JP2018132110A - Rolling bearing - Google Patents

Abstract

[PROBLEMS] To provide a rolling bearing that can improve lubrication performance while preventing or suppressing the occurrence of electrolytic corrosion in a rolling bearing provided in a railway vehicle. A bearing 32 is a rolling bearing provided in a main motor of a railway vehicle. The bearing 32 includes an inner ring 32b, an outer ring 32a surrounding the inner ring 32b, a plurality of rolling elements 32c disposed between the inner ring 32b and the outer ring 32a, and a lubricant sealed between the inner ring 32b and the outer ring 32a. Have. The lubricant is composed of a base oil and carbon black, the first conductivity imparting agent that imparts conductivity to the lubricant, and the second conductivity that is composed of carbon nanotubes and imparts conductivity to the lubricant. And an imparting agent. [Selection] Figure 2

Description

  The present invention relates to a rolling bearing.

  A main motor provided in a railway vehicle includes a bearing device, and the bearing device includes a rolling bearing. A rolling bearing provided in such a railway vehicle includes an inner ring, an outer ring that surrounds the inner ring, a plurality of rolling elements disposed between the inner ring and the outer ring, and a cage that holds the plurality of rolling elements. . Further, grease as a lubricant is sealed between the inner ring and the outer ring.

  Japanese Patent Application Laid-Open No. 2008-164173 (Patent Document 1) discloses a rolling bearing in which a plurality of rolling elements are rotatably held at substantially equal intervals via a cage between an inner ring and an outer ring, and A technique is disclosed in which a grease composition containing carbon black or carbon nanotubes in a proportion of 0.5 to 5% by weight is encapsulated.

  Japanese Patent Laid-Open No. 2002-195277 (Patent Document 2) discloses a rolling bearing in which a plurality of rolling elements are rotatably held at substantially equal intervals via a cage between an inner ring and an outer ring, and A technique of enclosing a grease composition containing carbon black in a proportion of 0.1 to 10% by weight is disclosed.

JP 2008-164173 A JP 2002-195277 A

  Consider a case where grease as a lubricant sealed in a rolling bearing provided in a railway vehicle has an insulating property. Moreover, in a railway vehicle, a high electric field is applied, for example, between an outer ring and a rolling element, or between an inner ring and a rolling element, for example, by generating a potential difference between the frame of the main motor and the main shaft. There is a case. In such a case, the insulation by the oil film of the lubricant is destroyed, and a discharge current flows through the rolling bearing. However, the discharge current flows to the outer ring surface, the inner ring surface, or the rolling element surface. Therefore, there is a possibility that electric corrosion occurs in the rolling bearing.

  On the other hand, when conductivity is imparted to the grease as the lubricant, since no discharge current flows through the rolling bearing provided in the railway vehicle, it is possible to prevent or suppress the occurrence of electrolytic corrosion on the rolling bearing. can do.

  However, when the shear stability of the thickener contained in the grease as the lubricant is small, when a shear stress is applied to the grease, the performance of the thickener contained in the grease decreases, The separation of the base oil proceeds, the grease hardens, and the performance of the grease as a lubricant decreases. That is, it is difficult to improve the lubrication performance of the rolling bearing while preventing or suppressing the occurrence of electrolytic corrosion in the rolling bearing provided in the railway vehicle.

  The present invention has been made to solve the above-described problems of the prior art, and in a rolling bearing provided in a railway vehicle, lubrication of the rolling bearing while preventing or suppressing the occurrence of electrolytic corrosion. An object of the present invention is to provide a rolling bearing capable of improving performance.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The rolling bearing as one aspect of the present invention is a rolling bearing provided in a main motor of a railway vehicle. The rolling bearing has an inner ring, an outer ring surrounding the inner ring, a plurality of rolling elements disposed between the inner ring and the outer ring, and a lubricant sealed between the inner ring and the outer ring. The lubricant is composed of a base oil and carbon black, the first conductivity imparting agent that imparts conductivity to the lubricant, and the second conductivity that is composed of carbon nanotubes and imparts conductivity to the lubricant. And an imparting agent.

  As another aspect, the lubricant may contain 0.5 to 5.0% by mass of the second conductivity imparting agent. At this time, the immiscible penetration of the lubricant may be 195 to 215.

  Moreover, as another aspect, the lubricant may contain 1.0 to 1.5% by mass of a second conductivity imparting agent. At this time, the immiscibility of the lubricant may be 200 to 210.

  As another aspect, the dmN value of the rolling bearing may be 300,000 to 800,000.

  By applying one embodiment of the present invention, in a rolling bearing provided in a railway vehicle, the lubrication performance of the rolling bearing can be improved while preventing or suppressing the occurrence of electrolytic corrosion.

It is a figure which shows typically the structure of the main motor periphery of the railway vehicle provided with the rolling bearing of embodiment. It is a partially cutaway perspective view of a ball bearing as an example of a rolling bearing of an embodiment. It is a partially cutaway perspective view of a roller bearing as another example of the rolling bearing of the embodiment. It is a figure which shows the structure of carbon black typically. It is a figure which shows the structure of a carbon nanotube typically. It is a figure which shows typically the factor of the electric corrosion which generate | occur | produces in the rolling bearing with which a rail vehicle is equipped. It is a graph which shows the relationship between a fusion | melting load and content of a carbon nanotube. It is a figure which shows typically the fine structure of the grease of the comparative example 2 before and behind a lubrication life test. It is a figure which shows typically the fine structure of the grease of Example 1 before and after a lubrication life test. It is a figure which shows typically the electricity supply rotation test apparatus using a small bearing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, the drawings may be schematically represented with respect to the width, thickness, shape, and the like of each part as compared with the embodiments for the sake of clarity of explanation, but are merely examples, and the interpretation of the present invention is not limited thereto. It is not limited.

  In addition, in the present specification and each drawing, elements similar to those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description may be omitted as appropriate.

