JP2011127739A - Sliding component, resin composition for molding sliding component, and spindle motor including the sliding component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive sliding component with excellent wear resistance of low halogen content; to provide a resin composition molding the sliding component; and to provide a spindle motor including the sliding component in a bearing mechanism. <P>SOLUTION: The sliding component is produced by the resin composition made by distributing a filler in polyphenylene sulfide resin. As a raw material resin composition of the sliding component, the composition includes at least both carbon fiber and glass fiber as the filler, addition of the filler is 50-64 mass% in total, and the halogen content in the resin composition is 900 ppm or less. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a sliding motor constituting a sliding part such as a bearing, a resin composition used for molding a required sliding part by injection molding, and a spindle motor provided with a bearing mechanism having the sliding part. And about.

  A recording disk drive device such as a hard disk drive device is provided with a spindle motor as a drive source of the recording disk, and the bearing mechanism of this spindle motor lubricates radial gaps and thrust gaps formed between the shafts. Fluid dynamic pressure bearings filled with oil are employed (see, for example, Patent Documents 1, 2, and 3).

  In Patent Document 1, as a bearing mechanism of such a spindle motor, a shaft, a cylindrical sleeve into which the shaft is inserted, a bottomed cylindrical sleeve housing into which the sleeve is inserted, and an annular disposed on the opening side of the sleeve And a thrust member disposed on the inner bottom surface of the sleeve housing, the sleeve is formed of a porous sintered metal, and the thrust member is formed of a synthetic resin material having low friction. ing. Further, Patent Document 1 also discloses a bearing mechanism in which the sleeve housing itself is formed of a low friction synthetic resin material and the thrust member is omitted.

  In Patent Document 2, a portion corresponding to the sleeve of the bearing mechanism disclosed in Patent Document 1, a portion corresponding to the sleeve housing, and a portion corresponding to the thrust member are integrally formed with a low-friction synthetic resin material. A bearing mechanism is disclosed. Patent Document 2 also discloses a technique using a polyphenylene sulfide resin (hereinafter, abbreviated as “PPS resin” in the present specification and drawings) as a low-friction synthetic resin material. Yes.

  Patent Document 3 discloses a resin in which at least a portion of a rotating body and a stationary body facing each other through a bearing gap is made of a PPS resin as a base resin and filled with a filler such as carbon fiber, carbon black, and an inorganic compound. Techniques for forming with compositions are disclosed.

JP 2009-156360 A JP 2009-017635 A JP 2007-085448 A

  By the way, the spindle motor provided in the recording disk drive device is required to have excellent high-speed rotation performance in order to further improve the recording density and increase the disk rotation speed. For this reason, the sliding members constituting the radial bearing surface and the thrust bearing surface of the shaft are required to have high dimensional accuracy and wear resistance as basic performance. With the trend toward lower prices, there is a strong demand for lower costs. In addition, sliding parts made of resin materials and resin compositions, which are used in electronic devices and electrical devices, have a halogen content in the resin of 900 ppm or less in order to suppress circuit deterioration. Its use is recommended by the Japan Electronic Circuits Association and the Electronic Equipment Technology Council. Such a technical problem is required to be solved not only for a spindle motor for a recording disk drive device, but also for all devices having sliding parts that slide at high speed with other parts.

  As described above, Patent Document 2 discloses a technique for forming a sliding member using a PPS resin, and Patent Document 3 discloses a sliding member using a resin composition having a PPS resin as a base resin. Techniques for molding are disclosed. As described in Patent Documents 2 and 3, PPS resin is advantageous as a base material for wear-resistant materials. However, not a little halogen compound, which is a by-product generated in the polymerization process, remains in the resin. is doing. A resin composition containing a PPS resin as a base resin is advantageous in that the wear resistance of the sliding member can be increased and the halogen content can be reduced as compared with the case where the PPS resin is used alone.

