JP2007051763A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device excellent in low water absorbing property and calcium chloride resistance, and sufficiently enduring in use in snowy areas. <P>SOLUTION: This bearing device is provided with an outer ring correspondence member having an outer ring raceway on an inner peripheral surface and not rotated at the time of usage, an inner ring correspondence member having an inner ring raceway on an outer peripheral surface confronting the inner peripheral surface of the outer ring correspondence member and rotated at the time of usage, a plurality of rolling elements arranged so as to be freely rolled between the outer ring raceway and the inner ring raceway, an encoder for detecting rotation fixed on the corresponding member to the inner ring and a synthetic resin cover including low water absorbing resin and fixed on an outer ring aperture. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bearing device including an encoder that detects the number of rotations of a rotating body.

  In recent years, an increasing number of automobiles are equipped with a rotational speed detection device used for anti-skid for preventing skid or for traction control for effectively transmitting driving force to a road surface. In an automobile equipped with such a rotational speed detection device, a bearing device for a wheel that incorporates a sensor for detecting the rotational speed of a wheel necessary for control is generally used. A rolling bearing unit 1 for supporting a driven wheel in an independent suspension as shown in FIG.

  In the illustrated rolling bearing unit 1, the rolling element 2 includes a rolling groove 4 a formed in the hub 3, a rolling groove 4 b of the inner ring 6 that is caulked by the caulking part 5 at the end of the hub 3, and an outer ring 7. It is held in a space formed by the rolling grooves 8a and 8b facing the rolling grooves 4a and 4b via a cage 9 so as to be freely rollable. A gap between the hub 3 and the outer ring 7 on the mounting flange 15 side is sealed by a seal ring 17. In addition, an encoder 12 is fixed to the end of the inner ring 6 by attaching a magnet portion 11 to a slinger 10. The magnet portion 11 of the encoder 12 is made of an elastic magnetic material obtained by mixing magnetic powder into an elastic material such as rubber or resin, and is magnetized in multiple directions in the circumferential direction. The slinger is substantially cylindrical and has a substantially L-shaped cross-sectional shape that curves outward at a position protruding from the side end face of the inner ring 6 and further bends to the axial side. A sensor 13 is disposed at a position facing the magnet unit 11 of the encoder 12 with a predetermined gap, and the rotational speed of the inner ring 6 is detected by detecting a magnetic pulse from the magnet unit 11. The sensor 13 is fixed to the cover 14. The cover 14 is a lid member that is mounted so as to cover the opening surrounded by the outer ring 7, and the sensor 13 is fixed in a state of being inserted into the through hole 14a. Furthermore, an O-ring 16 is inserted into the engagement end with the outer ring 7 so that water and foreign matter do not enter from the outside.

  The cover 14 is mainly made of metal, but a resin-made cover is increasingly used because of high manufacturing costs and difficulty in forming the cover 14 into a complicated shape. For example, a cover made of polyamide 66 (see Patent Document 1), a cover made of polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyamide (PA) based synthetic resin (see Patent Document 2), and the like are known. .

JP 2005-30427 A JP 2004-44664 A

  Automobiles are used outdoors, and are in contact with rainwater and muddy water when running in the rain, and wash water when washing, so the cover is required to have water resistance and chemical resistance. Specific resin is used. In addition, automobiles are used in various places and areas. For example, automobiles may come into contact with water containing seawater in coastal areas, and may come into contact with water containing snow melting agent in snowy regions. The snow melting agent contains calcium chloride, and when the water containing calcium chloride penetrates into the cover, only water is removed during drying, and calcium chloride accumulates in the cover. In polyamide-based resins, strength develops due to hydrogen bonding of amide groups, but when calcium chloride hydrate is present, hydrogen bonding of amide groups is broken, cracking occurs in the cover due to the occurrence of microcrazes and progress, or in the worst There is a risk of destruction.

  As described above, it is not sufficient for the resin cover to have low water absorption, and resistance to a snow melting agent (calcium chloride) may be required, and the above-described resin covers cannot be used. Accordingly, an object of the present invention is to provide a highly reliable bearing device that is excellent in resistance to calcium chloride in addition to low water absorption, and can sufficiently withstand use in a snowy region.

