JP4557509B2 - Epoxy adhesive composition for electric power steering apparatus, adhesive structure, and electric power steering apparatus - Google Patents

Description

【００３５】
上記の表中、ＤＧＥＢＡは油化シェル（株）社製のビスフェノールＡ型エポキシ樹脂であり、
エピコート８０７は油化シェル（株）社製のビスフェノールＦ型エポキシ樹脂であり、
ＴＧＤＤＭは東都化成（株）社製のテトラグリシジルジアミノジフェニルメタン（ＹＨ４３４）であり、
ＦＸ６０２は日本合成ゴム（株）（ＪＳＲ）社製のカルボキシル基含有架橋ニトリルブチルゴム（ＮＢＲ）からなるゴム成分であり、ガラス転移温度（Ｔｇ）は約−５０℃であり、
ＡＣ３３５５はガンツ化成（株）社製のアクリルコアシェルポリマーからなるゴム成分であり、コア成分のＴｇは約−２０℃であり、
ＣＧ１４００はエアプロダクツ（株）社製のジシアンジアミドであり、
ＤＣＭＵはアルドリッチ（株）社製の３−（３，４−ジクロロフェニル）−１，１−ジメチルウレアであり、
アルミニウム金属粉は東洋アルミニウム（株）社製のＡＣ２５００であり、
アルミナ粉は昭和電工（株）社製のＡＳ−１０であり、
Ａ２００はアエロジル（株）社製のシリカ粉である。
【００３６】
以下の条件で、２枚のアルミニウム試験片どうしを接合する接着剤のせん断接着強さを測定し、そしてネオジム磁石と鉄試験片との間を接合する接着剤のせん断接着強さ及び耐熱衝撃性を測定した。
１．アルミニウム試験片（Ａｌ）の接合におけるせん断接着強さ
試験片サイズ：１．６ｍｍ×２５ｍｍ×１００ｍｍ
接着面積：１２．５ｍｍ×２５ｍｍ
接着剤層の厚さ：０．１ｍｍ
硬化条件：１４０℃で３０分間
引張速度：５ｍｍ／分
表面処理：クロム酸混液（ＦＰＬ）エッチング
２．ネオジム磁石（Ｎｄ）と鉄試験片（Ｆｅ）との接合におけるせん断強さ及び耐熱衝撃性試験
試験片サイズ：Ｎｄ磁石７．６５ｍｍ×４．８３ｍｍ×４５．５ｍｍ、ＦｅＳＣ４５Ｃ：３．２ｍｍ×２５ｍｍ×１００ｍｍ
接着面積：８ｍｍ×３５ｍｍ
接着剤層の厚さ：０．１ｍｍ
硬化条件：１４０℃で３０分間
引張速度：５ｍｍ／分
表面処理：メチルエチルケトン（ＭＥＫ）脱脂
冷熱サイクル：−４０℃から１２０℃
【００３７】
【表２】

【００３８】
上記の表２から、本発明の接着剤組成物では１０００サイクルの冷熱サイクル後にも優れた耐熱衝撃性を有することが確認された。
【００３９】
【発明の効果】
本発明の１液型エポキシ系接着剤組成物は、広い温度域において高い接着強さを有し、かつ冷熱サイクル後にも優れた接着強さを有する。
また、本発明のエポキシ系接着剤組成物を用いて永久磁石とモータシャフトとを接着すると、強固でかつ耐冷熱サイクル性が優れた接着構造体を得ることができるので、永久磁石とモータシャフトとの間の固定に機械的固定を併用する必要がなくなる。このため、モータの構成を簡素化でき、かつモータを小型化できることから、電動パワーステアリング装置全体を小型化できる。
【図面の簡単な説明】
【図１】電動パワーステアリング装置の部分分解図を示している。
【図２】図１の電動パワーステアリング装置の拡大図を示している。
【符号の説明】
１１…電動パワーステアリング装置
１２…第１ラックハウジング
１３…第２ラックハウジング
１４…モータハウジング
１６…ラックシャフト
１８…モータシャフト
２０…第２ベアリング（軸受）
２１…第１ベアリング（軸受）
２６…ボールねじナット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a one-pack type epoxy adhesive composition suitable for bonding a permanent magnet (for example, a neodymium magnet) and a metal part in the manufacture of an electric power steering device, an adhesive structure using the same, and such an adhesive structure. The present invention relates to an electric power steering apparatus having a body.
