JP7334103B2 - Induction heating device and induction heating method for rotary electric machine stator core - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an induction heating device and an induction heating method for a stator core of a rotating electrical machine, and more particularly to reducing abnormal heating in an annular yoke and efficiently heating teeth.

2. Description of the Related Art Conventionally, rotary electric machines such as motors and generators are configured by arranging a stator core and a rotor core to face each other in the radial direction. Stator cores are sometimes annealed to remove internal strain due to work hardening and to reduce core loss. In the stator core, residual strain is generated due to work hardening, especially in the teeth, so that portion may be annealed.

For example, a high-frequency magnetic flux is applied to the entire stator core from one side in the axial direction, in-plane eddy currents are caused to flow through the ends of the stator core, and the resulting Joule loss is used to heat the stator core.

In addition, as in the configurations described in Patent Documents 1 and 2, a coil (induction heating section) that performs induction heating closely covers the entire outer periphery of the stator core, and by energizing the coil, an induced current is generated in the stator core. It is known to flow and heat the stator core.

Further, as in the configuration described in Patent Document 3, the primary side yoke is passed through the inside of the coil, and the secondary side yoke magnetically coupled to the primary side yoke is passed through the center of the stator core to It is also known to pass an alternating current through the primary yoke to cause an axial magnetic flux to flow inside the stator core. According to this method, it is possible that the stator core can be heated by causing an induced current to flow in the stator core due to this axial magnetic flux.

JP 2013-5553 A JP 2012-5283 A JP 2018-81896 A

When high-frequency magnetic flux is applied to the entire stator core from one side in the axial direction, the magnetic flux interlinkage area in the stator core is large, so the demagnetizing field due to the eddy current increases, and the reactive power increases. Moreover, in this case, a large amount of heat is applied to parts other than the teeth that require annealing, resulting in large power consumption.

Further, in the methods described in Patent Documents 1 to 3, since the induced current flows only in the annular yoke portion on the outer circumference of the stator core, only the yoke portion can be heated.

Moreover, if the annular yoke is abnormally heated, the yoke may be overannealed or deformed.

An object of the induction heating device and the induction heating method for a rotating electric machine stator core of the present disclosure is to reduce abnormal heating in the annular yoke and to efficiently heat the teeth.

An induction heating apparatus for a rotating electric machine stator of the present disclosure is an induction heating apparatus for a rotating electric machine stator core including an annular yoke and a plurality of teeth extending radially inward from a plurality of positions in the circumferential direction of the yoke, wherein the rotating electric machine includes: A columnar central core, which is arranged on the inner peripheral side of the stator core and around which an exciting coil is wound, is arranged to face the axial end surface or the outer peripheral surface of the yoke on the outer peripheral side of the rotating electric machine stator core via a first heat insulating portion. at least one annular current source configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the yoke by the excitation coil; and the excitation coil. and a second heat insulating portion disposed between the outer peripheral surface of the rotating electrical machine stator core.

A rotary electric machine stator induction heating method of the present disclosure is a method of induction heating the teeth of the rotary electric machine stator core using the rotary electric machine stator core induction heating apparatus of the present disclosure, wherein an alternating current is supplied to the excitation coil. Thus, the induction heating method for a rotating electric machine stator core includes a magnetic flux generation step of inductively heating the teeth by causing the magnetic flux to flow through the central core and the teeth.

According to the induction heating device and the induction heating method for the rotating electric machine stator core of the present disclosure, abnormal heating in the annular yoke can be reduced, and the teeth can be efficiently heated.

1 is a perspective view showing a state in which a rotating electrical machine stator core is heated using the induction heating apparatus and induction heating method for a rotating electrical machine stator core of the embodiment, with the first heat insulating material omitted; FIG. It is the figure which looked at the induction heating apparatus from the axial direction one side in FIG. FIG. 2 is a perspective view of FIG. 1 with an outer yoke removed; 4 is an enlarged view of part A in FIG. 3; FIG. 2 is a schematic diagram of a cross section including the central axis of the induction heating device of FIG. 1. FIG. FIG. 6 is a diagram for explaining the reason why teeth are heated intensively by removing the outer yoke in FIG. 5 and the reason why abnormal heating of the end face of the stator yoke can be reduced. FIG. 7 is a view corresponding to FIG. 6 in an induction heating device of another example of the embodiment; FIG. 7 is a view corresponding to FIG. 6 in an induction heating device of another example of the embodiment; FIG. 3 is a view corresponding to FIG. 2 in an induction heating device of another example of the embodiment; FIG. 8 is a perspective view of an outer yoke used in another example of the induction heating device of the embodiment; FIG. 6 is a view corresponding to FIG. 5 in an induction heating device of another example of the embodiment; FIG. 12 is a diagram corresponding to FIG. 11 for explaining the reason why the abnormal heating of the end face of the stator yoke can be reduced by removing the outer yoke; FIG. 11 is a perspective view showing an induction heating device of another example of the embodiment with the outer yoke and the first heat insulating material removed. When heating the rotating electrical machine stator core by the induction heating device of the comparative example, the Joule loss density (W/m ³ ) in a part of the rotating electrical machine stator core in the circumferential direction when the thickness of the first heat insulating portion is large (5 mm). It is a figure which shows the analysis result of distribution. When the rotating electrical machine stator core is heated by the induction heating device shown in FIG. 1 , the Joule loss density (W/m ³ ) is a diagram showing the analysis results of the distribution of . When the rotating electric machine stator core is heated by the induction heating device shown in FIG. 11, the Joule loss density (W/m ³ ) is a diagram showing the analysis results of the distribution of .

