JP5090829B2 - Bearing device for steering of motorcycles - Google Patents

Description

  The present invention relates to a steering bearing device for a motorcycle.

  In a large vehicle, a tapered roller bearing or a cylindrical roller bearing is used as a rolling bearing of a steering bearing device for a two-wheeled vehicle that rotatably supports a steering stem of the two-wheeled vehicle on a steering support portion (for example, see Patent Document 1). In small and medium-sized vehicles, a ball bearing of a total ball type in which balls as rolling elements are closely arranged between raceway surfaces of inner and outer rings without using a cage is used (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 2004-217056 Japanese Patent Laid-Open No. 8-74861

  As described in Patent Document 2, a two-wheeled vehicle steering bearing device using a ball bearing of a total ball type is easy to drop off as a rolling element arranged between raceway surfaces of inner and outer rings during assembly. There is a bad problem. In particular, in an angular contact ball bearing in which a counter portion is provided on one side of at least one raceway surface of the inner and outer rings, the rolling elements easily fall off from the counter portion.

  In order to prevent such rolling elements from falling off, it is only necessary to hold the rolling elements arranged between the raceway surfaces of the inner and outer rings using a cage. Since the number of rolling elements arranged is reduced by the distance separating the two, the contact surface pressure between the rolling elements and the raceway surface increases, and surface damage such as fretting and seizure is likely to occur. In particular, since the raceway surface of the inner ring has a convex cross section in the direction perpendicular to the axis and a small radius of curvature, the rolling element in the cross section in the direction perpendicular to the axis is greater than the raceway surface of the outer ring having a concave shape in the direction perpendicular to the axis and a large curvature radius. The contact length becomes shorter and the contact surface pressure with the rolling element becomes higher. In order to reduce the contact surface pressure between the raceway surface and the rolling element, the radius of curvature in the axial cross section of the raceway surface is reduced so as to approach the radius of the rolling element, and the raceway surface and the rolling element in the axial cross section It is conceivable to increase the contact area by increasing the contact length.

  In addition, in a steering bearing device for a motorcycle, fine foreign matters such as gravel adhering to the road surface and the vehicle body enter the inside of the bearing mixed with muddy water and washing water when traveling in an area where road conditions are bad or washing. The bearing device for steering of a two-wheeled vehicle that supports a vertically oriented steering stem has the bearing end face directed up and down, so that compared to a bearing that supports a transverse shaft and the end face is directed left and right, Although it is easy to fall out and be discharged, the wedge angle of the wedge space formed between the raceway surface in the axial section and the rolling element when the radius of curvature in the axial section of the raceway surface is brought close to the radius of the rolling element Becomes smaller. When the wedge angle of the wedge space is reduced in this way, foreign objects are easily caught in the wedge space, and the reaction force for rejecting the foreign objects from the wedge space is reduced, so that the foreign objects are easily caught between the raceway surface and the rolling element. Become.

  When hard foreign matter such as gravel is caught between the raceway surface and the rolling element in this way, an indentation is formed on the raceway surface or the surface of the rolling element. There is a problem that surface peeling occurs at an early stage and bearing life is shortened.

  Therefore, an object of the present invention is to reduce the contact surface pressure between the rolling element and the raceway surface while ensuring the assemblability of the steering bearing device using the ball bearing, and to further remove the surface due to the biting of foreign matter. To prevent and extend the life of the bearing.

  In order to solve the above problems, the present invention enables a steering stem inserted in a steering support portion of a two-wheeled vehicle to be freely rotated by a ball bearing in which a plurality of rolling elements are arranged in a bearing space between raceway surfaces of an inner ring and an outer ring. In a supported steering bearing device for a two-wheeled vehicle, a rolling element arranged between the raceway surfaces of the inner ring and the outer ring is held by a cage, and an axial cross section of the raceway surface of at least the inner ring of the raceway of the inner ring and the outer ring The radius of curvature of the rolling element is 53% or less of the diameter of the rolling element, and the small radius of curvature race ring whose curvature radius of the raceway surface is 53% or less of the diameter of the rolling element is C: 0.95 to 1 as an alloy element. 10% by mass, Si: 0.15 to 0.70% by mass, Mn: 1.15% by mass or less, Cr: 0.90 to 1.60% by mass, with the balance being Fe and inevitable impurities Using steel as a material, Put, subjected to tempering treatment, the amount of residual austenite in the surface layer of the raceway surface 20 vol% or more, employing the configuration of the Vickers hardness Hv is 680 or more.

