Rotary electric motor stator with thermally expanding layered slot liner

In an expansion sheet for a rotary electric machine that has a thermal expansion property and is to be arranged between a core and a coil conductor in a slot in the rotary electric machine, in which the coil conductor is housed in the slot formed in the core, the expansion sheet has a first surface and a second surface and includes: a first surface-side portion; and a second surface-side portion that is closer to the second surface than the first surface-side portion. An amount of volume increase, caused by heating, of the first surface-side portion is higher than an amount of volume increase, caused by the heating, of the second surface-side portion.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2012-107327 filed on May 9, 2012 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an expansion sheet for a rotary electric machine, a stator for a rotary electric machine using an expansion sheet for a rotary electric machine, and a manufacturing method of a stator for a rotary electric machine.

2. Description of Related Art

A vehicle such as a hybrid vehicle or an electric vehicle is typically provided with a rotary electric machine capable of functioning as both a motor and a generator. The rotary electric machine typically includes a stator, and a rotor that rotates with respect to the stator, with a predetermined gap created therebetween. The stator includes a stator core, and a plurality of coil conductors that are wound around the stator core.

When the rotary electric machine functions as a motor, direct current (DC) power from a power supply such as a secondary battery or a fuel cell is stepped up to a desired voltage using a step-up converter as necessary, and converted to a polyphase alternating current (AC) power by an inverter. The resultant current then flows through the coil conductors that are wound around the stator, causing the rotor to rotate. On the other hand, when the rotary electric machine functions as a generator, rotation of the rotor causes current to flow through the coil conductors that are wound around the stator. The power obtained at this time is charged to the secondary battery or the like as regenerative power, or is supplied to electronic equipment such as auxiliary equipment, and consumed as driving power.

Slots are formed in the stator core of the stator for the rotary electric machine. The coil conductors are housed in these slots. At this time, an insulating layer for insulation needs to be formed between the inner peripheral surface of each slot and the corresponding coil conductor. One example of a method for providing this insulating layer in the slot is a method using an insulating sheet.

Japanese Patent Application Publication No. 59-117435 (JP 59-117435 A) relates to a high-voltage coil of a rotary electric machine, and describes housing, in a groove of an iron core, a coil conductor that is wound surrounded by a slot liner having a conductive foam layer on both sides of graphite paper.

Japanese Utility Model Application Publication No. 01-166780 (JP 01-166780 U) relates to a rotary electric machine for a compressor, and describes installing insulating paper having a trilaminar structure in which surface layers of different thicknesses are formed on both sides, such that the thin surface layer is on a coil side and the thick surface layer is on an iron core side.

Japanese Patent Application Publication No. 61-277347 (JP 61-277347 A) relates to motor insulating paper of a compressor, and describes slot insulating paper in which first insulating paper material that is extremely strong mechanically is laminated to second insulating paper material that is heat resistant.

Japanese Patent Application Publication No. 2002-262500 (JP 2002-262500 A) describes a rotary electric machine in which a stator coil is supported by a bimetal in which a plurality of sheets of material having different coefficients of thermal expansion are laminated together.

Japanese Patent Application Publication No. 2010-259316 (JP 2010-259316 A) relates to a stator for a rotary electric machine, and recites that, in an adhesive sheet that has a trilaminar structure formed by an adhesive layer that is laminated to each side of an insulating layer, and resin that forms the adhesive layer may have expandability.

SUMMARY OF THE INVENTION

The invention provides an expansion sheet for a rotary electric machine, with which it is made possible to improve the fixedness of a coil conductor in a slot, a stator for a rotary electric machine using an expansion sheet for a rotary electric machine, and a manufacturing method of a stator for a rotary electric machine.

A first aspect of the invention is an expansion sheet for a rotary electric machine that has a thermal expansion property and that is to be arranged between a core and a coil conductor in a slot in the rotary electric machine, in which the coil conductor is housed in the slot formed in the core, the expansion sheet having a first surface and a second surface and including: a first surface-side portion; and a second surface-side portion that is closer to the second surface than the first surface-side portion, wherein an amount of volume increase, caused by heating, of the first surface-side portion is higher than an amount of volume increase, caused by the heating, of the second surface-side portion.

A second aspect of the invention is a stator for a rotary electric machine that includes: a stator core in which a slot is formed; a coil conductor that is housed in the slot; and the expansion sheet according to the first aspect of the invention that is arranged between the stator core and the core conductor with the first surface facing the coil conductor and with the second surface facing the stator core, wherein the coil conductor is fixed to the stator core by the expansion sheet.