Hereinafter, embodiments of an induction heating device and an induction heating method for a rotary electric machine stator core according to the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, numerical values, quantities, etc. are examples for facilitating understanding of the present disclosure, and may be changed as appropriate according to the specifications of the rotating electric machine stator core or the induction heating device. can. In the following description, similar elements are denoted by the same reference numerals in all drawings.

FIG. 1 is a perspective view showing a state in which the rotary electric machine stator core 10 is heated using an induction heating device 30 and an induction heating method for the rotary electric machine stator core 10 of the embodiment. FIG. 2 is a diagram of the induction heating device 30 viewed from one side in the axial direction in FIG. FIG. 3 is a perspective view of FIG. 1 with the outer yoke 54 removed. 4 is an enlarged view of part A in FIG. 3. FIG. FIG. 5 is a schematic diagram of a cross section including the central axis of the induction heating device 30. As shown in FIG.

A rotating electrical machine stator core 10 will be described with reference to FIGS. 1 to 5. FIG. The rotating electric machine stator core 10 is hereinafter referred to as the stator core 10 . Stator core 10 forms a stator together with stator coils (not shown). A stator, together with a rotor (not shown) located inside the stator, is used to form a rotating electric machine.

The stator core 10 is an annular magnetic component, and is formed of a laminated body in which, for example, a plurality of annular electromagnetic steel plates such as silicon steel plates are laminated in the axial direction (vertical direction in FIG. 1).

The stator core 10 includes a stator yoke 13 that is annular and arranged on the outer peripheral side, and a plurality of teeth 14 (FIGS. 1, 3, 4, 4A and 4B) extending radially inward from a plurality of circumferential positions on the inner peripheral surface of the stator yoke 13. 5). A plurality of teeth 14 are arranged at intervals in the circumferential direction. A slot 16 (FIG. 4), which is a groove, is formed between two adjacent teeth 14 .

The stator coil has three-phase coils of U, V, and W phases, and each coil is wound around a plurality of teeth 14 so as to straddle two slots 16 separated in the circumferential direction of stator core 10 .

When constructing a rotating electric machine, a rotor is arranged radially inside a stator. A rotating electrical machine is driven by supplying a three-phase alternating current to a three-phase stator coil during use. For example, a rotating electric machine is used as a permanent magnet type synchronous motor.

Stator core 10 is configured by laminating a plurality of electromagnetic steel sheets as described above, and a plurality of teeth 14 extend from the inner peripheral surface of stator yoke 13 . Each electromagnetic steel sheet is formed into a predetermined shape by punching or the like. As a result, work hardening occurs in the teeth 14, and strain (residual strain) is likely to occur. For this reason, the teeth 14 are annealed to remove internal strain and reduce iron loss.

For this reason, in the embodiment, an induction heating device 30 is used to anneal the stator core 10 . The induction heating device 30 is arranged on the inner peripheral side of the stator core 10, and includes a columnar central core 31 around which an exciting coil 33 is wound, two first heat insulating portions 40 (FIGS. 2 and 5), and a second heat insulating portion. 42 ( FIG. 5 ), two metal rings 44 and an outer yoke 54 . Note that FIG. 5 shows a schematic shape in which the diameter of the central core 31 is smaller than the shape shown in FIG. 1 in relation to the stator core 10 . 1, 3, and 4, illustration of the first heat insulating portion 40 and the second heat insulating portion 42 is omitted.

The central core 31 is made of a magnetic material and has a cylindrical shape, for example. Central core 31 is arranged along central axis O of stator core 10 . Both axial end portions of the center core 31 protrude axially from both axial end surfaces of the stator core 10 . The excitation coil 33 is arranged around the center core 31 and on the inner diameter side of the stator core 10 .

A highly insulating powder core such as a dust core or ferrite may be used for the central core 31 . The central core 31 may be made of an electromagnetic steel sheet. At this time, the central core 31 may be a laminated core obtained by laminating a plurality of electromagnetic steel sheets, a cylindrical wound core obtained by spirally winding a single electromagnetic steel sheet, or a plurality of electromagnetic steel sheets arranged radially in the radial direction. It is good also as a radial core which carried out.

If the cross-sectional shape of the central core 31 cut along a plane perpendicular to the central axis O is rectangular, the central core includes a plurality of elements divided in a direction parallel to one side, such as the width direction, and a plurality of elements. may be formed by combining If the central core is cylindrical, it may be formed from a plurality of elements divided at a plurality of positions in the circumferential direction.

The two first heat insulating portions 40 (FIGS. 2 and 5) are ring-shaped discs, and the axial end faces of the stator yoke 13 and the plurality of teeth 14 are formed on the axial end faces of the central core 31, respectively. placed to cover the The first heat insulating portion 40 can be a block made of an insulating material having heat insulating properties such as resin or ceramic.

