DD213085A1 - MAGNETIC SYSTEM WITH A RINGING CERAMIC PERMANENT MAGNET - Google Patents

Abstract

A magnet system having a ring-shaped ceramic permanent magnet has between two plates the permanent magnet and in the cylindrical cavity of the permanent magnet a core which is connected to one of the plates and protrudes into a cylindrical recess of the other plate and is separated from the latter by an air gap; a suitable design of the plates and the core to reduce volume, mass and leakage losses. The plates are therefore designed as flat Kegelstuempfe that touch the Grundflaechen the front surfaces of the permanent magnet and whose thickness is preferably zero at the edge of the permanent magnet. The core may be formed as a hollow cylinder or solid cylinder with a disc and with a plate consist of a piece. Core, plates and permanent magnet have a common geometric axis. The one plate and the end facing away from the core can be provided rotationally symmetrical to the axis with recesses.

Description

Helga Bühling P 925

Brno joke IPK: H 01 P, 7/02

21.12.1982

Title of the invention

Magnetic system with a ring-shaped ceramic permanent magnet

Field of application of the invention

The invention relates to a magnetic system with an annular permanent ceramic magnet having a central oscillating space and two substantially planar end faces, and with two plates, each of which is disposed adjacent to an end face and one of which is provided axially to the permanent magnet with a cylindrical core is, which protrudes through the resonant space, in a central recess of the other plate and is separated from this other plate by an air gap. Such magnet systems are used in loudspeakers.

2aDEL1982 * OS86ß ^! 7

.- 2 -. P 925 Characteristic of the known technical solutions

Are known ring magnet systems with permanent magnets made of oxide sintered materials, soft iron cover plates and soft iron core, in which the cover plates have substantially constant thicknesses. The thickness of the upper cover plate corresponds to the required depth of the air gap, and the thickness of the lower cover plate is equal to or greater than the thickness of the upper cover plate depending on the desired Lufttspaltinduktion. While the dimensions and shapes of the annular permanent magnet, the air gap and the air gap induction are adapted to the intended use, the geometry of the soft iron parts is given little importance, which is why they are often too voluminous and thereby burden the structure and weight of the ring magnet system. It is also already known a ring magnet system in which the permanent magnet and the soft iron components auxiliary magnets are assigned to thereby obtain a stray magnetic system without having to accommodate it in an additional pot. Apart from the fact that here in place of the pot at least one auxiliary magnet and arranged between the auxiliary magnet and the permanent magnet, adapted in thickness and shape cover plate are required, the auxiliary magnet is technologically difficult to manufacture by its shape and the ring magnet system loading size and mass Soft iron parts never reduced.

Object of the invention

The invention seeks to remedy the identified deficiency and a lightweight and kompendiöses magnet system 'can be created with an annular permanent ceramic magnet, which is favorably applicable for speakers of different types and sizes, but especially for large speakers.

Principle of the _Er-making

The invention is based on the object, the soft iron parts

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to give a suitable shape and thereby to ensure a low leakage low-magnetic system without the use of auxiliary magnets.

According to the invention the object is achieved in that each of the plates is formed as a flat truncated cone whose base surface of the associated end face of the permanent magnet is immediately adjacent, the top surface facing away from the associated end face and is substantially above the resonant space that the thicknesses ζ of Plates over the corresponding faces of the relationship. ·.

Z = rr-

1.05 T

In which By means of the air-gap induction, D "the pressure gauge of the core, IL, the outer diameter of the permanent magnet, d", the inner diameter of the permanent magnet, d the diameter of the plates., t ₁ the depth of the air gap and T the unit of measure Tesla. that the outer diameter of the plates at most half the height of the permanent magnet are smaller than the outer diameter of the permanent magnet and that the material cross section of the core is reduced. The plates and the core are made of soft magnetic material, preferably soft iron. They are arranged and formed in their cross-section perpendicular to the direction of flow of the magnetic field by the invention so that their'Mase is reduced to a minimum and the magnetic flux density at any point of its cross-section at right angles to the flow direction ifert the same., Which is less than or equal to Reducing the mass of soft iron pieces used for core and plates is particularly important for loudspeakers in portable devices and for high power loudspeakers An advantageous embodiment of the invention results when the one plate and the core out It is favorable for the mass reduction if the core has either the shape of a hollow cylinder with an inner diameter d "or, as a solid core (solid cylinder) outside the air gap area, to an outer diameter.