  That is, the rolling elements arranged between the raceways of the inner ring and the outer ring are held by the cage, and the radius of curvature in the axial section of at least the raceway surface of the inner ring and the outer ring is 53% or less of the diameter of the rolling element. In addition, it is preferable that the contact area between the rolling elements and at least the raceway surface of the inner ring in the axial section is increased and the contact area thereof is increased while ensuring assemblability of the steering bearing device by ensuring that it is 52% or less. The contact surface pressure is reduced, and a small radius of curvature raceway with a raceway radius of curvature of 53% or less, preferably 52% or less of the diameter of the rolling element is used as an alloy element. 10% by mass, Si: 0.15 to 0.70% by mass, Mn: 1.15% by mass or less, Cr: 0.90 to 1.60% by mass, with the balance being Fe and inevitable impurities Hardened with steel By performing tempering treatment, the amount of retained austenite in the surface layer portion of the raceway surface is set to 20% by volume or more, and the Vickers hardness Hv is set to 680 or more, thereby preventing surface peeling due to foreign matter biting and extending the bearing life. I made it.

  The steel used as the material of the small radius of curvature race ring is a steel corresponding to the high carbon chromium bearing steel SUJ2 or SUJ3, and the amount of retained austenite in the surface layer portion of the raceway surface is obtained by quenching and tempering the steel material. 20% by volume or more and Vickers hardness Hv of 680 or more can alleviate stress concentration at the edge portion of the indentation caused by the biting of foreign matter, and suppress the propagation of cracks starting from the indentation, Surface peeling can be prevented.

  By setting the prior austenite grain size of the surface layer portion of the raceway surface to 10 or more as defined in JIS G0551, the toughness of the surface layer portion of the raceway surface can be enhanced. In order to set the prior austenite grain size to 10 or more, the heating temperature during the quenching process may be lowered at the Acm point or higher. The prior austenite crystal grains are austenite crystal grains that have undergone phase transformation at the start of quenching, and remain as a past history even after transformation to martensite by cooling.

  By nitriding the steel material forming the small radius of curvature race ring, the surface layer portion of the raceway surface can be strengthened, the generation of indentation can be reduced, and the stress concentration in the indentation portion can be further reduced. . Further, occurrence of surface damage such as fretting and seizure can be prevented.

  It is preferable that the nitrogen concentration at a depth of 100 μm from the surface of the surface portion of the raceway surface of the small curvature radius raceway subjected to the nitriding treatment is 0.1% by mass or more. This is because many foreign materials such as gravel have a diameter of about 100 μm.

  By sealing the bearing space with a contact-type seal member, it is possible to suppress entry of foreign matter into the bearing.

  The intrusion of foreign matter into the bearing can also be suppressed by sealing the bearing space with a non-contact type shield member.

  By using a urea grease containing a urea compound as a thickener for the grease sealed in the bearing space, a stable oil film is formed between the rolling elements and the raceway surface, resulting in surface damage such as fretting and seizure. Can be more reliably prevented. In addition, since urea-based grease is excellent in oxidation resistance, water resistance, and heat resistance, the inside of the bearing can be stably lubricated for a long period of time.

  The above-described steering bearing device for each two-wheeled vehicle is suitable for the ball bearing that is an angular ball bearing in which a counter portion is provided on one side of the raceway surface of at least one of the inner ring and the outer ring.

  The two-wheeled vehicle steering bearing device of the present invention holds the rolling elements arranged between the raceway surfaces of the inner ring and the outer ring in a cage, and in the axial cross section of the raceway surface of at least the inner ring of the raceways of the inner ring and the outer ring. A small radius of curvature raceway ring in which the radius of curvature is 53% or less, preferably 52% or less of the diameter of the rolling element, and the radius of curvature of this raceway surface is 53% or less, preferably 52% or less of the diameter of the rolling element, As alloying elements, C: 0.95 to 1.10% by mass, Si: 0.15 to 0.70% by mass, Mn: 1.15% by mass or less, Cr: 0.90 to 1.60% by mass Since the balance is made of steel consisting of Fe and inevitable impurities, quenching and tempering are performed, the amount of retained austenite in the surface layer portion of the raceway surface is 20% by volume or more, and the Vickers hardness Hv is 680 or more. Using While ensuring the assembly of the bearings for the bearing device, it is possible to reduce the contact surface pressure between the rolling elements and the raceway surfaces, further, to prevent surface peeling due to biting of foreign matters, it is possible to extend the bearing life.

