JP5630341B2 - Management method of adhesive shear strength - Google Patents

Description

  The present invention relates to an adhesive shear strength of an adhesive surface of an adhesive structure using an adhesive.

  High heat resistance and durability are required for the electric power steering device parts, particularly the bonded portion of the permanent magnet constituting the motor. For this reason, epoxy adhesives that are difficult to bond to permanent magnets but have high heat resistance are used. Even today, the adhesive strength is improved and electric power steering devices for large vehicles are required. There is a need to provide an adhesive structure using an adhesive that can satisfy such a high adhesive shear strength in a wide temperature range and maintain the adhesive shear strength even after a thermal cycle.

  In Patent Document 1, an epoxy adhesive is conventionally used as an adhesive, and there is a problem of residual stress at the adhesive interface due to temperature change, and the adhesive has been studied. However, in terms of quality that leads to durability due to adhesion peeling. This issue is not mentioned.

  Patent Document 2 discusses a cleaning agent for adhesives that is excellent in cleaning removal and storage of contaminants on the adhesive surface, but the problem of quality control of cleaning that affects adhesive shear strength is not clarified.

JP 2005-15563 A JP 2008-138072 A

  Adhesion between the motor magnet and the motor shaft of the electric power steering is heat-resistant and high-strength epoxy adhesive is used. However, the adhesive strength decreases due to the curing inhibitor and contaminants of the motor magnet and adhesive. As a result, there is a problem that the durability of the motor magnet is deteriorated due to peeling off of the motor magnet, leading to poor steering performance. As one of the causes, it has become clear that the cleanliness of the bonding surface between the motor magnet and the motor shaft, particularly the cleaning liquid and the cleaning management method, affect the durability of the adhesive shear strength.

  In order to solve the above-described problems, an object of the present invention is to provide a method for managing an adhesive shear strength having a stable adhesive shear strength of an adhesive.

  In order to solve the above-mentioned problems, the structural feature of the invention according to claim 1 is that as a pretreatment for bonding a motor magnet to a motor shaft of a motor used in an electric power steering apparatus, the adhesion surface of the motor magnet of the motor shaft is In the management method of adhesive shear strength, which manages the adhesive shear strength by the cleaning liquid to be cleaned, the adhesive surface of the motor magnet and the motor shaft has a cleaning liquid temperature of 65 ± 5 ° C. and a pH of 9 or more, and the number of bacteria in the cleaning liquid is 1000 / mL or less. The gist is to wash with the above-mentioned washing liquid.

  According to the invention according to claim 1 configured as described above, since the adhesion surface of the motor magnet and the motor shaft is washed with a cleaning liquid that is less susceptible to bacterial decay, no contaminants remain on the adhesion surface. Adhesive strength can be secured.

  Further, in order to solve the above problems, the structural feature of the invention according to claim 2 is that an organic cleaning agent containing an antibacterial agent is used as a cleaning solution for the adhesion surface of the motor magnet and the motor shaft. .

  According to the invention according to claim 2 configured as described above, since the organic cleaning agent is used as the cleaning liquid for the adhesive surface, the generation of bacteria is suppressed due to the antibacterial agent, and the adhesion of inorganic components does not occur. Since the bond shear strength does not decrease, a high-quality bonded structure with good durability can be obtained.

  According to the present invention, since the strength of the adhesive layer does not decrease due to contaminants, an epoxy-based adhesive structure having a stable and adhesive strength can be obtained. A steering device can be provided.

1 is an overall view of an electric power steering device. It is a principal part enlarged view of an electric power steering device. It is a figure which shows the creep durability test result by a pollutant. It is a figure which shows the change of the number of bacteria by pH in 50 degreeC of a washing | cleaning liquid. It is a figure which shows the change of the number of bacteria by pH at 65 degreeC of a washing | cleaning liquid. It is a creep durability test result of the adhesive composition with the inventive cleaning liquid.

11 Electric Power Steering Device 12 First Rack Housing 13 Second Rack Housing 14 Motor Housing 16 Rack Shaft
18 Motor shaft
20 Second bearing (bearing)
21 First bearing (bearing)
26 Ball screw nut

  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 an appropriate amount of filler.