  However, since the sliding component described in Patent Document 3 uses only expensive carbon fibers as the fibrous filler filled in the PPS resin, it is expensive and can meet the demand for cost reduction. difficult. The technique described in Patent Document 3 is intended only to improve wear resistance, and the halogen content in sliding parts is 900 ppm or less recommended by the Japan Electronic Circuits Association or the Electronic Equipment Technology Council. No consideration is given to making it.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide a sliding component that is excellent in wear resistance and low in cost and has a low halogen content, and molding the sliding component. An object of the present invention is to provide a resin composition for carrying out the process and to provide a spindle motor provided with a sliding part in a bearing mechanism.

  In order to solve the above technical problem, the present invention relates to a sliding part formed of a resin composition in which a filler is dispersed in a PPS resin. The product includes at least both carbon fiber and glass fiber, the total amount of the filler added is 50 to 64% by mass, and the halogen content in the resin composition is 900 ppm or less.

  Further, the present invention relates to a sliding component, wherein the resin composition is a polyacrylonitrile-based (hereinafter referred to as “PAN-based” in the present specification and drawings) carbon fiber and glass fiber, which are the filler. And 30 to 50% by mass in total.

  Moreover, this invention made it the structure that the said resin composition contained 10-30 mass% polyacrylonitrile-type carbon fiber and 20-40 mass% glass fiber regarding sliding parts.

  Moreover, this invention made it the structure that the said resin composition contains the inorganic filler 4-20 mass% further as the said filler regarding a sliding component.

  Moreover, this invention made it the structure that the said inorganic filler was at least any one of a mica and potassium titanate fiber regarding a sliding component.

  On the other hand, regarding the resin composition, the present invention is a resin composition in which a filler is dispersed in a PPS resin, and includes at least both carbon fibers and glass fibers as the filler, and the amount of the filler added is The total content was 50 to 64% by mass, and the halogen content in the resin composition was 900 ppm or less.

  Further, regarding the spindle motor, the present invention relates to a spindle motor comprising a stator portion that is a fixed assembly, a rotor portion that is a rotary assembly, and a bearing mechanism that includes a shaft. It has the structure which has the sliding component which moves, and this sliding component is the sliding component in any one of Claims 1-5.

  According to the present invention, in the spindle motor, the sliding component is at least one of a thrust plate, a sleeve, and a sleeve housing.

  Since the sliding component and the resin composition of the present invention are formed by dispersing 50 to 64% by mass of a filler in the PPS resin, the sliding component and the resin are obtained using a PPS resin having a halogen content of 1800 ppm to 2500 ppm. The theoretical halogen content contained in the composition can be 900 ppm or less. In addition, since both carbon fiber and glass fiber are filled in the PPS resin, a part of expensive carbon fiber can be replaced with glass fiber, and the cost of sliding parts and resin composition can be reduced. can do. On the other hand, the spindle motor of the present invention is a resin composition in which a filler is dispersed in a PPS resin as a sliding component provided in the bearing mechanism, and includes at least both carbon fiber and glass fiber as the filler. The total amount of these fillers added is 50 to 64% by mass, and since a resin composition having a halogen content in the resin composition of 900 ppm or less is used, it can be manufactured at low cost and has durability. Can be increased.

It is sectional drawing which shows an example of the spindle motor applied to a recording disk drive device. It is sectional drawing which shows the 1st example of the bearing mechanism with which a spindle motor is equipped. It is sectional drawing which shows the 2nd example of the bearing mechanism with which a spindle motor is equipped. It is sectional drawing which shows the 3rd example of the bearing mechanism with which a spindle motor is equipped. It is a table | surface figure which compares and shows the composition of the resin composition which concerns on an Example, and the composition of the resin composition which concerns on a comparative example. It is a table | surface which compares and shows the characteristic of the sliding component and resin composition which concern on an Example, and the characteristic of the sliding component and resin composition which concerns on a comparative example.

  First, prior to the description of the sliding component and the resin composition according to the present invention, a configuration of a spindle motor for a recording disk drive device to which these are applied and a bearing mechanism provided therein will be described.

