WO2012032399A2

WO2012032399A2 - Electromagnetic composite material (emcm)

Info

Publication number: WO2012032399A2
Application number: PCT/IB2011/002092
Authority: WO
Inventors: Martin Gudem
Original assignee: Norwegian University Of Science And Technology (Ntnu)
Priority date: 2010-09-07
Filing date: 2011-09-07
Publication date: 2012-03-15
Also published as: WO2012032399A3

Abstract

A composite drive unit includes a composite material including conductive fibers 14 as an integrated part of the composite material. The conductive fibers 14 can be organized in different patterns, and each of the conductive fibers is terminated to an electrical conductor. A material for a composite drive unit includes a plurality of conductive fibers 14 arranged in a predetermined pattern 30. The plurality of conductive fibers 14 are embedded in a matrix material 12. The plurality of the conductive fibers 14 is connectable to a source of electricity to generate a magnetic field 18 for operating the composite drive unit.

Description

ELECTROMAGNETIC COMPOSITE MATERIAL (EMCM)

CROSS-REFERENCE TO RELATED APPLIC ATION

[0001] This application claims priority to U.S. Provisional Application No.

61/380,573, filed on September 7, 2010, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the invention:

[0002] The present invention is related to electromagnetic composite materials

(EMCM). In particular, the present invention is related to electromagnetic composite materials (EMCM) that can be used as part of a composite drive unit.

SUMMARY OF THE INVENTION

[0003] The present invention is directed to a composite drive unit, comprising: a composite material including conductive fibers as an integrated part of the composite material, wherein the conductive fibers can be organized in different patterns, and wherein each of the conductive fibers is terminated to an electrical conductor.

[0004] According to an embodiment of the present invention, the composite drive unit further comprises a stator; and a moving part, wherein said stator and/or said moving part includes said conductive fibers embedded in a matrix material, said conductive fibers being connected to a source of electricity to generate a magnetic field.

[0005] According to an embodiment of the present invention, the composite drive unit is constructed as an electric motor.

[0006] According to an embodiment of the present invention, the composite drive unit further comprises a coil, which is an integral structural component, wherein the coil functions as reinforcement fiber in a composite material, and wherein the fibers may be ferromagnetic or ferrimagnetic. [0007] According to an embodiment of the present invention, the ferromagnetic or ferrimagnetic fibers may also be integrated in the material, so as to guide the magnetic flux, and may also be used as electromagnetic conductors.

[0008] According to an embodiment of the present invention, the composite drive unit is constructed as an electromagnetic generator.

[0009] According to an embodiment of the present invention, the composite drive unit is constructed as a wheel motor, windmill or tidewater generator, a high-speed motor or generator, or a transformer.

[0010] The present invention is also directed to a material for a composite drive unit, comprising: a plurality of conductive fibers arranged in a predetermined pattern, said plurality of conductive fibers being embedded in a matrix material, wherein said plurality of the conductive fibers are connectable to a source of electricity to generate a magnetic field for operating the composite drive unit.

[0011] The present invention is also directed to a method of making a composite material for a composite drive unit, comprising the steps of: arranging a plurality of conductive fibers in a predetermined pattern; embedding said plurality of conductive fibers in a matrix material to make a composite material; and etching edges of the composite material, wherein said plurality of conductive fibers are connectable to a source of electricity to generate a magnetic field for operating the composite drive unit.

[0012] According to an embodiment of the present invention, the method of making a material for a composite drive unit further comprises the steps of: combining the plurality of conductive fibers with structural fibers; and winding the plurality of conductive fibers and the structural fibers on a mandrel, wherein said step of embedding the plurality of conductive fibers in a matrix material includes adding the matrix material during the winding process.

[0013] According to an embodiment of the present invention, the method of making a material for a composite drive unit further comprises the steps of: weaving the plurality of conductive fibers into plies with structural fibers; and assembling the plies, wherein said step of embedding the plurality of conductive fibers in a matrix material includes adding the matrix material during the weaving and assembling steps.

[0014] According to an embodiment of the present invention, the method of making a material for a composite drive unit further comprises the steps of: providing a base having a chamfered surface, a plurality of pins and a central peg; and winding structural fibers around the pins and the central peg, wherein the structural fibers are maintained in close contact with the base. [0015] The present invention is also directed to a method of making a composite material for a composite drive unit further comprises the steps of: inserting pins into a foam base covered with a non-stick material; winding a plurality of conductive fibers in predetermined patterns using the pins to hold the plurality of conductive fibers in place; and embedding said plurality of conductive fibers in a matrix material to make a composite material, wherein said plurality of conductive fibers are connectable to a source of electricity to generate a magnetic field for operating the composite drive unit.