(Embodiment)
<Structure around the main motor of a railway vehicle>
First, a structure around a main motor of a railway vehicle provided with a rolling bearing according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing a structure around a main motor of a railway vehicle provided with the rolling bearing of the embodiment.

  The rolling bearing of the present embodiment is a rolling bearing provided in a main motor of a railway vehicle that travels on a rail.

  As shown in FIG. 1, the railway vehicle provided with the rolling bearing according to the present embodiment includes a main motor 10, a coupling 11, a drive device 12, an axle 13, and wheels 14. .

  The main motor 10 includes a main shaft 15, and the main shaft 15 of the main motor 10 is connected to the drive device 12 via a coupling 11. The drive device 12 has a small gear 16 fixed to the main shaft 15 and a large gear 17 fixed to the axle 13, and the small gear 16 and the large gear 17 are arranged to mesh with each other. A pair of wheels 14 is fixed to the axle 13.

  The main motor 10 is supported by a carriage (not shown) provided in the railway vehicle. Further, both ends of the axle 13 are rotatably supported by a carriage (not shown) provided in the railway vehicle.

  The main motor 10 includes a frame 20, a stator 21, and a rotor 22. The stator 21 has a coil 21a, and the rotor 22 is disposed so as to face the stator. The frame 20 is disposed so as to surround the stator 21 and the rotor 22. The main shaft 15 is fixed to the center portion of the rotor 22 so as to penetrate the rotor 22. That is, the main shaft 15 is a rotation shaft of the main motor 10. The main motor 10 has a bearing device 30 and a bearing device 31. The rotor 22 and the main shaft 15 are supported by the frame 20 via the bearing device 30 and the bearing device 31. That is, the rotor 22 is supported by the frame 20 so as to be rotatable about the main shaft 15 as a rotation axis.

  When the railway vehicle travels, first, a three-phase alternating current is supplied to the coil 21 a of the stator 21. At this time, a rotating magnetic field is formed around the rotor 22, and an induced current is generated in the rotor 22 by the rotating magnetic field. Thus, a rotating magnetic field is formed around the rotor 22 and an induced current is generated in the rotor 22, thereby generating an electromagnetic force that works to rotate the rotor 22 around the rotation axis. The rotor 22 rotates. Then, the main shaft 15 fixed to the rotor 22 also rotates.

  Thus, the main shaft 15 rotates with the operation of the main motor 10, and the rotation of the main shaft 15 is transmitted to the driving device 12 through the coupling 11, and the small gear 16 fixed to the main shaft 15 rotates. The large gear 17 that meshes with the small gear 16 is rotated by the rotation of the small gear 16. Then, when the axle 13 fixed to the large gear 17 rotates, the wheels 14 fixed to both ends of the axle 13 rotate, and the railway vehicle travels.

<Rolling bearing structure>
Next, the structure of the rolling bearing according to the present embodiment will be described with reference to FIGS. FIG. 2 is a partially cutaway perspective view of a ball bearing as an example of the rolling bearing of the embodiment. FIG. 3 is a partially cutaway perspective view of a roller bearing as another example of the rolling bearing of the embodiment.

  As shown in FIGS. 1 and 2, the bearing device 30 includes a bearing 32 as a rolling bearing, a lid portion 33 on the rotor 22 side, and a lid portion 34 on the opposite side to the rotor 22 side. . The bearing 32 includes an outer ring 32a, an inner ring 32b, a rolling element 32c, and a cage 32d. The outer ring 32a surrounds the inner ring 32b. The rolling element 32c is disposed between the inner ring 32b and the outer ring 32a. The bearing 32 is sandwiched between the lid portion 33 and the lid portion 34, the inner circumferential surface of the inner ring 32 b is in contact with the outer circumferential surface of the main shaft 15, and the outer ring 32 a is fixed to the main motor 10.

  In the example shown in FIG. 2, the bearing 32 is a ball bearing, and the rolling element 32c is a ball. In such a case, the inner ring 32b is arranged inside the outer ring 32a so that the outer peripheral surface (track surface) of the inner ring 32b faces the inner peripheral surface (track surface) of the outer ring 32a. A plurality of rolling elements 32c are arranged in an annular shape along the circumferential direction of the outer circumferential surface of the inner ring 32b and the circumferential direction of the inner circumferential surface of the outer ring 32a. The cage 32d holds the rolling elements 32c at a constant pitch in the circumferential direction.

  The rolling element 32c which is a ball is mainly subjected to rolling friction between the raceway surface of the inner ring 32b and the raceway surface of the outer ring 32a. In order to reduce this friction, grease as a lubricant is sealed between the inner ring 32b and the outer ring 32a.

  As shown in FIGS. 1 and 3, the bearing device 31 includes a bearing 35 as a rolling bearing, a lid portion 36 on the rotor 22 side, and a lid portion 37 on the opposite side to the rotor 22 side. . The bearing 35 includes an outer ring 35a, an inner ring 35b, a rolling element 35c, and a cage 35d. The outer ring 35a surrounds the inner ring 35b. The rolling element 35c is disposed between the inner ring 35b and the outer ring 35a. The bearing 35 is sandwiched between the lid portion 36 and the lid portion 37, the inner circumferential surface of the inner ring 35 b is in contact with the outer circumferential surface of the main shaft 15, and the outer ring 35 a is fixed to the main motor 10.

  In the example shown in FIG. 3, the bearing 35 is a roller bearing, and the rolling element 35c is, for example, a roller. In such a case, the inner ring 35b is disposed inside the outer ring 35a so that the outer peripheral surface (track surface) of the inner ring 35b faces the inner peripheral surface (track surface) of the outer ring 35a. A plurality of rolling elements 35c are arranged in an annular shape along the circumferential direction of the outer circumferential surface of the inner ring 35b and the circumferential direction of the inner circumferential surface of the outer ring 35a. The cage 35d holds the rolling elements 35c at a constant pitch in the circumferential direction.

