JP2010155877A - Prepreg sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control an increase of a labor hour required for production of a drive motor for an automobile, and to enhance insulation reliability. <P>SOLUTION: This prepreg sheet is formed so as to have each thermosetting adhesive layer on both surfaces of a self-sheet substrate. The prepreg sheet is so used: that one surface of the thermosetting adhesive layer is adhered to a slot internal wall of a stator core or a rotor core of the drive motor for the automobile; and that another surface of the thermosetting adhesive layer is adhered to a surface of a conductor coil in the slot. In order that a U-shaped segment to form the conductor coil is inserted into one slot in a state where a plurality of segment feet are bound, after the another surface is adhered to the feet by heating, the one surface is adhered to the slot internal wall by heating in a state of bound feet. In the prepreg sheet, a starting temperature of thermoset reaction of a thermosetting resin composition to form the one surface of the thermosetting adhesive layer is higher than a starting temperature of thermoset reaction of a thermosetting resin composition to form the another surface of the thermosetting adhesive layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a prepreg sheet in which a thermosetting adhesive layer is formed on both surfaces of a sheet-like substrate.

With the recent popularization of electric vehicles and hybrid vehicles, the demand for drive motors that serve as power sources for such vehicles is expanding.
Usually, a motor is provided with a stator that is fixedly arranged, and a rotor that is rotatably provided with respect to the stator, and a conductor formed of a winding such as an enameled wire. A coil is provided.

The conductor coil is usually formed by bundling a plurality of windings, and a part of the conductor coil is accommodated in a groove called a slot formed in the stator core or the rotor core.
The slots normally extend along a direction parallel to the rotation axis direction of the motor or generator, and a plurality of slots are formed on the surface of the stator core or the rotor core around the rotation axis at substantially equal intervals.
And the slot is formed in the length over the full length of a stator core or a rotor core, and the opening part is formed in the both end surfaces of a stator core or a rotor core.
For the formation of the stator core and the rotor core, a steel material having a high magnetic permeability is used from the viewpoint of the operation efficiency of the motor and the generator.
Therefore, for example, the winding is surrounded by a sheet-like member such as a slot liner or a wedge in order to prevent damage to the insulating coating of the winding due to contact between the winding and the edge portion of the core end surface. In this state, it is disposed in the slot (see Patent Document 1).

By the way, in recent years, when a motor with a high voltage is formed, a segment formed in a U shape by a rectangular enamel wire is accommodated in a plurality of slots, and then the segments are connected to each other to form a conductor coil. Is formed (see Patent Document 2).
In the manufacture of such a high voltage motor, as shown in Patent Document 2, the leg portion of the segment is inserted from one opening side of the slot, and the tip portion protrudes from the other opening portion. And a method of connecting the protruding leg end portions to each other is employed.
Also in this case, the sheet-like member is arranged along the inner wall surface of the slot in advance, thereby preventing the segment insulation film from being damaged by the core.

JP 2003-111328 A JP 2005-341656 A

The suppression of the decrease in the insulation reliability of the conductor coil due to the contact with the core as described above is required not only when the motor is manufactured but also when it is used.
That is, since the insulation coating such as a winding constituting the conductor coil may be damaged by the core due to vibration caused by the rotation of the motor, the sheet-like member is more reliably interposed between the conductor coil and the core. It is required to be.

However, little attention has been paid to such problems so far, and countermeasures have not been fully studied.
On the other hand, it is possible to prevent contact between the conductor coil and the core by imparting adhesiveness to the sheet-like member and performing adhesion between the conductor coil and the inner wall surface of the core, thereby suppressing a decrease in insulation reliability. Can do.

Further, the conductor coil using the U-shaped segment as described above is formed by inserting a plurality of leg portions of the segment into one slot, and the complicated operation of sequentially inserting the individual segments. It is formed by carrying out.
Moreover, in such a motor, it is not sufficient to suppress damage to the insulating film during operation, and when the segment is inserted, the insulating film of the segment already accommodated in the slot is inserted later. There is a risk of injury by the leg end of the segment.

As described above, a motor in which a conductor coil is formed by using a U-shaped segment as described above can be easily increased in pressure and required to be applied to an automobile drive motor. In addition, it is difficult to improve the insulation reliability.
An object of the present invention is to improve insulation reliability while suppressing an increase in labor required for manufacturing an automobile drive motor.

  The present inventor reduces the labor required for manufacturing a drive motor for an automobile by using a prepreg sheet having a predetermined configuration even in a motor in which a conductor coil is formed using a U-shaped segment. In addition, the inventors have found that the decrease in insulation reliability can be suppressed, and have completed the present invention.

