Electromagnetic actuator

Abstract

An electromagnetic actuator having at least one electromagnetic actuator unit, the actuator unit comprising a coil and a plunger, which plunger is axially movable relative to the coil via energization of the coil, and the actuator unit being arranged in a housing. In order to achieve a particularly simple design, the plunger is arranged approximately coaxially with the coil according to the invention.

Claims

1. An electromagnetic actuator comprising: at least two electromagnetic actuator units, each electromagnetic actuator unit including: a coil; a core concentrically arranged within and rigidly connected to the coil; a plunger coaxially aligned with the coil and the core, the plunger configured to translate axially in relation to the coil and the core based on an energization of the coil; a stop rigidly connected to the core such that the plunger rests against an at least partially spherical surface of the stop when the plunger is in a first end position proximate to the core; and a plunger guide coaxially aligned with the coil and the core, the plunger guide configured to slidably receive the plunger, wherein each plunger guide is further configured to move in relation to one another.

2. The electromagnetic actuator according to claim 1, wherein: the at least two electromagnetic actuator units are arranged in a common housing.

3. The electromagnetic actuator according to claim 1, wherein: in each electromagnetic actuator unit, the plunger is further configured to switch between the first end position proximate to the core, and a second end position away from the core; and each plunger rests against a stop arranged at each end position.

4. The electromagnetic actuator according to claim 3, wherein: in each electromagnetic actuator unit, the stop is arranged in a pass-through hole formed in the core.

5. The electromagnetic actuator according to claim 1, wherein: each electromagnetic actuator unit further includes a permanent magnet arranged on the plunger.

6. The electromagnetic actuator according to claim 5, wherein: in each electromagnetic actuator unit, the permanent magnet is magnetically separated from the core in an axial direction only through an air gap.

7. The electromagnetic actuator according to claim 1, wherein: each electromagnetic actuator unit further includes an anchor plate arranged on the plunger.

8. The electromagnetic actuator according to claim 1, wherein: each electromagnetic actuator unit further includes a permanent magnet and an armature element arranged on the plunger, the armature element protruding radially beyond the permanent magnet.

9. The electromagnetic actuator according to claim 8, wherein: each electromagnetic actuator unit further includes a spring configured to connect the plunger to the coil.

10. The electromagnetic actuator according to claim 9, wherein: in each electromagnetic actuator unit, the spring, the armature element, the permanent magnet, and the coil cooperate so as to move the plunger a predefined minimum distance to the first end position as the plunger approaches the first end position when the coil is de-energized.

11. The electromagnetic actuator according to claim 9, wherein: in each electromagnetic actuator unit, the spring, the armature element, the permanent magnet, and the coil cooperate so as to move the plunger from the first end position to a second end position away from the core.

12. The electromagnetic actuator according to claim 9, wherein: in each electromagnetic actuator unit, the spring, the armature element, the permanent magnet, and the coil cooperate so as to maintain the plunger in a second end position away from the core independently of the energization of the coil such that the plunger is enabled to move out of the second end position only when an additional force is applied to the plunger.

13. The electromagnetic actuator according to claim 1, wherein: each electromagnetic actuator unit further includes a spring configured to connect the stop to the coil.

14. The electromagnetic actuator according to claim 1, wherein: in each electromagnetic actuator unit, the stop rests against a yoke disk fixed to the core.

15. The electromagnetic actuator according to claim 14, wherein: in each electromagnetic actuator unit, the stop is arranged in a pass-through hole formed in the core so as to extend beyond first and second axial ends of the core.

16. The electromagnetic actuator according to claim 1, wherein: each plunger guide is arranged in a separate guide body which are configured to move in relation to each other.

17. The electromagnetic actuator according to claim 16, wherein: in each electromagnetic actuator unit, the plunger includes a central taper that remains within the plunger guide as the plunger translates.

18. The electromagnetic actuator according to claim 1, wherein: in each electromagnetic actuator unit, a maximum external diameter of the core is less than or equal to an inner diameter of the coil.

19. The electromagnetic actuator according to claim 18, wherein: each electromagnetic actuator unit further includes a component made of a magnetically conductive material arranged on at least one axial end of the core, the component protruding radially beyond the core.

