DE10241591A1 - Electromagnetic actuator drive especially for combustion engine gas-exchange valves, has sleeve-shaped armature mounted on carrier element and designed as common armature for both magnets - Google Patents

Abstract

An electromagnetic actuator drive has two pot-type magnets (4,4a) arranged coaxially in a housing, and with their pole plates positioned with a given spacing opposite one another and with a movable carrier element located between them and having a sleeve-shaped armature fixed to it. The pole plates (7,7a) have an annular air-gap (12,12a) and the sleeve-shaped armature on the carrier element (11) is designed as a common armature of both pot-type magnets (4,4a) and is displaceable in the air-gap. The thickness of the pole plates (7,7a) at least corresponds to the stroke of the carrier element, and the latter can be positioned, together with the associated actuating element (10), along the stroke.

Description

The invention relates to an electromagnetic Actuator, preferably for actuating gas exchange valves in piston internal combustion engines, with two coaxially arranged in one housing Pot magnets whose pole plates are at a predetermined distance from each other face and in which there is a displaceable carrier element is on which a sleeve-shaped anchor is attached.

With piston internal combustion engines the gas exchange processes usually controlled by valves so that a fuel / air mixture get into the combustion chamber, burn there and then as exhaust gas can escape. For this purpose, the valves are over a or several camshafts in synchronism with the piston movement actuated, to accomplish the charge change. Since the opening and closing times the valves are predetermined by the camshaft is usually for the Control of quantity and ratio of the fed Fuel / air mixture uses a throttle valve. Such one However, engine control is very lossy because of the throttle losses are considerable in particular in the partial load range.

To make a significant improvement here to achieve a throttle-free control is aimed. This means that the charge change is then carried out directly by the control system of the opening cross section the intake valves, i.e. through the valve lift and its opening time must be done. The advantage here is that there are almost no flow resistances occur.

In “MTZ Motortechnische Zeitschrift 62, 2002, 6, pages 450 to 463 ", a gasoline engine has already been described, the over a fully variable valve train with a mechanical adjustment system features. This fully variable valve control system opens up through the greatest savings potential is to avoid throttling losses as far as possible in gasoline engines.

The variable mechanical valve lift is here by an intermediate lever and an additional shaft with eccentric cams reached. The eccentric of the eccentric shaft is the fulcrum of the Intermediate lever and thus the valve lift. The eccentric shaft is coupled with a rotation angle sensor and is powered by an electric motor driven. The particular advantage here is that the valve lift from idle to full load in the shortest possible time Time can be adjusted.

The disadvantage here is the considerable mechanical effort and the associated unavoidable wear, which then through further technical measures must be partially compensated.

To eliminate this disadvantage are different spring-anchor systems with electromagnets as control elements for the valve or the valve stem of petrol engines.

So describes the DE 33 07 070 C2 a spring-mass system in which two electromagnets are arranged at a distance from one another, between the pole faces of which an armature is moved back and forth in accordance with the current supply. The armature is firmly connected to the valve stem and opens and closes the valve accordingly. The armature furthermore has an armature plate, on which two prestressed return springs act, so that the spring-mass system is formed. When one of the electromagnets is switched off, the system swings into the other end position and is held there by the magnet. Two switch positions can thus be implemented.

To make the system ready for operation, the anchor can be brought into one of the two end positions, what achieved by generating vibrations with increasing amplitude until an electromagnet catches the armature in an end position and holds.

The disadvantage of this system is besides the inevitable noise, that this has to be made ready to start as the anchor in neutral position between the two end positions and not be pulled into one of the end positions by one of the electromagnets can. Moreover throttle valve free operation is not possible because only between the both end positions can be switched. In addition, the combustion chamber or the piston should be designed so that during the oscillation process between the also vibrated valve and the Piston at top dead center no contact can occur.

From the US 6,216,653 B1 a gas exchange valve has also become known, in which the known spring-armature system with two springs acting against each other on the armature with two electromagnets arranged opposite one another has been supplemented by a hollow cylindrical permanent magnet. As a result, a sufficient magnetic flux occurs even when the electromagnet is not energized, which holds the armature in an end position (valve open or closed). It is characteristic of such a drive, however, that the magnetic force increases exponentially with increasing proximity of the disk part to one of the pole plates. As a result, a hard hit cannot be avoided.

