KR20190021375A - Rotary actuator - Google Patents

Abstract

An actuator for high rotational speed applications using a stator using laminated features to reduce eddy current losses in the stator. This configuration allows for a high number of poles while providing the efficiency and fast gain of the laminated configuration. Laminated configurations are very difficult for high pole lightweight motors, but embodiments of the device provide other benefits such as low manufacturing costs, high heat dissipation, integrated cooling channels, and lightweight configurations, as well as structural strength and stiffness. Many of these benefits are due to the use of laminate sandwiches of non-magnetic, thermally conductive materials such as anodized aluminum as structural members of the stator.

Description

Rotary actuator

Actuator.

A high pole count motor has many advantages such as the possibility for high torque and light weight. In WIPO published patent application WO2017024409A1 it has been found that a solid stator can provide adequate performance with respect to minimizing eddy current when the speed is relatively low, such as when used in robotics lost. For higher speed applications, the use of a laminate is desirable to reduce eddy current losses. The problem is that high pole axial motors have very thin profiles (if they are to take advantage of such torque to weight potential) and are very difficult to construct with laminates. For example, when a single rotor and single stator configuration is used, the force pulling the stator and rotor together across the airgap is a glue that keeps the laminated structure together -line to shear to prevent the air gap from being maintained.

Rotary actuators solve this problem in a number of ways, including the use of a dual rotor configuration in which the stator is located between two rotors. An advantage of such a configuration is that the magnetic force on the stator is always reasonably the same in both axial directions on each of the posts. This reduces the load on each of the posts and reduces the stress on each of the glue lines in the stator assembly. The tangential forces on each of the posts may also be very high when under full power, but these forces are also balanced on each post so that glue lines are not always subject to high stresses.

Thus, in one embodiment, as an electric machine,

A stator-rotor disposed between the rotors is mounted on a bearing for rotation about a stator about the axis of the electric machine, the rotor being separated from the stator by respective air gaps; The stator is formed of a structural member, each structural member is formed of a laminate, each laminate having a minimum dimension extending in the axial direction; Each structural member having a slot and a magnetic post, the magnetic post being secured within the slot for support of the magnetic post by the structural member; And at least one electrical conductor disposed about the post to produce a series of commutated electromagnetic poles.

Embodiments of rotary actuators will now be described by way of example with reference to the drawings, in which like reference numerals refer to like elements.
1 shows a rotor with a magnet, a thrust bearing, a four-point contact bearing, a stator with a laminated post, a laminated structural member of a stator, a solid structural member, and a high- Lt; / RTI >
Figure 2 is an illustration of an exemplary embodiment in which a laminated post is placed between laminated structural members.
3 is a view of a laminated structural member of a stator illustrating a preferred stack layup of lamination. Wherein a radial cut is radially inwardly or outwardly of the stator post slot and alternating with respect to each adjacent layer.
Figure 4 illustrates the installation of a laminated stator post into a laminated structural member of the stator in the absence of a solid structural member.
Figure 5 illustrates the installation of a laminated stator post into a laminated structural member of the stator in the presence of a solid structural member having mounting features.
Figure 6 shows how the eddy current path is interrupted by a formed radial notch in both the inward and outward sides of the stator post slot in the laminate of the laminated structural element.
7 is a cross-sectional view of a stator and rotor for showing the orientation of magnets in the rotor and the flux path across the laminated stator posts;
8 is a view of a final lamination assembly having two laminated structural pieces and a laminated stator post.
Figure 9 is a cutaway view of a stator with some posts and coils removed.

A rotating actuator using a dual rotor configuration in which the stator is located between two rotors is disclosed. The advantage of this configuration is that the magnetic force on the stator is always reasonably the same in both axial directions on each of the posts. This reduces the load on each of the posts and reduces the stress on each of the glue lines in the stator assembly. The tangential forces on each of the posts may also be very high when under full power, but these forces are also balanced on each post so that the glue line is not always subjected to high stresses.

In this configuration it is desirable to use a "backiron" (which is not actually part of the flux path like a conventional single stator) with high thermal conductivity as well as high structural strength and stiffness. Aluminum will be an excellent choice in terms of high strength to weight and high thermal conductivity, but aluminum will also have high electrical conductivity, which will generate high eddy currents, especially at high operating speeds.

