Improved Linear Actuator

Abstract

The present invention provides a permanent magnet assembly (300) for use in a non-commutated linear actuator (100), the permanent magnet assembly (300) including a magnetic core structure (350) and a permanent magnet (400) having a first magnetic pole and a second magnetic pole, the magnetic core structure (350) including a central core portion (360) connected to the first magnetic pole of the permanent magnet (400), an outer hollow portion (370) connected to the second magnetic pole of the permanent magnet (400), and a gap region (380) located between the central core portion (360) and the outer hollow portion (370), the magnetic core structure (350) being arranged such that magnetic flux generated by the permanent magnet (400) flows between the central core portion (360) and the outer hollow portion (370) through the gap region (380), and the magnetic core structure (350) includes one or more protrusions (361, 371) extending into the gap region.

Description

[Technical Field]

[0001] The present invention relates to uncommutated linear actuators, and more particularly to permanent magnet assemblies used in such motors. [Background technology]

[0002] Linear motors, such as uncommutated linear actuators, are also known. An uncommutated linear actuator (also known as a voice coil linear actuator, or, when a DC signal is applied, an uncommutated DC linear actuator) is a direct-drive linear actuator. It consists of a permanent magnetic field assembly and a coil assembly, arranged so that current flowing through the coil assembly interacts with the permanent magnetic field generated by the permanent magnetic field assembly to generate a force vector perpendicular to the direction of the current. This force "actuates" the linear actuator, allowing the coil assembly to move linearly along its longitudinal axis. Summary of the Invention [Problem to be solved by the invention]

[0003] Typical uncommutated linear actuators have several drawbacks. First, when the moving part within the actuator is at different positions along its length of travel, different forces are generated due to the interaction of the current flowing through the coil assembly with the permanent magnetic field. Compensating for these force differences and ensuring functional consistency throughout the linear movement process requires increased motor control complexity.

[0004] Additionally, because these devices rely on the alignment of a moving member that moves linearly relative to a fixed member, alignment of the moving and fixed members is critical to achieving the desired force. However, typical non-commutated linear actuators offer inadequate protection against external forces, such as mechanical shock, which can cause misalignment between the fixed and moving members. Finally, when the coil assembly of a non-commutated linear actuator is part of the actuator's moving member, additional issues arise related to the reliability of the electrical connection to the coil assembly. For example, if wires are used to connect to the coil assembly, the constant movement of the moving member can rapidly wear the wires, potentially leading to motor failure.

[0005] Furthermore, under high load conditions (i.e., when a large amount of current is present in the coil assembly), typical non-commutated linear actuators experience problems such as significant distortion and displacement of the magnetic flux lines in the air gap. These distortions and displacements result in poor motor control linearity, reduced available force applied to the coil, poor armature frequency response, poor armature position repeatability, and poor compliance (i.e., the extent to which the armature moves proportionally to input power without bouncing).

[0006] It would therefore be desirable to provide an arrangement to overcome or at least mitigate the problems of conventional linear actuators. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided a permanent magnet assembly for use in a non-commutated linear actuator, the permanent magnet assembly including a magnetic core structure and a permanent magnet having a first magnetic pole and a second magnetic pole, the magnetic core structure including a central core portion connected to the first magnetic pole of the permanent magnet, an outer hollow portion connected to the second magnetic pole of the permanent magnet, and a gap region located between the central core portion and the outer hollow portion, the magnetic core structure being arranged such that magnetic flux generated by the permanent magnet flows between the central core portion and the outer hollow portion through the gap region, and the magnetic core structure including one or more protrusions extending into the gap region.

[0008] A magnetic core structure may refer to a mechanical structure having high magnetic permeability (i.e., the internal dipoles of the structural material are easily oriented in response to an applied magnetic field), thereby confining and guiding a magnetic field. In this case, the magnetic core structure is positioned to contain and guide the magnetic field generated by a permanent magnet. A gap region may refer to one or more air gaps that exist between a cylindrical outer hollow portion and a central core portion.

[0009] The terms "central core" and "outer hollow" refer to the relative arrangement of these features. That is, the outer portion of the magnetic core structure may completely surround and be concentric with the central core. Alternatively, the outer hollow may include two arms, one of which covers the top of the central core and the other of which covers the bottom of the central core. The central core may have an approximately circular, oval, square, rectangular, etc. cross-section. The outer hollow may similarly have an approximately circular, oval, square, rectangular, etc. cross-section, but lacking material in its center (hence the structure is hollow). However, the central core and outer hollow are not required to have similar cross-sectional shapes. Nevertheless, in some embodiments, the outer hollow and central core have similar cross-sectional shapes (i.e., both may have approximately circular cross-sections, or each may have an overall cylindrical shape). For the avoidance of doubt, "outer hollow portion" may refer to the same feature as "outer pole piece" and "central core portion" may refer to the same feature as "inner pole piece".

[0010] It may be further understood that the outer layer hollow portion may be concentric with the central core portion, such that the two may share a center point in cross section. It may be further understood that the length of the outer layer hollow portion (defined by a line along the surface of the outer layer hollow portion from the proximal end of the permanent magnet assembly to the distal end of the permanent magnet assembly) is essentially parallel to the corresponding length of the central core portion.

[0011] The terms distal and proximal are used to define the endpoints of the permanent magnet assembly. It can be understood that the central core and the outer hollow portion extend between their respective proximal and distal ends. It can further be understood that the end of the permanent magnet assembly at which the permanent magnet is located may be considered the proximal end.

[0012] It may be further understood that the permanent magnet assembly is designed to define a channel between the movable members (also referred to as members that are capable of linear movement in a longitudinal direction) of the non-commutated linear actuator, and that the channel may include a gap region.

[0013] For ease of understanding, protrusions may refer to features of the magnetic core structure that protrude or extend from a surface of the magnetic core structure, where one or more protrusions are positioned to extend into the gap region, thereby reducing the distance between the outer layer hollow portion and the central core portion at least at the location of the one or more protrusions.