  By setting the prior austenite grain size of the surface layer portion of the raceway surface to 10 or more as defined in JIS G0551, the toughness of the surface layer portion of the raceway surface can be enhanced.

  By nitriding the steel material forming the small radius of curvature race ring, the surface layer portion of the raceway surface can be strengthened, the generation of indentation can be reduced, and the stress concentration in the indentation portion can be further reduced. . Further, occurrence of surface damage such as fretting and seizure can be prevented.

  By sealing the bearing space with a contact-type seal member, it is possible to suppress entry of foreign matter into the bearing.

  The intrusion of foreign matter into the bearing can also be suppressed by sealing the bearing space with a non-contact type shield member.

  By using a urea grease containing a urea compound as a thickener for the grease sealed in the bearing space, a stable oil film is formed between the rolling elements and the raceway surface, resulting in surface damage such as fretting and seizure. Can be more reliably prevented. In addition, since urea-based grease is excellent in oxidation resistance, water resistance, and heat resistance, the inside of the bearing can be stably lubricated for a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this two-wheeled steering bearing device is configured such that a steering stem 12 inserted in a steering pipe 11 as a steering support portion is rotatably supported by a pair of upper and lower angular ball bearings 1. A steering wheel 15 is attached to the steering stem 12 via an upper bracket 14 that connects the left and right front forks 13.

  As shown in FIG. 2, the angular ball bearing 1 includes a plurality of balls 4 as rolling elements that are arranged between the raceway surfaces 2 a and 3 a of the inner ring 2 and the outer ring 3 by a cage 5. Counter portions 2b and 3b are provided on one side of the raceway surfaces 2a and 3a opposite to each other. Urea grease (not shown) is sealed in the bearing space in which the balls 4 are arranged. Sealed with a contact-type seal member 6a.

  The curvature radius ρ2 in the axial section of the raceway surface 2a of the inner ring 2 is 51% of the diameter D of the ball 4, and the curvature radius ρ3 in the axial section of the raceway surface 3a of the outer ring 3 is 53% of the diameter D of the ball 4. The contact length between the ball 4 and each of the track surfaces 2a and 3a in the axial cross section is long. Therefore, even if the number of balls 4 arranged is reduced by the amount using the cage 5, the contact area between each ball 4 and each track surface 2a, 3a can be expanded to reduce the contact pressure between them. it can.

  Both the inner ring 2 and the outer ring 3 are subjected to quenching and tempering treatment using the high carbon chrome bearing steel SUJ2 or SUJ3 shown in Table 1 as a raw material. The amount of retained austenite in the surface layer portions of the raceway surfaces 2a and 3a of the outer ring 3 is 20% by volume or more, and the Vickers hardness Hv is 680 or more. Further, the prior austenite grain size defined in JIS G0551 is made finer than 10th. In both SUJ2 and SUJ3, P and S as inevitable impurities are both 0.025% by mass or less. This is because almost all of P precipitates at the prior austenite grain boundaries to reduce toughness, and S combines with Mn to become MnS, and when MnS increases, the toughness decreases.

  FIG. 3 shows a modification of the angular ball bearing 1. This modification is different in that both sides of the bearing space are sealed with a non-contact type shield member 6b. The other portions are the same as those in the embodiment. The radius of curvature ρ2 of the raceway surface 2a of the inner ring 2 is 51% of the diameter D of the ball 4, and the radius of curvature ρ3 of the raceway surface 3a of the outer ring 3 is the diameter D of the ball 4. Of 53%.

  In the embodiment described above, the retained austenite amount in the surface layer portion of the raceway surface of the inner and outer rings is set to 20% by volume or more, and the Vickers hardness Hv is set to 680 or more. It may be the amount and Vickers hardness.