[0002]
[Prior art]
Conventionally, a hydraulic assist type power steering (hydraulic power steering) has been often used for a power steering device of an automobile. However, since the hydraulic power steering uses the hydraulic pressure generated by driving the engine, there is a drawback that the fuel cost efficiency is reduced. In order to remedy such drawbacks, recently, as an alternative to hydraulic power steering, there is an example in which an electric power steering device with the assistance of a DC brushless motor is mounted on a small vehicle. However, in a large vehicle, it is difficult to apply the electric power steering device for a small vehicle as it is. In large-sized electric power steering devices, in order to obtain high output, large magnets cannot be sufficiently fixed by electric power steering devices used in small vehicles or by other conventional one-component epoxy adhesives. is there. That is, it is because the adhesive strength after the durability test is significantly lowered or the magnet is dropped after the durability test due to insufficient adhesive strength in a high temperature region or insufficient heat and heat cycle resistance.
[0003]
In order to avoid this, a magnet bonding method using a silicone adhesive having a low elastic modulus can be considered. However, a silicone adhesive is a relatively expensive adhesive, and a silicone adhesive has an absolute bonding strength. Therefore, the combined use of mechanical fixation (for example, mechanical stop) is inevitable. Mechanical fixation is undesirable because it induces magnetic field disturbances and reduces the overall efficiency of the motor.
[0004]
Thus, there is a demand for an adhesive having a high adhesive strength in a high temperature range and a cold-heat cycle resistance. Patent Document 1 discloses a method of using a fluorene epoxy resin in order to obtain a highly heat-resistant epoxy adhesive. Since this adhesive provides a resin having a high glass transition temperature (Tg) upon curing, it has high heat resistance, but is not necessarily excellent in heat cycleability. On the other hand, in Patent Document 2, an epoxy adhesive containing a cross-linked acrylic rubber is used in order to prevent breakage of a magnet in a cooling / heating cycle. However, the evaluation cycle is as short as 100 cycles, and the required characteristics such as adhesive strength are low in the first place.
[0005]
[Patent Document 1]
JP-A-6-192394 (Claims)
[Patent Document 2]
JP-A-8-283687 (Claims)
[0006]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to satisfy a high adhesive strength required for the manufacture of an electric power steering device for a large vehicle in a wide temperature range and to maintain the adhesive strength even after a cooling cycle. It is providing a type epoxy adhesive composition. The present invention also provides an adhesive structure in which motor parts are bonded with such an adhesive composition, and an electric power steering apparatus having such an adhesive structure.
[0007]
[Means for Solving the Problems]
The present invention solves the above problems, and according to one aspect of the present invention, 100 parts by mass of an epoxy resin containing at least an aromatic epoxy resin, 1 to 20 parts by mass of a dicyandiamide curing agent, a glass transition temperature ( Tg) is a one-pack type epoxy adhesive composition for an electric power steering apparatus, comprising 10 to 15 parts by mass of a toughness imparting agent comprising a thermoplastic elastomer having a temperature of less than -40 ° C, and a filler, There is provided an epoxy adhesive composition having a Tg after curing of the adhesive composition of 170 ° C. or more and a storage elastic modulus of 2 GPa or less as measured with a dynamic viscoelasticity tester at 25 ° C. and 10 Hz. The
Such an adhesive composition exhibits a high adhesive strength between the permanent magnet and the metal part in a wide temperature range during curing, and has excellent thermal shock resistance.