Further, two metal rings 44 that are continuous in the circumferential direction are arranged in spaces on both axial end faces of the stator yoke 13 on the outer peripheral side of the stator core 10 . Each metal ring 44 has an annular shape and is arranged to face the axial end face of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. As a result, two metal rings 44 are opposed to each other on both axial end faces of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. Each metal ring 44 corresponds to an annular current source. Each metal ring 44 is configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the stator yoke 13 by the excitation coil 33, as will be described later. The metal ring 44 is made of a highly conductive material such as copper. Although the cross section perpendicular to the circumferential direction of the metal ring 44 is rectangular, the cross section may be circular or other shape.

Metal ring 44 and stator core 10 may be brought into contact with first heat insulating portion 40 . It should be noted that the first heat insulating portion may not be solid, but may be a highly heat insulating gas or air layer. 10 may be formed as the first heat insulating portion. By disposing the first heat insulating portion 40 between the axial inner surface of the metal ring 44 and the axial end surface of the stator core 10, heat escape from both ends of the teeth 14 in the axial direction is suppressed, and the teeth 14 are cooled. Efficient heating.

Furthermore, the second heat insulating portion 42 ( FIG. 5 ) is cylindrical and arranged between the outer peripheral surface of the exciting coil 33 and the inner peripheral surface of the stator core 10 . As with the first heat insulating portion 40, the second heat insulating portion 42 may be made of an insulating material having heat insulating properties, such as resin or ceramic. The inner peripheral surface of stator core 10 and the outer peripheral surface of exciting coil 33 may be brought into contact with second heat insulating portion 42 . It should be noted that the second heat insulating portion may be a gas having high heat insulating properties or an air layer instead of being solid. A vacuum gap formed between the surface and the inner peripheral surface of the stator core 10 may be used as the second heat insulating portion. By disposing the second heat insulating portion 42 between the outer peripheral surface of the exciting coil 33 and the inner peripheral surface of the stator core 10 , it is possible to prevent the exciting coil 33 from being excessively heated by the radiant heat from the stator core 10 . As a result, the excitation coil 33 can be protected and performance degradation of the excitation coil 33 can be suppressed.

The outer yoke 54 is arranged to cover the stator core 10 and the central core 31 . The outer yoke 54 is formed including a yoke element 57 having a rectangular cross section so that the shape of the outer yoke 54 when viewed along a cross section including the central axis is rectangular as shown in FIG. The yoke element 57 has a rectangular frame shape formed by connecting two parallel rectangular plate portions 57b to the longitudinal ends of two parallel rectangular plate portions 57a. The outer yoke 54 is connected to both axial end surfaces of the central core 31 so that the inner surfaces of the two plate portions 57a in the axial direction (vertical direction in FIG. 1) are in surface contact with each other. As a result, the outer yoke 54 is arranged to face both axial end surfaces of the central core 31 . In this state, a gap is formed between the inner peripheral surface of yoke element 57 of outer yoke 54 and the outer peripheral surface of stator core 10 . The outer yoke 54 is made of a magnetic material. For example, for the outer yoke 54, similarly to the central core 31, a highly insulating powder core such as a dust core or ferrite may be used. The outer yoke 54 may be formed of a laminate of electromagnetic steel sheets.

The induction heating method for the stator core 10 of the embodiment induction-heats the plurality of teeth 14 of the stator core 10 using the induction heating device 30 described above. At this time, first, as an arrangement step, as shown in FIGS. An outer yoke 54 is arranged around the central core 31 and the stator core 10 so that the axial inner surfaces of 54 are in contact with each other.

Then, as a magnetic flux generation step, an alternating current is supplied from a power supply (not shown) to the exciting coil 33, thereby causing the central core 31 and the stator core 10 to move in the direction of the solid line arrow α in FIG. A magnetic flux is passed through the teeth 14 of . The direction of the solid arrow α in FIG. 5 is the magnetic flux direction when current flows in the right side of FIG. As a result, high-frequency magnetic flux flows in the axial direction of the teeth 14, whereby the teeth 14 are induction-heated and annealed. At this time, the frequency of the alternating current flowing through the excitation coil 33 is set to a frequency (lower limit frequency) at which the skin thickness caused by eddy currents due to the high-frequency magnetic flux flowing in the stator core 10 is 1/3 or less of the circumferential width of the teeth 14. is preferred. More preferably, the alternating current frequency is a frequency (upper limit frequency) at which the skin thickness caused by eddy currents due to high-frequency magnetic flux is equal to or greater than the plate thickness of the electromagnetic steel sheet forming the stator core 10, and the circumferential width of the teeth 14 It is preferable that the frequency (lower limit frequency) is 1/3 or less. As a result, a large amount of electric current can be supplied to the teeth 14 and their root portions that need to be heated in the stator core 10, so that the portions that particularly need to be heated can be heated intensively by Joule loss.

