EP1122748B1 - Device controlling and reducing the speed of impact of an electromechanical actuator - Google Patents

Abstract

The electromagnetic driver impact reduction mechanism has a rod driving a plane (10) moving in a gap (11) with electro magnets (12,13) on each side. The electromagnets have an elastic stop fixed to them which deadens the movement towards the magnets.

Description

The present invention relates to a device for controlling and reducing the impact speed of an electromechanical actuator against stop stops of the member controlled by it and more particularly applies, although not exclusively, to the control of the valves of an internal combustion engine.

As known in the art, it is known to operate the valves of a vehicle engine by means of a mechanical assembly of the type usually referred to as a camshaft, the rotation of which controls the movement of these valves to cause their relative displacement vis-à-vis their seat, opening or closing, to achieve the admission and / or escape of the combustion products in the cylinders of the engine.

To obtain a variable adjustment of the angles, that is to say the opening and closing times of each valve depending on the conditions of use of the engine, in particular to optimize the energy efficiency thereof, it is also known to use, in a more sophisticated manner, an electromagnetic assembly associated with each valve stem.

Summarily to its essential elements, this assembly comprises, associated with the valve stem, two windings electromagnetic neighbors but separated by an air gap whose distance is substantially equal to the stroke of the valve head, the rod being secured to a transverse plate of magnetic material, housed in the air gap between the two windings, so that, according to the direction of the current which crosses alternatively these, this plate is attracted by one or the other, so that the valve passes from its open position to that of its closure, the swash plate of part and of other of a position of intermediate equilibrium.

The valve stem is associated with springs respectively working and simultaneously in compression and extension or vice versa as appropriate, particularly in the direction of movement of the valve stem towards one or the other of the two windings, on opening or closing, the effect of these springs adding to that of the electromagnetic attraction force exerted on the transverse plate, created alternately by the windings.

By adjusting the intensity of the current in the two windings, it is thus possible, in a simple manner, to adjust the speed of the valve stem in its stroke and to vary it as needed.

The Figures 1a, 1b and 1c schematically illustrate a known device of this kind.

In these figures, which show in elevation the aforementioned control device, the reference 1 designates a rod illustrated in a vertical position which comprises at its lower end a valve head 2 and at its opposite end a bearing surface 3 for a spring 4 mounted between this seat and a fixed stop 5.

The rod 1 comprises on the side of the valve head 2 another bearing surface 6 for a second spring 7, mounted between this range and a fixed guide 8 having a through bore 9 in which slides, in a reciprocating motion, the corresponding end of the rod 1.

This rod is also equipped, between the bearing surfaces 3 and 6 of the springs 4 and 7, with a transverse plate 10 which, if the rod is vertical, extends horizontally, this plate being mounted in a gap 11 arranged between two electromagnets, respectively 12 and 13, each of these electromagnets comprising a yoke 14 of magnetic material and an electric winding 15, so that the passage of a current in the windings of the two electromagnets causes on the plate 10 an effect of attraction by one of these electromagnets and repulsion by the other, the valve head 2 thus oscillating between two positions where the plate is in contact with one or the other of the electromagnets.

The Figure 1a illustrates the equilibrium position of the assembly thus envisaged, in which the plate 10 is substantially in the middle of the gap 11 between the two electromagnets 12 and 13, the Figure 1b representing the position where this plate has moved to be in contact with the electromagnet 12 and the Figure 1c the one where, conversely, the plate is applied against the electromagnet 13.

During the movements of the plate 10, on either side of its intermediate equilibrium position, the springs 4 and 7 are respectively contracted or stretched, or conversely, the two positions reached by the valve head, represented on the Figures 1b and 1c , corresponding for the first to that where the valve is supposed to be closed by applying to a seat (not shown) and for the second to that where the valve is open.

The operation of such an actuator assembly is relatively simple, the means necessary to oscillate the plate 10 carried by the rod 1 on either side of its equilibrium position does not present major difficulties to be achieved industrially.

However, this set has disadvantages. Indeed, when the plate 10 is released from the position illustrated on the Figure 1b , that is to say in the closed position of the valve 2, the springs 4 and 7 must ensure the displacement of the rod to the opposite position of the plate, represented on the Figure 1c , this to the friction near the rod in the bore 9 of the guide 8.

