EP1007825A1

EP1007825A1 - Device for actuating a gas exchange valve with an electromagnetic actuator

Info

Publication number: EP1007825A1
Application number: EP98940271A
Authority: EP
Inventors: Matthias Gramann; Roland Krebser; Rosario Pepe; Thomas Stolk; Dirk Strubel; Alexander Von Gaisberg; Klaus Wunderlich
Original assignee: DaimlerChrysler AG; Temic Telefunken Microelectronic GmbH
Current assignee: Conti Temic Microelectronic GmbH; Mercedes Benz Group AG
Priority date: 1997-08-30
Filing date: 1998-08-08
Publication date: 2000-06-14
Also published as: WO1999011908A1; DE19737967A1

Abstract

The invention relates to a device for actuating a gas exchange valve with an electromagnetic actuator, having an opening magnet and a closing magnet. An axially displaceable armature is arranged between the pole faces of said magnets, which alternately comes into contact with the thrust face on the pole faces of the magnets and which is stopped at least in front of a pole face by a damping device. According to the invention, the damping device consists of a separate damping element with a damping piston and a cylinder, which can be displaced towards each other and dampened by a non-gaseous medium.

Description

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The invention relates to a device for actuating a gas exchange valve with an electromagnetic actuator according to the preamble of patent claim 1.

Electromagnetic actuators for actuating gas exchange valves generally have two switching magnets, an opening magnet and a closing magnet, between the pole faces of which an armature is arranged so as to be displaceable coaxially with a gas exchange valve axis of the gas exchange valve. The armature acts on the valve stem of the gas exchange valve via an armature tappet. In the case of actuators based on the principle of the mass oscillator, a preloaded spring mechanism, usually two preloaded compression springs, acts on the armature, namely an upper and a lower valve spring. The upper valve spring acts in the opening direction and the lower valve spring in the closing direction of the gas exchange valve. When the solenoids are not energized, the armature is held in an equilibrium position by the valve springs, which preferably coincides with the geometric or with an energetic center between the solenoids.

If the actuator is started, the closing magnet or the opening magnet is briefly overexcited or the armature is excited in its resonance frequency by an oscillation routine in order to attract it from the equilibrium position. The armature is in the closed position of the gas exchange valve with a first contact surface on the pole surface of the energized closing magnet and is held by this. The closing magnet biases the valve spring acting in the opening direction. To open the gas exchange valve, the closing magnet is switched off and the opening magnet is switched on. The valve spring acting in the opening direction accelerates the armature beyond the equilibrium position, so that it is attracted by the opening magnet. The armature meets with its second contact surface on the pole surface of the opening magnet and is held by it. To close the gas exchange valve again, the opening magnet is switched off and the closing magnet is switched on. The valve spring acting in the closing direction accelerates the armature beyond the equilibrium position to the closing magnet. The armature is attracted by the closing magnet, hits the pole face of the closing magnet and is held by it.

In addition to forces that act on a valve plate of the gas exchange valve and must be overcome in particular when opening, losses in the opening direction and in the closing direction occur in the device due to guide friction, internal friction of the springs and aerodynamic damping, which must be compensated for so that the device lasts works, ie the gas exchange valve closes and opens safely. The time between the detachment from one pole face and the impact on the opposite pole face of the armature is in the range of a few milliseconds. In this very short time, it is difficult to precisely couple the required energy through control measures. It is therefore necessary to operate the device with a certain excess energy in order to ensure safe operation.

Due to the excess energy, the armature hits the pole faces of the magnets at a high speed, with the result that the wear increases and the noise is considerable. From DE 39 20 931 AI a damping device is known which brakes the armature in front of the pole face by compressing gas between the armature and the pole face. The play between the armature and a cam ring is reduced in front of the pole face and thus the outflow cross-section for the gas. In addition, energy is converted into volume change work - only the excess energy in the system may be reduced shortly before the end position is reached. The armature should only be braked shortly before the pole faces and move as freely as possible in the remaining area between the pole faces, ie against a low back pressure, so that the damping affects the control characteristics of the gas exchange valve and the efficiency and the gas exchange valve opens smoothly, quickly, almost completely and can be closed. A large volume change is required to build up sufficient back pressure for gaseous media. Here the gas must be compressed far in front of the pole face in order to achieve sufficient damping shortly before the pole face. The gas exchange valve closes and opens more slowly over wide areas, which in turn requires energy to be supplied.

