GB2173351A

GB2173351A - A ferromagnetic multiple shell

Info

Publication number: GB2173351A
Application number: GB08602548A
Authority: GB
Inventors: Zsolt Szabo
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 1986-02-03
Filing date: 1986-02-03
Publication date: 1986-10-08
Also published as: GB8602548D0; GB2173351B

Abstract

A ferromagnetic multiple shell core 1 has a circular-cylindrical pot- shaped basic shape with two or more winding spaces 2, 3 arranged concentrically with respect to one another. The winding spaces are separated from one another by ring- shaped walls 4 have a joint central circular-cylindrical core 5 and are of different depths. The multiple shell core is particularly suitable for inductive close-range transmission systems for wireless transmission of measuring values between a movable machine part or vehicle part and a machine part or vehicle part that is stationary relative to the movable part, for example, for a type pressure control system. Because of the good decoupling of the magnetic circuits and the low winding capacitance, high crosstalk attenuation between the different signal circuits can be achieved together with an advantageous mechanical structure. <IMAGE>

Description

SPECIFICATION A ferromagnetic multiple shell core This invention relates to a ferromagnetic multiple shell core.

When using wireless measurement transmission by means of an inductive close-range transmission system, particularly between a stationary machine part or vehicle part and a machine part or vehicle part that is movable with respect to it, the problems of targeting control of the magnetic flux, of reducing stray fields and of improving the crosstalk attenuation between different signal levels are encountered.

With wireless measured-value transmitting systems, several signals must often be transmitted at the same time. For example, for the operation of a sensor on a rotating machine part or vehicle part, it is necessary to supply the sensor, by means of (wirelessly transmitted) energy signal, with the energy required for the measurement and the generating of the measurement transmitting signal.

Conventional (compressed iron) dust cores or ferrite cores are known, for example, from DE-AS 10 11 087. It is true that such devices known as shell or pot cores are intended for the enlargement or for the alignment of coil sections. When these are divided into halves and the halves are assigned to the stationary and movable machine or vehicle parts, respectively, they may be used for the bunching or concentrating of the magnetic flux of an inductive close-range transmitter system.

When several signals must be transmitted at the same time via several pairs of coils, it is necessary to wind several coils onto one shell core.

Because of the strong inductive coupling on one magnetic circuit and because of the high winding capacitance between the individual coils, very strong crosstalk between the signals of the individual signal levels is generated and must be eliminated by means of expensive filters before further processing.

DE-AS 12 77 460 discloses a ferromagnetic multiple shell core for electric coils which mitigates the problem of crosstalk attenuation.

However, due to its arrangement, the multiple shell core is completely unsuitable for the intended purpose because the individual coils are located far away from one another in the core material and are arranged partially vertically to one another.

The invention and preferred embodiments thereof are defined in the appended claims.

It is thus possible to provide a ferromagnetic multiple shell core for electric coils which has high crosstalk attenuation between the windings as well as a winding capacitance that is very small, which is especially suitable for close-range transmission, and which can be produced in a simple and cost-effective way.

Because of the separate winding spaces, good crosstalk attenuation with a low winding capacitance between the individual coils can be achieved. A compact construction can be achieved, the coils are arranged advantageously with respect to space, and the core can be produced in a simple and cost-effective way.

The invention will be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a double shell core constituting a preferred embodiment of the invention; Figure 2 is a top view of the double shell core of Figure 1; Figure 3 is a section on Line Ill-Ill of Figure 2; Figure 4 is a sectional view of two double shell cores facing each other in mirror-image fashion and having windings to provide, for example, part of an inductive measured-value transmitting system; and Figure 5 shows another embodiment in a view corresponding to Figure 3.

As an example of a ferromagnetic multiple shell core for electric coils, Figure 1 shows a double shell core 1 in a perspective view. The double shell core 1 has a pot-shaped circularcylindrical basic shape with circular-ringshaped exterior and interior winding spaces 2, 3 located concentrically to one another. The exterior winding space 2 and the interior winding space 3 are separated from one another by a ring-shaped wall 4. A circularcylindrical core 5 is arranged in the centre.

In Figure 3, the thickness of a bottom 6 of the double shell core 1 in the area of the exterior winding space 2 and of the interior winding space 3 is selected in such a way that a magnetic flux from an outside wall 7 or the ring-shaped wall 4 and penetrating the bottom 6 and the core 5 is subjected to no tapering of the cross-section with respect to the walls 4, 7. Further, the magnetic flux is also subjected to no tapering of the crosssection in the area of the radiuses of the bottom 6 of the exterior winding space 2 and the bottom of the interior winding space 3 that are located furtherest to the inside. The same is true for the core 5, which therefore, has a cross-section that corresponds approximately to the sum of the cross-sections of all walls 4, 7.