A third aspect of the invention is a manufacturing method of a stator for a rotary electric machine that includes: inserting the expansion sheet according to the first aspect of the invention into a slot in a stator core with the second surface facing the stator core; tentatively adhering, to an inner wall surface of the slot, the second surface of the expansion sheet that has been inserted into the slot; housing the coil conductor in the slot; and adhering an outer peripheral surface of the coil conductor to the first surface of the expansion sheet, and adhering the inner wall surface of the slot to the second surface of the expansion sheet, by expanding and curing the expansion sheet by heating the expansion sheet.

A fourth aspect of the invention is a manufacturing method of a stator for a rotary electric machine that includes: limiting expansion of an edge portion of the expansion sheet according to the first aspect of the invention by laser processing the edge portion of the expansion sheet, and then inserting the expansion sheet into the slot of the stator core with the second surface facing the stator core; tentatively adhering, to an inner wall surface of the slot, the second surface of the expansion sheet that has been inserted into the slot; housing the coil conductor in the slot; and adhering an outer peripheral surface of the coil conductor to the first surface of the expansion sheet, and adhering the inner wall surface of the slot to the second surface of the expansion sheet, by expanding and curing the expansion sheet by heating the expansion sheet.

According to the invention, a gap between a coil conductor housed in a slot and a slot inner wall surface is eliminated or reduced, so that the fixedness of the coil conductor in the slot is improved.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings. In the drawings, like structures will be denoted by like reference characters, and descriptions of those structures are omitted or simplified in some cases.

(Expansion Sheet for a Rotary Electric Machine)

FIG. 1is a partial perspective view of an example of a stator core for a rotary electric machine when an insulating sheet for a rotary electric machine or an expansion sheet for a rotary electric machine and a coil conductor, that will be described later, are not arranged between teeth viewed from an end surface10A of the stator core. As shown inFIG. 1, a stator core10has a plurality of teeth12including teeth12a,12b, that are formed so as to protrude radially inward, and a plurality of slots14including slots14a,14b, . . . that are formed between adjacent teeth.

FIG. 2Ais a partial sectional view of a comparative example of a stator for a rotary electric machine (hereinafter simply referred to as “stator”) to which an insulating sheet for a rotary electric machine (hereinafter simply referred to as “insulating sheet”) and a coil conductor are attached. In a stator120illustrated inFIG. 2A, an insulating sheet116is inserted into each slot14of the stator core. Also, a coil conductor18is attached via the insulating sheet116to the outer periphery of the teeth12.

Here, when conductive material referred to as a so-called rectangular wire or flat wire, which has a generally rectangular sectional shape, is used as the coil conductor18shown inFIG. 2A, a stepped gap22in which the interval is uneven is formed between an inner wall surface14A of the slot14and the coil conductor18, as shown inFIG. 3. In this way, with the insulating sheet116shown inFIG. 2A, a case may arise in which it may be difficult to appropriately fill the gap in which the end surface shape largely differs between the coil conductor18side and the inner wall surface14A side of the slot14. Therefore, as shown inFIG. 2B, by using an expansion sheet for a rotary electric machine (hereinafter, simply referred to as “expansion sheet”)16of embodiments of the invention instead of the insulating sheet116shown inFIG. 2A, the gap formed between the inner wall surface of the slot14and the coil conductor18is eliminated or reduced.

FIG. 4is a sectional view schematically showing a structure of the expansion sheet of a first embodiment of the invention. As shown inFIG. 4, an expansion sheet16aincludes: a stator core-side expansion layer30athat contains a first epoxy resin composition32athat expands when heated; a coil conductor-side expansion layer40athat contains a second epoxy resin composition42athat expands by a higher volume increase amount than the stator core-side expansion layer30awhen heated; and an insulating film50that is arranged between the stator core-side expansion layer30aand the coil conductor-side expansion layer40a, and contains insulating material52. The expansion sheet16ais arranged such that one surface of the stator core-side expansion layer30acontacts one surface of the insulating film50, and one surface of the coil conductor-side expansion layer40acontacts the other surface of the insulating film50. Note that in all embodiments described herein, the surface of the expansion sheet on the coil conductor side corresponds to the first surface of the invention and the surface of the expansion sheet on the stator core side corresponds to the second surface of the invention, the portion of the expansion sheet adjacent the first surface corresponds to the first layer portion, the portion of the expansion sheet adjacent the second surface corresponds to the second layer portion, the coil conductor-side expansion layer corresponds to the first expansion layer, the stator core-side expansion layer corresponds to the second expansion layer.

