FR2792451A1 - Internal combustion (IC) engine inlet/outlet valve electromagnetic drive having flexible return with tongue section pivoting about axis and movement valve rod plane transformed. - Google Patents

Abstract

The electromagnetic drive mechanism has a flexible return section to move the valve (2) between an opening and closed position. The flexible return is made up of tongue sections (112,113) pivoting about an axis (E,F) which act on the valve spoke (3) transforming movements to the valve movement plane.

Description

- 1 - Electromagnetic actuation device The present invention is

  relates to the technical field of intake and exhaust valve actuators of an internal combustion engine. More specifically, it relates to an electromagnetic actuation device for a stem valve of an internal combustion engine, comprising electromagnetic means and elastic return means for moving said valve between an extreme open position

  o and an extreme closed position.

  Mushroom type valves are usually found in internal combustion engines. They are maintained, at rest, in a closed position, by means of springs. A cam, or any equivalent means, acts against the action of the spring to open the valve, the spring tending to keep the valve in the closed position. The camshaft is connected and rotates in synchronization with the engine crankshaft. Since the valves are connected to the crankshaft, the speed of opening and closing of the valves

  is related to the speed of rotation of the crankshaft.

  The use of electromagnetic actuators, for each valve, makes it possible to obtain valve opening and closing speeds which

  can be controlled independently of the engine speed.

  Electromagnetic actuators usually operate on the following principle. A plate, made of a ferromagnetic substance, is integral with the valve stem. This plate undergoes the forces of attraction or repulsion of variable magnetic field generators which are fixedly mounted on the actuator. These forces are of sufficient intensity to cause the displacement of the valve, via the plate which can come into abutment in two extreme positions, one of opening and one of

  valve closed, each close to a generator.

  -2- To optimize the intake and exhaust phases of the gases from the engine combustion chamber, it is desirable to obtain high valve opening and closing speed values, allowing a change almost instantaneous between the open position and the closed position of the valve. However, to obtain high opening and closing speeds, it is necessary to exert on the plate linked to the valve stem forces of high intensity, and therefore to be able to obtain magnetic fields of high intensity. . However these forces decrease rapidly i0 with the distance separating the plate from the generator. Obtaining magnetic fields of sufficient intensity represents unacceptable constraints

  for sizing generators.

  This is why electromagnetic actuators are generally equipped with return springs. The plate is fixed to helical springs which keep it, at rest, in a balanced position, most often

  equidistant from the valve opening or closing positions.

  When the plate leaves this position of equilibrium, the return springs exert a resulting force which tends to bring the plate back to this position of equilibrium. Thus, when the plate is in abutment in an open or closed position, the action of the return springs opposes the magnetic forces exerted on the plate, but since the plate is close to a magnetic generator, the forces exerted by the latter are significant. When we want the plate to leave a given extreme position to move to the other extreme position, we remove the magnetic field of the generator against which the plate is in abutment, and we activate the second generator. Consequently, the magnetic field is suddenly modified so that the magnetic forces and the restoring forces of the springs are superimposed, thus obtaining very significant initial accelerations, without however requiring magnetic fields of intensity.

too important.

  The publication EP0471614 describes a device according to the principle

previously stated.

  The return springs usually used are coil springs which are coaxial with the valve stem. However, such springs are bulky and represent a very significant constraint on the overall volume of the actuator, which is an essential criterion during the general dimensioning of the engine. In addition, these springs have a high inertia which penalizes the response times of the electromagnetic actuator. The present invention aims to significantly reduce the dimensions of an electromagnetic valve actuator while having

  very short response times.

  To this end, it provides an electromagnetic actuation device in which the elastic return means act on the valve by means of at least one latch that can pivot around an axis, and cooperating with means connected to the rod. valve, to transform a rotational movement of said latch into a displacement of the valve, by exerting a restoring torque, on the latch, around said axis, which, when the valve is at least in one of the extreme positions, tends

  to cause the valve to move away from said extreme position.