According to Figure 4, double-chamber shell cores 8, 9 are arranged so that they are in mirror-image relationship with respect to one another and each has an interior winding 10, 11 and an exterior winding 12, 13 representing a part of an inductive close-range transmission system, such as a tyre pressure control system. The double shell core 9 is mounted on a rotating machine part or vehicle part (not shown), such as a vehicle wheel, and the double shell core 8 is mounted on a part that is stationary relative to the rotating part (not shown), such as a wheel support.

For each rotation of the wheel, the double shell cores 8, 9 encounter one another once as shown, so that the coils 10, 11 and 12, 13 are inductively coupled with one another via an air gap 14 and can be used for the signal transmission.

By means of the interior pair 10, 11 of coils, an energy signal may, for example, be transmitted from the wheel support for the operation of a tyre pressure sensor mounted on the wheel. Also, by means of the exterior pair 12, 13 of coils, a measuring signal of a higher frequency and modulated by a measuring value is transmitted from the tyre pressure sensor to the wheel support, and from there, to an evaluating unit.

A system that is constructed in this way also permits relatively large air gaps 14 and permits a relatively large lateral offset without noticeably impairing the transmission qualities.

Figure 5 shows a triple shell core 15 having exterior 16, central 17 and interior 18 winding spaces for a total of three coils. In this way, the number of winding spaces can be expanded and can be individually adapted to the corresponding application.

The use of multiple shell cores of this type is not limited to tyre pressure control systems, but can, for instance, be used forprac- tically all cases of inductive close-range transmission systems in which more than one signal must be transmitted. These cores are particularly useful for arrangements in which a machine part or vehicle part can be moved relative to another part or relative to any stationary object.

When the double shell cores 8, 9 are placed directly on top of one another and are screwed together with one another, they can also be used as a core for transmitter systems with a galvanic separation between the windings

Claims

1. A ferromagnetic core comprising a cylinder which is closed at one end and open at the other end, an internal axially extending limb, and at least one internal annular wall extending from the closed end so as to define a plurality of internal annular spaces for accommodating a plurality of windings.

2. A ferromagnetic multiple shell core for at least two electric coils that are substantially decoupled from one another so that the windings of the coils are arranged in recesses of core parts and are almost completely surrounded by ferromagnetic material, wherein the multiple shell core has a circular-cylindrical pot-shape having several winding spaces located concentrically with respect to one another and separated from one another by ring-shaped walls, and a central circular-cylindrical core.

3. A ferromagnetic multiple shell core as claimed in claim 2, wherein the or each radially inwardly located winding space has a lower depth than the or each radially outwardly located winding space.

4. A ferromagnetic multiple shell core as claimed in claim 3, wherein each bottom portion of the multiple shell core defining a respective one of the winding spaces has at least a thickness such that magnetic flux from the radially outer wall defining the respective winding space and penetrating the bottom and the core is subjected to no tapering of the cross-section with respect to the walls and is also subjected to no tapering in the area the diameters of the bottom of the. respective winding space located radially innermost.

5. A ferromagnetic multiple shell core as claimed in any one of claims 2 to 4, wherein the cross-section of the central cylindrical core corresponds to the sum of the cross-sections of all hollow-cylinder-shaped walls.

6. A pair of ferromagnetic multiple shell cores each as claimed in any one of claims 2 to 5, arranged with their open ends facing one another and constituting part of an inductive close-range transmitter system, one of the cores being movable relative to the other core on an orbit so that the two multiple shell cores are cyclically or anticyclically opposite one another via a small air gap.

7. A pair of ferromagnetic multiple shell cores as claimed in claim 6, wherein the. multiple shell cores are part of an inductive closerange transmitting system for transmitting energy signals and/or measuring signals from a rotating machine part or vehicle part to a machine part or vehicle part that is stationary relative to the rotating part or from a stationary machine part or vehicle part to a machine part or vehicle part that rotates with respect to the stationary part.

8. A pair of ferromagnetic multiple shell cores as claimed in claim 6 or 7, wherein windings are located in the winding spaces and are operated at different frequencies with the radially outer windings operating at high frequencies.

9. A ferromagnetic shell core substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.