  Further, in the above-described embodiment, the ball bearing that supports the steering stem is an angular ball bearing, and the counter portion is provided on one side of the raceway surfaces of both the inner ring and the outer ring. However, the angular ball bearing includes either the inner ring or the outer ring. A counter portion may be provided on one side of one of the raceway surfaces, and the ball bearing may be a deep groove ball bearing.

  As an example, the radius of curvature in the axial cross section of the raceway surface of the inner ring is 51% of the diameter of the ball, and the radius of curvature in the axial cross section of the raceway surface of the outer ring is 53% of the diameter of the ball. Deep groove ball bearings with inner and outer rings made of SUJ2 or SUJ3 and tempered, with a retained austenite amount of 20 vol% or more in the surface layer portion of each raceway surface and a Vickers hardness Hv of 680 or more (Examples 1 to 4) ) Was prepared. Examples 1, 2 and 4 were also subjected to nitriding treatment, and the nitrogen concentration at a depth of 100 μm from the surface was 0.1% by mass or more. Further, as a comparative example, the inner and outer rings having the same radius of curvature of the raceway surface are quenched and tempered using SUJ2 or SUJ3 as a raw material, and the amount of retained austenite and Vickers hardness Hv in the surface layer portion of each raceway surface. A deep groove ball bearing (Comparative Examples 1 to 4) in which at least one of these was out of the range defined in the present invention was also prepared. The comparative examples 2 and 4 were also subjected to nitriding treatment. The dimensions of the deep groove ball bearings of the examples and comparative examples were an outer diameter of 62 mm, an inner diameter of 30 mm, and a width of 16 mm.

The deep groove ball bearings of the above examples and comparative examples were attached to a rotating shaft disposed in a lubricating oil bath mixed with foreign matter, and a foreign matter mixed life test was performed in which a radial load was applied. The test conditions are as follows.
・ Radial load: 6.86kN
・ Maximum contact surface pressure: 3.2 GPa
・ Rotation speed: 3000rpm
・ Lubricant: Turbine oil VG56
Foreign matter: gas atomized powder (particle size 100 to 180 μm, hardness Hv 700 to 800, mixing amount 0.4 g / liter)

  The results of the foreign matter mixing life test are also shown in Table 2. The life ratio in the table is based on the bearing life of Comparative Example 1 with SUJ2 as the raw material, the amount of retained austenite in the surface layer portion is 12% by volume, and the Vickers hardness Hv is 750. Evaluation was based on the L10 life (the time in which 90% of the samples fitted to the Weibull distribution can be used without damage).

  Each of the examples has a long bearing life with a life ratio of 2 or more. In particular, Examples 1, 2, and 4 subjected to nitriding treatment have a long bearing life with a life ratio of 3 or more. ing. On the other hand, the comparative examples 2 and 4 subjected to nitriding treatment have a life ratio exceeding 1 but the life ratio far exceeds 2 in the comparative examples 2 and 4 as compared with those in the respective examples. The bearing life is extremely short. Most of the factors determining the L10 life of each of the examples and the comparative examples were surface peeling of the raceway surface of the inner ring. From the above test results, when the amount of retained austenite in the surface layer portion of the raceway surface of the inner ring is 20% by volume or more and the Vickers hardness Hv is 680 or more, the radius of curvature of the raceway surface of the inner ring is 52% of the ball diameter. Even in the following cases, it has been confirmed that surface peeling caused by foreign object biting can be prevented and the bearing life can be greatly extended.

  Next, similarly to the inner and outer rings of Example 1, nitriding treatment, quenching, and tempering treatment were performed using SUJ2 as a raw material, the amount of retained austenite in the surface layer portion was 20% by volume or more, and the Vickers hardness Hv was 680 or more. As shown in Table 3, cylindrical test pieces (Examples 11 to 14) in which the heating temperature during the quenching treatment was changed to change the prior austenite grain size of the surface layer portion were prepared. The cylindrical test pieces were tempered at 180 ° C. for 2 hours, and the cylindrical surfaces were superfinished to the same extent as the raceway surfaces of the inner and outer rings.

