JP2010062488A - Method of manufacturing coil - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing a coil that can reduce an increase in electrical resistance caused by residual stress or residual strain and can relieve a change in shape caused by the spring back.
A method of manufacturing a coil 1 includes a forming step of forming a coil by winding a winding 2 mainly composed of copper and having an insulating coating, and a heat treatment step of energizing and heating the coil. including.
[Selection] Figure 4

Description

  The present invention relates to a method for manufacturing a coil. More specifically, the present invention relates to a method for manufacturing a coil that can remove residual strain and residual stress generated in the process of forming a coil by winding a winding, thereby reducing the electrical resistance of the coil and removing spring back.

  For example, a stator of a motor or a generator is configured by winding a coil around a core. In order to increase the efficiency of a motor or the like, it is necessary to increase the space factor in the coil. For this reason, a coil is often formed by edgewise winding a rectangular wire having a rectangular cross section.

The edgewise coil is configured by winding the rectangular wire in the thickness direction (small cross-sectional dimension direction) while bending it in the width direction (large cross-sectional dimension direction). By adopting this configuration, the gap between the windings can be set small. For this reason, a high space factor can be obtained.
JP-A-2005-304244

In the process of manufacturing the edgewise coil as described in Patent Document 1, a large tensile stress acts on the outer peripheral portion of the rectangular coil, while a large compressive stress acts on the inner peripheral portion. Due to these processing forces, distortion and internal stress are generated in the coil after the forming process. These strains and internal stresses increase the electrical resistance of the coil and increase the amount of heat generation, thereby reducing the efficiency of the coil.

  In addition, a springback may occur due to the residual strain or residual stress, and the coil may not be formed with high dimensional accuracy. For this reason, a member or the like for holding the coil in a predetermined shape is required in a subsequent assembly process or the like, or it is often assembled in a state where a stress for correction is applied. As a result, the residual stress and the residual strain are increased accordingly, and the electric resistance of the coil is increased.

  The present invention provides a method for manufacturing a coil that solves the above problems, reduces an increase in electrical resistance caused by residual stress or residual strain, and can alleviate a change in shape due to the spring back. .

  The invention described in claim 1 is a method for manufacturing a coil, wherein a coil is formed by winding a wire material having copper as a main component and an insulating coating, and a heat treatment in which the coil is energized and heated. Process.

  When a cold-worked metal is heated, the property changed by the processing returns to the state before the processing. This operation is called annealing. By performing the annealing treatment, the residual strain and residual stress can be relaxed. The process of restoring properties by annealing is roughly divided into two. The first is a recovery process in which a crystal grain that has undergone internal strain by processing releases the internal strain as it is. The second is a recrystallization process in which crystal grains with internal strain are replaced by new crystals without internal strain. The recrystallization process involves the generation and growth of new crystal grain nuclei, which are different in shape and orientation from the old crystal grains.

  In a material having a low melting point such as copper used for the coil, the recovery proceeds even if it is left at room temperature, and the recovery is accelerated by further heating. Therefore, the residual strain and the residual stress can be effectively relieved also by heating to a temperature below the temperature at which the material structure changes. In particular, the electrical resistance can be effectively reduced by heating to room temperature or higher to accelerate the recovery process.

  The form of the coil and the method for performing the forming process are not particularly limited. For example, a cylindrical or rectangular cylindrical coil can be formed by using a known edgewise coil winding device.

  As long as the coil can be formed, the type of the wire is not limited. For example, tough pitch copper or oxygen-free copper widely used as a conductive material can be employed.

  The type of the insulating coating is not limited, but it is preferable to employ a material having heat resistance that can withstand the heat treatment temperature. For example, an amidoimide wire (AIW wire) or a polyimide wire (IMW) can be employed. These insulating coating layers have a softening point of 400 ° C. or higher, and a thermal shock resistance (a criterion for whether or not cracking occurs when heated while straining the insulating coating) is also 200 ° C. or higher. Therefore, by employing an insulating coating formed from these materials, the coil can be heat-treated without deteriorating the insulating coating.

