JP2008517573A - Magnet assembly for linear electromechanical machine - Google Patents

Abstract

Magnetic assembly for a linear electromechanical machine comprising an annular support (8) centered on the reciprocating axis of the machine. A magnet assembly (9) is attached to the annular support. The magnet assembly includes at least one annular portion (20) that is substantially a magnet. The annular part (20) has at least one non-conductive part (21, 22, 23, 25) extending in a substantially radial plane to at least half of the path through the wall of the annular part.
[Selection] Figure 1

Description

  The present invention relates to a magnet assembly for a linear electromechanical machine and a method for forming a magnet. In particular, the present invention relates to a magnet assembly for a linear motor or alternator.

  As is well known in the art, in an alternator, the movement of a magnet in the vicinity of a conductor induces a current in the conductor. In the case of a motor, the magnetic field in the magnet changes due to a change in the current flowing through the conductor, thereby moving the magnet.

  The present invention relates to an improved structure of a magnet assembly for use in such a machine. The present invention was designed for linear Stirling engines, particularly for linear free piston Stirling engines. However, as described above, the present invention is widely applicable to linear electromechanical machines.

  WO 97/13261 discloses a magnet assembly for a linear electromechanical machine. In particular, a support structure in the form of an annular drum having a plurality of slots extending in the reciprocating direction is provided. A plurality of magnets are mounted on the drum. In general, the number of magnets is equal to the number of slots. The slotted drum and the plurality of magnet segments are configured to reduce losses caused by eddy currents in the drum and magnet.

  The present invention aims to improve the magnet assembly of WO 97/13261 and to form a magnet assembly that has comparable efficiency but can be manufactured at a much lower cost and is suitable for mass production assembly. And

  According to a first aspect of the present invention, a magnetic assembly for a linear electromechanical machine comprising an annular support centered on a reciprocating shaft of the machine and a magnet assembly attached to the annular support. The magnet assembly comprises at least one annular portion that is substantially a magnet and is centered on the reciprocating shaft, the at least one annular portion being in a substantially radial plane, A magnetic assembly is provided having at least one non-conductive portion extending to at least half of the path through the wall of the annulus.

  The nonconductive portion serves to limit eddy current. The use of an annulus greatly simplifies the manufacturing process. In WO 97/13261, there are generally 10 magnet segments. Each of these magnet segments must be individually attached to the drum. In addition, each segment must be placed in the correct circumferential position so that it is accurately aligned with the adjacent segment and drum slot.

  In contrast, the annular portion of the present invention is easy to install because the number of discrete components is greatly reduced. Since the magnet can be mounted in any circumferential direction, the circumferential alignment of the magnet and the drum is not a problem.

  In its simplest form, the non-conductive part is formed by a slit. As a result, the nonconductive portion is effectively provided by the air gap. This is easy to manufacture and forms a lightweight magnet. However, the presence of one or more slits reduces the strength of the magnet. Accordingly, the non-conductive portion may be made of a solid non-conductive material when a high strength is required to enable the shape of the magnet to be maintained during the extension operation.

  The magnet assembly may be used with respect to the reciprocating or static part of the machine. In the first case, the annular support is a drum arranged to reciprocate along the axis of reciprocation when in use. In the latter case, the annular support is fixed, the core is reciprocated with respect to the drum, and a magnetic field is induced in the core.

  The present invention may be performed using one annular portion. However, it is preferred that a plurality of such annular portions are arranged in the axial direction. This increases the number of components, but is still significantly less than the number of components in WO 97/13261 and the circumferential alignment problem still does not arise.

  There are many possible forms of non-conductive parts that can be used. For example, the non-conductive portion may extend from an end surface facing the axial direction of the magnet, or may extend from a surface facing the radial direction.

  It has been found that one non-conductive part results in a significant reduction in eddy currents. Two spaced non-conductive portions may be provided to form a more tortuous path around the magnet. In this case, each non-conductive portion extends from the opposite surface of the magnet. In the case of two non-conductive parts, they are arranged in a staggered fashion and overlap so that any circle in the magnet centered on the axis of reciprocation intersects at least one non-conductive part. That is, there is no uninterrupted circumferential path around the magnet.

  Preferably, each non-conductive portion extends across at least 75% of the magnet and in some cases extends over as much as 90% of the magnet. The larger the range of non-conductive parts, the better the reduction of eddy currents.

  Alternatively, the non-conductive portion may extend completely across the magnet. In the case of a slit, only one such non-conductive part extends completely across the magnet. However, a plurality of such non-conductive portions may exist in the solid non-conductive portion.

  The non-conductive portion may be a separate component that is inserted into the slot of the annular portion. Preferably, however, the non-conductive component is formed integrally with the annular portion. This is the subject of the second aspect of the invention.

