FR2849100A1 - Single coil electromagnetic valve drive having palette pivoting two end positions with flexible unit and center with additional section/permanent magnet with second active face - Google Patents

Abstract

The electromagnetic drive has a palette (2) pivoting between two end positions with a flexible unit (5,7) and a coil (14) with associated valve. There is a center (8) with an additional section and permanent magnet (13). There is a second active face (16) in contact with the palette.

Description

The invention relates to a single coil electromagnetic actuator

Swivel.

  BACKGROUND OF THE INVENTION Electromagnetic actuators of a vane valve mounted mobile between two extreme positions are known under the effect of springs mounted in opposition and of a coil associated with a core having a main part which passes through the coil and which has on either side of the coil two ends which have first portions of active face which are in contact with the pallet when the latter is in one or the other of the extreme positions.

  In known valve actuators, when the valve is in the closed position, the valve actuated valve is generally detached from the valve to ensure the support of the valve against its seat The spring linked to the valve therefore ceases to '' act on the plunger which is then no longer subjected to the force of the other spring The effort to develop to maintain the pallet in the extreme position corresponding to the closed position of the valve is therefore greater than effort to develop to maintain the pallet in the extreme position corresponding to the open position of the valve.

  In the actuator of document EP-A 1 174 596, the main part is separated into two core elements by a permanent magnet so that the flux thereof closes in the pallet when the latter is in 30 l one or other of the extreme positions The holding force exerted by the permanent magnet on the pallet is substantially identical for each of the extreme positions.

  To take account of the difference in holding force between the extreme positions, it is therefore necessary to size the permanent magnet so that it is capable of providing a magnetic flux capable of inducing the holding force on the pallet. Most important.

  This effort, greater than necessary to retain the pallet in the extreme position corresponding to the open position of the valve, then penalizes the dynamics of the pallet, and obliges to supply the coil with a greater current than necessary to take off the pallet in the extreme position corresponding to the open position of the valve.

  OBJECT OF THE INVENTION The object of the invention is a single coil actuator with permanent magnet, in which the action of the magnet on the pallet can be differentiated according to the very ex15 positions.

  BRIEF DESCRIPTION OF THE INVENTION In an actuator according to the invention, the core comprises at least one additional part adjacent to one of the ends of the main part and which is magnetically associated with this end by means of a magnet permanent, the additional part comprising a second active face portion which extends so as to be in contact with the pallet when the latter is in contact with the first active face portion carried by the other end of the main core part .

  Thus, the flow of the permanent magnet closes, in the pallet only for the extreme position in which the pallet is in contact with the second active face portion carried by the additional core part When the pallet is in the other extreme position, the flow of the permanent magnet can not close in the pallet so that the permanent magnet does not exert a holding force on it.

  It is therefore possible, in a single-coil actuator according to the invention, to make the action of the permanent magnet asymmetrical in one or the other of the extreme positions.

  According to a particular embodiment, the additional part of the core comprises a third portion of active face which extends so as to be in contact with the pallet when the latter is in contact with the first portion of active face carried by the end of the main core part magnetically associated with the additional core part.

  Thus, the flux of the magnet closes in two different ways, depending on whether the pallet is in one or the other of the extreme positions: in one of the extreme positions, the flux of the permanent magnet closes by the second active face portion of the additional core part and by the first active face portion of the other end passing through the coil in the main core part from one end to the other; in the other of the extreme positions, the flux of the permanent magnet closes by passing through the pallet through the third active face portions of the additional core part and through the first active face portion of the associated end, therefore staying in the end zone without passing through the coil.

  These two separate paths, not leading to the same areas of contact with the pallet, allow the permanent magnet to exert on the pallet holding moments in the two extreme positions, these moments being distinct.

  BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in the light of the description which follows with reference to the figures of the appended drawings in which: FIG. 1 is a schematic view of an actuator according to the invention illustrating the flow path magnetic during the pallet attraction phase; Figure 2 is a view similar to that of Figure 1 illustrating the path of magnetic flux during the pallet holding phase; FIG. 3 is a view similar to that of FIG. 1 illustrating the path of the magnetic fluxes during the phase of separation of the pallet.

  DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. 1, the actuator 10 of the invention is here mounted on a cylinder head 4 of an engine for actuating a valve 1.

  The actuator 10 comprises a pallet 2 made of ferromagnetic material mounted to rotate about an axis 3.

  The pallet 2 has one end which is clamped between on the one hand the end of the valve 1 which is pressed against the pallet 2 by a first spring 5, and on the other hand the end of a guide 6 mounted to slide coaxially at 20 the valve 1, which is pressed against the pallet 2 by a second spring 7 mounted in opposition with respect to the first spring 5.