  That is, the present invention is a prepreg sheet in which a thermosetting adhesive layer is formed on both sides of a sheet-like base material in order to solve the above-mentioned problem, and the inner wall surface of a slot of a stator core or rotor core of an automobile drive motor And a thermosetting adhesive layer on one side and a thermosetting adhesive layer on the other side adhered to the surface of the conductor coil in the slot to form the conductor coil. After the other surface side is heat-bonded to the leg portion so as to be inserted into one slot in a state where a plurality of leg-shaped segments are bundled, the one surface side is bound in a state where the leg portions are bundled. The thermosetting reaction start temperature of the thermosetting resin composition forming the thermosetting adhesive layer on one side forms the thermosetting adhesive layer on the other side so that it can be heat-bonded to the inner wall surface of the slot. Of thermosetting resin composition Providing a prepreg sheet characterized by than the curing reaction starting temperature is a high temperature.

According to the prepreg sheet of the present invention, since the thermosetting adhesive layer is formed on both sides of the sheet-like base material, the conductor coil and the stator core, or the conductor coil are utilized using this thermosetting adhesive layer. And at least one of the rotor core can be bonded and fixed, and a decrease in insulation reliability when the motor is used can be suppressed.
Moreover, according to the prepreg sheet of the present invention, the side bonded to the inner wall surface of the slot is bonded to the conductor coil so that a plurality of U-shaped segment legs can be inserted into one slot in a bundled state. The thermosetting adhesive layer is formed with a thermosetting resin composition having a higher thermosetting reaction start temperature than that of the side.
Therefore, for example, even if the heat bonding is performed in a state where the legs are bundled by bringing the side having a low thermosetting reaction start temperature into contact, the outer thermosetting adhesive layer is sufficiently bonded to the inner wall surface of the slot. Adhesiveness can be maintained.
As a result, after the bundle of leg portions is collectively inserted into one slot, heat bonding to the inner wall surface of the slot can be performed.
Therefore, the segment mounting work is simplified, and compared to the conventional method in which the segments are inserted one by one, there is a risk that the insulating film of the previously inserted segment may be damaged by the segment inserted later. Can be suppressed.
That is, according to the present invention, it is possible to improve insulation reliability while suppressing an increase in labor required for manufacturing an automobile drive motor.

According to a preferred embodiment of the present invention, an epoxy resin composition is used for forming any one of the thermosetting adhesive layers, and the epoxy resin composition has a softening point of 70 ° C. or higher. Since it is in the form of a powder containing a resin and a room temperature solid novolac type epoxy resin in a weight ratio of 30:70 to 70:30 and further containing an imidazole-based curing agent, its adhesive property as a prepreg sheet It is possible to make the prepreg sheet heat-curable in a short time while ensuring a period in which can be used effectively.
Therefore, the workability of bonding to the conductor coil and the core can be improved, and the insulation reliability of the automobile drive motor can be improved while suppressing an increase in labor required for manufacturing.

Hereinafter, preferred embodiments of the present invention will be described (based on the accompanying drawings).
First, an automobile drive motor in which the prepreg sheet of this embodiment is used will be described.
FIG. 1 shows a state in which a stator and a rotor of a drive motor with a rotation axis oriented in a vertical direction are viewed from the upper surface side, and is a plane perpendicular to the rotation axis and is higher than the upper end surface of the stator core It shows a state where the upper side is slightly cut.
FIG. 2 is an enlarged view of the area surrounded by the broken line indicated by the symbol “A” in FIG. 1, and the area surrounded by the broken line indicated by the sign “B” is enlarged. An enlarged view is also shown in the figure.

As shown in FIGS. 1 and 2, a rotary shaft 10 having an elongated cylindrical shape is disposed at the center of the drive motor, and a rotor core is provided around the outer periphery of the rotary shaft 10.
The rotor core 20 is formed in a substantially cylindrical shape having a through-hole through which the rotary shaft 10 is inserted from the upper end side to the lower end side, and the rotary shaft 10 and the rotor core 20 are fixed and integrated. The drive motor is provided so as to be rotatable around the rotary shaft 10.

The drive motor of the present embodiment is provided with a stator core 30 surrounding the rotor core around the rotary shaft 10, and the stator core 30 is a four-layer segment sequential joining stator coil (see FIG. (Not shown) is mounted as a conductor coil and fixed in the drive motor.
The stator core 30 is formed in an overall substantially cylindrical shape having an inner diameter slightly larger than the outer diameter of the rotor core 20, and a slight gap is formed between the cylindrical inner peripheral surface and the outer peripheral surface of the rotor core 20. The rotor core 20 is accommodated in the hollow region so that it is disposed in the drive motor.

A plurality of slots 31 are formed on the inner peripheral surface side of the stator core 30, and the plurality of slots 31 extend in the extending direction (vertical direction) of the rotary shaft 10, and Adjacent slots 31 are arranged substantially parallel to each other.
A plurality of linear openings 31 a having a length from the upper end side to the lower end side of the stator core 30 (the entire length of the data core 30) are arranged substantially parallel to each other on the inner peripheral surface side of the stator core 30. Is formed.
The slot 31 is formed so as to penetrate the stator core 30 in the length direction (vertical direction), and an opening 31 b having the same shape as the cross-sectional shape of the slot 31 is formed on the upper end surface side of the stator core 30. An opening having the same shape is also formed on the lower end surface side.
Further, the depth of the slots 31 from the inner peripheral surface of the stator core 30 toward the outer peripheral side is substantially the same depth in all the slots 31.

