FR2812024A1 - VALVE ACTUATOR FOR INTERNAL COMBUSTION ENGINES - Google Patents

Abstract

The valve activator comprises two electromagnets (1,2) each comprising a supply reel (5,6) and a magnetic armature (8), located between the electromagnets, connected to a valve driving part (9) against the action of a commutation energy storage spring (13,14). A permanent magnet (22,23) interposed in the body of each electromagnet has its magnetization parallel to the field generated in the body by the corresponding supply reel.

Description

The present invention relates to valve actuators of

internal combustion engines.

  A valve actuator of the aforementioned type generally comprises

  two electromagnets between which is provided an air gap.

  In the air gap is mounted a magnetic pallet linked to the valve to be actuated, movable by the electromagnets against energy storage springs. The arrangement thus formed forms a harmonic oscillator in which the storage of the energy necessary for rapid switching is ensured

  by the springs and the change of position is controlled using the electroai-

  mants. This system is apparently simple, but it has technical limitations. The control of the valve position is ensured by means of the two coils of the electromagnets by application of current which generates a magnetic field producing a force F.

  In the saturation phase, this force is constant and not controlled

ble by the current.

  Excluding saturation, this force is proportional to the square of the current

  thrown into the coils and inversely proportional to the square of the air gap.

  This double non-linearity makes it very difficult to control the valve

by electromagnets.

  Indeed, at a great distance, that is to say at a distance equal to 3 to 4

  mm, the force applied to the pallet is very low, which reduces the range of use

  sation and poses a problem regarding the initialization of the actuator.

  At the intermediate distance between 1 and 3mm, the force is diffi-

  cilly controllable by the current due to the pre-quadratic dependence

  cited. At a short distance, when the valve approaches its seat for example, the force increases very quickly, practically without possible control

  by the current. There is a runaway effect responsible for the impact noise.

  This phenomenon is quite comparable to the click produced by electroai-

mant of a closet door.

  The force exerted on the pallet is always positive due to its

  proportionality to the square of the coil supply current.

  Consequently, the valve cannot be slowed down if there is a visible

too large a size.

  To this problem relating to force is added the significant presence of

  eddy rants, which attenuate and delay the effect of the coils.

  In order to remedy these drawbacks, we have been obliged so far,

  to make the valve control device more complex, using caps

  high-performance valve position sensors, precise and rapid control electronics, a sophisticated software strategy and possibly having

  use of a mechanical shock absorber.

  Despite these increases in the complexity of means of

  control and performance expected performance in terms of impact speed

  risk remaining insufficient forcing the implementation of additional means

  additional sound insulation.

  On admission, the actuator must be able to supply the necessary energy

  to switch. This is to compensate for friction losses which

  wind at approximately 0.2 J for a stroke or lift of 8 mm from the valve, and by

  therefore from the range of electromagnets.

  The energy provided by an electromagnet throughout the race

  above, is equal to the integral of the force.

  This energy is relatively low due to the strong decrease

  strength for the great air gap values.

  For example, at a motor rotation speed of 6000 rpm, on a two-stroke cycle, which would optimize the use of the actuator, the useful power would be 20 W, which is low compared to its mass , around 1 kg and

its large volume.

  For a 500 cc combustion engine with a unit displacement, we can

  satisfy such dimensions although they remain a handicap.

  However, these dimensions are not compatible with cylinders.

weaker unit feeds.

  At the exhaust, the energy to be supplied is around 1.4 J to fight

  against pressure in the cylinder chamber when opening the valve.

  It was found during tests that the current actuators are insufficient

  exhaust and do not allow the engine to run at

full load.

  In conclusion, the current actuator has a low power density which limits its use for controlling engine intake valves.

  of unit displacement greater than or equal to 500 cm3.

  The efficiency of an actuator is the ratio between the mechanical energy returned (useful) and the electrical energy consumed. It is around 30%, losses being mainly due to induced currents and losses by effect

Joule.