The electromagnet 13 is then energized to generate a force to compensate for friction and bring the plate 10 into its final position, valve 2 open.

When the plate 10 is in abutment, a weaker current still passes through the winding of the electromagnet to ensure a sufficient force to maintain the parts in this position, this current being then cut to allow the valve stem to reverse its movement, according to a symmetrical displacement of the previous one.

However, the non-reproducibility of the friction during use of such an electromechanical actuator, in an internal combustion engine in particular, related to the variable temperature of the assembly and in particular of the oil in which the corresponding parts are immersed, oil, the quantity of which may vary, as well as manufacturing tolerances, makes it necessary to oversize the force produced by each of the two electromagnets in turn to ensure the safe movement of the plate to one or other of these two positions, the valve head being suitably brought into the open or closed position.

As a result, the plate is accelerated at the end of the stroke, its speed at the time of the final impact on the electromagnet when the valve opens or closes being relatively high, of the order of 1 m / sec. This results in a not inconsiderable noise during engine operation.

To overcome this drawback and reduce the noise thus created without changing the speed of impact, various solutions have already been proposed.

A first possibility is to soundproof the mechanical environment of the actuator to reduce the transmission of noise to the outside of the engine hood, this solution does not act on the cause of the problem, while weighing down the vehicle.

A different solution in principle is to reduce the effort created by each of the electromagnets, in particular to adjust this effort to the value just needed to produce a reduction of the plateau acceleration at the end of the race. This solution is illustrated in particular in the documents of DE-A-19623698 , DE-C-19735375 , US Patent 5769043 and EP-B-0662697 .

This solution is effective but difficult to implement and above all very expensive. It requires a sensor to know precisely the position of the plate at each moment and a microprocessor that calculates and continuously adjusts the current in the winding of the electromagnet. The environment of the sensor, because of temperature and vibrations, poses problems for obtaining a reliable and sufficiently fast measurement, which complicates the achievement of the servocontrol by increasing unacceptably the necessary computing power.

A last solution is to increase the resistance resisting the movement of the plateau at the end of its movements towards one or the other of the two electromagnets, in order to decrease its acceleration and to reduce the speed of impact of this plate.

For this purpose, complementary electromagnetic coils can be used to create a resisting force acting in the opposite direction to that which causes the attraction of the plate. This solution is complex and expensive because it requires additional windings, creating congestion problems for the actuator and an increase in the power consumption for the vehicle (see for example DE-U-29615396 , US Patent 5730091 or WO-A-9810175 ).

It is also possible to use a damping device of the type in particular hydraulic stop, which requires complementary parts in motion and a special supply of oil, the stop increasing the magnetic forces to be produced during the phase when the valve head remains in the open position or before reversing its movement (see for example DE-A-19646938 ).

Similarly, the use of an additional spring, able to produce a force only during the last part of the displacement, if it is simpler mechanically, has the disadvantage of increasing the forces proportionally to the position of the plateau, so that they are the highest when the plateau is in the final position, the power consumption is increased very significantly.

The present invention relates to a device for controlling and limiting the end-of-stroke impact velocity of an actuator of the aforementioned type, which is similar to the last solutions mentioned above, allowing an increase in the resisting force exerted on the plate carried by the stem of the valve in the application more especially considered, this increased effort being created during only a portion of the movement of the actuator, in order to reduce its speed just before the moment it reaches one or the other of its final positions, when opening or closing the head of the valve.

The DE-A-19646937 illustrates a similar device in which the swash plate carried by the valve stem comprises abutments of an elastomeric material, mounted such that these stops are partially projecting out of the apparent contour of the plate, in the direction respectively of one and the other of the two electromagnets and in particular of the rigid yoke of these last ones.

Therefore, these resilient abutments housed, according to the cited earlier patent, in open and parallel grooves formed opposite one another in the opposite faces of the plate, come into contact with the ends of the yoke of the electromagnets. and provide effective damping of the movement of the rod at the end of the race.

However, this solution still has drawbacks, despite its simplicity.

Indeed, from the moment when the elastic stops are mounted in grooves dug in the plate, this results in a reduction of the "iron section" at this location, that is to say, the section of metal to through which the lines of the magnetic field created by the corresponding electromagnet pass.