20. The electromagnetic actuator according to claim 19, wherein: each component is a plate-shaped component.

21. The electromagnetic actuator according to claim 1, wherein: each stop is a ball or a pin.

22. A camshaft actuator for adjusting an axially movable sleeve on a camshaft of an internal combustion engine, the camshaft actuator comprising the electromagnetic actuator according to claim 1.

23. The electromagnetic actuator according to claim 1, wherein: each stop comprises: a ball; or a pin including a hemispherical end surface.

Description

(1) Further features, advantages and effects of the invention emerge from the exemplary embodiment are shown below. In the drawings to which reference is made:

(2) FIG. 1 shows an actuator according to the invention in a sectional illustration;

(3) FIG. 2 shows a diagram from which forces acting on a plunger can be inferred over a stroke;

(4) FIGS. 3 and 4 show further embodiments of an actuator according to the invention in sectional illustration.

(5) FIG. 1 shows a sectional view of an actuator 1 according to the invention. As it can be seen, two actuator units are provided in a common housing 4 in the illustrated embodiment, each actuator unit having a coil 2, a core 7 around which coil 2 is arranged, a plunger 3 extending along a longitudinal axis 17, a spring 10 which connects the plunger 3 to the core 7, has a permanent magnet 6 and an armature element formed by an armature plate 9.

(6) A magnetic circuit, through which plunger 3 can be actuated by means of coil 2, is closed through a jacket 15 in which coil 2 is arranged and through which the coil 2 is magnetically connected to the armature element on plunger 3.

(7) As shown, in order to ensure a small distance between the plungers 3, it is advantageous if jacket 15 is arranged to enclose both cores 7, but no jacket 15 is positioned between core 7.

(8) As it can also be seen, plungers 3 are each arranged coaxially to the longitudinal axes 17 of coils 2 or centrally to coils 2. The longitudinal axis 17 of plunger 3 thus coincides with the longitudinal axes 17 of plunger 3. As a result, when the same is actuated by means of a magnetic force caused by coils 2, no torque acts on plunger 3 about an axis transverse to the longitudinal axis 17, which is why the plunger guide 12 can be designed in a particularly simple manner.

(9) In order to be able to manufacture actuator 1 particularly cost-effectively, core 7 arranged in coil 2 has an essentially cylindrical external contour, with a maximum external diameter 28 of core 7 corresponding approximately to a minimum inner diameter of coil 2. It goes without saying that coil 2 here is understood to mean not only the windings themselves, but also a component carrying the windings which is located between core 7 and the windings themselves.

(10) In order to achieve a low magnetic resistance between core 7 and jacket 15, there are both on an end of core 7 on the plunger side and on an end of core 7 opposite the end on the plunger side

(11) Yoke disks 27, which protrude radially beyond core 7 relative to the longitudinal axis 17, are arranged to establish a magnetic connection between core 7 and jacket 15. Yoke disks 27 are made from an easily magnetizable plate material and have an approximately circular cross-section in a section perpendicular to longitudinal axis 17.

(12) Anchor plate 9 protrudes on each plunger 3 in a plane perpendicular to longitudinal axis 17 or perpendicular to the image plane beyond the permanent magnets 6 of the respective plungers 3, so that a magnetic circuit can close over anchor plate 9. Permanent magnets 6 are only separated from core 7 by an air gap 8. An approximately hollow cylindrical protective sleeve 13 is arranged around each permanent magnet 6. A magnetic flux produced by means of coil 2 and the magnetic circuit thus runs essentially through core 7, plunger 3, armature plate 9 and jacket 15.

(13) As a result, a force can be applied to the armature element or the respective plunger 3 by energizing coil 2, the force of which moves plunger 3 away from the end position 23 near the core.