The stator core 30 is formed with the slots such that the slots are plate-shaped.
In other words, the plate-like teeth 32 are formed between the slots, and a plurality of the teeth 32 are formed in a state of projecting toward the inner peripheral surface side (the direction of the rotating shaft 10) of the stator core 30.
The teeth 32 have a wide portion 32a formed wider at the tip end in the protruding direction than the other portions, and a cross section of a plane perpendicular to the extending direction of the slot 31 (the extending direction of the rotary shaft 10) is formed. It has a shape that is substantially T-shaped.
The formation of the rotor core 20 and the stator core 30 is not particularly limited. For example, a laminated body in which electromagnetic steel plates are laminated in the axial direction of the rotary shaft 10 can be used.

Four slots 40 of U-shaped segments are accommodated in the slots 31 of the stator core 30 respectively. The segments include a rectangular conductor 41 and an insulating coating 42 formed on the surface thereof by enamel varnish. It is constituted by.
The U-shaped segment has its U-shaped head positioned on the upper end side of the stator core 30, and its legs are inserted from the opening 31b on the upper end side of the stator core 30 so as to protrude from the opening on the lower end side. In this embodiment, by connecting the tip end of the protruding leg to the tip of the leg protruding from another slot, a plurality of teeth 32 are connected from the upper end side to the lower end side and the lower end of the stator core 30. A continuous conductor is formed so as to sew from the side to the upper end side.
That is, in the stator formed by the stator core 30 and a plurality of segments, the coil end formed by the head portion of the segment is arranged on the upper end side, and the coil end formed by the connecting portion between the leg portions is on the lower end side. It has been arranged.
Each slot 31 accommodates a total of four legs in a line from the inside outward.

A slot liner 51 is arranged so as to surround and bundle the four legs around the entire circumference, and the prepreg sheet according to the present embodiment is used for the slot liner 51.
The slot liner 51 is arranged along the inner wall surface 31c of the slot 31, the outer surface thereof is adhered to the inner wall surface 31c of the slot 31, and the inner surface is attached to the outer peripheral surface (insulating coating 42) of the segment leg portion. Glued.
That is, the conductor coil formed by the segment and the stator core 30 are bonded and fixed by the slot liner 51.

The slot liner 51 has adhesive layers 51b ₁ and 51b ₂ on both sides of a sheet-like base material 51a which is the center in the thickness direction, and an adhesive layer 51b ₁ (hereinafter referred to as the conductor coil side) on the inner surface side (conductor coil side). Both the “first adhesive layer 51b ₁ ” and the outer surface side (slot inner wall surface side) adhesive layer 51b ₂ (hereinafter also referred to as “second adhesive layer 51b ₂ ”) are epoxy resins. It is formed with the thermosetting adhesive in which the composition was used.

When the slot liner 51 is in the state of a prepreg sheet before being bonded to both the conductor coil and the stator core 30, the first adhesive layer 51b in the B stage state is formed on both surfaces of the sheet-like substrate 51a. _1, in which the second adhesive layer 51b ₂ (thermosetting adhesive layer) was provided.

The thicknesses of the first adhesive layer 51b ₁ and the second adhesive layer 51b ₂ in this prepreg sheet are appropriately changed depending on the size of the automobile drive motor used, etc., but usually 5 μm to 500 μm, respectively. It is set as the thickness of either.

In the present embodiment, the thermosetting adhesive used for forming the first adhesive layer 51b ₁ in the prepreg sheet and the thermosetting adhesive used for forming the second adhesive layer 51b ₂ are: The reaction start temperature of the curing reaction is varied.
In addition, at least one contains a bisphenol type epoxy resin having a softening point of 70 ° C. or higher and a novolac type epoxy resin that is solid at room temperature in a weight ratio of 30:70 to 70:30, and further, imidazole-based curing It is preferable that it is an epoxy resin composition containing the agent.

Either the first adhesive layer 51b ₁ or the second adhesive layer 51b ₂ is formed of such an epoxy resin composition, so that heat generation and vibration during the operation of an automobile drive motor, and adhesion of oils As a result, the slot liner 51 is hardly deteriorated and has excellent adhesion durability.
Accordingly, it is possible to suppress the possibility that the conductor coil and the stator core 30 are not adhered to each other and fall off from between them, and the effect of preventing damage to the insulating coating 42 of the segment can be maintained for a long time. it can.
Moreover, by using the composition as described above, it is possible to form a thermosetting adhesive layer excellent in the reactivity of the thermosetting reaction at the time of bonding, and to the conductor coil and the stator core (the inner wall surface 31c of the slot). Adhesive workability can be improved.

  In addition, the bisphenol type epoxy resin having a softening point of 70 ° C. or higher and the novolac type epoxy resin which is solid at room temperature are included in a weight ratio of 30:70 to 70:30, and further, an imidazole curing agent is further included. The epoxy resin composition is preferably powdery in the formation of the thermosetting adhesive layer of the prepreg sheet.