In particular, these field lines have only a narrow passage at the stops, in the section of the plate which separates the two opposite grooves receiving these stops in one and the other of the faces thereof. Therefore, to maintain good performance, it is necessary to use a larger current through the coil of each of the two electromagnets or to oversize these coils, which is penalizing.

Note that a possible solution could be in this case, not to reduce the iron section, to eliminate the grooves and stick or otherwise fix the stops on the opposite surfaces of the plate; however, in this case, the latter would be significantly increased, resulting in the same constraints as those mentioned above.

The present invention relates to an improvement made to the production of resilient stops for damping the impact of the end-of-travel tray on the yokes of the two electromagnets, which eliminates the last aforementioned drawbacks.

For this purpose, the device for controlling and reducing the impact speed of an actuator, comprising a control rod subjected to a displacement back and forth along its axis, this rod being secured to a transverse plate having two opposed faces extending substantially perpendicularly to the rod and moving in a gap delimited by at least one electromagnet alternately attracting the plate in combination with a force created by opposing springs acting on the rod, the plate moving oscillatingly from of a position of intermediate equilibrium between two final positions in which it comes into contact with an electromagnet, is characterized in that, at least one of the electromagnets comprises, facing the transverse plate integral with the rod, at least one elastic stop attached to the electromagnet and against which the plate comes into contact at the end of the race to slow it in its movement.

Most often, two opposing electromagnets are used. However, there are known systems using only one electromagnet, the movement oscillation being obtained by a particular geometry of its frame.

The solution thus proposed thus involves one and preferably two elastic stops, that is to say one for each direction of movement of the valve, which are here directly associated, not to the transverse plate itself - which avoids any particular machining thereof for the mounting of the stops - but actuator electromagnets actuator, these abutments, because of their crushing, being arranged to increase the resisting force which opposes the movements of the transverse plate carried by the rod in order to reduce the speed of this plate end of stroke when approaching one or other of its final positions, the opening or closing of the valve.

In a preferred embodiment of the invention, each electromagnet comprises a metal yoke comprising an axial central armature on which is mounted the winding of an electric coil whose turns extend in a plane perpendicular to the armature, the stop being made integral with the coil in the face thereof which is opposite the transverse plate.

Preferably, the yoke of each electromagnet has, in cross section, the shape of a "m", the median leg of which constitutes the central armature, the coil mounted around this armature being surrounded externally by an external carcass parallel to the armature. central armature and connected thereto by a flat end armature extending perpendicularly to the central armature against the face of the coil opposite that which carries the elastic stop, housed between the central armature and the peripheral carcass .

Also preferably, the elastic stop has a height such that, before contact with the plateau transversely, it slightly exceeds the support plane thereof, a distance that sizing the resisting force slowing the speed of the plateau at the end of the race.

According to a particular characteristic of the invention, the elastic stop is made in the form of one or more continuous strips of an elastomeric material.

Alternatively, the stop is formed of a plurality of separate pads, preferably regularly distributed over the surface of the coil around the central frame. Depending on the case, the separated pads may have a cylindrical profile, in regular hyperboloid or truncated cone in their anchoring zones on the electrical coil, extended by a cylindrical portion projecting externally. Other particular forms for the elastic stops could likewise be envisaged without departing from the scope of the present invention.

Depending on the case, the elastic stop is made of an elastomeric material, of the natural rubber or silicone type, suitable for generating under the progressive crushing force thereof due to the displacement of the transverse plate at the end of the stroke, a resistant force , partly proportional to the position and partly proportional to the speed of the plate, the latter component automatically disappearing in the final position of the plate when it applies and "sticks" on the yoke of the electromagnet.

In a also preferred embodiment, the coil of each electromagnet comprises an electrical winding embedded in an insulating resin, the stop being anchored and bonded to the coil via this resin.

In particular and as the case may be, it is possible to pour the resin around the electrical winding of the coil before setting up the abutment or, conversely, arrange the abutment on the winding and then pour the resin.

• La Figure 2 illustre schématiquement les deux électroaimants de l'actionneur et le plateau transversal oscillant entre eux, avec les butées élastiques contre les bobines de ces électroaimants, avant impact du plateau.
• La Figure 3 représente un des électroaimants de la Figure 2 lorsque le plateau transversal est en fin de course, la butée élastique correspondante étant écrasée entre la bobine et ce plateau.
• Les Figures 4a à 4c illustrent diverses variantes de réalisation et de montage des butées élastiques.