[0008]
According to another aspect of the present invention, there is provided an adhesive structure in which a motor shaft and a permanent magnet formed of a material having a linear expansion coefficient different from that of the motor shaft are fixed with the epoxy adhesive composition. Provided.
In such an adhesive structure, adhesion between the permanent magnet and the motor shaft is strong, and the cold-heat cycle can be improved.
[0009]
According to still another aspect of the present invention, in the electric power steering apparatus including a motor that generates assist torque that reduces the steering force applied to the steering wheel, the above-described adhesive structure is used for the motor. An electric power steering device is provided.
According to still another aspect of the present invention, a rack shaft having a ball screw groove having a ball screw structure is inserted and arranged along the axial direction of a motor shaft of a motor formed in a hollow cylindrical shape, and a ball having a ball screw structure is provided. A motor housing that includes a screw nut interposed between the motor shaft and the rack shaft, covers the motor shaft, and a plurality of rack housings that are coaxially coupled to both ends of the motor housing and cover the rack shaft; In an electric power steering apparatus in which both ends of a shaft are supported by bearings provided at both ends of a motor housing, an electric power steering apparatus using the above-described adhesive structure for the motor is provided.
By using the adhesive structure of the present invention that is strong and has improved cold-heat cycle, the permanent magnet and the motor shaft can be fixed with sufficient strength without using mechanical fixing. When the mechanical fixing is not used, the disturbance of the magnetic field due to the mechanical fixing and the reduction in the efficiency of the entire motor based on this can be eliminated, and the electric power steering apparatus itself can be miniaturized by simplifying the configuration of the motor.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The one-pack type epoxy adhesive composition for an electric power steering device of the present invention includes an epoxy resin containing at least an aromatic epoxy resin and a dicyandiamide-based curing agent, is a thermoplastic elastomer as a toughness imparting agent, and has a glass transition temperature ( Tg) contains a rubber component of less than −40 ° C. and further contains a certain amount of filler.
[0011]
The epoxy resin used in the adhesive composition of the present invention is bisphenol A type epoxy, bisphenol F type epoxy, bisphenol AD type epoxy, in order to develop high heat resistance and high adhesive strength after curing of the adhesive composition. It is preferable that an aromatic epoxy such as bisphenol S type epoxy or biphenyl type epoxy is contained as a main component and a bisphenol A type epoxy resin (DGEBA) is contained as a main component. Such an aromatic epoxy resin imparts a high Tg to the cured adhesive, and thus improves the heat resistance of the adhesive and improves the adhesive strength in a high temperature range.
[0012]
As an epoxy resin, it is preferable to contain the epoxy resin exceeding bifunctionality in addition to said aromatic epoxy resin. It is because Tg of the adhesive composition after curing can be set to 170 ° C. or more by containing the polyfunctional epoxy resin having a bifunctionality together with the aromatic epoxy resin. Examples of such a polyfunctional epoxy resin exceeding the bifunctionality include tetraglycidyl diaminodiphenylmethane and novolac type epoxy resin.
[0013]
As the epoxy resin, polyhydric alcohol type epoxy such as polyethylene glycol type epoxy and polypropylene glycol type epoxy can be used. Besides, glycidylamine type epoxy, dimer acid-modified glycidyl ester type epoxy, halogenated epoxy Other epoxy resins such as aminophenol-type epoxies.
[0014]
Moreover, 1-20 mass parts dicyandiamide type | system | group hardening | curing agent is used per 100 mass parts of epoxy resins as a hardening | curing agent for epoxy resins. When the amount of the curing agent is less than the above range, the adhesive is not sufficiently cured, and the glass transition temperature (Tg) becomes low. Even when the amount is larger than the above range, the cured adhesive Tg It may lead to deterioration of characteristics such as lowering. The dicyandiamide-based curing agent may be dicyandiamide or a derivative thereof. The curing agent may be used in combination with a conventional curing catalyst.