[0016] According to an embodiment of the present invention, the method of making a composite material for a composite drive unit further comprises the steps of: covering the embedded conductive fibers with a sheet of non-stick material; pressing a foam block onto the non-stick material, so that the pins protrude through a top of the non-stick material and into the foam block, resulting in compression on the embedded conductive fibers; curing the embedded conductive fibers while under compression; and removing the foam-blocks, nonstick materials, and pins to form the composite material.

[0017] The EMCM (Electromagnetic Composite Material) according to the present invention uses conductive fibers as an integrated part of a long-fiber composite. The conductive fibers can be organized in different patterns, and each conductive fiber is terminated to an electrical conductor, so as to make the EMCM exhibit electromagnetic properties. The material has the potential of offering increased design flexibility and improved performance in electromagnetic devices, such as motors, generators, resonators, solenoids, etc.

[0018] Motors and generators using the EMCM can be designed with basis in existing coreless machinery. Coreless machines exclude the use of ferromagnetic cores as a means of directing the magnetic flux. Benefits associated with this technology include more lightweight design solutions. Furthermore, enclosing the conductive fibers inside a nonmagnetic structure will reduce or eliminate unintended buckling of rotor and/or stator components, which can be experienced in axial flux permanent magnets (AFPM) and similar structures. This property is particularly important for designing large-scale machines.

[0019] Ferrimagnetic and/or Ferromagnetic fibers, for example made from ferritic steel, may also be integrated in the material, so as to guide the magnetic flux. These fibers can be terminated, thereby serving as electrical conductors as well as flux-carriers.

[0020] The composite material may include structural fibers, which serve solely as reinforcement to the overall structure (e.g. glass fiber, carbon fiber, etc.). [0021] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: The invention will now be explained in more detail with reference to the appended drawings, wherein:

[0023] Figure 1 is a schematic view illustrating the composition of a long fiber composite;

[0024] Figure 2 is a schematic view illustrating conductive material integrated into a sandwich structure;

[0025] Figure 3 is a schematic view illustrating a different orientation of the structural and conductive fibers;

[0026] Figure 4 is a schematic view illustrating a magnetic field resulting from imposing an electric current in the conductive fibers;

[0027] Figure 5 is a schematic view illustrating a piece of EMCM where the conductive fibers are made from a ferrimagnetic or ferromagnetic material;

[0028] Figure 6 is a schematic view illustrating the same piece of EMCM as in Figure

5, but with an electric current running through the upper and lower layer;

[0029] Figure 7 is a photograph illustrating a manual prototype before epoxy resin is added;

[0030] Figure 8 is a photograph illustrating a manual prototype after curing;

[0031] Figure 9 is a photograph illustrating a foam base, release liner, pattern markup, and guiding pins;

[0032] Figure 10 is a photograph illustrating plies of reinforcement fibers and a winding tool;

[0033] Figure 11 is a photograph illustrating matrix material added;

[0034] Figure 12 is a photograph illustrating the part being cured under compression;

[0035] Figure 13 is a photograph illustrating the part after compression; [0036] Figure 14 is a photograph illustrating the trimmed part after removal of the release liners and guiding-pins;

[0037] Figure 15 is a photograph illustrating the center peg and chamfered sides keeping fibers close to base;

[0038] Figures 16a, 16b and 16c are schematic views illustrating an AFPM based on

EMCM technology, wherein Figure 16a illustrates the entire construction; Figure 16b illustrates the stator; and Figure 16c illustrates the rotor; and

[0039] Figure 17 is a schematic view illustrating conductive fibers arranged on a 3- phase configuration, and the resulting magnetic field.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The EMCM is developed with a basis in long-fiber composites. Long-fiber composites gain their strength from structural fibers (e.g. glass or carbon fibers), held together by a matrix material (e.g. epoxy). Figure 1 illustrates the make-up of a typical long- fiber composite. In Figure 1, a plurality of structural fibers 10 is illustrated stacked up in three layers with the longitudinal axis of each fiber being oriented in the same direction. A matrix material 12 occupies the volume between the fibers. However, the fibers 10 may be oriented in layers, or plies in different directions, so as to achieve direction-specific mechanical properties.

[0041] As illustrated in Figure 2, EMCM uses conductive fibers 14 (e.g. thin wires), which are integrated into a sandwich structure. The conductive fibers 14 may consist of copper, steel, aluminum, or any other material with satisfactory electric conductivity. The conductive fiber or wire may be pre-coated with insulation (not shown), so as to prevent short-circuiting. The insulation is etched off at the contact points where the conductors are connected to an electric circuit.