[0014] It may further be understood that the protrusions are three-dimensional structures and thus may extend a fixed distance from the entire surface (e.g., a trumpet-shaped annular disk extending outward from a cylindrical central core), or may be provided with several dispersed, fixed protrusions that do not necessarily extend around the core or outer periphery.

[0015] One advantage of the above arrangement is that the one or more protrusions are used to shorten the distance between the outer hollow portion and the central core, thereby strengthening the magnetic field present in the air gap, compared to a comparable arrangement without the protrusions. This is advantageous because the higher the magnetic field density (i.e., magnetic flux) in the gap region, the greater the force that can be transferred to the conductive element (e.g., the winding coil of a non-commutated linear actuator) present in the gap region. This effect can occur without having to increase the strength and size of the permanent magnet, further improving the cost-effectiveness and size of such permanent magnet assemblies.

[0016] Another benefit is that these protrusions reduce the distortion of the magnetic flux lines in the air gap that occurs when high currents flow through the coil. Less distortion or displacement of the magnetic flux in the air gap is advantageous because it improves the linearity of the control (and therefore the relationship between input power and armature position).

[0017] Also, by reducing the distortion and displacement of the magnetic flux lines, a higher magnetic flux density passes through the coil in a direction perpendicular to the current in the coil, thereby increasing the available force applied to the coil, which again improves the frequency response of the armature and ensures greater repeatability of the armature position.

[0018] Finally, reducing the distortion and displacement of the magnetic flux lines in the air gap improves the compliance of the linear actuator (i.e., the degree to which the armature moves proportionally to the input power without bouncing).

[0019] In some embodiments, the one or more protrusions of the magnetic core structure include one or more core portion protrusions that extend radially outward from the central core portion into the gap region.

[0020] In some embodiments, the one or more protrusions of the magnetic core structure include one or more hollow portion protrusions that extend radially inward from the outer hollow portion into the gap region.

[0021] The one or more core projections may be understood to be features that are integral with or attached to the central core, and the one or more hollow projections may further be understood to be integral with or attached to the outer hollow.

[0022] One advantage of having protrusions only on the central core or the outer hollow section is that the same benefit of increased magnetic flux can be achieved without increasing cost and manufacturing complexity. For example, compared to having protrusions on both the central core and the outer hollow section (each requiring a different process), protrusions can be implemented only on the outer hollow section, simplifying the central core design (and vice versa).

[0023] In some embodiments, at least one core projection of the one or more core projections corresponds to and aligns with a corresponding hollow projection of the one or more hollow projections.

[0024] It may be understood that when a core portion protrusion "corresponds to and aligns with a corresponding hollow portion protrusion," it refers to an arrangement in which the core portion protrusion is located at a specific position along the length of the core portion and the corresponding hollow portion protrusion is located at a similar position along the length of the hollow portion. In other words, it may be understood that the two protrusions extend toward each other, further shortening the distance between the core portion and the outer hollow portion compared to a single protrusion of the same size.

[0025] This arrangement is particularly advantageous when it is desired to optimize the magnetic flux present in the air gap while keeping the length of each of the protrusions to a minimum. In other words, having an equally shortened air gap (with corresponding protrusions on both sides) means that each corresponding protrusion forming the air gap is smaller than a corresponding arrangement with a single long protrusion (extending from either the central core or the outer hollow portion). This makes the permanent magnet assembly more robust (the shorter protrusions are less likely to break) and significantly improves the magnetic flux density compared to an arrangement without protrusions.

[0026] In some embodiments, the central core has an axial cross-section that is approximately circular, approximately oval, or approximately square.

[0027] In some embodiments, the hollow portion has an axial cross-section that is approximately circular, approximately oval, or approximately square, and the outer hollow portion includes at least one elongated slot along its length to allow access to the gap region.

[0028] The at least one elongated slot can be understood to be a gap that projects through the entire thickness of the hollow portion. Such slot is designed to allow electronic commutation of components that may be present in the gap region. This allows, for example, the transmission of power to a winding coil present in the gap region to form a non-commutated linear actuator.

[0029] As previously mentioned, the central core and hollow portion can each have different shapes, which will ultimately be determined by the shape of the linear actuator that the permanent magnet assembly is part of. For example, if the moving member of the linear actuator is a hollow cylinder, it would be advantageous for both the central core and the outer hollow portion to have an approximately circular axial cross section to provide an annular gap region in which the moving member fits.

[0030] One advantage of designing the permanent magnet assembly in this manner (i.e., with elongated slots in the outer hollow section) is that the magnetic flux is transmitted along the length of the permanent magnet assembly except for the elongated slots, thereby maximizing the magnetic flux generated between the outer hollow section and the core.

[0031] In some embodiments, the one or more core projections have an axial cross-section that is approximately circular, approximately oval, or approximately square.

[0032] In some embodiments, the one or more hollow projections have an axial cross-section that is approximately circular, approximately oval, or approximately square, and the hollow projections include at least one elongated slot along their length to allow entry into the gap region.

[0033] As mentioned above, protrusions are three-dimensional structures. As such, they can extend a certain distance from the entire surface (e.g., a trumpet-shaped annular disk extending outward from a cylindrical core). The above configuration defines that a protrusion can have an approximately circular, oval, or square cross-section. This may refer to the cross-section defined by the outermost or innermost edge of the protrusion. For example, if there is a cylindrical core and an annular disk extending outward from a point along the length of the core, the protrusion of the annular disk is considered to have an approximately circular cross-section. This is because the outermost edge of the annular disk is circular.

[0034] In this case, the axial cross section of the protrusion may refer to the cross section of the protrusion and the central core itself. For example, a protrusion extending a certain length from a cylindrical core would be considered to have a circular cross section.

[0035] Alternatively, the axial cross section of a protrusion may refer to the cross section of the protrusion only (when there is no core). As such, the cross section of such a core protrusion may also be considered to be annular (not circular).