  An engine revolution has a duration of 60 ms at 1000 rpm, while a

  valve transition takes approximately 3.5 ms. It is clear that at low speed, the system

  teme is statistically very often in a stable position, either open or closed.

  To keep the valve in the open or closed position,

  plique a current in the coil on the side concerned, in order to fight against the force

  of the spring which tends to return the valve to the intermediate position.

  The actuator lends itself well to this operation, since the force pro-

  duite by the electromagnet is naturally raised to zero air gap.

  However, the consumption of electric current weighs heavily in the calculation of the consumption of the vehicle which is done at an average speed of 1600

  RPM approximately, representative of the actual use of vehicles which contains a lot

  blow of urban driving at low engine speed.

  For example, 100 W electrical requires approximately 200 W for the

  internal combustion engine, approximately 1.5% of fuel consumption per cycle.

  However, maintenance consumption could be theoretically zero

  since it produces no work.

  In conclusion, the consumption of the current actuator is high and

can be reduced.

  Current actuators have a relatively large height.

  aunt due to stacking of springs, two electromagnets and a plate

actuator or pallet.

  When parked, on the engines of current vehicles, there is always

a cylinder in compression.

  The engine thus provides an additional parking brake which some

  some users use as an additional brake to the handbrake, in particular

in the ribs.

  When using the electromagnetic actuators, the valves are in the equilibrium position in the middle, so that all the chambers of the engine are at atmospheric pressure and there is no longer any additional braking possible. Finally, the actuator itself is relatively inexpensive due to its simplicity, but the associated control electronics as well as the

  valve position, are complex and therefore expensive.

  The invention aims to remedy the drawbacks of electric actuators

  tromagnetics of conventional valves by creating an actuator, which while being of a relatively low cost price, presents performances

  improved in all the areas mentioned above.

  It therefore relates to an electromagnetic valve actuator

  internal combustion engine comprising two electromagnets comprising each

  cun a supply coil, a magnetic pallet disposed between the two electromagnets, linked to a valve drive member against the action of at least one switching energy storage spring of said switching

  valve, characterized in that in the magnetic body of at least one electric

  troagnet is interposed a permanent magnet whose magnetization combines with

  field generated in said body by the supply coil.

  According to other characteristics: - the magnetic bodies of the two electromagnets defining between them an air gap in which said pallet is mounted movable against at least one antagonistic switching energy storage spring, a permanent magnet is interposed in the magnetic body of each electromagnet;

  - the permanent magnet is interposed in the magnetic body of the elect

  top magnet; - The body of each electromagnet comprises two pole pieces, a permanent magnet being interposed between the two pole pieces of the body of each electromagnet; - the permanent magnet is placed in the body of the electromagnet

  so that the magnetization of the permanent magnet is parallel to the generated field

  dré in said body by the corresponding supply coil; The permanent magnet is arranged in the body of the electromagnet so that the magnetization of the permanent magnet is inclined relative to the

  field generated in said body by the corresponding supply coil.

  The invention will be better understood on reading the description which will

  follow, given only by way of example and made with reference to the accompanying drawings, in which: - Fig.1 is a schematic view of a first embodiment of an electromagnetic actuator with two electromagnets according to the invention;

  - Fig.la is a partial schematic view of a variant of the ac-

the holder of FIG. 1;

  - Fig.2 is a schematic sectional view of another embodiment

  the electromagnetic valve actuator with two electromagnets followed

  before the invention; - Fig.3 is a schematic sectional view of yet another embodiment of the electromagnetic valve actuator according to the invention; and - Fig.4 is a comparative graph of the force exerted on the pallet

  an actuator with or without a permanent magnet.

  The electromagnetic valve actuator shown in Figure 1,

  comprises two electromagnets 1,2 each comprising a body 3,4 made of sheet metal

  laminated gnetics carrying a respective supply coil 5.6. The faces

  electromagnets 1,2 turned towards each other, define between them a

  trefer 7 with a value corresponding to the lifting of a pallet 8 made of ma-

  magnetic attached to one end of a rod 9 for actuating a valve 10 of

internal combustion engine.