In devices that brake the armature primarily by elastic deformation, for example with a spring-loaded armature, as is known from DE 30 24 109 C2, an increased holding energy must be applied by the magnet so that the armature is not affected by the the spring stored energy is catapulted away from the pole face.

Furthermore, a damping device for a valve control is known from US Pat. No. 4,794,890, in which a hydraulic damping is combined with an elastic damping. The valve control has two anchors, an upper closing anchor and a lower opening anchor, which are between two pole faces an upper closing magnet and a lower opening magnet are slidably arranged. Between the armatures there is a hydraulic piston guided in a cylinder fixed to the housing and between the piston and the armature two diaphragm springs directed towards each other, which are connected to the armature for common movement. In the closed position, the locking armature is held by the locking magnet. If the gas exchange valve is opened, the closing magnet repels the closing anchor and the opening anchor is attracted to the opening magnet. Shortly before the opening armature hits the pole face of the opening magnet, it is damped by the piston hitting and prestressing the disc springs and the piston moving in the cylinder. When the gas exchange valve is closed, the process proceeds accordingly in the opposite direction. The two anchors and the disc springs arranged between them and the piston create a complex construction with many individual parts and with a large moving mass and overall height.

From DE 35 00 530 AI a device for electromagnetic control of globe valves by means of an actuator is known in which the coil springs arranged on both sides of the armature with their end assigned to the armature via a damping sleeve and a cone fixedly attached to a valve stem on the valve stem and thus on Support anchor. The damping sleeve, which serves as a spring plate, consists of a material that is elastically resilient in the radial direction and lies with a conical lateral surface, the cone angle of which is chosen close to the self-regulating angle, on a corresponding lateral surface of the cone attached to the valve stem. This measure dampens the impact of the valves and armature masses shortly before reaching the end position, the kinetic energy being converted into a largely inelastic impact, so that the armature does not bounce or only bounces slightly. The damping effect based on friction and clamping forces is difficult to adjust and due to wear To keep constant over the service life, especially since the components perform additional functions, namely to serve as spring plates for the actuator springs.

The object of the invention is to reduce the excess energy of the armature and the valve in a short way in front of the pole face of the magnet with as few additional components as possible, without the holding forces having to be increased significantly.

The object is achieved according to the invention by the features of claim 1, while advantageous refinements and developments of the invention can be found in the subclaims.

With a separate damping element, i.e. with its own component provided with a damping piston and a cylinder, which can be displaced relative to each other by a non-gaseous medium, precisely defined counterforces can be created to brake the armature shortly before a pole face of a magnet without the armature and the gas exchange valve between the magnets are prevented from moving. If the damping piston or the cylinder is moved against a non-gaseous material, a high counterforce can be generated over a short distance. Part of the excess energy can be absorbed temporarily before it is broken down in the damping element. Gaseous media are excluded because a large volume change is required for a sufficiently high back pressure and thus a large distance. In closed, pressurized systems with gas, a high back pressure can be achieved over short distances, but a large proportion of the kinetic energy is converted into clamping energy, which means that the magnet must apply an increased holding force so that the armature does not move away from the pole face is catapulted. Damping material emerging from the damping element can hinder the function of individual components, for example in the case of oil, the pole faces of the magnets and the contact faces of the armature can become oiled, as a result of which the armature detaches more poorly from the pole faces. In one embodiment of the invention it is proposed that the damping element form a closed system in itself, ie the damping material is tightly sealed to the outside.

If oil is used as the damping material, this can be achieved with seals.

However, it is particularly advantageous to use plastically deformable materials instead of oil, which can be securely sealed to the outside with little effort. In one embodiment of the invention, this is achieved in that the damping piston is displaceably guided in the cylinder via a fit.

The armature should be decelerated from a high speed by a large counterforce to a low speed in front of the pole face and should be able to be attracted to the pole face at the low speed with almost no counterforce by the magnet, directly at the low speed. After detaching the contact surface of the armature from the pole surface, the damper should return to its starting position as quickly as possible.