[0042] As illustrated in Figure 3, the conductive fibers may be oriented in a direction different from that of the structural fibers. Furthermore, the sandwich construction may be based on conductive fibers 14 serving as structural elements, eliminating the need for separate structural fibers 10.

[0043] Figure 4 illustrates a magnetic field 18 resulting from imposing an electric current 16 in the conductive fibers 14.

[0044] Figure 5 illustrates a piece of EMCM where the conductive fibers are made from a ferrimagnetic or ferromagnetic material. Imposing an electric current 16 in one layer induces a magnetic field 18 in the perpendicular layers. [0045] Figure 6 shows the same piece of EMCM as in Figure 5, but with an electric current 16 running through the upper and lower layer. This imposes a magnetic field 18, which is carried by the center layer.

[0046] In Figures 4 to 6, the conductors are not shown. However, the arrows indicate the electric current 16 resulting from terminating the conductive fibers 14.

[0047] The EMCM can be manufactured using processes similar to those associated with the production of other long-fiber composites. However, the manufacturing process requires high precision to avoid tearing off the conductive fibers 14 and ensuring that conductors are terminated properly. Manufacturing methods include:

1. Filament winding

[0048] Conductive fibers 14 are combined with structural fibers 10 and wound onto a mandrel. Matrix material 12 is added in the winding process. The edges of the resulting component are etched, and the conductive fibers are soldered to connector points.

2. Lay-up

[0049] Conductive fibers 14 are woven into plies with structural fibers 10. Plies are assembled and matrix material 12 is added in a lay-up process. The edges of the resulting component are etched, and the conductive fibers are soldered to connector points.

3. Pin-guided winding process (see below)

[0050] Two EMCM prototypes have been developed using a process here referred to as the "pin-guided winding process." The second prototype was manufactured using a semi- automated process where the conductive fiber 14 was wound using a CNC-machine (Computer Numerical Control). The ping-guided winding process is suitable for making flat or curved parts with fiber-orientation that changes direction while staying parallel to the part surface. The process includes the following steps:

1. A foam-base is prepared with a release liner;

2. Pins are inserted for each corner of the pattern;

3. Conductive fibers 14 are wound around pins using CNC machinery;

4. Fibers are applied by hand (lay-up) or by CNC machinery (winding);

5. Steps 4 and 5 are repeated to create a sandwich construction;

6. Matrix material 12 is added;

7. Upper release liner is installed; 8. The part is put under compression (and/or vacuum) and cured;

9. Release liner and guiding pins are removed; and

10. The part is trimmed.

[0051] Figure 7 shows a prototype made using a manual pin-guided winding process before epoxy resin is added. Copper wire (conductive fibers 14) was fed through the tip of an automatic pencil 22, and glass-fibers (structural fibers 10) were wound around a foam base 24. The pins 26 served as guides for both the conductive fibers 14 and the structural glass- fiber (structural fibers 10). The workpiece is made up from several layers of copper wire and glass fiber stacked onto each other.

[0052] In Figure 7, the pins 26 are made of metal. However, it should be understood that other materials such as plastic or glass may be more suitable. For example, pins made of thermoplastic material may be molten after the part is cured, making the removal process easier.

[0053] Figure 8 shows the final part after the matrix material 12 has been added and the part has been compressed and cured. This test was conducted without covering the foam base with non-stick film, and the EMCM is consequently glued onto the foam base 24.

[0054] The final part in Figure 8 will then be trimmed, and once the portion of the conductive fibers 14 outside of the matrix material 12 is cut, the terminal ends of the conductive fibers 14 can be connected to an electrical conductor (at 27).

[0055] Figure 9 shows the foam base 24 used in a semi-automated pin-guided winding process. The foam base 24 has been covered by a release liner 28, and a pattern 30 has been sketched out using a felt pen guided by a CNC machine. Pins 26 have been placed in each corner of the pattern 30.

[0056] The conductive wire (conductive fibers 14) are wound around the pins 26 using a CNC machine, and plies of reinforcement fibers (structural fibers 10) are added. The process is repeated to create a desired sandwich-structure.

[0057] Figure 10 shows the workpiece, which is made up from multiple plies of reinforcement fibers (structural fibers 10), stacked with conductive wire (conductive fibers 14).