  The rod 9 passes through the body 4 of one of the electromagnets 2 between which

  and a housing 12 formed in the cylinder head wall C of an engine, are available

  sés two antagonistic springs 13,14 of energy storage surrounding the rod

  drive 9 and the tail 15 of the valve to be actuated.

  The spring 13 is supported on the one hand on the body 4 of the electromagnet 2 and on the other hand, on a connecting piece 16 of the rod 9 with the stem 15 of the valve 10. The spring 14 is supported between said connecting piece 16 and the bottom of the housing 12 formed in the wall of the cylinder head C.

  According to the invention, the bodies 3 and 4 of the electromagnets 1 and 2 comprise

  each tent two pole pieces 18,19,20,21 between which are inserted respective permanent magnets 22,23. The power coils 5,6 are wound around the branches

  pole pieces 18,19,20,21 between which the magnets are interposed

employees 22.23.

  The pole pieces 18 to 21 respectively have branches

  24,25,26,27 which define two by two, the air gap 7 in which is mounted

  can be placed on the actuator pallet 8.

  The addition of a magnet in series in the magnetic circuit of each

  coil 5,6, allows, when the valve is in closed or open position, to

  apply a significant permanent holding force without consuming

current.

  Sa being the section of a magnet and Se being the section of the air gap, the

  reading of a Sa section greater than Se amplifies the field created by the permanent magnet. We can use a ferrite magnet if desired

relatively inexpensive.

  The thickness of the magnet measured in the direction of its magnetization is in principle fairly reduced so that the coils 5 and 6 remain effective for the

steering of the system.

  According to a variant not shown, a magnet is only placed in

  the most used closing solenoid.

  During the approach phase of a stop, we also benefit

  of the strength of the corresponding magnet.

  For takeoff, it is the opposite, because you have to apply a current

  negative to reduce or cancel the field created by the corresponding magnet.

  FIG. 4 shows a graph of the force F1 which it is possible to obtain as a function of the air gap between an electromagnet and the movable pallet for a non-polarized electromagnet and a polarized electromagnet according to the invention. The solid curve represents the variation of the force as a function

  of the air gap for a polarized electromagnet, that is to say provided with a per-

  manent while the dotted curve represents the variation of the force in

  function of the air gap for a non-polarized electromagnet.

  The force exerted on the plate by the electromagnet is given by the relation: F Se 2Ao 2e + S Sa) with J = magnetization of the magnet Sa = Section of the magnet Se = Section of the air gap la = width of the magnet / thickness S = Section of the plate to which the force applies e = air gap To attract the plate or pallet, the force at a long distance, that is to say for a large air gap, is greater. The control zone is therefore Se la-- Sa

more extensive.

  For air gaps smaller than one millimeter, the polarized actuator is

  less sensitive to saturation and therefore easier to control.

  The control of the force by the current is much easier because it

varies in (Bala + po.nl) 2.

  In this relation: - Ba = field created by the permanent magnet, - la = width of the magnet,

  - n = number of turns of the supply coil.

  When I is not too large, a variation dl results in a varia-

  linear tion of the force in 2.Ba.la.po.n.dl.

  Similarly, instead of being proportional to -, e being the air gap, the i

  force varies in, Se = section of the air gap, Sa = section of the magnet.

(e + la) 2S 2Sa

  The sensitivity to the air gap is therefore very low.

  The polarized actuator is much more easily controllable and must allow

  to reach very low impact speeds much more easily.

  The useful power of a polarized actuator compared to its volume

  can be multiplied by a factor equal to at least 2 with respect to that of an ac-

non polarized holder.

