Electromagnetic actuating apparatus

An electromagnetic actuating apparatus, in particular a proportional magnet or switching magnet, includes a magnet armature (4) guided for axial movement in a pole tube (2). The pole tube is at least partially surrounded by a coil winding and is adjoined by a pole core (10) via a separating region (20) forming a magnetic decoupling. On energization of the coil winding (52), a magnetic force acts on the armature (4) to move the armature (4) in the direction of the pole core (10) within a travel area. At least one insert (28) of ferromagnetic material with a preset axial thickness is between the armature (4) and the pole core (10) to shorten, as desired, the axial length of the travel area.

FIELD OF THE INVENTION

The invention relates to an electromagnetic actuator, in particular a proportional magnet or solenoid, with a magnet armature. The magnetic armature is guided in an axially movable manner in a pole tube at least partially surrounded by a coil winding. The pole tube is connected to a pole core via a magnetic decoupling forming a separation area. Upon energization of the coil winding, a magnetic force acts upon the armature, which magnetic force seeks to move the armature towards the pole core within a stroke chamber.

BACKGROUND OF THE INVENTION

Such electromagnetic actuators, in technical terminology also called proportional magnets or switching magnets, are freely available on the market in a variety of embodiments. An actuator provided in particular for actuating a valve of this type is described for example in DE 10 2008 061 414 A1. In such devices, the armature performs a stroke movement in the pole tube upon electrical energization of the associated coil winding. Upon de-energization of the coil winding, as a rule, the armature is returned to its home position by a restoring force. In most cases, the restoring force acts on the armature via an armature-connected actuator member, which is designed, for instance, rod-shaped, extends through the pole core and triggers a relevant actuation procedure, for instance, in an externally connected valve for controlling fluid flows. Depending on the application, a specific determined response behavior of the actuating device is required. More specifically, a certain course of the magnetic force-displacement curve is required for associated switching and control functions. The geometry of the pole tube in the transition region between the magnetic separation area and the pole core is particularly decisive for the course of this F-d curve. The manufacturer of such actuation devices then has to manufacture and offer different pole core systems, as needed, i.e. depending on whether a customer wants a rising characteristic, an approximately horizontal characteristic, or a falling characteristic. In particular for small quantities, customization to customer wishes leads to increased manufacturing costs.

SUMMARY OF THE INVENTION

With regard to this difficulty, the invention addresses the problem of providing an electromagnetic actuator that provides more universal capabilities and therefore makes for an efficient production.

According to the invention, this problem is basically solved by an electromagnetic actuator having, as one essential feature of the invention for a desired shortening of the axial length of the section of the stroke chamber located between the magnetic separation area on the pole tube and the pole core portion, at least one insert made of ferromagnetic material of a pre-specified axial thickness introduced between the armature and the pole core. This insert opens up the possibility of manufacturing a pole tube-pole core system in a standard size and then introducing an additional ferromagnetic element determining, as required, the length of the stroke chamber defining the characteristic curve available for a stroke of the armature between the magnetic separation area and the pole core. An optimum course of the force-displacement curve for the intended use is then attained.

Particularly advantageously, the portion of the stroke chamber adjacent to the separation area of the pole tube is formed by a recess in the pole core. The recess continues the guide of the armature formed by the pole tube and ends at the separation area in an edge-forming rim. The respective insert can applied to the bottom surface of the recess of the pole core. In doing so, the axial distance between the ferromagnetic insert and the rim of the pole core acting as magnetic control edge can be set to a desired length, for which a desired characteristic curve of the F-d curve is given.

Preferably, the respective insert can be attached on the bottom surface of the recess.

Advantageously, the armature has a rod-shaped actuating member, and a ferromagnetic annular disc of a pre-selected thickness surrounding the actuator member is provided as the respective insert.

For an optimum reliability, an anti-adhesion disc can be arranged in a conventional manner between the annular ferromagnetic disc and the armature.

In exemplary embodiments in which an end body is attached at the side facing away from the pole core end of the pole tube, which end body forms a stroke delimiter for the armature, different lengths of the total stroke available for the armature can be realized through an appropriate dimensioning of the end body for pole tubes produced in a standard size depending on the desires and requirements.

The respective annular ferromagnetic disc may be attached to the pole core by gluing or soldering or by a material deformation, for example by caulking the outer edge, or by caulking an annular groove formed in the bottom surface of the pole core.

Alternatively, the respective annular ferromagnetic disc can be attached by a sleeve bordering its peripheral edge, which sleeve is externally attached to an inner surface of the pole tube or pole core.

Furthermore, the respective annular ferromagnetic disc may be attached by a weld formed between the peripheral edge and the surface of the pole core.

In alternate exemplary embodiments, the arrangement can be made such that the respective annular ferromagnetic disc has a coaxial sleeve-shaped extension on the side facing away from the armature. This extension is secured in a bore of the pole core by an interference fit and is penetrated by the rod-shaped actuating member of the armature.