[0036] It can be seen that the elongated slots in the hollow portion projections align with the corresponding elongated slots in the hollow portion, since there is no magnetically permeable material in the elongated slots in the hollow portion, so nothing protrudes from this feature.

[0037] In some embodiments, the one or more core projections include a plurality of core projections, and / or the one or more hollow projections include a plurality of hollow projections.

[0038] One advantage of multiple core projections and / or hollow projections is that they can distribute regions of increased magnetic flux along the length of the permanent magnet assembly. For example, if a first core projection is located at a first position along the length of the magnetic core structure and a second core projection is located at a second position along the length of the magnetic core structure (the second position being distal or proximal to the first position), at least two distinct regions of increased magnetic flux are provided within the gap region. The distribution of these projections (and the resulting regions of increased magnetic flux) improves the operation of non-commutated linear actuators that implement such permanent magnet assemblies because the movable member of the linear actuator experiences a more uniform magnetic flux along the movable length of the movable member.

[0039] In some embodiments, each of the plurality of core portion projections is spaced a second distance from an adjacent core portion projection, and each of the plurality of hollow portion projections is spaced a second distance from an adjacent hollow portion projection.

[0040] It is advantageous for the core projections, and similarly for the hollow projections, to be spaced apart from one another by a fixed distance, as this further ensures that the moving member of the non-commutated linear actuator is subjected to a uniform force along the length of travel of the moving member.

[0041] In some embodiments, the second distance may be less than the length of the associated moving member of the non-commutated linear actuator, such that there is no position along the length of travel of the moving member where the moving member is not within the increased flux region (defined by the aforementioned protrusion).

[0042] In some embodiments, the permanent magnet assembly further includes a filler material positioned to cover the sides of the one or more protrusions.

[0043] The "side" of a protrusion may be understood to refer to an edge or region that essentially faces proximally or distally (i.e., faces proximally or distally of the magnetic core structure). When multiple protrusions are present in the same portion of the magnetic core structure (e.g., core portion), the "sides" of two protrusions are the portions that face each other. In other words, the side is the portion of each protrusion that does not form the base of the protrusion or face the associated gap region.

[0044] "Covering" can refer to a feature that completely covers the side of the protrusion, or it can cover only a selected portion of the side of the protrusion.

[0045] The advantage of introducing a material to cover the sides of the protrusions is that it prevents the protrusions from having sharp edges, which are undesirable, especially when the movable member is moving within the gap region. By providing a filler material, the sharp corners associated with the protrusions can be rounded. As a result, when a non-commutated linear actuator having such a permanent magnet is subjected to an external force (e.g., being dropped or impacted by the linear actuator's chassis), the movable member of the linear actuator will not collide with sharp corners during its operation. In other words, the permanent magnet assembly of this embodiment provides all the benefits associated with increasing magnetic flux at specific points along the magnetic core structure, but without compromising the structural resilience of the associated linear actuator.

[0046] In some embodiments, a filler material is disposed to completely fill spaces between adjacent core projections of the plurality of core projections, and a filler material is disposed to completely fill spaces between adjacent outer hollow projections of the plurality of hollow projections.

[0047] "Adjacent" may be understood to refer to two protrusions that are close to each other, with no intervening protrusions. Thus, when the filler material completely fills the space between them, each side of the adjacent protrusions is completely covered. Furthermore, completely filling the space between the protrusions means that the channel through which the movable member of the linear actuator moves is uniform throughout the entire length of the permanent magnet assembly. Thus, the channel is defined only by the gap between the axial cross section of the core portion protrusion (which would be the surface of the core portion if not present) and the axial cross section of the hollow portion protrusion (which would be the surface of the outer hollow portion if not present).

[0048] The benefit of a uniform profile in the channel / gap region is that it provides improved structural integrity. Additionally, as mentioned above, small edges along the length of the permanent magnet assembly are beneficial for impact resistance, as the moving member is not easily damaged when it comes into contact with a flat surface. It also aids in the return of the moving member to its original position, as the uniform channel formed by the filler material limits the allowable movement of the moving member, thereby preventing it from jamming.

[0049] In some embodiments, the filler comprises a resin.

[0050] The filler material may be any material that is relatively magnetically impermeable compared to the magnetic permeability of the core, hollow portions, and such protrusions. This means that the filler material has little effect on the magnetic field provided within and directed through the magnetic core structure. It is also advantageous to provide a material with a low coefficient of friction so as not to adversely affect moving parts present within channels at least partially formed by the filler material.

[0051] According to the present invention, there is also provided a non-commutated linear actuator having a fixed member and a movable member, the movable member arranged for longitudinal movement relative to the fixed member, the fixed member including a permanent magnet assembly according to any of the above embodiments, and the movable member being arranged within an air gap region of the permanent magnet assembly.

[0052] A non-commutated linear actuator, also known as a voice coil linear actuator (or a non-commutated DC linear actuator when a DC signal is applied), may further be understood to be a direct drive linear actuator. It consists of a permanent magnet assembly and a moving member, arranged to generate a force vector perpendicular to the direction of electric current by interacting with the permanent magnetic field generated by the permanent magnet assembly.

[0053] It may be understood that the movable member is also referred to herein as a member that is linearly movable in the longitudinal direction.

[0054] In some embodiments, the movable member includes at least one conductive winding.

[0055] It can be seen that the movable member is provided with conductive windings so that current is driven along the path of the windings, and the current flowing through the coil assembly interacts with the permanent magnet assembly.

[0056] In some embodiments, the movable member includes a structure including at least one of carbon fiber, thermoplastic, thermoset plastic, or synthetic fiber material, and the at least one conductive winding is wound around the structure.

[0057] The tube can be made from a number of insulating materials, including, for example, carbon fiber, PEEK, PEKK, or other types of insulating polymers, or it can be made from a synthetic fiber material such as Kevlar.