In order to utilize the structure and thermal gain of aluminum for the back irons, the slots in the disk for receiving the posts, and the ones that are radially outward or inward from the slots to remove the electrical conduction path around each of the posts A rotating actuator using a stack of two or more aluminum disks with the same additional slots is disclosed. Although a single piece of aluminum can be used with radial slots to prevent eddy currents, the present inventors have found that a laminated aluminum structure having alternating eddy current slots radially inwardly radially outwardly alternating from layer to layer, It is believed to provide a stronger and more rigid structure. This is because the eddy current slots on one layer are aligned with the non-slotted rings of the material on the next aluminum layer so that the two adjacent layers do not have aligned eddy current slots.

Aluminum in the back iron laminates can be coated, but they are preferably anodized with, for example, a hard anodized finish. Anodizing is essentially a ceramic coating that provides a high dielectric strength and a very good thermal conductivity.

The electric motor / actuator may be configured with a stator utilizing a ferromagnetic material laminate for the electromagnetic post to reduce eddy current losses. It is also preferred that a high thermal conductivity material is used within the stator structure to obtain heat from the device. The rotor can be made of a ferrous material that performs as required.

Reference numerals

20 Stator coil

22 Stator post laminate

24 Stator Non-Ferrous Structural Laminate (Stator Non-Ferrous Structural Laminate)

26 Stator back bone

28 Outer Rotor Housing

30 Rotor magnet

32 Thrust bearing

34 Ball Bearing

36 Stator post laminated assembly

38 "M" non-iron stator structure laminate

40 "W" non-iron stator structure laminate

42 Discontinuous Eddy Current Loop Path

44 Internal Stator Cooling Chamber

46 The radial cut-

48 Stator posts and structural laminate

50 Rotor side 1

52 Rotor side 2

54 Rotor stimulation

56 Structural laminate assembly

58 Air gap

60 slot

62 The ridge on the stator backbone

64 The channel around the interior of the stator structural member,

66 The distance between the structural members and between the posts

1, the electric machine includes a stator having a backbone 26 and a structural laminate assembly 56 disposed between the rotors 50, 52, and the rotors 50, And mounted on the bearings 32, 34 for rotation about a stator about an axis. The approximate location of the axis is identified by A in FIG. The rotors 50, 52 are separated from the stator by respective air gaps 58. 2, the stator structure laminate assembly 56 can include a structural member 24, each structural member having an annular laminate 38, 40, as shown in Fig. 2 And each laminate 38, 40 has a minimum dimension extending in the axial direction. Each structural member 24 and corresponding laminate has an opening or slot 60 and a magnetic post 36 (as shown in Figure 4) And is secured within the slot 60 for support. The slot 60 may have a longest dimension extending in the radial direction, a circumferentially extending intermediate dimension, and an axially extending depth. As shown in FIG. 2, one or more electrical conductors 20 are disposed about post 36 to create a series of rectified pre-excitation poles. There can be M stimuli and N posts, and the greatest common factor of N and M is 3 or more.

5, the backbone 26 includes an outer backbone 68 and an inner backbone 70, wherein the structural members 24 each have a ridge extending inwardly of the outer backbone and outwardly of the inner backbone, (62). ≪ / RTI > The structural member 24 may be secured to the ridge 62 by any suitable means, such as glue.

The rotors 50 and 52 are mirror images of each other and are fixed to each other by, for example, bolts or screws (not shown) at their outer periphery. 1, the rotors 50, 52 are mounted on a radial bearing 34 inside the stator for rotation about the stator and on thrust or axial bearings (not shown) on the outside of the stator (not shown). Bearing races are formed on the backbone 26 of the stator and in the rotors 50, 52. The stator backbone 26 may be secured to the fixed structure at the inner periphery of the backbone 26 by any suitable means. Then, the outward peripheral portion 28 of the rotor 50, 52 can be used as an output portion. Power for the windings 20 can be supplied through the inner portion of the backbone 26 through a channel (not shown). 2, the radial length of the stator posts 22 between the structural members 24 is less than the distance between the ridges 62 of the stator backbone 26, A channel 64 is formed around the stator. A channel (not shown) in the inner portion of the stator backbone 26 may be used to flow the cooling fluid into and out of the channel 64.

