Litz wire manufacturing method and coil structure

Abstract

The invention relates to a Litz wire manufacturing method and a coil structure, a Litz wire is divided into an inner layer structure and an outer layer structure, the inside of the Litz wire is formed by twisting a plurality of mutually insulated wires, the outside of the Litz wire is covered by an insulating layer, the number of strands of the internally twisted wires is more than 2700, the diameter of a copper wire used for wire twisting is more than 0.2 mm, and the Litz wire is directly blanked and trimmed without winding and forming; according to the Litz wire, a pole-phase group is directly embedded in a stator iron core groove, and only two coil lead outgoing heads are arranged in the pole-phase group, so that welding among coils is reduced; and after the soft litz wire is embedded, the end part can be directly shaped, so that the soft litz wire can be orderly arranged in sequence.

Description

Technical Field

[0001] The invention relates to the field of motor manufacturing, and in particular to a litz wire manufacturing method and a coil structure. Background Art

[0002] Litz wire is a special conductor structure, which is made of multiple insulated thin wires twisted or braided according to a certain rule. This structure can significantly reduce AC losses in high-frequency applications, especially the losses caused by skin effect and proximity effect. The design of Litz wire allows the current to be evenly distributed between each individual wire, thereby improving the overall conductive efficiency. Litz wire is mainly used in high-frequency and high-power motor industry, high-frequency transformer industry and inductive wireless charging industry. High-frequency Litz wire is made of multiple strands of mutually insulated single wires twisted together, and is usually used in applications with operating frequencies between 10kHz and 5 MHz. At present, Litz wires mostly use copper or aluminum alloy wire cores. The single strands are coated with an insulating layer (generally insulating varnish), and then twisted into the required shape, and then the required coil is formed through processes such as winding, pressing, and baking. The common features of this type of Litz wire are that the number of core strands is small and the core diameter is small, which will lead to an increase in skin effect and proximity effect. The different insulation layers wrapped outside the wire after twisting will make it impossible to meet the requirements of direct embedding and no need to wrap the ground insulation after the coil is formed. The search did not find the same technical solution as the present invention, but only found some related comparative technical documents, mainly the following: 1. The patent with application number 202020211869.1 discloses a permanent magnet three-phase synchronous motor, including a stator with a toothed coil winding, which is designed as a hollow winding and has a high-frequency Litz wire with a rectangular profile. The high-frequency Litz wire is composed of a large number of electrically insulated enameled copper wires, which are twisted and then pressed into a rectangular profile. Compared with a single unpressed wire, a significantly higher copper filling factor is obtained by pressing the Litz wire cross section. In addition, it is known to use enameled wire to make coil windings. Enameled wire is a wire, wherein this conductive wire has, for example, a paint layer, and an additional outer layer (baking layer) in addition to an insulating layer. The paint layer is, for example, a thermoplastic layer. When heated, the paint layer is softened and can be combined with the paint layer of the adjacent wire. This process is also called baking treatment. The baking treatment ensures that the geometry of the coil is permanently maintained. At the same time, the patent describes a method for manufacturing a component having a winding for a motor and a motor including such a component. The method comprises the following steps: one or more wires are wound into a coil. The wire is an enameled wire having a conductive core, an insulating layer and an outer baking layer. The wound coil is then pressed with the aid of a pressing tool. Finally, a baking process is performed on the pressed coil to maintain the geometric shape of the coil.

[0003] 2. The patent with application number 202021901891.5 discloses a hot air Litz wire, characterized in that it includes a plurality of copper conductors, polyurethane, polyester fastening wire and polyester thermal fuse wire, the polyurethane is coated on the outside of each of the copper conductors to form an enameled wire, the enameled wire is spirally twisted into a stranded wire, the polyester fastening wire is spirally wound on the outside of the stranded wire, the double-sided thickness of the polyester fastening wire is 0.004-0.012mm, the polyester thermal fuse wire is spirally wound on the outside of the polyester fastening wire, the double-sided thickness of the polyester thermal fuse wire is 0.004-0.012mm, and the outside of the polyester thermal fuse wire is coated with a surface lubricant.

[0004] 3. Patent application No. 201821934725.8 discloses a highly conductive Litz wire, characterized in that: the Litz wire includes a core layer, the core layer is formed by coaxially twisting a plurality of conductive wires, each of the conductive wires includes an aluminum alloy core layer, a copper layer and an insulating layer sequentially coated from the inside to the outside; the diameter of the conductive wire is 0.05-0.15mm; the core layer is formed by twisting 100-110 conductive wires with a diameter of 0.06-0.10mm; the core layer is formed by twisting 280-320 conductive wires with a diameter of 0.08-0.12mm; the core layer is formed by twisting 1800-2200 conductive wires with a diameter of 0.08-0.12mm.