The insulating film50has a property of ensuring rigidity and insulation from the earth, and functions as the base material of the expansion sheet16a. Meanwhile, both the stator core-side expansion layer30aand the coil conductor-side expansion layer40aexpand when heated, and function as joining material that joins to both the stator core10and the coil conductor18to immobilize the coil conductor18. When the expansion sheet16a, in which the coil conductor-side expansion layer40ais formed using an epoxy resin composition that expands by a higher volume increase amount than the stator core-side expansion layer30awhen heated is used, the coil conductor-side expansion layer40a, in particular, of the expansion sheet16aexpands when heated, and spreads throughout the gap formed between the inner wall surface14A of the slot14and the coil conductor18. As a result, the stator core10is joined to the stator core-side expansion layer30a, and the coil conductor18(or more specifically, a coating, not shown, that covers an outer peripheral surface of the coil conductor18) is joined to the coil conductor-side expansion layer40a, such that the coil conductor18is appropriately immobilized (seeFIGS. 4 and 5).

FIG. 6is a sectional view schematically showing a structure of an expansion sheet according to a second embodiment of the invention. As shown inFIG. 6, an expansion sheet16bincludes: a stator core-side expansion layer30bthat contains an epoxy resin composition32bthat expands when heated; a coil conductor-side expansion layer40bthat contains an epoxy resin composition42bwhich expands when heated, and that is thicker than the stator core-side expansion layer30b; and an insulating film50that is arranged between the stator core-side expansion layer30band the coil conductor-side expansion layer40b, and contains insulating material52. The expansion sheet16bis arranged such that one surface of the stator core-side expansion layer30bcontacts one surface of the insulating film50, and one surface of the coil conductor-side expansion layer40bcontacts the other surface of the insulating film50.

InFIG. 6, when the expansion sheet16expands by being heated, the epoxy resin compositions32band42bcontained in the expansion sheet16bmay be the same or different from each other, as long as the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40bis larger than that of the stator core-side expansion layer30b. In particular, having the epoxy resin compositions32band42bbe the same is advantageous in terms of procuring the material. The stator core is joined to the stator core-side expansion layer30b, and the coil conductor is joined to the coil conductor-side expansion layer40b, by heating the expansion sheet16b. At this time, the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40bis larger than that of the stator core-side expansion layer30b, so that the expanded coil conductor-side expansion layer40bspreads throughout the gap formed on the coil conductor side, thus appropriately immobilizing the coil conductor.

FIG. 7is a sectional view schematically showing the structure of an expansion sheet according to a third embodiment of the invention. As shown inFIG. 7, an expansion sheet16cincludes: a stator core-side expansion layer30cthat contains an epoxy resin composition32cthat expands when heated; a coil conductor-side expansion layer40cthat contains an epoxy resin composition42cwhich expands when heated, and that expands by a higher volume increase amount than the stator core-side expansion layer30cwhen heated; an insulating film50that is arranged between the stator core-side expansion layer30cand the coil conductor-side expansion layer40c, and contains insulating material52; a stator core-side joining layer35athat is arranged on the outer side of the stator core-side expansion layer30cand contains joining material37a; and a coil conductor-side joining layer45athat is arranged on the outer side of the coil conductor-side expansion layer40cand contains joining material47a. The expansion sheet16cis arranged such that one surface of the stator core-side joining layer35acontacts one surface of the stator core-side expansion layer30c, one surface of the insulating film50contacts the other surface of the stator core-side expansion layer30c, one surface of the coil conductor-side expansion layer40ccontacts the other surface of the insulating film50, and one surface of the coil conductor-side joining layer45acontacts the other surface of the coil conductor-side expansion layer40c. Note that in all embodiments described herein, the coil conductor-side joining layer corresponds to the first joining layer and the stator core-side joining layer corresponds to the second joining layer.

InFIG. 7, the epoxy resin compositions32cand the42ccontained in the expansion sheet16bmay be the same or they may be different from each other, as long as the coil conductor-side expansion layer40cexpands by a higher volume increase amount than the stator core-side expansion layer30cwhen heated. That is, combinations of the coil conductor-side expansion layer and the stator core-side expansion layer such as those illustrated inFIGS. 4 and 6may be applied. Meanwhile, the stator core-side joining layer35aand the coil conductor-side joining layer45aare both made of resin material that has excellent joining performance with respect to the stator core and the coil conductor, respectively, and also has suitable flexibility so as to be able to change shape with the expansion of the corresponding resin layers. At this time, the coil conductor-side expansion layer40cexpands by a higher volume increase amount than the stator core-side expansion layer30cwhen heated, so that the expanded coil conductor-side expansion layer40cand the coil conductor-side joining layer45aspread throughout the gap formed on the coil conductor side, thus appropriately immobilizing the coil conductor.