[0058] Wrapping at least one conductive winding around the structure increases the current density around the circumference of the structure, resulting in a stronger interaction between the input current and the magnetic flux generated by the permanent magnet assembly.

[0059] In some embodiments, the structure is tubular to fit within a cylindrical linear actuator, however, the structure can adopt any suitable shape (e.g., a hollow rectangular prism) to fit the profile of a particular linear actuator.

[0060] In some embodiments, the uncommutated linear actuator further includes an electrical interface positioned to connect the at least one conductive winding to a power source through the at least one elongated slot.

[0061] The electrical interface of the present invention may be any connection (eg, a direct wire connection) to at least one conductive winding.

[0062] In some embodiments, the electrical interface includes at least one flexible conductive band positioned to transfer electrical power from the power source to at least one conductive winding on the movable member.

[0063] A "flexible conductive band" may refer to a strip or loop of material. The conductive band itself may be at least partially formed from a conductive material, or there may be a conductive element on, around, or connected to a non-conductive substrate of the conductive band. "Flexible" may further be understood to refer to the ability of the conductive band to bend or deform without breaking.

[0064] In some embodiments, the flexible conductive band is a resilient element that can be deformed (e.g., compressed) from a rest state to an assembled state when disposed between the first and second conductive surfaces. In such an assembled state, the flexible conductive band can be subjected to a mechanical strain that returns the flexible conductive band to its rest state. This characteristic improves the electrical connection between the first and second conductive portions by maximizing the surface area of ​​electrical contact.

[0065] In some embodiments, at least one flexible conductive band is arranged to mechanically interact with a first contact region and to mechanically interact with a second contact region, where the first region is a conductive strip on the movable member and the second region is a conductive strip coupled to a chassis of the uncommutated linear actuator, such that when the second portion is moved relative to the first portion, the flexible conductive band moves along a predetermined path and maintains electrical connection between the first contact region and the second contact region.

[0066] In some embodiments, the at least one flexible conductive band is arranged to undergo a rolling motion as the movable member of the linear actuator is translated to move along the predetermined path.

[0067] In such an embodiment, the at least one flexible conductive band is positioned to transmit power to at least one conductive winding on the longitudinally translatable member or movable member.

[0068] Such an arrangement can replace wired connections to longitudinally movable members or conductive windings on the moving member. These wires are subject to significant stress during repeated operation of the linear motor. The linear electric motor of the present invention is therefore advantageous in that wear on the members is reduced, extending the life of the motor itself. [Brief explanation of the drawings]

[0069] Advantageous embodiments of the invention will now be described with reference to the accompanying drawings, in which: [Figure 1] 1A and 1B are an exemplary linear actuator having a smooth surface on the permanent magnet assembly. [Figure 2] FIG. 2 is an isometric view of a cylindrical linear actuator according to one embodiment of the present invention. [Figure 3] FIG. 3 is an exploded view of the cylindrical linear actuator shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the cylindrical linear actuator shown in FIG. [Figure 5] FIG. 5 is a cross-sectional 2D view of a permanent magnet assembly according to one embodiment of the present invention, illustrating the magnetic flux present within the permanent magnet assembly. [Figure 6] 6A and 6B are 3D views of an outer hollow section used with a permanent magnet assembly according to one embodiment of the present invention. [Figure 7] FIG. 7 is a 3D view of a permanent magnet assembly installed in a linear actuator according to one embodiment of the present invention. [Figure 8] FIG. 8 is an isometric view of a rectangular linear actuator according to one embodiment of the present invention. [Figure 9]9 and 9A show a cross-sectional view of the rectangular linear actuator of FIG. 8, as well as a sub-cross-sectional view with magnetic flux lines indicated. [Figure 10] FIG. 10 is a diagram of an exemplary flexible conductive band for use in a linear actuator in accordance with one embodiment of the present invention. [Figure 11] FIG. 11 is another view of the flexible conductive band shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0070] In the following description, the terms "primary," "secondary," "primary," and "secondary" are not intended to be limiting, but rather are used to distinguish different elements from one another. The longitudinal axis of a linear actuator can be thought of as the axis extending in a direction between the proximal end (i.e., the power input side) and the distal end of the electric motor. In other words, this longitudinal axis follows the direction of movement of the motor.

[0071] Figures 1A and 1B illustrate this phenomenon for a length of cylindrical linear actuator that includes a permanent magnet assembly with an inner pole piece and an outer pole piece. As can be seen in Figure 1A, magnetic flux lines (dashed lines) emerge from the permanent magnet, cross the air gap from the outer pole piece of the permanent magnet assembly, enter the inner pole piece of the permanent magnet assembly, and close the magnetic circuit at the other end of the permanent magnet. In this case, the surfaces of both the outer pole piece and the inner pole piece in the area of ​​the air gap are smooth, with no protruding features protruding into the air gap. The magnetic field passing through the air gap is arranged to interact with the current flowing in the coil layer (which resides within the air gap) to generate a linear force in the coil layer.

[0072] 1B shows the magnetic flux lines of the linear actuator of FIG. 1A under high load conditions (i.e., when high current is flowing through the coils of the coil layer). In this case, the magnetic flux lines (also shown as dashed lines) are distorted and shifted within the air gaps that intersect with the coils of the coil layer. In the illustrated example, the magnetic flux lines shift backward, but it can be seen that if the polarity of the current in the coils is reversed, the magnetic flux lines shift forward.

[0073] This phenomenon is equivalent to a linear actuator's reaction to the armature of a DC rotating machine that has permanent magnets or electromagnets to generate the magnetic flux: in a rotating machine, the geometric magnetic neutral axis (GMNA) is subjected to a secondary magnetic field generated by the armature (armature flux), and these two fields interact (determined by the electrical neutral axis ENA), producing a rotational torque when the angle between them is less than 90 degrees.

[0074] As previously mentioned, the actuator of Figures 1A and 1B has a permanent magnet assembly in which both the inner and outer pole pieces are substantially smooth along the surface of the air gap region.