In order to achieve the above object, the present invention provides the following bearing device and wheel bearing.
(1) An outer ring equivalent member that has an outer ring raceway on the inner peripheral surface and does not rotate during use, and an inner ring equivalent member that has an inner ring raceway on an outer peripheral surface facing the inner peripheral surface of the outer ring equivalent member and rotates during use. A plurality of rolling elements provided between the outer ring raceway and the inner ring raceway so as to be freely rollable, a rotation detection encoder fixed to the inner ring equivalent member, and a synthetic resin fixed to the outer ring opening. A bearing device comprising a cover made of plastic, wherein the synthetic resin cover contains a low water-absorbing resin.
(2) The bearing device according to (1), wherein the low water-absorbent resin is an aliphatic polyamide resin in which the alkylene group in the repeating unit has 7 or more carbon atoms.
(3) The bearing device according to (1), wherein the low water-absorbing resin is an aromatic polyamide resin.
(4) The resin cover contains 60 to 80% by mass of polyamide 66 resin, 15 to 25% by mass of amorphous aromatic polyamide resin, and 5 to 15% by mass of low water-absorbing aliphatic polyamide resin. The bearing device according to the above (1), comprising 45 to 80% by mass of a resin component and 20 to 55% by mass of glass fiber.
(5) The bearing device according to (4), wherein the low water-absorbing aliphatic polyamide resin is at least one selected from polyamide 12 resin, polyamide 11 resin, polyamide 612 resin, and polyamide 610 resin.
(6) The synthetic resin cover is formed by integrally forming a metal attachment member for fixing to the outer ring, as described in any one of (1) to (5) above Bearing device.
(7) A wheel bearing comprising the bearing device according to any one of (1) to (6) above.

  The bearing device of the present invention is provided with a cover made of a specific resin that is excellent in resistance to calcium chloride in addition to strength, heat resistance, and low water absorption. It is particularly effective as a bearing. Further, since the cover is made of resin, it can be efficiently molded by injection molding or the like, and can be easily molded into a complicated shape.

  Hereinafter, the present invention will be described in detail.

  The present invention is characterized in that, in a bearing device configured to include a rotation speed detection device and a cover for sealing an outer ring opening, the cover is formed of a material containing a low water absorption resin. is there. Therefore, as long as the rotational speed detection device and the cover are provided, the configuration of the bearing device is not limited. For example, a rolling bearing unit for supporting a driven wheel of an automobile as shown in FIG. The cover 14 is formed of a resin composition containing resin as a resin component. By using the low water-absorbent resin, water containing a snow melting agent can be prevented from penetrating into the cover 14, and as a result, accumulation of calcium chloride can be prevented.

  As the low water-absorbent resin, an aliphatic polyamide resin or an aromatic polyamide resin in which the alkylene group in the repeating unit has 7 or more carbon atoms is preferable. Specifically, examples of the aliphatic polyamide resin include polyamide 11 resin (PA11), polyamide 12 resin (PA12), polyamide 610 resin (PA610), polyamide 612 resin (PA612), and the like. For reference, the water absorption rate (ASTM D570) of these polyamide resins when immersed in water at 23 ° C. for 24 hours is shown, all of which are 0.5% by mass or less.

  On the other hand, examples of the aromatic polyamide resin include a modified polyamide resin having an aromatic ring introduced, such as polyamide MXD6 (PAMDX6).

  These aliphatic polyamide resins and aromatic polyamide resins can be used by blending a plurality of types.

  Further, as the resin component, the above-mentioned aliphatic polyamide resin and aromatic polyamide resin are preferably used alone, but a highly water-absorbing polyamide resin such as polyamide 6, polyamide 66 or polyamide 46 may be used in combination. Highly water-absorbent polyamides generally have advantageous properties for heat resistance and mechanical strength, and mixing these in appropriate amounts increases the heat resistance and mechanical properties of the entire cover.