  According to another characteristic of the invention, the elastic return means of the valve comprise at least one coaxial torsion bar

with the latch.

  According to another characteristic of the invention, the torsion bar is

  mounted at one end integral with the latch.

  According to another characteristic of the invention, the torsion bar comprises at one end a lever arm on which comes to bear.

the end of at least one screw.

  Other characteristics and advantages of the invention will become apparent on

  reading the following description of three embodiments of

  the invention, given by way of nonlimiting example, with reference to the appended drawings in which: - Figure 1 represents a view in longitudinal section of a first embodiment of the device according to the invention, - Figure 2 represents a sectional view of the first embodiment, along line II-II of Figure 1, - Figure 3 shows views similar to Figure 1, of the device according to the first embodiment when the valve is respectively in position d 'opening and closing, - Figure 4 shows a longitudinal sectional view of a second embodiment of the device according to the invention, - Figure 5 shows a sectional view of the second embodiment, along the line VV of Figure 4, - Figure 6 shows an overview of the device of Figure 4 from which some elements have been removed, - Figure 7 shows an overview of a third embodiment of the device according to the in vention, - Figure 8 shows a longitudinal sectional view of the third

  embodiment of the device according to the invention.

  The numberings are kept for the elements common to

  different figures for the three embodiments.

  For the three embodiments of the invention, the elements having an identical or fundamentally identical function, have a 5- reference number o the first digit corresponds to the embodiment followed by the number of the element, which is the same for all embodiments. FIG. 1 represents a valve 2 with a rod controlling the inlet of the intake gases, or the outlet of the exhaust gases, into a cylinder of an internal combustion engine. This valve 2 is slidably mounted by its

  rod 3, of axis D, in a guide 4 partially mounted in the cylinder head 5 of the engine.

  The actuator 100 is composed of two half housings. Each half housing is composed of a magnetic core 106, 107, of substantially parallelepiped shape. Each magnetic core 106, 107 has, at the center of one face, an element projecting from the rest of the core. This element,

  as well as the part of the magnetic core located behind, and extending this

  ci, is commonly called the central nucleus. At the ends of the same face, two other projecting elements project. Due to its general shape,

  such a magnetic core 106, 107 is usually called an "E"> core.

  The central core is surrounded by a recess in which is placed a coil 108,109. On the edges of the face of the magnetic core 106,107, comprising the projecting end of the central core, extends a junction

  118,119, composed of a non-magnetic material.

  The two half housings are mounted so that the junctions 118, 119 are opposite. The two half housings are assembled and fixed to the cylinder head 5 by means of four screws 120. A bore passes through the two

  half housings to allow the passage of the rod 3 of the valve 2.

  The coils 108,109 can be crossed by electric currents (by means of connections not shown) and thus cause inductions in the magnetic cores 106,107 whose general direction of circulation is indicated by way of example by arrows in Figure 1. - 6The two junctions 118,119, placed opposite, release a space, between the two magnetic cores 106,107, in which are placed two latches 112,113, made of a ferromagnetic material. Each junction 118,119 has eight half bearings, which form four bearings when the junctions 118,119 are mounted opposite. These four bearings are two to two coaxial, and of axes E and F respectively. The opposite end to the valve 2 of each latch 112,113 has two cylindrical parts 1 1OA, 1OB, 1 1 A, 1 1 lB, each engaging in a bearing, and allowing the pivoting of the latch 112,113 about the axis E , F of both

corresponding bearings.

  This end further comprises a bore 114,115 in which is placed, coaxially with the two bearings, a torsion bar 116,117 (Figure 2). Each torsion bar 116,117 has one end mounted tight with the latch 112,113 and the other end having a projecting part serving as a lever arm 130,131. Each torsion bar 116, 117 is locked in rotation, in one direction, by the cooperation of the lever arm, 131 with an adjustment screw 121, 122. The torsion bar 117 is locked in rotation, by the screw 122, in the trigonometric direction. Bar

  116 is locked in rotation, by the screw 121, in the opposite direction.