Thus, by making an epoxy resin composition into a powder form, a hardening reaction advances until a prepreg sheet is used as the slot liner 51, and adhesiveness falls, or adhesiveness is not exhibited at all. It is possible to prevent troubles such as such a situation.
That is, even if a poxy resin and an imidazole-based curing agent are contained as described above, these are once dispersed in an organic solvent to form a varnish, applied to the sheet-like substrate 51a and dried to form a prepreg sheet. When produced, the degree of progress of the curing reaction during storage is greater than when a powdery epoxy resin composition is used.
Therefore, in such a case, the period in which the slot liner 51 can be used is shortened.

The material and form of the sheet-like substrate 51a used for the prepreg sheet are not particularly limited. For example, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, aliphatic polyamide, aromatic polyamide, polyimide, polyamide Resin films such as imide, polyether sulfide, polyvinyl chloride, polyketone, and polytetrafluoroethylene, and films, nonwoven fabrics, or woven fabric sheets using resin fibers may be employed.
In addition, for example, a nonwoven fabric or woven fabric sheet using cellulose, cotton, wool, rock wool, glass fiber, carbon fiber, or the like may be employed.
In addition, the thickness of the sheet-like base material 51a is not particularly limited, and can usually be any thickness of 5 μm to 500 μm.

Examples of the bisphenol type epoxy resin having a softening point of 70 ° C. or higher contained in the epoxy resin composition include a bisphenol A type epoxy resin having a softening point of 70 ° C. or higher, and a bisphenol F type having a softening point of 70 ° C. or higher. Epoxy resins, and further, for example, those obtained by modifying CTBN.
Especially, in order to make the coexistence of the reactivity in a thermosetting reaction and suppression of the reaction at the time of storage more reliable, it is preferable that a softening point is any one of 95-130 degreeC.
Similarly, a bisphenol A type epoxy resin having an epoxy equivalent of any one of 900 to 2500 g / eq, which has not been modified such as CTBN modification, is suitable.
In addition, this epoxy equivalent can be calculated | required based on JISK7236. The softening point can be measured by the ring and ball method of JIS K 7234.

Examples of the novolac epoxy resin that is solid at room temperature (23 ° C.) contained in the epoxy resin composition include a cresol novolac epoxy resin and a phenol novolac epoxy resin.
Especially, in order to make the reactivity in the thermosetting reaction and the suppression of the reaction during storage more reliable, an o-cresol novolac type epoxy resin having any softening point of 70 to 90 ° C. Is preferred.

  In the epoxy resin composition, the content of the bisphenol-type epoxy resin having a softening point of 70 ° C. or higher and the novolac-type epoxy resin solid at room temperature is set to any weight ratio of 30:70 to 70:30. However, if the weight ratio is out of this range, it will not have enough heat resistance to be used in a drive motor for automobiles, or the reactivity and storage during thermosetting reaction (adhesion) This is because it becomes difficult to maintain a balance with the reactivity of time.

  Examples of the imidazole curing agent contained in the epoxy resin composition include alkyl imidazoles such as 1-methylimidazole, 2-methylimidazole, 2-undecylimidazole, and 2-heptadecylimidazole; 1,2-dimethyl Dialkylimidazoles such as imidazole and 2-ethyl-4-methylimidazole; aryl imidazoles such as 2-phenylimidazole; 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazolium tri Retite, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]- Ethyl-s-triazine, 2,4-diamino-6- (2'-undecylimidazolyl) -ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4-methylimidazolyl- (1 ')]-Ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine-isocyanuric acid adduct, 2-phenylimidazole-isocyanuric acid addition , 2-methylimidazole / isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl 4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4,5-di (2-cyano-ethoxy) can be used methylimidazole.

  Among them, as the imidazole curing agent, those having a reaction start temperature exceeding 110 ° C. are preferable, and those having a reaction start temperature exceeding the softening point of the bisphenol type epoxy resin or novolak type epoxy resin. Preferably, specifically, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct or 1-cyanoethyl-2-phenylimidazole Preference is given to lithium trimellitate.

  In addition, this reaction start temperature is an epoxy resin composition in which 20 parts by mass of a curing agent is uniformly mixed with 100 parts by mass of a liquid bisphenol A type epoxy resin (for example, “Epicoat 828” manufactured by Japan Epoxy Resin Co., Ltd.). The product can be defined by the DSC measuring the change in the amount of heat generated by heating at 10 ° C./min.

  The imidazole-based curing agent may be contained in the epoxy resin composition at a ratio of 2 to 5 parts by weight with respect to 100 parts by weight of the total amount of the bisphenol type epoxy resin and the novolac type epoxy resin. preferable.

In addition, since the epoxy resin composition is used for forming a thermosetting adhesive layer in a powder form, for example, the epoxy resin composition itself is put into a powder state by preventing aggregation of the epoxy resin powders. In order to maintain, inorganic particles can be further contained.
Examples of the inorganic particles include aluminum hydroxide, magnesium hydroxide, calcium carbonate, talc, wollastonite, alumina, silica, unfired clay, fired clay, and barium sulfate.