  As shown in FIG. 1, the spindle motor 10 of this example is an outer rotor type motor, and includes a stator portion 2 that is a fixed assembly, a rotor portion 3 that is a rotary assembly, and a bearing mechanism 4. The bearing mechanism 4 is provided with a shaft 41, and the rotor portion 3 attached to the upper end portion 413 of the shaft 41 is connected to the stator portion 2 around the central axis J <b> 1 of the motor 10 via the bearing mechanism 4. It is rotatably supported. Hereinafter, although the rotor part 3 side is described as the upper side and the stator part 2 side is the lower side along the central axis J1, the central axis J1 does not necessarily coincide with the direction of gravity. Note that reference numeral 11 in the drawing denotes a recording disk that is rotationally driven by the rotor unit 3.

  The rotor unit 3 includes a rotor hub 31 that is formed of stainless steel or the like and serves as a main body of the rotor unit 3, and a field magnet 32 that is attached to the rotor hub 31. The rotor hub 31 is attached to the upper end 413 of the shaft 41. In addition, a substantially disc-shaped disc portion 311 and a substantially cylindrical yoke 312 projecting downward from the outer periphery of the disc portion 311 are provided. The field magnet 32 is attached to the inner surface of the yoke 312.

  The stator portion 2 includes a base bracket 21 having a substantially cylindrical holder 211 at the center, and an armature 22 attached around the holder 211. The holder 211 has a bottomed cylindrical shape of a bearing mechanism 4 described later. A sleeve housing 43 is inserted and fixed. The armature 22 faces the field magnet 32 in the radial direction, and generates a rotational force that rotationally drives the shaft 41 with the field magnet 32.

  As shown in FIG. 2, the bearing mechanism 4 is disposed above the shaft 41, a cylindrical sleeve 42 into which the shaft 41 is inserted, a substantially bottomed cylindrical sleeve housing 43 into which the sleeve 42 is inserted, and the sleeve 42. And an annular seal member 44 and a thrust member 45 disposed on the inner bottom surface of the sleeve housing 43. The sleeve 42 is a porous member made of sintered metal, and the sleeve housing 43 and the seal member 44 play a role of holding the lubricating oil impregnated in the sleeve 42.

  A cylindrical shaft 41 arranged concentrically with the central axis J1 has an upper end protruding upward from the sleeve housing 43, and the rotor portion 3 is formed on the upper end of the shaft 41 protruding upward from the sleeve housing 43. A substantially disk-shaped disk portion 311 is attached by press-fitting or the like. The lower end portion 411 of the shaft 41 has a spherical shape that is convex downward (that is, toward the thrust member 45), and an outer peripheral surface in the vicinity of the lower end portion 411 has an annular shape centered on the central axis J1. The retaining member 412 is attached. The outer surface of the sleeve 42 is fixed in the sleeve housing 43, the inner surface of the sleeve 42 supports the shaft 41 in the radial direction via the lubricating oil, and the lower surface 421 of the sleeve 42 is a retaining member attached to the shaft 41. It faces the upper surface 4121 of 412. Between the upper surface 4121 of the retaining member 412 and the lower surface 421 of the sleeve 42, an axial gap 46 of 10 to 40 μm corresponding to a width in which the shaft 41 can move in the axial direction with respect to the sleeve housing 43 is formed. The shaft 41 is prevented from coming out of the sleeve 42 by the upper surface 4121 of the retaining member 412 and the lower surface 421 of the sleeve 42 coming into contact with each other even when the shaft 41 moves upward.

  The sleeve housing 43 has a cylindrical side portion 431 and a substantially dish-shaped bottom portion 432, and is formed as one continuous member by pressing a plate member made of spring steel. The bottom portion 432 includes a substantially annular stepped portion 4321 extending inward from the lower end portion of the side portion 431 toward the central axis J1, and a bottomed cylindrical thrust member holding portion 4322 in which the upper end portion is continuous with the inner edge of the stepped portion 4321. Have.