[0015]
The one-pack type epoxy adhesive composition includes a rubber component having a glass transition temperature of less than −40 ° C. as a toughness imparting agent. Such a toughness imparting agent imparts high adhesive strength and thermal shock resistance at low temperatures to the adhesive after the adhesive composition is cured. The reason why Tg is less than −40 ° C. is to ensure that the toughness-imparting agent can maintain the elastomeric property even when the use condition of the automobile is extremely low. Examples of such a toughness imparting agent include isoprene rubber, natural rubber, butadiene rubber, styrene-butadiene rubber, butadiene-acrylonitrile rubber, chloroprene rubber, urethane rubber, fluorine rubber, and acrylic rubber. In addition, a core-shell type polymer having the rubber component as a core part can also be used as a toughness imparting agent. In such a core-shell type polymer, an acrylic polymer can be exemplified as a material constituting the shell portion.
[0016]
The toughness-imparting agent is included in an amount that gives good properties to the cured adhesive composition, and is included in an amount of 10 to 15 parts by mass per 100 parts by mass of the epoxy resin in the epoxy adhesive composition. If the amount of the toughness-imparting agent is less than 10 parts by mass, the adhesive strength at low temperatures may not be sufficient, and the thermal shock resistance may not be sufficient. On the other hand, when the toughness-imparting agent exceeds 15 parts by mass, the adhesive strength at high temperatures may be insufficient.
[0017]
The epoxy adhesive composition of the present invention contains a suitable amount of filler. Since the linear expansion coefficient of the adhesive composition can be suppressed, the filler can improve the adhesive strength in the high temperature range of the adhesive composition after curing, and also has the effect of improving the thermal shock resistance. Have. Fillers can also reduce the cost of the adhesive composition. Specifically, metal, metal oxide, or inorganic powder may be used as the filler. More specifically, the filler can be powdered aluminum metal, alumina, silica, or barium sulfate. The form of the particles may be spherical, elliptical, acicular, or flat, and is not particularly limited. Moreover, although not necessarily limited, the particle size of a filler is generally 10-60 micrometers. In addition, the particle size of a filler means the maximum length of a filler cross section. If the particle size of the filler is too small, the viscosity of the adhesive composition becomes too high, and workability during application may be deteriorated. On the other hand, when the particle size of the filler is too large, the adhesive layer becomes too thick, and the performance such as shear bond strength decreases.
[0018]
The amount of the filler is not limited, but is generally included in the adhesive composition in an amount of 80% by mass or less. This is because if the amount of the filler is too large, the adhesive strength may decrease.
[0019]
Hereinafter, an electric power steering apparatus to which the epoxy adhesive composition of the present invention can be applied will be described. FIG. 1 shows a partially exploded view of the electric power steering apparatus. The electric power steering apparatus 11 includes a hollow cylindrical first rack housing 12, a hollow cylindrical second rack housing 13, and a hollow cylindrical motor housing 14 coaxially coupled to the two rack housings. It is supported by the body of the vehicle body that is not screwed and fixed via a mounting portion 15 formed in the first rack housing 12.
[0020]
A cylindrical body constituted by the first rack housing 12, the second rack housing 13 and the motor housing 14 incorporates a rack shaft 16 which is not rotatable and is movable in the axial direction. The left and right front wheels are connected via a tie rod (not shown) connected to The rack shaft 16 is connected to a steering wheel (not shown) via a pinion shaft 17 provided in the first rack housing 12. An engagement portion (not shown) of a rack and pinion mechanism is formed between the rack shaft 16 and the pinion shaft 17. The motor housing 14 also functions as a rack housing for the electric power steering apparatus.
[0021]
Next, description will be made with reference to FIG. A stator 19 having windings is fitted to the inner periphery of the motor housing 14, and a motor shaft 18 is coaxially formed outside the rack shaft 16 coaxially in a hollow cylindrical shape at an intermediate portion in the axial direction of the rack shaft 16. It is fitted.