  The rolling element 35c, which is a roller, mainly receives rolling friction between the raceway surface of the inner ring 35b and the raceway surface of the outer ring 35a. In order to reduce this friction, grease as a lubricant is sealed between the inner ring 35b and the outer ring 35a.

  As described above, the bearing 32 is provided in the bearing device 30, the bearing 35 is provided in the bearing device 31, and the bearing device 30 and the bearing device 31 are provided in the main motor 10 provided in the railway vehicle. The maximum operation speed of the railway vehicle is, for example, about 80 to 130 km / h, and the maximum rotation speed of the main shaft 15 of the main motor 10, that is, the maximum rotation speed of the bearing 32 and the bearing 35 is, for example, about 4000 to 6000 rpm. Therefore, the dmN value in each of the bearing 32 and the bearing 35 is 300,000 to 800,000, which is extremely larger than the dmN value of a bearing provided in a normal mechanical device. The dmN value means the product of dm and N, dm means the average value of the inner diameter and the outer diameter of the bearing, and N means the number of rotations per minute of the bearing.

<Grease composition>
Next, the composition of the grease enclosed in the rolling bearing of the present embodiment, that is, the composition of the grease as the lubricant of the present embodiment will be described.

The grease as the lubricant of the present embodiment contains a base oil, a first conductivity imparting material, and a second conductivity imparting material. The first conductivity imparting material and the second conductivity imparting material both impart conductivity to the lubricant. In the specification of the present application, imparting conductivity means imparting conductivity equal to or higher than that of a semiconductor, and conductivity (reciprocal of electrical resistivity) is 10 ⁻⁶ Scm ⁻¹ or more. That is, it means that the electrical resistivity is 10 ⁶ Ωcm or less.

  The base oil is not particularly limited, and can be used regardless of whether it is a mineral oil type or a synthetic type as long as it is normally used as a base oil for lubricating grease.

  Mineral oil base oils include, for example, lubricating oil fractions obtained by subjecting crude oil to atmospheric distillation and vacuum distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrogen Paraffinic or naphthenic oils that are refined by appropriately combining purification treatments such as chemical purification, sulfuric acid washing or clay treatment can be used.

  Synthetic lubricant base oils include, for example, poly α-olefin (polybutene, 1-octene oligomer or 1-decene oligomer), alkylbenzene, alkylnaphthalene, diester (ditridecylglutarate, di (2-ethylhexyl)). Adipate, diisodecyl adipate, ditridecyl adipate or di (2-ethylhexyl) separate), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate or pentaerythritol pelargonate), Polyoxyalkylene glycol, polyphenyl ether, silicone oil, perfluoroalkyl ether, or the like can be used. These base oils may be used alone or in combination of two or more.

  The first conductivity imparting agent is made of carbon black. FIG. 4 is a diagram schematically showing the structure of carbon black.

  As shown in FIG. 4, the carbon black 40 means spherical carbon fine particles that are artificially synthesized and have a diameter of several nanometers to several hundred nanometers. As shown in FIG. 4, the carbon black 40 has a network structure formed by agglomerating spherical carbon fine particles. Thereby, the carbon black contained in the grease has a function as a conductivity imparting agent for imparting conductivity to the grease and a function as a thickener for keeping the grease in a semi-solid state.

  The average particle diameter of the carbon black contained in the grease sealed in the rolling bearing of the present embodiment is preferably 30 to 70 nm. When the average particle size is 30 nm or more, the conductivity is improved as compared with the case where the average particle size is less than 30 nm, and when the average particle size is 70 nm or less, the carbon fine particles are aggregated as compared with the case where the average particle size exceeds 70 nm. Thus, it becomes easy to form a network structure.

  The content of carbon black contained in the grease enclosed in the rolling bearing of the present embodiment is preferably 5 to 15% by mass. When the carbon black content is 5% by mass or more, the conductivity of the grease is improved as compared with the case where the carbon black content is less than 5% by mass. On the other hand, when the carbon black content is 15% by mass or less, the lubricity of the grease is improved as compared with the case where the carbon black content exceeds 15% by mass.

  The second conductivity imparting agent is made of carbon nanotubes. FIG. 5 is a diagram schematically showing the structure of the carbon nanotube.

  As shown in FIG. 5, the carbon nanotube 41 has a hollow tubular structure in which a graphene sheet in which carbon atoms are two-dimensionally bonded in a hexagonal network by a covalent bond is rounded into a cylinder having a diameter of nanometer order. . Accordingly, the carbon nanotubes contained in the grease have a function as a conductivity imparting agent that imparts conductivity to the grease and a function as a thickener for keeping the grease in a semi-solid state.

  In addition, the strength of the carbon nanotube is higher than that of the carbon black network structure, and even when a shear stress is applied to the carbon nanotube, the hollow tubular structure of the carbon nanotube is not easily destroyed. Therefore, the carbon nanotube contained in the grease does not lose its function as a thickener even when a shear stress is applied to the grease, and can improve the lubricity of the grease.

  The content of the carbon nanotubes contained in the grease enclosed in the rolling bearing of the present embodiment, that is, the second conductivity imparting agent, is preferably 0.5 to 5.0% by mass. When the content of the carbon nanotube is 0.5% by mass or more, the performance of the grease as a lubricant is improved as compared with the case where the content of the carbon nanotube is less than 0.5% by mass. On the other hand, when the content of carbon nanotubes is 5.0% by mass or less, compared to the case where the content of carbon nanotubes exceeds 5.0% by mass, the immiscibility of grease can be 195 or more. Can be softened. Further, when the content of the carbon nanotube is 0.5% by mass or more, the grease immiscibility penetration is 215 or less. That is, when the content of the carbon nanotube, that is, the second conductivity imparting agent is 0.5 to 5.0% by mass, the grease immiscibility is 195 to 215.