  Furthermore, the epoxy resin composition can appropriately contain a coloring component such as a pigment, a functional agent such as a flame retardant, and the like.

In the present embodiment, the prepreg sheet will be described by taking as an example the case where the first adhesive layer 51b ₁ and the second adhesive layer 51b ₂ are both thermosetting adhesive layers using an epoxy resin composition. However, if necessary, it is possible to use the epoxy resin composition as described above on one side and to form the other side with a thermosetting adhesive resin composition other than the epoxy resin composition. The resin composition for forming the other is not particularly limited.

However, in order to more reliably fix the conductor coil and the stator core 30, it is possible to form both the first adhesive layer 51b ₁ and the second adhesive layer 51b ₂ with the epoxy resin composition. preferable.
In addition, either the first adhesive layer 51b ₁ or the second adhesive layer 51b ₂ or both may have a multilayer structure.
For example, the first adhesive layer 51b ₁ may have a laminated structure of two layers or three or more layers formed of epoxy resin compositions having different compositions.

In addition, it is preferable that surface adhesiveness is provided to the 1st adhesive bond layer 51b ₁ side, ie, the side adhere | attached on a conductor coil.
On the other hand, the second adhesive layer 51b ₂ side, that is, the side bonded to the stator core 30 (the inner wall surface 31c of the slot) is preferably non-tacky. For example, the second adhesive layer The 51b ₂ side is preferably formed so as not to exhibit tackiness at room temperature.

By adopting such a configuration, for example, when inserting a segment into the stator core 30, the four leg portions accommodated in the individual slots 31 by the prepreg sheet having surface adhesiveness are the same as in the accommodated state. , And a state in which all the U-shaped segments have been installed in the slots 31 (a form of the conductor coil before connecting the leg tips) is prepared in advance, and an assembly of the segments is formed at a time at the stator core 30. Can be attached.
Therefore, the operation can be simplified as compared with the case where the individual segments are sequentially inserted into the slots, and the use of such a prepreg sheet can reduce the labor required for manufacturing the automobile drive motor.
At this time, since the second adhesive layer 51b ₂ side is non-tacky, the sliding with the inner wall surface 31c of the slot 31 is also good, and the workability in the manufacture of the automobile drive motor is further improved. .

As a method of imparting surface tackiness to the first adhesive layer 51b ₁ side, a method of providing a pressure-sensitive adhesive layer on the surface side of the first adhesive layer 51b ₁ to form two or more layers, Examples of the adhesive layer 51b ₁ include a method in which a tackifier is blended with an epoxy resin composition to be formed while having a single layer structure to exhibit surface tackiness.
The pressure-sensitive adhesive layer formed on the surface of the thermosetting adhesive layer can be formed to a thickness of, for example, 10 μm to 50 μm using a pressure-sensitive adhesive.
Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives and rubber-based pressure-sensitive adhesives.
In addition, an epoxy resin composition different from the thermosetting adhesive forming the thermosetting adhesive layer serving as a base can also be used as the adhesive. In this case, an epoxy resin composition containing a tackifier or the like can be used.

  In this case, if a large amount of pressure-sensitive adhesive is interposed between the thermosetting adhesive layer and the surface of the segment (insulating coating 42) after thermosetting, the epoxy forming the thermosetting adhesive layer Since it may be difficult to make the excellent heat resistance of the resin composition sufficiently effective to improve the reliability of the drive motor, the thermosetting adhesive layer and the surface of the segment are more reliably secured during thermosetting. It is preferable to form the pressure-sensitive adhesive layer thin so as to be bonded.

In addition, it is difficult to maintain the shape for a long time in a state where all the U-shaped segments have been attached to the slot 31 only by the surface adhesiveness applied to the first adhesive layer 51b ₁ side. Therefore, after bundling the four legs with a prepreg sheet, it is important to heat the prepreg sheet so that the thermosetting adhesive layer adheres to the surface of the segment. is there.

In this case, since the second adhesive layer 51b ₂ side is also heated, the reaction start temperature of the thermosetting reaction in the second adhesive layer 51b ₂ is higher than that in the first adhesive layer 51b _1. High epoxy resin composition is used.
The difference in the reaction start temperature of the thermosetting reaction in the epoxy resin composition constituting the first adhesive layer 51b ₁ and the second adhesive layer 51b ₂ is preferably set to 20 ° C. or more, and 30 ° C. More preferably, the reaction start temperatures are set apart from each other.

The comparison of the reaction start temperature between the epoxy resin composition of the first adhesive layer 51b _{1 and} the epoxy resin composition of the second adhesive layer 51b ₂ should be performed in the same manner as the measurement of the reaction temperature of the imidazole curing agent. Can do.
That is, the measuring changes in curing calorific value at heating rate conditions of the epoxy resin compositions used for forming the first adhesive layer 51b ₁ 10 ° C. / min DSC, second adhesive layer 51b ₂ The epoxy resin composition used for forming the epoxy resin composition is subjected to DSC measurement under the same conditions, and the epoxy resin composition having a low reaction start temperature depending on which of the epoxy resin compositions the temperature at which the chart leaves the baseline is observed to be low Can be determined.