  The springs 5,7 define an equilibrium position of the pallet 2 corresponding to a semi-open position of the valve 1, between two extreme positions of the pallet 2 corresponding respectively to the open position and to the closed position of the valve .

  The actuator comprises a core 8 made of ferromagnetic material, comprising a main part of the core 9 having the general shape of a C which passes through a coil 14 The main part of the core 9 has two ends 11 on either side other of the coil 14.

  Additional core parts 12 are adjacent to each of the ends 11 and are magnetically associated with them by means of permanent magnets 13 which are arranged so that their magnetization is directed in the same direction, symbolized in the figures by the arrows 30.

  The ends 11 of the main part of the core 9 and the additional parts of the core 12 have active faces with which the pallet 2, when it is in a position close to one or the other of the extreme positions, has a zero or very low air gap.

  Each of the active faces comprises: a first active face portion 15 which extends opposite a first face of the pallet 2 and which is formed in one of the ends 11 of the main core part 9; a second active face portion 16 which extends opposite the second face of the pallet 2 and which is formed in the other additional part of the core 9, extending on the other side relative to the axis 3 from pallet 2; and finally, a third active face portion 17 which extends opposite the first face of the pallet and which is formed in the additional core part 12 associated with the end 11 carrying the first active face portion 15, the third active face portion 25 17 extending on the same side relative to the axis 3 of the pallet 2 as the first active face portion 15.

  For the description of the operation which follows,

  reference will be made to a lower part and an upper part relative to a median plane passing through the axis 3 of the pallet 2.

  The operation of the actuator according to the invention is as follows.

  It is assumed, as illustrated in FIG. 1, that the vane 2 is closer to the extreme position corresponding to the closed position of the valve.

  To attract the pallet 2 to this extreme position, the coil 14 is supplied to generate a magnetic flux 34 which circulates in the main part of the core 9 up to the upper end 11, passes through the permanent magnet 13 above, circulates in the additional core portion 12 upper to pass through the pallet 2 by crossing the gap between the upper face of the pallet 2 and the second portion of active face 10 upper 16.

  Then the magnetic flux 34 circulates in the pallet 2 to pass through the lower end 11 by crossing the gap between the lower face of the pallet 2 and the first portion of the active face 15 below, and thus close in the main part. of core 9.

  This flow exerts on the pallet 2 a moment around the axis 3, which causes the rotation of the pallet against the spring 7.

  Furthermore, the upper permanent magnet 13 generates a magnetic flux 35 which has the same path as the magnetic flux 34 generated by the coil 14 The magnetic flux 35, which passes through the coil 14, therefore exerts on the pallet 2 a moment similar to that imposed by the magnetic flux 34 generated by the coil 14.

  As for the magnetic flux 36 generated by the lower permanent magnet 13, it closes on passing through the pallet 2 by crossing on the one hand the air gap between the third portion of active face 17 below and the lower face 30 of the pallet 2 , and on the other hand the air gap between the underside of the pallet 2 and the first portion of the active face 15 below. This flow therefore does not pass through the coil 14 The first and third portions of the active face being located on the same 35 side of the axis 3 of the pallet 2, this flow therefore exerts on -7 the pallet 2 a moment tending to rotate the latter in the same direction as the moments exerted by the magnetic fluxes generated by the coil 14 and by the permanent magnet 13 upper.

  The three magnetic fluxes 34, 35, 36 add their effects to rotate the pallet 2 against the spring 7 and attract the pallet 2 to the extreme position corresponding to the closed position of the valve.

  At the end of the race, when the pallet 2 is close to the active face 10, the magnetic flux 34 generated by the coil 14 can be cut or even reversed in order to slow down the pallet 2 and control the approach speed of the pallet 2 against the core 8.

  As can be seen in FIG. 2, when the pallet is in abutment against the active face of the core 8, the magnetic flux 35 of the upper permanent magnet 13 and the magnetic flux 36 of the lower permanent magnet 13 are then sufficient to hold the pallet against the core 8.

  In this respect, the active face portions 15, 16, 17 in contact with the pallet 2 have areas smaller than that of the faces of the permanent magnets 13, which causes a concentration of magnetic flux which tends to increase the force of attraction exerted by the permanent magnets 13 on the pallet 2.

  To take off the pallet 2, and as can be seen in FIG. 3, the coil 14 is supplied to generate a reverse magnetic flux 37 in the opposite direction to the magnetic flux 35 generated by the permanent magnet 13 above and passing exactly through the same path that this path flows.

