JP5625362B2 - Method for managing adhesive shear strength of silicone-based adhesive structures - Google Patents

Description

  The present invention relates to a method for managing the adhesive shear strength of an adhesive structure using a silicone-based adhesive.

  Epoxy adhesives with heat resistance and high adhesive shear strength are used for bonding the permanent magnets of motors in electric power steering devices, but residual stress and environmental degradation between the permanent magnets and metal parts depending on the usage conditions ( Adhesive shear strength decreases due to heat, temperature, etc., and the permanent magnet peels off, resulting in poor durability. Therefore, the combined use of adhesion and mechanical fixing is inevitable. On the other hand, silicone adhesives that are flexible and have excellent chemical stability are used to increase the adhesive shear strength, but silicone adhesives have the problem of poor adhesion due to the deactivation of the platinum catalyst, and their use is limited. ing. In such a background, an adhesive structure having heat resistance and good durability is required.

Epoxy adhesives have been improved to solve the above problems of silicone adhesives. (Patent Document 1) On the other hand, silicone adhesives with good heat resistance may be used, but quality control such as insufficient adhesive shear strength and inhibition of curing is important, and various silicone materials are improved. Has been made. (Patent Document 2)

JP-A-2005-15563 JP 5-7427

  High heat resistance and durability are required for the power steering device parts, particularly the bonded portions of the permanent magnets constituting the motor. Therefore, there is a great demand for a silicone-based adhesive with good heat resistance instead of an epoxy-based adhesive that has a difficulty in bonding shear strength for bonding a permanent magnet. Therefore, by clarifying the tolerance for curing inhibition of silicone adhesives, the management method and manufacturing process are improved, and high adhesive shear is required for silicone-based adhesives for electric power steering devices of large vehicles. There is a need to provide a silicone-based adhesive structure using a silicone-based adhesive that satisfies the strength over a wide temperature range and can maintain the adhesive shear strength even after a thermal cycle.

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

In order to solve the above problems, the present invention provides a management method of the adhesive shear strength of the adhesive portion of the silicone based adhesive structure bonded with silicone adhesive, the adhesive surface nitrogen, and amount of elemental Io c, wherein By measuring the bond shear strength of the bonded part, an approximate function in which the moles of nitrogen and sulfur and the bond shear strength are proportional to each other is set in advance, and the amounts of nitrogen and sulfur elements on the bonding surface to be measured are determined. Measured and converted to moles, the adhesive shear strength of the adhesive part in the silicone-based adhesive structure characterized by estimating the adhesive shear strength of the adhesive part to be measured from the mole of the measurement result and the approximate function It is summarized as management how.

Setting adhesive surface of Chisso, the amount of elemental Io c, by measuring the adhesion shear strength of the adhesive portion, in advance, nitrogen, and moles of sulfur, an approximate function the adhesive shear strength is proportional By measuring the amount of nitrogen and sulfur elements on the adhesion surface of the measurement object and converting them to moles, the bond shear strength of the adhesion part of the measurement object is estimated from the moles of the measurement results and the approximate function. a contaminant contained in the cleaning agent of the adhesive surface nitrogen, the adhesive shear strength required be managed moles of sulfur below the specified amount can be obtained, Ru can manage adhesive shear strength of the silicone-based adhesive structure .

According to the present invention, the amount of the nitrogen and sulfur elements on the adhesion surface of the measurement object is measured and converted to moles, and the mole of the measurement result and the approximate function obtained in advance are used to determine the adhesion portion of the measurement object. By estimating the adhesive shear strength, the required adhesive shear strength can be obtained if the moles of nitrogen and sulfur on the adhesive surface are controlled below a prescribed amount, and the adhesive shear strength of the silicone-based adhesive structure can be managed .

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 relationship between the mole of a contaminant, and adhesive shear strength.

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

  Hereinafter, an electric power steering apparatus to which the silicone adhesive of the present invention 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 composed of 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. A meshing 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 on 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 fixed to the motor shaft 18 by being pressed in the axial direction by being tightened by a first lock nut 22 screwed into an end portion of the motor shaft 18. A permanent magnet 27 is externally fixed to the motor shaft 18 by the silicone adhesive according to the present invention.