[0005] In the above three schemes, the Litz wire uses a copper or aluminum alloy wire core, and the single-strand wire is coated with an insulating layer (generally insulating paint), and then twisted into the required shape, and then formed into the required coil through processes such as winding, pressing, and baking. The common point of the Litz wires in the above three schemes is that the number of core strands is small, and the maximum is only 2200 strands. In addition, the core diameter is small and the insulation layer wrapped outside the wire after twisting is different. It cannot meet the requirements that the Litz wire can be directly embedded and does not need to be wrapped for ground insulation after the coil is formed. Therefore, it is necessary to make improvements. Summary of the invention

[0006] The technical problem to be solved by the present invention is: to provide a method for manufacturing Litz wire and a coil structure. The Litz wire manufactured according to the manufacturing method has a large number of core strands, a large core diameter, and different insulation layers wrapped outside the twisted wires. The requirements that the Litz wire can be directly embedded and does not need to be wrapped for ground insulation after the coil is formed can be met. The skin effect and proximity effect can be well weakened to reduce eddy current losses.

[0007] The technical solution proposed by the present invention is: a Litz wire structure, the Litz wire is divided into an inner and outer two-layer structure, the inner layer is formed by twisting multiple insulated wires together, and the outer layer is covered by an insulating layer. The number of wire strands after the inner twisting is more than 2700 strands, and the diameter of the copper wire used for the wire twisting is more than 0.2mm.

[0008] Furthermore, the outside of the Litz wire is wrapped with an insulating layer, and the insulating material used for wrapping is determined by the heat resistance grade of the motor. For example, when the heat resistance grade is required to be 180°C, polyimide film mica tape can be used for wrapping. After wrapping, it is not baked and cured to ensure the softness of the coil.

[0009] Furthermore, the surface of the inner conductor of the Litz wire is covered with a resin paint film, and the resin paint film forms an insulating layer insulated from each other in the inner conductor.

[0010] Furthermore, the cross-sectional shape of the Litz wire is a rectangular structure, and the outside is wrapped with an insulating tape to form an insulating layer.

[0011] Furthermore, the cross-sectional shape of a single conductor inside the Litz wire is a hexagon.

[0012] A method for manufacturing a Litz wire coil comprises first twisting more than 2700 strands of self-insulated copper wires together, then wrapping a soft insulating layer around the twisted round Litz wire, then shaping the round Litz wire into a square shape using a shaping tool, and then directly embedding the soft square Litz wire into a core slot of a motor stator to form a Litz coil structure; the method comprises the following steps: Step 1: Make multiple strands of internal wires; select copper wires with more than 2700 strands, the diameter of the copper wires used is more than 0.2mm, and the outside of the wires is covered with a resin paint film; Step 2: Arrange more than 2700 strands of copper wire in a "one" shape to form a wire row, and perform square pressing and heating to shape the wire row composed of more than 2700 strands of copper wire: use the upper, lower, left and right pressing rollers to squeeze the wire row in four directions at the same time to form a rectangular wire; Step 3: Film the rectangular wire and bake the film-wrapped rectangular wire before the finished product is collected. Heat it to 120 degrees Celsius to debond the enameled single wires bonded together in the film-wrapped rectangular wire, and complete the production of the Litz wire. Step 4: Determine the length of the Litz wire according to the size of the stator core slot and the required number of turns, and then cut the Litz wire to the required length of the stator core slot; Step 5: directly embed the Litz wire segments cut according to the required length of the stator core slot into a pole phase group in the stator core slot, and ensure that only two coil leads are exposed in one pole phase group, reducing the welding between coils; Step 6: After the soft Litz wire is embedded, use a punch, hammer or other shaping tools to arrange the wire turns into the desired shape so that they are arranged in order to form an embedded Litz coil.

[0013] Furthermore, the Litz wire is firstly formed by twisting the insulated conductors into a circle, and then the circle is pressed into a rectangle with a required cross-sectional size, and the size is based on the motor design requirements.

[0014] Furthermore, after the Litz wire is pressed and formed, an insulating layer of a corresponding heat-resistant grade is wrapped around the outside of the wire core, and the insulating layer is formed by wrapping a soft insulating tape to ensure the softness of the Litz wire.

[0015] Furthermore, when the Litz wire is embedded, a manual rubber hammer is used for direct embedding, and the curved portion needs to be manually bent and formed step by step, and a manual rubber hammer is used to assist in hammering.

[0016] Furthermore, the Litz wire coil is continuously embedded by directly placing it into the iron core, and there is no breakpoint between the coils of the same pole phase group that needs to be connected; the ends of the coils after embedding are directly shaped and arranged in sequence.