  Moreover, it is more preferable that the content of the carbon nanotube contained in the grease enclosed in the rolling bearing of the present embodiment, that is, the second conductivity imparting agent is 1.0 to 1.5% by mass. When the content of the carbon nanotube is 1.0% by mass or more, the performance of the grease as a lubricant is further improved as compared with the case where the content of the carbon nanotube is less than 1.0% by mass. On the other hand, when the content of carbon nanotubes is 1.5% by mass or less, compared to the case where the content of carbon nanotubes exceeds 1.5% by mass, the grease immiscibility penetration can be 200 or more. Can be further softened. Further, when the content of the carbon nanotube is 1.0% by mass or more, the grease immiscibility is 210 or less. That is, when the content of the carbon nanotube, that is, the second conductivity imparting agent is 1.0 to 1.5% by mass, the grease immiscibility is 200 to 210.

  The immiscible penetration is a scale indicating the softness of the grease, and the larger the immiscibility penetration, the softer the grease. Further, as the grease sealed in the rolling bearing provided in the main motor of the railway vehicle, a grease having an immiscible consistency of 150 to 350 can be used.

  Note that the grease of the present embodiment may contain a thickener. The thickener is not particularly limited, and any thickener that is usually used as a thickener can be used regardless of whether it is naturally derived or synthetic. Among the commonly used thickeners, it is possible to use, for example, a calcium soap, lithium soap or sodium soap, or a metal soap-based thickener such as a calcium complex soap, an aluminum complex soap or a lithium complex soap. preferable.

  Next, the fact that the rolling bearing of the present embodiment can prevent electrolytic corrosion will be described with reference to FIGS. 1 and 6. FIG. 6 is a diagram schematically showing the cause of electrolytic corrosion occurring in the rolling bearing provided in the railway vehicle. The main motor 10, the bearing 32, the bearing 35, and the wheel 14 shown in FIG. 6 correspond to the main motor 10, the bearing 32, the bearing 35, and the wheel 14 shown in FIG.

  First, consider the case where the lubricant contains a base oil but contains neither carbon black nor carbon nanotubes. In such a case, the lubricant is not imparted with conductivity, and the lubricant has insulating properties. Further, in a railway vehicle, for example, a potential difference is generated between the frame 20 of the main motor 10 and the main shaft 15, so that, for example, between the outer ring 32a and the rolling element 32c, or between the inner ring 32b and the rolling element 32c, or A high electric field may be applied between the outer ring 35a and the rolling element 35c or between the inner ring 35b and the rolling element 35c.

  In such a case, the insulation by the oil film of the lubricant is broken, and between the outer ring 32a and the rolling element 32c, between the inner ring 32b and the rolling element 32c, or between the outer ring 35a and the rolling element 35c, or the inner ring 35b. And a discharge current flows between the rolling elements 35c. That is, a discharge current flows through the bearing 32 or the bearing 35 as a rolling bearing. In this way, a discharge current flows through the bearing 32 or the bearing 35 and a discharge current flows through the outer ring 32a or the inner ring 32b or the outer ring 35a or the inner ring 35b, whereby the surface of the outer ring 32a, the surface of the inner ring 32b, or the surface of the rolling element 32c. Alternatively, the surface of the outer ring 35a, the surface of the inner ring 35b, or the surface of the rolling element 35c is damaged, so that there is a possibility that electrolytic corrosion occurs in the bearing 32 or the bearing 35.

  Moreover, as an example in which a current flows through the bearing 32 or the bearing 35 as a rolling bearing provided in the railway vehicle and the electrolytic corrosion occurs in the bearing 32 or the bearing 35, the first to fourth examples shown in FIG. It is done.

  As a first example shown in FIG. 6, the following phenomenon may be mentioned. Due to the unbalance of the magnetic circuit of the main motor 10, the magnetic circuit resistance changes depending on the rotational position of the armature (rotor), and a voltage is generated in the main shaft 15 (see FIG. 1) due to the change in magnetic flux. May flow. As a result, current easily flows through the bearing 32 or the bearing 35, and there is a possibility that electric corrosion occurs in the bearing 32 or the bearing 35. As shown in FIG. 6, the main motor 10 is electrically connected to the overhead line 51 via the pantograph 50.

  Moreover, the following phenomenon is mentioned as a 2nd example shown in FIG. A voltage is applied via an insulator between the winding of the main motor 10 and the iron core or the magnetic frame, and the winding of the main motor 10 and the iron core or the magnetic frame form a capacitor. And when controlling the electric current which is electrically connected with the main motor 10, and controls the electric current which flows into the coil | winding of the main motor 10 using the control apparatus 52 which consists of a chopper or an inverter, a pulse-form voltage is applied to a coil | winding, There may be transient magnetic flux imbalances. Since the winding of the main motor 10 and the iron core or the magnetic frame form a capacitor, or because a transient magnetic flux imbalance occurs, a current easily flows through the bearing 32 or the bearing 35 by a pulsed voltage. Therefore, there is a possibility that electric corrosion occurs in the bearing 32 or the bearing 35.

  Moreover, the following phenomenon is mentioned as a 3rd example shown in FIG. Since the control device 52 as the main circuit or auxiliary circuit is not sufficiently grounded to the rail 54 via the grounding device 53 and the wheel 14, the current as a part of the grounding current is the bearing 32 or the bearing 35 (see FIG. 1). There is a risk that electrolytic corrosion will occur in the bearing 32 or the bearing 35.

  Moreover, the following phenomenon is mentioned as a 4th example shown in FIG. Between the rails 54 on both sides of the insulation joint 55 of the rail 54, the impedance current is interrupted between the rails 54 on both sides in order to cut off the signal current that is an alternating current and flow a return current that is a direct current. 56 is connected. In such a case, the rails 54 on both sides may be short-circuited via the carriage 57 or the vehicle body of the traveling railway vehicle. As a result, current easily flows through the bearing 32 or the bearing 35, and there is a possibility that electric corrosion occurs in the bearing 32 or the bearing 35.