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a side view in section of an exemplary embodiment of the actuator according to the invention with an associated coil winding omitted. The coil winding is arranged in a manner known per se on the pole tube2and can have a current applied to it for actuation processes. In the pole tube2, an armature4has one end with a coaxial rod-shaped actuating member6attached and is guided in an axially movable manner. Actuating member6extends through a through hole8in a pole core10, such that the free end12of the actuating member6is accessible for an actuating process at a connecting part14of the pole core10. An actuator is connected to the connecting part14with for example, the actuator being in the form of a valve (not shown inFIG. 1).

The example shown inFIG. 1is designed as a “pushing magnet”. The illustrated axial position corresponds to the fully energized state of excitation of the coil winding (not shown), with the armature4generating a compressive force via the actuating part6as an actuating force. A resetting device, returning the armature4upon termination of the energization inFIG. 1upwardly, for example in the form of a return spring, is not shown inFIG. 1, as such a device can be designed according to prior art. To limit the length of the return stroke caused by a restoring force of the armature4, an end body18is attached to the end of the pole tube2, attached on the top inFIG. 1by a crimp16. By appropriate dimensioning of the end body18, the stroke designed for the return stroke can be set to a desired length. The pole tube2is connected to the pole core10via a weld20that forms a separation area effecting a magnetic decoupling in a manner known per se. The guide formed on the inside of the pole tube2for the armature4continues through the separation area formed by the weld20in a recess22, which recess is cylindrical in the pole core10and has a bottom surface24located in a radial plane. At the weld20, the recess22terminates at an edge26that forms a sharpened edge surrounding the guiding surface of the armature4.

In the illustration ofFIG. 1, an annular ferromagnetic disc28made of a ferritic material is penetrated by the rod-shaped actuating member6and is inserted at the bottom surface24in the recess22of the pole core10. An anti-adhesion disc30of conventional type is arranged between the annular disc28and the end of the armature4. The annular disc28shown in an inserted state has a relatively low axial thickness.FIG. 1, shows by way of example, a selection of insertable annular discs28of different axial thicknesses. The thickness of the respective inserted annular disc28results in a corresponding shortening of the axial length of the stroke chamber available for armature4when moving in the direction of the pole core10. The modification of the stroke chamber in the critical stroke range, which adjoins the magnetic separation area of the weld20, affects the magnetic force-displacement curve, as shown in examples inFIGS. 2 and 3.

FIG. 2shows an example with an inserted annular disc28of lower thickness, whileFIG. 3shows an example with an annular disc28of greater thickness. In the example ofFIG. 2, the characteristic curve32in a numbered F-d graph is without inserted annular disc28, and the characteristic curved34is with an inserted annular disc28of a thickness of 0.7 mm. As can be seen, the inserted annular disc28results, via a mainly to be used standard stroke of approx. 1.5 mm to 2.5 mm, in a largely horizontal characteristic curve, whereas the characteristic curve32is inclined there, in contrast. In the example shown inFIG. 3for an inserted annular disc28with a thickness of 1.3 mm, a sharp increase in force results in a higher maximum force with a smaller stroke, cf. characteristic curve34. The choice exists, in manufacturing a pole tube-pole core system in a standard size, to realize a selected course of the F-d curve, depending on whether no annular ferromagnetic disc28is inserted or an annular disc28of predetermined thickness is inserted. With the same standard size, the stroke of the return stroke can also be determinable by selecting the dimensions of the respective end body18.

FIGS. 4 to 9show further exemplary embodiments with a choice of possible types of the incorporation of an annular disc28. For instance in the example ofFIG. 4, the annular disc28is attached to the bottom surface24of the pole core10by adhesive bonding or brazing. In the example ofFIG. 5, a connection is realized by mechanical deformation by external caulking36the annular disc28against the inner wall of the recess22.FIG. 6shows the attachment of the annular disc28by a sleeve38, forming the guiding surface for the armature4on the inside of the pole tube2and the recess22.

In the example ofFIG. 7, a welded geometry40formed on the annular disc28is provided as the connection, while in the example ofFIG. 8in contrast, a mechanical deformation is provided by caulking the annular disc28into an annular groove42incorporated in the bottom surface24. Finally,FIG. 9shows an example, in which a specially shaped annular disk28has, on the side facing away from the armature4, a coaxial sleeve-shaped extension44, which is secured in the bore8of the pole core10by an interference fit.

FIG. 10shows an exemplary embodiment in which the invention has been implemented for a compact magnet. In contrast to the configuration shown inFIG. 1, the pole core10is designed shorter in relation to its diameter and has a flange-shaped radial extension48at the end having the connection member14. The end body18forms the closed end of a pot-shaped housing50, which extends down to the extension48of the pole core10. The extension48closes the open end of the pot. Between the end body18and the extension48of the pole core10, the housing50surrounds the coil winding52, which in turn surrounds a large part of the pole tube2and the pole core10. For the compact magnet shown inFIG. 10the course of the F-d curve can be equally influenced by the selection of the introduced ferromagnetic annular discs28.