  Commercially available products can be used for the aliphatic polyamide resins and aromatic polyamide resins listed above. For example, “Rilsan” manufactured by Toray Industries, Inc. as polyamide 11 and “Dilcel” manufactured by Daicel Corporation as “polyamide 12”. Tegusa "etc. can be obtained. As aromatic polyamides, "Zytel HTN" manufactured by DuPont Co., Ltd., "Gripoly" manufactured by MMS Showa Denko Co., Ltd., "Genesta" manufactured by Kuraray Co., Ltd., "Aalen" manufactured by Mitsui Chemicals, Inc., and Solvay Advanced "Amodel" manufactured by Polymers Co., Ltd. and "Lenny" manufactured by Mitsubishi Engineering Plastics Co., Ltd. are available. In addition, “Ube Nylon” manufactured by Ube Industries, Ltd. and “Amilan” manufactured by Toray Industries, Inc. are used as polyamide 6, and “Ube Nylon” manufactured by Ube Industries, Ltd., “Zytel” manufactured by DuPont Co., Ltd., and polyamide 46 are used as polyamide 66. "Stanyl" manufactured by DSM Japan Engineering Plastics Co., Ltd. is available.

  It is preferable to add a reinforcing material to the resin composition in order to increase the mechanical strength of the cover 14 and suppress dimensional changes. The reinforcing material is preferably a fiber such as glass fiber, carbon fiber, potassium titanate whisker, aluminum borate whisker, or a particulate filler such as whisker, calcium carbonate, and has an adhesive property with the polyamide resin as a resin component. In view of this, a surface treatment with a silane coupling agent or the like is more preferable. Moreover, these reinforcing materials can be used in combination of multiple types.

  Among these, glass fiber is preferable. Further, the thinner glass fibers have a larger number of fibers even at the same content, resulting in a higher reinforcing effect and further improved orientation in the resin. However, if it is too thin, the reinforcing effect is reduced. Therefore, it is preferable to use glass fibers having a diameter of 5 to 15 μm, preferably 5 to 9 μm, more preferably 6 to 8 μm. Moreover, it is preferable that the fiber length of glass fiber is 100-900 micrometers, More preferably, it is 300-600 micrometers. When the fiber length is less than 100 μm, the fiber length is too short, and the reinforcing effect and the size suppressing effect are small. When the fiber length exceeds 900 μm, the reinforcing effect and the dimensional restraining effect are improved, but it is assumed that the fiber is broken in the resin part forming step and the forming accuracy is deteriorated due to the decrease in orientation.

  10-60 mass% is preferable and, as for the compounding quantity of the reinforcing material in a resin composition, 20-50 mass% is more preferable. When the blending amount is less than 10% by mass, the reinforcing effect is not exhibited. When the blending amount exceeds 60% by mass, the fluidity of the resin composition is lowered and the moldability is lowered, and it becomes impossible to cope with the injection molding having excellent moldability. .

  As another embodiment of the resin composition, the polyamide 66 resin is 60 to 80% by mass, the amorphous aromatic polyamide resin is 15 to 25% by mass, and the low water-absorbing aliphatic polyamide resin is 5 to 15% by mass. What mixed 45-80 mass% of resin components to contain and 20-55 mass% of glass fiber can also be used. When the polyamide 66 resin is less than 60% by mass, the content of the relatively low water-absorbing aliphatic polyamide resin can be increased, so that the calcium chloride resistance can be improved, but the heat resistance and fatigue resistance are reduced. It is not preferable. On the other hand, when the polyamide 66 resin exceeds 80% by mass, the content of the relatively low water-absorbing aliphatic polyamide decreases, and the intended calcium chloride resistance cannot be obtained. Further, when the glass fiber is less than 20% by mass of the total amount of the fat composition, the reinforcing effect is small, and when it exceeds 55% by mass, not only fluidity suitable for injection molding is obtained, but also it is difficult to mold with high accuracy. Become.

  The polyamide 66 resin preferably has a number average molecular weight of 13,000 to 30000 in view of injection moldability, and more preferably has a number average molecular weight of 18000 to 25000 in consideration of fatigue resistance and high molding accuracy. When the number average molecular weight is less than 13,000, the molecular weight is too low, the fatigue resistance is low, and there is no practicality. On the other hand, when the number average molecular weight exceeds 30000, fatigue resistance is improved. However, when a specified amount of glass fiber is contained in order to achieve mechanical strength such as impact strength necessary for the cover, the melt viscosity at the time of molding. It becomes difficult to manufacture with high accuracy by injection molding.

