Bearing insulation cover and rolling bearing

Abstract

To actualize the insulation of a rolling bearing without applying insert molding of an insulation resin to a bearing ring.SOLUTION: A bearing insulation cover includes a first cylindrical resin surface 2 formed on one of the inside and the outside of a cylindrical resin part so as to be fitted into a mating face of a bearing ring, a second cylindrical resin surface 3 formed on the other of the inside and the outside of the cylindrical resin part, and a first protruded resin part 4 for being axially caught on the side face on the axial single side of the bearing ring when the first cylindrical resin surface 2 is in a fitted state of being fitted into the mating face of the bearing ring, the first cylindrical resin surface 2, the second cylindrical resin surface 3, and the first protruded resin part 4 being integrally formed. The first cylindrical resin surface 2 includes a second protruded resin part 2c for being axially caught on the side face on the opposite side to the axial single side of the bearing ring when in the fitted state. At least one of the cylindrical resin surfaces 2, 3 has irregularities 2b, 2a, 3b, 3a extending over the whole widths of the cylindrical resin surfaces 2, 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin insulating cover for a shaft, which is attached to a raceway ring to insulate a rolling bearing, and a rolling bearing including the same.

Background Art

[0002] In the case of a rolling bearing that supports a rotating part of a device that uses electricity, such as an electric motor or an e-Axle in which an electric motor and a speed reducer are integrated, a voltage may be applied to the rolling bearing. When electricity flows from the outer ring to the inner ring side or from the inner ring to the outer ring side of the rolling bearing due to this voltage, electric corrosion occurs at the contact portions between the rolling elements of the rolling bearing and the outer and inner rings. Conventionally, measures have been taken to insulate the rolling bearing in order to prevent such electric corrosion.

[0003] As a measure for insulation, there is a method in which a resin having high insulation is insert-molded into a raceway ring (inner ring or outer ring), and the fitting surface and side surface of the raceway ring are coated with the resin (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the insert molding, in order to integrate the resin that coats the raceway ring and the raceway ring, the resin is filled in a circumferential groove formed by shaving the vicinity of the raceway surface of the raceway ring. There are many precautions such as removing gate marks after insert molding, masking to prevent dust from adhering to the raceway surface during post-processing after molding, and cleaning, which leads to an increase in cost and there is room for improvement.

[0006] In view of the above background, the problem to be solved by the present invention is to insulate the rolling bearing without performing insert molding of insulating resin on the raceway ring.

Means for Solving the Problem

[0007] To solve the above problems, the present invention includes a first cylindrical resin surface formed on one side inside and outside of a cylindrical resin portion so as to be fitted into the fitting surface of a raceway ring, a second cylindrical resin surface formed on the other side inside and outside of the cylindrical resin portion, and a first protruding resin portion that axially catches on the side surface on one axial side of the raceway ring when the first cylindrical resin surface is fitted into the fitting surface of the raceway ring. The first cylindrical resin surface, the second cylindrical resin surface, and the first protruding resin portion are integrally formed. The first cylindrical resin surface includes a second protruding resin portion that axially catches on the side surface opposite to the one axial side of the raceway ring in the fitted state. The present invention adopts Configuration 1, which is a bearing insulating cover in which one or both of the first cylindrical resin surface and the second cylindrical resin surface are formed with irregularities.

[0008] According to Configuration 1 above, when the first cylindrical resin surface is fitted into the fitting surface of the raceway ring and the first protruding resin portion and the second protruding resin portion are axially caught on the side surfaces on both axial sides of the raceway ring to be in a fitted state, the bearing insulating cover can be attached to the raceway ring. When the raceway ring with the bearing insulating cover is fitted into the corresponding mechanical element, the cylindrical resin portion having the first cylindrical resin surface and the second cylindrical resin surface is sandwiched between the bearing seat of the corresponding mechanical element and the fitting surface of the raceway ring, so that insulation can be achieved between the two. In this way, if the rolling bearing is insulated by the bearing insulating cover attached to the raceway ring, it becomes unnecessary to perform insert molding of insulating resin on the raceway ring.

[0009] If the shaft insulating cover is configured as a simple cylinder, a tightening allowance for attaching the shaft insulating cover to the race ring is set between the fitting surface of the race ring and the first cylindrical resin surface, and the dimensional accuracy in the radial direction of the cylindrical resin portion having the first cylindrical resin surface and the second cylindrical resin surface must be strictly controlled. That is, if the aforementioned tightening allowance becomes loose, there is a concern that the shaft insulating cover may naturally come out of the race ring due to temperature changes, vibrations, etc. during the use of the rolling bearing, and the insulation performance cannot be stably maintained. On the other hand, if the tightening allowance becomes too tight, it becomes difficult to fit it into the fitting surface of the race ring. Also, if the radial difference between the second cylindrical resin surface and the first cylindrical resin surface becomes too large, the surface pressure of each mating surface among the three between the fitting surface of the shaft insulating cover, the fitting surface of the race ring, and the corresponding mechanical element may become excessive, which may have an adverse effect on the rolling bearing.

