Pole tube for electromagnets and magnetic valves, and method as well as apparatus for its manufacture

Abstract

The invention relates to a method for manufacturing a pole tube, with two magnetic pole tube parts, for an electromagnet, in particular for a magnetic valve of an automatic transmission in an automobile, including the following steps: (a) arranging the pole tube parts on a centering arbor; and (b), connecting, in particular insert molding and/or casting an outer lateral surface of the pole tube parts; wherein the centering arbor has a radially expandable cylinder surface also closed even in the expanded state. Further, the invention relates to, in particular with the method obtainable, a pole tube, an electromagnet for a magnetic valve, in particular for an automatic transmission in an automobile, having a pole tube according to the invention, and an apparatus for the manufacture of the pole tube.

Claims

1. A method for manufacturing a pole tube, having two magnetic pole tube parts, for an electromagnet, in particular for a magnetic valve of an automatic transmission in an automobile, comprising the following steps: (a) arranging the pole tube parts on a centering arbor; and (b) connecting, in particular insert molding and/or casting, an outer lateral area of the pole tube parts; wherein employing the centering arbor has a radially expandable cylinder surface which is closed even in the expanded state.

2. The method according to claim 1, further comprising: in step (a), arranging the pole tube parts on the centering arbor with a mutual axial distance such that the pole tube parts form a gap sufficient for a magnetic separation.

3. The method according to claim 1, further comprising: after step (a), expanding the centering arbor so that in the region of the gap, a lateral surface of the centering arbor closes the gap with the respective inner surfaces of the pole tube parts without any offset.

4. The method according to any of claim 1, further comprising: in step (b), connecting, in particular insert molding and/or casting outer lateral surfaces, the pole tube parts with a nonmagnetic material so that, together with the pole tube parts, the nonmagnetic material forms the inner surface of the pole tube.

5. The method according to any of claim 1, further comprising: inserting a pole core in one of the pole tube parts at one end of the pole tube.

6. A pole tube for an electromagnet, in particular for a magnetic valve of an automatic transmission in an automobile, comprising a nonmagnetic material that fills a gap between two pole tube parts, wherein the pole tube parts are arranged in a mutually concentric relationship, wherein outer lateral surfaces of the pole tube parts are cast-in or insert-molded with the nonmagnetic material, in particular with a plastic, and wherein together with the pole tube parts the nonmagnetic material forms a planar and offset-free inner surface.

7. The pole tube according to claim 6, wherein the pole tube can be obtained through manufacture by means of a method according to claim 1.

8. The pole tube according to claim 6, wherein the nonmagnetic material is a plastic.

9. The pole tube according to claim 6, wherein the pole tube parts are manufactured from a magnetically conducting steel material, for example, by machining, or as a sintered part or as an extruded part.

10. The pole tube according to claim 6, wherein portions of the inner surface of the pole tube which is formed by the nonmagnetic material in the gap and respectively the part of the inner surface of the adjacent pole tube part have the same inside diameter at the respective transitions.

11. The pole tube according to claim 6, wherein one of the pole tube parts has a pole core at one end of the pole tube or is connected, by joining, with a pole core.

12. The electromagnet according to claim 6, wherein a bearing foil is arranged between the pole tube and a lateral surface of a magnetic armature arranged in the pole tube.

13. The electromagnet for a magnetic valve according to claim 6, wherein a coil, in particular a copper wire winding, is arranged on a winding carrier, which is formed by the nonmagnetic material surrounding the lateral surface of the pole tube parts.

14. An apparatus for manufacturing a pole tube, having two magnetic pole tube parts, for an electromagnet, in particular for a magnetic valve of an automatic transmission in an automobile, comprising: a centering arbor for arranging the pole tube parts; and an injection mold which can enclose the pole tube parts arranged on the centering arbor to connect the pole tube parts by insert molding and/or casting an outer lateral surface of the pole tube parts by means of an injection molding or casting material; wherein: the centering arbor has a radially expandable cylinder surface which is closed even in the expanded state, and the apparatus is configured to radially expand the centering arbor before the insert molding and/or casting so that in the region of a gap between the pole tube parts a lateral surface of the centering arbor terminates the gap flush with the respective adjacent inner surfaces of the pole tube parts.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] FIG. 1 shows a flowchart of the inventive method for manufacturing an inventive pole tube.

[0042] FIG. 2A shows a step in a method for manufacturing an inventive pole tube.

