JP2008095912A - Alternator bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alternator bearing, which has a long life and high reliability. <P>SOLUTION: The alternator bearing 21 rotatably supports the rotary shaft of the alternator for an automobile with respect to a casing, the alternator comprising the casing, the rotary shaft, a stator, and a rotor. Concretely, the bearing 21 comprises: an inner race 22 serving as an internal member; an outer race 23 serving as an external member; a plurality of rolling elements 24 arranged between the inner race 22 and the outer race 23; and a cage 25 containing polyamide 9T resin having a degree of polymerization of 60 to 120 and a fiber loading material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling bearing, and more particularly to a bearing for an alternator for supporting a rotating shaft that is easily affected by heat inside an automotive alternator (alternator).

  A conventional automotive alternator rotates at a position facing a casing, a rotating shaft rotatably supported with respect to the casing by a bearing, a pulley fixed to the rotating shaft, a stator fixed to the casing, and the stator. And a rotor fixed to the shaft.

  A bearing that rotatably supports the rotating shaft is described in, for example, Japanese Patent Application Laid-Open No. 4-244624 (Patent Document 1). The bearing described in the publication includes an inner ring, an outer ring, a plurality of rolling elements disposed between the inner ring and the outer ring, a cage that holds a space between adjacent rolling elements, and a seal that seals the inside of the bearing. It is a rolling bearing provided with a seal.

  As a cage, a so-called engineering plastic simple substance such as polyamide (nylon 66), a resin cage formed of a composite material mixed with short fibers such as glass fiber and carbon fiber, or an iron plate punching (press) cage, etc. Is used.

  Polyamide is superior in physical properties required as a cage as compared to other engineering plastics. For example, it is superior in strength and heat resistance as compared with polyacetal. Further, compared with polybutylene terephthalate, the flexibility required for molding and bearing assembly is high.

In recent years, polyether sulphonic acid (PES), polyether imide (PEI), polyamide imide (PAI), polyether ether ketone are used as plastic cage materials for bearings used in high temperature environments exceeding 150 ° C. So-called super engineering plastic resins such as (PEEK) have been proposed. However, these materials are very expensive. On the other hand, polyamide is frequently used as a material for plastic cages because it has a good balance between material cost and performance.
JP-A-4-244624

  The alternator for automobiles is highly efficient and compact, and the electric load increases with the increase in power consumption. And it has the subject that bearing temperature becomes still higher by the heat_generation | fever accompanying these. As a result, the usage environment of the bearing that supports the rotating shaft of the alternator has become severe.

  In addition, the rolling elements of the rolling bearing that supports the rotating shaft generate heat as the automobile alternator rotates at a high speed and with a high load. Thereby, the temperature of the whole rolling bearing may become higher than the tempering temperature (about 170-200 degreeC) of the general steel which is the raw material of an inner-outer ring.

  In this case, the polyamide that is not suitable for use at high temperatures and the retainer of the iron plate (not subjected to heat treatment) cause dimensional deformation, strength deterioration, and the like, resulting in problems such as impairing the rotation function of the bearing. Also, polyamides may deteriorate over time under conditions where they are constantly or intermittently contacted with oils such as extreme pressure additives and additive oils, and may fail to meet the performance required in the market. .

  Furthermore, since polyamide has an amide bond in its molecular structure, it is easily affected by water, and has a large dimensional change and toughness change due to water absorption during high temperature and high humidity and dehydration during drying. This property is advantageous from the viewpoint of improving the toughness of the cage and preventing breakage of the cage in the bearing assembly process. However, since the dimensional change during high temperature and high humidity and during drying is large, there is a concern that smooth rotation of the rolling elements may be hindered.

  Therefore, the object of the present invention is to provide a long life and reliable by adopting a cage with improved dimensional stability, flexibility, heat resistance, chemical resistance, etc. as a bearing that supports the rotating shaft of an alternator for automobiles. It is providing the bearing for alternators with high property.

  An alternator bearing according to the present invention includes a casing, a rotating shaft housed in the casing, a stator fixed inside the casing, and a rotor that is disposed at a position facing the stator and rotates integrally with the rotating shaft. The rotating shaft of the alternator for automobiles is supported rotatably with respect to the casing. Specifically, it contains an inner member, an outer member, a plurality of rolling elements disposed between the inner member and the outer member, a polyamide 9T resin having a polymerization degree of 60 to 120, and a fibrous filler. And a cage that holds the interval between adjacent rolling elements.