With the electromagnets here are connected in series, this is done during operation Switch the armature between the two end positions. A continuous one However, load control cannot be achieved with this system, but for that a significant reduction in electrical energy consumption.

Finally describes the US 6,308,667 B1 a gas exchange valve with a disk-shaped armature which is provided with ring-shaped teeth, which correspond to correspondingly shaped grooves of the magnetic cores. This arrangement is intended to avoid the otherwise exponentially steep drop in the attractive force and to linearize the course of the attractive force. This should provide enough magnetic force even with a larger distance. Like the systems already described, this system is designed as a spring-mass system, which can be used to switch between two end positions when the electromagnets are suitably energized.

Based on this state of the art the invention has for its object an electromagnetic actuator to create, which is immediately operational when switched on and which in particular for actuation of gas exchange valves in piston internal combustion engines with variable Valve stroke is suitable.

To solve the problem underlying the invention The task is performed by an electromagnetic actuator, preferably for actuating Gas exchange valves in piston internal combustion engines. This Actuator consists of two pot magnets arranged coaxially in a housing Pole plates face each other at a predetermined distance. There is a sliding support element between the pole plates, which by a sleeve-shaped anchor is surrounded.

According to the invention, the Pole plates of the pot magnets have an annular air gap, whereby the on the support member attached sleeve-shaped anchors is designed as a common anchor of the two pot magnets. The sleeve-shaped anchors is displaceable in the air gap, the thickness of the pole plates at least the stroke of the carrier element corresponds and wherein the carrier element and along the associated actuator the stroke can be positioned as desired.

The particular advantage of this electromagnetic Actuator can be seen in the fact that the carrier element with the sleeve-shaped anchor fixed with appropriate current between the pot magnets and that from one of the two end positions the Force is greatest and becomes almost zero when the other end position is reached. In order to on the one hand becomes a safe positioning movement with very high acceleration reached and on the other hand an impact of the carrier element on the pole plates prevented. At the same time it ensures that the actuator is immediately ready for use when switched on.

In a first continuation of the invention, the position of the carrier element along the stroke path (s) can be positioned as desired by appropriate independent adjustment of the currents I ₁ and I ₂ conducted through the coils.

In addition, the electromagnetic according to the invention Actuator with appropriate dimensions for any Use positioning tasks and is therefore not on the field of application of actuation limited by gas exchange valves.

The sleeve-shaped anchor consists of a soft magnetic Material, this one-sided completely in the air gap of the respective pot magnet is retractable. The wall thickness of the sleeve-shaped anchor is to be dimensioned so that an optimum in terms of saturation and the force effect is achieved.

In a variant of the invention provided that in each case an annular approach within the housing parts protrudes, with the annular air gap between the annular Approach and the circumference of the pole plates is located.

To get a maximum actuating force from a to reach the end positions, the inner edge of the sleeve-shaped anchor in the extended state (lower or upper end position according to the drawing) the outer lower or top edge of the respective pole plate opposite.

The carrier element is a further development of the invention with a centrally guided in the pot magnet actuator that is also designed as a valve stem, so that the electromagnetic Actuator directly for controlling a gas exchange valve an internal combustion engine can be used.

So that the electromagnetic properties of the actuator are not adversely affected and by one To achieve linear force-displacement characteristics, the support element is made made of a non-magnetic material. So long the saturation of the magnetic material is not reached, the positioning force or the magnetic force is proportional to the current through the solenoids.

For a precise and smooth management of the support element with the sleeve part for measuring purposes can the shaft in axial ball bearings or similar bearings within the Pot magnets are guided. In normal use it is enough a simple plain bearing, which may be included in the engine lubrication becomes.

