EP1174595B1 - Valve actuator for internal combustion engine - 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 formed a gap.

In the air gap is mounted a magnetic pallet connected 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 required for rapid switching is ensured by the springs and the change of position is controlled by means of the electromagnets.

This system is simple in appearance, but it has technical limitations.

The control of the position of the valve 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 uncontrollable by the current.

Excluding saturation, this force is proportional to the square of the current injected into the coils and inversely proportional to the square of the gap.

This double non linearity makes very difficult the control of the valve by the 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 small, which decreases the range of use and poses a problem with regard to the initialization of the actuator.

At the intermediate distance between 1 and 3 mm, the force is difficult to control by the current because of the aforementioned quadratic dependence.

At a short distance, when the valve approaches its seat for example, the force increases very rapidly, practically without any control by the current. There is a runaway effect responsible for impact noise. This phenomenon is quite comparable to the slam produced by the electromagnet of a closet door.

The force exerted on the pallet is always positive because of its proportionality to the square of the supply current of the coils.

Therefore, the valve can not be slowed down if too much speed is detected.

To this problem relating to the force is added the important presence of eddy currents, which attenuate and delay the effect of the coils.

In order to overcome these drawbacks, up to now it was necessary to make the valve control device more complex, by means of high-performance sensors for position of the valve, of a precise and fast control electronics, a sophisticated software strategy and possibly using a mechanical damper.

Despite these increases in the complexity of the control and control means, the expected performance in terms of impact speed may remain insufficient requiring the implementation of additional means of sound insulation.

At the intake, the actuator must be able to provide the necessary energy for switching. This is to compensate for friction losses that amount to about 0.2 J for a stroke or 8 mm lift of the valve, and therefore the range of electromagnets.

The energy provided by an electromagnet over the whole of the aforementioned race is equal to the integral of the force.

This energy is relatively weak because of the strong decrease of the force for the great values of gap.

For example, at a speed of rotation of the engine 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. , of the order of 1 kg and its fat.volume.

For an engine of 500 cm ³ , of cubic capacity, one can be satisfied with such dimensions although they remain a handicap.

On the other hand, these dimensions are not compatible with smaller unit displacements.

At the exhaust, the energy to be supplied is of the order of 1.4 J to fight against the pressure in the cylinder chamber during the opening of the valve.

Current actuators have a relatively high height due to the stacking of springs, two electromagnets and an actuating plate or pallet.

In parking, on the engines of current vehicles, there is always a cylinder in compression.

The engine thus provides a complementary parking brake that some users use as an additional brake to the parking brake, especially in the ribs.

When the electromagnetic actuators are used, the valves are in 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 because of its simplicity, but the associated control electronics as well as the valve position sensor, are complex and therefore expensive.

The invention aims to overcome the disadvantages of conventional solenoid valve actuators by creating an actuator, which while at a relatively low cost, has improved performance in all of the areas mentioned above.

The invention relates to an improvement to the electromagnetic valve actuator of an internal combustion engine known from the patent application. EP-1010866A , the known elements of which are incorporated in the preamble of claim 1, this improvement being that the body of each electromagnet comprises a central branch and two lateral branches, in that the supply coil is arranged around the central branch and in that the permanent magnet is placed in said central branch of the body.

• les corps magnétiques des deux électroaimants définissant entre eux un entrefer dans lequel ladite palette est montée déplaçable à l'encontre d'au moins un ressort antagoniste de stockage d'énergie de commutation, un aimant permanent est interposé dans le corps magnétique de chaque électroaimant ;
• l'aimant permanent est interposé dans le corps magnétique de l'électroaimant du haut ;
• l'aimant permanent est disposé dans le corps de l'électroaimant de manière que l'aimantation de l'aimant permanent soit parallèle au champ engendré dans ledit corps par la bobine d'alimentation correspondante ;

According to other characteristics:

• the magnetic bodies of the two electromagnets defining between them an air gap in which said pallet is mounted displaceable against at least one switching energy storage counteracting spring, a permanent magnet is interposed in the magnetic body of each electromagnet;
• the permanent magnet is interposed in the magnetic body of the upper electromagnet;
• the permanent magnet is disposed in the body of the electromagnet so that the magnetization of the permanent magnet is parallel to the field generated in said body by the corresponding supply coil;

• la Fig.1 est une vue schématique d'un actionneur électromagnétique à deux électroaimants suivant l'invention ;
• la Fig.1a est une vue schématique partielle d'un actionneur suivant l'invention;
• la Fig.2 est une vue schématique en coupe d'un autre actionneur électromagnétique de soupape à deux électroaimants suivant l'invention ;
• la Fig.3 est une vue schématique en coupe d'encore un actionneur électromagnétique de soupape, et
• la Fig.4 est un graphique comparatif de la force exercée sur la palette d'un actionneur pourvu ou non d'un aimant permanent.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

• the Fig.1 is a schematic view of an electromagnetic actuator with two electromagnets according to the invention;
• the D.1a is a partial schematic view of an actuator according to the invention;
• the Fig.2 is a schematic sectional view of another electromagnetic valve actuator with two electromagnets according to the invention;
• the Fig.3 is a schematic sectional view of yet another electromagnetic valve actuator, and
• the Fig.4 is a comparative graph of the force exerted on the pallet of an actuator provided or not with a permanent magnet.