  Polyamide 9T resin is excellent in heat resistance, oil resistance, chemical resistance, dimensional stability and toughness, and has high mechanical properties. Further, by adding a fibrous filler such as glass fiber, the rigidity of the cage is improved, and the dimensional accuracy during the production of the cage is stabilized. As a result, a long-life and highly reliable alternator bearing can be obtained even in a harsh environment such as a high temperature atmosphere, contact conditions with oil or chemicals, high-speed rotation conditions, high-load conditions, and humid environments.

  According to this invention, by forming a cage with a material containing polyamide 9T resin and a fibrous filler, the dimensional stability, flexibility, heat resistance, chemical resistance, etc. of the cage are improved. As a result, a long-life and highly reliable alternator bearing can be obtained.

  With reference to FIG. 1 and FIG. 2, the alternator 11 for motor vehicles based on one Embodiment of this invention and the deep groove ball bearing 21 as a bearing for alternators employ | adopted as the alternator for motor vehicles are demonstrated. 1 is a cross-sectional view of the alternator 11 for an automobile, and FIG. 2 is a cross-sectional view of the deep groove ball bearing 21.

  First, referring to FIG. 1, an automotive alternator 11 includes, as main components, a casing 12, a rotating shaft 13, a pulley 14, a stator 15, a rotor 16, and a deep groove ball bearing 21 as a rolling bearing. With.

  The casing 12 is configured by bolting a front bracket 12a and a rear bracket 12b. And the rotating shaft 13, the stator 15, the rotor 16, and the deep groove ball bearing 21 grade | etc., Are accommodated.

  The rotary shaft 13 is rotatably supported with respect to the casing 12 by two deep groove ball bearings 21. Further, it is inserted through the pulley 14 outside the casing 12 and through the rotor 16 and the slip ring 17 inside the casing 12. A brush 18 is pressed against the slip ring 17 by a spring 19.

  An endless belt (not shown) is attached to the pulley 14 and rotates the rotating shaft 13 as the engine (not shown) rotates. Moreover, in this embodiment, it functions also as a fan which cools the alternator 11 for motor vehicles.

  The stator 15 is a ring-shaped member and is fixed to the casing 12. On the other hand, the rotor 16 is fitted and fixed to the rotary shaft 13 and rotates integrally with the rotary shaft 13. The stator 15 and the rotor 16 are arranged so as to face each other, and a predetermined gap is provided between them. The stator 15 and the rotor 16 are each wound with a coil.

  Next, referring to FIG. 2, the deep groove ball bearing 21 includes an inner ring 22 as an inner member, an outer ring 23 as an outer member, and a plurality of rolling elements disposed between the inner ring 22 and the outer ring 23. 3, a retainer 25 that holds the interval between adjacent balls 24 as shown in FIG. 3, and a sealing seal 26 as a sealing member that seals both ends. Further, in order to maintain the smooth rotation of the ball 24, the bearing is filled with grease.

  The inner ring 22 is formed of general bearing steel such as SUJ-2. On the other hand, the outer ring 23 is formed by SAE5120, for example. In addition, the inner ring 22 and the outer ring 23 are subjected to heat treatment such as carburizing, sub-zero, and tempering in order to obtain predetermined mechanical properties. Further, the balls 24 are formed of ceramics mainly composed of silicon nitride, for example. The cage 25 is formed of a resin material described later.

  The “sub-zero treatment” refers to a treatment for maintaining the retained austenite at a temperature of 0 ° C. or lower in order to transform the retained austenite into martensite. In this embodiment, the sub-zero treatment is maintained at a temperature of −75 ° C. for a predetermined time. The “tempering process” refers to a process for reducing residual stress and internal strain caused by quenching and improving the toughness of steel and the like. In this embodiment, the tempering temperature of the inner ring 22 is 185 ° C. The tempering temperature of the outer ring 23 is set to about 270 ° C.

  The automotive alternator 11 having the above configuration converts part of the engine power into electricity. Specifically, the rotating shaft 13 and the rotor 16 rotate integrally with the rotation of the engine. At this time, electricity is generated between the stator 15 and the rotor 16 by the principle of electromagnetic induction. The electricity generated by the automobile alternator 11 is charged in a battery (not shown) and used for the operation of each electrical component.