  The heat treatment step is performed to remove residual strain and residual stress generated in the molding step. For example, in the case of copper wire, it is desirable to heat the coil to 200 ° C. or higher in order to effectively remove strain. On the other hand, if the heating temperature is equal to or higher than the heat resistance temperature of the insulating coating, the insulating coating is damaged. Therefore, as in the invention described in claim 3, it is desirable that the heat treatment step is performed by applying a temperature lower than the heat resistant temperature of the insulating coating to the coil.

  For example, when an amideimide wire (AIW wire) of tough pitch copper is employed, the heat resistance temperature of the insulating coating is 250 ° C to 300 ° C. Therefore, it is desirable to apply a temperature of 300 ° C. or lower. Further, since the recrystallization temperature of the tough pitch copper is about 200 ° C. to 250 ° C., it is effective to heat the coil to 200 ° C. or higher.

  Further, the heating and holding time can also be determined within a range that does not damage the insulating coating. In the case of the tough pitch copper amideimide wire, the effect of reducing electrical resistance can be obtained by heating to 250 ° C. and holding for 10 seconds or more.

  The heat treatment step is performed by energizing the coil. By adopting energization heating, heating can be performed from the inside of the wire constituting the coil. Therefore, the heat treatment can be effectively performed with little damage to the insulating coating. As long as the coil can be heated to a required temperature, the energization mode is not particularly limited, and a large DC current or a high-frequency current can be applied to the coil.

  By adopting the above configuration, residual strain and residual stress generated in the winding process can be relaxed. For this reason, the electrical resistance increased due to the residual strain and residual stress can be reduced.

  The invention described in claim 2 is performed by energizing the coil in the state where the heat treatment step is shaped and pressed into a predetermined shape.

  By heating in the shaped state, residual strain and residual stress can be reduced and springback can be relaxed.

  The shaping can be performed using a mold apparatus that can correct the spring back of the coil. The configuration of the mold apparatus is not particularly limited, as long as the diameter of the cylindrical coil is uniformed or the coil can be held so as to reduce the axial gap between the windings. By relaxing the spring back, the dimensional accuracy can be increased.

  Furthermore, when heated above the recrystallization temperature, the metal structure itself changes, so that the residual strain and residual stress can be greatly relaxed. Therefore, as in the invention described in claim 8, by heating the wire to the recrystallization temperature or higher, not only the electric resistance of the coil is reduced, but also the spring back can be more effectively relaxed.

  Although the actual recrystallization temperature varies depending on the degree of processing, for example, the recrystallization temperature of copper is generally 200 ° C. to 250 ° C. By heating to this temperature, the residual strain and residual stress of the coil are alleviated. It is possible to reduce the electrical resistance and effectively relieve the spring back.

  On the other hand, the heat resistance of the amideimide wire is 200 ° C. to 250 ° C., and the heat treatment step can be performed without adversely affecting the insulating coating.

  The invention described in claim 4 performs the heat treatment step while cooling the outer surface of the coil. The outer surface of the coil includes not only the outer peripheral surface of the cylindrical coil but also the inner peripheral surface and the surface of each winding.

  In the present invention, the coil is heated from the inside of the winding by energizing the coil. Therefore, by cooling the outer surface of the coil, the coil can be heated while protecting the insulation coating of the winding. Further, as in the invention described in claim 7, the heat treatment step is performed by applying a temperature equal to or higher than the heat resistant temperature of the insulating coating to the coil, and cooling the insulating coating to the heat resistant temperature or lower. It can be carried out. This makes it possible to perform an effective heat treatment without damaging the insulating coating.

  Further, even when a winding having a recrystallization temperature higher than the heat resistance temperature of the insulating coating is adopted, the coil can be heated to the recrystallization temperature or higher by performing the heat treatment step while cooling. . For this reason, not only can the residual strain and the residual stress be relieved to reduce the electric resistance, but also the spring back can be effectively relieved.

