EP1479880B1 - Valve drive with electromagnets and permanent magnets - Google Patents

Description

The present invention relates to an electric valve train for internal combustion engines according to the preamble of claim 1.

Such a valve train is off PATENT ABSTRACTS OF JAPAN Bd 2000, No. 03, 30 March 2000 (2000-03-30 ) JP 11 350929 A (TOYOTA MOTOR CORP; TOYOTA CENTRAL RES & DEV LAB INC.), 21 December 1999 (1999-12-21), PATENT ABSTRACTS OF JAPAN Bd 1998, No. 06, 30 April 1998 (1998-04-30 ) JP 10 047028 A (SUZUKI MOTOR CORP; 17 February 1998 (1998-02-17) and the EP 1 264 969 A2 known. The technical background also includes the U.S. 4,829,947 ,

The more distant technical background also includes the DE 1 539 731 ,

Another valve train is from the De 197 23 405 A1 known to be related to FIG. 5 is described. In conventional engines, the valves are mechanically controlled by a camshaft driven by the crankshaft. Electrically controlled valves have been researched for quite some time, as they promise a higher power output with lower fuel consumption. In electric valve spools, there are two basic variants, namely so-called lifting actuators, in which the actuators are actuated by solenoid valves for valve control and so-called rotary actuators, in which an acting on a cam electric motor is provided for valve actuation. In electric valve trains with Hubaktuatoren an axially displaceable armature is provided, which is biased by springs and held in a central position. The anchor has an anchor plate. On both sides of the anchor plate an electromagnet is arranged in each case. By energizing one or the other electromagnet, a magnetic field can be generated in each case, which pulls the armature in the one or in the other direction. The preloaded by the springs anchor represents a spring mass oscillator.

During a combustion cycle, the armature must be held during most of the cycle for most of the cycle time in one or the other end position where the armature plate abuts one or the other of the electromagnets. In the end positions, the valve associated with the lift actuator is either fully open or fully closed. In order to hold the armature in one or in the other end position, the associated electromagnet must be energized with a relatively large holding current. Overall, therefore, a relatively high electrical "holding power" is required.

To reduce the electrical holding power was in the above-mentioned DE 197 23 405 A1 proposed to arrange permanent magnets on the electromagnet, whose magnetic field is rectified to the magnetic field of the associated electromagnet. Due to the force exerted by the permanent magnet on the armature magnetic forces the magnetic field of the associated electromagnet is supported in the respective holding position, so that the power required to hold the armature current is lower. In the DE 197 23 405 A1 the permanent magnets are arranged laterally on pole pieces of the electromagnets. That is not without problems. In Hubaktuatoren namely significant mechanical loads can occur, especially vibration loads. Individual components, such as the permanent magnets, must be very firmly attached to the yoke of the associated electromagnet to prevent detachment due to mechanical stress in continuous operation.

The object of the invention is to provide a Hubaktuator for an electric valve train with electric and permanent magnets, in which the permanent magnets are magnetically favorable, mechanically fixed and space-saving.

This object is solved by the features of patent claim 1. Advantageous embodiments and further developments of the invention can be found in the dependent claims.

The invention is based on a known electric valve drive for internal combustion engines, which has a displaceable armature with an armature plate and a first and a second electromagnet, the both sides are arranged with respect to the anchor plate. The electromagnets each have a yoke formed from a laminated core and an electric coil arranged thereon. By energizing the coil of an electromagnet, a magnetic field is generated, which pulls the armature in the direction of a first end position and by energizing the coil of the other electromagnet, a magnetic field is generated, which pulls the armature in the opposite direction to a second end position. To reduce the holding current, which is required to hold the armature in one or the other end position, at least one permanent magnet is arranged on at least one, preferably on both yokes. The permanent magnet (s) attracts or attracts the armature when it is in the vicinity of the associated electromagnet.

The at least one permanent magnet is arranged "behind the coil" of the associated electromagnet. "Behind the coil" means that the at least one permanent magnet is arranged on a side facing away from the armature plate of the coil of the associated electromagnet.

The essence of the invention is that the coil and the at least one permanent magnet are cast into the yoke.

Preferably, the yoke, on which the at least one permanent magnet is arranged, viewed from the armature plate, in the region "behind" the coil, a recess in which the at least one permanent magnet is arranged. The at least one permanent magnet is thus "positively" embedded in the yoke.

It is particularly advantageous when the at least one permanent magnet, viewed from the armature plate, is arranged directly in the region behind the turns of the coil. This results in a "magnetic circuit" with relatively low magnetic resistance.