(14) Of the two actuator units shown in FIG. 1, the plunger 3 of the actuator unit shown on the left is in an end position 23 near the core and plunger 3 of the actuator unit shown on the right on FIG. 1 is in an end position 24 away from the core. In the end position 23 near the core, plunger 3 rests against a stop device designed as a ball 5, which in turn is positioned in core 7 so that the core near the end position 23 of plunger 3 is defined in a simple and at the same time highly accurate manner. Plungers 3 make contact with the ball 5 at an approximately circular disk-shaped, essentially flat, contact surface 16, so that a point-like contact results. In order to be able to ensure the exact position of the end position 23 near the core over a long period of time or a desired service life of a motor in which actuator 1 is used, the stop device is made of a material with a high hardness or a hardness higher than core 7.

(15) Plungers 3 are guided in plunger guides 12, which are formed by cylindrical bores in a guide body 18. Plungers 3 also have a cylindrical external contour in some areas, which interacts with the plunger guides 12, so that plungers 3 can only be moved translationally in the direction of longitudinal axis 17 and rotationally about longitudinal axis 17, but beyond that there is no movement of plungers 3 relative to the housing 4 or to guide body 18.

(16) As can also be seen, plungers 3 in plunger guides 12 have tapers 14 in which oil can be collected in order to lubricate a movement of plungers 3 in the guides and thus to minimize wear.

(17) Plungers 3 are connected to core 7 through spring 10 and permanent magnet 6 in such a way that spring 10 exerts a force on plunger 3 in stroke direction 25, i.e. from end position 23 near the core in the direction of end position 24 away from the core parallel to longitudinal axes 17, is exercised when plungers 3 are in the end position 23 near the core. In the end position 23 close to the core, permanent magnets 6 apply a force counteracting the spring force 20 to plunger 3, the magnitude of which is greater than spring force 20, so that plunger 3 is in a current-less state of coil 2 due to a total force of magnetic force and spring force 20 and held in end position 23 near the core. The total force thus acts against stroke direction 25 when coil 2 is de-energized.

(18) In order to operate an actuator unit and move the corresponding plunger 3 out of the end position 23 near the core, an electrical voltage is applied to the coil 2 of this actuator unit, creating a magnetic flux in the magnetic flux formed by the core 7, casing 15, plunger 3 and armature plate 9 Circle causes a force on the plunger 3 in the stroke direction 25, so that the total force acting on the plunger 3 points in the stroke direction 25 and the plunger 3 is moved from the end position 23 near the core.

(19) When actuated accordingly, plunger 3 is moved into end position 24 away from the core, in which plunger 3 rests against a stop formed by metallic plate 11.

(20) The longitudinal axes 17 of both plungers 3 are approximately parallel, as shown, and when the actuator 1 is used, they are typically less than 25 mm, in particular 6 mm to 15 mm, spaced from one another. With the design of actuator 1 according to the invention, a force sufficient for camshaft adjustment can be provided despite the small distance.

(21) FIG. 2 schematically shows the forces acting on a plunger 3 of an actuator unit as a function of a stroke of plunger 3 starting from the end position 23 near the core in stroke direction 25 to an end position 24 of plunger 3 away from the core.

(22) Both a magnetic force and a force of permanent magnet 6 and a magnetic force caused by energizing coil 2 on plunger 3, as well as a spring force 20 resulting from spring 10, the magnetic force being shown in solid line for a situation in which coil 2 is not energized and in a broken line for a situation in which coil 2 is energized. The solid line thus represents a current-less magnetic force 21, which is caused by permanent magnet 6 alone, and the broken line represents the energized magnetic force 22, which is a total force of permanent magnet 6 and the magnetic force formed by the energization of coil 2 on Plunger 3. In the case of spring force 20, a force in the stroke direction 25 is shown as a positive force, while in the case of the de-energized magnetic force 21 and energized magnetic force 22 positively represented forces aligned against stroke direction 25. On the ordinate of the diagram, values in the stroke direction 25 with respect to spring force 20 and values against the stroke direction 25 with respect to the magnetic forces are thus shown.

(23) As it can be seen, a current-less magnetic force 21 holding plunger 3 in the end position 23 near the core, that is to say with a stroke of 0 mm, is greater than spring force 20 during this stroke. When coil 2 is de-energized, plunger 3 is therefore held in end position 23 near the core by permanent magnet 6. As shown, spring force 20 decreases over the stroke and approaches zero in end position 24 of plunger 3 away from the core. This ensures that when plunger 3 moves, spring 10 is never without a defined position between core 7 and plunger 3 or is loose, which could lead to the development of noise and wear.