FIG. 6 is a diagram for explaining the reason why the teeth 14 are heated intensively and the reason why the abnormal heating of the end face of the stator yoke 13 can be reduced by removing the outer yoke 54 in FIG. By supplying an alternating current to the excitation coil 33 as described above, a high-frequency magnetic flux flows in the axial direction of the teeth 14 . At this time, when the exciting coil 33 is energized, magnetic flux flows from the central core 31 to the axial direction of the teeth 14 in the direction of the solid line arrow α in FIG. generates an induced current in the circumferential direction of the stator yoke 13 . The induced current generates a magnetic flux that flows around the stator yoke 13 in the direction of the dashed-dotted line arrow β in FIG. This magnetic flux also flows through the teeth 14, and the magnetic flux direction at that time coincides with the magnetic flux direction of the solid-line arrow α. Therefore, since the magnetic flux density of the magnetic flux flowing through the teeth 14 in the axial direction can be easily maintained high, the strength of the eddy current flowing inside the teeth 14 can be easily maintained high, and the Joule loss of the eddy currents can heat the teeth 14 . is promoted.

According to the induction heating device 30 and the induction heating method for the stator core 10 described above, an alternating current is supplied to the excitation coil 33 wound around the central core 31 disposed on the inner peripheral side of the stator core 10, thereby heating the teeth. A high-frequency magnetic flux flows through 14 to increase Joule loss, thereby heating teeth 14 . As a result, the teeth 14 that particularly require heating are heated intensively, so that the teeth 14 can be efficiently heated. Therefore, the electric power required for heating the teeth 14 can be reduced, and the teeth 14 can be heated in a short time. In addition, since it is possible to suppress the concentrated heating of only the axial ends of the teeth 14, it is possible to prevent deterioration of the magnetic properties due to over-annealing.

Further, the induction heating device 30 includes a metal ring 44 as a ring-shaped current generating source disposed opposite to the axial end face of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. The metal ring 44 is configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the stator yoke 13 by the exciting coil 33 . This will be explained using FIG. First, consider the case where the thickness of the first heat insulating portion 40 is increased assuming that the metal ring 44 is not provided. In this case, a part of the magnetomotive force of the exciting coil 33 generates an induced current in the circumferential direction of the stator yoke 13 due to the alternating current flowing through the exciting coil 33 . The direction of the induced current in the circumferential direction is opposite to the current direction of the exciting coil 33 . This induced current generates a magnetic flux that flows around the stator yoke 13 in the direction of the dashed line arrow β in FIG. This magnetic flux may increase eddy currents near the axial end faces of the stator yoke 13 and cause excessive and concentrated heating of the axial ends of the stator yoke 13 .

According to the configuration of this example, the induced current flowing through the metal ring 44 can generate magnetic flux flowing around the metal ring 44 in the direction of the dashed arrow γ in FIG. 6, for example. The direction of the magnetic flux is opposite to the magnetic flux in the direction of the dashed line arrow β in the vicinity of the axial end face of the stator yoke 13 . As a result, the direction of the magnetic flux generated by the metal ring 44 is the direction in which the magnetic flux generated on the axial end surface of the stator yoke 13 by the excitation coil 33 is canceled. Therefore, the concentrated heating of the axial end portion of the stator yoke 13 due to the magnetic flux can be canceled or mitigated by the magnetic flux due to the induced current flowing through the metal ring 44, and the concentrated heating can be suppressed. Therefore, since the vicinity of the axial end face of the stator yoke 13 can be prevented from being excessively and intensively heated, abnormal heating in the stator yoke 13 can be reduced, and over-annealing and deformation of the stator yoke 13 can be suppressed.

Furthermore, in the case of this example, the outer yoke 54 is arranged to cover the central core 31 and face the axial end surface of the central core 31 . This outer yoke 54 can suppress leakage magnetic flux from the central core 31 to the outside of the induction heating device 30 . A gap may be formed between at least one of the axial end faces of the central core 31 and the inner side face of the outer yoke.

FIG. 7 is a diagram corresponding to FIG. 6 in an induction heating device 30a of another example of the embodiment. In the case of the configuration of this example, in the induction heating device 30 a , two short-circuited coils 46 are arranged in the space on both axial end faces of the stator yoke 13 on the outer peripheral side of the stator core 10 . Each short-circuited coil 46 is short-circuited at the winding start and the winding end. Each short-circuit coil 46 is arranged to face the axial end surface of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. As a result, two short-circuited coils 46 are arranged opposite to each other on both axial end surfaces of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. Each short-circuited coil 46 corresponds to an annular current source. Each short-circuit coil 46 is configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the stator yoke 13 by the exciting coil 33, similarly to the metal ring 44 configured in FIGS. The axial direction of the short-circuit coil 46 is aligned with the axial direction of the exciting coil 33 .

In the above configuration as well, the induced current flows through the short-circuited coil 46 instead of the metal ring 44 of the configuration shown in FIGS. be able to. The direction of the magnetic flux is opposite to the direction of the magnetic flux flowing near the axial ends of the stator yoke 13 due to the induced current generated in the circumferential direction of the stator yoke 13. Concentrated heating of the part can be suppressed. As a result, abnormal heating in the stator yoke 13 can be reduced, and over-annealing and deformation of the stator yoke 13 can be suppressed. Other configurations and actions in this example are the same as those in FIGS. The winding direction of the short-circuit coil 46 can be opposite to the winding direction of the exciting coil 33 as shown in FIG.