  According to the second aspect of the present invention, preferably, a method of forming an annular magnet using an annular mold having a central axis and a plurality of supply nozzles, wherein the nozzle is centered on the central axis. It is arranged in a circle corresponding to the annular mold and can move in the direction of the central axis, with at least one nozzle containing a powder non-conductive material and the remaining nozzles containing a powder magnetic material. In the method, lowering the nozzle into the mold, depositing a powder material, raising the nozzle when the material is dispensed to fill the mold, and removing the nozzle; Compressing and heating the powder material to form a ring and exposing the material to a magnetic field to form a magnetic pole. How to obtain is provided.

  This method provides a simple way to produce composite cores in a single operation.

  The magnetic field may be applied before or after the material is compressed and heated, but is preferably applied in both cases.

  Here, an example of a magnet assembly according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the basic components of a linear free piston Stirling engine to which the present invention can be applied. The Stirling engine includes a head 1 provided with a plurality of fins 2 heated by an external burner. A cooling circuit 3 is provided to remove heat from the middle part of the engine. A displacer 4 is located in the engine head. The displacer 4 extends through the engine downward in the axial direction and is attached to at least one leaf spring 6 fixed to the engine casing. Is attached to. Accordingly, the displacer 4 is mounted so as to reciprocate in the axial direction. A power piston 7 supported so as to reciprocate in the engine out of phase with the displacer 4 surrounds the rod 5. An annular drum 8 is attached to the power piston 7, and a magnet assembly 9 described in detail below is provided on the annular drum 8.

  The magnet assembly 9 is disposed so as to reciprocate in the axial direction within an air gap (gap) 10 of the stator 11. The stator 11 includes an outer annular winding and laminate assembly 12 and an inner core 14 made of a ferromagnetic material (for example, a soft magnetic composite material). This is not a permanent magnetized component, but may still be longitudinal slits (filled with non-conductive material or left hollow to reduce eddy currents induced during normal operation ). The magnet assemblies 9, 14 are made of a standard permanent magnet material such as iron neodymium. The operation of linear free pistons is well known in the art.

  The present invention relates to an improved structure of the annular magnet assembly 9 on the drum 8. Various other structures for the magnet are shown in FIGS.

  FIG. 2A shows an annular magnet 20 having a first axial slot 21 extending about 3/4 of the magnet down from the axial end face. The second slot 22 is cut into the opposite axial end face and extends a similar length across the magnet.

  In FIG. 2B, the axial slots are replaced with two opposing circumferential slots 23, 24 of the magnet 20.

  In FIG. 2C, one slit 25 is provided over the entire width of the magnet 20, so that a split ring configuration is effectively formed.

  Needless to say, many variations on the three structures are possible. For example, in FIGS. 2A and 2B, only one of the two slots may be required. Alternatively, more than two slots may be provided and there may be multiple slots extending around the magnet. Furthermore, the slot configurations may be mixed so that the slots in two or three of the embodiments are combined on one magnet.

  Of course, the exact form of the slot is determined according to the performance requirements. These provide a trade-off between reduced eddy currents on the one hand and ease of handling and manufacturing costs on the other hand. One slot, such as the slot 21 shown in FIG. 2A, provides a magnet that is easy to handle and significantly reduces eddy currents. To further reduce eddy currents, the staggered slot arrangement of FIG. 2A or 2B can be provided in conjunction with the split ring configuration of FIG. 2C. However, this is more expensive to manufacture and more difficult to handle.

  2A-2C have been described in connection with a non-conductive material that is a slit. However, the illustrated embodiment can be similarly applied to a solid non-conductive material. In this case, instead, the area occupied by the slit is filled with a non-conductive material. FIG. 2C shows one slit extending across the full width of the magnet. Only one such slit can be provided, otherwise the magnet becomes two components. However, if a solid non-conductive material is used, this non-conductive material can extend across the full width of the magnet at multiple locations while maintaining the component as a single annular component.

  The slits of FIGS. 2A-2C can be filled with a suitable material to form an annular ring having a solid non-conductive material insert. However, the current priority is to form an annular magnet with a solid non-conductive portion in one manufacturing process described with reference to FIGS.

  Preferred solid non-conductive materials are ceramic powder or thermoplastic.

  The illustrated arrangement is adapted to form two regions of non-conductive material that extend completely across the width of the magnet.

  The apparatus includes a mold 30 having an annular recess 31 around the main shaft 32. Above the annular recess 31, there is a nozzle 33 disposed around the main shaft 32 and mounted on a nozzle ring 34. These nozzles can enter the annular recess 31 along the shaft 32 and can exit the annular recess 31. Most of the nozzle 33 is filled with powdered magnetic material. However, the two nozzles 33A on both sides are filled with a non-conductive material.

  In order to allow the injection of powder into the lower region of the recess, with the nozzles entering the annular recess 31 and their outlets positioned near the bottom of the recess, the nozzle is used using a gravity feed system Powder is fed into the upper end of the ring. A low-speed gas supply device can be used as an alternative to the gravity supply system.

  A magnetic field is applied to the mold during the feeding process to ensure accurate alignment of the magnetic particles during the filling process. The nozzle ring 34 is gradually raised with minimal agitation to prevent mixing of different feed materials.