  As described above, when the lubricant contains the base oil but does not contain carbon black or carbon nanotubes and has an insulating property, there is a possibility that electrolytic corrosion occurs in the bearing 32 or the bearing 35.

  That is, when the lubricant has an insulating property, the bearing 32 or the bearing 35 is provided in the main motor 10 of the railway vehicle. Therefore, the cause specific to the railway vehicle compared to the bearing provided in a normal mechanical device. Therefore, electric corrosion tends to occur. As described with reference to FIG. 6, since the bearing 32 or the bearing 35 is provided in the main motor 10 of the railway vehicle, a current flows through the bearing 32 or the bearing 35 in the path through which electricity flows in the railway vehicle. It differs from a bearing provided in a normal mechanical device in that the path is easy. Further, since the bearing 32 or the bearing 35 is provided in the main motor 10 of the railway vehicle, the dmN value in each of the bearing 32 or the bearing 35 is 300,000 to 800,000, and is provided in a normal mechanical device. It is extremely large compared to the dmN value of the bearing. That is, the problem that electric corrosion occurs in the bearing 32 or the bearing 35 is that the path through which electricity flows in the railway vehicle is a path that facilitates the flow of current through the bearing 32 or the bearing 35, and the bearing 32. Or it is the problem peculiar to the bearing 32 or the bearing 35 with which the dmN value of the bearing 35 is large and which is provided in the main motor 10 of the railway vehicle.

  On the other hand, let us consider a case where the lubricant contains base oil and carbon black but does not contain carbon nanotubes. In such a case, the lubricant contains a base oil, but the lubricant is given conductivity as compared with the case where neither the carbon black nor the carbon nanotube is contained. Therefore, current easily flows between the outer ring 32a and the rolling element 32c, between the inner ring 32b and the rolling element 32c, or between the outer ring 35a and the rolling element 35c, or between the inner ring 35b and the rolling element 35c. Become.

  Therefore, for example, a high electric field is applied between the outer ring 32a and the rolling element 32c, between the inner ring 32b and the rolling element 32c, or between the outer ring 35a and the rolling element 35c, or between the inner ring 35b and the rolling element 35c. Even in this case, the insulation by the oil film of the lubricant is broken and the discharge current does not flow. Therefore, the surface of the outer ring 32a, the surface of the inner ring 32b or the surface of the rolling element 32c, or the surface of the outer ring 35a, the surface of the inner ring 35b or the surface of the rolling element 35c can be prevented or suppressed. It is possible to prevent or suppress the occurrence of electrolytic corrosion on the bearing 32 or the bearing 35 provided in the railway vehicle.

  As shown in FIG. 4, the carbon black 40 has a network structure formed by agglomerating a plurality of particles. In the grease containing the base oil and the carbon black, the carbon black is a semi-solid grease. It is a thickening agent that imparts thickening properties to maintain the shape. However, when shear stress is applied to the grease containing the base oil and carbon black, the network structure of the carbon black is destroyed and the performance as a thickener is reduced, so the separation of the base oil proceeds, The grease hardens. Therefore, the performance of the grease as a lubricant is reduced.

  Thus, it is difficult to improve the lubrication performance of the bearing 32 or the bearing 35 while preventing or suppressing the occurrence of electrolytic corrosion in the bearing 32 or the bearing 35 provided in the railway vehicle.

  On the other hand, the grease of the present embodiment contains a base oil, carbon black, and carbon nanotubes. The strength of carbon nanotubes is higher than that of carbon black having a network structure, and the stability of carbon nanotubes against shear stress, that is, shear stability, is greater than the shear stability of carbon black. Therefore, in the grease of the present embodiment, even when the network structure of carbon black is broken by shear stress, the carbon nanotubes that remain without being broken serve as a thickener, thereby suppressing separation of the base oil. be able to. Moreover, the performance of the grease as a lubricant can be improved by the lubricating effect of the carbon nanotubes themselves.

  In addition, since the grease of this Embodiment also contains carbon black, electroconductivity is provided to grease. Therefore, even when the rolling bearing in which the grease of the present embodiment is sealed is provided in a railway vehicle, the lubrication performance of the rolling bearing can be improved while preventing or suppressing the occurrence of electrolytic corrosion.

  As described above, the problem that electric corrosion occurs in the rolling bearing is a very remarkable problem in the rolling bearing provided in the railway vehicle. Therefore, in the rolling bearing in which the grease of the present embodiment is sealed, the effect of preventing or suppressing the occurrence of electrolytic corrosion and improving the lubrication performance of the rolling bearing is the rolling bearing provided in a normal mechanical device. Greater than the effect on.

  Hereinafter, the present embodiment will be described in more detail based on examples. The present invention is not limited to the following examples.

[Grease sample preparation]
(Comparative Example 1)
As grease of Comparative Example 1, grease containing 86% by mass of mineral oil as base oil and 14% by mass of lithium composite soap as thickener (trade name: Unimax R No. 2, Kyodo Yushi Co., Ltd.) Prepared by the company). The composition of the grease of Comparative Example 1 is shown in Table 1.

(Comparative Example 2)
As a grease of Comparative Example 2, a synthetic ester oil as a 92% by mass base oil, a lithium composite soap as a 3% by mass thickener, and a carbon black as a 5% by mass conductivity imparting agent are contained. (Trade name: Martemp ELK, manufactured by Kyodo Yushi Co., Ltd.) was prepared. The composition of the grease of Comparative Example 2 is shown in Table 1. In Table 1, carbon black is represented by “CB”.

Example 1
As the grease of Example 1, 90% by mass of a synthetic ester oil as a base oil, 3% by mass of a lithium composite soap as a thickener, 5% by mass of carbon black as a conductivity-imparting agent, A grease containing 5% by mass of carbon nanotubes as a conductivity imparting agent was prepared. Specifically, as the grease of Example 1, carbon nanotubes (trade name: VGCF-H, Showa Denko Co., Ltd.) were added to the grease of Comparative Example 2 so that the addition amount (content) was 1.5% by mass. Manufactured) was added (contained). The composition of the grease of Example 1 is shown in Table 1. In Table 1, carbon black is represented by “CB”, and carbon nanotubes are represented by “CNT”.

