Electromagnetic camshaft adjuster

Abstract

A electromagnetic camshaft adjuster comprising: an armature unit which can be moved relative to a pole core when a stationary coil unit is energized and which has an armature plunger; and a permanent magnet unit by means of which the armature unit is held in a rest position when the coil unit is not energized; and a spring element between the pole core and the armature unit to force the armature unit axially away from the pole core, the spring force of the spring element being chosen smaller than the holding force of the permanent magnet unit when the coil unit is not energized. The permanent magnet unit is stationarily arranged between a housing cover and the pole core, the armature plunger is rotationally arranged, and the spring element is supported on a part of the armature unit which is rotationally fixedly mounted.

Claims

1. An electromagnetic camshaft adjuster, comprising: a movable armature unit movable relative to a pole core by exciting a stationary coil unit with a current; an armature plunger; a permanent magnet unit, through which the armature unit is held in a resting position in a non-excited condition of the coil unit; a spring unit between the pole core and the armature unit, the spring unit providing a spring force to force the armature unit axially away from the pole core, wherein the spring force of the spring unit is dimensioned so as to be smaller than a holding force of the permanent magnet unit in the non-excited condition of the coil unit; wherein the permanent magnet unit is provided to be stationary between a housing cover and the pole core, wherein the armature plunger is provided in an armature so as to be rotatable, wherein the spring unit is supported on the armature, and wherein the armature unit is axially movable in a guide bushing, and the armature unit is guided in the guide bushing in a rotationally fixed manner.

2. The electromagnetic camshaft adjuster according to claim 1, wherein the armature unit has a pot-shaped armature with a bottom in which an opening is provided, and wherein the armature plunger extends through the opening.

3. The electromagnetic camshaft adjuster according to claim 2, wherein the spring unit is a compression spring that is supported in the bottom of the armature.

4. The electromagnetic camshaft adjuster according to claim 1, wherein a gap is provided between the pole core and the armature unit, wherein the gap is formed to increase towards a central axis (X) of the electromagnetic camshaft adjuster.

5. The electromagnetic camshaft adjuster according to claim 1, wherein the pole core and a yoke unit are connected to each other in a stationary manner via a sleeve.

6. The electromagnetic camshaft adjuster according to claim 5, wherein the pole core and the yoke unit are welded together with the sleeve.

7. The electromagnetic camshaft adjuster according to claim 2, wherein the armature plunger is encompassed and fixed in the bottom of the pot-shaped armature by a retaining disc.

8. A camshaft adjuster, comprising: a movable armature unit comprising: a pot-shaped armature having a bottom with an opening; and a rotatable armature plunger that extends through the opening, wherein the movable armature unit is movable relative to a pole core by exciting a stationary coil unit with a current and wherein, in a non-excited condition of the stationary coil unit, the movable armature unit is held in a resting position by a magnet unit between a housing cover and the pole core; a spring unit located between the pole core and the movable armature unit and supported on the armature, the spring unit biased with a spring force to force the movable armature unit axially away from the pole core, wherein the spring force is less than a holding force of the magnet unit in the non-excited condition of the stationary coil unit; a guide bushing; and wherein the movable armature unit is axially movable in the guide bushing while being rotationally fixed with respect to the guide bushing.

9. The camshaft adjuster according to claim 8, wherein the rotatable armature plunger is encompassed and fixed in the bottom of the pot-shaped armature by a retaining disc.

10. The camshaft adjuster according to claim 8, further comprising: a yoke unit; and a sleeve; wherein the yoke unit and the pole core are connected to each other in a stationary manner via the sleeve.

11. The camshaft adjuster according to claim 10, wherein the pole core and the yoke unit are welded together with the sleeve.

12. An electromagnetic camshaft adjuster, comprising: a movable armature unit movable relative to a pole core by exciting a stationary coil unit with a current; an armature plunger; a permanent magnet unit, through which the armature unit is held in a resting position in a non-excited condition of the coil unit; a spring unit between the pole core and the armature unit, the spring unit providing a spring force to force the armature unit axially away from the pole core, wherein the spring force of the spring unit is dimensioned so as to be smaller than a holding force of the permanent magnet unit in the non-excited condition of the coil unit; wherein the permanent magnet unit is provided to be stationary between a housing cover and the pole core, wherein the armature plunger is provided in an armature so as to be rotatable, wherein the spring unit is supported on the armature, wherein a gap is provided between the pole core and the armature unit, wherein the gap is formed to increase towards a central axis (X) of the electromagnetic camshaft adjuster, and wherein the armature unit is axially movable in a guide bushing, and the armature unit is guided in the guide bushing in a rotationally fixed manner.

13. The electromagnetic camshaft adjuster according to claim 12, wherein the pole core and a yoke unit are connected to each other in a stationary manner via a sleeve.

14. The electromagnetic camshaft adjuster according to claim 13, wherein the pole core and the yoke unit are welded together with the sleeve.