The electromagnetic valve actuator shown in FIG. figure 1 , comprises two electromagnets 1,2 each comprising a body 3,4 laminated magnetic sheet carrying a respective supply coil 5,6. The faces of the electromagnets 1, 2 turned towards each other, define between them an air gap 7 of a value corresponding to the lifting of a pallet 8 of magnetic material attached to one end of an actuating rod 9 a valve 10 of an 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 wall C of a motor, are arranged two energy storage 13,14 antagonistic springs surrounding the drive rod 9 and the tail 15 of the valve to be actuated.

• Suivant l'invention, les corps 3 et 4 des électroaimants 1 et 2 comportent chacun deux pièces polaires 18,19,20,21 entre lesquelles sont insérés des aimants permanents respectifs 22,23.

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 tail 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 each comprise two pole pieces 18, 19, 20, 21, between which permanent magnets 22, 23 are inserted.

The supply coils 5,6 are wound around the branches of the pole pieces 18,19,20,21 between which are interposed the respective magnets 22,23.

The pole pieces 18 to 21 respectively comprise branches 24,25,26,27which define in pairs, the air gap 7 in which is mounted displaceable pallet 8 of the actuator.

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 have a large permanent holding force without power consumption.

Sa being the section of a magnet and Se being the section of the air gap, the use of a section Sa greater than Se allows to amplify the field created by the permanent magnet. Thus a relatively inexpensive ferrite magnet can be used if desired.

The thickness of the magnet measured in the direction of its magnetization, is in principle quite reduced so that the coils 5 and 6 remain effective for controlling the system.

According to a variant not shown, a magnet is placed only in the closing electromagnet which is the most used.

During the approach phase of a stop, one also benefits from the strength of the corresponding magnet.

For takeoff, it's the opposite, because you have to apply a negative current to reduce or cancel the field created by the corresponding magnet.

On the figure 4 a graph of the force F ₁ that can be obtained as a function of the air gap e1 between an electromagnet and the mobile pallet for a non-polarized electromagnet and a polarized electromagnet according to the invention is shown.

The curve in solid line represents the variation of the force as a function of the gap for a polarized electromagnet, ie provided with a permanent magnet while the dashed line represents the variation of the force as a function of the gap for a non-polarized electromagnet.

• avec J = aimantation de l'aimant
• Sa = Section de l'aimant
• Se = Section de l'entrefer
• la = largeur de l'aimant / épaisseur
• S = Section du plateau sur laquelle s'applique la force
• e = entrefer

The force exerted on the plate by the electromagnet is given by the relation: $$F_S=\frac{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="imgf0001.png"\; state="\{\{state\}\}">S</figure-callout>}}{2{\mu }_o}{\left(\frac{\mathit{Jla}+{\mu }_o\mathit{or}}{2e+\mathit{the}\frac{\mathit{himself}}{\mathit{Her}}}\right)}^2$$

• with J = magnetization of the magnet
• Sa = Section of the magnet
• Se = Section of the air gap
• the = width of the magnet / thickness
• S = Plateau section on which force is applied
• e = gap

plus étendue.To attract the plate or pallet, the force at great distance, ie for a large air gap, is more important. The control zone is therefore $$\mathit{the}\frac{\mathit{himself}}{\mathit{Her}}\mathrm{.}$$

more extensive.

For gaps smaller than a 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 + μ ₀ .nl) ² .

• Ba = champ créé par l'aimant permanent,
• la = largeur de l'aimant,
• n = nombre de spires de la bobine d'alimentation.

In this relationship:

• Ba = field created by the permanent magnet,
• the = width of the magnet,
• n = number of turns of the supply coil.

When l is not too big, a variation dl results in a linear variation of the force in 2.Ba.la.μ ₀ .n.dl

e étant l'entrefer, la force varie $\frac{1}{{\left(e+\mathit{la}\frac{\mathit{Se}}{2\mathit{Sa}}\right)}^2},$

Se = section de l'entrefer, Sa = section de l'aimant.Similarly, instead of being proportional to $\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="imgf0001.png"\; state="\{\{state\}\}">e</figure-callout>}}^2},$

e being the air gap, the force varies $\frac{1}{{\left(e+\mathit{the}\frac{\mathit{himself}}{2\mathit{Her}}\right)}^2},$

Se = section of the gap, Sa = section of the magnet.

The sensitivity to the gap is very small.

The polarized actuator is much more easily controllable and must achieve much more easily impact speeds very low.

The effective power of a polarized actuator relative to its volume can be multiplied by a factor equal to at least 2 vis-à-vis that of a non-polarized actuator.

With respect to power consumption, the efficiency of the polarized actuator is greatly improved over that of an unpolarized actuator.

The consumption is easily reduced by 30% at 6000 rpm and 60% at 1500 rpm due to the absence of maintenance consumption.