FIG. 8 is a diagram corresponding to FIG. 6 in an induction heating device 30b of another example of the embodiment. In the case of the configuration of this example, in the induction heating device 30 b , the two end surface side opposite polarity coils 48 are arranged in the space on both axial end surfaces of the stator yoke 13 on the outer peripheral side of the stator core 10 . Each end face side reverse polarity coil 48 is connected so as to have a reverse polarity with respect to the exciting coil 33 . Each end face side reverse polarity coil 48 is arranged to face the axial end face of the stator yoke 13 with the first heat insulating portion 40 interposed therebetween. As a result, two opposite-polarity coils 48 are arranged on both axial end surfaces of the stator yoke 13 so as to face each other with the first heat insulating portion 40 interposed therebetween. Each end face side reverse polarity coil 48 corresponds to an annular current source.

Here, "reverse polarity" means that the polarities of the two coils are reversed in the axial direction of the induction heating device 30b. The axial direction of the end surface side reverse polarity coil 48 is made to coincide with the axial direction of the excitation coil 33 . For example, when the winding directions of the end face side reverse polarity coil 48 and the excitation coil 33 are reversed, the winding end of the end face side reverse polarity coil 48 on one side in the axial direction (upper side in FIG. The winding end of the excitation coil 33 is connected to the winding start end of the end surface side opposite polarity coil 48 on the other side in the axial direction (lower side in FIG. 8). In addition, the winding end of the end face side reversed polarity coil 48 on the other axial side is connected to the winding start end of the end face side reversed polarity coil 48 on the one side in the axial direction via the power supply section. The winding direction of the end surface side reverse polarity coil may be the same as the winding direction of the exciting coil 33 . At this time, the winding end of the end face side reverse polarity coil on one axial side is connected to the winding end end of the excitation coil 33, and the winding start end of the excitation coil 33 is connected to the winding start end of the end face side reverse polarity coil on the other axial side. connect to the ends. In addition, the winding end of the opposite-polarity coil on the other side in the axial direction is connected to the starting end of the opposite-polarity coil on the one side in the axial direction via the power supply unit. 1 to 6 or the short-circuit coil 46 of FIG. configured to generate a magnetic flux in the

In the case of the above configuration, alternating current is supplied to the exciting coil 33 , so that alternating current also flows through the two end face side opposite polarity coils 48 . At this time, for example, a magnetic flux can be generated that flows around the end face side reverse polarity coil 48 in the direction of the dashed arrow δ in FIG. 8 . The direction of the magnetic flux is opposite to the direction of the magnetic flux flowing near the axial ends of the stator yoke 13 due to the induced current generated in the circumferential direction of the stator yoke 13. The concentrated heating can be canceled or mitigated by the magnetic flux generated by the current flowing through the end surface side reverse polarity coil 48, and the concentrated heating can be suppressed. As a result, abnormal heating in the stator yoke 13 can be reduced, and over-annealing and deformation of the stator yoke 13 can be suppressed. In this example, other configurations and actions are the same as the configuration in FIGS. 1 to 6 or the configuration in FIG.

In addition, in the configuration of FIG. 8, the total number of turns of the two opposite polarity coils 48 on the end surface side can be less than or equal to half the number of turns of the exciting coil 33 .

FIG. 9 shows an induction heating device 30c of another example of the embodiment, in which the outer yoke 54a has a shape similar to that of the outer yoke 54 in FIG. Two gate-shaped second yoke elements 59 are connected at the center in the longitudinal direction of the . Each second yoke element 59 is connected to the ends of two parallel rectangular plate portions 59a in the longitudinal direction so that a rectangular connecting plate portion 59b is perpendicular to the plate portions 59a. As a result, a cross-sectional shape cut at the center of the first yoke element 58 in the width direction (vertical direction in FIG. 9) of the outer yoke 54a and a cross section cut at the center of the second yoke element 59 in the width direction (horizontal direction in FIG. 9) The shape is the same shape as the outer yoke 54 in FIG. As shown in FIG. 9, the shape of the outer yoke 54a viewed from one end in the axial direction is a cross. Also in the case of the induction heating device 30c using the outer peripheral yoke 54a, leakage magnetic flux from the central core 31 to the outside of the induction heating device 30c can be suppressed as in the configuration of FIGS. Other configurations and actions in this example are the same as those in FIGS.

FIG. 10 is a perspective view of an outer yoke 54b used in another example of the induction heating device of the embodiment. The outer yoke 54b is arranged to cover the stator core 10 and the central core 31 shown in FIG. As with the outer yoke 54 in FIG. 5, the outer yoke 54b has two ridges at both ends of the cylindrical portion 55 so as to close the openings at both ends of the cylindrical portion 55 so that the shape of the cross section including the central axis is rectangular. The plate portion 56 is connected. The cylindrical portion 55 is cylindrical, and each plate portion 56 is disk-shaped. The outer yoke 54b is connected to both ends of the central core 31 (FIG. 5) in the axial direction so that the inner side surfaces of the two plate portions 56 are in surface contact with each other. As a result, the outer yoke 54b is arranged to face the axial end surface of the central core 31 . In this state, a gap is formed between the inner peripheral surface of cylindrical portion 55 of outer yoke 54b and the outer peripheral surface of stator core 10 (FIG. 5). The outer yoke 54b is made of a magnetic material. For example, for the outer yoke 54b, similarly to the center core 31, a highly insulating powder core such as a dust core or ferrite may be used. The outer yoke 54b may be formed of a laminate of electromagnetic steel sheets.