[0017] The beneficial effects of the present invention are as follows: (1) by increasing the number of strands and diameter of the internal wire of the Litz, the skin effect and the proximity effect are reduced, the current-carrying cross-sectional area is increased, and the high-frequency loss is reduced. (2) The coil manufacturing process is to first shape the wire, then wrap it with an insulating tape, and then directly embed the Litz wire in the stator slot of the motor, without the need for winding, forming or curing steps, simplifying the process flow and increasing the manufacturing efficiency. (3) The insulation layer is wrapped around the outside of the coil, and the insulation layer is not cured, so the wire turns are relatively soft, and the end of the wire after embedding can be directly shaped to make the wires arranged neatly. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the Litz wire structure provided by an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the coil structure.

[0020] Description of reference numerals: conductor 1, insulating layer 2. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0022] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0023] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0024] In the actual work of the inventor, it was found that even if the existing Litz wire uses 2200 strands of multi-strand wires with a diameter of 0.08-0.12mm twisted together, then wrapped with insulating tape on the outside, and then made into a formed coil, and finally embedded in the motor stator; this method still has the defects of a small number of wire cores, a small wire core diameter, and different insulating layers wrapped on the outside after the wires are twisted. It cannot meet the requirements that the Litz wire can be directly embedded and does not need to be wrapped for ground insulation after the coil is formed. In particular, it is necessary to use a copper or aluminum alloy wire core, coat a single strand of wire with an insulating layer (generally insulating varnish), and then twist it into the required shape, and then form the required coil through winding, pressing, baking and other processes. This can easily destroy the insulating structure of the Litz wire during embedding, resulting in insulation failure of the Litz wire.

[0025] After studying various schemes, the inventor has summarized a method for making a Litz wire coil, which includes first twisting more than 2700 strands of self-insulated copper wire together, then wrapping a soft insulating layer on the outside of the twisted round Litz wire, and then using a shaping tool to shape the round Litz wire into a square shape, and then directly embedding the soft square Litz wire into the core slot of the motor stator to form a Litz coil structure; the method includes the following steps: Step 1: making a plurality of internal wires, the number of which is more than 2700 strands, the diameter of the copper wire used is more than 0.2 mm, and the outside of the wire is covered with a resin paint film; Step 2: Arrange more than 2700 strands of copper wire in a "one" shape to form a wire row, and perform square pressing and heating to shape the wire row composed of more than 2700 strands of copper wire: use the upper, lower, left and right pressing rollers to squeeze the wire row in four directions at the same time to form a rectangular wire; Step 3: Film the rectangular wire and bake the film-wrapped rectangular wire before the finished product is collected. Heat it to 120 degrees Celsius to debond the enameled single wires bonded together in the film-wrapped rectangular wire, and complete the production of the Litz wire. Step 4: Determine the length of the Litz wire according to the size of the stator core slot and the required number of turns, and then cut the Litz wire to the required length of the stator core slot; Step 5: Cut the Litz wire according to the required length of the stator core slot and directly embed it into a pole phase group in the stator core slot. There are only two coil leads in one pole phase group, which reduces the welding between coils. Step 6: After the soft Litz wire is embedded, use a punch, hammer or other shaping tools to shape the wire turns into the desired shape so that they are arranged in order.

[0026] Furthermore, the Litz wire is firstly formed by twisting the mutually insulated conductors 1 into a circle, and then the circle is pressed into a rectangle with a required cross-sectional size, and the size is based on the motor design requirements.

[0027] Furthermore, after the Litz wire is pressed and formed, an insulating layer of a corresponding heat-resistant grade is wrapped around the outside of the wire core, and the insulating layer is formed by wrapping a soft insulating tape to ensure the softness of the Litz wire.

[0028] Furthermore, when the Litz wire is embedded, a manual rubber hammer is used for direct embedding, and the curved portion needs to be manually bent and formed step by step, and a manual rubber hammer is used to assist in hammering.

[0029] Furthermore, the Litz wire coil is continuously embedded by directly placing it into the iron core, and there is no breakpoint between the coils of the same pole phase group that needs to be connected; the ends of the coils after embedding are directly shaped and arranged in sequence.

[0030] The structure of the Litz wire coil produced according to the above production method is as follows Figure 1-2 As shown, a Litz wire has an inner and outer two-layer structure. The inner layer is formed by twisting a plurality of mutually insulated wires 1, and the outer layer is covered by an insulating layer 2. The number of strands of the inner twisted wire 1 is more than 2700, and the diameter of the copper wire 1 used for the wire twisting is more than 0.2 mm.

[0031] Furthermore, the outside of the Litz wire is wrapped with an insulating layer 2, and the insulating material used for wrapping is determined by the heat resistance grade of the motor. After wrapping, it is not baked and cured to ensure the softness of the coil.