[0043] FIG. 2B shows a step in a method for manufacturing an inventive pole tube.

[0044] FIG. 2C shows a step in a method for manufacturing an inventive pole tube.

[0045] FIG. 2D shows a step in a method for manufacturing an inventive pole tube.

[0046] FIG. 3 shows an embodiment of a magnetic valve of an electromagnet according to the invention.

[0047] FIG. 4 shows a connection, known from prior art, of two pole tube halves by means of a nonmagnetic ring and casting with an outer plastic layer.

DETAILED DESCRIPTION

[0048] FIG. 1 shows a flowchart as to the method steps shown in FIG. 2. In a first step S10a, pole tube's structural parts are arranged on a hydraulic expansion arbor, which is a possible embodiment of a centering arbor with a radially expandable closed cylinder lateral surface. In FIG. 2(a), a magnetic tube 20, which has a flange 24 at one end forming an end 22 of the pole tube, is arranged on the expansion arbor 10.

[0049] Thereafter, as shown in FIG. 2(b), the second pole tube's structural part, namely a pole core tube 26, is slipped on the expansion arbor 10. It can be readily recognized in FIG. 2(b) that the pole tube's structural parts, namely the magnetic tube 20 and the pole core tube 26, are arranged to each other on the expansion arbor 10 with a distance D. The distance D is so chosen or adjusted that between the pole tube's structural parts 20, 26, a gap 28 is formed sufficient for magnetically separating the pole tube's structural parts. The gap-forming arrangement is step S10b of FIG. 1.

[0050] The expansion arbor 10, as a possible embodiment of a centering arbor having a radially expandable cylinder lateral surface closed even in the expanded state, is in principle known concerning its manner of functioning and its construction in the field of the workpiece clamping and tool clamping, and can therefore substantially be constructed like a hydro expansion arbor known there. The expansion arbor 10 shown schematically in FIGS. 2(a) to 2(d) corresponds in its construction and its function to a hydro expansion arbor known for workpiece clamping.

[0051] Instead of the expansion arbor 10, a centering arbor having a radially expandable lateral cylinder surface, which is closed even in the expanded state, can of course be employed while the centering arbor can have any other arbitrary setup, as long as the effect of the radially expandable closed cylinder surface required here can be supplied for closing the gap 28 on the inside between two gap-forming adjacent pole tube's structural parts 20, 26.

[0052] Inside of the expansion arbor 10 there is a chamber system 12 into which a pressurizing medium, for example a hydraulic oil, can be pressed via a feed line 14, whereby the pressure built up in the pressurizing medium acts substantially against the inner walling of the thin-walled expansion sleeve 16. Consequently, the expansion sleeve 16 expands radially uniformly, centrically and cylindrically to the center axis M corresponding to the pressure fed on the entire clamping length L. Thereby the two pole tube's structural parts 20, 26 are centered to each other by their inner surfaces on the expansion arbor. The expanding of the expansion arbor 10 corresponds to the step S20 in FIG. 1.

[0053] In contrast to a centering by means of cone surfaces at an intermediate ring, like in the prior art, here the influence of concentricity tolerances on the later functional inner surfaces is at least minimized, ideally excluded, by means of the clamping. By using the hydraulic expansion arbor 10, the present diameter tolerances between the two pole tube's structural parts are perfectly distributed, ideally compensated, over the entire circumference of the pole tube's structural parts. Additionally, the region forming the gap 28 between the two pole tube's structural parts to the interior of the pole tube to be manufactured is sealed splash-tightly or tightly and delimited planarly by means of the expansion arbor 10.

[0054] In the details shown in FIGS. 2(a) to 2(d) of the inventive manufacturing method, in order to facilitate the clamping of the pole tube's structural parts 20, 26 to the expansion arbor 10, a pole core 30 (cf. Figure (d)), where applicable including flange, is joined with the finished pole tube advantageously only after the insert molding. The open construction of the pole tube during manufacture, i.e. with a through bore, allows a central positioning of both pole tube's structural parts on the hydraulic expansion arbor 10.

