Electromagnetic Control Device, In Particular for Adjusting Camshafts of an Internal Combustion Engine

Abstract

An electromagnetic control device, in particular for adjusting camshafts or a camshaft section of an internal combustion engine, comprising an energisable coil unit, by means of which an armature mounted for movement along a longitudinal axis can be moved relative to a pole core between a retracted position and an extended position; a tappet, which is mounted for movement along the longitudinal axis with a free end portion with which, in the extended position, the tappet interacts with a camshaft in order to adjust the camshaft, and with an inner end portion (30), with which the tappet is attached to the armature, wherein the tappet is attached in a form-fitting manner to the armature by means of a deformable connection element and a method for the form-fitting attachment of a tappet to an armature of an electromagnetic control device of this kind.

Claims

1. An electromagnetic control device, comprising: an energizable coil unit, an armature, which is mounted displaceably along a longitudinal axis and is movable between a retracted position and an extended position, a tappet mounted movably along the longitudinal axis, comprising: a free end portion with which the tappet, in an extended position cooperates with a camshaft to adjust the camshaft and an inner end portion, with which the tappet is secured on the armature, a deformable connection element, wherein the tappet is secured on the armature under form closure with the deformable connection element.

2. The electromagnetic control device of claim 1, wherein the tappet comprises: a first ledge with which the tappet is in contact on the armature, and a second ledge, with which the tappet is in contact on the connection element.

3. The electromagnetic control device of claim 2, wherein the tappet comprises a form-fit recess, extending from the second ledge, into which the connection element is introducible by deformation.

4. The electromagnetic control device of claim 1, wherein the connection element is a deformable ferrule.

5. The electromagnetic control device of claim 4, wherein the tappet comprises a third ledge with which the tappet is in contact on the ferrule.

6. The electromagnetic control device of claim 4, wherein the ferrule comprises a deformation section.

7. The electromagnetic control device of claim 1, wherein the tappet is hardened.

8. The electromagnetic device of claim 1, wherein the tappet is rotatably secured on the armature.

9. A method for securing a tappet on an armature of the electromagnetic control device of claim 1, comprising the following steps: providing the deformable connection element and connecting the tappet on the armature under form closure by deformation of the connection element.

10. The method of claim 9, wherein the tappet comprises a first ledge and a second ledge as well as a form-fit recess extending from the second ledge, comprising the following steps: positioning the tappet such that the tappet is in contact on the first ledge, and introducing the connection element into the recess by deformation of the connection element.

Description

[0028] Exemplary embodiments of the invention will be described in further detail in the following with reference to the attached drawing. Therein depict:

[0029] FIGS. 1a and 1 b a schematic representation of the manner in which in prior art a tappet is connected with an armature,

[0030] FIG. 2 a sectional representation of an embodiment example of a connection element,

[0031] FIG. 3 a sectional representation of a tappet connected with the armature by the connection element depicted in FIG. 2,

[0032] FIG. 4 a basic sectional representation of an electromagnetic control device in which the tappet is connected to the armature by a connection element depicted in FIG. 2.

[0033] FIGS. 1a and 1 b show schematically the manner by which in prior art a tappet 10 is connected with an armature 12. With reference to the depiction selected in FIGS. 1a and 1 b, the tappet 10 is guided from below with a movement directed along a longitudinal axis L of tappet 10 through an opening 13 of the armature 12 until the tappet 10 with a lower ledge 14 is in contact on the armature 12. A retaining washer 16 is subsequently introduced from above into the armature 12 and slid onto the tappet 10 until the retaining washer 16 is in contact on an upper ledge 18 of tappet 10. The retaining washer 16 is dimensioned such that it projects radially beyond the opening 13 of armature 12. Subsequently, a not depicted stamping tool is introduced from above into armature 12 and tappet 10 is deformed such that the retaining washer 16 is secured on the tappet 10 under form closure. Due to the deformation, tappet 10 assumes a mushroom-like shape. The position of tappet 10 is now fixed with respect to the longitudinal axis L with the lower ledge 14 and, on the other hand, with the retaining washer 16. A certain play or tolerance along the longitudinal axis L can herein be provided for the purpose, for example, of compensating longitudinal changes due to temperature fluctuations.

[0034] FIG. 2 shows an embodiment example of a proposed connection element 20 with reference to a sectional representation. The connection element 20 is implemented as a tubular ferrule 22 comprising a deformation section 24. In the deformation section 24 the ferrule 22 has a reduced wall thickness.

[0035] FIG. 3 shows a sectional representation of a proposed tappet 26 connected to the armature 12 by the connection element 20 depicted in FIG. 2. Armature 12 is structured precisely as the armature 12 shown in FIGS. 1a and 1 b. Graphical discrepancies should be ignored. The tappet 26 comprises a free end portion 28 and an inner end portion 30, wherein within the inner end portion 30 the tappet 26 comprises a first ledge 32, a second ledge 34, a recess 36 extending from the second ledge 34, and a third ledge 38.