15. An electromagnetic camshaft adjuster, comprising: a movable armature unit movable relative to a pole core by exciting a stationary coil unit with a current; an armature plunger; a permanent magnet unit, through which the armature unit is held in a resting position in a non-excited condition of the coil unit; a spring unit between the pole core and the armature unit, the spring unit providing a spring force to force the armature unit axially away from the pole core, wherein the spring force of the spring unit is dimensioned so as to be smaller than a holding force of the permanent magnet unit in the non-excited condition of the coil unit; wherein the permanent magnet unit is provided to be stationary between a housing cover and the pole core, wherein the armature plunger is provided in an armature so as to be rotatable, wherein the spring unit is supported on the armature, wherein the pole core and a yoke unit are connected to each other in a stationary manner via a sleeve, wherein the pole core and the yoke unit are welded together with the sleeve.

16. A camshaft adjuster, comprising: a movable armature unit comprising: a pot-shaped armature having a bottom with an opening; and a rotatable armature plunger that extends through the opening, wherein the movable armature unit is movable relative to a pole core by exciting a stationary coil unit with a current and wherein, in a non-excited condition of the stationary coil unit, the movable armature unit is held in a resting position by a magnet unit between a housing cover and the pole core; a spring unit located between the pole core and the movable armature unit and supported on the armature, the spring unit biased with a spring force to force the movable armature unit axially away from the pole core, wherein the spring force is less than a holding force of the magnet unit in the non-excited condition of the stationary coil unit; a yoke unit; a sleeve; wherein the yoke unit and the pole core are connected to each other in a stationary manner via the sleeve, and wherein the pole core and the yoke unit are welded together with the sleeve.

17. The camshaft adjuster according to claim 16, further comprising: a guide bushing; and wherein the movable armature unit is axially movable in the guide bushing while being rotationally fixed with respect to the guide bushing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The electromagnetic camshaft adjuster according to the present application will be explained in more detail below in connection with figures by way of an embodiment example, wherein:

(2) FIG. 1 shows a longitudinal section through an electromagnetic camshaft adjuster in the resting position with the coil not energised,

(3) FIG. 2 shows the electromagnetic camshaft adjuster of FIG. 1 with an extended armature plunger, and

(4) FIG. 3 shows the electromagnetic camshaft adjuster of FIGS. 1 and 2 in the returning condition, in which the camshaft presses against the armature plunger.

DETAILED DESCRIPTION

(5) In the figures following below, the same reference signs identify the same parts with the same meaning, unless otherwise specified.

(6) FIG. 1 shows the electromagnetic camshaft adjuster in a resting condition, i.e. with the exciter coil 22 not excited. It is assumed here that the armature plunger 44 is initially in its top position. In this condition, a magnetic force flux is provided by the permanent magnet unit 60, which keeps the armature unit 40 attracted to the pole core 30. Also, a gap 49 is provided between the pole core 30 and the armature unit 60, where the gap 49 is formed to increase towards a central axis (X) of the electromagnetic camshaft adjuster. It is essential here that the spring unit 70, i.e. the provided coil spring in the embodiment example, has a spring force that is dimensioned to be lower than the retaining force of the permanent magnet unit 60 in the non-excited condition of the exciter coil 22.

(7) The adapter element 14 extends through a flange 100. On this flange 100, the housing 11 of the electromagnetic camshaft adjuster 10 is seated.

(8) On the inside of the electromagnetic camshaft adjuster 10, a pole core 30 is provided at a distance from the surface of the cover 12 that faces the inside of the electromagnetic camshaft adjuster 10. This pole core 30 is directed towards the camshaft 80 and is formed with a conically tapered circumferential surface for providing a control cone in a manner that is known per se. Between the pole core 30 and the cover 12, a permanent magnet unit 60 in the form of a permanent magnet disc is provided. The cover 12, the permanent magnet unit 60 and the pole core 30 are here stationary and are placed within the housing 11 preferably without a gap relative to each other.

(9) As can be seen from FIG. 1, both the pole core 30 and the permanent magnet disc 60 are designed to be annular and have a central opening through which a spring unit 70, presently a coil spring, extends. The coil spring 70 is here oriented centrally to the central axis X and is supported at the end thereof that is shown at the top in FIG. 1 in an annular groove 12a of the cover 12. With its opposite end, the coil spring 70 is supported on the bottom 42 of a pot-shaped armature 41. From the bottom 42 of the armature 41, a peripheral wall 43 of the armature 41 extends upwards and encompasses the coil spring 70. The bottom 42 of the armature 41 has an opening 46, through which the upper end of an armature plunger 44 protrudes. This armature plunger 44 forms the above-mentioned actuator element for the camshaft 80. The armature plunger 44 is encompassed at the end thereof that protrudes through the bottom 42 of the armature 41 by a retaining disc 45 and is fixed thereby to the armature 41. This fixing is achieved by the retaining disc 45 as a result of the fact that it engages in a peripheral groove at the top end of the armature plunger 44 in a manner similar to a locking ring and interacts at the bottom end of the bottom 42 of the armature 41 with a flange 44a of the armature plunger 44 that protrudes in a circular manner.