Thus, by adopting an epoxy resin composition having a reaction initiation temperature higher than that of the first adhesive layer 51b ₁ for the formation of the second adhesive layer 51b ₂ , the first adhesive layer is formed before the segment is mounted on the stator core 30. only can be thermoset side 51b _1, it is possible to perform the binding of the segment in the prepreg sheet more firmly by heat curing.
Therefore, it becomes easy to handle the assembly of segments, and the work of mounting this assembly on the stator core 30 becomes easy.
That is, the workability in the manufacture of the automobile drive motor can be further improved.

The second adhesive layer 51b ₂ in the prepreg sheet has sufficient heat for the epoxy resin composition that forms the second adhesive layer 51b ₂ after the leg portions of the segments are accommodated in the slots 31 of the stator core 30. The entire surface can be bonded to the inner wall surface 31 c of the slot 31 by heating the whole to a temperature sufficient to cause a curing reaction.

  In this way, the conductor coil and the stator core 30 are bonded together using the prepreg sheet, so that the segment insulating coating 42 is more reliably protected not only at the time of manufacture but also at the time of use. Can be improved.

Next, a method for producing the prepreg sheet will be described.
First, a bisphenol-type epoxy resin having a softening point of 70 ° C. or higher and a novolak-type epoxy resin that is solid at room temperature are blended in a weight ratio of 30:70 to 70:30, and further an imidazole-based curing agent is added. Then, a powdery epoxy resin composition is prepared by pulverizing and mixing a composition in which inorganic particles are appropriately blended as necessary.
The first pulverization step for pulverizing the compounding agent excluding the imidazole-based curing agent, and the multi-step process in which the imidazole-based curing agent is added to the resin powder obtained in the first pulverization step to perform the second pulverization step It is also possible to produce a powdery epoxy resin composition through the above process.
By carrying out such a multi-stage pulverization process, it is possible to prevent the epoxy resin curing reaction from proceeding due to frictional heat generated during the pulverization.

The average particle size of the epoxy resin composition powder produced at this time is usually 1000 μm or less. The thickness is preferably 0.1 μm to 500 μm, and more preferably 0.1 to 200 μm.
In this way, by reducing the average particle size of the epoxy resin composition powder, the surface area is reduced, and even dispersion of particles having different specific gravities such as inorganic particles is facilitated, and the epoxy resin and The number of contact points with the imidazole curing agent can be increased, and the reactivity during the curing reaction can be increased.

Such an epoxy resin composition powder can be produced using, for example, a Henschel mixer, a planetary mixer, a ball mill, a jet mill, a hammer mill, or the like.
The obtained epoxy resin composition powder may be classified by passing it through a mesh or the like.

  The obtained epoxy resin composition powder is spread, for example, by allowing a long strip-like sheet-like base material to run at a constant speed in the horizontal direction, and depositing so that the deposition amount per unit area is constant on the upper surface side. Then, a thermosetting adhesive layer can be formed by fixing this powdery epoxy resin composition to a sheet-like substrate.

  As a method for depositing the epoxy resin composition powder on the sheet-like substrate, an electrostatic coating method, a spray coating method, or the like can be employed.

  Then, with the epoxy resin composition powder deposited, the sheet-like substrate is passed through a heating furnace maintained at a predetermined temperature, or added from above with a heating roll subjected to surface release treatment. The epoxy resin composition powder can be softened by pressing or the like to be fixed to the sheet-like substrate.

After that, a thermosetting adhesive having a low reaction initiation temperature of the thermosetting reaction, such as using an imidazole-based curing agent having a low reaction initiation temperature on the opposite side of the thermosetting adhesive layer formed on one side in this way. The prepreg sheet can be obtained by forming an adhesive layer.
Although it is possible to first form a thermosetting adhesive layer with a low reaction initiation temperature of the thermosetting reaction, the first thermosetting adhesive layer produced later is the other thermosetting adhesive layer. Since it receives heat again when forming the adhesive layer, it is preferable to first form a thermosetting adhesive layer having a high reaction initiation temperature.

In this embodiment, when the effect of the present invention can be exhibited more remarkably, it is used as a slot liner by being wound around the leg portion of a four-layer segment sequentially joined stator coil using a flat enameled wire. However, the present invention is not limited to the above examples.
For example, the prepreg sheet of this embodiment can also be used when a conductor coil is attached to the rotor core.