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knife dg · is tapered. The inner diameter of the hollow cylinder is given by the relationship ~

= IL. 1/1 - ^{1 L} II

y%. 1.05 τ *

This is the basic condition

^A L% · -τ * 1.05 T III

for avoiding supersaturation losses in the soft magnetic material, in which A ^ the cross section of the air gap and A- the soft iron cross section perpendicular to the direction of flow. For the smallest outside diameter | of the Tollzylinders-between the plates

^L 4%. t. , IV

Thus, it is said that the solid core between the plates can have a taper which, in addition to saving material, allows for an increase in the free vibration space for the loudspeaker coil. To reduce the stray flux, the core can have a conical recess axially to the core at its end face located in the vicinity of the air gap, the base surface of which lies in the end face of the core. For the same reason, the one plate connected to the core can have a conical recess axially of the core, whose base surface is arranged in the top surface of the one plate.

The relation I holds under the constraint condition Djj> d> dj ^. If d ^ ^ d ^ Dg-, then. the plate thickness

d. 1.05 T

If the outer diameter d of the plates is smaller by half the height tu * of the permanent magnet than its outer diameter D _n , the plate thickness ζ should be at the edge

B _T , t. , H,-

IPR IQ A ^ * (j H Λ ; -h; w · '- 5 -

^z o - 1, üi? T. (Ai-Dr.) VI

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or, in a favorable approximation

^z o ^ 2 ^(D M ~ ^d a>

his; it goes to zero for d = D ,, In the production of the core and the plates according to the above conditions not only material is saved, but it is simultaneously raised the Eutzfluß in the air gap.

The realization of the invention for small magnet systems in large numbers can be done by cold forming. Pur large high-performance loudspeakers, which are only produced in small numbers, plates and core can be made by forging or machining.

embodiments

The invention will be explained below with reference to the schematic drawing näger. Bs show:

Pig. 1 shows an axial section through an embodiment of the magnet system according to the invention,

Pig. 2 shows an axial section through a second embodiment of the magnet system according to the invention,

Pig. 3 is an axial section through a plate and

Pig «4 an axial section of the core of a magnet system according to the invention.

In Pig. 1, an annular permanent ceramic magnet 1 is two plates 2; 3 so assigned that this at the end faces 4; 5 of the permanent magnet 1 abut. The plates 2; 3 are as cones with curved generatrices 6; 7 trained. At the plate 2 UBd; a core 8 attached, which is ausgebil det as a hollow cylinder and the cavity 9 is arranged in extension of a recess in the plate 2. The plate 2 has a base 11 and a top surface 12. With the base 11 ·. is the plate 2 on the end face 4, In the top surface

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is as well as in the end face 13 of the core 8 a cone-shaped recess 14; 15 incorporated so that the base surface of the respective conical recess 14; 15 in the top surface 12-or · the end face 13 is located and that the cone tips are on an axis X ₁ ^- X ₁ , the common geometric axis of the recesses 9; 10; 14; 15 and the permanent magnet 1, the plates 2; 3 and the core is 8. The plate 3 has a likewise to the axis X ₁ -X ₁ axial recess 16, in which the core 8 protrudes so that its end face 13 with the top surface 17 of the plate 3 is approximately in a plane. Between the wall of the recess 16 and the free end of the core 8 there is an air gap 19, the depth t Decide decisively on them to be equipped speakers. The curvature of the edge! Lines 6; 7 corresponds essentially to the course of the magnetic flux. lines 20 in the plates 2; 3 and results from the formula (III).