FIG. 8is a sectional view schematically showing a structure of an expansion sheet of a fourth embodiment of the invention. As shown inFIG. 8, an expansion sheet16dincludes a stator core-side expansion layer30dthat contains an epoxy resin composition32dthat expands when heated, and a coil conductor-side expansion layer40dthat contains an epoxy resin composition42dwhich expands when heated, and that expands by a higher volume increase amount than the stator core-side expansion layer30dwhen heated. The expansion sheet16dis arranged such that one surface of the stator core-side expansion layer30dcontacts one surface of the coil conductor-side expansion layer40d.

InFIG. 8, the epoxy resin compositions32dand42dcontained in the expansion sheet16dmay be the same or they may be different from each other, as long as the coil conductor-side expansion layer40dexpands by a higher volume increase amount than the stator core-side expansion layer30dwhen heated. That is, combinations of the coil conductor-side expansion layer and the stator core-side expansion layer such as those illustrated inFIGS. 4 and 6may be applied. At this time, the coil conductor-side expansion layer40dexpands by a higher volume increase amount than the stator core-side expansion layer30dwhen heated, so that the expanded coil conductor-side expansion layer40dspreads throughout the gap formed on the coil conductor side, thus appropriately immobilizing the coil conductor. In the fourth embodiment, a member corresponding to the insulating film50of the expansion sheets16ato16cof the first to third embodiments illustrated inFIGS. 4, 6, and 7is not provided. Therefore, the structure is preferably one in which insulating material such as an epoxy resin composition, for example, for imparting the appropriate insulation is used in at least one of the stator core-side expansion layer30dand the coil conductor-side expansion layer40d, and impregnated into a felt-like sheet base material.

FIG. 9is a sectional view schematically showing a structure of an expansion sheet according to a fifth embodiment of the invention. As shown inFIG. 9, an expansion sheet16econtains an epoxy resin composition38ethat expands when heated. The expansion sheet16eis configured such that the amount of volume increase caused by heating increases gradually from a stator core-side end surface66atoward a coil conductor-side end surface66b. The expansion sheet may be configured such that the amount of volume increase caused by heating increases stepwise from a stator core-side end surface toward a coil conductor-side end surface.

InFIG. 9, when the expansion sheet16eexpands by being heated, the type of component contained in the epoxy resin composition38emay be the same throughout in the thickness direction of the expansion sheet16e, may change gradually, or may change stepwise, as long as the amount of volume increase, caused by heating, on the coil conductor-side end surface66bside is larger than that on the stator core-side end surface66aside. At this time, the coil conductor-side end surface66bside expands by a higher volume increase amount than the stator core-side end surface66awhen heated, so that the expansion sheet16espreads throughout the gap formed on the coil conductor side, thus appropriately immobilizing the coil conductor. In the fifth embodiment, the expansion sheet16emay contain insulating material for imparting the appropriate insulation, similar to the expansion sheet16dof the fourth embodiment shown inFIG. 8.

FIG. 10is a sectional view schematically showing a structure of an expansion sheet according to a sixth embodiment of the invention. As shown inFIG. 10, an expansion sheet16fincludes: a stator core-side expansion layer30fthat contains an epoxy resin composition32fthat expands when heated; a coil conductor-side expansion layer40fthat contains an epoxy resin composition42f, and that expands by a higher volume increase amount than the stator core-side expansion layer30fwhen heated; and an insulating film50that is arranged between the stator core-side expansion layer30fand the coil conductor-side expansion layer40f, and contains insulating material52. The expansion sheet16fis arranged such that one surface of the stator core-side expansion layer30fcontacts one surface of the insulating film50, and one surface of the coil conductor-side expansion layer40fcontacts the other surface of the insulating film50.

The expansion sheet16fshown inFIG. 10has a structure similar to those of the expansion sheets16aand16bof the first and second embodiments shown inFIGS. 4 and 6, except that the amount of volume increase, caused by heating, of edge portions402and406of the coil conductor-side expansion layer40fis lower than that of a center portion404that is sandwiched between the edge portions402and406. The edge portions402and406are provided at an outer periphery of the center portion404. In this case, “the amount of volume increase is lower than that of the center portion” means that an epoxy resin composition that expands at a lower volume increase amount than the center portion404is used in the edge portions402and406. As a modification of the sixth embodiment, the structure may be such that at least a portion of the insulating film50is exposed by not forming the coil conductor-side expansion layer40fin locations corresponding to the edge portions402and406. According to the sixth embodiment, it is possible to manufacture a rotary electric machine having the desired performance, in which excess resin is inhibited from protruding out to the coil conductor side as it expands by being heated, when the expansion sheet16fis applied to the inner wall surface of the slot. The sixth embodiment describes a structure that reduces the amount of volume increase, caused by heating, of the edge portions402and406of the coil conductor-side expansion layer40fthat correspond to two sides of the expansion sheet16fthat are arranged along the axial direction of the rotary electric machine when the expansion sheet16fis applied to the inner wall surface of the slot. Alternatively, however, the structure may be one that reduces the amount of volume increase, caused by heating, of edge portions of the coil conductor-side expansion layer40fthat correspond to two sides of the expansion sheet16fthat are arranged at both axial end surfaces (seeFIG. 1) of the stator core, or one that reduces the volume increase amount for both the edge portions402and406of the coil conductor-side expansion layer40fthat correspond to two sides of the expansion sheet16fthat are arranged along the axial direction of the rotary electric machine when the expansion sheet16fis applied to the inner wall surface of the slot, and the edge portions of the coil conductor-side expansion layer40fthat correspond to two sides of the expansion sheet16fthat are arranged at both axial end surfaces (seeFIG. 1) of the stator core.