The outer yoke 54b described above can suppress leakage magnetic flux from the central core 31 to the outside of the induction heating device. A gap may be formed between at least one of the axial end surfaces of the central core 31 and the axial inner surface of the plate portion 56 of the outer yoke 54b. Other configurations and actions in this example are the same as those in FIGS.

In the configuration of FIG. 10, the cylindrical portion of the outer yoke 54b may have a shape other than a cylindrical shape, such as a square cylindrical shape. For example, the outer yoke may be formed by a square tube-shaped cylindrical portion and two square plate portions.

FIG. 11 is a diagram corresponding to FIG. 5 in an induction heating device 30d of another example of the embodiment. In the case of the configuration of this example, in the induction heating device 30 d , the outer reverse polarity coil 50 is arranged on the outer peripheral side of the stator yoke 13 on the outer peripheral side of the stator core 10 . The outer opposite polarity coil 50 is connected to the excitation coil 33 with the number of turns equal to or less than half of the number of turns of the excitation coil 33 . "Reverse polarity" means that the polarities of the two coils are opposite in the axial direction of the induction heating device 30d. The axial direction of the outer peripheral reverse polarity coil 50 coincides with the axial direction of the excitation coil 33 . When the winding directions of the outer circumference side reverse polarity coil 50 and the excitation coil 33 are matched, for example, the winding end of one end side (the lower side in FIG. 11) of the excitation coil 33 (lower side of FIG. 11). In addition, the winding start end of the other end side (upper side in FIG. 11) of the exciting coil 33 is connected to the winding start end of the other end side (upper side in FIG. 11) of the outer reverse polarity coil 50 via the power supply section. . When the winding directions of the outer-side reverse-polarity coil 50 and the exciting coil 33 are reversed, for example, one end side (lower side in FIG. 11) of the exciting coil 33 is connected The winding start end on the other end side (upper side in FIG. 11) is connected to the winding start end on the other end side (upper side in FIG. 11) of the excitation coil 33 via the power supply unit, and the end of the outer peripheral reverse polarity coil 50 is connected to the end of the winding start end. side (lower side in FIG. 11). The outer peripheral side reverse polarity coil 50 is arranged to face the outer peripheral surface of the stator yoke 13 via a cylindrical first heat insulating portion 52 which will be described later. The outer circumference side reverse polarity coil 50 corresponds to an annular current generation source. As will be described later, the outer peripheral reverse polarity coil 50 is configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end face of the stator yoke 13 by the exciting coil 33 .

The cylindrical first heat insulating portion 52 is arranged between the inner peripheral surface of the outer peripheral reverse polarity coil 50 and the outer peripheral surface of the stator core 10 . The cylindrical first heat insulating portion 52 has the same configuration as the second heat insulating portion 42 and has a larger diameter than the second heat insulating portion 42 . Since the cylindrical first heat insulating portion 52 can prevent the outer peripheral side reverse polarity coil 50 from being excessively heated by the radiant heat from the outer peripheral surface of the stator core 10, the outer peripheral side reverse polarity coil 50 can be protected and the outer peripheral side can be prevented. Performance degradation of the reverse polarity coil 50 can be suppressed.

The induction heating device 30d includes an outer-peripheral-side reverse-polarity coil 50 as a ring-shaped current generating source disposed facing the outer peripheral surface of the stator yoke 13 with a first heat insulating portion 52 interposed therebetween. The outer opposite polarity coil 50 is configured to generate magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the stator yoke 13 by the exciting coil 33 . This will be explained using FIG.

FIG. 12 is a diagram corresponding to FIG. 11 for explaining the reason why the abnormal heating of the end face of the stator yoke 13 can be reduced by removing the outer yoke 54 . First, consider a case in which the thickness of the disk-shaped first heat insulating portion 40 is increased assuming that the outer peripheral side reverse polarity coil 50 is not present. In this case, of the solid line arrows α shown in FIG. 12, as indicated by the solid line arrows with X, when the alternating current flows through the exciting coil 33, the magnetic flux due to part of the magnetomotive force of the exciting coil 33 is generated by the stator yoke. It spreads to 13 and flows. Eddy current increases near the axial end face of the stator yoke 13 due to the magnetic flux flowing near the axial end of the stator yoke 13 . Therefore, the axial ends of the stator yoke 13 may be heated excessively and in a concentrated manner.

According to the configuration of this example, an alternating current flows through the outer-peripheral-side opposite-polarity coil 50 by supplying an alternating current to the excitation coil 33 . At this time, for example, a magnetic flux can be generated that flows around the outer-periphery-side reverse-polarity coil 50 in the direction of the dashed-dotted line arrow η in FIG. 12 . Among the magnetic fluxes, the magnetic flux flowing as indicated by the dashed-dotted arrow with X is the direction of the magnetic flux flowing near the axial end of the stator yoke 13 due to the magnetomotive force of the excitation coil 33 (the direction of the solid arrow with X). , the concentrated heating of the axial end portion of the stator yoke 13 due to the magnetic flux can be canceled or mitigated by the magnetic flux due to the current flowing through the reverse polarity coil 50 on the outer peripheral side, and the concentrated heating can be suppressed. At this time, the outer peripheral reverse polarity coil 50 generates magnetic flux in a direction that cancels the magnetic flux generated on the axial end surface of the stator yoke 13 by the exciting coil 33 . As a result, the vicinity of the axial end face of the stator yoke 13 can be prevented from being excessively and intensively heated, so abnormal heating in the stator yoke 13 can be reduced, and over-annealing and deformation of the stator yoke 13 can be suppressed. Other configurations and actions in this example are the same as those in FIGS.