Next, an example of a preferred embodiment of the present invention will be described.
In bonding structure of a permanent magnet motor, the adhesive surface of the motor magnet and the motor shaft is nitrogen, the molar contaminants Io c is a 0.1 [mu] mol / cm ² or less, the thickness of the cement layer is more than 0.1mm Is a good product condition. 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.
The bonding shear strength of the bonding agent layer is a good product condition of 6 MPa or more. When the adhesive shear strength is 6 MPa or less, the bonding agent layer creeps at a high temperature, the strength decreases, the bonding agent layer thickness decreases, the residual stress increases, and fatigue occurs. There is a possibility that the adhesive peels off and the durability is lowered. Since the strength can be predicted and estimated by measuring contaminants on the adhesive surface by this management method, the required adhesive shear strength can be obtained by controlling the moles of contaminants to a specified amount or less.

The adhesive surface of the nitrogen, the measurement of the amount of elemental Io c is carried out by ultraviolet fluorescence analyzer, the thickness of the bonding agent layer, for example a rotor of the motor magnet was cut perpendicular to the axis, scanning the bonding agent layer in the cross section It can be measured by observing with a scanning electron microscope (SEM). The adhesive shear strength of the bonding agent layer can be determined by applying a stress in the shearing 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 of the present invention can be formed by applying a silicone adhesive to the adhesion surface of the motor magnet and the motor shaft and curing it. As the silicone-based adhesive, a known silicone-based adhesive can be used. Specifically, the silicone adhesive contains at least two alkenyl groups such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, and a cyclohexenyl group as a silicone rubber composition. An adhesive containing diorganopolysiloxane and organohydrogenpolysiloxane can be used.

For the silicone-based adhesive, platinum group metal catalysts such as platinum (including platinum black), rhodium, palladium, etc. can be used as the platinum group metal catalyst at the time of curing, but in addition, H ₂ PtCl _4. nH ₂ O, H ₂ PtCl ₆ .nH ₂ O, NaHPtCl ₆ .H ₂ O, K ₂
PtCl ₄ · nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ · nH
₂ O (wherein n is an integer of 0-6, preferably 0 or 6), such as platinum chloride, chloroplatinic acid and chloroplatinate, alcohol-modified chloroplatinic acid, chloroplatinic acid and Complex with olefin, platinum black, platinum group metals such as palladium, supported on alumina, silica, carbon, etc., rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst), platinum chloride, It contains a complex of chloroplatinic acid or chloroplatinate and a vinyl group-containing siloxane, particularly a vinyl group-containing cyclic siloxane.

  The silicone adhesive preferably further contains an organic peroxide in addition to the platinum group metal catalyst. In this case, the curing of the adhesive is further facilitated. Organic peroxides may be inhibited from curing by oxygen. As described above, the combined use of an organic peroxide and a platinum group metal catalyst allows the interface between the peroxide and the platinum group metal catalyst. Curing can be advanced by the action, and inside, the hardening can be advanced by the action of the organic peroxide. Therefore, the adhesive shear strength of the bonding agent layer can be further improved.

  The organic peroxide functions as a catalyst for crosslinking the resin component by radical reaction. Specific examples include ketone peroxide, hydroperoxide, diacyl peroxide, dialkyl peroxide, peroxyketal, alkyl perester, and percarbonate. More specifically, for example, di-tert-butyl peroxide, dicumyl peroxide, diisopropylbenzene hydroperoxide, 1,3-bisbenzene, 1,1-di (t-butylperoxy) cyclohexane and the like can be used.

  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. Furthermore, 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 is rotatable about its own axis by the nut holding portion 18a being fitted 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.

  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.

  A spiral ball screw groove 16 a is provided on the outer peripheral surface of the rack shaft 16 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 an 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.

Silicone adhesive of the present invention, as described above, can be used for adhesion between the motor shaft 18 and the permanent magnet 27 of the electric power steering apparatus. Spatula adhesive to the magnets 27 and / or motor shaft 18 of the present invention, such as by applying a syringe automatic applicator, 30-120 minutes at a temperature of 120 to 150 ° C., is adhered by curing.

The rack assist type electric power steering device in which the motor shaft 18 and the rack shaft 16 are coaxially arranged has been described above, but the rack assist type electric power steering device in which the motor shaft and the rack shaft are arranged non-coaxially is described. apparatus, a column assist type, pinion-assist type, can be used a silicone-based adhesive of the present invention in the adhesive of the direct drive type electric power other electric power steering system permanent magnets and the motor shaft, such as a steering device. 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. The present invention can also be applied to an electric motor of the variable transmission ratio mechanism.