  The thrust member 45 is formed in a substantially disk shape with a resin composition in which a filler is dispersed in PPS resin, and is formed on the lower end portion 411 of the shaft 41 on the upper surface (the surface facing the shaft 41). A spherical recess having a curvature substantially equal to the spherical surface formed is formed. The thrust member 45 is disposed in the thrust member holding portion 4322 of the sleeve housing 43 and functions as a pivot bearing that receives a force in the thrust direction of the shaft 41.

  Next, another configuration example of the bearing mechanism provided in the spindle motor for the recording disk drive device will be described. In the example of FIGS. 1 and 2, a bottomed cylindrical sleeve housing 43 is formed using a metal material, and the bottom of the sleeve housing 43 is formed with a resin composition in which a filler is dispersed in PPS resin. In the example of FIG. 3, the sleeve housing 43 itself is formed of a resin composition obtained by dispersing a filler in PPS resin, and the member corresponding to the thrust member 45 is omitted. ing. In the example of FIG. 4, a portion corresponding to the sleeve 42 and the sleeve housing 43 is integrally formed with a resin composition obtained by dispersing a filler in PPS resin, and a member corresponding to the sleeve 42 and the thrust member 45. Is omitted. In the present specification, parts formed with a resin composition in which a filler is dispersed in these PPS resins are referred to as “sliding parts”. The sliding part is generally manufactured by injection molding, but can of course be manufactured by cutting or other processing methods.

  Hereinafter, embodiments of the sliding component and the resin composition according to the present invention will be described.

  Needless to say, the sliding parts are required to have a low dynamic friction coefficient, excellent wear resistance, high fluidity and excellent moldability, and low cost. In addition to this, a sliding component applied to an electronic device or an electric device is required to have a low halogen content such as chlorine or bromine in order to prevent or suppress deterioration of the circuit. The halogen content is recommended to be 900 ppm or less by the Japan Electronic Circuits Association and the Electronic Equipment Technical Council.

  The sliding component according to the embodiment includes at least carbon fiber (in the drawing of the present application, this is expressed as “CF”) and glass fiber (in the drawing of the present application, this is expressed as “GF”) in the PPS resin. Are molded with a resin composition in which a total of 50 to 64% by mass of a filler containing both of the above is dispersed.

  When a PPS resin having a halogen content of 1800 ppm or less is used, the theoretical halogen content contained in the sliding component (the halogen content in the PPS resin is added by adding a filler of 50% by mass or more to the PPS resin. X The filling rate of the packing) can be 900 ppm or less recommended by the Japan Electronic Circuit Industry Association or the Electronic Equipment Technology Council. Further, when a PPS resin having a halogen content of 2500 ppm or less is used, the theoretical halogen content contained in the sliding component is set to 900 ppm or less by adding a filler of 64% by mass or more to the PPS resin. be able to. On the other hand, if the filling rate of the filler added to the PPS resin exceeds 64% by mass, the fluidity of the resin composition decreases and the molding processability of the molded product is impaired. By controlling the content to 64% by mass or less, good moldability can be maintained. Further, since glass fiber is less expensive than carbon fiber, by adding carbon fiber and glass fiber as fillers in the PPS resin, the sliding component is equivalent to the amount of carbon fiber replaced with glass fiber. The cost can be reduced. Of course, the carbon fiber and glass fiber for increasing the strength were added in an appropriate amount to the matrix of the PPS resin excellent in mechanical properties such as strength, elastic modulus, creep properties and fatigue properties and precision moldability. Abrasion and dynamic friction coefficient.

  There are two types of carbon fibers: PAN based on acrylic long fibers, and pitch based on coal tar and petroleum pitch, but because of high strength and excellent wear resistance, PAN based carbon fibers It is particularly desirable to use it.

  In addition, glass fiber has the effect of improving the dimensional stability and tensile strength of the molded product, so that the cross-sectional shape when cut along a plane perpendicular to the length direction is circular (the deformed ratio (cross-section ratio)). It is particularly desirable to use a material having an aspect ratio exceeding 1 than that having an aspect ratio of 1].