FIG. 13 is a perspective view showing an induction heating device of another example of the embodiment with the outer yoke and the first heat insulating material removed. In the case of the configuration of this example, in the configuration of FIGS. 1 to 6, a hole 61 is formed through the center core 31a in the axial direction. At this time, a coolant pipe (not shown) is connected to the hole 61 . A coolant such as oil or water is supplied to the upstream end of the hole 61 from a discharge port of a coolant pump (not shown) connected to the upstream side of the coolant pipe, and the coolant flows through the hole 61 . Coolant discharged from the downstream end of hole 61 is returned to the inlet of the coolant pump. This cools the central core 31a. Other configurations and actions in this example are the same as those in FIGS.

In the configuration of FIG. 13, a cooling member (not shown) having higher thermal conductivity than the central core 31a may be inserted into the hole 61 instead of circulating the coolant through the hole 61. FIG. For example, the cooling member is rod-shaped. The cooling member is made of, for example, metal with high thermal conductivity such as aluminum alloy. A cooling member may be brought into contact with the inner surface of the hole 61 . The portion of the cooling member protruding from the hole 61 may be connected to a cooling source (not shown) such as a heat sink. Such a configuration can also cool the central core 31a.

14 to 16 show analysis results of the distribution of Joule loss density (W/m ³ ) when the stator core 10 is heated by the induction heating device of the embodiment. FIG. 14 shows the distribution of the Joule loss density in a part of the stator core in the circumferential direction when the thickness of the disk-shaped first heat insulating portion is large (5 mm) when the stator core is heated by the induction heating device of the comparative example. Analysis results are shown. The induction heating device of the comparative example has the same configuration as the induction heating device 30 of the embodiment shown in FIGS. 1 to 6 without the two metal rings 44 . In FIG. 14 , the portion with the lowest Joule loss density in the stator core 10 is indicated by the non-coated portion. The joule loss density increases in the order of the non-coated portion, the sandy portion, the hatched portion, and the slanted lattice portion, and the joule loss density is highest in the black portion.

From the analysis results of FIG. 14, in the case of the comparative example, when the thickness of the disk-shaped first heat insulating portion is increased, the Joule loss density increases near the end face of the stator yoke 13, and the temperature rise is reduced. It was confirmed that they tend to be large. A possible reason for this is that the axial ends of the stator yoke 13 tend to be heated intensively by the magnetic flux generated on the axial end faces of the stator yoke 13 by the excitation coil 33 (see FIG. 5).

On the other hand, FIG. 15 shows a portion of the stator core 10 in the circumferential direction when the stator core 10 is heated by the induction heating device 30 of the embodiment shown in FIG. Fig. 4 shows the analytical results of the distribution of the joule loss density in In FIG. 15, the non-coated portion, the sandy portion, the shaded portion, and the diagonal lattice portion have the same meanings as in FIG.

From the analysis results of FIG. 15, even when the thickness of the first heat insulating portion 40 is increased as in the case of FIG. 14, the Joule loss density near the end surface of the stator yoke 13 is lower than in the case of FIG. 1 to 6, when the induction heating device 30 is provided with the metal ring 44, the magnetic flux generated on the axial end surface of the stator yoke 13 by the excitation coil 33 (see FIG. 5) is , can be canceled or mitigated by the magnetic flux generated by the induced current flowing through the metal ring 44, and it has been confirmed that the concentrated heating of the axial ends of the stator yoke 13 can be suppressed. When the induction heating device was provided with the short-circuited coil 46 or the reverse polarity coil 48 on the end surface side, the analysis results were similar to those shown in FIG.

16 shows the Joule loss in a part of the stator core 10 in the circumferential direction when the thickness of the first heat insulating portion 40 is large (5 mm) when the stator core 10 is heated by the induction heating device 30d shown in FIG. 4 shows analysis results of density distribution. When the induction heating device 30d was provided with the reverse polarity coil 50 on the outer peripheral side as in the configuration of FIG. 11, the results shown in FIG. 16 were obtained. In this case, the Joule loss density was slightly higher than in the case of FIG. 15 at the outer periphery of the stator core 10, but the analysis result was that the Joule loss density was lower than in the case of FIG. Ta.

It should be noted that the outer yoke may be omitted from the induction heating device of each of the above-described embodiments.

Although not shown, a circuit switching section and a control device can be provided in the configuration having the end surface side reverse polarity coil 48 of FIG. 8 or the outer peripheral side reverse polarity coil 50 of FIGS. For example, in a configuration in which the total number of turns of the two end face side reverse polarity coils is larger than the number of turns of the exciting coil 33, the intermediate position of the end face side reverse polarity coils and the exciting coil 33 are reversed in polarity through the circuit switching unit. Connecting. The circuit switching unit is, for example, a relay switch or the like, and is controlled by a control device. The control device connects the circuit switching unit when the stator core temperature is equal to or higher than a predetermined temperature such as 400° C., and disconnects the circuit switching unit when the temperature is lower than the predetermined temperature. When the circuit switching portion is cut off, the two opposite-polarity end-face coils having a total number of turns greater than that of the exciting coil 33 and the exciting coil 33 are connected. By connecting the circuit switching portion, the total number of turns of the portion connected in series to the excitation coil 33 among the two end face side opposite polarity coils is made smaller than the number of turns of the excitation coil 33 .