Other characteristics of a device established in accordance with the invention will become apparent from the following description of several exemplary embodiments, given by way of non-limiting indication, with reference to the appended drawings in which:

• The Figure 2 schematically illustrates the two electromagnets of the actuator and the transverse plate oscillating between them, with the elastic stops against the coils of these electromagnets, before impact of the plate.
• The Figure 3 represents one of the electromagnets of the Figure 2 when the transverse plate is at the end of travel, the corresponding elastic stop being crushed between the coil and this plate.
• The Figures 4a to 4c illustrate various embodiments and mounting resilient stops.

On the Figure 2 , we find the two electromagnets, respectively 12 and 13, described in relation to the Figures 1a to 1c mentioned above, these electromagnets each comprising a yoke 14 and an electric coil 15. In this figure, there is also illustrated the transverse plate 10 mounted in the gap 11 between the two electromagnets 12 and 13, this plate being shown in its position d equilibrium substantially in the equidistant position of the two electromagnets.

According to the invention, the electrical coils 15 of these electromagnets are associated with resilient stops 16 fixed against these coils in their faces which face the plate 10 oscillating in the gap 11, these stops being dimensioned so as to partially crush when the plateau, in the terminal phase its stroke, approaches the cylinder head 14 of one or the other of the two electromagnets 12 or 13 as the case, providing a resistant force which gradually reduces the impact speed.

The Figure 3 illustrates one of the preceding electromagnets, in this case the electromagnet 12, in the corresponding position where the elastic stop 16 is partially crushed by the plate 10 when it "sticks" on the yoke 14.

The yoke 14 of each electromagnet is preferably constituted by a central armature 17, surrounded by an outer casing 18, these two elements preferably made of laminated sheets, as is customary in a conventional electromagnet, being interconnected by one another. flat end armature 19, the cylinder head thus having a general profile in "m".

In this example, the yoke 14 has the general shape of a rectangular parallelepiped extending perpendicular to the plane of the Figure 2 or 3 . More specifically, the central frame 17 has the shape of a flat plate whose "slice" is seen on the Figures 2 and 3 and the carcass 18 is formed of two flat plates 18a and 18b parallel to the central armature 17.

The electric coil 15 of the electromagnet is cylindrical, housed between the central armature 17 and the peripheral casing 18, its turns extending substantially horizontally, parallel to the transverse plate 10.

The elastic abutment 16 is attached and fixed against the upper face 20 of the coil 15, which is arranged slightly recessed relative to the upper ends of the central armature 17 and the outer carcass 18, against which the plate 10 is applied. as illustrated on the Figure 3 .

In the example described here, the abutment 16 is composed of two parallel strips 16a and 16b extending perpendicularly to the plane of the Figures 2 and 3 .

According to the invention, the elastic stop 16, at rest, that is to say when the plate 10 does not produce a crushing force on it, slightly exceeds the apparent contour of the electromagnet, a distance determined by construction to size the resistant force created by this stop, to brake the transverse plate at the end of the race.

As the case may be, the elastic abutment 16 is made of an elastomer material of the rubber, natural or synthetic type, preferably of silicone rubber, enabling it to withstand the ambient conditions in which the actuator operates, in particular of temperature and atmosphere. surrounding.

The stop may be in the form of one or more continuous strips, or may consist of separate pads, preferably regularly distributed on either side of the frame.

In either case, the cross section of the abutment can be substantially square as shown on the Figures 2 and 3 , or to present a more complex form as illustrated on the Figures 4a to 4c , with a part or anchor 16c allowing its immobilization vis-à-vis the coil 15 and a free portion 16d protruding outwards, against which the plate 10 is applied by partially crushing.

Thus, the abutment 16 may have a profile substantially in the form of a hyperboloid ( Figure 4a ) or with a cone-shaped anchoring heel 16c, extended by a part outer surface 16d cylindrical ( Figures 4b and 4c ).