  With regard to electricity consumption, the efficiency of the ac-

  polarized actuator is greatly improved compared to that of a non-polarized actuator. Consumption is easily reduced from 30% to 6000 rpm and from 60% to

  1500 rpm due to the lack of maintenance consumption.

  The polarized actuator has a footprint roughly close to

  that of an actuator without a permanent magnet in its magnetic circuit.

  The actuator partially shown in FIG. la, comprises two electromagnets such as the electromagnet 1 a respectively comprising bodies

  such as 2a in magnetic sheet, turned towards each other each carrying a box

  power supply such as the coil 3a. A magnetic pallet 8a is mounted

  movable between the magnetic sheet bodies of the electromagnets.

  The supply coil such as the coil 3a is carried by a central branch 9a of the body 2a which further comprises two lateral branches 10a, 11a. In the central branch 9a is placed a permanent magnet 12a. The second electromagnet of this actuator variant is similar to that described in

  reference to FIG. 1a and the rest of the actuator is similar to that of FIG. 1.

  The electromagnetic actuator shown in FIG. 2 is of the type also comprising two electromagnets 30, 31 the respective bodies 32, 33 of magnetic material, for example of laminated sheet, are each provided

a supply coil 34.35.

  The electromagnets 30,31 each mounted on end holding pieces 36,37 in non-magnetic material, define between them an air gap 38 whose value corresponds to the lifting of a pallet or magnetic plate 39 carried by a rod 40 of driving a valve 41. The rod 40 passes through the

  body 32.33 of the electromagnets 30.31 as well as the retaining parts of the

  mite 36.37 which each have a blind sleeve 42.43 external threaded-

  ment and containing a corresponding spring 44,45 for energy storage.

  Each spring 44,45 is supported on the one hand, against the bottom of the man-

  blind cap 42.43 corresponding and on the other hand, on a disc 46.47 in contact by its face opposite the spring with a corresponding end of the rod 40

valve drive 41.

  The valve 41 has a stem 49 which bears on the face of the disc 47 opposite the rod 40, which is surrounded by the spring 45 and which passes through the bottom of the blind sleeve 43, the head 50 of said valve cooperating with a

  valve seat of an engine cylinder head (not shown).

  As in the embodiment of FIG. 1, each of the magnetic bodies 32,33 of the electromagnets 30,31, comprises two pole pieces

  51.52.53.54 respectively, between which are arranged permanent magnets

  nents 55.56 whose function is similar to that of permanent magnets 22.23

  of the embodiment of FIG. 1.

  It can be seen that the directions of the magnetizations of the permanent magnets 55, 56 are parallel to the fields generated by the actuating coils.

  34.35 carried by the bodies 32.33 of the electromagnets 30.31.

  The electromagnetic actuator shown schematically in Figure

  gure 3 comprises two electromagnets 60, 61 of which the bodies made of magneti-

  that for example in laminated sheets, each carry a supply coil

63.64.

  The body of each electromagnet has two pole pieces

  , 66 and 67.68 joined together by a respective permanent magnet 69.70 in-

  rotated by the corresponding supply coil 63.64.

  Each of the permanent magnets 69.70 is mounted in a branch

  corresponding central unit 71.72 formed by corresponding portions of the parts

  these polar 65.66 and 67.68. It is placed in the central branch of its circuit

  tilted magnetic, so that its magnetization is tilted relative

  port to the electromagnetic field generated by the supply coil 63, 64

  corresponding and thus combines with the latter.

  The angle of inclination of the magnetic field of each permanent magnet

  nent 69.70 relative to the field generated by the corresponding coil 63.64, is advantageously chosen so that the end of its inner longitudinal side furthest from the lateral branches of the pole pieces 65,66,67,68

  is at a distance d from these branches equal to the width of these.

  The mounting of each permanent magnet 69.70 in the body of

  the corresponding electromagnet is produced by cutting the sheets of the polar parts

  res 65.66 and 67.68 so as to form between the pole pieces 65.66 on the one hand

  and 67.68 on the other hand, housings receiving the respective magnets 69.70.