[0075] 1A and 1B have significant problems related to motor control. Specifically, distorted magnetic flux lines in the air gap are disadvantageous because they result in less linear control, reduced available force applied to the coil, poor armature frequency response, poor armature position repeatability, and poor compliance (i.e., the degree to which the armature moves proportionally to input power without bouncing).

[0076] A first embodiment of a cylindrical linear actuator 100 is shown in Figures 2 through 4. Figure 2 shows an isometric view of the assembled linear actuator 100, Figure 3 shows an exploded view of the linear actuator 100, and Figure 4 shows a cross-sectional view of the linear actuator 100 showing further details of the internal components.

[0077] Cylindrical linear actuator 100 includes a fixed member 105 and a movable member 110. During operation, power (e.g., electrical current) is transmitted from fixed member 105 to movable member 110. In the illustrated embodiment, the current flows through the surface of movable member 110 and interacts with a permanent magnetic field present within linear actuator 100 to generate a force vector. As such, the linear actuator can be considered a type of uncommutated linear actuator (also commonly referred to as a "voice coil" motor).

[0078] Such linear actuators can be operated bidirectionally by adjusting the polarity of the input voltage / current applied to the input terminals of the linear actuator.

[0079] Such a linear actuator 100 requires that current be present in the movable mass 110, and therefore there is a mechanism for transmitting the input voltage / current from the input terminals of the linear actuator 100 to the movable mass 110. This can be accomplished using any number of interface elements, as will be appreciated by those skilled in the art.

[0080] In one embodiment of the present invention, the electrical interface of the linear actuator 100 (i.e., the electrical interface between the fixed member and the moving member) is provided via one or more flexible conductive bands 150. The one or more flexible conductive bands 150 are positioned to transmit electrical current from the fixed power rail 107 (a power rail fixed to the fixed member 105 of the linear actuator 100) to the moving power rail 112 (a power rail fixedly attached to the moving member 110 of the linear actuator 100).

[0081] There may be a first electrical interface formed by a first set of flexible conductive bands, a first fixed power rail 107a, and a first movable power rail 112a. The first set of flexible conductive bands is arranged to transmit a first electrical signal between the first fixed power rail 107a and the first movable power rail 112a. There may be multiple flexible conductive bands 150 to ensure adequate power is transferred to the movable member 110 and to transfer current to the movable member 110 more evenly throughout the length of the movable member 110.

[0082] There may also be a second electrical interface formed by a second set of flexible conductive bands, a second fixed power rail 107b, and a second movable power rail 112b. The second set of flexible conductive bands 150 is arranged to transmit a second electrical signal between the second fixed power rail 107b and the second movable power rail 112b. There may also be multiple flexible conductive bands 150 to more evenly distribute current to the movable member 110 throughout the length of the movable member 110 so that adequate power is delivered to the movable member 110.

[0083] In such a case, the first and second electrical interfaces are provided to transmit bipolar electrical signals to the movable member 110. That is, the second electrical interface serves as a return path for the signal provided via the first electrical interface. In other words, when a power source is connected to the two input terminals of the linear actuator 100, current flows from the power source through the first electrical interface, around the surface of the movable member 110, and out through the second electrical interface and back to the power source.

[0084] In some embodiments, the movable member 110 may have at least one conductive winding (not shown) wound around the structure of the movable member 110. The act of winding a conductive winding around the movable member 110 means that greater forces can be generated by the linear actuator without increasing the voltage of the power supply. As previously mentioned, current flowing through the coil assembly interacts with the permanent magnetic field generated by the permanent magnet assembly, generating a force vector perpendicular to the direction of the current.

[0085] The additional loops in the conductive winding increase the current density around the movable mass 110, thereby increasing the force experienced by the linear actuator 100 due to interaction with the permanent magnetic field. Nevertheless, the linear actuator 100 can operate even when multiple loops are not present and the current flows around the surface of the movable mass 110.

[0086] 3, the first and second electrical interfaces may be located on opposite sides of the linear actuator 100. However, other arrangements are possible (including, for example, the first and second electrical interfaces being adjacent to the same side of the linear actuator 100).

[0087] One or more flexible conductive bands 150 provide a low-friction electrical interface between the fixed and moving members within the linear actuator 100. As the moving member 110 moves along the longitudinal axis, the one or more flexible conductive bands 150 are arranged to roll in the same direction as the moving member 110. This type of interface provides a lower friction interface than a corresponding static interface and is less prone to wear than electrical interfaces that utilize brushes or direct wiring configurations.

[0088] Such an electrical interface can therefore be considered an improved electrical commutation assembly that offers high current carrying capacity, high wear resistance, and low friction, all of which make the electrical interface particularly advantageous for transmitting electrical signals to an electric motor assembly.

[0089] As previously mentioned, the cylindrical linear actuator 100 according to one embodiment of the present invention includes a permanent magnet assembly 300 for generating a constant permanent magnetic field.

[0090] The permanent magnetic field is generated by a permanent magnet assembly 300 located within the chassis 106 of the fixed member 105. For the avoidance of doubt, the permanent magnet assembly 300 is not visible in Figures 2 and 3 but is visible in the cross-sectional view of Figure 4.

[0091] 4 and 5, the permanent magnet assembly 300 includes a permanent magnet 400 having a first magnetic pole (eg, a north pole) and a second magnetic pole (eg, a south pole), and a magnetic core structure 350.

[0092] In some embodiments, the magnetic core structure 350 is made from a material with high magnetic permeability so that it can contain and guide the magnetic field generated by the permanent magnet 400. In some embodiments, the magnetic core structure 350 may include a ferromagnetic material such as iron, other ferromagnetic compounds, or silicon. The core structure may or may not be laminated.

[0093] The magnetic core structure 350 includes two sections: a central core section 360 and an outer hollow section 370. In the cylindrical embodiment of the linear actuator 100 shown in Figure 4, the outer hollow section 370 has an approximately ring-shaped cross section, and the central core section 360 has an approximately circular cross section.