[0022]
The motor shaft 18 is formed with a fitting step portion 18c on one end side (pinion shaft 17 side), and the fitting step portion 18c is connected to the motor housing 14 and the first rack housing via a first bearing 21 as a bearing. 12 is supported.
The first bearing 21 is connected to the first fitting step 14a and the fitting step 12a formed so as to go around the inner peripheral surface of the end portion of the motor housing 14 and the inner peripheral surface of the end portion of the first rack housing 12, respectively. The inner fitting is fixed.
[0023]
Further, the first bearing 21 is pressed in the axial direction by being fastened by a first lock nut 22 screwed to the end of the motor shaft 18, and is fixed to the motor shaft 18. A permanent magnet 27 is externally provided and fixed to the motor shaft 18 via an epoxy adhesive according to the present invention.
[0024]
The motor housing 14 is in contact with each other at a first contact portion 14c provided at the end portion, and the first rack housing 12 is in contact with each other at an contact portion 12b provided at the end portion. By screwing the fixing screw 24 inserted through 12b into the first abutting portion 14c, both are fastened and connected to each other by the fixing screw 24. A thin packing 23 is interposed between the mating surfaces of the first contact portion 14c and the contact portion 12b. The packing 23 prevents intrusion of liquid such as water and oil from the fitting portion between the motor housing 14 and the first rack housing 12. With this configuration, the motor housing 14, the first rack housing 12, and the first bearing 21 are fitted in one place. Further, the movement of the motor shaft 18 in the axial direction is restricted via the first bearing 21 fitted in the motor housing 14 and the first rack housing 12.
[0025]
On the other end side of the motor shaft 18 (on the side opposite to the pinion shaft 17 side), a hollow cylindrical nut holding portion 18a whose diameter is larger than that of the intermediate portion is integrally formed.
Further, a second fitting step 14 b that circulates is formed on the inner peripheral surface of the other end side of the motor housing 14. The motor shaft 18 is rotatably fitted around its own axis by fitting the nut holding portion 18a into the second bearing 20 as a bearing fitted and fixed to the second fitting step portion 14b. It is supported. The second bearing 20 is configured to be movable in the axial direction between the second fitting step 14 b of the motor housing 14 and the end 13 a of the second rack housing 13.
[0026]
The end portion 13 a of the second rack housing 13 is fitted into the motor housing 14, and the contact portion 13 b that extends from the outer peripheral surface of the end portion 13 a is formed on the end surface of the second contact portion 14 d of the motor housing 14. It is in contact. The motor housing 14 and the second rack housing 13 are tightened and connected to each other by the fixing screw 25 by screwing the fixing screw 25 inserted through the contact portion 13b into the second contact portion 14d.
[0027]
A circumferential groove 13d is formed on the outer peripheral surface of the end portion 13a fitted in the motor housing 14, and an O-ring 29 is fitted in the circumferential groove 13d. The O-ring 29 prevents the intrusion of liquid such as water or oil from the fitting portion between the motor housing 14 and the second rack housing 13.
[0028]
Further, the motor housing 14 and the motor shaft 18 are configured with high accuracy by the first bearing 21 and the second bearing 20. With the above configuration, both ends of the motor shaft 18 are supported by the first bearing 21 and the second bearing 20 provided at both ends of the motor housing 14.
[0029]
A ball screw nut 26 is coaxially fitted in the nut holding portion 18 a of the motor shaft 18. The ball screw nut 26 is fixed to prevent the ball screw nut 26 from being removed by screwing the second lock nut 28 into the nut holding portion 18a.
