed, as the moving part 26 is an integral part of the magnetic circuit, its movement is limited. Furthermore, its mobility is reduced because it results from a bending of a magnetic part. The object of the present invention is precisely to remedy this drawback.
• the invention provides a bistable actuator in which the displacement of the moving part is increased and its mobility improved. This object is achieved by the fact that the moving part is fixed to flexible means which are no longer part of the magnetic circuit.
• the invention relates to a bistable magnetic actuator comprising:
• a first fixed magnetic structure comprising a first conductive winding surrounding a first open magnetic circuit having a first end and a second end,
• a second fixed magnetic structure comprising a second conductive winding surrounding a second open magnetic circuit having a first end and a second end, the first ends of the first and second magnetic circuits being arranged opposite one another,
• a moving magnetic part which can occupy a first or a second stable working position depending on whether the first or the second conductive winding is excited, - for each magnetic circuit, the first end and the second end have faces located in planes perpendicular to each other, and the second ends of the first and second magnetic circuits have faces arranged in the same plane or are combined, characterized in that :
• the mobile magnetic part is located in the vicinity of the first end of the first magnetic circuit and of the first end of the second magnetic circuit,
• the moving magnetic part is fixed to non-magnetic means allowing the moving part to move in the direction of the first end of the first magnetic circuit or in the direction of the first end of the second magnetic circuit.
• the conductive windings and the magnetic circuits can be produced according to techniques borrowed from microelectronics.
• the actuator is then a micoactuator.
• the windings can be made up of plies of conductive tapes deposited in engraved boxes.
• the magnetic circuit can be produced using layers of "soft” or “hard” magnetic materials or hysteresis materials.
• Soft materials magnetize linearly depending on the magnetic field applied to them (iron, nickel, iron-nickel, iron-cobalt, iron-silicon, ).
• Hard materials have a fixed magnetization which does not depend on the applied field (ferrite, samarium-cobalt, neodymium-iron-boron, platinum-cobalt).
• Hysteresis materials have properties between those of soft materials and those of hard materials. They can magnetize and keep a magnetization after the excitation field has disappeared.
• the two magnetic structures can take various forms, and for example be symmetrical with respect to a plane or with respect to a point.
• the movement of the moving part can be a translation (or a quasi-translation) or a rotation.
• a translation or a quasi-translation
• a rotation or a rotation.
• FIG. 3 illustrates a particular embodiment of a bistable microactuator according to the invention
• FIG. 4A to 41 show different steps of a method of producing a microactuator according to one invention
• FIG. 5 illustrates an application to the production of a microrelay
• FIG. 8 illustrates a microactuator with an axis of rotation.
• the embodiment illustrated in Figure 3 corresponds to a device having a plane of symmetry.
• the first magnetic structure comprises a first conductive winding 32 ⁇ surrounding a first open magnetic circuit comprising a circular part 34 x and a straight part 30 located in the plane of symmetry.
• the second structure comprises, in the same way, a second conductive coil 32 2 surrounding a second open magnetic circuit comprising a circular part 34 2 and the straight part 30 already mentioned, which therefore happens to be common to the two structures.
• the first magnetic structure has a first end 35 ⁇ with a face perpendicular to the plane of the figure
• the second magnetic structure has a first end 35 2 with a face perpendicular to the plane of the figure.
• These two structures have second ends which, in the example illustrated, coincide with the end 35 ′ of the straight part 30. The face of this second end is perpendicular to the plane of the faces of the first ends.
• the device is completed by a movable magnetic part 36 placed between the first ends 35 ⁇ and 35 2 of the first and second magnetic circuits and the second ends 35 'combined of these circuits.
• This part 36 is fixed to two flexible non-magnetic beams 38 and 39, embedded in a base 40. Naturally, one could use only one beam or use more than two.
• the operation of this device is as follows. As shown in Figure 3, the microactuator is at rest. When the left winding 32 ⁇ is traversed by a current, the left magnetic circuit 34 ⁇ is excited and the movable part 36 is drawn to the left. It then closes the left air gap which it defined with the first magnetic circuit. When it is the right winding 32 2 which is traversed by a current, it is the right magnetic circuit 34 2 which is excited and the movable part is drawn to the right. It then closes the right air gap which it defined with the second magnetic circuit.