[0094] The cross section of the outer hollow portion 370 has at least one elongated slot 375 along a portion of the length of the permanent magnet assembly 300 to accommodate an electrical interface.

[0095] As best seen in the embodiment of Figure 2, there may be two elongated slots 375 aligned with the two electrical interfaces. As a result, the cross section of the outer hollow portion 370 in Figure 2 is generally ring-shaped, with material removed on a first side of the ring and a second, opposite side of the ring. The removal of material creates the elongated slots 375 in the outer hollow portion 370, which allow for the transfer of power to the moveable member 110 generally disposed within the outer hollow portion 370.

[0096] The central core portion 360 is coupled to a first pole of the permanent magnet 400 , and the outer hollow portion 370 is coupled to a second pole of the permanent magnet 400 .

[0097] 5, the central core portion 360 is separated from the outer hollow portion 370 by a gap region 380. The gap region 380 is wide enough so that at least a portion of the movable member 110 of the linear actuator 100 fits within the gap region 380 when the permanent magnet assembly 300 is attached to the linear actuator 100.

[0098] In other words, it can be seen that this gap region 380 defines a channel along the length of the permanent magnet assembly (and thereby along the length of the associated linear actuator), and the movable member is arranged to move within this channel.

[0099] 5, the magnetic field travels through the magnetic core structure 350 from the north pole of the permanent magnet 400 to the south pole of the permanent magnet 400. The magnetic field travels between the central core portion 360 and the outer hollow portion 370 through the gap region 380.

[0100] The protrusions essentially prevent shifts of the magnetic flux lines along the length of the hollow outer and central core sections (such as those seen in Figures 1A and 1B), although they may cause slight local distortion of the magnetic flux lines in response to high current conditions in the coil.

[0101] In another example, the permanent magnets 400 can be connected in the opposite direction (i.e., north pole connected to the outer hollow portion 370 and south pole connected to the central core portion 360). While this arrangement does not affect the operation of the linear actuator 100, the polarity of the power supply must be reversed to achieve equivalent control, since applying the same voltage to the linear actuator 100 will cause the movable member 110 to move in either a distal or proximal direction depending on the orientation of the magnets.

[0102] The permanent magnet 400 may be any type of Alnico (AlNiCo), ferrite, samarium cobalt (SmCo), flexible rubber, or neodymium magnet (also known as neodymium iron boron magnet (NdFeB)). In some embodiments, the permanent magnet may be a neodymium iron boron (NdFeB) permanent magnet, which may have an axial magnetization.

[0103] In some embodiments, the permanent magnet may be cylindrical with a width of about 5-40 mm (preferably 15 mm) and a diameter of about 20-40 mm (preferably 31.5 mm).

[0104] In some embodiments, the magnetic flux density at the surface of the permanent magnet 400 may be about 0.1 to 2 Tesla (preferably 1.7 Tesla).

[0105] In the embodiment shown in FIG. 4, the movable member 110 has the shape of a hollow tube, enclosing a central core portion 360 (which is generally cylindrical) and surrounded by an outer hollow portion 370 (which is also generally hollow cylindrical).

[0106] To further improve the performance of the linear actuator 100, the magnetic core structure 350 may include one or more protrusions 361, 371 that extend into the gap region 380. These protrusions 361, 371 reduce the distance between the central core portion 360 and the outer hollow portion 370, thereby increasing the magnetic flux density within the gap.

[0107] In the embodiment shown in FIGS. 4 and 5, there are a plurality of protrusions 361 along the length of the central core portion 360 and a corresponding plurality of protrusions along the length of the outer hollow portion 371.

[0108] 5, the majority of the magnetic flux in the gap region 380 resides between the corresponding tooth-like projections 361, 371. In this embodiment, such projections 361, 371 provide regions of increased magnetic flux at regular intervals along the length of the permanent magnet assembly 300.

[0109] In the cylindrical linear actuator 100 of Figure 4, it can be seen that each protrusion 361 extends along the circumference of the central core portion 360. In other words, each protrusion 361 extending from the central core portion 360 (i.e., core portion protrusion) has a generally ring-shaped cross-section (or the cross-section of the protrusion and the underlying central core portion 360 is circular). Corresponding protrusions 371 extending from the outer hollow portion 370 (i.e., hollow portion protrusions) also each have a generally ring-shaped cross-section. More specifically, one embodiment of the outer hollow portion 370 is shown in Figures 6A and 6B.

[0110] In the embodiment of Figure 4, there are cavities between each adjacent core projection 361, and similar cavities between each adjacent hollow projection 371. These cavities are best seen in the cross section shown in Figure 5.

[0111] In some embodiments, the width of the denticles may be about 1-10 mm (preferably 2 mm).

[0112] In some embodiments, each of these cavities is filled with a filler material 365, which may be a resin, as shown in Figure 4. In Figure 4, the cavities are completely filled, resulting in a gap region of uniform width along the entire length of the permanent magnet assembly (and therefore no corners in the channel of the moving member of the associated linear actuator).

[0113] As previously mentioned, having a uniform profile for the channel / gap region 380 is beneficial for preventing sharp edges that may interfere with the movable member 110 of the linear actuator 100. This is particularly beneficial for improving impact resistance, as the movable member 110 is not easily damaged when in contact with a flat surface, and also aids in returning the movable member 110 to alignment, as the uniform channel formed by the filler material 365 limits the allowable travel of the movable member 110, thereby preventing the movable member 110 from jamming.

[0114] 2-4 and 7, in some embodiments, a guide rail 115 is attached to the inner surface of the movable member 110. In some embodiments, multiple guide rails 115 may be attached, for example, one rail on each side of the movable member 110.