The carbon nanotube of the trade name VGCF-H manufactured by Showa Denko KK has a fiber diameter of 150 nm, a true density of 2.1 g / cm ³ , a specific surface area of 13 m ² / g, and a thermal conductivity of 1200 W / (mK). And a resistivity of 1 × 10 ⁴ Ωcm. In addition, it is preferable that the average diameter of a carbon nanotube is 10-300 nm, and it is preferable that the average length of a carbon nanotube is 100-500 micrometers.

  In Comparative Example 2 and Example 1, carbon black functions not only as a conductivity-imparting agent that imparts conductivity to grease, but also as a thickening agent that imparts thickening properties to grease. Further, in Example 1, the carbon nanotube is not only a conductivity-imparting agent that imparts conductivity to the grease, but also a thickener that imparts thickness to the grease, and an improvement in lubricity that improves the lubricity of the grease. Also functions as an agent.

  In addition, in Example 1, the amount of carbon nanotubes to be added is such that if the amount added is increased, the consistency becomes small (the grease becomes hard), and there is a possibility that the introduction of grease into the lubrication part of the rolling bearing may be insufficient. The maximum addition amount at which the consistency does not become 200 or less was 1.5% by mass.

(Example 2)
As the grease of Example 2, carbon nanotubes (trade name: VGCF-H, manufactured by Showa Denko KK) were used so that the content of the grease of Comparative Example 2 was 0.5 mass% and 1.0 mass%. Two types of greases with different addition amounts (contents) were prepared.

(Example 3)
As the grease of Example 3, in the grease of Comparative Example 2, two layers were formed so that the content was 0.5% by mass, 1.0% by mass, 5.0% by mass, 10% by mass, and 15% by mass. Five types of greases with different amounts (contents) of carbon nanotubes (double-walled carbon nanotube: DWNT) having a coaxial tubular shape were prepared. In addition, when it becomes a double-layered coaxial tube, it is preferable that the average diameter of a carbon nanotube is 10-300 nm, and it is preferable that the average length of a carbon nanotube is 100-500 micrometers.

[Four ball frictional wear test]
(Comparative Example 1, Comparative Example 2 and Example 1)
Next, with respect to the three types of greases of Comparative Example 1, Comparative Example 2, and Example 1, load resistance evaluation was performed by a four-ball frictional wear test. Specifically, the fusion load, which is a load that causes seizure of any friction surface of the four balls used in the test, was measured. As a result, in Comparative Example 1, the fusion load is 1235N, and in Comparative Example 2, the fusion load is 1744N, whereas in Example 1, the fusion load is 2460N. The fusion load increased for both the grease and the grease of Comparative Example 2. Thereby, it has confirmed that the performance as a lubricant of grease improved by adding a carbon nanotube.

(Comparative Example 2, Example 1, Example 2 and Example 3)
Next, in order to evaluate the optimum range of the carbon nanotube content, four types of greases were used for the nine types of greases of Comparative Example 2, Example 1, Example 2 (2 types) and Example 3 (5 types). The load resistance was evaluated by a frictional wear test, and the fusion load was measured. The result is shown in FIG. FIG. 7 is a graph showing the relationship between the fusion load and the carbon nanotube content.

  As shown in FIG. 7, in Comparative Example 2, the fusion load was 1744N. On the other hand, carbon nanotubes (trade name: VGCF-H, manufactured by Showa Denko KK) are added to the grease of Comparative Example 2 so that the content is 0.5 mass%, 1.0 mass%, and 1.5 mass%. In Examples 1 and 2 which are added greases, the fusion load was 2195 N or more, and the fusion load increased with respect to the grease of Comparative Example 2. Of the data shown as “VGCF” in FIG. 7, the carbon nanotube content of 0% by mass indicates Comparative Example 2, and the carbon nanotube content of 1.5% by mass is implemented. Example 1 is shown, and the carbon nanotube content of 0.5% by mass and 1.0% by mass shows Example 2.

  Further, in Comparative Example 2, the fusion load is 1744 N, whereas the content is 1.0% by mass, 5.0% by mass, 10% by mass, and 15% by mass. In Example 3, which is a grease obtained by adding DWNT carbon nanotubes to the grease, the fusion load was 1960 N or more, and the fusion load increased compared to the grease of Comparative Example 2. In addition, among the data indicated by “DWNT” in FIG. 7, the carbon nanotube content of 0% by mass indicates Comparative Example 2, and the carbon nanotube content is 0.5% by mass and 1.0% by mass. %, 5.0 mass%, 10 mass% and 15 mass% represent Example 3.

  Accordingly, the grease preferably contains 0.5 to 5.0% by mass of carbon nanotubes. When the carbon nanotube content is 0.5 mass% or more, when the carbon nanotube is a trade name VGCF-H manufactured by Showa Denko KK, the carbon nanotube content is less than 0.5 mass%. As a result, the grease performance as a lubricant is improved. On the other hand, when the content of carbon nanotubes is 5.0% by mass or less, compared to the case where the content of carbon nanotubes exceeds 5.0% by mass, the immiscibility of grease can be 195 or more. Can be softened. Further, when the content of the carbon nanotube is 0.5% by mass or more, the grease immiscibility penetration is 215 or less.

  The immiscible penetration is a scale indicating the softness of the grease, and the larger the immiscibility penetration, the softer the grease.

  Moreover, it is more preferable that the grease contains 1.0 to 1.5% by mass of carbon nanotubes. When the carbon nanotube content is 1.0% by mass or more, the carbon nanotube content is 1. regardless of whether the carbon nanotube is a trade name VGCF-H manufactured by Showa Denko KK or DWNT. Compared with the case of less than 0% by mass, the performance of the grease as a lubricant is further improved or is equivalent to the case where the content of carbon nanotubes is 0.5% by mass. On the other hand, when the carbon nanotube content is 1.5% by mass or less, the consistency can be increased to 200 or more, and the grease becomes softer than when the carbon nanotube content exceeds 1.5% by mass. be able to. Further, when the content of the carbon nanotube is 1.0% by mass or more, the grease immiscibility is 210 or less.