  When each latch 112,113 pivots about its axis E, F, in a direction of rotation for which the torsion bar 116,117 is in abutment against the adjusting screw 121,122, a return torque is exerted by the torsion bar 116,117 on the latch 112,113. Consequently, a return torque will be exerted on the latch 112 when it is pivoted towards the magnetic core 106, and, conversely, a return torque will be exerted on

  the latch 113 during its pivoting towards the magnetic core 107.

  Each latch 112,113 is provided at one end with a fork 123,124 which cooperates with a groove 125 with a flange 126 screwed onto the end of the rod 3 of the valve 2. The flange 126 is held in position by a lock nut 127 also screwed onto the end of the rod 3 7- of the valve. The connection between the forks 123,124 and the flange 126 is such that the valve 2 is free to rotate about the axis D. When the lugs 112,113 pivot about their axis E, F, the forks 123,124 rest on the walls of the groove 125 and cause the displacement of the rod 3 and of the valve 2. A movement of rotation of the lugs 112, 113 corresponds to a displacement of the valve 2 along the axis D

of its stem 3.

  The latches 112, 113 come into abutment, during their pivoting, with the magnetic cores 106, 107. When the two latches 112, 113 are in abutment with the core 106, the valve 2 is in the closed position (FIG. 3). When the stop is made with the core 107, the valve 2 is in the open position. The two tabs 112,113 have flat faces 128A, 129A and 128B, 129B which come into abutment with the walls of the cores 106,107 when the tabs 112,113 are respectively in the high or low position, so that the contact surfaces between the tabs 112,113 and the magnetic nuclei 106,107 are the most

important possible.

  The actuator 100 may include an oil inlet 132 in order to lubricate the assembly. It is also possible to consider lubrication

autonomous of the system.

  The actuator 100, according to this first embodiment, operates as follows: in the absence of magnetic excitation, the torsion bars 116, 117 are adjusted by means of the adjustment screws 121, 122 so that the valve 2 is located halfway between the open position and the closed position, which corresponds to latches 112,113 substantially equidistant from the two cores 106,107. The adjustment to be made partly depends on the torsion coefficient specific to each torsion bar

  116.117, which may be different for each of them.

  -8- In normal operation, the valve is either in position

  opening, or in the closed position.

  Let us consider the case where the valve 2 is in the closed position, which corresponds to latches 112, 113 pressed against the magnetic core 106. An electric current then passes through the coil 108, the direction of this current being such that a magnetic force s '' exercises on the latches 112, 113, tending to keep them pressed against the wall of the magnetic core 106

  in which a magnetic induction has developed.

  The planar faces 128A, 129A being almost in perfect contact with the wall of the corresponding magnetic core 106, the magnetic forces exerted on the latches 112, 113 are very large. The latches 112, 113 can therefore be kept pressed against the electric core 106 without

  require the use of excessive electrical power.

  To move the valve 2 in the open position, the passage of the electric current from the coil 108 to the coil 109 is changed. On the one hand, the latches 112, 113 are subjected to the return torques of the torsion bars 116, 117 which tend to move them away from the high position, on the other hand, they are subjected to a force exerted by the magnetic induction developed by the magnetic core 107. The acceleration undergone by the latches 112, 113 therefore causes them to come to be pressed almost instantaneously against the wall of the magnetic core 107. The valve 2 is then in the open position. Again, a low electrical power is sufficient to keep the lugs 112,113 pressed against the electric core 107 given the almost perfect contact between the flat faces 128B, 129B of the lugs 112,113 and the wall of the core

magnetic 107.

  Figures 4,5 and 6 show a second embodiment of a

  electromagnetic actuator according to the invention.

  Analogously to the first embodiment, the valve 2 is guided slidingly by its rod 3, of axis D, in a guide 4 mounted in -9part in the cylinder head 5 of an internal combustion engine, and partly in

actuator 200.