Exemplary embodiments may use an iron alloy for stator post lamination and an aluminum alloy for the structural laminate. The stator of the electric machine is formed of a structural laminate 24 having slots into which the posts 22 are secured. The structural laminate 24 has the thinnest dimension in the axial direction and is annular in the radial direction.

For the structural laminate 24, a radial section formed from the post slot to the edge of the material to remove the eddy current loop path 42 around the stator post, as shown in Fig. 6, It is preferable to have the joint 46. A slot may also be between the posts, e.g. between every second post in the circumferential direction. The preferred embodiment has radial cutouts opposite each other per layer as can be seen in Fig. 3, which may be referred to as "M" 38 and "W" 40 laminate. This is done to remove the eddy current loop path 42 on all layers of the structural laminate while still maintaining the proper strength and rigidity of the aluminum layer by an overlapping section on one or both sides of each slot for the other layer will be. In the embodiment shown in FIG. 2, it is shown that each laminated assembly 24 has five layers within it, and the number of layers is dominated by the design range. This in turn will create a thicker assembly with strength requirements and will reduce losses from eddy currents by an electrical insulator, such as an anodized surface, between the interrupted eddy current path and each layer on each layer.

A stator post laminate 36, which is preferably mounted vertically to the structural laminate 24, is then mounted between the two structural laminates to create a stator, which allows one embodiment to be used for tabs at the inner and outer radial positions Lt; RTI ID = 0.0 > mechanically < / RTI > Such an assembly may desirably be subject to interference and may be pressed together to produce a solid assembly 48, as can be seen in Fig. It may then be desirable to coat such sub-assemblies with a potting compound to add other materials to aid in obtaining heat from the stator posts to the structural laminate. The self-post may have an enlarged central section defining a respective shoulder forming a tab, each shoulder engaging the structural member to resist axial movement of the magnetic post within the structural member do. The posts and structural members together define a chamber 66.

In this preferred configuration, a post lamination 36 is used for the two stator posts and serves as a single magnetic dipole. This requires the rotor to have a magnet 30 on the side 52 to form a magnetic pole 54 rotated by one pitch with respect to the side 50. The North Pole is opposite the South Pole on the other side of the rotor, as can be seen in FIG. 7, so that axially opposing magnets have opposite polarities.

Chamber 66 and channel 64 together create a chamber 44 between the two structural laminates, as can be seen in Figures 2 and 9, which chamber is occupied by structural member 24 or post But may extend throughout the space between the stator backbone and the rotor. Such a chamber may be filled with a fluid or gas to remove heat from the stator and stator coils. This is desirable because the fluid or gas will come into direct contact with the center of the stator post and the structure laminated member to allow effective heat transfer. This may be desirable because it allows the device to operate at a higher current while maintaining a stable, desired temperature. It is preferred that the fluid or gas in such a chamber flow through the chamber due to the pressure differential between the inlet and outlet (which may be in the inner backbone, though not shown). The fluid or gas may also be kept stationary, or if air cooling is desired, ambient air may also flow through by natural convection.

To manufacture the device it may be necessary or helpful to insert a spacer between two laminated structural members when the post and aluminum disc are assembled. After the coil is then added and the stator is potted, the spacer prevents the potting compound from filling the space between the laminated aluminum disks. These spacers are preferably made of a soluble or fusible material, such as wax, which can be removed by melting or melting after the potting is complete.

In order to attach the laminated stator assembly to another entity, it may be required to insert a solid member between the laminates during the assembly process. This is illustrated in FIG. 5 where an exemplary member is inserted between the structure laminations. This exemplary element allows the bearings on the ID and OD to be used and allows for a bolt hole pattern on the ID flange 72 of the stator backbone 26.

Instead of the illustrated coil 20 just protruding from the structural member, a single set of coils can be used between the two structural members with shorter posts. This will not have a cooling gain, but it may be a lower profile assembly.