In a special configuration the invention, the sleeve-shaped anchor is spring-loaded in one of the two stroke end positions. An appropriately dimensioned is sufficient for this Spring consisting of only the dead weight of the assembly Gas exchange valve, actuator, support element and sleeve-shaped anchor, to overcome Has. This spring has the energized state of the electromagnetic Actuator, so during the Realization of the positioning processes no function.

The invention is intended to be described below an embodiment are explained in more detail. To show:

1 : A sectional view of an electromagnetic actuator according to the invention;

2 : A sectional view of an electromagnetic actuator according to the invention with plain bearings, and

3 : the distance-force characteristic of the electromagnetic actuator 1 ,

The electromagnetic actuator according to the invention consists of a cylindrical housing 1 , consisting of two housing parts 2 . 2a that have a screw connection 3 are screwed together axially.

These housing parts 2 . 2a are part of the magnetic circuit of two pot magnets 4 . 4a consisting of a soft iron core 5 . 5a which on one end in the housing part 2 . 2a recessed cover plate 6 . 6a is attached centrally. On that of the closing plate 6 . 6a opposite end of the soft iron cores 5 . 5a there is a pole plate connected in one piece to this 7 . 7a , Finally, the pot magnets also contain a coil 8th . 8a to generate a magnetic flux.

Centric in the pot magnets 4 . 4a is via axial ball bearings 9 . 9a an actuator 10 led, on which is between the pole plates 7 . 7a a support element 11 located. The thrust ball bearing 9 . 9a is only advantageous for measuring purposes. In the practical application of the electromagnetic actuator, customary plain bearings can be used for the actuating element, for example a gas exchange valve, which may be included in the engine lubrication.

The carrier element 11 and the shaft 10 are made in one piece from the same material in the embodiment. But since only the support element 11 must consist of a non-magnetic material, this can also be non-positively with the actuator 10 , for example by shrinking. The carrier element 11 can be disc-shaped, other shapes, such as radially arranged supports, can also be realized.

This means that the pot magnets 4 . 4a generated magnetic flux is not adversely affected, and the in 3 shown linear force-displacement curve is not disturbed, as can be shown.

There is still an air gap for the function of the electromagnetic actuator 12 . 12a important, which is between the outer periphery of the pole plate 7 . 7a and the inner wall of the housing part 2 . 2a extends. In this air gap 12 . 12a can be a sleeve-shaped anchor 13 which is the support element 11 encloses, immerse one side at a time, i.e. upwards into the air gap according to the drawing 12 and down into the air gap 12a ,

To make this possible, the thickness of the pole plate 7 . 7a at least the maximum stroke s of the sleeve-shaped armature 13 correspond.

Inside the housing part 2 . 2a can also be the pole plates 7 . 7a enclosing annular approach may be provided, wherein the annular air gap 12 . 12a then between the annular shoulder and the periphery of the pole plate 7 . 7a located.

This sleeve-shaped anchor 13 consists of a soft magnetic material and is the common movable anchor of the two pot magnets 4 . 4a , Now the coil 8th energized, there is a magnetic force F, which the sleeve-shaped armature 13 in the air gap 12 draws. Will the coil 8a energized, so the sleeve-shaped anchor 13 accordingly in the air gap 12a drawn. The acceleration of the sleeve-shaped anchor 13 which is achieved depends on the size of the current.

In contrast to the prior art, it is characteristic here that the lower the sleeve-shaped armature, the lower the magnetic force F 13 in the air gap 12 . 12a plunges in as from the force-displacement characteristic 2 can be seen. On the other hand, the magnetic force F is greatest when the upper inner edge is 14 of the sleeve-shaped anchor 13 and the outer bottom edge 15 the pole plate 7 face each other, or the lower inner edge 14a of the sleeve-shaped anchor 13 and the outer top edge 15a the pole plate 7a , This situation is in the two end positions of the carrier element 11 given.

The result of this is that the electromagnetic actuator is fully operational as soon as it is switched on. Now both coils 8th . 8a energized simultaneously with the same current I ₁ , I ₂ , the carrier element 11 in the out 1 apparent middle position pulled and held there, since in this case the forces F ₁ and F ₂ cancel. Will the coils 8th . 8a with different currents, each intermediate position can be set along the stroke s ( 2 ).