[Lubrication life test using full-scale bearings]
Next, for the two types of greases of Comparative Example 2 and Example 1, the lubricating performance was evaluated by a lubrication life test using a full-size bearing having a size approximately equal to the rolling bearing of the main motor provided in the railway vehicle. . Specifically, the grease described in FIG. 3 is filled with the grease of any one of Comparative Example 2 and Example 1, and the traveling condition of the maximum traveling speed of 130 km / h is simulated, and an important part of the railway vehicle A lubrication life test, which is a bearing rotation test equivalent to 600,000 km running corresponding to the inspection cycle, was performed. After the lubrication life test was completed, the appearance of the roller bearing was examined. The results are shown in Table 2.

  After the lubrication life test was completed, the grease collected from the roller bearing was analyzed. Specifically, 0.3 g of grease as an analysis sample was collected from a cage. And the consistency (spreadness consistency) of the collected sample for analysis was measured. Further, the content of the metal contained in the collected analysis sample was measured by ICP (Inductively Coupled Plasma) emission spectrometry after dissolving the sample with an acid. Further, the oil separation rate of the collected analysis sample was measured by a method in which the analysis sample was dispersed in normal hexane and the solid content was filtered with a membrane filter. The results are shown in Table 2.

  In Comparative Example 2, as a result of an external appearance investigation, a bluish-purple discoloration considered to have occurred due to heat generation due to poor lubrication was observed on the raceway surface of the inner ring. Further, in Comparative Example 2, a large amount of the wear powder of the cage was included in the grease adhering to the cage. From these facts, in Comparative Example 2, it is presumed that the cage was worn due to poor lubrication.

  On the other hand, in Example 1, as a result of the appearance investigation, no abnormality was observed except that brown coloring was observed on the raceway surface of the inner ring.

  As shown in Table 2, in Comparative Example 2, the grease collected from the cage was analyzed. As a result, the collected grease was extremely hardened, and the consistency could not be measured. Further, since the copper content in the collected grease was as extremely high as 6.40% by mass, it was shown that the wear of the cage was remarkably progressing. Further, the oil separation rate in the collected grease was as large as 21.8%.

  On the other hand, as shown in Table 2, in Example 1, the grease collected from the cage was analyzed, and as a result, the consistency of the collected grease was 191 and the consistency of the grease before the lubrication life test was The grease was slightly cured by performing a lubrication life test slightly smaller than 200. However, both the iron content and the copper content in the grease sampled in Example 1 are smaller than the iron content and the copper content in the grease sampled in Comparative Example 2. The oil separation rate in the grease sampled in 1 was smaller than the oil separation rate in the grease sampled in Comparative Example 2.

  Thus, as a result of conducting a lubrication life test using a full-scale bearing, the grease of Comparative Example 2 in which only carbon black was added as a conductivity imparting agent resulted in poor lubrication of the roller bearing. As a result, it was confirmed that the grease of Example 1 to which carbon black and carbon nanotubes were added had a durability equivalent to 600,000 km running without causing poor lubrication of the roller bearing.

  The reason why the lubrication failure occurred in the grease of Comparative Example 2 can be considered as follows using FIG. FIG. 8 is a diagram schematically showing the microstructure of the grease of Comparative Example 2 before and after the lubrication life test.

  In Comparative Example 2, the carbon black 40 added to the grease has a network structure in which a plurality of particles are aggregated as shown in FIG. In the grease of Comparative Example 2, the carbon black 40 is used as a conductivity-imparting agent that imparts conductivity to the grease by utilizing the network structure of the carbon black 40, and increases the consistency of the grease to reduce the grease by half. It is used as a thickener that keeps it in a solid state. When shear stress is applied to the grease inside the rolling bearing, as shown in FIG. 8B, the network structure of the carbon black 40 is destroyed and the performance as a thickener is lowered, so that the oil content is separated. (Oil release) is promoted. Thereby, the value of the oil separation rate is increased, and it is considered that curing has progressed.

  On the other hand, the reason why the lubrication failure did not occur in the grease of Example 1 is considered as follows using FIG. FIG. 9 is a diagram schematically showing the fine structure of the grease of Example 1 before and after the lubrication life test.

  Also in Example 1, as in Comparative Example 2, the carbon black 40 added to the grease has a network structure in which a plurality of particles are aggregated as shown in FIG. 9A. On the other hand, in Example 1, unlike Comparative Example 2, as shown in FIG. 9A, carbon nanotubes 41 are added to the grease. The strength of the carbon nanotubes 41 added to the grease is higher than the strength of the carbon black 40 having a network structure, and the stability of the carbon nanotubes 41 against the shear stress, that is, the shear stability is higher than the shear stability of the carbon black 40. large.

  In the grease of Example 1 as well as the grease of Comparative Example 2, when a shear stress is applied to the grease inside the rolling bearing, the network structure of the carbon black 40 is destroyed as shown in FIG. 9B. The However, in the grease of Example 1, unlike the grease of Comparative Example 2, as shown in FIG. 9B, even when the network structure of the carbon black 40 is destroyed, the carbon nanotubes 41 remain without being destroyed. Since the remaining carbon nanotubes 41 serve as a thickener, the separation of the base oil can be suppressed. Moreover, the performance of the grease as a lubricant can be improved by the lubricating effect of the carbon nanotubes 41 themselves.

[Energized rotation test using small bearings]
Next, with respect to the three types of greases of Comparative Example 1, Comparative Example 2, and Example 1, electrolytic corrosion prevention performance evaluation was performed by an energization rotation test using a small bearing as shown in FIG. FIG. 10 is a diagram schematically showing an energization rotation test apparatus using a small bearing.