If the damping material is oil, this can be achieved with a throttle in one direction and with a check valve with a large flow area in the other direction.

However, oil is more difficult to seal, especially at higher temperatures. In order to obtain a damping element described in accordance with the requirements, which is securely sealed to the outside with little effort, in In one embodiment of the invention it is proposed to use a viscous or pasty material as damping material, the shear stress of which increases sharply with the rate of deformation.

Such properties can be created specifically in the case of plastic elastomers, as a result of which these materials are particularly suitable for this use. Such substances are known to the person skilled in the art under the name "bouncing putty" and are preferably based on organosilicon polymers.

Further details of the invention and the advantages resulting therefrom can be found in the following description of exemplary embodiments.

Numerous features are shown and described in connection in the description and in the claims. The person skilled in the art will expediently also consider the features individually and combine them into further useful combinations.

Show it:

1 shows an actuator for actuating a gas exchange valve with a built-in damping element, FIG. 2 shows an enlarged section of the damping element from FIG. 1, and FIG. 3 shows a variant of FIG. 2.

1 shows a device for actuating a gas exchange valve 1 with an actuator 2, which has an opening magnet 3 and a closing magnet 4. An armature 7 is arranged axially displaceably between pole faces 5, 6 of the magnets 3, 4. The armature 7 alternately strikes the pole faces with its contact surfaces 8, 9 and is held by the magnets 3, 4 in two separate switching positions. The armature 7 is fastened on an armature tappet 22 or embodied in one piece with it, with which it acts on a valve stem 23 of the gas exchange valve 1. Furthermore, the actuator 2 has a spring system 24 below the opening magnet 3 with a lower valve spring 25 acting in the closing direction and with an upper valve spring 26 acting in the opening direction. The lower valve spring 25 is supported in the direction of the gas exchange valve 1 on the component 27 and in the Gas exchange valve 1 facing away from a spring plate 28 attached to the valve stem 23. The upper valve spring 26 is supported in the direction of the gas exchange valve 1 on a spring plate 29 fastened on the armature tappet 22 and in the direction remote from the gas exchange valve 1 on the opening magnet 3. The valve springs 25, 26 are preloaded to the extent that the armature 7 adjusts to an approximately middle position between the switching magnets 3, 4 when the solenoids 3, 4 are undisturbed and immediately before the closed position of the gas exchange valve 1 a residual closing force of the lower valve spring 25 and immediately before a residual prestressing force of the upper valve spring 26 is present in the open position.

If the actuator 2 is started, either the closing magnet 4 or the opening magnet 3 is overexcited or the armature 7 is excited with its resonance frequency using an oscillation routine in order to move it to a pole face 5, 6 and hold it there. In the closed position of the gas exchange valve 1, the armature 7 rests with its first contact surface 9 against the pole surface 6 of the energized closing magnet 4 and is held by it. The closing magnet 4 biases the upper valve spring 26 acting in the opening direction. In order to open the gas exchange valve 1, the closing magnet 4 is switched off and the opening magnet 3 is switched on. The valve spring 26 acting in the opening direction accelerates the armature 7 beyond the equilibrium position, so that it is attracted by the opening magnet 3. The armature 7 meets with its second contact surface 8 on the pole surface 5 of the opening magnet

only immediately before the armature 7 hits the pole face of the closing magnet 4 or the valve plate 30 on the valve seat ring 31 and does not hinder the movement of the armature 7 in the direction of the opening magnet 3, whereby only one armature 7 is required.

Due to the central arrangement, only a small area is required for the damping element 10 in the pole face 6. With the same size, the pole face 6 is reduced only insignificantly. Furthermore, the influence on the magnetic field is very small in the middle. However, it is also possible to arrange one or more annular damping elements in the pole faces 5, 6 or one or more damping elements on the circumference of the pole faces 5, 6, which is particularly suitable for the opening magnet 3, in which a central arrangement by the armature plunger 22 may be possible could result in a more complex construction of the damping element.

The damping element 10 consists of a damping piston 11 which is displaceably mounted in a cylinder 12 against a damping material 13 (FIGS. 2 and 3), it also being possible for the cylinder to be displaceable and the piston to be fixed. The damping piston 11 protrudes from the pole face 6 of the closing magnet 4 in the direction of the contact face 9 of the armature 7, and acts directly on the armature 7. Additional components and moving masses are saved, for example plunger attached to the armature 7, via which the damping element 10 acts on the armature 7 Anchor 7 acts.