As already mentioned, occur in continuous operation on Hubaktuator considerable mechanical stress, in particular vibrations. For this reason, it is necessary that the Hubaktuator is compact and robust as possible. To achieve this, the coil of the electromagnet or is positively arranged between pole pieces of the associated yoke. Also, the at least one permanent magnet is arranged in a form-fitting manner in a recess of the respective yoke. The coil and the at least one permanent magnet are cast in the yoke. That is, between the yoke, coil and permanent magnet, a curing binder, such as epoxy resin, poured. After the binder has cured, a very compact, robust unit is obtained.

Preferably, the yokes of the electromagnet are also arranged in a housing. For reasons of strength, it is advantageous if the yokes are also cast in the housing. The "housing" is formed in a real engine through the cylinder head. In order to further improve the mechanical connection of the yoke to the surrounding housing, one or more undercut elements can be arranged on the outside of the yokes, which are filled in the housing of housing material when the yokes are poured into the housing. As a result, a positive connection of the yokes is achieved with the housing.

Preferably, the at least one permanent magnet is arranged in the region between the coil and the at least one undercut element. The undercut element projecting from the outer circumference of the yoke constitutes a "material accumulation" which favors the magnetic flux in the region of the at least one permanent magnet.

As already indicated, one or more, e.g. be provided two permanent magnets per yoke. The two permanent magnets may be spaced apart as seen in their north-south direction. Furthermore, it can be provided that the permanent magnets are arranged offset from one another in a direction transverse to their north-south direction.

Figur 1

das Grundprinzip eines Hubaktuators gemäß der Erfindung;

Figuren 2, 3

verschiedene Varianten eines Elektromagneten der Hubaktuoranordnung im Querschnitt;

Figuren 4a, 4b, 5, 6

verschiedene Anordnungsmöglichkeiten der Permanentmagneten im Joch des zugeordneten Elektromagneten.

In the following the invention will be explained in connection with the drawing. Show it:

FIG. 1

the basic principle of a Hubaktuators according to the invention;

FIGS. 2, 3

different variants of an electromagnet of Hubaktuoranordnung in cross section;

FIGS. 4a, 4b, 5, 6

various possible arrangements of the permanent magnets in the yoke of the associated electromagnet.

FIG. 1 shows a Hubaktuator 1 according to the invention in a schematic representation. The lifting actuator 1 has a first electromagnet 2 and a second electromagnet 3. Further, an anchor biased by springs 4, 5 in a central position anchor, of which only an anchor plate 6 is shown here. The anchor plate 6 is arranged between the two electromagnets 2, 3. The armature further comprises a shaft, not shown here, and is arranged between an upper and lower end position axially displaceable between the two electromagnets. The electromagnets each have a formed by a laminated core yoke 7 with pole pieces 8-10. By the pole pieces 8-10 recesses 11, 12 are formed, in which a coil 13 of the electromagnet is arranged.

Seen from the anchor plate 6, the yoke 7 in the region "behind" the coil 13 recesses 14, 15, in each of which a permanent magnet 16, 17 is arranged.

In the area behind the recesses 14, 15 or the permanent magnets 16, 17 arranged therein, the yoke has on its outside two dovetail-like undercut elements 18, 19. The undercut elements 18, 19 serve primarily to connect the yoke 7, which is in a housing surrounding the yoke 7 - e.g. a cylinder head - is poured, positively and thus mechanically robust with the housing (not shown) is connected. By the undercut elements 18, 19 so a positive connection between the yoke 7 and the surrounding housing (not shown) is achieved. The electromagnet 2 shown here only schematically can be constructed very analogous to the electromagnet 3.

Due to the arrangement of the permanent magnets 16, 17 in the region of the undercut elements, the mechanical strength of the laminated yoke 7 guaranteed. The danger that the laminated yoke 7 divides into several parts, thus does not exist. Overall, the described arrangement results in a high stability with low production technical effort.

By energizing the coil 13, the armature in the direction of the electromagnet 3 can be pulled out. When the armature plate 6 is in the vicinity of the electromagnet 3, the armature plate is detected by the magnetic field of the permanent magnets 16, 17 in addition to the magnetic field generated by the coil 13. To hold the armature plate 6 in the end position in which the armature plate 6 abuts the yoke 7, therefore, a smaller holding current is required due to the permanent magnets 14, 15 than in purely electromagnetic actuation of the armature, i. if no permanent magnets were present.