FIG. 11is a sectional view schematically showing a structure of an expansion sheet according to a seventh embodiment of the invention. As shown inFIG. 11, an expansion sheet16gincludes: a stator core-side expansion layer30gthat contains an epoxy resin composition32gthat expands when heated; a coil conductor-side expansion layer40gthat contains an epoxy resin composition42g, and that expands by a higher volume increase amount than the stator core-side expansion layer30gwhen heated; and an insulating film50that is arranged between the stator core-side expansion layer30gand the coil conductor-side expansion layer40g, and contains insulating material52. The expansion sheet16gis arranged such that one surface of the stator core-side expansion layer30gcontacts one surface of the insulating film50, and one surface of the coil conductor-side expansion layer40gcontacts the other surface of the insulating film50.

InFIG. 11, the expansion sheet16ghas a structure similar to those of the expansion sheets16aand16bof the first and second embodiments shown inFIGS. 4 and 6, except that the amount of volume increase, caused by heating, of the stator core-side expansion layer30gand the coil conductor-side expansion layer40gis lower than that of a center portion414due to the fact that edge portions412and416of the expansion sheet16gare cut by heat treatment such as laser cutting or the like, for example. According to the seventh embodiment, it is possible to manufacture a rotary electric machine having the desired performance, in which excess resin is inhibited from protruding out to the coil conductor side as it expands by being heated, when the expansion sheet16gis applied to the inner wall surface of the slot.

As a modification of the seventh embodiment, heat treatment such as laser cutting may be performed on edge portions corresponding to two sides of the expansion sheet16gthat are arranged at both axial end surfaces of the stator core, or heat treatment such as laser cutting may be performed on both the edge portions412and416of the expansion sheet16g, and the edge portions corresponding to the two sides of the expansion sheet16gthat are arranged at both axial end surfaces of the stator core. Also, a volume increase amount reduction process illustrated inFIG. 10may be performed on one or some of the edge portions that include the four sides of the expansion sheet16, and heat treatment such as laser cutting may be performed on the remaining edge portion(s).

Next, the compositions of the expansion sheet16ato16gdescribed above will be described in detail.

The epoxy resin compositions32a,32b,32c,32d,32f,32g,38e,42a,42b,42c,42d,42f, and42gof the first to seventh embodiments typically contain an epoxy resin and an expansion filler having a thermal expansion property. The expansion filler thermally expands and the stator core side of the expansion sheet increases in volume, which makes it possible to adhere the coil conductor to the inner wall surface of the slot without any gaps. The thermal expansion property in the invention refers to the property of expanding beyond the thermal expansion normally displayed by an ordinary substance. Some examples of material having such a thermal expansion property are given below.

The expansion filler of the first to seventh embodiments can be classified into two types, i.e., an inorganic or organic chemical expansion agent, and a microcapsule physical expansion agent. The inorganic or organic chemical expansion agent expands through gasification by thermal decomposition. Also, there are various types of these two types of expansion agents, and they are manufactured by a variety of methods. For example, taking into account the effect on the hardenability (i.e., curability) and physical property of resin, and the uniformity of expansion and the like, a thermally expandable microcapsule, which is one of microcapsule physical expansion agents, is preferable because it has few trade-offs. Also, a thermally expandable microcapsule that is one of microcapsule physical expansion agents is a microcapsule in which a low-boiling point substance in liquid form is encapsulated by a polymer shell made of a thermoplastic polymer. This thermally expandable microcapsule gasifies near the softening temperature of the polymer shell, or at a temperature equal to or higher than that temperature, and in doing so, thermally expands.

For the expansion filler of the first to seventh embodiments, a thermally expandable microcapsule in which liquid carbon dioxide gas is sealed inside a polymer shell made of a thermoplastic polymer, for example, is used. When the volume expansion becomes equal to or greater than five times this thermally expandable microcapsule, the relative permittivity becomes equal to or less than 1.4, so that reduction of permittivity of the expansion sheet is promoted, and the gap between the inner wall surface of the slot and the coil conductor is reduced by the volume expansion of the expansion sheet.