[0058] As shown in Figure 11, matrix material 12 is added, and the part is cured under compression (see Figure 12). In Figures 13 and 14, the final product is illustrated. Once the final product is trimmed, the terminal ends of the conductive fibers 14 extending out of the matrix material 12 can be connected to an electrical connector (at 27). [0059] Whereas the above semi-automated process used fiber mats as the structural fibers 10, the foam base 24 used in this process has also been designed to work with fiber strands as the structural fibers 10, laid out by a CNC machine. Keeping the fibers close to the base represents a challenge when using this method, since loose fibers may interfere with the routing of conductive fibers 14. Structural fibers 10 are wound around needles 34 positioned at a chamfered edge 36 below the final part surface, thereby being pulled towards the base 24. A peg 32 with a tapered surface is placed at the center for the base 24. Winding the structural fibers 10 around or partly around the peg ensures good contact between base and structural fibers 10 at the center (Figure 15).

[0060] Manufacturing processes 1 and 3 described above, (filament winding and pin- guided winding) are not likely to require removal of matrix material, since the conductive fibers 14 can be guided to a termination point outside the final part. Etching will be needed to remove any insulation material (if applied) from the conductive fibers 14. This is standard procedure when working with electromagnetic coils.

[0061] Manufacturing process 2 described above (lay-up) uses pre- woven mats consisting of conductive fibers 14 and structural fibers 10. The ends of the conductive fibers 14 in this process will either have to be separated from the reinforcement fibers before matrix material 12 is added (un-sewing the edges and separating the fiber ends will work). Alternatively, grinding and/or dissolving the matrix material 12 covering the material edges will be necessary if the ends of the conductive fibers 14 have not been separated from the rest of the part before matrix is added. Other matrix materials such as thermoplastics, may be more suitable for this process.

Example

[0062] The following example describes a 3-phase axial flux permanent magnet

(AFPM) machine based on EMCM technology. An AFPM uses a magnetic field parallel to the machine's axle 4 in creating torque. The short distance between the opposing magnetic poles of the two stators 2 eliminates the need for a ferromagnetic core for guiding the magnetic flux. The machine is made up from two stators 2 consisting of permanent magnets backed by a steel disc, which provides structural support and guides the magnetic field (see Figure 16a). The rotor 1, which is made from EMCM, is attached to the axle 4, which is held in place by two bearings 3. The pin-guided winding process described above may be suitable for manufacturing the rotor 1. [0063] The conductive fibers are wound according to the pattern illustrated in Figure

17. Imposing electric current through the conductors will result in a magnetic field, as indicated by the arrows (dot=arrow tip, cross=arrow tail). An electric controller or a mechanical system based on brushes contacting a commutator can be used in changing polarity of the three conductors, causing the magnetic field to change direction. The pattern indicated in Figure 17 is curved around a center axis, resulting in a disc-shaped rotor, as shown in Figure 16c.

[0064] One of the benefits of EMCM is that the electrical conductors represent an integrated part of the structural support. As a result, a rotor made from EMCM will be more lightweight and support higher rotational speed compared to traditional designs where separate coils of copper are held in place by a mechanical structure.

[0065] Enclosing the conductive fibers inside a non-magnetic structure will also reduce or eliminate unintended buckling of rotor and/or stator components, which can be experienced in axial flux permanent magnet (AFPM) machines and similar structures. This property is particularly important for designing large-scale turbines. Traditional, large- diameter rotors made from ferromagnetic material will be affected by the magnetic field in which the coils travel to produce electricity. The rotors must exhibit high bending stiffness, so as to avoid sticking to the permanent magnets. EMCM is expected to eliminate this problem, supporting the development of large-diameter, high-power, and lightweight axial flux generators.

[0066] Parts made from EMCM are sealed units, a quality that can make them particularly suitable for harsh operating conditions, such as corrosive environments, or underwater installations.

[0067] The EMCM-technology may offer increased design flexibility and improved performance in electromagnetic devices, such as motors, generators, resonators, solenoids, etc. Application areas that may benefit from the introduction of EMCM include:

1. Wheel motors

[0068] The concept may offer significant weight savings, thereby reducing the unsprung mass when installed in cars, scooters, etc.

2. Windmill or tidewater generators

[0069] The concept may offer significant weight savings, easing the structural requirements for such installations. 3. Motors and/or generators for harsh operating environments

[0070] Parts made from EMCM are sealed units, a quality that can make them particularly suitable for harsh operating conditions, such as corrosive environments, or underwater installations.

4. High-speed motors/generators

[0071] A rotor made from composite material may offer higher strength, and thus permit higher angular speed for motors/generators. This may be particularly relevant for large-scale generators.

