CROSS REFERENCE TO RELATED APPLICATION 0001 This application claims the priority of German Application No. 100 18 739.0 filed Apr. 15, 2000, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 0002 An electromagnetic actuator for operating a cylinder valve of a piston-type internal-combustion engine has to be mass produced in large numbers in an economical manner. Such an electromagnetic actuator includes opening and closing electromagnets having spaced, facing pole faces, an armature reciprocated between the pole faces and coupled to the cylinder valve to move the latter into open and closed positions, as well as opening and closing (resetting) springs opposing the armature motion. 0003 German Offenlegungsschrift (application published without examination) 198 25 728 discloses an electromagnetic actuator of the above-outlined type. The electromagnets are each provided with a respective, separate housing for receiving the magnet yoke which supports a coil. Such housings make possible a mass produced assembly of complete electromagnetic actuators. The housings are expediently made of a non-magnetic metal, for example, aluminum or an aluminum alloy so that they may be mass produced with a suitable casting process (such as die casting) in large numbers in an economical manner and adapted to individual requirements. On its side oriented away from the pole face of the inserted yoke body, the housing is provided with a tubular passage for receiving one end of a resetting spring. Thus, each housing may be used either for the part serving the opening function or the part serving the closing function. 0004 In the housing oriented towards the cylinder valve the closing spring extends through the housing passage and is supported at its ends by the engine block and, respectively, by a spring seat disk affixed to the cylinder valve stem. 0005 In the housing oriented away from the cylinder valve the opening spring passes through the housing passage and is supported on a threaded sleeve, by means of which the mid position of the armature between the pole faces of the two electromagnets may be adjusted. Such a threaded sleeve involves not only high manufacturing and assembly costs but also has disadvantages as concerns the reproducibility of an optimal setting and its handling during maintenance work.

SUMMARY OF THE INVENTION 0006 It is an object of the invention to provide an improved electromagnetic actuator of the above-outlined type from which the discussed disadvantages are eliminated. 0007 This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the electromagnetic actuator for operating a cylinder valve in an internal combustion engine includes first and second housings secured to one another. Each housing has a cavity and a through bore extending therefrom. First and second electromagnets are disposed in the cavity of the respective housings. Each electromagnet has a yoke, a coil and a pole face. The pole faces are oriented toward and spaced from one another, and a reciprocating armature is disposed between the pole faces. A spring which urges the armature away from the first electromagnet has an end oriented away from the armature. A support cap is axially insertable in the through bore of the first electromagnet and includes a cap base having an inner face supporting the spring end. A locking arrangement secures the support cap to the housing and has a component axially insertable in the through bore with the support cap. 0008 By eliminating the conventional, disadvantageous threaded sleeve, both actuator housings may be made from identical blanks without major finishing costs. By using an axially insertable support cap including a plug-in lock, cutting threads into the housing for a threaded adjusting sleeve cooperating with the opening spring is no longer needed. Merely geometrical elements for a plug-in lock are needed which may be readily formed in the housing blank. The presence of such housing configuration is harmless for the other, cap-less housing (accommodating the opening magnet) because, as concerns the opening magnet, only the closing spring is received in the housing passage and therefore any particular housing shape required for the support cap does not cause disturbance during service. Plug-in support bodies may be installed in a simple manner and further have the advantage that they may be made in large numbers of shaped steel sheet. Making the support cap from steel sheet also has the advantage that the cap, although exposed to high tension forces, may be relatively thin-walled. A further advantage compared to a conventional thread provided in the actuator housing resides in the fact that the securing and locking means can be made as large-area members so that the securing means of the steel supporting cap and the housing (such as an aluminum casting) may engage one another with a low surface pressure. 