The composition used for the prepreg sheet of the present invention was examined.
(Preparation of prepreg sheet)
(Formulations 1-8)
Using the following ingredients, a powdery epoxy resin composition was prepared so as to have the composition shown in Table 1.
(Combination agent)
(Epoxy resin component)
A1: manufactured by Japan Epoxy Resin (JER), bisphenol A type epoxy resin, trade name “1004” (softening point: 97 ° C., epoxy equivalent: 925 g / eq)
A2: manufactured by JER, bisphenol A type epoxy resin, trade name “1007”,
(Softening point: 128 ° C., epoxy equivalent: 2000 g / eq)
A3: Made by Printec, CTBN-modified bisphenol A type epoxy resin,
Product name “SR35K”, (softening point: 98 ° C., epoxy equivalent: 975 g / eq)
N1: manufactured by Toto Kasei Co., Ltd., o-cresol novolac type epoxy resin,
Product name “YDCN703” (softening point: 80 ° C., epoxy equivalent: 208 g / eq)
B1: manufactured by JER, biphenyl type epoxy resin, trade name “YX4000”,
(Softening point: 105 ° C., epoxy equivalent: 186 g / eq)
(Curing agent component)
M1: manufactured by Shikoku Kasei Co., Ltd., trade name “2MA-OK” (2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct),
Reaction start temperature: 120 ° C
M2: manufactured by Shikoku Kasei Co., Ltd., trade name “2PZCNS-PW” (1-cyanoethyl-2-phenylimidazolium trimellitate), reaction start temperature: 120 ° C.
M3: manufactured by Shikoku Kasei Co., Ltd., trade name “C11Z-CNS” (1-cyanoethyl-2-undecyl imidazolium trimellitate), reaction start temperature: 105 ° C.
D1: 4,4′-diaminodiphenyl sulfone, reaction start temperature: 110 ° C.
(Inorganic particles)
S1: Nippon Aerosil Co., Ltd., fumed silica, trade name “AEROSIL 300”

(Preparation of powdered epoxy resin composition)
Of the above blends, only the resin component was pulverized with a hammer mill (rotation speed: 3000 rpm, filter diameter: φ1 mm), and then classified with 42 mesh, so that the fraction under the sieve and the curing agent were in the ratio shown in Table 1 above. The mixture was further mixed and ground with a super mixer (processing time: 90 seconds, filter 40 mesh) to prepare an epoxy resin composition powder.

(Preparation of prepreg sheet)
After the obtained powdery epoxy resin composition was applied to one side of a sheet-like base material (meta-aramid fiber sheet, manufactured by DuPont Teijin Advanced Paper, Nomex paper, thickness: 50 μm) using a gravure roller, 150 Passing through the heating furnace at 5 ° C. at a speed of 5 m / min (furnace residence time: 30 seconds), the powder epoxy resin composition was fixed on the other side as well.
The obtained sheet is passed between rollers heated to 160 ° C. with the release sheet sandwiched between them at a speed of 5 m / min to carry out a surface smoothing treatment, on both sides of a sheet-like substrate having a thickness of 50 μm. Then, a thermosetting adhesive layer having a thickness of 25 μm was formed to produce a prepreg sheet having a total thickness of 100 μm.
However, about the prepreg sheet | seat of the mixing | blending 6, the mixing | blending of the said Table 1 was disperse | distributed in the mixed solvent of methyl ethyl ketone and toluene, and a liquid epoxy resin composition (epoxy resin varnish) was produced, and a sheet-like base material ( Meta-aramid fiber sheet, DuPont Teijin Advanced Paper Co., Nomex Paper, thickness: 50 μm) on both sides, the epoxy resin varnish is applied and dried so that the thickness after drying is 25 μm, and thermosetting adhesive Layers were formed.

(Evaluation)
(Preservability of prepreg sheet)
Two test pieces obtained by cutting the prepared prepreg sheet into 100 mm × 100 mm were stacked and flowed outward from the initial shape (100 mm × 100 mm) when heat press cured at 125 ° C. × 30 minutes × 5 kg / cm ² . Measure the amount of resin. The result was determined as “◯” when the value after storage for 30 days at room temperature (23 ° C.) with respect to the initial value was 50% or more, and “X” when the value was less than 50%.
The results are shown in Table 2.

(Shear bond strength)
First, the prepared prepreg sheet was cut into 10 mm × 10 mm to prepare square test pieces.
Next, a steel plate having a thickness of 1.5 mm, a width of 10 mm, and a length of 100 mm was prepared, and a test piece was placed in a state where three sides of the square were aligned on one edge of the steel plate.
Furthermore, another steel plate (thickness 1.5 mm, width 10 mm, length 100 mm) is prepared, and the edge of this other steel plate is attached to the remaining square side of the test piece placed on the previous steel plate. They were placed in an aligned state, and arranged so that the previous steel plate and this other steel plate were in a substantially straight line with a part of them overlapped.
Then, the portion where the three-layer structure of this steel plate / test piece / steel plate is formed is sandwiched and fixed by a clip (“No. 54” manufactured by LION Co., Ltd.) and subjected to heat bonding at 125 ° C. for 90 minutes. A 190 mm tensile sample was prepared.
This sample was subjected to a tensile tester to measure the maximum value of the tensile stress necessary to separate the two steel plates and to determine the shear adhesive strength of the prepreg sheet. And the case where the shear adhesive force was 340N or more was determined as "(circle)", and the case below 340N was determined as "x".
The results are shown in Table 2.

