This application is a § 371 National Phase of PCT/EP2015/064896, filed Jun. 30, 2015, the entirety of which is incorporated by reference and which claims priority to German Patent Application No. 10 2014 109 124.8, filed Jun. 30, 2014.
The application relates to an electromagnetic camshaft adjuster having an armature unit that can be moved relative to a pole core by energising a stationary coil unit and that has an armature plunger as well as a permanent magnet unit, through which the armature unit is held in a resting position in the non-energised condition of the coil unit.
Such an electromagnetic camshaft adjuster is known for example from DE 20 2011 052 220 U1. The permanent magnet unit there has a disc-shaped permanent magnet that is received between a first and second magnetically conductive pole discs. The two pole discs are here welded together with the armature plunger. The end of the armature plunger that protrudes from the housing of the electromagnetic camshaft adjuster engages in a circumferential groove of a cam that can be adjusted on a camshaft. When the coil of the electromagnetic camshaft adjuster is energised, the plunger is forced in the direction of the camshaft and is set back by the camshaft during rotation. This electromagnetic camshaft adjuster has no spring unit.
Another electromagnetic camshaft adjuster is described in EP 2 252 774 B1, which is also placed on the front side of a camshaft of an internal combustion engine and effects an axial movement of the camshaft adjuster as a response to an energisation of the stationary coil unit and by the movement effected thereby of the armature unit or of the associated armature plunger. The yoke unit there is supported in a manner so as to be rotational relative to the coil unit. By contrast, the armature unit with the armature plunger is mounted to be stationary in the rotational yoke and core unit. In this way, the overall armature unit together with the surrounding yoke unit can rotate together with the camshaft.
Finally, also EP 1 421 591 B1 describes an electromagnetic camshaft adjuster. Here, a permanent magnet disc is also provided between two pole discs, which in turn is fixedly connected to the armature unit or the armature plunger. The permanent magnet unit ensures in the resting position, which means when the coil is not energised, that the armature unit is held on the pole core. It is not until the coil is energised with a current that a magnetic field that acts against the field of the permanent magnet discs and the armature unit is repulsed by a spring force supported by the pole core. To this end, a coil spring is provided, the spring force of which is dimensioned to be smaller than the holding force of the permanent magnet disc in the non-energised condition of the coil unit. As soon as the spring force of the coil spring is stronger than an attraction or holding force of the permanent magnet disc, an energisation of the coil with current can be removed and the assembly is held in the extended condition of the armature plunger, without a current having to be supplied to the coil.
The present disclosure provides a further electromagnetic camshaft adjuster that is simple to manufacture and still allows very fast switching times, in particular switching times of less than three milliseconds.
The present application provides an electromagnetic camshaft adjuster having the features and structures disclosed herein.
It is here advantageous for the electromagnetic camshaft adjuster according to the present disclosure that the permanent magnet unit is mounted to be stationary between a housing cover and the pole core of the electromagnetic drive unit. In addition, the armature plunger is provided to be rotatable in an armature of the armature unit, and the spring unit is supported on a part of the armature unit that is preferably mounted in a rotationally fixed or a substantially rotationally fixed manner. The part of the armature unit may be the armature itself, in which the armature plunger is rotatably seated.
Such an electromagnetic camshaft adjuster is characterised by a very compact design and by very constant switching times, which may be below three milliseconds. What is of particular advantage here is the stationary mounting of the permanent magnet between the housing cover and the pole core. This simplifies the design of the electromagnetic camshaft adjuster because the permanent magnet can be installed without any bearing or guide bushings.
In the present disclosure, the armature unit is formed as a pot-shaped armature, the bottom of which is provided with an opening through which the armature plunger extends. The armature plunger is here preferably mounted so as to be rotational in the armature. Such a rotational mounting of the armature plunger in or on the armature has the advantage that the armature itself may be mounted so as to be merely axially displaceable, but rotationally fixed, in the electromagnetic camshaft adjuster.
According to the disclosure, the armature unit or the armature may here be guided in a guide bushing so as to be axially movable, but rotationally fixed. Such a rotational fixing may be achieved for example by providing the guide bushing on the side thereof that faces the armature unit and the armature unit on the side thereof that faces the guide bushing with a tongue-and-groove guide that extends along the central axis of the electromagnetic camshaft adjuster.
According to the disclosure, the armature plunger protrudes through the bottom of the pot-shaped armature and is encompassed and retained on the inside of the armature at the bottom by a retaining disc, preferably in such a way that the armature plunger can continue to rotate in the armature and in the opening of the retaining disc.
The spring unit provided according to the present disclosure for a force-related support of the movement of the armature unit in the direction of the camshaft is supported at one end thereof on a suitable surface within the camshaft adjuster, for example on the housing cover, and is supported on the armature unit at its opposite end that faces the camshaft. Preferably, the spring unit is here supported at one end on the bottom of the pot-shaped armature. The advantage of this is that the spring unit is supported on both of its ends on surfaces which rotate not at all or only very slightly during operation, so that no friction occurs on the support surfaces of the spring unit. For this reason, it is provided in a development of the present disclosure that the above-mentioned retaining disc has a smaller diameter than the spring unit that is preferably formed as a coil spring. As a result, the front end of the spring unit may be supported on the bottom of the armature of the armature unit.
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:
In the figures following below, the same reference signs identify the same parts with the same meaning, unless otherwise specified.
The adapter element 14 extends through a flange 100. On this flange 100, the housing 11 of the electromagnetic camshaft adjuster 10 is seated.
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.
As can be seen from
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
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.
For the sake of completeness it is to be noted in connection with the representation of
An electromagnetic camshaft adjuster 10 as shown in
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
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
Number | Date | Country | Kind |
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10 2014 109 124 | Jun 2014 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2015/064896 | 6/30/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2016/001254 | 1/7/2016 | WO | A |
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Number | Date | Country | |
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20180144855 A1 | May 2018 | US |