Some examples of an epoxy resin that may be applied to the stator core-side expansion layers30ato30d,30f, and30gof the first to fourth, sixth, and seventh embodiments are, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, and novolac-type epoxy resin, but the epoxy resin is not limited to these. One or a plurality of types of epoxy resins may be used together with a curing agent or a hardening accelerator as necessary, and applied.

As an epoxy resin applied to the coil conductor-side expansion layers40ato40d,40f, and40gof the first to fourth, sixth, and seventh embodiments, an epoxy resin similar to that which is applied to the stator core-side expansion layers30ato30d,30f, and30gmay be applied. The type of epoxy resin that is applied to the stator core-side expansion layer and the coil conductor-side expansion layer at this time may be the same or different from each other.

The epoxy resin applied to the expansion sheet16eof the fifth embodiment may be manufactured by applying the plurality of epoxy resins applied to the stator core-side expansion layers30ato30d,30f, and30g, and the coil conductor-side expansion layers40ato40d,40f, and40g, in an appropriate combination, and/or making the amount of the expansion filler different in a gradual manner.

In the stator core-side expansion layers30ato30d,30f, and30gin the first to fourth, sixth, and seventh embodiments, at least 1 but less than 3 parts by mass of the expansion filler is mixed with 100 parts by mass of the applied epoxy resin. If the amount of expansion filler is equal to or greater than 3 parts by mass, it may become extraneous material. If the amount of expansion filler is less than 1 part by mass, the effect of filling the gap between the stator core and the expansion sheet may not be sufficiently exhibited.

In the coil conductor-side expansion layers40ato40d,40f, and40gof the first to fourth, sixth, and seventh embodiments, at least 3 but no more than 7 parts by mass of the expansion filler is mixed with 100 parts by mass of the applied epoxy resin. If the amount of expansion filler is greater than 7 parts by mass, it may become extraneous material. If the amount of expansion filler is less than 3 part by mass, the effect of filling the gap between the coil conductor and the expansion sheet may not be sufficiently exhibited.

The thickness of the expansion sheets16ato16gof the first to seventh embodiments is equal to or less than 350 μm, and preferably between 300 μm and 340 μm, inclusive. If the thickness of the expansion sheets16ato16gexceeds 350 μm, the space factor of the coil conductor inside the slot will not improve. On the other hand, if the thickness of the expansion sheets16ato16gis less than 300 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The thickness of the stator core-side expansion layers30a,30b,30f, and30gof the first, second, sixth, and seventh embodiments is equal to or less than 125 μm, and preferably between 100 μm and 120 μm, inclusive. If the thickness of the stator core-side expansion layers30a,30b,30f, and30gexceeds 125 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the thickness of the stator core-side expansion layers30a,30b,30f, and30gis less than 100 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The sum of the thickness of the stator core-side expansion layer30cand that of the stator core-side joining layer35ain the third embodiment is equal to or less than 125 μm, and preferably between 100 μm and 120 μm, inclusive. If the sum of the thickness of the stator core-side expansion layer30cand that of the stator core-side joining layer35aexceeds 125 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the sum of the thickness of the stator core-side expansion layer30cand that of the stator core-side joining layer35ais less than 100 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The thickness of the stator core-side expansion layer30din the fourth embodiment is equal to or less than 175 μm, and preferably between 150 μm and 170 μm, inclusive. If the thickness of the stator core-side expansion layer30dexceeds 175 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the thickness of the stator core-side expansion layer30dis less than 150 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The thickness of the coil conductor-side expansion layers40a,40b,40f, and40gin the first, second, sixth, and seventh embodiments is equal to or less than 125 μm, and preferably between 100 μm and 120 μm, inclusive. If the thickness of the coil conductor-side expansion layers40a,40b,40f, and40gexceeds 125 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the thickness of the coil conductor-side expansion layers40a,40b,40f, and40gis less than 100 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The sum of the thickness of the coil conductor-side expansion layer40cand that of the coil conductor-side joining layer45ain the third embodiment is equal to or less than 125 μm, and preferably between 100 μm and 120 μm, inclusive. If the sum of the thickness of the coil conductor-side expansion layer40cand the coil conductor-side joining layer45aexceeds 125 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the sum of the thickness of the coil conductor-side expansion layer40cand the coil conductor-side joining layer45ais less than 100 μm, the gap may not be filled and sufficient adhesive force may not be generated.

The thickness of the coil conductor-side expansion layer40din the fourth embodiment is equal to or less than 175 μm, and preferably between 150 μm and 170 μm, inclusive. If the thickness of the coil conductor-side expansion layer40dexceeds 175 μm, the space factor of the coil conductor in the slot will not improve. On the other hand, if the thickness of the coil conductor-side expansion layer40dis less than 150 μm, the gap may not be filled and sufficient adhesive force may not be generated.