In below, describing a method for controlling quality silicone adhesive of the present invention based on examples.
Silicone-based adhesives are known to cause curing inhibition due to contaminants (chisso, sulfur) contained in the cleaning agent for the adhesive surface. Monoisopropanolamine CH ₃ CH (OH) CH ₂ NH ₂ which is a cleaning agent _, Diethanolamine (CH ₃ CH ₂ OH) ₂ NH _, triethanolamine (CH ₃ CH ₂ OH) ₃ N _{, and} dodecanethiol CH ₃ (CH ₂ ) ₁₁ SH were added to the adhesive surface to confirm the effect. The results are shown in Figure 3. An ultraviolet fluorescence analyzer is used to measure the amount of contaminants on the adhesive surface . The adhesive shear strength measurement is double-wrapped shear specimens bonded portion having an adhesive surface with the addition of contaminants (Material: JISG3141: SPCC) was used to carried out in the conditions of Table 1.

Next, the amount of the pollutant (nitrogen, sulfur) element is converted into moles, and the area of the adhesive surface is divided to give mol per unit area μmol / cm. ² Ask for. FIG. 3 is a plot of the moles per unit area of contaminants (chisso, sulfur) on the bonded surface and the bond shear strength of the bonded portion determined in this way. Triethanolamine (CH ₃ CH ₂ OH) ₃ A measurement obtained by adding N to the adhesive surface is plotted with a mark ●, and triethanolamine contains a contaminant (nitroso). Monoisopropanolamine CH as a cleaning agent ₃ CH (OH) CH ₂ NH ₂ Those measured by adding to the adhesive surface are plotted with ▲, and the monoisopropanolamine contains a contaminant (nitroso). Diethanolamine (CH ₃ CH ₂ OH) ₂ The measurement results obtained by adding NH to the adhesion surface are plotted with ■, and diethanolamine contains a contaminant (nitroso). Dodecanethiol CH as a cleaning agent ₃ (CH ₂ ) ₁₁ The measurement results obtained by adding SH to the adhesive surface are plotted with ♦, and the dodecanethiol contains a contaminant (sulfur). Thereafter, a straight line descending to the right is drawn along the plotted “●”, “▲”, “■”, “◆”. An approximation function representing a proportional relationship can be determined from this straight line.

As shown in FIG. 3, the moles per unit area of contaminants (nitrogen and sulfur) on the adhesive surface and the adhesive shear strength of the adhesive part are proportional as shown in the approximate function (straight line) shown in FIG. It has been found that moles affect not the type and amount of pollutants. The bond shear strength of the bonded portion is proportional to the moles of contaminants (nitrogen and sulfur) on the adhesive surface. When the mole of contaminants (nitrogen and sulfur) is 0.1 μmol / cm ² or less, the bond shear strength is 6 MPa. Predictive estimation can be made as follows. Preliminarily set an approximate function in which the moles of nitrogen and sulfur and the adhesive shear strength are in a proportional relationship, measure the amount of nitrogen and sulfur elements on the adhesion surface of the measurement object, convert them to moles, and measure the measurement results. It is necessary if the moles of nitrogen and sulfur, which are contaminants contained in the cleaning agent on the adhesive surface, are controlled below the specified amount by estimating the bond shear strength of the bonded part to be measured from the mole and the approximate function. adhesive shear strength can be obtained, Ru can manage adhesive shear strength of the silicone-based adhesive structure.

Claims (1)

A method for managing the adhesive shear strength of the adhesive portion of the silicone silicone was glued bonding structure, the adhesive surface nitrogen, and amount of elemental Io c, by measuring the adhesion shear strength of the adhesive portion, Preliminarily set an approximate function in which the moles of nitrogen and sulfur and the adhesive shear strength are in a proportional relationship, measure the amount of nitrogen and sulfur elements on the adhesion surface of the measurement object, convert them to moles, and measure the measurement results. The management method of the adhesive shear strength of the adhesive part in the silicone-based adhesive structure , wherein the adhesive shear strength of the adhesive part to be measured is estimated from the mole and the approximate function .

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