  The epoxy resin used in the adhesive composition is bisphenol A type epoxy, bisphenol F type epoxy, bisphenol AD type epoxy, bisphenol S type epoxy in order to develop high heat resistance and high adhesive strength after curing of the adhesive composition. Alternatively, it is preferable that an aromatic epoxy such as a biphenyl type epoxy is included as a main component and a bisphenol A type epoxy resin (DGEBA) is included 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.

  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.

As cleaning agents, organic rust preventives, inorganic rust preventives, and soaps are used.
Clean the motor magnet and motor shaft. Washing is performed in the following process sequence.
Adhesive product → First cleaning → Liquid blow → Second wash → Liquid blow → Drying → Adhesive application → Heat curing Then, apply to motor magnet 27 and / or motor shaft 18 with a spatula, syringe automatic applicator, etc. Bonding is performed by curing at a temperature of 120 to 150 ° C. for 30 to 120 minutes.

Next, an example of a preferred embodiment of the present invention will be described.
In the bonded structure of the permanent magnet of the motor, the non-defective condition is that the thickness of the bonding agent layer on the bonded surface of the motor magnet and the motor shaft is 0.1 mm or more. If the thickness is less than 0.1 mm, the residual stress of the bonded product increases, and there is a risk of peeling off due to fatigue due to repeated temperature changes. Further, the initial bonding shear strength of the bonding agent layer is 19 MPa or more as a good product condition.
It was found that there is a proportional relationship between the amount of the inorganic component of the cleaning liquid and the durability at high temperature and high humidity, and the durability decreases as the amount of the inorganic component increases. It was found that the amount of bacteria and the temperature of the cleaning solution can be controlled to control the amount of inorganic components in the cleaning solution.

  The thickness of the bonding agent layer on the adhesive surface can be measured, for example, by cutting a rotor of a motor magnet in a direction perpendicular to the axis and observing the bonding material layer in the cross section with a scanning electron microscope (SEM). The bonding shear strength of the bonding material layer can be determined by applying stress in the shear direction to the bonding agent layer and measuring the stress during shearing using a tensile tester.

  The adhesion structure for the electric power steering apparatus can be formed by applying an epoxy adhesive to the adhesion surface of the motor magnet and the motor shaft and curing it.

  Hereinafter, an electric power steering apparatus to which the adhesive composition can be applied will be described. FIG. 1 is an overall view of an 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.

  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.

  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.

  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 rotatably. 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.

  Further, the first bearing 21 is pressed in the axial direction by being fastened by a first lock nut 22 screwed into an end portion of the motor shaft 18, and is fixed to the motor shaft 18. A motor magnet 27 is externally fixed to the motor shaft 18 with the adhesive according to the present invention.

  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 contact portion 14c, the two 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 or oil from the fitting portion between the motor housing 14 and the first rack housing 12 into the inside. 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.

  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 can be rotated about its own axis by the nut holding portion 18a being fitted in 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.

  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.

  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.

  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.

  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.

  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 forward / reverse rotation of the motor shaft 18 into the assist force of 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.

  As described above, the adhesive is used for bonding the motor shaft 18 and the motor magnet 27 of the electric power steering apparatus. The adhesive is applied to the motor magnet 27 and / or the motor shaft 18 after the cleaning process by applying a spatula, an automatic syringe applicator or the like, and curing the adhesive at a temperature of 120 to 150 ° C. for 30 to 120 minutes.

  Although the rack assist type electric power steering apparatus in which the motor shaft 18 and the rack shaft 16 are coaxially arranged has been described above, the rack assist type electric power steering apparatus in which the motor shaft and the rack shaft are arranged non-coaxially is described. The adhesive composition is also used for bonding the motor magnet and the motor shaft of other electric power steering devices such as the device, column assist type, pinion assist type, and direct drive type electric power steering device. Furthermore, the electric power steering device includes a steering with a variable transmission ratio mechanism for driving the electric motor so as to change the relationship between the turning angle of the steering wheel and the turning angle of the wheels (the left and right front wheels) according to various conditions. The device is also included, and is applied to the electric motor of this transmission ratio variable mechanism.