For the insulating material52that forms the insulating film50of the first to third, sixth, and seventh embodiments, a polyethylene naphthalate film, a polyimide film, or a polyetherimide film or the like may be used, for example. The thickness of the insulating film50of the first to third, sixth, and seventh embodiments is equal to or less than 100 μm, and preferably between 50 μm and 100 μm, inclusive. If the thickness of the insulating film50exceeds 100 μm, the resin thickness of the expansion layer may end up decreasing. On the other hand, if the thickness of the insulating film50is less than 50 μm, the electrical insulation may be unsatisfactory.

In the expansion sheets16a,16f, and16gof the first, sixth, and seventh embodiments, the amounts of volume increase, caused by heating, of the stator core-side expansion layers30a,30f, and30gare preferably between 0 μm and 100 μm, inclusive. If the amounts of volume increase, caused by heating, of the stator core-side expansion layers30a,30f, and30gexceed 100 μm, they may become extraneous material. On the other hand, the amounts of volume increase, caused by heating, of the coil conductor-side expansion layers40a,40f, and40gare higher than the amounts of volume increase, caused by heating, of the corresponding stator core-side expansion layers30a,30f, and30g, respectively, and preferably equal to or greater than 590 μm. If the amounts of volume increase, caused by heating, of the coil conductor-side expansion layers40a,40f, and40gare less than 590 μm, the gap may not be filled and sufficient adhesive force may not be generated. However, this does not apply to the edge portions402,406,412, and416, as described above.

In the expansion sheet16bof the second embodiment, the amount of volume increase, caused by heating, of the stator core-side expansion layer30bis preferably between 0 μm and 100 μm, inclusive. If the amount of volume increase, caused by heating, of the stator core-side expansion layer30bexceeds 100 μm, it may become extraneous material. On the other hand, the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40bis higher than the amount of volume increase, caused by heating, of the stator core-side expansion layer30b, and preferably equal to or greater than 590 μm. If the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40bis less than 590 μm, the gap may not be filled and sufficient adhesive force may not be generated.

In the expansion sheet16cof the third embodiment, the amount of volume increase, caused by heating, of the stator core-side expansion layer30cis preferably between 0 μm and 100 μm, inclusive. If the amount of volume increase, caused by heating, of the stator core-side expansion layer30cexceeds 100 μm, it may become extraneous material. On the other hand, the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40cis higher than the amount of volume increase, caused by heating, of the stator core-side expansion layer30c, and preferably equal to or greater than 590 μm. If the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40cis less than 590 μm, the gap may not be filled and sufficient adhesive force may not be generated.

In the expansion sheet16dof the fourth embodiment, the amount of volume increase, caused by heating, of the stator core-side expansion layer30dis preferably between 0 μm and 100 μm, inclusive. If the amount of volume increase, caused by heating, of the stator core-side expansion layer30dexceeds 100 μm, it may become extraneous material. On the other hand, the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40dis higher than the amount of volume increase, caused by heating, of the stator core-side expansion layer30d, and preferably equal to or greater than 590 μm. If the amount of volume increase, caused by heating, of the coil conductor-side expansion layer40dis less than 590 μm, the gap may not be filled and sufficient adhesive force may not be generated.

In the expansion sheet16eof the fifth embodiment, the amount of volume increase, caused by heating, of the coil conductor-side end surface66bside is adjusted to gradually become higher than the amount of volume increase, caused by heating, of the stator core-side end surface66aside. At this time, the expansion sheet16eis manufactured such that the amount of volume increase, caused by heating, of the stator core-side end surface66aside corresponds to a range of one of the amounts of volume increase, caused by heating, of the stator core-side expansion layers30a,30b,30c,30d,30f, and30g, and the amount of volume increase, caused by heating, of the coil conductor-side end surface66bside corresponds to a range of one of the coil conductor-side expansion layers40a,40b,40c,40d,40f, and40g.

For the manufacturing method of the expansion sheets16ato16g, in the case of the expansion sheet16ashown inFIG. 4, for example, the stator core-side expansion layer30a, the insulating film50, and the coil conductor-side expansion layer40amay each be manufactured separately, and then be adhered or joined together with a suitable adhesive or the like. Also, as another embodiment, the expansion sheet16amay be formed by applying or impregnating the epoxy resin composition32athat contains epoxy resin and expansion filler to or into one surface of the insulating film50, and applying or impregnating the epoxy resin composition42athat contains epoxy resin and expansion filler to or into the other surface of the insulating film50, and then drying them as necessary. However, the manufacturing method of the expansion sheets16ato16gis not limited to these.