As already mentioned several times, occur on a Hubaktuator in continuous operation considerable mechanical stress. In order to achieve the most robust possible arrangement, the coil 13 and the permanent magnets 16, 17 are cast in the associated recesses 11, 12 and 14, 15, for example by a curable synthetic resin, e.g. Epoxy resin.

FIG. 2 shows a variant of in FIG. 1 shown electromagnet 3 of the Hubaktuators. In this embodiment, only a single permanent magnet 16 is provided. The permanent magnet 16 is slightly wider here than in FIG FIG. 1 provided electromagnet 16. The electromagnet 16 of FIG. 2 has substantially the same width as the coil 13. Accordingly, the recesses 11 and 14 merge into each other or are formed by a single groove in the yoke 7.

FIG. 3 shows another variant of the electromagnet 3. Similarly as in FIG. 1 Here two permanent magnets 16, 17 are provided. However, these are not arranged centrally below the coil 13, but offset towards the center of the yoke 7. How out FIG. 3 it can be seen, the permanent magnets 16, 17 have a slightly smaller width than the coil 13. Accordingly, the recesses 14, 15 have a slightly smaller width than the recesses 11, 12th

The FIGS. 4a, 4b, 5, 6 show plan views of different variants of the invention. In the embodiment of FIGS. 4a, 4b the permanent magnets 14, 15 are arranged centrally below the recesses 11, 12. How out FIG. 4a It can be seen that the permanent magnets 16, 17 extend over the entire length of the yoke 7.

In the embodiment of FIG. 5 are the permanent magnets 16, 17 shorter than in the embodiment of FIGS. 4a, 4b , The permanent magnets 16, 17 are arranged centrally on the yoke 7 with respect to their longitudinal direction.

In contrast, the permanent magnets 16, 17 in the embodiment of FIG. 6 offset in its longitudinal direction at the yoke 7 is arranged.

Claims (9)

1. An electric valve drive for internal combustion engines, comprising a movable armature with an armature plate (6), a first electromagnet (2) disposed on one side of the armature plate (6), and a second electromagnet (3) disposed on the other side of the armature plate (6), wherein
   each electromagnet (2, 3) has a yoke (7) and a coil (13) mounted thereon, and the coil (13) of one electromagnet (2) is energised so as to generate a magnetic field which pulls the armature in the direction of its first end position whereas the second electromagnet (3) is energised so as to generate a magnetic field which pulls the armature in the opposite direction to a second end position, wherein
   at least one permanent magnet (16, 17) is disposed on at least one yoke (7) and attracts the armature, especially when the armature plate (6) is near the associated electromagnet (3), wherein the at least one permanent magnet (16, 17) is disposed on a side of the coil (13) remote from the armature plate (6) of the associated electromagnet (3), wherein the yoke (7) on which the at least one permanent magnet (16, 17) is disposed has a recess (11, 12) in which the associated coil (13) is disposed, and a recess (14, 15) holding the at least one permanent magnet (16, 17) is formed in the yoke (7) in a region behind the coil (3) relative to the armature plate (6),
   characterised in that
   the coil (3) and the at least one permanent magnet (16, 17) are fixed to the associated yoke (7) by a binder which is hardened after being poured in between the yoke (7), the coil (13) and the permanent magnet (16, 17).
2. An electric valve drive according to claim 1, wherein the at least one permanent magnet (16, 17) is disposed in a region behind the turns of the coil (13), relative to the armature plate (6).
3. An electric valve drive according to claim 1 or claim 2, wherein the yoke (7) is disposed in a casing.
4. An electric valve drive according to any of claims 1 to 3, wherein the yoke (7) is embedded in a casing.
5. An electric valve drive according to claim 4, wherein the yoke (7) has at least one undercut element (18, 19) projecting from its outside, wherein an undercut formed by the undercut element (18, 19) is filled with the casing material and thus positively connected to the casing.
6. An electric valve drive according to claim 5, wherein the at least one permanent magnet (16, 17) is disposed in the region between the associated coil (13) and the at least one undercut element (18, 19).
7. An electric valve drive according to any of claims 1 to 6, wherein two permanent magnets (16, 17) are mounted on at least one of the two yokes (7) of the electromagnets (2, 3).
8. An electric valve drive according to claim 7, wherein the two permanent magnets (16, 17) are spaced apart from one another in their north-south direction.
9. An electric valve drive according to claim 7 or claim 8, wherein the two permanent magnets (16, 17) are offset from one another in a direction transversely of their north-south direction.

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