(Heat resistance evaluation)
In order to simulate and evaluate the heat resistance required for automobile drive motors, dielectric breakdown voltage and shear bond strength were evaluated using each prepreg sheet.
(Evaluation of oil resistance breakdown voltage)
A dielectric breakdown test was performed on an evaluation sample obtained by thermosetting each prepreg sheet under curing conditions of 125 ° C. × 90 minutes, and a dielectric breakdown voltage was measured.
In addition, the same measurement was performed after immersing the evaluation sample in automould (ATF) heated to 150 ° C. for 1000 hours. The dielectric breakdown voltage after immersion in ATF was 50% of the initial dielectric breakdown voltage. Those showing the above values were judged as “◯”, and those less than 50% were judged as “x”.
The results are shown in Table 2.

(Oil-resistant adhesive strength)
Further, after the evaluation sample was immersed in automould (ATF) heated to 150 ° C. for 1000 hours, the same measurement was performed, and the shear adhesive strength after ATF immersion was 50% with respect to the initial shear adhesive strength. Those showing the above values were judged as “◯”, and those less than 50% were judged as “x”.
The results are shown in Table 2.

Also from this table, in the present invention, the epoxy resin composition used for forming the thermosetting adhesive layer comprises a bisphenol type epoxy resin having a softening point of 70 ° C. or higher and a novolac type epoxy resin that is solid at room temperature. 30:70 to 70:30 in a weight ratio, and further in the form of a powder containing an imidazole-based curing agent, the powdery epoxy resin composition being fixed to the sheet-like base material and the heat It can be seen that the formation of the curable adhesive layer can make the prepreg sheet excellent in adhesion workability while prolonging the usable period of the prepreg sheet.

And since the above-mentioned prepreg sheet can maintain excellent adhesive strength for a long period of time, the adhesion state between the conductor coil and the inner wall surface of the core can be secured for a long period of time, and contact between the conductor coil and the core can be prevented. A decrease in insulation reliability can be suppressed.
In the evaluation of the above prepreg sheet, the thermosetting adhesive layers on both sides of the base sheet have the same composition, but the thermosetting adhesive layers were further changed with different thermosetting reaction temperatures. By forming on each surface of the material sheet, it is possible to improve the workability of segment mounting.

The schematic sectional drawing which looked at the stator and rotor of a drive motor from the upper surface side. The enlarged view which expanded the area | region shown with the symbol "A" of FIG. 1, and the partial enlarged view.

Explanation of symbols

10: Rotating shaft, 20: Rotor core, 30: Stator core, 31: Slot, 31a: Opening part, 31b: Opening part, 31c: Inner wall surface, 32: Teeth, 32a: Wide part, 40: Leg part of segment, 41: Flat conductor, 42: insulation coating, 51: slot liner, 51a: sheet-like substrate, 51b ₁ , 51b ₂ : adhesive layer (thermosetting adhesive layer)

Claims (6)

A prepreg sheet in which a thermosetting adhesive layer is formed on both sides of a sheet-like substrate,
A thermosetting adhesive layer on one side is bonded to the inner wall surface of a slot of a stator core or a rotor core of an automobile drive motor, and a thermosetting adhesive layer on the other side is bonded to the surface of a conductor coil in the slot. After the other surface side is heated and bonded to the leg portion so that the U-shaped segment for forming the conductor coil is inserted into one slot in a state where a plurality of the leg portions are bundled, The thermosetting reaction start temperature of the thermosetting resin composition that forms the thermosetting adhesive layer on one side is such that the one side can be heated and bonded to the inner wall surface of the slot in a state where the legs are bundled. A prepreg sheet having a temperature higher than a thermosetting reaction start temperature of a thermosetting resin composition forming a surface-side thermosetting adhesive layer.   An epoxy resin composition is used for forming the thermosetting adhesive layer on the one surface side or the other surface side, and the epoxy resin composition includes a bisphenol type epoxy resin having a softening point of 70 ° C. or more and And a novolac type epoxy resin that is solid at room temperature in a weight ratio of 30:70 to 70:30, and further in the form of a powder containing an imidazole curing agent, the powdery epoxy resin composition is The prepreg sheet according to claim 1, wherein the thermosetting adhesive layer is fixed to a sheet-like substrate.   The prepreg sheet according to claim 2, wherein the bisphenol type epoxy resin is a bisphenol A type epoxy resin having an epoxy equivalent of any one of 900 to 2500 g / eq.   As the imidazole curing agent, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine / isocyanuric acid adduct or 1-cyanoethyl-2-phenylimidazole The prepreg sheet according to claim 2 or 3, wherein any one of lithium trimellitates is used.   In the epoxy resin composition, the imidazole curing agent is contained in any proportion of 2 to 5 parts by weight with respect to 100 parts by weight of the total amount of the bisphenol type epoxy resin and the novolac type epoxy resin. The prepreg sheet according to any one of claims 2 to 4.   The prepreg sheet according to any one of claims 2 to 5, wherein the epoxy resin composition further contains inorganic particles.

Images