(24) If coil 2 is energized, plunger 3 is reduced in the area close to the magnetic force holding the end position 23 is less than the amount of spring force 20, so that the current-less magnetic force 21 acts, whereby the plunger 3 moves away from end position 23 near the core when coil 2 is energized by spring force 20.

(25) As it can also be seen, plunger 3 is pulled near an end position 24 away from the core into end position 24 away from the core. This is done by a magnetic force brought about by permanent magnet 6, by means of which plunger 3 is pulled to a plate 11 which forms a stop in the end position 24 away from the core.

(26) Plunger 3 is thus positionally stable both in end position 23 near the core and in end position 24 away from the core when the coil 2 is de-energized. In order to move plunger 3 away from end position 24 away from the core back into end position 23 near the core, plunger 3 is moved, for example, by means of a sleeve into which plunger 3 engages in a camshaft actuator, at least up to a minimum return position 19 counter to stroke direction 25. From this minimum return position 19, the magnetic force of permanent magnet 6 pulling plunger 3 into end position 23 near the core when coil 2 is de-energized, i.e. the de-energized magnetic force 21 against the stroke direction 25 is greater than spring force 20 in stroke direction 25, so that a resulting force acts against stroke direction 25 on plunger 3 and plunger 3 is pulled from the minimum return position 19 into end position 23 near the core when coil 2 is de-energized.

(27) FIG. 3 shows a further actuator 1 according to the invention, which is basically constructed similarly to the actuator 1 shown in FIG. 1, but in contrast to the actuator 1 shown in FIG. 1 has a pin 26 as a stop device. As shown, the stop device embodied as pin 26 is supported here on one behind the core 7 or on a yoke disk 27 arranged opposite a rear side of the core 7 opposite an end of core 7 on the side of the plunger, so that core 7 is not mechanically stressed when plunger 3 strikes. In order to be able to transmit a force from plunger 3 to yoke disk 27 when plunger 3 strikes, without mechanically stressing the core 7, a pass-through hole is provided in the core 7 in this embodiment. In the embodiment shown, pin 26 is positioned in the pass-through hole and protrudes from core 7 on both sides, without

(28) contacting core 7 or a yoke disk 27 arranged at an end of core 7 on the plunger side in a manner suitable for the transmission of forces in the direction of longitudinal axis 17. Furthermore, a spring 10 is also provided in this embodiment, which is also supported here on yoke disk 27 and penetrates the pass-through hole in the core. Alternatively, spring 10 could of course also be supported on core 7, for example on a shoulder in the pass-through hole in core 7. This design achieves an increased service life because core 7 is not mechanically stressed with every stop of plunger 3. The pass-through hole can lead to a magnetic weakening 7 of core 7 or to an increased magnetic resistance of core 7, which are accepted in order to minimize the mechanical load.

(29) FIG. 4 shows a further actuator 1 according to the invention, which is constructed largely similar to that shown in FIG. 3. In a departure from the actuator 1 shown in FIG. 3, plunger guides 12 are arranged here in separate guide bodies 18 which are connected to housing 4 through plate 11. Guide bodies 18 are connected to plate 11 with little mobility or play, so that the actuator 1 can be connected in a simple manner to a connection component of an engine, typically a cylinder head cover, even if there are manufacturing tolerances in the engine as well as in the case of actuator 1 are used in the most unfavorable manner or a mechanical interface on the motor has position and/or position deviations. Guide bodies 18 and thus an alignment of the longitudinal axes 17 of plungers 3 can thus be achieved by the movable connection of guide bodies 18 to housing 4 or on plate 11 can be easily adapted to the relevant conditions. It goes without saying that guide bodies 18 can then also be moved relative to one another and that the longitudinal axes 17 of plungers 3 may no longer be exactly parallel.

(30) With an actuator 1 according to the invention, a bistable actuator 1 for camshaft adjustment is achieved in a particularly simple manner, which ensures a particularly simple and therefore inexpensive guidance of plungers 3.