If the rotor is on each side of the stator, an equilibrated axial force is applied to the stator poles resulting from the fact that the rotor poles act on the both axial ends of each post with the same force. This tends to eliminate the shear force on the stator post laminate, which reduces deformation of the glue layer between the laminates. The mechanical fixation of the stator post laminate between the two aluminum layered discs (a wider section of the post is between the aluminum layer discs) resists migration of the laminate even when the glue is destroyed. This design reduces the eddy current in the laminate of the structural member due to the alternating ID-OD slots in each layer. Alternating ID to OD according to each successive layer provides a non-interrupted surface on at least one side of each eddy current prevention slot on the adjacent layer.

The use of aluminum for structural members results in lighter weight structures with excellent heat dissipation properties. Anodizing these layers prior to assembly provides electrical insulation with minimal thermal insulation between the layers. The space between the aluminum layer discs can also be used for internal fluid cooling.

Claims (22)

As an electric machine,
A stator disposed between the rotors is mounted on a bearing for rotation about a stator about the axis of the electric machine and the rotor has a respective air gap from the stator, Lt; / RTI >
The stator includes a structural member, wherein each structural member is formed of a laminate, each laminate having a minimum dimension extending in the axial direction;
Each structural member having a slot and a magnetic post, the magnetic post being secured within the slot for support of the magnetic post by the structural member; And
And at least one electrical conductor disposed about the post to produce a series of commutated electromagnetic poles. 2. The electrical machine of claim 1 wherein there are M stimuli and N posts and the greatest common factor of N and M is 3 or greater. 3. The electrical machine according to claim 1 or 2, wherein each post comprises an eddy current reduction feature comprising an electrically insulating laminate or powder. The electrical machine according to any one of the preceding claims, wherein each laminate of structural members comprises a barrier for the completion of a current circuit around the posts. 5. The electrical machine of claim 4, wherein each barrier comprises a slot in a corresponding laminate. 6. The electrical machine of claim 5, wherein the slots in adjacent laminates are located on opposite sides of the posts. 7. An electric machine according to any one of claims 1 to 6, wherein the post comprises a laminated ferrous material. 8. An electric machine according to any one of claims 1 to 7, wherein the post comprises an electrically insulated powdery material. 9. An electric machine according to any one of claims 1 to 8, further comprising a stator backbone to which the structural member is mounted. 10. The electrical machine of claim 9, wherein the structural member is spaced apart by a ridge on the stator backbone. 11. An electric machine according to claim 9 or 10, wherein the stator backbone comprises an inner portion and an outer portion. 12. An electric machine as in claim 11, wherein the bearing comprises an axial thrust bearing between a rotor and a portion of the outer side of the backbone between a rotor and an inner portion of the backbone. 13. The method of claim 10, 11, or 12, wherein the structural member forms a chamber between the structural member and the post, a channel extends around an inner portion of the backbone, Thereby forming a cooling chamber within the stator. 5. The electrical machine of claim 4, wherein the barrier to the current comprises a radial cut in each laminate formed from the post slot of the laminate to the adjacent edge. 15. The electrical machine of claim 14, wherein the radial cutouts alternate between opposite sides of the slots on adjacent laminates. 16. An electric machine according to claim 14 or 15, wherein the cutouts comprise blind slots. 17. An electric machine according to any one of the preceding claims, wherein the stator post is laminated. 18. The electrical machine of claim 17, wherein the stator post comprises a magnetic material. 19. The method of any one of claims 1 to 18, wherein the laminated posts extend axially outwardly on opposite sides of the structural member and pass through each of the structural members, each post forming a magnetic dipole , The magnets facing in the axial direction of the rotor have opposite polarities. 20. The electrical machine according to any one of the preceding claims, wherein the structural member comprises a non-magnetic material. 21. The electrical machine of claim 20, wherein the laminate of structural members comprises anodized aluminum. 22. A device according to any one of the preceding claims, wherein the magnetic post has an enlarged central section defining a respective shoulder, each shoulder engaging a structural member, An electric machine, which is resistant to axial movement of a magnetic post.

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