The turns of the electrical winding of the coil 15 are naturally insulated and preferably embedded in a resin, which can also allow immobilization of the stop 16 in the face 20 of this coil, the resin can be cast before or after the stop is put in place, the surface state of the face 20 being previously prepared to promote the bonding of the abutment, this operation being all the easier to implement as this abutment undergoes no lateral force in operation .

Thus, a device for controlling and reducing the impact speed of a very simple, inexpensive actuator whose industrialistion can be very easily controlled during the manufacture of this actuator.

The resistive force due to the stop is of viscoelastic type, so is partly proportional to the crushing and partly to the speed of the plate, so that the latter component is canceled when it reaches its final position when it is glued to the metal cylinder head of the electromagnet.

This solution has an advantage over the implementation under the same conditions of a single spring, the resisting force provided by it being this time proportional to the distance traveled under the effect of the plateau and not to the speed of this last.

Of course, it goes without saying that the invention is not limited to the embodiment more specifically described above with reference to the accompanying drawings; on the contrary, it embraces all variants. So, if the above description was made with electromagnets of rectangular shape, the invention is equally applicable to electromagnets of different shape, for example cylindrical circular section. In addition, only one stop may be used if the noise problem arises only in one direction of displacement of the valve.

Claims (11)

1. Device for controlling and reducing the impact speed of an electromechanical actuator, including a control rod (1) subjected to a back-and-forth movement along the axis thereof, this rod being integral with a transverse plate (10) having two opposite faces extending substantially perpendicular to the rod and moving in a gap (11) defined by at least one electromagnet (12, 13), including an electric coil (15), alternately attracting the plate in combination with a force created by countersprings (4, 7) acting on the rod, the plate moving in a oscillating manner from an intermediate equilibrium position between two final positions in which it enters into contact with an electromagnet, characterized in that at least one electromagnet comprises at least one elastic stop (16) fixed against the coil (15), in the face thereof that is opposite the transverse plate (10) that is integral with the rod, the plate (10) coming into contact against the elastic stop (16) at the end of travel to brake the movement of the plate.
2. Device according to Claim 1, characterized in that each electromagnet (12, 13) comprises a metal support assembly (14) including an axial central armature (17) on which is mounted the winding of an electric coil (15), the turns of which extend in a plane that is perpendicular to the armature, the stop (16) being made integral with the coil in the face thereof which is opposite the transverse plate (10).
3. Device according to one of Claims 1 or 2, characterized in that the support assembly (14) of each electromagnet (12, 13) has, in the cross section, the shape of a "m", the middle leg of which forms the central armature (17), the coil mounted about this armature being surrounded externally by an outer casing (18), which is parallel with the central armature and connected thereto by a planar end armature (19) extending perpendicular to the central armature against the face of the coil opposite that which bears the elastic stop (16), which is housed between the central armature and the peripheral casing.
4. Device according to one of Claims 2 or 3, characterized in that the elastic stop (16) has a height such that, prior to contact with the transverse plate (10), it projects slightly beyond the support plane thereof, by a distance which determines the dimensions of the resisting force braking the speed of the plate at the end of travel.
5. Device according to any one of Claims 2-4, characterized in that the elastic stop (16) is produced in the form of one or more continuous strips (16a, 16b) made of elastomer material.
6. Device according to any one of Claims 2-4, characterized in that the elastic stop (16) is formed from a plurality of separate blocks, that are preferably evenly distributed on the surface of the coil (15) about the central armature (17).
7. Device according to Claim 6, characterized in that the separate blocks forming the elastic stop (16) have a cylindrical profile, as a regular hyperboloid or truncated cone in the areas (16c) thereof for anchoring on the electric coil (15), that is extended by an outwardly projecting cylindrical part (16d).
8. Device according to any one of Claims 1-7, characterized in that the elastic stop (16) is produced from an elastomer material, of the natural or synthetic rubber, or silicone type.
9. Device according to any one of Claims 2-8, characterized in that the coil (15) of each electromagnet (12, 13) comprises an electric winding embedded in an insulating resin, the stop (16) being anchored and stuck to the coil by means of this resin.
10. Device according to Claim 9, characterized in that the resin is cast about the electric winding of the coil (15) before installing the stop (16).
11. Device according to Claim 9, characterized in that the stop (16) is installed on the electric winding of the coil (15) before casting the resin.

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