In the embodiments described above, the expansion sheets16ato16gthat have what is called a cuff-less shape that enables them to be inserted into the slot with the shape matched with that of the inner wall surface of the slot by bending as necessary are described. However, an expansion sheet16hprovided with cuff portions70aand70blike those illustrated inFIG. 12, that facilitate fixing the stator core into the slot may also be applied. InFIG. 12, as the expansion sheet16h, an expansion sheet having a structure similar to that of the expansion sheets16ato16gdescribed above, except for the cuff portions70aand70b, may be applied. Also, with regard to the cuff portions70aand70b, expansion performance is not necessary, so that the expansion ratio reduction process illustrated inFIG. 10or an expansion reduction process with heat treatment, for example, may be performed. The edge portions422and426and the center portion424shown inFIG. 12correspond to the edge portions402and406and the center portion404shown inFIG. 10, and the edge portions412and416and the center portion414shown inFIG. 11, respectively.

(Stator for a Rotary Electric Machine)

An embodiment of a stator for a rotary electric machine according to the invention includes: a stator core10provided with the slots14; the coil conductor18housed inside the slots14; and the expansion sheet16arranged between the stator core10and the coil conductor18, as shown inFIGS. 2B and 5. The expansion sheet16is one of the expansion sheets16ato16hdescribed above, and appropriately fixes the coil conductor18to the stator core10.

With the stator20of this embodiment having the structure described above, the gap between the coil conductor housed in the slot and the slot inner wall surface is eliminated or reduced, thus improving the fixedness of the coil conductor inside the slot, as compared with the case where an insulating sheet or an expansion sheet not having the structure described above is applied.

(Manufacturing Method of the Stator for a Rotary Electric Machine)

An embodiment of a manufacturing method of the motor stator according to the invention will hereinafter be described with reference toFIGS. 2B and 13.

First, a laser processing is performed on an edge portion of an expansion sheet16that is one of the expansion sheets16ato16hdescribed above (S90). The laser processing limits an expansion of the edge portion of the expansion sheet Next the expansion16is inserted into the slot14(S100). The expansion sheet16may be bent into the slot shape in advance such that the stator, core-side surface of the expansion sheet16contacts the inner wall surface of the slot14at this time.

Next, the stator core-side surface of the expansion sheet16that is inserted into the slot14is tentatively adhered to the inner wall surface of the slot14(S102). The method for this tentative adhering is not particularly limited. For example, the expansion sheet may be tentatively adhered to the stator core by softening the expansion sheet by applying heat of a temperature (such as 90° C. or lower) that will not expand the expansion layer and will not generate adhesive force.

Next, the coil conductor18is housed in the slot14(S104). The method for housing the coil conductor18may be any known method for forming what is called a concentrated winding. Also, when flat wire is applied, for example, the winding may be edgewise winding or flatwise winding.

Next, the expansion sheet16is expanded and cured (S106). Because the expansion sheet16is tentatively adhered to the inner wall surface of the slot14, the distance between the inner wall surface of the slot14and the stator core10side surface of the expansion sheet16is narrow. Therefore, the stator core10side surface of the expansion sheet16can easily be adhered to the inner wall surface of the slot14by heating the expansion sheet16. On the other hand, the distance between the outer peripheral surface of the coil conductor18and the coil conductor18side surface of the expansion sheet16is greater than the distance between the inner wall surface of the slot14and the stator core10side surface of the expansion sheet16. Therefore, the gap between the inner wall surface of the slot14and the coil conductor18is eliminated or reduced, thus improving the fixedness of the coil conductor18within the slot14, by applying the expansion sheet16ato16hin which the coil conductor18side has a higher expansion ratio than the stator core10side as described above. In the embodiment of the invention, the suitable temperature for expanding and curing the expansion sheet16differs depending on the composition and the like of the applied epoxy resin composition. For example, the temperature may be approximately 150° C. to 220° C. If the temperature for expanding and curing the expansion sheet is less than 150° C., sufficient curing characteristics may not be obtained.

As long as the application of the invention is related to the manufacturing of a rotary electric machine in which a coil conductor is housed in a slot formed in a core, the invention is effective not only for the application with a stator core, but for various other applications as well, such as a rotor core, for example.

The coil conductor side may also have a sheet center portion, and a coil conductor-side expansion layer that is formed by a sheet edge portion that is provided on an outside of the sheet center portion and expands by a lower volume increase amount than the sheet center portion.

The coil conductor side may also have a sheet center portion that expands by a higher volume increase amount than the core side, and a coil conductor-side layer that is formed by a sheet edge portion that is provided on an outside of the sheet center portion and does not have the thermal expansion property.