0009 According to a preferred embodiment of the invention, in the region of the through bore the support cap and the housing together form the support cap lock which immobilizes the support cap in the actuator housing. This is achieved by configuring the lock as a bayonet lock composed of at least one radial projection and a receiving element for accommodating the projection, provided, for example, on the outer surface of the support cap and the housing, respectively. Upon assembly, the support cap may be plugged into the housing passage (through bore) and is thereafter rotated about its axis to lock it in place. 0010 According to a particularly advantageous feature of the invention the projection and/or the projection receiving element is configured as a helical ramp in relation to the longitudinal actuator axis. As a result, by rotating the support cap relative to the housing, the bias of the opening spring may be changed and thus the mid position of the armature between the two pole faces may be adjusted. According to the invention, securing means are provided for fixing the support cap in the housing in a predeterminable position of installation. 0011 According to a further advantageous feature of the invention, the outer surface of the cap base whose inner bottom surface is engaged by the opening spring is provided with at least one element for receiving a mounting tool. Such an element may be a rectangular opening provided in the cap base or two openings radially spaced from the central axis of the supporting cap to receive, respectively, a quadrilateral wrench or a hook wrench. After inserting the supporting cap into the housing bore while compressing the opening spring, the support cap may be turned into its locked position by the wrench inserted into the receiving element. 0012 In accordance with a further advantageous feature of the invention, at least the base of the support cap made of steel sheet is tempered (hardened). The opening spring engages at one end a spring seat disk which is made of a wear resistant material and which is affixed to an armature guide bar. The other end of the opening spring engages the inner surface of the cap base. Since at that location substantial spring forces have to be taken up and the support of the springs in operation is exposed to a fluctuating pressing load, a hardened cap base prevents the spring end from working itself into the cap material. 0013 Instead of providing a helical ramp for the projection and/or the projection-receiving element of the bayonet lock for the support cap, according to another feature of the invention at least one adjusting washer is positioned on the inner face of the cap base for engaging the opening spring. By inserting adjusting washers of different thicknesses or as a stack, it is possible to adjust, within the required accuracy, the mid position of the armature between the two pole faces. By virtue of this measure the structure of the lock between the support cap and the housing is simplified since the support cap needs only to be inserted into the housing bore and then locked to the housing by rotation.

BRIEF DESCRIPTION OF THE DRAWINGS 0014 FIG. 1 is an axial sectional view of an electromagnetic cylinder valve actuator incorporating the invention. 0015 FIG. 2 is a perspective view of a housing for the closing magnet of the actuator, provided with a support cap for the opening spring according to a preferred embodiment of the invention. 0016 FIG. 3 shows the magnet housing of FIG. 2 without the support cap. 0017 FIG. 4 is a sectional view taken along line IV-IV of FIG. 3. 0018 FIG. 5 is a perspective view of the support cap shown in FIG. 2. 0019 FIG. 6 is a sectional view taken along line VI-VI of FIG. 5. 0020 FIG. 7 is a sectional elevational view of a support cap according to a variant of the FIG. 6 structure. 0021 FIG. 8 is a perspective view of another preferred embodiment of the invention. 0022 FIG. 9 is a sectional view taken along line IX-IX of FIG. 8. 0023 FIG. 10 is a perspective view of a support cap according to the embodiment shown in FIG. 8. 0024 FIG. 11 is a perspective view of another preferred embodiment of the support cap for use in a housing shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 0025 The electromagnetic actuator illustrated in FIG. 1 includes a closing electromagnet 1 and an opening electromagnet 2. The magnets 1, 2 which are separated from one another by spacer members 3.1 and 3.2 have respective pole faces 4 oriented toward one another. In the space between the two pole faces 4 an armature 5 is movable from one pole face to the other and is attached to a guide bar 6 passing through the electromagnet 2. In the illustrated embodiment the armature 5 has a rectangular outline. 