  The faces of the electromagnets 60,61 facing one another, defined

  feels between them an air gap 74 of a value corresponding to the lifting of a part

  lette 75 of a magnetic material fixed to one end of an action rod 76-

  valve 77 of an internal combustion engine.

  As in the embodiment shown in Figure 1, the rod 76 passes through the body of the electromagnet 61 between which and a housing 78 formed in the wall of the cylinder head C of an engine, are arranged two springs 79.80 of

  energy storage surrounding the drive rod 76 and the tail 81 of the support

pope to operate.

  The function of a magnet in series in the magnetic circuit of each coil 63,64, ensures in the embodiment of Figure 3, the same effect

  than in the previous embodiments.

  In addition, the fact of inclining the magnets 69.70 relative to the direction of the fields generated by the supply coils 63.64, makes it possible to reduce

  considerably the height of the magnetic circuits of the electromagnets 60,61.

  We can thus reduce the overall size of the actuator in particular with regard to its overall height, which facilitates its

  installation on the cylinder head of an internal combustion engine.

  The arrangement which has just been described presents with respect to the state of the

technical, the following advantages.

  It allows better control of the valve thanks to the relative linearity

  force as a function of the air gap, which makes it possible to obtain a gain in noise.

  The power consumption of holding the valve in position is

none or very limited.

  Switching power consumption is reduced by reduction

losses by the Joule effect.

  The polarized actuator is generally more powerful and therefore better suited for use on exhaust valves or on a combustion engine.

lower unit displacement.

Claims (7)

  1. Electromagnetic actuator of an internal combustion engine valve comprising two electromagnets (1,2; 30,31; 60,61) each comprising a supply coil (5,6; 34,35; 63,64), a pallet magnetic (8; 39; 75) disposed between the two electromagnets, linked to a drive member (9; 40; 76) of the valve against the action of at least one spring (13,14; 44.45; 79.80) for switching energy storage of said valve   (10; 41; 77), characterized in that in the magnetic body of at least one elect   a permanent magnet (22.23; 55.56; 69.70) is interposed, the magnet of which   tion combines with the field generated in said body by the supply coil (5,6; 34,35; 63,64).   2. An electromagnetic actuator according to claim 1, in which the magnetic bodies of the two electromagnets (1,2; 30,31) define between them a gap (7; 38; 74) in which said pallet (8; 39; 75) is mounted displaceable against at least one opposing spring (13,14; 44,45; 79, 80) for storing switching energy, characterized in that a permanent magnet (22,23; 55,56) is interposed in the magnetic body of each electromagnet (1,2; 30,31; 60,61).   3. Electromagnetic actuator according to claim 2, characterized   in that the permanent magnet is interposed in the magnetic body of the elect closing magnet.   4. Electromagnetic actuator according to one of claims 1 to   3, characterized in that the body of each electromagnet (1,2; 30,31; 60, 61) comprises two pole pieces (18,19,20,21; 51,52,53,54; 65,66,67 , 68), a permanent magnet (22,23; 55,56; 69,70) being interposed between the two pole pieces of the body of each electromagnet.   5. Actuator according to one of claims 1 to 4, characterized in that   that the permanent magnet is arranged in the body of the electromagnet so that the magnetization of the permanent magnet (22,23; 34,35) is parallel to the field   generated in said body by the supply coil (5,6; 34,35) corresponding ponding.   6. Actuator according to one of claims 1 to 4, characterized in that   that the permanent magnet is arranged in the body of the electromagnet so that the magnetization of the permanent magnet (69,70) is inclined relative to the   field generated in said body by the supply coil (63,64) corresponding ponding.   7. Actuator according to one of claims 1 to 3, characterized in that   that the body (2a) of each electromagnet has a central branch (9a) and two lateral branches (10a, 11a), the supply coil (3a), is arranged around the central branch and the permanent magnet (12a) is placed in said central branch of the body (2a).