  As the low water-absorbing aliphatic polyamide resin, the above-mentioned polyamide 12 resin, polyamide 11 resin, polyamide 612 resin and polyamide 610 resin are preferable, and these are used alone or in combination.

  The amorphous aromatic polyamide is blended in order to make the polyamide 66 resin and the low water-absorbing aliphatic polyamide resin compatible. As this amorphous aromatic polyamide resin, a modified polyamide 6T / I having a basic skeleton of polyamide 6T / 6I, which is a polycondensate of hexamethylenediamine, terephthalic acid and isophthalic acid, and further forming an aliphatic polyamide portion in the molecule. 6I can be preferably used. Examples of the monomer for forming the aliphatic polyamide portion include 6-aminocaproic acid, 12-aminododecanoic acid, ε-caprolactam, laurolactam, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, and the like. Can be suitably used. Among these, when carbon 6 and carbon number 12 are used in combination, the molecular structure is similar to that of the polyamide 66 resin and the preferable low water-absorbing aliphatic polyamide resin, and the compatibility is further improved. .

  As the glass fiber, those having the above-described fiber diameter and fiber length can be suitably used. If necessary, a part thereof may be replaced with another fibrous reinforcing material such as carbon fiber or a whisker-like reinforcing material such as potassium titanate whisker.

  The resin composition is configured as described above, and various additives can be added as necessary.

  For example, since it is assumed that pebbles and the like from the road surface collide with each other during traveling, the cover 14 is preferably provided with impact resistance by blending an elastomer with the resin composition. Examples of the elastomer include ethylene propylene non-conjugated diene (EPDM) rubber and urethane rubber, and 2 to 15% by mass of the total amount of the resin composition is blended.

  Also, in order to improve the heat dissipation of the resin part, a high thermal conductive filler having a thermal conductivity of 10 W / m · K or more, specifically, alumina, magnesia, aluminum nitride, silicon carbide, beryllia, graphite, etc. It may be added.

  Furthermore, in order to reduce the unevenness of the cover 14 or to further improve the wear resistance, a particulate filler, specifically, calcium carbonate, clay, talc, silica, wollastonite or the like may be added. Good. As the particulate filler, if the above-described highly thermally conductive filler is also particulate, the same effect is obtained.

  In addition, in order to prevent deterioration due to heat during molding and use, it is preferable to add an iodide heat stabilizer and an amine antioxidant to the resin, either alone or in combination. Further, a colorant or the like may be added.

  In order to manufacture the cover 14, the above resin composition may be formed into a predetermined shape according to a normal resin molding method. The resin composition is obtained by kneading a resin component, a reinforcing material, an elastomer, a resin additive and the like according to a conventional method. Various molding methods are possible, but injection molding is preferable from the viewpoint of productivity.

  2 is a cross-sectional view showing another example of the bearing device, and shows an example in which the cover 14 is changed in the rolling bearing unit 1 shown in FIG. In addition, there is no change in other members, the same code | symbol is attached | subjected and description is abbreviate | omitted. In the figure, the cover 14 has a structure in which an attachment member 20 for mounting to the outer ring 7 is integrally formed. The mounting member 20 is a cylindrical member made of metal such as stainless steel, and the tip portion is bent outward at a substantially right angle, and the above resin composition is molded so as to surround the bent portion. . In order to strengthen the bonding between the cover 14 and the mounting member 20, the surface of the bent portion of the mounting member 20 may be roughened, or a suitable adhesive may be baked. Further, the outer diameter of the mounting member 20 matches the inner diameter of the outer ring 7, and the cover 14 is fixed to the outer ring 7 by fitting the outer peripheral surface of the mounting member 20 into the inner wall of the outer ring 7. Since the metal has little settling due to aging, the cover 14 including the mounting member 20 is stably fixed to the outer ring 7 for a long period of time.

  The mounting member 20 is not limited to the above, and various shapes are possible as long as the mounting member 20 includes a mounting portion to the outer ring 7 and a joint portion with the cover 14.