The damping piston 11 preferably protrudes from the pole face 6 to such an extent that the speed of the armature 7 can be braked to almost zero in the shortest possible way to the pole face 6.

In order to take into account variables that cannot be determined exactly from the beginning or change over time, such as manufacturing tolerances of individual components, thermal expansion of different materials, etc., and the damping element 10 To be able to set exactly, the damping element 10 is mounted in the closing magnet 4 in the direction of movement 19. This can be achieved via a large number of different adjustment mechanisms familiar to the person skilled in the art, such as, for example, via clamping mechanisms, adjustment screws, etc. In the exemplary embodiment, the cylinder 12 is adjustably mounted in the recess 14 via an external thread 20 in an internal thread 21. The recess 14 extends in the direction of movement 19 of the damping piston 11 through the entire closing magnet 4, from the pole face 6 to the side of the closing magnet 4 facing away from the gas exchange valve 1. Furthermore, the internal thread 21 extends over the entire recess 14, whereby the damping element 10 of the side of the closing magnet 4 facing away from the gas exchange valve 1 is adjustable, mountable and, if necessary, removable and replaceable. After the damping element 10 is set exactly, it is fixed with a locking device, not shown, such as a lock nut, a locking screw or any other mechanism familiar to the person skilled in the art.

According to the invention, a non-gaseous, preferably plastically deformable damping material 13 is used, against which the damping piston 11 is displaced.

The requirements for the material 13 result from the task of the damping element 10 to generate a large counterforce at a high speed of the armature 7 in order to brake the armature 7 in a short way and at a low speed of the armature 7 directly in front of the pole face 6 generate as small a counterforce as possible that the armature 7 can be easily attracted to the pole face 6 by the closing magnet 4.

If the armature 7 a bears against the pole face 6, the damping element 10 should exert as little force as possible on the armature act so that the holding force of the closing magnet 4 does not have to be increased significantly.

If the armature 7 detaches from the pole face 6, the damping element 10 should quickly return to its starting position before the damping process.

Furthermore, the damping element 10 should represent a system which is closed to the outside, as a result of which no escaping substances impede the remaining functions of the device.

The large opposing forces at high and the small opposing forces at low speeds of the armature 7 are preferably achieved by viscous or pasty materials 13, the shear stress of which increases sharply with the rate of deformation. Such properties can be created specifically in the case of plastic elastomers and in particular in the case of elastomers based on an organosilicon.

The viscous materials 13 can also be easily sealed to the outside. In the exemplary embodiments shown, the damping piston 11 is displaceably mounted via a fit in the cylinder 12, which is sufficient as a seal for correspondingly viscous materials 13. Additional seals can be saved.

So that the damping piston 11 is displaceable against the material 13 and does not jam, either the material 13 must be compressible or there must be a space in which the material 13 can be displaced. A corresponding space is provided in the exemplary embodiment shown (FIGS. 2 and 3). A damping element 10 with compact material and without this space would, however, also be possible.

In the embodiment according to FIG. 3, the space is formed by a recess 16 on the side of the damping piston 11 facing away from the armature 7. Preferably cylindrical There is a spring 15 which is supported against the material 13 by a piston 17 guided in the recess 16. If the armature 7 deflects the damping piston 11, the material 13 is displaced into the recess 16 and thereby pushes the piston 17 against the spring 15 into the recess 16. At the initially high speed of the damping piston 11, high shear stresses act in the material 13, thereby the damping piston 11 builds up a high counterforce against the direction of movement of the armature 7. Immediately in front of the pole face 6, the armature 7 is braked to a low speed, so that almost only the spring force has to be overcome by the closing magnet 4 in order to fully attract the armature 7 to the pole face 6.

After the armature 7 detaches itself from the pole face 6 of the closing magnet 4, the spring 15 moves the damping piston 11 back into the starting position. The starting position is determined by a stop 32 in the cylinder 12, against which the damping piston 11 runs with a step 33. A spring 15 can be dispensed with if materials are used which have an elasticity corresponding to the spring 15, i.e. do not generate a too large counterforce when the armature 7 bears against the pole face 6 and nevertheless generate a sufficient force to return the damping piston 11 to its initial position as soon as the armature 7 detaches itself from the pole face 6.