About each said cylindrical test piece, the rolling fatigue test which makes a cylindrical surface roll-contact with two opposing steel balls was done. In this rolling fatigue test with a steel ball as a counterpart, the maximum contact surface pressure is made higher than that in a rolling fatigue test with a steel roller as a counterpart, and the toughness of the surface portion of the cylindrical specimen is strictly evaluated. The test conditions are as follows.
・ Cylinder test piece dimensions: 12mm outer diameter, 22mm length
-Counter steel ball dimensions: Diameter 19.05mm
・ Maximum contact surface pressure: 5.88 GPa
・ Loading speed: 46240 cycles / minute ・ Lubricating oil: Turbine oil VG68 (oil bath spray lubrication)

  The results of the rolling fatigue test are also shown in Table 3. The table also shows the life ratio of the L50 life (the time in which 50% of the samples applied to the Weibull distribution can be used without being damaged) together with the life ratio of the L10 life. Each life ratio is obtained by setting the L10 life and the L50 life of Example 11 as the reference value 1, respectively. From these test results, Examples 13 and 14 in which the prior austenite grain size was made finer than No. 10 of JIS G0551 were compared with Examples 11 and 12 in which the former austenite grain size was smaller than No. 10, and the L50 life ratio was Although no significant difference is observed, the L10 life ratio is extended to about twice. From this, it can be seen that by setting the prior austenite grain size to 10 or more, the toughness of the surface layer portion can be improved, the rolling fatigue life can be stably extended, and the probability of short life can be reduced.

Notched longitudinal sectional view showing an embodiment of a steering bearing device for a motorcycle 1 is a longitudinal sectional view showing the angular ball bearing of FIG. FIG. 2 is a longitudinal sectional view showing a modification of the angular ball bearing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Angular contact ball bearing 2 Inner ring 3 Outer ring 2a, 3a Raceway surface 2b, 3b Counter part 4 Ball 5 Cage 6a Seal member 6b Shield member 11 Steering pipe 12 Steering stem 13 Front fork 14 Upper bracket 15 Handle

Claims (8)

  In a steering bearing device for a two-wheeled vehicle, wherein a steering stem inserted into a steering support portion of the two-wheeled vehicle is rotatably supported by a ball bearing in which a plurality of rolling elements are arranged in a bearing space between the raceway surfaces of the inner ring and the outer ring. The rolling elements arranged between the raceways of the outer ring are held in a cage, and the radius of curvature in the axial section of at least the raceway surface of the inner ring of the inner ring and the outer raceway is 53% of the diameter of the rolling element. In the following, a small curvature radius race ring in which the radius of curvature of the raceway surface is 53% or less of the diameter of the rolling element, C: 0.95 to 1.10 mass%, Si: 0.15 to. 70% by mass, Mn: 1.15% by mass or less, Cr: 0.90 to 1.60% by mass, with the balance being steel composed of Fe and unavoidable impurities, quenching and tempering, Of the raceway The amount of retained austenite in layer portion 20 vol% or more, steering bearing device for two-wheeled vehicle, characterized in that the Vickers hardness Hv was 680 or more.   2. The steering bearing device for a motorcycle according to claim 1, wherein the prior austenite grain size of a surface layer portion of the raceway surface is set to No. 10 or more as defined in JIS G0551.   The bearing device for steering of a two-wheeled vehicle according to claim 1 or 2, wherein a nitriding treatment is applied to a steel material forming the small radius of curvature raceway.   The bearing device for steering a motorcycle according to claim 3, wherein a nitrogen concentration at a depth of 100 µm from a surface of a surface layer portion of the raceway surface of the small curvature radius raceway subjected to the nitriding treatment is 0.1 mass% or more. .   The two-wheeled vehicle steering bearing device according to any one of claims 1 to 4, wherein the bearing space is sealed with a contact-type seal member.   The bearing device for steering a motorcycle according to any one of claims 1 to 4, wherein the bearing space is sealed with a non-contact type shield member.   The bearing device for steering a motorcycle according to claim 5 or 6, wherein urea grease containing a urea compound as a thickener is sealed in the bearing space sealed with the seal member or the shield member.   The bearing device for steering a motorcycle according to any one of claims 1 to 7, wherein the ball bearing is an angular ball bearing in which a counter portion is provided on one side of at least one of the raceways of the inner ring and the outer ring.

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