  When the mold is filled, the nozzle ring 34 is removed and thus the magnetic field is removed. A solid compaction ring (not shown) is gradually lowered into the mold to compress the mixture. The mold is positioned in the furnace, at which point the furnace is raised to its operating temperature without moving the mold. Thereby, the material in a mold is sintered and one ring which consists of two materials is formed. The ring is removed from the mold and allowed to cool, after which the ring is subjected to additional magnetic fields to reinforce the magnetic pattern and form the correct number of poles.

  FIG. 5 shows the configuration of the magnet drum 8 and the magnet assembly 9 in more detail. A flange 15 is provided at the lowermost end of the drum 8 so that the drum can be attached to the power piston 7. The drum has an annular form and is provided with a plurality of slots 16 extending in the axial direction according to the teachings of WO 97/13261. The slot 10 can also extend in an oblique direction. The magnet assembly includes four annular magnets, that is, two main magnets 20 and two spring magnets 26. The main magnet 20 may be configured in accordance with any of the above-described FIGS. 2A-2C, or may be configured in accordance with any alternative means described with respect to these figures. The spring magnet 26 is an annular magnet having a polarity opposite to that of the main magnet, and is provided to generate a restoring force when the movement of the power piston 7 approaches a specific preset limit. Such spring magnets are well known in the art.

  The magnets 20 and 26 are disposed on the drum in a state where the spring magnet 26 is in contact with the annular lip 27 which gives the drum rigidity in the radial direction, and are fixed to a predetermined position using an adhesive. . Thereafter, the drum is bolted to the lower end of the power piston 7, and the magnet 9 is inserted into the air gap 10.

It is a schematic sectional drawing of the linear free piston Stirling engine which can apply this invention. 1 illustrates one form of magnet suitable for use with the present invention. 1 illustrates one form of magnet suitable for use with the present invention. 1 illustrates one form of magnet suitable for use with the present invention. It is a schematic sectional drawing of the mold and nozzle for forming a magnet according to the 2nd aspect of this invention. It is a schematic plan view which shows the layout of the nozzle shown by FIG. It is an exploded sectional view showing assembly of a magnet and a drum.

Claims (17)

A magnetic assembly for a linear electromechanical machine,
An annular support centered on a reciprocating axis of the linear electromechanical machine, and a magnet assembly attached to the annular support;
The magnet assembly includes at least one annular portion that is substantially a magnet and is centered on the reciprocating shaft, the at least one annular portion being in a generally radial plane and a wall of the annular portion. A magnetic assembly having at least one non-conductive portion extending to at least half of the path through it.   The magnetic assembly according to claim 1, wherein the non-conductive portion is a slit.   The magnetic assembly of claim 1, wherein the non-conductive portion is a solid non-conductive material.   The magnetic assembly according to claim 3, wherein the non-conductive portion is formed integrally with the annular portion.   The magnetic assembly according to claim 3, wherein the non-conductive portion is a component inserted into a slot of the annular portion.   6. A magnetic assembly according to any one of the preceding claims, wherein the annular support is a drum arranged to reciprocate along the axis of reciprocation in use. The magnetic assembly is a stator;
6. Magnetic assembly according to any one of the preceding claims, wherein the annular support is fixed with respect to a reciprocating component.   The magnetic assembly according to claim 1, wherein the nonconductive portion extends from a surface facing the axial direction of the magnet.   The magnetic assembly according to claim 1, wherein the non-conductive portion extends from a surface facing the radial direction of the magnet.   The magnetic assembly according to claim 1, comprising two non-conductive parts, each non-conductive part extending from an opposite surface of the magnet.   11. A magnetic assembly according to any one of the preceding claims, wherein the non-conductive portion or each non-conductive portion extends across at least 75% of the annular portion.   The magnetic assembly of claim 11, wherein the non-conductive portion or each non-conductive portion extends across approximately 90% of the annular portion.   The magnetic assembly of claim 2, wherein the slit extends completely across the annulus.   The magnetic assembly according to any one of claims 3 to 5, wherein the non-conductive portion or each non-conductive portion extends completely across the annular portion. A method of forming an annular magnet using an annular mold having a central axis and a plurality of supply nozzles, wherein the nozzle is arranged in a circle corresponding to the annular mold around the central axis, A method capable of moving in the direction of the central axis, wherein at least one nozzle contains powdered non-conductive material and the remaining nozzles contain powdered magnetic material;
Lowering the nozzle into the mold;
Dispensing powder material into the mold;
Raising the nozzle when the material is dispensed and the mold is filled;
Removing the nozzle;
Forming a ring by compressing and heating the powder material;
Exposing the material to a magnetic field to form a magnetic pole.   The method of claim 15, wherein the material is exposed to a magnetic field before the material is compressed and heated.   17. A method according to claim 15 or 16, wherein the material is exposed to a magnetic field after the material is compressed and heated.

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