Specifically, the grease 62 of Comparative Example 2 and Example 1 is sealed in a bearing 62 similar to the deep groove ball bearing described with reference to FIG. 2 described above, and the energization rotation test apparatus shown in FIG. 10 is used. A radial load (radial load) FR1 of 180 N is applied and rotated at a rotational speed of 1000 min ⁻¹ . This load is set so that the maximum contact surface pressure between the ball 62c and the raceway surface of the outer ring 62a or the inner ring 62b is substantially equal to the radial load of the rolling bearing of the main motor provided in the actual railway vehicle. is there.

  By connecting the positive and negative electrode terminals of the DC power supply 67 to the housing 64 in contact with the outer ring 62a and the rotary connector 66 attached to the rotary shaft 65 in contact with the inner ring 62b, current as a DC current is generated inside the bearing 62. Washed away. When direct current is applied, it is said that traces of electrolytic corrosion occur on the negative track surface. However, after the test, evaluation is performed using the inner ring 62b that is easy to handle when observing the surface state. The raceway surface of the outer ring 62a is on the positive electrode side, and the raceway surface of the inner ring 62b is on the negative electrode side. Further, in consideration of the allowable current of the rotary connector 66 and the like, a current density of 6A is provided so that a current density capable of reliably generating electrolytic corrosion in a relatively short time when a test is performed with conductive grease. An electric current 67a was supplied. In addition, current was passed for 360 hours. The current flowing in the bearing 62 was measured as an electric current 67a by an ammeter 68, and the voltage between the positive and negative electrode terminals of the DC power supply 67 was measured by a voltmeter 69.

  As a result, when the grease of Comparative Example 1 was sealed, a ridge mark was generated on the raceway surface of the inner ring 62b. Therefore, it was found that the electrolytic corrosion preventing performance of the grease of Comparative Example 1 was small. This is considered to be because, for example, the grease of Comparative Example 1 does not contain a conductivity-imparting agent and has insulating properties.

  Further, when the grease of Comparative Example 2 was sealed, a ridge mark was generated on the raceway surface of the inner ring 62b, although it was slight compared with the case of sealing the grease of Comparative Example 1. Therefore, it was found that the electrolytic corrosion prevention performance of the grease of Comparative Example 2 is larger than the electrolytic corrosion prevention performance of the grease of Comparative Example 1, but not so great. This is considered because the network structure of carbon black is destroyed by applying a shear stress to the grease as described with reference to FIG.

  On the other hand, when the grease of Example 1 was sealed, no ridge mark was generated on the raceway surface of the inner ring 62b in appearance. Therefore, it was found that the electrolytic corrosion prevention performance of the grease of Example 1 is larger than the electrolytic corrosion prevention performance of the greases of Comparative Examples 1 and 2. Therefore, it has been confirmed that the addition of carbon nanotubes to the grease containing base oil and carbon black improves the electrolytic corrosion prevention performance of the grease.

  Although details are omitted, when the grease as the lubricant contains base oil and carbon nanotubes but does not contain carbon black, a ridge mark is generated on the raceway surface of the inner ring. did. Therefore, when the grease contains base oil and carbon nanotubes, but does not contain carbon black, the electrolytic corrosion prevention performance is smaller than when grease contains base oil and carbon black. I understood. This is because, for example, when the grease contains base oil and carbon nanotubes but does not contain carbon black, the grease has a volume resistivity compared to the case where the grease contains base oil and carbon black. This is thought to increase.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In the scope of the idea of the present invention, those skilled in the art can conceive various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention.

  For example, those in which the person skilled in the art appropriately added, deleted, or changed the design of the above-described embodiments, or those in which the process was added, omitted, or changed the conditions are also included in the present invention. As long as the gist is provided, it is included in the scope of the present invention.

  The present invention is effective when applied to a rolling bearing provided in a railway vehicle.

DESCRIPTION OF SYMBOLS 10 Main motor 11 Coupling 12 Driving device 13 Axle 14 Wheel 15 Main shaft 16 Small gear 17 Small gear 17 Large gear 20 Frame 21 Stator 21a Coil 22 Rotor 30, 31 Bearing device 32, 35, 62 Bearing 32a, 35a, 62a Outer ring 32b, 35b, 62b Inner ring 32c, 35c Rolling elements 32d, 35d Cage 33, 34, 36, 37 Lid 40 Carbon black 41 Carbon nanotube 50 Pantograph 51 Overhead line 52 Control device 53 Grounding device 54 Rail 55 Insulation seam 56 Impedance bond 57 Carriage 62c Ball 64 Housing 65 Rotating shaft 66 Rotary connector 67 DC power supply 67a Current 68 Ammeter 69 Voltmeter FR1 Load

Claims (6)

In rolling bearings provided in the main motors of railway vehicles,
Inner ring,
An outer ring surrounding the inner ring;
A plurality of rolling elements disposed between the inner ring and the outer ring;
A lubricant encapsulated between the inner ring and the outer ring;
Have
The lubricant is
Base oil,
A first conductivity imparting agent comprising carbon black and imparting conductivity to the lubricant;
A second conductivity imparting agent comprising carbon nanotubes and imparting conductivity to the lubricant;
Containing rolling bearings. The rolling bearing according to claim 1,
The lubricant is a rolling bearing containing 0.5 to 5.0% by mass of the second conductivity-imparting agent. The rolling bearing according to claim 1,
The lubricant is a rolling bearing containing 1.0 to 1.5% by mass of the second conductivity-imparting agent. The rolling bearing according to claim 2,
A rolling bearing having an immiscibility of the lubricant of 195 to 215. In the rolling bearing according to claim 3,
A rolling bearing having an immiscibility of the lubricant of 200 to 210. In the rolling bearing as described in any one of Claims 1 thru | or 5,
The rolling bearing has a dmN value of 300,000 to 800,000.

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