[0036] Again, with reference to the representation selected in FIG. 3, the tappet 26 is guided from below, with a movement directed along the longitudinal axis L of the tappet 26, with the inner end portion 30 through opening 13 of armature 12 until the tappet 26 is in contact with the first ledge 32 on armature 12. Ferrule 22 is subsequently slid onto tappet 26 until ferrule 22 is in contact on the third ledge 38 of tappet 26. The third ledge 38 is disposed such that it is flush with a bottom face 40 of armature 12 or projects minimally beyond the bottom face 40 when tappet 26 is in contact with the first ledge 32 on armature 12. A not depicted tool is subsequently slid [into the armature 12] from above onto ferrule 22. The tool can be implemented such that it is in contact at the transition from the deformation section 24, or from the reduced wall thickness, to the full wall thickness of ferrule 22. A positioning of the tool is thereby achieved. Ferrule 22 is subsequently deformed using the tool such that ferrule 22 is introduced into the recess 36, as is shown in FIG. 3. The position of ferrule 22 on tappet 26 is now fixed. The tool is subsequently retracted from the armature 12. Tappet 26 is now secured on armature 12 under form closure.

[0037] FIG. 4 shows a basic sectional representation of an electromagnetic control device 42 in which the tappet 26 is connected on armature 12 by the connection element 20 depicted in FIG. 2. Only those components are depicted that are required for an understanding of the function of the control device 42.

[0038] In a manner not further shown, tappet 26 is mounted in the control device 42 such that it is displaceable along its longitudinal axis L, for which purpose a slide bearing of synthetic material or a not magnetizable material can be employed.

[0039] To move the armature 12, the control device 42 comprises a coil unit 44 which annularly encompasses armature 12 with the formation of a gap. The control device 42 comprises furthermore a magnet unit 46 which comprises a pole core and a permanent magnet that are not explicitly shown and are considered to be included in the depiction of magnet unit 46.

[0040] Beyond that, there is provided a spring element 48 with a first end 50 and a second end 52. The spring element 48 can provide a prestress force acting substantially along the longitudinal axis L. The spring element 48 is stayed with the first end 50 on the bottom face 40 (see FIG. 3) and with its second end 52 on the magnet unit 46.

[0041] The control device 42 is operated in the following manner: the not depicted permanent magnet exerts an attractive force onto armature 12 acting along the longitudinal axis L, such that, in the retracted state, armature 12 is attracted by the permanent magnet and is in contact on an upper stop 54. The spring element 48 is hereby compressed such that spring element 48 provides a prestress force that is, however, less than the force of attraction of the permanent magnet. Armature 12 and tappet 26 consequently assume a retracted position that is not shown.

[0042] If the coil unit 44 is now energized, a magnetic field is built up that induces a magnetic force onto armature 12 which acts in the same direction as the prestress force provided by spring element 48 and consequently acts against the force of attraction of the permanent magnet. The sum of the magnetic force of the permanent magnet and the prestress force is greater than the force of attraction of the permanent magnet such that armature 12, and consequently also tappet 26, is moved away from the permanent magnet along the longitudinal axis L until armature 12 abuts against a lower stop 56 whereby tappet 26 and armature 12 have reached the extended position depicted in FIG. 4. In this extended position tappet 26 engages with its free end portion 28 into a grooving of a not depicted camshaft section. Referred to the rotational axis of the camshaft, the grooving has a spiral or helical course such that the engagement of tappet 26 into the grooving in combination with the rotation of the camshaft about its own rotational axis effects a longitudinal displacement along the rotational axis of the camshaft. To transfer appropriate axial forces, tappet 26 is in contact on one of the side walls of the grooving and rolls out on its surface such that tappet 26 at the engagement into the grooving is rotated at a very high rotational speed. The depth of the grooving decreases toward the end such that, starting at a certain angle of rotation of the camshaft, a tangency of the free end portion 28 of tappet 26 with the base of the grooving is carried out whereby tappet 26 is moved again in the direction of the permanent magnet. At this point at the latest the energization of the coil unit 44 is interrupted such that the force of attraction exerted by the permanent magnet onto armature 12 is again greater than the sum of the prestress force provided by the spring element 48, and of the magnetic force that is no longer active due to the absent energization of coil unit 44.

[0043] Tappet 26 and armature 12 consequently assume again the retracted position until the coil unit 44 is again energized. Further description of the function of the control device can also be found in WO 2016/001 254 A1.

[0044] As has been explained, when engaging into the grooving of the camshaft, tappet 26 is rotated about the longitudinal axis L. However, since the tappet 26 is mounted rotatably on armature 12, the rotation is not transferred onto armature 12 and consequently also not onto spring element 48. With reference to the rotation, tappet 26 is therefore decoupled from armature 12 and spring element 48.

LIST OF REFERENCE SYMBOLS

[0045] 10 Tappet according to prior art [0046] 12 Armature [0047] 13 Opening [0048] 14 Lower ledge [0049] 16 Retaining washer [0050] 18 Upper ledge [0051] 20 Connection element [0052] 22 Ferrule [0053] 24 Deformation section [0054] 26 Tappet [0055] 28 Free end portion [0056] 30 Inner end portion [0057] 32 First ledge [0058] 34 Second ledge [0059] 36 Recess [form-fit] [0060] 38 Third ledge [0061] 40 Bottom face [0062] 42 Control device [0063] 44 Coil unit [0064] 46 Magnet unit [0065] 48 Spring element [0066] 50 First end [0067] 52 Second end [0068] 54 Upper stop [0069] 56 Lower stop [0070] L Longitudinal axis