In the practical application of the electromagnetic actuator, however, it is absolutely necessary that the gas exchange valve, not shown, has a certain starting position in the de-energized state. Usually the gas exchange valve must be in the starting position or in the event of a power failure, be closed to prevent the valve from colliding with the piston to rule out in any case.

To achieve this, an auxiliary spring is sufficient, which must be dimensioned such that it the actuator (shaft) 10 presses in one of the two end positions when de-energized. If the gas exchange valve is to be closed when de-energized, the auxiliary spring must be the actuator 10 with the support element 11 and the sleeve-shaped anchor 13 press into the upper end position as shown. In contrast to the spring / mass systems used in the prior art, this auxiliary spring is completely inoperative during the operation of the electromagnetic actuator.

1

casing

2, 2a

housing part

3

screw

4, 4a

pot magnet

5, 5a

Soft iron core

6 6a

closing plate

7, 7a

pole plate

8th, 8a

Kitchen sink

9 9a

Axialkugellager

10

actuator

11

support element

12 12a

air gap

13

sleeve-shaped anchor

14 14a

inner edge

15

outer lower edge

15a

outer upper edge

s

stroke

I ₁ , I ₂

electricity

F ₁ , F ₂

force

Claims (10)

Electromagnetic actuator, preferably for actuating gas exchange valves in piston internal combustion engines, with two pot magnets arranged coaxially in a housing, the pole plates of which face each other at a predetermined distance and in which there is a displaceable support element to which a sleeve-shaped armature is fastened, characterized in that that the pole plates ( 7 . 7a ) the pot magnets ( 4 . 4a ) an annular air gap ( 12 . 12a ) that the on the support element ( 11 ) attached sleeve-shaped anchors ( 13 ) as a common anchor of the two pot magnets ( 4 . 4a ) is formed, which in the air gap ( 12 . 12a ) is displaceable, the thickness of the pole plates ( 7 . 7a ) at least the stroke (s) of the carrier element ( 11 ) corresponds and that the carrier element ( 11 ) and the associated actuator ( 10 ) can be positioned anywhere along the stroke (s). Electromagnetic actuator according to claim 1, characterized in that the position of the carrier element ( 11 ) along the stroke (s) by corresponding de independent adjustment of the by the coils ( 8th . 8a ) conducted currents I ₁ and I ₂ can be positioned as desired. Electromagnetic actuator according to claim 1, characterized in that the sleeve part ( 13 ) consists of a soft magnetic material. Electromagnetic actuator according to claim 1 to 3, characterized in that the sleeve part ( 13 ) one-sided completely in the air gap ( 12 ; 12a ) of the respective pot magnet ( 4 ; 4a ) is retractable. Electromagnetic actuator according to claims 1 to 4, characterized in that within the housing part ( 2 . 2a ) the pole plates ( 7 . 7a ) surrounding annular projection protrudes in such a way that the annular air gap ( 12 . 12a ) between the ring-shaped extension and the circumference of the pole plate ( 7 . 7a ) is located. Electromagnetic actuator according to claims 1 to 4, characterized in that the inner edge ( 14 ; 14a ) of the sleeve part ( 13 ) when the outer lower or upper edge is extended ( 15 . 15a ) of the respective pole plate ( 7 ; 7a ) faces. Electromagnetic actuator according to one of claims 1 to 6, characterized in that the carrier element ( 11 ) with one in the center of the pot magnet ( 4 . 4a ) guided actuator ( 10 ) is firmly connected. Electromagnetic actuator according to claim 7, characterized in that the carrier element ( 11 ) consists of a non-magnetic material. Electromagnetic actuator according to claim 7 or 8, characterized in that the actuating member ( 10 ) in axial ball bearings ( 9 . 9a ) inside the pot magnets ( 4 . 4a ) is performed. Electromagnetic actuator according to one of claims 1 to 10, characterized in that the sleeve-shaped armature ( 13 ) when the coils are de-energized ( 8th . 8a ) is spring-loaded in one of the two stroke end positions.