The polarized actuator has a size roughly similar to that of an actuator devoid of permanent magnet in its magnetic circuit.

The actuator according to the invention partially represented in the Fig. 1a , comprises two electromagnets such as the electromagnet 1a respectively comprising bodies such as 2a made of magnetic sheet, turned towards each other each carrying a supply coil such as the coil 3a. A magnetic paddle 8a is movably mounted 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 with reference to the figure 1 a and the rest of the actuator is similar to that of the Fig. 1 .

The electromagnetic actuator shown in figure 2 , is of the type also comprising two electromagnets 30,31 whose respective bodies 32,33 of magnetic material, for example of laminated sheet, are each provided with a supply coil 34,35.

The electromagnets 30, 31, each mounted on end holding pieces 36, 37 of 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. driving a valve 41. The rod 40 passes through the bodies 32,33 of the electromagnets 30,31 and the end holding pieces 36,37 which each comprise a blind sleeve 42,43 externally threaded and containing a spring 44, 45 corresponding energy storage.

Each spring 44,45 is supported on the one hand, against the bottom of the corresponding blind sleeve 42,43 and on the other hand, on a disk 46,47 in contact with its face opposite the spring with a corresponding end of the rod 40 driving the valve 41.

The valve 41 has a shank 49 which bears against the face of the disk 47 opposite to 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 seat of valve of a motor cylinder head (not shown).

As in the figure 1 each magnetic body 32,33 of the electromagnets 30,31 comprises two pole pieces 51,52,53,54 respectively, between which are disposed permanent magnets 55,56 whose function is similar to those of the permanent magnets 22,23 of the embodiment of the figure 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 at the figure 3 comprises two electromagnets 60, 61 whose bodies made of magnetic material, for example laminated sheets, each carry a supply coil 63, 64.

The body of each electromagnet comprises two pole pieces 65,66 and 67,68 joined together by a respective permanent magnet 69,70 surrounded by the corresponding supply coil 63,64.

Each of the permanent magnets 69,70 is mounted in a corresponding central branch 71,72 formed by corresponding portions of the pole pieces 65,66 and 67,68. It is disposed in the central branch of its magnetic circuit in an inclined manner, so that its magnetization is inclined relative to the electromagnetic field generated by the corresponding supply coil 63,64 and thus combines with the latter.

The angle of inclination of the magnetic field of each permanent magnet 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 away from the lateral branches of the pole pieces 65,66,67,68 is at a distance d from these branches equal to the width thereof.

The mounting of each permanent magnet 69,70 in the body of the corresponding electromagnet is achieved by cutting the plates of the pole pieces 65,66 and 67,68 so as to form between the pole pieces 65,66 and 67 , 68 on the other hand, housings receiving the magnets 69,70 respective.

The faces of the electromagnets 60,61 facing towards each other, define between them an air gap 74 of a value corresponding to the lifting of a pallet 75 made of a magnetic material attached to one end of a rod 76 of actuation of an internal combustion engine valve 77.

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 valve to be actuated.

The function of a magnet in series in the magnetic circuit of each coil 63,64, ensures in the embodiment of the figure 3 the same effect as in the previous embodiments.

Furthermore, tilting the magnets 69, 70 relative to the direction of the fields generated by the supply coils 63, 64 makes it possible to considerably reduce the height of the magnetic circuits of the electromagnets 60, 61.

It is thus possible to reduce the overall size of the actuator, particularly with regard to its overall height, which facilitates its installation on the cylinder head of an internal combustion engine.

The arrangement shown partially in Fig. 1a which has just been described presents with respect to the state of the art, the following advantages.

It allows a better control of the valve thanks to the relative linearity of the force according to the air gap, which makes it possible to obtain a gain in noise.

The electrical consumption of holding the valve in position is zero or very limited.

Switching power consumption is reduced by reducing Joule losses.

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

Claims (4)

1. Electromagnetic actuator for internal combustion engine valves comprising two electromagnets each having a power supply coil (3a), a magnetic paddle (8a) positioned between the two electromagnets, connected to a member driving the valve against the action of at least one energy-storage spring for switching over said valve, a permanent magnet (12a) whose magnetization is combined with the field generated in said body by the power supply coil (3a) being inserted into the magnetic body (2a) of at least one electromagnet, characterized in that the body (2a) of the electromagnet comprises a central branch (9a) and two lateral branches (10a, 11a), the power supply coil (3a) being positioned around the central branch and the permanent magnet (12a) being placed in said central branch of the body (2a).
2. Electromagnetic actuator according to Claim 1, of which the magnetic bodies of the two electromagnets define between them an air gap in which said paddle is mounted to move against at least one opposing switching energy storage spring, characterized in that a permanent magnet (12a) is inserted into the magnetic body of each electromagnet.
3. Electromagnetic actuator according to Claim 1, characterized in that the permanent magnet is inserted into the magnetic body of the closing electromagnet.
4. Actuator according to any one of the preceding claims, characterized in that the permanent magnet is positioned in the body of the electromagnet so that the magnetization of the permanent magnet (12a) is parallel to the field generated in said body by the corresponding power supply coil (3a).

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