5. Lightweight, low-cost, and/or flexible power transformers

[0072] An AC transformer can be made by installing two or more coil-shaped circuits on a patch of material. AC current is run through the input coil, imposing a magnetic field. The changing magnetic field induces electricity in the output coil(s).

6. Curved or flat plates

[0073] Can be used in setting up a steady or varying magnetic field, applicable for transmitting electricity wirelessly or support propulsion and/or elevation for mag-lev (magnetic levitation) designs.

[0074] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

What is claimed is:

1. A composite drive unit, comprising:

a composite material including conductive fibers (14) as an integrated part of the composite material,

wherein the conductive (14) can be organized in different patterns, and wherein each of the conductive fibers (14) is terminated to an electrical conductor (27).

2. The composite drive unit according to claim 1, further comprising:

a stator (2); and

a moving part (1),

wherein said stator (2) and/or said moving part (1) includes said conductive fibers (14) embedded in a matrix material (12), said conductive fibers (14) being connected to a source of electricity to generate a magnetic field (18).

3. The composite drive unit according to claim 1, wherein the composite drive unit is constructed as an electric motor.

4. The composite drive unit according to claim 1, further comprising a coil, which is an integral structural component, wherein the coil functions as reinforcement fiber in a composite material, and wherein the fibers may be ferromagnetic or ferrimagnetic.

5. The composite drive unit according to claim 4, wherein the ferromagnetic or ferrimagnetic fibers may also be integrated in the material, so as to guide the magnetic flux, and may also be used as electromagnetic conductors.

6. The composite drive unit according to claim 2 wherein the composite drive unit is constructed as an electromagnetic generator.

7. The composite drive unit according to claim 6, wherein the composite drive unit is constructed as a wheel motor, windmill or tidewater generator, a high-speed motor or generator, or a transformer.

8. A material for a composite drive unit, comprising: a plurality of conductive fibers (14) arranged in a predetermined pattern (30), said plurality of conductive fibers (14) being embedded in a matrix material (12),

wherein said plurality of the conductive fibers (14) are connectable to a source of electricity to generate a magnetic field for operating the composite drive unit.

9. A method of making a composite material for a composite drive unit, comprising the steps of:

arranging a plurality of conductive fibers (14) in a predetermined pattern (30);

embedding said plurality of conductive fibers (14) in a matrix material (12) to make a composite material; and

etching edges of the composite material,

wherein said plurality of conductive fibers (14) are connectable to a source of electricity to generate a magnetic field for operating the composite drive unit.

10. The method of making a material for a composite drive unit according to claim 9, further comprising the steps of:

combining the plurality of conductive fibers (14) with structural fibers (10); and winding the plurality of conductive fibers (14) and the structural fibers (10) on a mandrel,

wherein said step of embedding the plurality of conductive fibers (14) in a matrix material (12) includes adding the matrix material (12) during the winding process.

11. The method of making a material for a composite drive unit according to claim 9, further comprising the steps of:

weaving the plurality of conductive fibers (14) into plies with structural fibers (10); and

assembling the plies,

wherein said step of embedding the plurality of conductive fibers (14) in a matrix material (12) includes adding the matrix material (12) during the weaving and assembling steps.

12. The method of making a material for a composite drive unit according to claim 9, further comprising the steps of: providing a base (24) having a chamfered surface (36), a plurality of pins (26, 34) and a central peg (32); and

winding structural fibers (10) around the pins (26, 34) and the central peg (32), wherein the structural fibers (10) are maintained in close contact with the base (24).

13. A method of making a composite material for a composite drive unit, comprising the steps of:

inserting pins (26) into a foam base (24) covered with a non-stick material (28);

winding a plurality of conductive fibers (14) in predetermined patterns (30) using the pins (26) to hold the plurality of conductive fibers (14) in place; and

embedding said plurality of conductive fibers (14) in a matrix material (12) to make a composite material,

wherein said plurality of conductive fibers (14) are connectable to a source of electricity to generate a magnetic field (18) for operating the composite drive unit.

14. The method of making a composite material for a composite drive unit according to claim 12, further comprising the steps of:

covering the embedded conductive fibers (14) with a sheet of non-stick material (28); pressing a foam block (24) onto the non-stick material (28), so that the pins (26) protrude through a top of the non-stick material (28) and into the foam block (24), resulting in compression on the embedded conductive fibers (14);

curing the embedded conductive fibers (14) while under compression; and

removing the foam-blocks (24), non-stick materials (28), and pins (26) to form the composite material.