  The total content of carbon fibers and glass fibers in the resin composition is desirably 30 to 50% by mass. When the content is less than 30% by mass, the content of other fillers becomes excessively high, and the wear resistance and mechanical strength of the sliding parts are insufficient. When the content exceeds 50% by mass, the fluidity of the resin composition decreases. This is because the moldability of the molded product is impaired. Further, the glass fiber content in the resin composition is desirably higher than the carbon fiber content in the resin composition in order to achieve cost reduction of an effective sliding member. From this, the content rate of the carbon fiber in a resin composition shall be 10-30 mass%, and the content rate of glass fiber shall be 20-40 mass%.

  Furthermore, other fillers can be added to the matrix of the PPS resin along with the carbon fibers and glass fibers. Examples of other fillers include inorganic substances such as mica or potassium titanate fibers that improve moldability, and organic substances such as glycidyl methacrylate that improve impact resistance. The inorganic content is preferably 4 to 20% by mass, and the organic content is preferably 0 to 2% by mass. When the inorganic content is less than 4% by mass, the fluidity of the resin composition is insufficient, and when it exceeds 20% by mass, the filling amount of carbon fiber and glass fiber is insufficient, and the wear resistance and mechanical strength are impaired. Because it is.

FIG. 5 shows the composition of the resin composition according to Example 1-9 and the resin composition according to Comparative Example 1-7. Moreover, in FIG. 6, the characteristic of the sliding component and resin composition which concern on each Example and each comparative example is shown. In each of these Examples and Comparative Examples, a linear PPS resin LC-5G manufactured by Dainippon Ink and Chemicals, Inc. (melting temperature 310 ° C., melt viscosity 280 Pa · s at a shear rate of 10 ³ S ⁻¹⁾ is used as the PPS resin. , PAN-based carbon fiber HM35-C6S manufactured by Toho Tenax Co., Ltd. (fiber diameter: 7 μm, average fiber length: 6 mm, tensile strength: 3240 MPa), and Nitto as glass fiber. CSG 3PA-820 (cut length: 3 mm, profile ratio: 4) manufactured by Spinning Co., Ltd. was used. Further, AB-25S from Yamada Mica Industry was used as mica, and Tismo (registered trademark) D from Otsuka Chemical Co., Ltd. was used as potassium titanate fiber.

  As shown in FIG. 6, the properties of the sliding parts and the resin composition according to Example 1-9 and Comparative Example 1-7 are evaluated as follows: wear amount, dynamic friction coefficient, moldability (fluidity), resin composition The theoretical chlorine amount and cost were measured. The dynamic friction coefficient was measured using a ball-on-disk wear tester μ3000 manufactured by Takachiho Seiki Co., Ltd. The test conditions were as follows: a test piece having a side length of 35 mm and a thickness of 3.5 mm, a test sphere diameter of 3 mm, a test ball pressing position at a radius of 10 mm from the center of rotation of the test piece, and a test load. The value when the pressure of the test ball against the surface of the test piece was 5 N and the test piece was rotationally driven at 500 rpm for 10 minutes was measured. Regarding the amount of friction, the depth of the press mark of the test ball on the surface of the test piece on which the dynamic friction coefficient measurement test was performed was measured with a surface roughness measuring machine SURFCOM 130A of Tokyo Seimitsu Co., Ltd. Regarding molding processability, a thrust member 45 (see FIGS. 1 and 2) having a diameter of 8.0 mm and a thickness of 1.0 mm was injection-molded and visually evaluated for defects in appearance. The theoretical chlorine content was calculated from the chlorine content of the PPS resin used and the filling rate of the packing material. The cost is shown by comparison with the cost of the most expensive resin composition according to Comparative Example 1.