[0032] Furthermore, the surface of the inner conductor 1 of the Litz wire is covered with a resin paint film, so as to insulate the inner conductors 1 from each other.

[0033] Furthermore, the cross-sectional shape of the Litz wire is a rectangle.

[0034] Furthermore, the cross-sectional shape of a single conductor 1 inside the Litz wire is a hexagon.

[0035] The beneficial effects of the present invention are as follows: (1) by increasing the number of strands and diameter of the internal wire 1 of the Litz coil, the skin effect and the proximity effect are reduced, the current-carrying cross-sectional area is increased, and the high-frequency loss is reduced. (2) the coil manufacturing process does not require winding, forming or curing steps, the process flow is simplified, and the manufacturing efficiency is higher. (3) the coil is wrapped with an insulating layer 2, and the insulating layer 2 is not cured, so the wire turns are relatively soft, and the rear end of the embedded wire can be directly shaped so that the wires 1 are arranged neatly.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for manufacturing a litz wire coil, characterized in that: First, more than 2700 strands of self-insulated copper wires are twisted together, and then a soft insulating layer is wrapped around the twisted circular magnetic wires. Then, a shaping tool is used to shape the circular magnetic wires into squares, and then the soft square magnetic wires are directly embedded into the core slots of the motor stator to form a magnetic coil structure; the steps include: Step 1: Make multiple internal wires, the number of which is more than 2700, the diameter of the copper wire used is more than 0.2mm, and the outside of the wire is covered with a resin paint film; Step 2: Arrange more than 2700 strands of copper wire in a "one" shape to form a wire row, and perform square pressing and heating to shape the wire row: use the upper, lower, left and right pressing rollers to squeeze the wire row in four directions at the same time to form a rectangular wire; Step 3: Film the rectangular wire and bake the film-wrapped rectangular wire before the finished product is collected. Heat it to 120 degrees Celsius to debond the enameled single wires bonded together in the film-wrapped rectangular wire, and complete the production of the Litz wire. Step 4: Determine the length of the Litz wire according to the size of the stator core slot and the required number of turns, and then cut the Litz wire to the required length of the stator core slot; Step 5: Cut the Litz wire according to the required length of the stator core slot and directly embed it into a pole phase group in the stator core slot. There are only two coil leads in one pole phase group, which reduces the welding between coils. Step 6: After the soft Litz wire is embedded, use a punch, hammer or other shaping tools to shape the wire turns into the desired shape so that they are arranged in order.

2. A method for manufacturing a litz wire coil according to claim 1, characterized in that: The Litz wire is firstly made by twisting the mutually insulated conductors (1) into a circle, and then pressing the circle into a rectangle with a required cross-sectional size, the size of which is determined according to the design requirements of the motor.

3. A method for manufacturing a litz wire coil according to claim 2, characterized in that: After the Litz wire is pressed and formed, an insulating layer of a corresponding heat-resistant grade is wrapped around the wire core, and the insulating layer is formed by wrapping a soft insulating tape to ensure the softness of the Litz wire.

4. A method for manufacturing a litz wire coil according to claim 3, characterized in that: When the Litz wire is embedded, a manual rubber hammer is used for direct embedding, and the bent portion needs to be manually bent and formed step by step, and the manual rubber hammer is used to assist in hammering.

5. A method for manufacturing a litz wire coil according to claim 4, characterized in that: The Litz wire coil is continuously embedded by directly placing it into the iron core, and there is no breakpoint between the coils of the same pole phase group that needs to be connected; the ends of the coils after embedding are directly shaped and arranged in sequence.

6. A litz wire structure manufactured by the litz wire coil manufacturing method according to any one of claims 1 to 5, characterized in that: The Litz wire is divided into an inner and outer two-layer structure. The inner layer is formed by twisting a plurality of mutually insulated wires (1), and the outer layer is covered by an insulating layer (2). The number of strands of the inner twisted wires (1) is more than 2700, and the diameter of the copper wires (1) used for the wire twisting is more than 0.2 mm.

7. A Litz wire according to claim 6, characterized in that: The Litz wire is wrapped with an insulating layer (2) on the outside. The insulating material used for wrapping is of a grade determined by the heat resistance grade of the motor. After wrapping, it is not baked and cured to ensure the softness of the coil.

8. A Litz wire according to claim 6, characterized in that: The surface of the inner conductors (1) of the Litz wire is covered with a resin paint film, so as to achieve the effect of insulating the inner conductors (1) from each other.

9. A Litz wire according to claim 6, characterized in that: The cross-sectional shape of the Litz wire is a rectangle.

10. A Litz wire according to claim 6, characterized in that: The cross-sectional shape of a single conductor (1) inside the Litz wire is a hexagon.

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