(10) The armature 41 with its bottom 42 and its wall 43 forms, together with the armature plunger 44, an armature unit 40. The entire armature unit 40, i.e. the armature 41 and the armature plunger 44, are axially movable in the axial direction of the central axis X. This means that during an axial movement of the armature 41, the armature plunger 44 that is axially fixed to the armature is moved at the same time. To this end, the armature 41 is seated in a guide bushing 47 that allows an axial movement of the armature 41. However, the armature 41, unlike the armature plunger 44, is mounted within this guide bushing 47 so that it cannot, or almost not, rotate. To this end, for example a suitable groove-and-tongue connection is provided. Thus, the guide bushing 47 may for example have a longitudinal groove that extends parallel along the central axis X, into which a protruding longitudinal web that also extends parallel along the central axis X engages on the circumferential wall 43 of the armature 41. For the purpose of enhancing clarity, such a tongue-and-groove connection between the armature 41 and the guide bushing 47 is not shown in FIG. 1. Although in another variant the armature 41 may in principle be provided to be rotatable in relation to the guide bushing 47, as a result of the spring force of the spring unit 70, the armature 41 is axially pretensioned in such a way that the latter can be rotated only against the spring force applied by the spring unit 70. In the case of a correspondingly large dimensioning of the spring force, the armature 41 is placed so as to be virtually rotationally fixed. Compared with this, however, the armature plunger 44 can be rotated with comparative ease within the armature 41. Consequently, this solution results in the fact that the armature plunger 44 will rotate during operation, but the armature 41 will not.

(11) Thus, whilst the armature 41 is axially displaceable along the central axis X, but not rotatable, such a rotation of the armature plunger 44 is allowed and expressly provided for. To this end, the armature plunger 44 is placed in the opening 46 in the bottom 42 of the armature 41 so as to be rotatable. Such a rotatable placement of the armature plunger 44 may be achieved for example as a result of the fact that a certain play is provided between the opening 46 of the armature 41 and the armature plunger 44 on the one hand and in between the distance of the retaining disc 45 and the flange 44a.

(12) For the sake of completeness it is to be noted in connection with the representation of FIG. 1 that a flange-shaped yoke part 32 is provided which is placed so as to be stationary within the housing 11 of the electromagnetic camshaft adjuster 10 and constitutes the magnetic counterpiece to the pole core 30. The pole core 30 and the yoke part 32 are preferably fixed to a further sleeve 36, for example by welding. In addition, both the cover 12 and the yoke part 32 are sealed relative to the sleeve 36 by sealing rings 37, 38.

(13) An electromagnetic camshaft adjuster 10 as shown in FIG. 1 operates as follows. Reference is in this respect also made to the representations in FIGS. 2 and 3, which show the electromagnetic camshaft adjuster 10 in each case in different operating conditions which will be explained below. However, the known reference numerals are the same.

(14) FIG. 1 shows the electromagnetic camshaft adjuster in a resting condition, i.e. with the exciter coil 22 not excited. It is assumed here that the armature plunger 44 is initially in its top position. In this condition, a magnetic force flux is provided by the permanent magnet unit 60, which keeps the armature unit 40 attracted to the pole core 30. It is essential here that the spring unit 70, i.e. the provided coil spring in the embodiment example, has a spring force that is dimensioned to be lower than the retaining force of the permanent magnet unit 60 in the non-excited condition of the exciter coil 22.

(15) If in the next step current flows through the exciter coil 22 so that the force effected thereby counteracts the force of the permanent magnet unit 60, the force of the permanent magnet unit 60 is minimised or cancelled out, so that the spring force of the spring unit 70 is sufficient to force the armature 41 on the armature plunger 44 away. In the case of a corresponding excitation of the exciter coil 22, this can be carried out so quickly that a forcing away of the armature plunger 44 can be achieved within less than 3 ms, in order to engage in the camshaft groove 82 of the camshaft 80 and to adjust the latter correspondingly. In the maximum extended position of the armature plunger 44 as shown in FIG. 2, the force of permanent magnet unit 60 is then no longer sufficient to return the plunger 41.

(16) Such a return will not be possible until the camshaft groove 82 of the camshaft 80 forces the armature plunger 44 back, as shown in FIG. 3. As soon as the armature 41 is close enough to the pole core 30, the force flux via the permanent magnet 60 becomes so great that the armature is pulled back further into its resting position, until the latter has again reached its resting position according to FIG. 1.

LIST OF REFERENCE NUMERALS

(17) 10 Electromagnetic camshaft adjuster 11 Housing 12 Cover 12a Groove 13 Opening 14 Adapter element 20 Stationary coil unit 22 Input coil 23 Coil carrier body 30 Pole core 32 Yoke part 36 Sleeve 37 Sealing ring 38 Sealing ring 40 Armature unit 41 Armature 42 Bottom 43 Wall 44 Armature plunger 44a Flange 45 Retaining disc 46 Opening 47 Guide bushing 48 Annular flange 49 Gap 50 Guide bushing 52 Flange 60 Permanent magnet unit 70 Spring unit 80 Camshaft 82 Camshaft groove 100 Flange X Central axis