  In the bearing device shown in FIGS. 1 and 2, a through hole 14 a is provided in the cover 14, and the sensor 13 is inserted through the through hole 14 a so as to face the encoder 12. Instead of this, as shown in FIG. 3, the sensor 13 and the encoder 12 may be opposed to each other without providing the through hole 14 a in the cover 14. However, the magnetic force from the encoder 12 decreases as the sensor 13 and the encoder 12 are separated from each other. On the other hand, in order to make the sensor 13 and the encoder 12 approach each other, the thickness of the cover 14 may be reduced. However, if the entire thickness is reduced uniformly, the strength is reduced. Therefore, as shown in the drawing, a recess 14b having a size capable of accommodating the tip of the sensor 13 is provided on the outer surface of the cover 14, and the tip of the sensor 13 is accommodated in the recess 14b. Thereby, the distance between the sensor 13 and the encoder 12 is shortened, and the decrease in sensitivity can be suppressed while maintaining the strength. Further, when the bearing device is assembled, the positioning of the sensor 13 is facilitated.

The following examples further clarify the present invention.
(Examples 1-4, Comparative Examples 1-2)
As a resin composition for a cover, glass fiber 30% by weight containing polyamide 66 (Comparative Example 1), glass fiber 30% by weight containing polyamide 6 (Comparative Example 2), and a resin obtained by mixing polyamide 66 and polyamide 612 in an equivalent amount. What was blended so as to be 33% by mass of the total amount (Example 1), glass fiber 30% by mass-containing polyamide 12 (Example 2), glass fiber 35% by mass-containing polyamide MXD6 (Example 3), polyamide MXD6 and glass A fiber (Example 4) was prepared by blending the fibers so that the total amount was 15% by mass and the EPDM rubber was 5% by mass. And the disk-shaped test piece of diameter 30mm and thickness 2mm was produced from each resin composition. The prepared test piece was left in a constant temperature and humidity chamber (50 ° C., 80% RH) for 24 hours, and the weight difference before and after being left was determined as the water absorption rate. The results are shown in Table 1.

  From Table 1, it can be seen that the low water-absorbing polyamide resin used in the present invention has a water absorption of less than half that of polyamide 6 and polyamide 66, and exhibits low water absorption.

  Further, a stainless steel plate was pressed into a cylindrical shape as shown in FIG. 2 and provided with a bent portion, and the above resin composition was injection molded using the bent portion as a core to prepare a cover. And after leaving each cover in a constant temperature and humidity chamber (50 ° C., 80% RH) for 10 hours, immersing in a 10% aqueous solution of calcium chloride for 1 minute and then drying at 80 ° C. for 1 hour, The cover surface was observed with a 10-fold optical microscope for each cycle, and the number of cycles was determined until cracks occurred. The upper limit of the number of cycles was 50, and the cycle was terminated when it reached 50. The results are shown in Table 2.

  From Table 2, it can be seen that the cover made of the resin composition according to the present invention is excellent in durability because accumulation of calcium chloride is suppressed. From this, it can be said that the bearing device of the present invention is suitable as a bearing for automobile wheels used in a snowfall region where a snow melting agent is used.

(Example 5)
Polyamide 66 (“UBE Nylon 2020U” manufactured by Ube Industries, Ltd., number average molecular weight 20,000, containing copper iodide-based additive) 72% by mass (however, 46.8% for the total amount of resin and glass fiber) %), Amorphous aromatic polyamide (modified polyamide 6T / 6I, "Grivory G21" manufactured by Ms Chemi Japan) 20% by mass (however, 13% by mass with respect to the total amount of resin and glass fiber) , Low water-absorbing aliphatic polyamide (polyamide 12, “UBE nylon 3014U” manufactured by Ube Industries, Ltd., number average molecular weight 14000, containing hindered phenol antioxidant) 8% by mass (however, the total of resin and glass fiber) The resin material was prepared by mixing (5.2% by mass with respect to the amount). 65% by mass of this resin material and a fiber diameter of 13 μm (that is, an average diameter of 13 μm and a diameter of 12 to 14 μm) of glass fiber (amino group-containing silane coupling agent-treated product) at a ratio of 35% by mass The resin composition was obtained by kneading. The resin composition was injection molded to obtain a cover having the shape shown in FIG.