0026 A further guide bar 7 passes through the electromagnet 1 in aligned contact with the guide bar 6. At its upper end 7 the guide bar 7 is connected with a resetting spring 8 which serves as an opening spring. The lower free end 9 of the guide bar 6 engages the upper free end 10 of the valve stem 11 of a valve which is guided in an only symbolically shown cylinder head 12 of an internal combustion engine. By means of a resetting spring 13 which serves as a closing spring, the cylinder valve is urged in the closing direction. The closing spring 13 and the opening spring 8 exert their spring force in facing, opposite directions whereby in the de-energized state of the electromagnets 1 and 2 the armature 5 assumes its position of rest in the mid region between the two pole faces 4 of the electromagnets 1 and 2, as illustrated in FIG. 1. 0027 In case the two electromagnets 1 and 2 are alternatingly energized, the armature 5 alternatingly arrives at the respective pole face 4 of the two electromagnets 1 and 2 and, accordingly, the cylinder valve is, for the duration of the energization, maintained in the open position (engagement of the armature 5 with the pole face 4 of the electromagnet 2) against the force of the closing spring 13 or in the closed position (engagement of the armature 5 with the pole face 4 of the electromagnet 1) against the force of the opening spring 8. 0028 The electromagnetic actuator illustrated in FIG. 1 is a structural unit composed of practically identical modular elements. The two electromagnets are preferably of identical construction and are each composed essentially of a separate housing 14 which has a cavity 15 oriented towards the armature 5 for receiving a yoke body 16 carrying a coil 17. The housing 14 further has a through bore 18 through which the respective opening spring 8 or closing spring 13 may partially pass. 0029 As indicated by the flatness of the actuator housing 14 shown in FIG. 2, the electromagnetic actuator is of very narrow construction allowing a close, side-by-side installation of such actuators in the limited space of the engine. The yoke body 16 is, together with the coil 17, inserted into the cavity 15 of the housing 14 and is fixed and held therein by means of a suitable cast mass. 0030 The housing 14 further has an additional lateral opening 20 which permits access to the terminals 21 of the coil 17. By virtue of such an arrangement the two electromagnets 1, 2 may be connected to the actuator control by a coded, one-piece plug 22 (shown in dash-dot lines) in a non-interchangeable manner. The plug 22 is positioned and protected in the lateral flanks of the lateral opening 20. 0031 Reverting to FIG. 1, the two housings 14 made, for example, of an aluminum alloy by means of die casting, have aligned passages 23 which extend parallel to the axis of the guide bars 6 and 7 and cooperate with similar apertures provided in spacers 3.1 and 3.2 positioned between the two housings 14. The two housings 14 may thus be firmly bolted to one another and/or to the engine block 12 with the interposition of the spacers 3.1 and 3.2. 0032 The opening spring 8 is supported by a support cap 25 serving as a spring-force setting element. By turning the support cap 25 or by inserting adjusting washers, the mid position of the armature 5 between the two pole faces 4 may be altered. 0033 As may be seen in FIG. 1 and particularly in FIG. 2, the through bore 18 is surrounded by a flange 19 at its end oriented away from the yoke body 16. Also referring to FIG. 3, on the inside the through bore 18 is, on diametrically opposite sides, provided with groove-like recesses 26 cooperating with respective, radially outwardly oriented projections 27 provided on the support cap 25, as also shown in FIGS. 5, 6 and 7. By virtue of this structure the support cap 25 may be inserted axially into the through bore 18 and then rotated to be immobilized in the housing 14 by a bayonet-type lock. Upon insertion of the support cap 25, the opening spring 8, previously positioned on a spring seat disk 71 affixed to the upper end 71 of the guide bar 7, is compressed. By virtue of the bias of the opening spring 8 the support cap 25 is held in its position even when the armature 5 is in engagement with the pole face 4 of the opening magnet 2. 0034 The base 28 of the support cap 25 is provided with a polygonal (for example, rectangular, as shown in FIG. 2) aperture 29 for receiving a non-illustrated turning tool to rotate the support cap 25 after it has been inserted into the through bore 18. 0035 In actuator constructions in which the upper end of the guide rod 7 passes through the opening spring 8 and through the base 28 of the support cap 25 and is provided with sensor elements, the through aperture 29 is circular. In such a case, as illustrated in FIG. 5, as tool receptors spaced bore holes 29.1 are provided into which a suitable hook wrench may be inserted for turning the support cap 25. 