In addition, the total number of turns of the two end face side reverse polarity coils is less than the number of turns of the excitation coil 33, and the end face side reverse polarity coils and the excitation coil 33 are connected with opposite polarities through the circuit switching section. good too. In this configuration, the control device cuts off the circuit switching unit when the stator core temperature is equal to or higher than a predetermined temperature such as 400° C., and connects the circuit switching unit when the temperature is lower than the predetermined temperature.

Further, in a configuration in which the number of turns of the outer circumference side reverse polarity coil is larger than the number of turns of the excitation coil 33, even if the intermediate position of the outer circumference side opposite polarity coil and the excitation coil 33 are connected with opposite polarities via the circuit switching section. good. The control device connects the circuit switching unit when the stator core temperature is equal to or higher than a predetermined temperature such as 400° C., and disconnects the circuit switching unit when the temperature is lower than the predetermined temperature. When the circuit switching portion is cut off, the outer peripheral reverse polarity coil having a larger number of turns than the exciting coil 33 and the exciting coil 33 are connected. By connecting the circuit switching portion, the number of turns of the portion of the outer peripheral reverse polarity coil connected in series with the excitation coil 33 is made smaller than the number of turns of the excitation coil.

Alternatively, the number of turns of the outer reversed-polarity coil may be smaller than the number of turns of the exciting coil 33, and the reversed-polarity coil on the outer periphery side and the exciting coil 33 may be connected with opposite polarities via a circuit switching unit. In this configuration, the control device cuts off the circuit switching unit when the stator core temperature is equal to or higher than a predetermined temperature such as 400° C., and connects the circuit switching unit when the temperature is lower than the predetermined temperature.

10 rotary electric machine stator core (stator core), 13 stator yoke, 14 tooth, 16 slot, 30, 30a to 30d induction heating device, 31, 31a center core, 33 excitation coil, 40 first heat insulation part, 42 second heat insulation part, 44 Metal ring 46 Short-circuiting coil 48 End face side reverse polarity coil 50 Outer periphery side reverse polarity coil 52 First heat insulating part 54, 54a, 54b Perimeter yoke 55 Cylindrical part 56 Plate part 57 Yoke element 57a, 57b Plate portion 58 First yoke element 59 Second yoke element 59a Plate portion 59b Connection plate portion 61 Hole.

Claims (8)

An induction heating device for a rotating electric machine stator core, comprising: an annular yoke; and a plurality of teeth extending radially inward from a plurality of positions in the circumferential direction of the yoke,
a columnar center core disposed on the inner peripheral side of the rotating electric machine stator core and wound with an exciting coil;
At least one annular current generation source disposed opposite to the axial end face or the outer peripheral face of the yoke on the outer peripheral side of the rotating electric machine stator core via a first heat insulating portion, wherein the exciting coil generates a current in the axial direction of the yoke. at least one current source configured to generate a magnetic flux in a direction that cancels the magnetic flux generated on the end surface;
a second heat insulating portion disposed between the outer peripheral surface of the exciting coil and the rotating electric machine stator core,
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to claim 1,
The at least one current generation source is two current generation sources arranged in a space on both axial end surfaces of the yoke, and is composed of two circumferentially continuous metal rings, or a winding start and a winding end. Two short-circuited coils that are short-circuited, or two end-side reverse polarity coils that are connected so that the polarity is opposite to the excitation coil,
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to claim 2,
The two current sources are the two end-side opposite-polarity coils, the total number of turns of which is less than half the number of turns of the excitation coil, and are connected in opposite polarities to the excitation coil.
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to claim 1,
The at least one current generation source is an outer reverse polarity coil arranged on the outer periphery side of the yoke and connected so as to have a reverse polarity with respect to the excitation coil.
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to claim 4,
The outer-peripheral-side reverse-polarity coil is connected to the excitation coil with a number of turns equal to or less than half the number of turns of the excitation coil,
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to any one of claims 1 to 5,
An outer peripheral yoke formed by including a yoke element having a rectangular cross section, or having two plate portions connected to both ends of a tubular portion so as to block openings at both ends of the tubular portion, covers the central core and arranged opposite the axial end face of the central core,
Induction heating device for rotating electric machine stator core. In the induction heating device for a rotating electric machine stator core according to any one of claims 1 to 6,
A hole is formed through the central core in the axial direction, and a cooling liquid flows through the hole, or a cooling member having higher thermal conductivity than the central core is inserted, thereby the core is cooled,
Induction heating device for rotating electric machine stator core. A method for induction heating the teeth of the rotating electrical machine stator core using the induction heating device for the rotating electrical machine stator core according to any one of claims 1 to 7, comprising:
A magnetic flux generating step of supplying an alternating current to the excitation coil to flow a magnetic flux through the central core and the teeth to anneal the teeth;
An induction heating method for a rotating electric machine stator core.

Images