(Example 6)
As polyamide 66, “UBE nylon 2026U” manufactured by Ube Industries, Ltd. having an average molecular weight of 26000 was used, and the glass fiber was replaced with a fiber diameter of 6 μm (that is, an average diameter of 6 μm and a diameter of 5 to 7 μm). Obtained a cover in the same manner as in Example 5.

(Comparative Example 3)
Glass fiber-containing polyamide 66 ("UBE nylon 2020GU6" manufactured by Ube Industries, Ltd., containing a number average molecular weight of 20,000, containing a copper iodide-based additive, containing 30% by mass of glass fiber treated with a silane coupling agent having a diameter of 13 μm) The cover was obtained in the same manner.

[Water absorption measurement]
A resin material is prepared with the same composition as the examples and comparative examples, a disk-shaped test piece having a diameter of 30 mm and a thickness of 2 mm is formed, and the test piece is placed in a constant temperature and humidity chamber at 50 ° C. and 80% RH. It was allowed to stand for a period of time, and the weight difference before and after being left as the water absorption rate. The results are shown in Table 3.

[Calcium chloride resistance evaluation]
The cover is immersed in hot water at 80 ° C. for 2 hours to absorb water, and then immersed in a 50% aqueous solution of calcium chloride for 5 minutes. Next, the following treatment was performed in a thermostatic bath in a state where the cover after immersion was subjected to a radial load of 150 kgf. That is, the temperature was raised from 20 ° C. to 110 ° C. over 30 minutes and then held at 110 ° C. for 2 hours, and then the temperature was lowered to 20 ° C. over 30 minutes and then kept at 20 ° C. for 1 hour, The cover is immersed in a 50% aqueous solution of calcium chloride for 5 minutes every two cycles. After repeating this for 10 cycles, it was confirmed whether cracks were generated. The results are shown in Table 3.

[Mechanical strength evaluation]
Resin materials were prepared with the same composition as the examples and comparative examples, and test pieces were separately molded. And bending strength was measured according to ASTM D-790. The results are shown in Table 3.

  As is apparent from Table 3, according to the present invention, a cover comprising a resin composition in which glass fiber is mixed with a resin containing polyamide 66, amorphous aromatic polyamide, and low water-absorbing aliphatic polyamide is It can be seen that both the properties of calcium and bending strength are expressed in a well-balanced manner.

It is sectional drawing which shows an example of the bearing apparatus of this invention. It is sectional drawing which shows the other example of the bearing apparatus of this invention. It is sectional drawing which shows the further another example of the bearing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing unit 2 Rolling element 3 Hub 6 Inner ring 7 Outer ring 9 Cage 12 Encoder 13 Sensor 14 Cover 20 Mounting member

Claims (7)

An outer ring equivalent member that has an outer ring raceway on the inner peripheral surface and does not rotate during use, an inner ring equivalent member that has an inner ring raceway on an outer peripheral surface facing the inner peripheral surface of the outer ring equivalent member, and that rotates during use, and the outer ring A plurality of rolling elements provided between a raceway and the inner ring raceway, a rotation detecting encoder fixed to the inner ring equivalent member, and a synthetic resin cover fixed to the outer ring opening. A bearing device comprising:
The synthetic resin cover includes a low water-absorbing resin.   2. The bearing device according to claim 1, wherein the low water-absorbent resin is an aliphatic polyamide resin in which an alkylene group in the repeating unit has 7 or more carbon atoms.   The bearing device according to claim 1, wherein the low water-absorbing resin is an aromatic polyamide resin.   Resin component 45 in which the resin cover contains 60 to 80% by mass of polyamide 66 resin, 15 to 25% by mass of amorphous aromatic polyamide resin, and 5 to 15% by mass of low water-absorbing aliphatic polyamide resin. The bearing device according to claim 1, wherein the bearing device is composed of ˜80 mass% and glass fiber 20-55 mass%.   The bearing device according to claim 4, wherein the low water-absorbing aliphatic polyamide resin is at least one selected from polyamide 12 resin, polyamide 11 resin, polyamide 612 resin, and polyamide 610 resin.   The bearing device according to claim 1, wherein the synthetic resin cover is integrally formed with a metal attachment member for fixing to the outer ring.   A wheel bearing comprising the bearing device according to any one of claims 1 to 6.

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