EP0043426B1 - Electromagnetically operated adjusting device - Google Patents

Abstract

An electromagnetically operating actuator for control elements capable of making oscillatory movements in displacement machines, more particularly for flat slide shut-off valves and lift valves, includes a spring system and a pair of electrically operating switching elements, over which the control element is movable in two discrete opposite operating positions and is retained thereat by either switching magnet, the locus of the position of equilibrium of the spring system lying between the two operating positions. The invention is characterized by the provision of a compression device in engagement with the spring system for relocating the locus of the position of equilibrium of the spring system upon actuation of the compression device.

Description

The invention relates to an electromagnetically operating control device for oscillatingly movable control elements on displacement machines, in particular for flat slides and lifting elements, consisting of a spring-mass system that has the control element and a spring system that is operatively connected to it, that preferably two springs working against each other contains, and from two electrically operating switching magnets, via which the control element can be moved into two discrete, opposite switching positions and can be held there by one of the switching magnets.

In the case of displacement machines, an adaptable control for the inflow and outflow of the working medium is required in order to be able to optimally influence the working process according to the particular requirements. The control process has a major influence on various parameters, for example the conditions of the working medium before, in and after the working area, the working frequency and the processes in the working area. The need for adaptable control is particularly given in internal combustion engines, since they operate unsteadily in very different operating states and a correspondingly variable positive control of the gas exchange valves is advantageous.

In particular, camshafts have hitherto been used primarily to control the gas exchange valves in internal combustion engines. However, these do not allow variable control. In addition, electromagnetic controls of gas exchange valves on internal combustion engines have become known, in which the closing force is applied to the gas exchange valve by a spring, while the opening forces are generated by a correspondingly controlled electromagnet. This type of electromagnetic control has the disadvantage that short control times with high actuation frequencies and usual strokes of the gas exchange valves can only be achieved with extensive switchgear and high energy consumption (DE-A No. 2815849.2063158).

Furthermore, an electromagnetically operating control for gas exchange valves on internal combustion engines is known (DE-A No. 2335150), which consists of two water-cooled switching coils, each of which cooperate with an armature. The two anchors are attached to a common spindle, which acts on the gas exchange valve. As with the cam control, the gas exchange valve has a compression spring which holds the valve in its closed state, in addition to which a further spring of the same stiffness is provided, which acts on one of the armatures and is tensioned by the armature in the closed state of the valve, so that these two springs together with the gas exchange valve and the transmission elements such as the spindle and armature form a spring-mass system. To switch this device, one electromagnet is energized and the other switched off. Due to the preloaded springs of the spring-mass system, the spindle with the armature is accelerated up to half the stroke, in which both armatures are equidistant from the associated switching coils. The switching coils are designed in such a way that when excited they can pull their armature from this central position against the increasing force of the spring system. When this arrangement is switched off, both anchors also move into their central position, so that the gas exchange valve has already traveled half its stroke and is thus open.

This arrangement has the disadvantage that it can practically not be used in internal combustion engines, since switching off the internal combustion engine over a longer period of time with gas exchange valves open for all cylinders can lead to corrosion formation within the cylinders. Another disadvantage of this arrangement is that to start up an internal combustion engine equipped in this way, the switching coils for pulling an armature over half the stroke have to be designed for large forces over long distances, which is a very high energy requirement for an internal combustion engine with several cylinders, in particular for the Starting process means. Furthermore, it is disadvantageous in such an arrangement that, because of the high masses to be accelerated, a high switching frequency can only be achieved with large spring forces due to the two plunger anchors, as a result of which the required magnetic forces and thus the energy requirement increase sharply.

It is therefore an object of the present invention to provide a variable actuating device in a generic device of the type mentioned at the outset, which requires a small installation space, is simple in construction and can be operated with little control and power expenditure.

This object is achieved according to the invention in that a tensioning device is connected to the spring-mass system such that the static rest position of the spring-mass system moves from an essentially central position between the switching positions of the switching magnets to another, preferably in the area of the switching positions of the switching solenoids located.

The invention is based on the knowledge that a low power consumption of the switching magnets is only achieved when the static rest position of the spring-mass system can be relocated to start the actuating device. The result of this is that the shift magnets do not have to attract the control element from a central position between the shift positions when moving off, which means a high energy requirement depending on the size of the shift path. Since no high power is required to switch the control element itself, the total power consumption of the arrangement according to the invention is very low. This has the further advantage that there is no great heat development in the Switching magnet takes place, so that a separate cooling for them does not have to be provided. Due to the low power consumption, it is also advantageously possible to use the actuating device according to the invention for controlling gas exchange valves in internal combustion engines. According to the invention, it does not matter whether the static rest position of the spring-mass system is moved in the switched-off state or only when the actuating device is started.