エポキシ系接着剤は接着面の洗浄剤に含まれる物質（リン、カリウム）により接着せん断強度の低下を起こすため、各種成分を添加した洗浄液でその影響を確認した。接着試験片をｐＨ７から１０の洗浄液にディッピング後，６０℃恒温槽内で乾燥ＴＰ表面の無機成分の付着状態を確認するため，ＥＰＭＡで元素マッピングを実施した。また、接着せん断強度測定試料はダブルラップシェアー試験片（材質：ＪＩＳＧ３１４１：ＳＰＣＣ）を用いて、表２の条件で実施した。クリープ耐久性試験は表２に記載の条件で実施して、初期と１００時間後の接着せん断強度の比較によりクリープ耐久性保持率を求めて評価した。
表３に分析結果を示し、図３にクリープ耐久性評価結果を示す。

Example 1
Below, the cleaning management method of the epoxy adhesive composition of the present invention will be described based on examples. Table 1 shows the basic composition of the cleaning solution.

Since the epoxy adhesive causes a decrease in the adhesive shear strength due to substances (phosphorus, potassium) contained in the cleaning agent for the bonding surface, the influence was confirmed with cleaning liquids to which various components were added. After dipping the adhesion test piece into a cleaning solution having a pH of 7 to 10, element mapping was performed with EPMA in order to confirm the adhesion state of the inorganic component on the surface of the dried TP in a 60 ° C. constant temperature bath. Moreover, the adhesive shear strength measurement sample was implemented on the conditions of Table 2 using the double lap shear test piece (material: JISG3141: SPCC). The creep durability test was carried out under the conditions shown in Table 2, and the creep durability retention rate was determined and evaluated by comparing the initial and the shear shear strength after 100 hours.
Table 3 shows the analysis results, and FIG. 3 shows the creep durability evaluation results.

実施例２
洗浄液の温度を５０±５℃および６５±５℃に変化させてｐＨを変化した洗浄液のバクテリアの測定結果をそれぞれ図４、５に示す。
バクテリア数は市販の簡易装置 例えば、三愛石油(株)製サンアイバイオチェッカＴＴＣを使用した。 As shown in Table 3, it was found that the adhesion of inorganic components such as phosphorus and potassium is extremely reduced when the pH is 9 or more.
As a result, it was found that creep durability was improved at pH 9 or higher as shown in FIG.

Example 2
FIGS. 4 and 5 show the measurement results of bacteria of the cleaning solution whose pH was changed by changing the temperature of the cleaning solution to 50 ± 5 ° C. and 65 ± 5 ° C., respectively.
For the number of bacteria, a commercially available simple device, for example, Sanai Bio Checker TTC manufactured by Sanai Oil Co., Ltd. was used.

  As a result, as shown in FIG. 4, under the condition of 50 ± 5 ° C., the pH drops sharply when bacteria increase (it is considered to change by generating acid).

  On the other hand, as shown in the change in the number of bacteria at the time of pH change in FIG. 5, at the temperature of the cleaning solution of 65 ± 5 ° C., no increase in bacteria is observed and the pH does not decrease. Therefore, it was found that the temperature of the cleaning liquid should be controlled at 65 ± 5 ° C. as a pretreatment of the adhesive.

Example 3
In addition, as shown in Table 4, when the antibacterial agent is added as a cleaning agent and the inorganic component is eliminated, the creep durability is improved even in a low pH range as shown in the results of FIG. all right.

In other words, in order to reduce the adhesion of inorganic components that affect adhesiveness, the addition of antibacterial agents suppresses the generation of bacteria, and the use of a cleaning solution that does not contain an inorganic component of the water-absorbing component suppresses the decrease in adhesiveness and reduces the adhesive shear strength. Durability can be maintained.

Claims (2)

  As a pretreatment for bonding a motor magnet to a motor shaft of a motor used in an electric power steering apparatus, a motor magnet is used in a management method for bonding shear strength in which the bonding shear strength is managed by a cleaning liquid for cleaning the bonding surface of the motor magnet of the motor shaft. And cleaning the adhesive surface of the motor shaft with a cleaning solution having a cleaning solution temperature of 65 ± 5 ° C. and a pH of 9 or more, and a cleaning solution having a bacteria count of 1000 / mL or less.   2. The method of managing adhesive shear strength according to claim 1, wherein an organic cleaning agent containing an antibacterial agent is used as a cleaning liquid for the bonding surface of the motor magnet and the motor shaft.

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