0036 The embodiment illustrated in FIG. 2 is shown in detail in FIGS. 4 and 5 and will be further described as the specification progresses. 0037 As may observed in FIG. 4, adjacent the groove-like recesses 26 the lower edge 30 of the through bore 18 has an undercut which is configured as a helical ramp 31 provided with a plurality of consecutive depressions. 0038 Correspondingly, as seen in FIG. 5, the projections 27 have nose-like elevations 32 which may be brought into engagement with the depressions on the ramp 31 by rotating the support cap 25 in the through bore 18. By virtue of the slope of the ramp 31 the distance of the cap base 28 changes relative to the pole face 4 of the closing magnet 1 in the shortening direction if, after insertion of the support cap 25 the latter is turned clockwise. As a result, the bias of the opening spring 8 is increased and, accordingly, the armature 5 is shifted in the direction of the pole face 4 of the opening magnet 2, simultaneously compressing the closing spring 13. By virtue of the engagement of the nose-shaped elevations 32 into the depressions on the ramp 31, the support cap 25 is immobilized in the housing 14 and thus securely prevented from rotating. 0039 Instead of depressions on the helical ramp 31 and corresponding nose-like elevations 32 on the support cap 25, it is feasible to configure the ramp 31 as well as the projection 27 to have a smooth surface as shown in FIG. 7. The angular immobilization of the support cap 25 after adjustment of the mid position of the armature 5 may be effected by a plug-in pin which passes through radial bores 33 in the support cap and corresponding, non-illustrated radial holding bores in the housing flange 19. It is also feasible, however, to provide the edge 27.1 of the projections 27 with a series of tooth-like recesses associated with at least one holding bore passing axially parallel through the flange 19. Thus, after setting the mid position of the armature by turning the support cap 25 in the appropriate angular position, the support cap 25 may be angularly immobilized by a pin passing through the holding bore in the flange 19 and a corresponding, axially parallel bore in the edge 27.1 of the projection 27. 0040 FIG. 8 is a perspective view of an embodiment in which the housing is provided with partial collar-like elevations 19.1 on its side oriented away from the housing cavity for the yoke body. As shown in FIG. 9, radial holding pins 34 pass through the elevations 19.1 and project into corresponding recesses 35 provided in the circumferential wall of the support cap 25. The recesses 35 may be through openings as shown in FIG. 10. For loosening the support cap the pins 34 are removed. 0041 As shown in the variant illustrated in FIG. 11, it is also feasible to provide, in the circumferential wall of the support cap 25, a slit-like recess 36 having an approximately L-shaped course and terminating in a detent 37. Such a support cap may be inserted on the pins 34 affixed to the collar-like insert 19.1 and may be immobilized by rotation. Here too, the support cap 25 is held in its position by the bias of the opening spring 8. 0042 In the embodiment according to FIGS. 9, 10 and 11 but also in all the previously described embodiments when suitably modified, the adjustment of the mid position of the armature 5 is effected by inserting and positioning on the base 28 of the support cap 25 one or more washers 38 of predetermined thickness before attaching the support cap 25 to the housing 14. 0043 The adjusting washers 38 may also be used when for the adjustment of the mid position of the armature 5 only an insufficient setting path is available for the projection 27 on the helical ramp 31. 0044 The wall thicknesses available for the housing 14 are sufficient to take up fluctuating stresses even if made of aluminum or aluminum die cast. The support cap 25 which should be thin-walled, is expediently made of steel sheet; for increasing the wear resistance, at least the base 28 is tempered to prevent the end of the opening spring from working itself into the base 28 during operation. Despite the thinness of the walls, the fluctuating spring forces acting between the housing 14 and the support cap 25 may be taken up as tension stresses via the steel plate material of the support cap 25. 0045 The drawings readily show that the arrangement of projections and projection-receiving elements may be interchanged, that is, the through bore 18, instead of the groove-like receiving elements 26, may be provided with the radial projections 27 and, likewise, the support cap 25, instead of the projections, may be provided with the groove-like receptors. 0046 It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.