An advantageous development of the invention provides that the tensioning device has at least two discrete positions, the static rest position of the spring-mass system in the first position of the tensioning device in the substantially central position between the switching positions of the switching magnets and in the second position of the Clamping device is in the range of one of the switching positions of the switching magnets. It makes sense to let the tensioning device move into its second position at least when the actuating device is started up. In addition, it is possible for this position to be reached even when the actuating device is not in use. This is particularly useful if a gas exchange valve of internal combustion engines is provided as the control element. This is associated with the decisive advantage for the control of the gas exchange valves of internal combustion engines, that the gas channel can be kept closed by the gas exchange valve when the internal combustion engine is switched off. The first position of the tensioning device is then only achieved when the adjusting device is in operation.

Any suitable tensioning device can be provided as a tensioning device in the sense of the invention, depending on the control element used. It can work mechanically, hydraulically, pneumatically or electrically. An embodiment of the tensioning device according to claim 3 is preferred. If gas exchange valves of an internal combustion engine are provided as control elements, it makes sense, for example as a tensioning device, for all gas exchange valves to have a common shaft, which is either eccentrically mounted or acts on the spring-mass system via corresponding levers, to be provided, which is shifted into its two discrete positions by a common switching device, for example an electric motor or a hydraulic cylinder.

If an electric motor is provided as the tensioning device, it makes sense to control it in its first position and to control it in its second position. This has the advantage that the switched-off position of the tensioning device coincides with the switched-off position of the actuating device, so that no energy requirement is required in the switched-off state. Another advantage is that in the first position there is no air gap between the coil and armature - that is, no field strength weakening - so that the energy requirement of the magnet is low.

The development of the invention according to claim 5 includes the advantage that the actuating device can move the control element at a high frequency, since the electromagnetic fields generated by the switching magnets can be built up and broken down at high frequency with low voltage peaks. This is achieved through a low inductance of the switching magnets. The tensioner electromagnet can be much slower, i.e. be equipped with a much higher inductance, since its operating frequency is significantly lower, because it remains in one of its two discrete positions during operation of the actuating device and only has to be switched to the other at least for starting.

Is the tensioning device switched to its second discrete position when the actuating device is switched off, i.e. the static rest position of the spring-mass system is in the range of one of the switching positions, so all magnets of an actuating device can be switched on together for commissioning the actuating device.

Due to the slower excitability of the electromagnet of the tensioning device, the switching magnets can hold the control element in one of the switching positions, so that this prevents the tensioning device from moving the static rest position between the two discrete switching positions when starting up.

The construction of the actuating device according to the invention makes it possible to design the forces of the switching magnets in such a way that they are greater than the counteracting forces of the spring system only shortly before the switching positions of the control element are reached. This allows switching magnets with a low attraction. force but large holding forces with practically no air gap between magnet and armature are used.

In order to keep the masses to be accelerated and thus also the holding forces to be applied by the switching magnets low, the development according to claim 7 is proposed. At the same time, an increase in the working frequency is possible due to the small masses to be accelerated.

For the function of the actuating device according to the invention, it does not matter where the spring system acts on the control element, since it only has to be ensured that the resulting force of the spring system is non-positively transmitted to the control element. If only one armature is provided for both switching magnets, it makes sense to let the spring system engage this armature. It is irrelevant here whether, for example, the spring system consists of two oppositely acting springs or a tension-compression spring.

The embodiment of the invention according to claim 9 includes the advantage that the entire switching time is available for the reconstruction of the magnetic field of the switching magnet, to which the control element is not present, that is to say the time which the armature takes to reach the other switching magnet get there and come back from there. Likewise, such an arrangement reduces the control outlay for the actuating device according to the invention, since now only a brief switch-off signal is required to switch the actuating device.

With the embodiment of the invention according to claim 10, the advantage is achieved that deviations from the target dimensions between the seat surface of the control element and the pole surfaces of the switching magnets, which occur due to installation tolerances, thermal expansion and wear and tear and can impair the safe reaching of the two discrete positions of the control element, be prevented. It makes sense to design the spring stiffness of these springs to be significantly higher than the spring stiffness of the spring system.

The development according to claim 11 ensures that the control element does not hit hard when it reaches its discrete positions, but reaches it in a damped manner.

• Fig. 1 bis 4 Querschnitte durch die erfindungsgemässe Stelleinrichtung mit einem Gaswechselventil einer Hubkolbenbrennkraftmaschine als Steuerelement;
• Fig. 5 die erfindungsgemässe Stelleinrichtung im Querschnitt mit einem Flachschieber als Steuerelement;
• Fig. 6 eine Befestigungsmöglichkeit des Doppelankers an dem Schaft eines Steuerelements;
• Fig. 7 und 8 Kraft-Weg-Diagramme der erfindungsgemässen Stelleinrichtung.