  The method for performing the cooling is not particularly limited. As in the invention described in claim 5, the heat treatment step can be performed while any one of cooling water, cooling oil or cooling gas is applied to the outer peripheral surface of the coil.

  According to a sixth aspect of the present invention, the heat treatment step is performed in an inert gas atmosphere. By performing in an inert gas atmosphere, deterioration of the insulating film can be prevented. For example, the heat treatment step can be performed in a nitrogen atmosphere. Furthermore, the heat treatment step can be performed while cooling the outer surface of the coil by allowing the ambient nitrogen to flow around the coil while maintaining the nitrogen at a low temperature. Moreover, the said heat processing process can also be performed by making cooling water or cooling oil act on the said coil in inert gas atmosphere.

  In addition, when the heat treatment is performed while cooling, the heating and holding time can be increased. Therefore, the metal structure of the coil winding can be adjusted to a desired form.

  By the heat treatment step of energizing and heating the coil, the residual strain and residual stress generated in the coil can be relaxed without damaging the insulation coating, the electrical resistance can be reduced, and the spring pack can be relaxed.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In this embodiment, the present invention is applied to a rectangular cylindrical coil mounted on a stator of an electric motor.

  FIG. 1 is an overall perspective view of a coil 1 that performs processing according to the present invention. As shown in this figure, the coil 1 according to the present embodiment is wound in the thickness direction (small cross-sectional dimension direction) while bending the rectangular wire 2 having a rectangular cross section in the width direction (large cross-sectional dimension direction), That is, it is formed by edgewise winding.

  The winding 2 according to the present embodiment employs a tough pitch copper wire having a rectangular cross section of 0.92 mm × 9.60 mm coated with an amide imide resin (amide imide wire).

  The coil 1 is formed by winding a linear winding 2 around the outer periphery of a mold member corresponding to the inner space. For this reason, in the rectangular corner portion 3 of the coil 1, the inner peripheral portion is largely compressed and deformed, and the outer peripheral portion is pulled and deformed.

  Due to the processing force, a spring back occurs in the coil 1 after molding. Springback is a phenomenon in which bending deformation returns to the direction opposite to the processed side due to elasticity after plastic processing.

  2 and 3 show the form of the coil 1 in which the springback has occurred. In these drawings, the amount of springback is drawn larger than the actual amount for easy understanding.

  In the case of the rectangular cylindrical coil 1 according to the present embodiment, the springback in the form in which the winding 2 of each turn shown in FIG. 2 is displaced from the coil axis, and the winding of each turn shown in FIG. In many cases, the spring back is rotated. Further, it is difficult to wind the windings of the turns adjacent to each other in the axial direction of the coil in close contact with each other, and a gap is formed between the windings of the turns. For this reason, as shown in FIG. 2, the axial height of the coil may be larger than the set value.

  Further, residual strain and residual stress resulting from processing are generated inside the winding 2, and the electrical resistance of the winding increases due to the residual strain and residual stress. As a result, if the stator is mounted on the core or the like as it is, the amount of heat generation may increase and the efficiency of the stator may decrease.

  In addition, when the coil 1 having the spring back is mounted on the core, it is often necessary to shape and mount the coil. On the other hand, if it is attached to the core in a state where the shaping force is applied, the coil 1 is further stressed, which may further increase the electrical resistance.

  In the present embodiment, as shown in FIG. 4, the coil is energized and heated while the coil is shaped into a predetermined shape.

  As shown in FIGS. 4 and 5, the shaping members 8 and 9 are brought into contact with each other from the side and axial directions of the coil 1 to hold the coil 1 in a predetermined shaping state. Then, the coil 1 is energized and heated.

  In the present embodiment, the shaping member 8 is brought into contact with the four side surfaces of the coil 1 toward the axis of the coil 1, so that the spring back associated with the deviation of the winding 2 from the coil axis and the rotational displacement around the axis can be obtained. The spring back is corrected. Further, the spring back in the axial direction is corrected by causing the rod-shaped shaping member 9 to act on each of the four end faces of the coil 1.