[0055] In FIG. 2(c) step S30 of FIG. 1 is illustrated, where the pole tube's structural parts 20, 26 are connected by insert molding of the outer lateral surface of the pole tube's structural parts with a nonmagnetic material, for example a plastic. The nonmagnetic material forms, beside the inner surfaces of the pole tube's structural parts 20, 26, a part of the inner surface of the pole tube in the region of the gap 28. For this purpose, it is represented in FIG. 2(c) that the pole tube's structural parts 20, 26 arranged on the expansion arbor 10 are enclosed by two halves of an injection mold 18a, 18b in such a way that the space formed thereby between the pole tube's structural parts 20, 26, the lateral surface of the expansion arbor 10 in the region of the gap 28 as well as the inner surface of the injection mold parts 18a and 18 has the form of a winding carrier 32. For this purpose, a nonmagnetic material, for example a plastic, is insert molded in a per se known manner into this space in liquid form, and thus the outer lateral surfaces of the pole tube's structural parts 20, 26 are insert molded and/or cast. In this way the pole tube's structural parts 20, 26 are permanently connected.

[0056] FIG. 2(d) shows the finished pole tube 34, consisting of the magnetic tube 20 and the pole core tube 26, the pole core 30 inserted into pole core tube 26 as well as the insert molded/cast winding carrier 32 connecting the pole tube's structural parts 20, 26. Particularly advantageously there results a nearly offset-free inner surface 36 for the pole tube 34 through the manufacturing method according to the invention.

[0057] Preferably the pole tube's structural parts 20, 26 and the pole core 30 are manufactured from a magnetically conducting ironworks substance, for example by machining (e.g. 1.0715), or as a sintered part (e.g. Sint D35) or as a extruded part (e.g. 1.0303). Preferably the nonmagnetic material is a plastic, e.g. PA 6.6 GF30.

[0058] FIG. 3 shows a section through an inventive electromagnet 40 for a magnetic valve with an inventive pole tube 34, which has preferably been manufactured with the inventive manufacturing method of FIGS. 1 and 2.

[0059] In the electromagnet 40, the pole tube 34 is arranged concentrically to a center longitudinal axis 42 of the electromagnet 40. As shown in FIG. 2(d), the pole tube 34 consists of the magnetic tube 20, the pole core tube 26 and the pole core 30 inserted therein at one end. The magnetic tube 20, the pole core tube 28 and the pole core 30 are manufactured from a magnetic material.

[0060] On the outer lateral surfaces of the pole tube's structural parts 20, 26, an insert molding or casting layer of a nonmagnetic material, preferably plastic, is applied. This insert-molded or cast layer acts as a winding carrier 32 for a coil 44 arranged thereon, for example in the form of a copper wire winding. Outwardly, the winding carrier 32 and the coil 44 supported thereon are enclosed by a cylindrical housing 46 of the electromagnet 40.

[0061] On the side of the pole tube 34 having the flange 24, the housing 46 is closed with a cover 48. Opposite of the cover 48, at the other pole tube's end at which the pole core 30 is located, the housing 46 is likewise closed by an element of the pole core 30 forming a flow disk 31.

[0062] The pole core 30 has a centric through bore 50, in which an actuation pin 52 is displaceably guided, for example for a valve element. A magnetic armature 54 in the pole tube 34 is mounted on an inner surfaces 36 of the pole tube 34 forming an armature running surface. The actuation pin 52 is actuatable by the magnetic armature 34 or, more precisely, by an armature bolt 56 connected to the magnetic armature 54.

[0063] The connection of both pole tube's structural parts 20, 26 by means of the plastic insert molding completely fills the gap 28 provided for the magnetic separation of the pole tube's structural parts. The continuous interior inner surface 36 serving as an armature running surface according to the inventive method is continuous and offset-free so that a guiding of the magnetic armature 54 is possible with minimal radial air gap 58.

[0064] Finally, it should be noted that the outer lateral surfaces of the pole tube's structural parts 20, 26 can be furnished with surface structures not shown in the Figures, for example in the form of knurling or grooves, prior to the insert molding to attain a better connection of the pole tube's structural parts 20, 26 with the nonmagnetic material.

[0065] For centering the magnetic armature 54 in the pole tube 34 with defined radial air gap 58 between outer lateral surface of the magnetic armature 54 and inner lateral surfaces 36 of the pole tube 34, a bearing foil (not shown in the Figure), for example of PTFE or plastic or a plastic-glass tissue, can be provided between the inner surface 36 of the pole tube 34 and the magnetic armature 54. This avoids a unilateral applying, connected with high magnetic transverse forces, of the magnet armature 54 to the magnetically conducting single parts of the pole tube 34.