  This actuator 200 consists of two half housings. Each half case has a magnetic core 206.207, similar to that used for the first embodiment, that is to say of the "E" type, comprising a central core. Each magnetic core 206.207 is equipped with two coils 208A, 208B and 209A, 209B, arranged on either side of the central core. When the current crosses these coils 208A, 208B, 209A, 209B, the circulation of the magnetic induction developed in each magnetic core 206,207 is symbolized by arrows on the

figure 4.

  Each core 206,207 and the two associated coils 208A, 208B, 209A, 209B are contained in a half carcass 233,234, composed of a non-magnetic material. Four screws 220 hold the two half-carcases 233,234, mounted opposite, and fix the assembly on the cylinder head 5 of the engine. A bore is made in the magnetic cores

  206.207 allowing the passage of the valve stem 3.

  Once mounted opposite, the two half carcases 233,234 define a space, between the two magnetic cores 206,207, in which can move a plate 235 linked to the valve 2. The connection is ensured by a thread made at the end valve stem 3. Two washers 236, 237 enclose the plate 235 with a non-zero clearance so as not to prevent the valve 2 from turning on itself. Washers

  236.237 are held in position by a lock nut 227.

  This plate 235 is likely to be pressed against the walls

magnetic cores 206,207.

  Two torsion bars 216,217 (FIG. 5) recall the plate 235. The connection between the torsion bars 216,217 and the plate 235 is carried out using two lugs with two branches 212,213. Each half 10- carcass 233,234 contains two half bearings, which can form two bearings,

  of axis E and F, once the two half carcases are mounted opposite.

  The end of each latch 212,213, opposite the plate 235, has a cylindrical part 210,211 (FIG. 6), and allows the latch 212,213 to pivot about the axis E, F of the corresponding bearing. The torsion bars 216,217 are embedded at one end in the latches 212,213 and locked in their movement at their other end by the cooperation of lever arms 230,231 and 4 adjusting screws

  221A, 221B, 222A, 222B (Figure 6), screwed onto the half carcases 233,234.

  The presence of two adjustment screws 221A, 221B, 222A, 222B (instead of a screw 121,122 for the first embodiment) by latch 212,213 means that the torsion bar 216,217 exerts a restoring torque, on the associated latch 212,213 , as soon as it departs from its equilibrium position, and this in both directions. The connection between each latch 212,213 and the plate 235 is ensured by an axis 238,239 passing through the plate 235 through a

buttonhole 240,241.

  The half carcass 233 has an access 232 to the lock nut 227, which can also be used for the arrival of oil to ensure the lubrication of the assembly. It is still possible, in this embodiment, to envisage

  autonomous lubrication of the system.

  The operation of the actuator 200, according to this second embodiment, is substantially identical to that of the first mode: in the absence of magnetic excitation, the torsion bars 216, 217 are adjusted by means of the adjustment screws 221A, 221B, 222A, 222B so that the plate 235 is in equilibrium in a position substantially equidistant from the

  positions in abutment against the magnetic cores 206,207.

  During normal operation of the alternator, each magnetic core 206,207 is alternately excited by the passage of a current in the two coils surrounding it 208A, 208B and 209A, 209B. The plate 235 is pressed against the excited core 206 or 207. Valve 2 is located

- 11 -

  then in the open or closed position. When it is desired to pass from one position to another, the excitation of an electrical core 206, 207 is switched to the other. Magnetic and restoring forces are added, thus causing the displacement of the plate 235, and consequently, that of the valve 2, with a significant acceleration. The buttonholes 240, 241 allow a translation of the axes 238, 239 of the latches 212, 213 during the displacements of

plate 235.

  Figures 7 and 8 show a third embodiment of a

actuator 300 according to the invention.

  The actuator 300 ensures the opening and closing of the valve 2, guided slidingly by its rod 3, of axis D, in a guide 4 mounted in part

  in the cylinder head 5 of an internal combustion engine.