[0030]
On the outer peripheral surface of the rack shaft 16, a spiral ball screw groove 16a is provided in a predetermined range in the axial direction. A spiral ball screw groove 26a is provided on the inner peripheral surface of the ball screw nut 26, and a large number of balls (not shown) are received between the ball screw groove 16a and the ball screw groove 26a so as to be able to roll. ing. Thus, a ball screw mechanism having a ball screw structure is formed by the ball screw groove 16 a of the rack shaft 16 and the ball screw nut 26. The ball screw mechanism converts the rotational torque of the motor shaft 18 in the forward / reverse rotation into the assist force for the reciprocating motion of the rack shaft 16 in the axial direction, and the steering force of a steering wheel (not shown) connected to the pinion shaft 17 is obtained. It comes to reduce.
[0031]
The epoxy adhesive composition of the present invention can be used for bonding the motor shaft 18 and the permanent magnet 27 of the electric power steering device as described above. The adhesive composition of the present invention is applied to a magnet and / or a motor shaft by a spatula, an automatic syringe applicator, or the like and cured at a temperature of 120 to 150 ° C. for 30 to 120 minutes.
[0032]
The rack assist type electric power steering apparatus in which the motor shaft 18 and the rack shaft 16 are arranged coaxially has been described above. However, the rack assist type electric power in which the motor shaft and the rack shaft are arranged non-coaxially is described. Also in the adhesion of permanent magnets and motor shafts of other electric power steering devices such as steering devices (for example described in JP-A-8-207796), column assist type, pinion assist type, direct drive type electric power steering device The epoxy adhesive composition of the present invention can be used. Furthermore, the electric power steering apparatus referred to in the present invention includes a variable transmission ratio mechanism for driving an electric motor so as to change the relationship between the turning angle of the steering wheel and the turning angles of the wheels (left and right front wheels) according to various conditions. Including a steering device (for example, described in Japanese Patent Application Laid-Open No. 2000-211151), and the present invention can also be applied to an electric motor of this variable transmission ratio mechanism. When the permanent magnet and the motor shaft are bonded using the epoxy adhesive composition of the present invention, it is possible to obtain a bonded structure having a strong and excellent thermal cycle resistance, and therefore, between the permanent magnet and the motor shaft. It is no longer necessary to use mechanical fixation together with the fixation. For this reason, since the structure of a motor can be simplified and a motor can be reduced in size, there exists an effect that the whole electric power steering device can be reduced in size.
[0033]
【Example】
Below, the epoxy-type adhesive composition of this invention is further demonstrated based on an Example.
Example 1 and Comparative Examples 1-3
A one-component epoxy adhesive composition having the composition shown in the formulation table of Table 1 below was prepared. A predetermined amount of each raw material was weighed into a container and mixed with a conditioning mixer until uniform.
[0034]
[Table 1]

[0035]
In the above table, DGEBA is a bisphenol A type epoxy resin manufactured by Yuka Shell Co., Ltd.
Epicoat 807 is a bisphenol F type epoxy resin manufactured by Yuka Shell Co., Ltd.
TGDDM is tetraglycidyldiaminodiphenylmethane (YH434) manufactured by Toto Kasei Co., Ltd.
FX602 is a rubber component composed of carboxyl group-containing crosslinked nitrile butyl rubber (NBR) manufactured by Nippon Synthetic Rubber Co., Ltd. (JSR), and has a glass transition temperature (Tg) of about −50 ° C.
AC3355 is a rubber component made of an acrylic core-shell polymer manufactured by Gantz Kasei Co., Ltd., and the Tg of the core component is about −20 ° C.
CG1400 is dicyandiamide manufactured by Air Products Co., Ltd.
DCMU is 3- (3,4-dichlorophenyl) -1,1-dimethylurea manufactured by Aldrich Co., Ltd.
The aluminum metal powder is AC2500 manufactured by Toyo Aluminum Co., Ltd.
Alumina powder is AS-10 manufactured by Showa Denko KK
A200 is a silica powder manufactured by Aerosil Co., Ltd.