  Here, the alternator 11 for automobiles generates heat simultaneously with power generation. In particular, the calorific value of the stator coil is large, and the temperature may rise to about 180 ° C. This heat is also transmitted to the deep groove ball bearing 21 through the casing 12. Furthermore, the deep groove ball bearing 21 itself generates heat as the balls 24 slide along the raceways of the inner ring 22 and the outer ring 23.

  When the temperature of the inner ring 22 and the outer ring 23 exceeds the tempering temperature, the composition is changed and the hardness is remarkably reduced, and the bearing clearance is increased with the enlargement of the dimensions due to the martensitic transformation in which the retained austenite of the steel becomes martensite. Bring. In particular, since the alternator 11 for an automobile is directly subjected to the vibration and impact of the engine to which it is attached, the indentation tends to occur on the raceway surface as the hardness of the inner ring 22 and the outer ring 23 decreases.

  Further, since the load region is constant in the outer ring 23 on the fixed side, the influence of vibration and impact is large and the raceway surface becomes rough. The above-mentioned phenomenon is promoted by a rough raceway surface which causes further heat generation under high speed and high load. As a result, there is a possibility that the bearing life may be reached early, such as peeling in a very short time.

  Therefore, by setting the tempering temperatures of the inner ring 22 and the outer ring 23 to be higher than the maximum temperature during use, it is possible to prevent changes in the structure due to temperature rise. Further, by employing the ceramic ball 24 and the synthetic resin cage 25, it is possible to prevent heat generation of the grease in the bearing and extend the bearing life.

  Next, the resin material forming the cage 25 will be described in detail. The cage 25 contains a polyamide 9T resin having a polymerization degree of 60 to 120 and glass fibers as a fibrous filler. The polyamide 9T resin is a polymer of terephthalic acid and nonanediamine represented by the formula (1), and is a semi-aromatic polyamide composed of an aromatic ring and a higher aliphatic chain. Specific examples of such materials include “Genstar (trade name)” manufactured by Kuraray Co., Ltd.

  Glass fiber is added in the range of 0 wt% to 50 wt% with respect to the total amount of the composition depending on the shape of the cage 25, the purpose of use, and the like. If the glass fiber content exceeds 50 wt%, not only the melt flowability of the resin composition is significantly lowered and the moldability is deteriorated, but also the deformability of the material becomes extremely small, and the excessive deformation at the time of molding of the cage can be avoided. It becomes difficult and the cage 25 may be damaged when the bearing is assembled. On the other hand, if the glass fiber content is less than 10 wt%, the effect of reinforcing the mechanical properties is small and the heat resistance is insufficient.

  Here, paying attention to the shape of the cage 25, in the case of a crown type cage for ball bearings, the content of the fibrous filler is preferably 0 wt% to 30 wt%, particularly preferably 10 wt% to 25 wt%.

  Next, in order to improve the assemblability of the cage 25, that is, forcibly removing at the time of mold release in the manufacturing process and relatively easily deforming at the time of ball incorporation, 0 wt% to 30 wt% of glass fiber is contained. It is preferable to contain 10 wt% to 30 wt%, and it is particularly preferable to contain 10 wt% to 25 wt%.

  Next, from the viewpoint of ensuring heat resistance and rigidity of the cage 25, that is, in order to appropriately support a relatively large force from the ball 24 generated during operation, the fibrous filler is contained in an amount of 20 wt% to 40 wt%. It is preferred that

  Furthermore, from the viewpoint of achieving both higher and higher deformability and higher rigidity, 0 wt% to 30 wt% is preferable, 10 wt% to 30 wt% is more preferable, and 10 wt% to 25 wt% is particularly preferable.

  In addition, as a form of glass fiber, an aspect ratio of 5 to 200 is preferable. If the aspect ratio is less than 5, the reinforcing effect of the cage 25 is not sufficiently exhibited and the cage becomes brittle. On the other hand, when the aspect ratio exceeds 200, uniform dispersion during mixing becomes extremely difficult. The fiber diameter is not particularly limited, but the average diameter is preferably 0.5 μm to 20 μm, more preferably 3 μm to 15 μm.

  The cage 25 configured as described above has heat resistance and chemical resistance and high mechanical characteristics. Further, this material has moderate flexibility and has a snap hit property necessary for the cage 25. Furthermore, this material has excellent dimensional stability due to its low water absorption. The cage 25 has high-temperature rigidity and can withstand long-term use under severe use conditions such as high temperature, high-speed rotation, and high load conditions.