In the left half of Fig. 1, the magnetic flux lines 20 are registered in the permanent magnet 1 from the magnetic pole N to the pole S and in the plates 2; 3 and run in the core 8 from the magnetic pole S to the pole II. Leakage flux 21 arise only to a small extent on the cylinder surface of the permanent magnet 1 and the air gap 19. If you look at the cones 2; 3 to think of cylindrical plates and present the core 8 solid and of larger diameter, as is common in the prior art, it is understandable that up to half of the soft magnetic material can be saved.

In Fig. 2, a magnet system is equipped with a permanent magnet 22 which is between two soft magnetic plates 23; 24 is arranged, which are formed as cones and with their base surfaces 25; 26, the end faces 27; 28 of the annular permanent magnet 22 touch. The generatrices 29; 30 of the cones 23; ·· are in a sufficiently approximate straight line. The plate 23 is made up of a solid core 31 and a cylindrical disk 32

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.•one piece. In the plate 23 and the disc 32 are per disc a conical recess 33; 34 incorporated, of which the recess 33 has curved generatrices and the recess straight generatrices. The plate 24 has a cylindrical recess 35, in which the disc 32, separated by an air gap 3δ, is located. In the Wähe the recess 35 has: the cone 24 a step 37. Such step is then to apply when the Ijuftspaltinduktion B _T considerably smaller than 1, OT, and therefore the calculated according to formula IV plate thickness ζ in the region of the air gap 3β to Results in values which are smaller than the air gap "deep t * required for the system. The magnetic system shown in Fig. 2, the effect of which is similar to that of Pig. 1 is rotationally symmetric to an axis Xq-X <3 »

In Pig * 3 a konisehe plate 38 with a base 39, curved generatrices 40th and a cylindrical recess 41 can be seen, which has a rotationally symmetrical to an axis X ^ -X ^ structure. For ease of manufacture, the cone 38 could be provided with straight generatrices 42 (shown in phantom). However, then the material consumption and the weight of the plate 38 would be larger *

FIG. 4 shows a core 44 provided with a cavity 43, the cavity 43 of which, unlike the core 8 in FIG. 1, has no chamfers.

Claims (6)

 - 8 - "P 925 invention claim A magnetic system comprising an annular permanent ceramic magnet having a central oscillating space and two substantially planar end faces, and having two plates, each of which is disposed adjacent one of the end surfaces and one of which is provided axially with a cylindrical core to the permanent magnet protrudes through the resonant space of the permanent magnet into a central recess of the other plate and is separated from this other plate by an air gap, characterized characterized that each of the plates is formed as a flat truncated cone whose base surface of the associated end face of the permanent magnet immediately adjacent, the top surface facing away from the associated end face and substantially above the resonant space, that the thicknesses ζ of the plates on the associated end faces of the relationship 'z3lI3 1.05T (D _M ² - where B _{T is} the air-gap induction, D ~ the outer diameter of the core, El. the outside diameter of the permanent magnet, dj, the inside diameter of the permanent magnet, d the diameter of the plates, t. the depth of the air gap and T the unit of measure in Tesla mean that the outer diameters of the plates are at most half the height of the permanent magnet smaller than the outer diameter of the permanent magnet and that the material cross section of the core is reduced. 2. magnet system according to item 1, characterized in that the core is designed as a hollow cylinder whose inner diameter 4t,. B
1 _ _J __ is. - 9.- P 925 3. Magnetic system after. Point 1, characterized in that. The core is formed as a solid cylinder and tapered below the air gap and in the vibrating space an outer diameter 1.05 T * ^{4 D} K 1/ Has. 4. magnet system according to item 2 and 3, characterized in that the one plate and the core consist of one piece. 5. magnet system according to item 4, characterized in that the core at its located in the iJahe the air gap face a conical recess axially to the core up 'has, the base surface in the end face of the core, -. ., 6. Magnetic system according to item 5, characterized in that one plate has a conical recess axially to the core.   has, whose base is arranged in the top surface of a plate .. - See 1 page drawings -