  In addition, the quality of each evaluation item was determined according to the following criteria. That is, with respect to the wear amount, 10 μm or less was regarded as a good product and a product exceeding 10 μm was regarded as a defective product. Regarding the coefficient of dynamic friction, a value of 0.3 or less was regarded as a non-defective product, and a value exceeding 0.3 was regarded as a defective product. Regarding molding processability (fluidity), a product with no appearance defect was regarded as a non-defective product (◯ mark), and a product with an appearance defect was regarded as a defective product (× mark). Regarding the theoretical chlorine content in the resin composition, 900 ppm or less, which is the recommended value of the Japan Electronic Circuits Association and the Electronic Equipment Technology Council, was determined to be a non-defective product, and a product exceeding 900 ppm was determined to be a defective product. As for the cost, compared with the resin composition according to Comparative Example 1, a product that can be reduced by 25% or more is regarded as a non-defective product, and a product whose cost reduction effect is less than 25% is regarded as a defective product.

  As is clear from FIG. 6, the resin composition according to Comparative Example 1 does not reach the evaluation standard with respect to molding processability and cost. The resin composition according to Comparative Example 2 does not reach the evaluation standard with respect to the theoretical chlorine amount and cost. The resin composition according to Comparative Example 3 does not reach the evaluation standard for the dynamic friction coefficient and the theoretical chlorine content. The resin composition according to Comparative Example 4 does not reach the evaluation standard with respect to the wear amount and the theoretical chlorine amount. The resin composition according to Comparative Example 5 does not reach the evaluation standard with respect to the wear amount, the theoretical chlorine amount, and the cost. The resin composition which concerns on the comparative examples 6 and 7 has not reached evaluation criteria about an abrasion amount and cost.

  On the other hand, it can be seen that the resin composition according to Example 1-9 satisfies all the evaluation criteria and is suitable as a raw material of the sliding component according to the present invention.

  In the present embodiment, the sliding member provided in the bearing mechanism of the spindle motor for the recording disk drive device has been described as an example. However, the gist of the present invention is not limited to this, and other arbitrary sliding members are provided. It can be applied to a sliding member applied to the moving part.

  The present invention can be used for a sliding part provided in a bearing mechanism of a motor.

DESCRIPTION OF SYMBOLS 10 Spindle motor 11 Recording disk 2 Stator part 21 Base bracket 211 Holder 22 Armature 3 Rotor part 31 Rotor hub 311 Disk part 312 Yoke 32 Field magnet 4 Bearing mechanism 41 Shaft 411 Shaft lower end part 412 Stopping member 43 Sleeve housing 44 Seal member 45 Thrust member 46 Axial gap

Claims (8)

In the sliding part formed by the resin composition in which the filler is dispersed in the polyphenylene sulfide resin,
The resin composition contains at least both carbon fibers and glass fibers as the filler, the total amount of the filler added is 50 to 64% by mass, and the halogen content in the resin composition is 900 ppm or less. Sliding parts characterized by being   2. The sliding component according to claim 1, wherein the resin composition contains a total of 30 to 50 mass% of polyacrylonitrile-based carbon fibers and glass fibers as the filler. 3.   The sliding component according to claim 2, wherein the resin composition contains 10 to 30% by mass of polyacrylonitrile-based carbon fiber and 20 to 40% by mass of glass fiber.   The sliding component according to claim 1, wherein the resin composition further contains 4 to 20% by mass of an inorganic filler as the filler.   The sliding component according to claim 4, wherein the inorganic filler is at least one of mica and potassium titanate fibers.   A resin composition in which a filler is dispersed in a polyphenylene sulfide resin, the filler including at least both carbon fiber and glass fiber, and the total amount of the filler added is 50 to 64% by mass, The resin composition, wherein a halogen content in the resin composition is 900 ppm or less. In a spindle motor comprising a stator portion that is a fixed assembly, a rotor portion that is a rotating assembly, and a bearing mechanism that includes a shaft,
6. The spindle motor according to claim 1, wherein the bearing mechanism has a sliding component that slides with the shaft, and the sliding component is the sliding component according to any one of claims 1 to 5. .   The spindle motor according to claim 7, wherein the sliding component is at least one of a thrust plate, a sleeve, and a sleeve housing.

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