• the microactuator described therefore has two stable working positions. Depending on the composition of the materials of the magnetic windings, the mobile part can keep one or the other of these positions. Even if the power supply to the windings is interrupted (case of hysteresis materials). However, the mobile part can also return to its rest position (in the case of soft materials). In the case of hysteresis materials, it will be necessary to demagnetize the magnetic circuit by supplying the appropriate winding with a current of correct direction so that the mobile part returns to its initial position.
• FIGS. 4A to 41 illustrate a method for producing a microactuator according to the present invention.
• a substrate 50 for example made of silicon (FIG. 4A); boxes are engraved therein which are filled with conductive material to obtain a sheet of conductors 52 located on a first level; we planarize the whole; an insulating layer 54 is deposited on which an insulating layer 56 (for example made of SiO 2 ) is formed, a so-called sacrificial layer.
• a layer of resin 58 is then deposited (FIG. 4B).
• a layer of magnetic material is deposited (FIG. 4C) to form the magnetic circuit 60 and the future mobile part 62; then we isolate the patterns ( Figure 4D).
• a new layer of resin 66 is then deposited (FIG. 4E) and the assembly is planarized (FIG. 4F).
• an insulating layer 70 (FIG. 4G) and a resin layer are deposited; new boxes are etched therein which are filled with conductive material to obtain a second layer of conductors 74 on a second level. Unrepresented connections allow the two layers to be united conductors to obtain a winding surrounding the magnetic part.
• FIG. 5 illustrates an application of the invention to the production of an electric microrelay.
• This device comprises the means already shown in Figure 4 and which bear the same references. It further comprises electrical contacts 80 and 82 arranged on the faces of the first ends 35 ⁇ and 35 2 of the magnetic circuits, three contact pads 91, 92, 93 and three tracks 94, 95, 96 connecting the pads to the contacts 80 and 82 and at the base 40.
• the second ends of the two magnetic circuits are, as in the previous example, merged with the end 35 'of the common part 30.
• the mobile part 36 When the left winding 32 is supplied, the mobile part 36 is drawn to the left and closes the electrical circuit 91, 93.
• the mobile part When the right winding 32 2 is supplied, the mobile part is drawn to the right and comes to close the electrical circuit 92, 93.
• the electrical contacts are only shown diagrammatically in FIG. 5. In reality, the tracks make it possible to transfer the contact pads towards the periphery of the microrelays where contacts can also be used to control the actuator.
• FIG. 6 illustrates another embodiment of a microactuator according to the invention in which the central branches of the magnetic circuits are not merged into a single branch 30, as in FIG. 3, but consist of two independent branches 30 ⁇ , 30 2 with second ends 35 ′ x and 35 ′ 2 whose faces are in planes parallel to each other and perpendicular to the planes of the faces of the first ends 35 ⁇ and 35 2 . Magnetic leaks are thus reduced.
• FIG. 7 illustrates an embodiment with central symmetry. In other words, the two structures
• the movable part 36 can then be connected in a symmetrical manner also to two bases 40 1; 40 2 , by two sets of two flexible beams (38 ⁇ , 39 ⁇ ) (38 2 , 39 2 ).
• Figure 8 shows an embodiment where the movable magnetic part 36 is movable in rotation about an axis 98. It can come to be pressed either under the end 35 ⁇ or under the end 35 2 of the two magnetic circuits 34 ⁇ and 34 2 depending on whether the current flows in winding 32 ⁇ or in winding 32 2 .

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Micromachines (AREA)
• Electromagnets (AREA)
• Reciprocating, Oscillating Or Vibrating Motors (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8862933

Family Applications (1)

Country Status (6)

Families Citing this family (10)

Family Cites Families (11)

• 2001
  • 2001-05-03 FR FR0105909A patent/FR2824417B1/fr not_active Expired - Fee Related
• 2002
  • 2002-04-29 JP JP2002588571A patent/JP4034657B2/ja not_active Expired - Fee Related
  • 2002-04-29 US US10/476,163 patent/US7049915B2/en not_active Expired - Fee Related
  • 2002-04-29 EP EP02735523A patent/EP1425764B1/de not_active Expired - Lifetime
  • 2002-04-29 DE DE60223566T patent/DE60223566T2/de not_active Expired - Lifetime
  • 2002-04-29 WO PCT/FR2002/001487 patent/WO2002091402A2/fr active IP Right Grant

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events