The space into which the material 13 can escape could also be arranged in the cylinder 12 instead of in the damping piston 11. Furthermore, the space and the spring could be combined by pushing the material against a membrane.

2 shows an embodiment of the damping element 10 according to the invention without a piston 17. The material 13 surrounds the spring 15 and fills the space between the damping piston 11 and the cylinder 12 except for small spaces (not shown) by pre-stretching the material 13 enclosed space completely. If the damping piston 11 is deflected by the armature 7, a damping effect arises in particular by the spring 15 shifting in the material 13, taking it along and displacing it together with the damping piston 11 into the free spaces.

In addition to the enclosed damping material 13 between the damping piston 11 and the cylinder 12, part of the kinetic energy of the armature 7 is absorbed by a damping plate 18 which is attached to the end face of the damping piston 11 facing the armature 7. A shock-absorbing plastic is particularly suitable as the material for the damping plate 18, although other materials that appear suitable to a person skilled in the art for such a purpose can also be used.

Claims

claims

1. Device for actuating a gas exchange valve with an actuator which has an opening magnet and a closing magnet, between the pole faces of which an armature is arranged to be axially displaceable and which alternately strikes the pole faces of the magnets with contact surfaces and is braked by a damping device at least in front of a pole face characterized in that the damping device is formed by a separate damping element (10) with a damping piston (11) and a cylinder (12), between which there is a flowable or plastically deformable, non-gaseous damping material (13) and which are mutually separated by the Damping material (13) is displaceable when damped.

2. Device according to claim 1, characterized in that the damping element (10) is a εich geεchloεseneε system.

3. Apparatus according to claim 1, characterized in that the damping piston (11) against a viscous material (13) is displaceable, whose shear stress increases sharply with the rate of deformation.

4. The device according to claim 3, characterized in that the material (13) is a plastic elastomer.

5. Device according to one of the preceding claims, characterized in that the damping piston

(11) with a fit in the cylinder (12).

6. Device according to one of the preceding claims, characterized in that the damping element (10) iεt in the closing magnet (4) and / or in the opening magnet (3) attached.

7. The device according to claim 6, characterized in that the cylinder (12) deε damping element (10) in the middle of the closing magnet (4) is fixed in a recess (14).

8. Device according to one of the preceding claims, characterized in that the damping piston (11) protrudes from the pole face (5, 6) of the magnet (3, 4) in the direction of the contact face (8, 9) of the armature (7) and directly acts on the contact surface (8, 9) of the anchor (7).

9. Device according to one of the preceding claims, characterized in that a spring (15) resets the damping piston (11) in its initial position before the damping process.

10. Device according to one of the preceding claims, characterized in that between the damping piston (11) and the cylinder (12) there is a space (16) in which the material (13) can be displaced.

11. Device according to one of the preceding claims, characterized in that the damping piston (11) has a recess (16) on the side facing away from the armature (7).

12. The apparatus of claim 9 and 11, characterized in that the spring (15) at least partially in the recess

(16) is arranged.

13. The apparatus according to claim 12, characterized in that the spring (15) is arranged in the recess (16) and εich is supported on the material (13) by a piston (17) guided in the recess (16).

14. Device according to one of the preceding claims, characterized in that the damping piston (11) has a damping plate (18) on its end facing the armature (7).

15. The apparatus according to claim 14, characterized in that the damping plate (18) is made of impact-absorbing plastic.

16. Device according to one of the preceding claims, characterized in that the damping element (10) in the magnet (3, 4) in the direction of movement (19) of the damping piston (11) is adjustable.

17. The apparatus according to claim 16, characterized in that the cylinder (12) has a thread (20, 21) in the magnet (3,

4) is adjustable.

18. The apparatus according to claim 17, characterized in that the cylinder (12) with an external thread (20) in an internal thread (21) is fixed in the recess (14).

19. Device according to one of the preceding claims, characterized in that daε damping element (10) from the gas exchange valve (1) facing away from the closing magnet (4) can be assembled, disassembled and / or adjusted.