The invention is explained in more detail below on the basis of preferred exemplary embodiments. They represent:

• 1 to 4 cross sections through the actuating device according to the invention with a gas exchange valve of a reciprocating piston internal combustion engine as a control element;
• 5 shows the actuating device according to the invention in cross section with a flat slide valve as a control element;
• 6 shows a possibility of fastening the double anchor on the shaft of a control element;
• 7 and 8 force-displacement diagrams of the actuating device according to the invention.

The actuating device according to the invention is described in the examples only on control elements which are used in internal combustion engines. However, it is not restricted to this, but it is quite generally possible to equip all oscillatingly movable control elements, which only have to have two discrete positions, with the actuating device according to the invention.

The internal combustion engine shown schematically in Figs. 1 to 4 consists of a cylinder block 1, a piston 2 with its piston rings 3, a cylinder head gasket 4, a cylinder head 5 and a poppet valve 6, which is guided in a valve guide-7 and the combustion chamber 8 together seals with its valve seat ring 9 against a gas channel 10.

The actuating device according to the invention for this poppet valve 6 consists of an armature 11, which is fastened to the shaft of the valve 6, and of two switching magnets or switching coils 12, 13, of which the switching coil 12 is designed as a closing coil and the switching coil 13 as an opening coil. A spring system, which consists of a compression spring 16 and a compression spring 17, acts on the armature 11, so that the spring system 16, 17 forms a spring-mass system with the poppet valve 6 and the armature 11 fastened thereon. The compression spring 17 is the valve spring known per se, which exerts a force in the closing direction on the poppet valve 6. The spring 16 is arranged such that it exerts a force on the poppet valve 6 in the opening direction. The compression spring 16 interacts with a prestressing anchor 15 which belongs to a prestressing coil 14 and forms a tensioning device. In the example according to FIG. 1, the preload anchor 15 bears against the preload coil 14, so that the compression spring 16 is tensioned. For this it is necessary that the bias coil 14 is energized. So that the poppet valve 6 remains in the position shown, it is also necessary that the closing coil 12 is energized so that the armature 11 is held on it against the force of the compression spring 16. The position of the actuating device shown in FIG. 1 corresponds to an operating position, namely the operating position poppet valve 6 closed. In this position, the valve spring 17 has its greatest length and accordingly exerts the least force on the armature 11.

The spacer sleeve 18 and the magnetic cover 19 serve to fasten the switching coils 12, 13 and the biasing coil 14 in the cylinder head 5, which is closed by the cover 20 at the top.

The mode of operation of the device according to the invention will be explained in more detail with reference to the diagrams in FIGS. 7 and 8. In FIG. 7, the forces in the closing direction are denoted by + and in the opening direction by - on the ordinate. The possible stroke of the poppet valve 6 is entered on the abscissa. 8 also shows the acceleration and the speed when opening, which are also entered positively in the closing direction, on the ordinate.

4 is switched off, i.e. if the switching coils 12, 13 and the biasing coil 14 are not energized, the biasing armature 15 is at rest, i.e. that it comes up against the magnetic ceiling 19. As a result, the compression spring 16 is relaxed, so that the poppet valve 6 with the armature is pressed by the valve spring 17 against the switching coil 12 designed as a closing coil. As a result, the combustion chamber 8 is closed.

To switch on the actuating device according to the invention - since the bias coil 14 has a substantially higher inductance than the two switching coils 12, 23 - all three coils are excited simultaneously. Due to the low inductance of the switching coil 12, this builds up its magnetic field faster than the bias armature 15 can be attracted by the bias coil 14. The armature 11 thus remains on the switching coil 12, so that the poppet valve 6 remains closed. In FIG. 7, this means that the spring system (curve 74) exerts a negative force on the armature 11 in the closing direction, which, however, is less than the holding force of the switching coil 12 (curve 75). In the closed position of the poppet valve 6, the force exerted by the switching coil 13 (opening coil) in the closing direction is practically zero (curve 76).

To open the poppet valve 6, the switching coil 12 is briefly switched off. The full force of the spring system (FIG. 7) thus acts in the opening direction, so that the armature 11 accelerates in the opening direction with the poppet valve 6 becomes. As shown in FIG. 7, the switching coil 12 can be switched on again immediately afterwards, since after a short stroke of the poppet valve 6 the attraction force of the switching coil 12 is less than the opening force of the spring system. As FIG. 7 further shows, practically no force acts on the moving poppet valve 6 at half the stroke. The entire potential energy present in the closing direction of the valve has thus been converted into kinetic energy. This causes (FIG. 8) that the poppet valve 6 with its armature 11 is moved beyond half the stroke (curve 79). The speed (curve 78) has its greatest value at half the stroke.