[0036]
Under the following conditions, the shear bond strength of the adhesive joining two aluminum test pieces was measured, and the shear bond strength and thermal shock resistance of the adhesive joining the neodymium magnet and the iron test piece were measured. Was measured.
1. Shear bond strength test piece size for joining aluminum test pieces (Al): 1.6 mm × 25 mm × 100 mm
Bonding area: 12.5mm x 25mm
Adhesive layer thickness: 0.1 mm
Curing condition: 30 minutes at 140 ° C. Tensile speed: 5 mm / min Surface treatment: Chromic acid mixed solution (FPL) etching Shear strength and thermal shock resistance test specimen size in joining of neodymium magnet (Nd) and iron specimen (Fe): Nd magnet 7.65 mm x 4.83 mm x 45.5 mm, FeSC45C: 3.2 mm x 25 mm x 100mm
Bonding area: 8mm x 35mm
Adhesive layer thickness: 0.1 mm
Curing conditions: 140 ° C. for 30 minutes Tensile speed: 5 mm / min Surface treatment: Methyl ethyl ketone (MEK) degreasing and cooling cycle: −40 ° C. to 120 ° C.
[0037]
[Table 2]

[0038]
From Table 2 above, it was confirmed that the adhesive composition of the present invention has excellent thermal shock resistance even after 1000 cycles of cooling and heating.
[0039]
【The invention's effect】
The one-pack type epoxy adhesive composition of the present invention has high adhesive strength in a wide temperature range, and has excellent adhesive strength even after a cooling and heating cycle.
In addition, when the permanent magnet and the motor shaft are bonded using the epoxy adhesive composition of the present invention, a strong and excellent heat cycle resistance can be obtained, so that the permanent magnet and the motor shaft There is no need to use mechanical fixing together with fixing between the two. For this reason, since the structure of a motor can be simplified and a motor can be reduced in size, the whole electric power steering apparatus can be reduced in size.
[Brief description of the drawings]
FIG. 1 shows a partially exploded view of an electric power steering apparatus.
2 shows an enlarged view of the electric power steering apparatus of FIG. 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Electric power steering apparatus 12 ... 1st rack housing 13 ... 2nd rack housing 14 ... Motor housing 16 ... Rack shaft 18 ... Motor shaft 20 ... 2nd bearing (bearing)
21 ... 1st bearing (bearing)
26 ... Ball screw nut

Claims (4)

Toughness comprising at least 100 parts by weight of an epoxy resin containing at least an aromatic epoxy resin and an epoxy resin having more than two functions, 1 to 20 parts by weight of a dicyandiamide curing agent, and a thermoplastic elastomer having a glass transition temperature (Tg) of less than −40 ° C. A one-component epoxy adhesive composition for an electric power steering apparatus, comprising 10 to 15 parts by mass of an imparting agent and a filler, wherein Tg after curing of the adhesive composition is 170 ° C. or higher And the epoxy-type adhesive composition whose storage elastic modulus is 2 GPa or less when it measures with a dynamic-viscoelasticity testing machine in 25 degreeC and 10 Hz.   The adhesion structure which fixed the motor shaft and the permanent magnet formed with the material from which a linear expansion coefficient differs compared with this motor shaft with the epoxy-type adhesive composition of Claim 1.   An electric power steering apparatus comprising a motor for generating an assist torque for reducing a steering force applied to a steering wheel, wherein the adhesive structure according to claim 2 is used for the motor.   A rack shaft having a ball screw groove of a ball screw structure is inserted and arranged along the axial direction of the motor shaft of the motor formed in a hollow cylindrical shape, and the ball screw nut of the ball screw structure is interposed between the motor shaft and the rack shaft. A motor housing that covers the motor shaft and a plurality of rack housings that are coaxially coupled to both ends of the motor housing and cover the rack shaft, and both ends of the motor shaft are provided at both ends of the motor housing. An electric power steering apparatus supported by a bearing, wherein the adhesive structure according to claim 2 is used for the motor.

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