[0115] 2-4, a first guide rail 115a is mounted on one side of the interior of the movable member 110, and a second guide rail 115b is mounted on the opposite side of the interior of the movable member 110. In this embodiment, the guide rails are aligned with elongated slots 375 in the outer hollow portion 370 (to minimize loss of magnetic flux along the length of the movable member 110), although this is not strictly necessary. If guide rails are present, the central core portion 360 has one or more cutouts to accommodate the guide rails 115.

[0116] The purpose of the guide rails 115 is to improve the sliding mechanism of the linear actuator 100. In some embodiments, the guide rails 115 slide on ball bearings or rollers 390. Such rollers 390 can be made of a low-friction material (e.g., PEEK) and are shown in FIG.

[0117] Figure 7 shows another isometric view of the cylindrical linear actuator 100 of Figures 2-4. In this view, the electrical interface has been hidden and the view has been rotated to highlight the inner guide rails 115 of the movable member 110 and the corresponding cutouts in the central core portion 360 of the permanent magnet assembly 300.

[0118] 8 is an isometric view of a rectangular linear actuator 120 according to another embodiment of the present invention. The rectangular linear actuator 120 includes a fixed member 125, a movable member 130, and a permanent magnet assembly 310. The rectangular linear actuator 120 operates in much the same manner as a cylindrical linear actuator, except for the shape of the movable member 125 and the shape of the permanent magnet assembly 310 (which is similar to permanent magnet assembly 300). That is, the rectangular linear actuator 120 relies on the same principles of interaction between current flowing in the movable member 130 and a permanent magnetic field, and the principles described above also apply to rectangular embodiments.

[0119] As shown in Figure 8, the movable member 125 of the rectangular linear actuator 120 has the shape of a hollow rectangular parallelepiped. In the illustrated embodiment, the upper surface of the hollow rectangular parallelepiped is disposed within a first channel, which is formed as a gap between a central core portion of the permanent magnet assembly and a first arm of the outer hollow portion. The lower surface of the hollow rectangular parallelepiped is disposed within a second channel, which is formed as a gap between a central core portion of the permanent magnet assembly and a second arm of the outer hollow portion.

[0120] In this way, current flowing on either the top or bottom surface of the movable member is arranged to interact with the permanent magnetic field present in the channel (i.e., the gap region formed by the permanent magnet assembly). In other words, there is a conductive path on at least one of the surfaces of the rectangular parallelepiped.

[0121] The conductive path may be formed by at least one conductive winding wound around the surface of the movable member.

[0122] Although not shown in FIG. 8, the rectangular linear actuator 120 may further have one or more electrical interfaces for supplying current to the movable member, which may include one or more flexible conductive bands 150 (similar to the flexible conductive bands of the cylindrical linear actuator).

[0123] The electrical interface between the fixed member 125 and the movable member 130 may be the same as the electrical interface of a cylindrical linear actuator.

[0124] In operation, power (e.g., electrical current) is transferred from the fixed member 125 to the movable member 130. As in the cylindrical case, there is a permanent magnet assembly that provides a magnetic field within the gap region 385 and interacts with the electrical current on the movable member.

[0125] In the embodiment shown in Figure 8, the permanent magnet assembly of the rectangular linear actuator 120 includes multiple protrusions 362, 372 on both the core portion (core portion protrusions 362) and the outer hollow portion (outer hollow portion protrusions 372). It is also possible for the protrusions 362, 372 to be present on only one of the core portion or the outer hollow portion. These protrusions serve the same purpose as the protrusions on a cylindrical linear actuator, so the principles described above apply here as well.

[0126] In certain embodiments, the cavities or spaces between adjacent protrusions 362, 372 of the core and outer hollow portion are at least partially filled with a filler material 365 (e.g., resin). The filler material 365 may be the same as the filler material of the cylindrical linear actuator embodiment. In the embodiment shown in FIG. 8, the spaces between adjacent protrusions are completely filled, forming a smooth channel for the movable member 130.

[0127] As shown in Figure 8, the filler material removes sharp corners on the protrusions and provides a smooth channel for the movable member to move in. When the linear actuator 120 is subjected to an external force (e.g., being dropped or being hit by the linear actuator's chassis), the movable member 130 of the linear actuator will not collide with sharp corners during its movement, thereby improving the robustness of the linear actuator 120.

[0128] More specifically, a cross-sectional view of the linear actuator is shown in FIG. 9, and a sub-cross-sectional view (showing the magnetic flux lines through the movable and fixed members) is shown in FIG. 9A.

[0129] 10 and 11 are diagrams of an exemplary flexible conductive band 150 for use in a linear actuator according to an embodiment of the present invention.

[0130] As shown in these figures, the flexible conductive band 150 may include a plurality of notches 170 that may be distributed around at least one edge of the flexible conductive band 150. In some cases, there is a first plurality of notches 170 along a first edge of the flexible conductive band 150 and a second plurality of notches along a second edge of the flexible conductive band 150.

[0131] In some cases, the linear actuator may include features that interact with notches in the flexible conductive bands to ensure that adjacent flexible conductive bands do not contact each other and to improve rotational movement of the flexible conductive bands between the power rails of the electrical interface, although such features are not required.

[0132] These flexible conductive bands 150 may be flexible metal foils, such as stainless steel, coated on at least one side. In some examples, this coating may be titanium nitride (which may be applied, for example, by vacuum deposition or sputtering). This coating provides a very low coefficient of friction, further improving long-term operation of the bands and tracks.

[0133] Alternatively, high-performance polymer film materials (such as KAPTON™ or PET (polyethylene terephthalate), a type of polyimide plastic film) can be used instead of metal foil. These polymer films offer excellent flexibility and can be repeatedly bent and folded without failure. This polyimide film can also be coated with a number of highly conductive coatings and finishes, such as graphene. Further coatings can then be applied by ion deposition in solution via electroless plating or electroplating. This allows copper chloride, copper sulfate, nickel, palladium, ruthenium, or other suitable metals to be applied in solution.

[0134] The process of adding multiple platings and coatings to flexible plastic substrates is well suited to mass-produced miniature motors, further reducing reliance on expensive metals currently used in such motors.