  Further, since the degree of polymerization of the polyamide 9T resin is in the range of 60 to 120, it has mechanical characteristics as a cage, toughness necessary for incorporation, heat resistance, dimensional stability, etc. It can be used as the cage 25 of the deep groove ball bearing 21 employed in the above.

  Furthermore, when long-term heat resistance is required in an environment where the bearing temperature exceeds 150 ° C., the degree of polymerization of the polyamide 9T resin is more preferably 80 or more, and when the degree of polymerization exceeds 120, the moldability deteriorates. Therefore, the degree of polymerization is more preferably 80 to 120.

  The polyamide 9T resin exhibits excellent heat resistance, oil resistance, chemical resistance, dimensional stability, toughness and high mechanical properties. Further, by forming the cage 25 with this material, it is possible to greatly improve the water absorption, dimensional stability and assemblability, and to provide an inexpensive cage for applications requiring accuracy. . As a result, it is possible to obtain the cage 25 that can withstand long-time use even in a harsh environment such as a high-temperature atmosphere, contact conditions with oil or chemicals, high-speed rotation conditions, high-load conditions, and a humid environment.

  Next, an effect confirmation test conducted for confirming the effect of the present invention will be described. In the test, the melting point (° C.) of the material forming the cage, the temperature (° C.) at which bending occurs when a constant load (1.82 MPa) was applied, and the tensile strength (MPa) were measured. In addition, as materials for the cage, a synthetic resin (hereinafter referred to as “the product of the present invention”) in which 30 wt% glass fiber is mixed with polyamide 9T resin, and a synthetic resin (hereinafter referred to as “the present invention product”) in which 25 wt% glass fiber is mixed with polyamide 66 resin. Comparative test was conducted using “conventional product”). The results are shown in Table 1.

  Referring to Table 1, it was confirmed that the product of the present invention was superior in high temperature characteristics and high in strength as compared with the conventional product. Thereby, it was confirmed that the cage formed of the product of the present invention is suitable for use under a high temperature atmosphere or a high load condition.

  In addition, the resin composition used as the material for the cage 25 can be mixed by any method. For example, each component may be separately supplied to the melt mixer, or each component may be mixed in advance with a mixer such as a Henschel mixer or a ribbon blender and then supplied to the melt mixer. As the melt mixer, any apparatus such as a short or twin screw extruder, a mixing roll, a pressure kneader, and a Brabender blast graph can be used.

  Moreover, in said embodiment, although the example of glass fiber was shown as a fibrous filler, arbitrary fibers can be employ | adopted according to the objective, without restricting to this. For example, carbon fiber, metal fiber, aramid fiber, potassium titanate whisker, or the like can be used.

  Further, in the above embodiment, for the purpose of improving the adhesion between the resin and the glass fiber by giving the affinity between the polyamide 9T resin and the glass fiber, and improving the dispersibility of the glass fiber, The fiber may be subjected to a surface treatment according to a coupling agent such as a silane coupling agent or a titanate coupling agent, or other purposes.

  Further, as a material of the cage 25, a heat stabilizer, a solid lubricant, a lubricating oil, a colorant, an antistatic agent, a release agent, a fluidity improver, and a crystallization accelerator, as long as the object of the present invention is not impaired. Etc. may be added as appropriate.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The present invention is advantageously used for alternator bearings.

It is sectional drawing of the alternator for motor vehicles based on one Embodiment of this invention. It is sectional drawing of the deep groove ball bearing used for the alternator for motor vehicles shown in FIG. It is a perspective view of the crown type cage for ball bearings.

Explanation of symbols

  11 Automotive Alternator, 12 Casing, 12a Front Bracket, 12b Rear Bracket, 13 Rotating Shaft, 14 Pulley, 15 Stator, 16 Rotor, 15a, 16a Coil, 17 Slip Ring, 18 Brush, 19 Spring, 21 Deep Groove Ball Bearing, 22 Inner ring, 23 Outer ring, 24 balls, 25 Cage, 26 Seal seal.

Claims (1)

A casing,
A rotating shaft housed in the casing;
A stator fixed inside the casing;
An alternator bearing for rotatably supporting the rotating shaft of the automobile alternator, which is disposed at a position facing the stator and includes a rotor that rotates integrally with the rotating shaft, with respect to the casing,
An inner member;
An outer member;
A plurality of rolling elements disposed between the inner member and the outer member;
An alternator bearing comprising: a polyamide 9T resin having a degree of polymerization of 60 to 120; and a fibrous filler, and having a cage that keeps an interval between the adjacent rolling elements.

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