  This actuator 300 (Figure 7) consists of two magnetic cores 306,307 substantially parallelepiped. At the two ends of a face of each core are projected two projecting elements. Such a nucleus is said to be of the "C" type. Each core 306,307 is preferably composed of laminated sheets. Two projections 318A, 318B, 319A, 319B, attached to the ends of the magnetic core 306,307 and made of a non-magnetic material, are adapted to position vis-à-vis the two magnetic cores 306,307. All

  is thus held in place by two screws 320.

  Two coils 308,309 are placed respectively around the magnetic cores 306,307 and are capable of inducing in these cores

306,307 magnetic induction.

  A latch 312 is mounted between the two magnetic cores 306,307. This latch 312 comprises, at its end opposite to the valve 2, a cylindrical part (not shown) which can pivot in a bearing, of axis E, formed from two half bearings situated respectively on the

projections 318A, 319A.

  - 12- A torsion bar 316, is mounted, as in the first two embodiments, clamped at one end in the pawl 312, the other end comprising a projecting part serving as a lever shaft 330 and coming to bear against the ends of two adjustment screws 321A, 321B, screwed onto the projections 318A, 319A. At its second end, the latch 312 is linked to the end of the valve stem 3 2 (Figure 8). This connection is ensured by the cooperation of the end of the latch 323 with a flange 326, comprising a groove 325, screwed onto the rod 3 of the valve 2. This flange 326 is blocked by a lock nut 327, itself screwed onto the end of the rod 3 of the

valve 2.

  The end of the latch 323 is provided with two pins (not

  shown) which are housed in the groove 325 of the collar 326.

  This connection is free so as to be able to allow on the one hand an articulation between the lug and the flange 326, on the other hand so as not to block

valve 2 in rotation.

  A third coil 342 is placed between the two magnetic cores 306,307, so as to surround the latch 312. An electrical insulator 343 prevents any electrical contact between the coil 342 and the

coils 308 and 309.

  The operation of the actuator 300, according to the third embodiment, is as follows: in the absence of magnetic excitation, the adjustment of the screws 321A, 321B is such that the latch 312 is in a position

  equidistant equilibrium of the two magnetic nuclei 306,307.

  In normal operating mode, the coils 308,309 are crossed by a current so as to create an overall induction field in the two magnetic cores 306,307 which closes on itself. These currents can be permanent. An example of an induction field at -13 -

  the interior of the cores 306, 307 is symbolized in FIG. 8 by arrows.

  These both rotate counterclockwise.

  The coil 342 is itself crossed by a current, thus creating an induction through the pawl 312. If the direction of this induction is such that the resulting magnetic field closes on the field generated by the magnetic core 306 (as it is shown schematically in Figure 8), the forces exerted on the latch 312 tend to keep it pressed against it. They are both forces of attraction of the magnetic core 306 and repulsion forces of the magnetic core 307. The valve 2 is then in the closed position. Once the latch 312 is thus pressed against the core 306, if the direction of the current flowing through the coil 342 is reversed, the direction of induction is reversed through the latch 312, the latter then undergoes repulsion forces from the magnetic core 306 and forces of attraction of the magnetic core 307. It also undergoes the restoring torque of the torsion bar 316 which tends to bring it back to the middle position. All these forces therefore tend to move the latch away from the magnetic core 306 with strong acceleration and to press it against the metal core 307. The

  valve 2 is then in the open position.

  It can thus be seen that the reversal of the direction of the current in the coil 342 alternately ensures the opening and closing of the valve. In this third embodiment, it is possible to replace the magnetic generators, consisting respectively of the cores 306,307 and the coils 308,309, by permanent magnets. Indeed, it is enough that only the current

  passing through the coil 342 varies to allow pivoting of the latch 312.

  For the three embodiments described, the use of torsion bars instead of the usual helical springs makes it possible to obtain greatly reduced dimensions for the actuators, compared to the

usual actuators.