  In the above state, a lead wire is connected to both the terminal portions 4 and 5 of the coil 1 and a current is supplied from the energizing device 11 to energize. The magnitude | size and form of the said electric current are not specifically limited, What is necessary is just to supply with electricity so that the inside of the coil | winding 2 can be heated to required temperature.

  In the present embodiment, a 1 kHz alternating current of 500 V is applied for about 30 seconds. Thereby, a coil is hold | maintained in the state heated at about 220 degreeC. By holding at the above temperature, it is possible to recrystallize the copper of the winding, and it is possible to reduce or eliminate residual strain and residual stress. Further, since recrystallization proceeds in the shaped form, the springback can be reduced.

  Further, in the present embodiment, as shown in FIG. 6, the heat treatment step of the coil 1 can be performed while cooling the outer peripheral surface of the coil 1.

  In the embodiment shown in FIG. 6, the outer surface of the coil 1 is cooled by performing the heat treatment step in a nitrogen atmosphere and causing the cooled gaseous nitrogen N2 to flow axially in the inner and outer portions of the coil. is doing. The temperature and flow rate of the gaseous nitrogen N2 are set so that the insulating coating of the coil 1 can be maintained at 200 ° C. or lower.

  By performing heat treatment on the coil 1 while performing the cooling, the insulating coating is not heated to a temperature higher than the heat resistant temperature. Therefore, it is possible to prevent the insulating coating from deteriorating.

  Further, the heating temperature of the coil 1 can be raised to effectively remove the residual strain and residual stress, thereby reducing the electrical resistance of the coil, and the spring back can be surely relaxed.

  The present invention is not limited to the embodiment described above. It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined not by the above-described meaning but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  By adopting the coil manufacturing method according to the present invention, the electric resistance of the coil can be reduced and the efficiency of the stator and the like can be increased.

It is an external appearance perspective view of the coil which concerns on this invention. It is a front view which shows the state of the spring back of the coil shown in FIG. It is a top view which shows the state of the spring back of the coil shown in FIG. It is an external appearance perspective view which shows the state which shapes and heat-processes the coil shown in FIG. It is a top view of the coil which performs the heat processing process shown in FIG. It is sectional drawing which follows the IV-IV line in FIG.

Explanation of symbols

1 coil 2 winding

Claims (9)

A method for manufacturing a coil, comprising:
A forming step of forming a coil by winding a wire having copper as a main component and having an insulation coating;
The coil manufacturing method including the heat treatment process which energizes and heats a coil.   The said heat treatment process is a manufacturing method of the coil of Claim 1 performed by supplying with electricity in the state which shape-pressed the said shape | molded coil in the predetermined shape.   The said heat processing process is a manufacturing method of the coil in any one of Claim 1 or Claim 2 performed by making the temperature below the heat-resistant temperature of the said insulation coating act on the said coil.   The method for manufacturing a coil according to any one of claims 1 to 3, wherein the heat treatment step is performed while cooling an outer surface of the coil.   The said heat processing process is a manufacturing method of the coil of Claim 4 performed while making any one of a cooling water, a cooling oil, or a cooling gas act on the outer peripheral surface of the said coil.   The coil manufacturing method according to claim 1, wherein the heat treatment step is performed in an inert gas atmosphere. The heat treatment step is performed by applying a temperature higher than the heat resistance temperature of the insulating coating to the coil.
The method for manufacturing a coil according to any one of claims 4 to 6, wherein the insulating coating is performed while cooling to the heat resistant temperature or lower.   The manufacturing method of the coil of any one of Claim 1-7 which heats the said coil more than the recrystallization temperature of the employ | adopted material. While adopting an amide imide wire with insulating coating of tough pitch copper on the coil winding,
The said heat processing process is a manufacturing method of the coil in any one of Claims 1-8 performed by heating a coil to 150 to 250 degreeC and hold | maintaining for 10 seconds or more.

Images