[0135] Coatings can also be applied to polymer films using liquid-based nanosilver inks. Such inks can be deposited by inkjet delivery or silkscreen or gravure printing processes. These processes use photocurable nanosilver oxide inks that instantly transform (via surface reduction) into a metallic state upon contact with polymers such as PET (polyethylene terephthalate). This oxide-to-metallic transformation (a moisture-assisted electron conversion) can be used to facilitate the further deposition of electroless copper (on top of the cured nanosilver coating), resulting in very low-cost conductive flexible bands or discs for use in the present invention.

[0136] The foregoing description has been presented with reference to presently disclosed embodiments of the invention. Those skilled in the art, familiar with the field and technology to which the invention pertains, will understand that modifications and variations of the described structure may be made without significantly departing from the principles, spirit, and scope of the invention. As those skilled in the art will appreciate, the drawings are not necessarily to scale, and any feature or combination of features described in any embodiment may be incorporated into any other embodiment, or combined with any other feature of the other embodiments, as appropriate. Accordingly, the foregoing description should not be read as relating solely to the exact structure described and illustrated in the accompanying drawings, but rather as consistent with and supporting the following claims, which have their fullest and fairest scope. [Explanation of symbols]

[0137] 100 Cylindrical Linear Actuator 105 Fixing member 106 chassis 107a First Fixed Power Rail 107b Second Fixed Power Rail 110 Movable parts 112a First Movable Power Rail 112b Second Moving Power Rail 115 guide rail 115a First guide rail 115b Second guide rail 120 Rectangular Linear Actuator 125 Fixing member 130 Movable parts 150 Flexible Conductive Band 170 notches 300, 310 Permanent magnet assembly 350 magnetic core structure 360 central core 361, 362 protrusion, core protrusion 365 Filling material 370 Outer hollow part 371, 372 protrusion, hollow part protrusion 375 Long and narrow slot 380, 385 Gap region 390 Roller 400 permanent magnets

Claims

1. 1. A permanent magnet assembly for use in a non-commutated linear actuator, comprising: a magnetic core structure; a permanent magnet having a first magnetic pole and a second magnetic pole; The magnetic core structure comprises: a central core portion connected to the first magnetic pole of the permanent magnet; an outer hollow portion connected to the second pole of the permanent magnet; a gap region located between the central core and the outer hollow portion, the magnetic core structure is arranged such that magnetic flux generated by the permanent magnet flows between the central core portion and the outer hollow portion through the gap region; The magnetic core structure includes one or more protrusions extending into the gap region.

2. the one or more protrusions of the magnetic core structure include one or more core portion protrusions; The permanent magnet assembly of claim 1 , wherein the one or more core portion projections extend radially outward from the central core portion into the gap region.

3. the one or more protrusions of the magnetic core structure include one or more hollow protrusions; 10. A permanent magnet assembly according to any one of the preceding claims, wherein the one or more bore projections extend radially inward from the outer bore into the gap region.

4. 4. The permanent magnet assembly of claim 3, when dependent on claim 2, wherein at least one core portion projection of the one or more core portion projections corresponds to and is aligned with a corresponding hollow portion projection of the one or more hollow portion projections.

5. 10. A permanent magnet assembly according to any one of the preceding claims, wherein the central core has an axial cross section that is approximately circular, approximately oval, or approximately square.

6. the hollow portion has an axial cross-section that is approximately circular, approximately oval, or approximately square; 10. A permanent magnet assembly according to any one of the preceding claims, wherein the outer hollow portion includes at least one elongated slot along its length to allow access to the gap region.

7. 7. The permanent magnet assembly of claim 2, wherein the one or more core projections have an axial cross section that is approximately circular, approximately oval, or approximately square.

8. the one or more hollow projections have an axial cross-section that is approximately circular, approximately oval, or approximately square; 8. A permanent magnet assembly as claimed in any one of claims 3 to 7, wherein the hollow projection includes at least one elongated slot along its length to allow access to the gap region.

9. the one or more core projections include a plurality of core projections; and / or 9. A permanent magnet assembly according to claim 3, wherein the one or more hollow projections comprise a plurality of hollow projections.

10. Each of the plurality of core portion projections is spaced apart from an adjacent core portion projection by a second distance, The permanent magnet assembly of claim 9 , wherein each of the plurality of hollow projections is spaced apart from an adjacent hollow projection by a second distance.

11. further comprising a filler; 10. A permanent magnet assembly according to claim 2, wherein the filler material is positioned so as to cover sides of the one or more protrusions.

12. 12. The permanent magnet assembly of claim 11, when dependent on claim 9 or 10, wherein the filler material is arranged to completely fill spaces between adjacent core portion projections of the plurality of core portion projections, and the filler material is arranged to completely fill spaces between adjacent outer hollow portion projections of the plurality of hollow portion projections.

13. 13. The permanent magnet assembly of claim 11 or 12, wherein the filler material comprises a resin.

14. A fixing member; a movable member disposed to move relative to the fixed member in a longitudinal direction. The fixed member comprises a permanent magnet assembly according to any one of claims 1 to 12, The movable member is located within the air gap region of the permanent magnet assembly.

15. 15. The uncommutated linear actuator of claim 14, wherein the movable member includes at least one conductive winding.

16. the movable member includes a structure including at least one of a carbon fiber, a thermoplastic, a thermoset, or a synthetic fiber material; 16. The uncommutated linear actuator of claim 15, wherein the at least one conductive winding is wound around the structure.

17. 17. An uncommutated linear actuator according to claim 15 or 16, when dependent on claim 8, further comprising an electrical interface arranged to connect the at least one conductive winding to a power source through the at least one elongated slot.

18. 20. The uncommutated linear actuator of claim 17, wherein the electrical interface includes at least one flexible conductive band positioned to transfer electrical power from the power source to the at least one conductive winding on the moveable member.

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