  The two catches for the first and the second embodiment, and the single catcher for the third, perform each of the rotational movements. The inertias influencing the response times of the actuator are therefore much lower than those of a plate carrying out a translational movement, and of helical springs equipping the

  conventional electromagnetic actuators.

  In addition, the latch (s) being in rotation, the mean air gap separating it from the magnetic generator is reduced compared to that of a plate undergoing translation, which makes it possible to use magnetic forces of lower intensity and by following to achieve reduced consumption

of electrical energy.

  Finally, in the three embodiments, accessible screws allow easy and precise adjustment of the equilibrium position of the latch (s). In particular, such an adjustment can be made once the actuator

  mounted, without requiring disassembly thereof.

  The present invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example. On the contrary, the invention includes all the technical equivalents of the means described

  as well as their combinations if these are carried out according to his spirit.

  It is possible to replace the torsion bars by any other means capable of exerting a restoring torque at the level of the pivot axis of the latch. Thus, a spiral spring can be used, one end of which is fixed to the latch and the other to a fixed element, the carcass or the projections of

  connection of magnetic cores for example.

-15 -

Claims (9)

  I. Electromagnetic actuation device (100,200,300) for valve (2) with rod (3) of an internal combustion engine, comprising electromagnetic means and elastic return means for moving said valve (2) between an extreme position d opening and an extreme closed position, characterized in that the elastic return means act on the valve (2) by means of at least one latch (112,113,212,213,312) which can pivot around an axis (E, F) , and cooperating with means connected to the valve stem (3), to transform a rotational movement of said latch (112,113,212, 213,312) into a displacement of the valve (2), said elastic return means exerting a return torque, on the latch (112,113,212,213, 312), around said axis (E, F), which, when the valve (2) is at least in one of the positions   extremes, tends to make it move away from said extreme position.   2.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to claim 1, characterized in that the elastic return means of the valve (2) comprise at least a torsion bar   (116,117,216,217,316) coaxial with the latch (112,113,212,213,312).   3.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to claim 2, characterized in that the torsion bar (116,117,216,217, 316) is mounted at one end integral with the latch (112,113,212,213,312).   4.Electromagnetic actuation device (100,200,300) of a valve of an internal combustion engine according to any one of   claims 2 or 3, characterized in that the torsion bar   (116,117,216,217,316) has at one end a lever arm (130, 131,230,231,330) on which the end of at least comes to bear   a screw (121,122,121A, 122A, 121B, 122B, 321A, 322B).   -16- 5.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to one   any of claims 2 to 4, characterized in that the second   end (123,124,323) of the latch (112,113,312) cooperates with a groove (125,325) of a flange (126,326) held on the valve rod (3) (2). 6.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to one   any of claims 2 to 5, characterized in that it comprises two   latches (112,113,212,213) located on either side of the valve stem (3).   7.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to one   any of claims 2 to 6, characterized in that the second   end of the latch (212,213) cooperates with a plate (235) held on the valve stem (3).   8.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to one   any of claims 1 to 7, characterized in that the means   electromagnetic comprise two magnetic generators, between which the latch (112,113,212,213,312) pivots, each magnetic generator being composed of a magnetic core (106,107,206,207,306,307) and at least one coil (108,109,208A, 208B, 209A, 209B, 308,309) adapted to generate magnetic induction in the magnetic core (106,107,206,207,306,307).   9. Electromagnetic actuating device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to claim 8, characterized in that each magnetic core (106,107,206,207) has a central core, projecting by compared to   magnetic core (106,107,206,207).   -17- IO. Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to one   any of claims 1 to 7, characterized in that the means   electromagnetic components are made up of two permanent magnets, between which the latch (312) pivots. 1 1.Electromagnetic actuation device (100,200,300) of valve (2) with rod (3) of an internal combustion engine according to claim 8 or 10, characterized in that the electromagnetic means further comprise a coil d induction (342) surrounding the latch   (312) so as to generate a magnetic induction in said latch (312).