  The flux 37 exerts on the pallet 2 a moment opposite to the moments generated by the magnetic fluxes 35.36 of the permanent magnets 13, and at least partially compensate for these until they are no longer sufficient to retain the pallet 2 against the spring 7 The pallet 2 then leaves the extreme position in which it was maintained.

  It should be noted that the two permanent magnets 13 5 exert different moments on the pallet When the pallet is in the other extreme position, the roles of the permanent magnets 13 are reversed so that the lower permanent magnet 13 generates a magnetic flux which passes through the coil 20, while the upper permanent magnet 13 generates a magnetic flux which remains at the corresponding end, without passing through the coil.

  Each of the magnets therefore exerts a different action on the pallet depending on whether the pallet is in one or the other of the extreme positions.

  We can take advantage of this property to make the total action of the two magnets asymmetrical, in particular to take into account a difference in force imposed by the springs in one or other of the extreme positions. This asymmetry can be obtained by choosing two magnets with different magnetic forces, or by differentiating the position of the first, second or third portions of the active face with respect to the axis of the pallet for both of the active faces.

  It is of course quite possible to make the actuator perfectly symmetrical by choosing identical magnets and ensuring perfect geometric symmetry of the lower and upper parts.

  According to a particular aspect of the invention, the second and third surface portions of the same additional core portion 12 are arranged on either side of the axis 3 of the pallet 2 and are separated by a recess 20 extending opposite the axis of the pallet 2 The purpose of this recess is to pass the flows mainly through one or the other of the active face portions, without these being able to travel through the vicinity of the axis of the pallet 2, which would have the consequence of reducing the moments which are imposed on the pallet 2.

  The invention is not limited to the particular embodiment of the invention which has just been described, but on the contrary encompasses any variant coming within the scope of the invention as defined by the claims.

  Although in the illustrated embodiment, the actuator of the invention comprises two permanent magnets, it is possible to delete one of the magnets.

  In this case, the remaining permanent magnet will naturally have an asymmetrical action on the pallet, due to the different paths of the flux generated by the permanent magnet when the pallet is in one or the other of the extreme positions.

  Although in the illustrated embodiment, the magnetic fluxes generated by the coil pass through one or other of the magnets, it is possible to avoid this situation by providing, adjacent to the magnets, surface portions of the main core part and the corresponding additional core part which have an air gap much less than a thickness of the magnet between them. The surface portions then define a magnetic path for the magnetic fluxes generated by the passing coil. near losses, outside of the permanent magnets This arrangement avoids possible problems of demagnetization of the magnets under the effect of the flux generated by the coil.

  Although the additional core parts have been illustrated as comprising second and third active face portions, the third active face portion may be omitted, thus making it difficult, or even preventing the flow of the permanent magnet to close, according to a path that does not pass through the coil.

  Although the additional core parts have been illustrated as being in one piece, they can be made in two parts separated by a ferromagnetic insert on each of which extends one of the second or third active face portion.

  It is also possible to design additional core parts for which the second and third active face parts are combined and consist of cylindrical surfaces in permanent contact with an axis of the pallet 2.

Claims (5)

  1 Vane electromagnetic actuator (2) pivoting between two extreme positions under the effect of an elastic member (5,7) and a coil (14) associated with a core (8) comprising a main core part ( 9) which extends through the coil (14) and which has on either side of the coil (14) two ends (11) having first active face portions (15) which extend to be selectively in contact with the pallet (2) when the latter is in one or other of the extreme positions, characterized in that the core (8) comprises at least one additional core part (12) extending in sight of one of the ends (11) of the main part of the core (9) and which is magnetically associated with this end (11) by means of a permanent magnet (13), the additional part of the core (12 ) having a second active face portion (16) which extends to be in contact with the pallet (2) when 20 this is in contact with the first active face portion (15) of the other end (11) of the main core part (9).   2 actuator according to claim 1, characterized in that, the additional core part (12) has a third active face portion (17) which extends to be in contact with the pallet (2) when the latter is in contact with the first active face portion (15) of the end (11) of the main core part (9) which is magnetically associated with the additional core part (12).   3 actuator according to one of the preceding claims, characterized in that the core (8) comprises two additional core parts (12) which each extend opposite one of the ends (11) of the main part of core (9) and which are magnetically associated with the corresponding end (11) by means of permanent magnets (13).   4 Actuator according to claim 1, characterized in that the additional core part (12) has with the main core part (8) an air gap much less than a thickness of the permanent magnet (13) associated, so that 'Except for losses, the flux generated by the coil (14) passes through the air gap while passing out of the permanent magnet (13).   5 Actuator according to claim 1, characterized in that the additional core part (12) comprises a recess (20) in the vicinity of an axis of rotation of the pallet (2).