After exceeding half the stroke, the valve spring 17 acts decelerating (at the same time, the force of the switching coil 13 on the armature 11 increases with increasing distance from the half stroke). This means that the acceleration of the poppet valve 6 and its speed decrease. As curve 79 clearly shows for the acceleration, this reverses shortly before reaching the open position. This means that the poppet valve 6 is braked and reaches the open position, with the result that a hard impact of the armature 11 on the switching coil 13 is avoided.

FIG. 2 differs from the embodiment according to FIG. 1 in that the springs 16, 17 are arranged within the switching coils 12, 13, while in FIG. 1 they are arranged within the laminated cores interacting with the switching coils.

3, the two springs 16, 17 enclose the switching coils 12, 13. Another difference is that the bias anchor 15.3 serves to receive the bias coil 14 and the switching coil 12. It is therefore necessary that the armature 11 in its rest position is pressed by the valve spring 17 against a bushing 21 which is held in position by the magnetic cover 19.

Fig. 4 shows a further alternative arrangement of the springs 16, 17. These are arranged outside the switching coils 12, 13. The bias anchor 15.4 of the relaxing spring 16 is pressed against the magnetic cover 19. As a result, almost the full force of the valve spring 17 acts on the armature 11, so that the armature 11 and thus the poppet valve 6 remain in their closed position.

In Fig. 5 the actuating device according to the invention is shown using a flat slide. It does not differ in structure and mode of operation from the arrangements previously described. The flat slide valve is known in its structure and mode of operation from DE-A No. 2929195 and is therefore not described in detail.

In Fig. 6, an elastic fastening possibility of the armature 11 on the stem of the control element, here the poppet valve 6, is recorded. The armature 11 is clamped between the plate springs 22 and 23. The plate springs 22 and 23 are preloaded and are fixed on the stem of the poppet valve by the insert rings 24 and 25, which are secured against falling out by locking rings 26 and 27. The plate springs 22 and 23 have a high spring stiffness, so that the relative movements between the stem of the poppet valve 6 and the armature 11 are dampened by the friction of the plate springs 22 and 23 on the armature 11.

Claims (11)

1. An electro-magnetically operating adjusting device for oscillatory control elements (6) in displacement machines, in particular for slide-type and lift-type valves, comprising a spring-mass system (6,11,16,17) which comprises the control element (6) and a spring system (16,17) which is in operative connection therewith and preferably comprises two springs acting oppositely to each other, and two electrically operating switching magnets (12, 13), by way of which the control element (6) can be moved into two discrete oppositely disposed switching positions and held there by one of the switching magnets (12 and 13 respectively), characterized in that a clamping device is connected to the spring-mass system (6, 11, 16, 17) in such manner that the static rest position of the spring-mass system (6,11,16,17) can be shifted from a substantially median position between the switching positions of the switching magnets (12, 13) into another location, preferably disposed in the zone of one of the switching positions of the switching magnets (12, 13).

2. An electro-magnetically operating adjusting device according to Claim 1, characterized in that the clamping device has at least two discrete positions, the static rest position of the spring-mass system (6, 11, 16, 17) lying in the substantially median position between the switching positions of the switching magnets (12,13) in the first position of the clamping device, and in the zone of one of the switching positions of the switching magnets in the second position of the clamping device.

3. An electro-magnetically operating adjusting device according to one of Claims 1 or 2, characterized in that the clamping device is designed as an electromagnet (biasing coil 14, armature 15).

4. An electro-magnetically operating adjusting device according to Claim 3, characterized in that the electromagnet (14,15) of the clamping device is switched in in the first position and cut out in the second position.

5. An electro-magnetically operating adjusting device according to one of Claims 3 or 4, characterized in that the electromagnet (14,15) of the clamping device can be energized more slowly than the switching magnets (12, 13).

6. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that the forces of the switching magnets (12, 13) are greater than the opposing forces of the spring system (springs 16, 17) only shortly before reaching the switching positions.

7. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that a single armature (11), which is connected to the control element (disc valve 6), is arranged between the two switching positions of the switching magnets (12, 13).

8. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that the springs (16, 17) engage the armature (11).

9. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that, when the adjusting device is in operation, both switching magnets (12,13) are energized, and in that the switching magnets (12, 13), against which the armature bears, can be briefly cut out to move the control element (disc valve 6).

10. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that the armature (11) can be held on the control element (disc valve 6) by way of resilient components (disc springs 22, 23) having high rigidity.

11. An electro-magnetically operating adjusting device according to one of the preceding claims, characterized in that damping elements are provided between the armature (11) and the control element (disc valve 6).

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