[0010] On the contrary, if the prevention of the shaft insulating cover from coming off the race ring is performed by the first protruding resin portion and the second protruding resin portion as in the above configuration 1, it is possible to prevent the shaft insulating cover from coming out without setting a tight tightening allowance between the fitting surface of the race ring and the first cylindrical resin surface. Also, even if the tightening allowance between the fitting surface of the race ring and the first cylindrical resin surface becomes large, since one or both of the first cylindrical resin surface and the second cylindrical resin surface are formed with irregularities, it is possible to fit the first cylindrical resin surface into the fitting surface of the race ring by improving the circumferential stretchability in the concave part. Also, when the mating surface pressure among the three between the shaft insulating cover, the fitting surface of the race ring, and the bearing seat of the corresponding mechanical element becomes high, the convex part is radially pressed between the fitting surface of the race ring and the corresponding mechanical element and flattened so as to spread toward the concave part, thereby reducing the mating surface pressure. Therefore, according to the above configuration 1, it is possible to relax the dimensional accuracy in the radial direction of the first cylindrical resin surface and the second cylindrical resin surface (that is, to eliminate the post-processing cost of improving the dimensional accuracy of the first cylindrical resin surface and the second cylindrical resin surface after resin molding), while stably maintaining the insulation performance during the use of the rolling bearing and preventing adverse effects on the rolling bearing.

[0011] In the above-described Configuration 1, a Configuration 2 can be adopted in which the first protruding resin portion is provided so as to overlap with the width surface on one axial side of the track wheel.

[0012] According to the above-described Configuration 2, when fitting the track wheel with an axial bearing insulating cover to the corresponding mechanical element, the first protruding resin portion can be sandwiched between the width surface on one axial side of the track wheel and the corresponding mechanical element, and insulation can be achieved between the two, and also, the concern that the axial bearing insulating cover separates axially from the track wheel during the use of the rolling bearing can be eliminated.

[0013] In the above-described Configuration 1 or 2, a Configuration 3 can be adopted in which the radial height of the second protruding resin portion is provided to be 0.3 mm or less.

[0014] If the radial heights of both the first protruding resin portion and the second protruding resin portion are increased, it becomes difficult to fit the first cylindrical resin surface to the fitting surface of the track wheel. For the second protruding resin portion located on the first cylindrical resin surface that is fitted to the fitting surface of the track wheel, the fitting property can be improved by reducing its radial height. The radial height of the second protruding resin portion may be set within a range that can ensure a state where the track wheel and the second protruding resin portion face each other axially even in the use state of the rolling bearing. When the fit between the track wheel and the corresponding mechanical element is a clearance fit, the generally adopted fit clearance is less than 0.3 mm. Therefore, it is not preferable that the radial height of the second protruding resin portion exceeds 0.3 mm as it is an excessive setting.

[0015] In any one of the above-described Configurations 1 to 3, a Configuration 4 can be adopted in which the first cylindrical resin surface and the second cylindrical resin surface each have the unevenness, and the recesses of the unevenness of the first cylindrical resin surface and the recesses of the unevenness of the second cylindrical resin surface face each other in the radial direction.

[0016] When the unevenness of the first cylindrical resin surface and the unevenness of the second cylindrical resin surface are formed in such a relationship that the recesses face each other in the radial direction as in the above configuration 4, the opposing portions of the recesses become particularly thin, and when the first cylindrical resin surface is fitted into the fitting surface of the raceway ring, it becomes easy to expand and contract in the circumferential direction. Therefore, compared with the case where only one of the first cylindrical resin surface and the second cylindrical resin surface has unevenness, the fitting property of the first cylindrical resin surface to the fitting surface of the raceway ring can be improved.

[0017] In any one of the above configurations 1 to 4, the configuration 5 in which the unevenness of the one or both cylindrical resin surfaces is equally distributed at a plurality of locations in the circumferential direction can be adopted.

[0018] Further, a rolling bearing including the raceway ring into which the insulating cover for a shaft according to any one of the above configurations 1 to 5 is fitted, another raceway ring facing the raceway ring in the radial direction, and a plurality of rolling elements disposed between the raceway ring and the other raceway ring, the configuration 6 can be adopted.

Advantages of the Invention

[0019] As described above, by adopting the above configuration 1, the present invention can insulate the rolling bearing without performing insert molding of the insulating resin on the raceway ring.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0021] The insulating cover for a shaft according to the first embodiment as an example of the present invention and the rolling bearing including the same will be described based on FIGS. 1 to 6 of the accompanying drawings.

[0022] The insulating cover 1 for a shaft shown in FIGS. 1 and 2 is for insulating the rolling bearing 10 as shown in FIGS. 3 to 6.

[0023] As shown in FIGS. 1 and 2, the insulating cover 1 for a shaft includes a first cylindrical resin surface 2 formed on the inner side as one of the inner and outer sides of the cylindrical resin portion, a second cylindrical resin surface 3 formed on the outer side as the other of the inner and outer sides of the cylindrical resin portion, and a first protruding resin portion 4 extending in a flange shape from one axial side of the first cylindrical resin surface 2.

[0024] The first cylindrical resin surface 2, the second cylindrical resin surface 3, and the first protruding resin portion 4 are integrally formed of resin. The entire insulating cover 1 for a shaft is formed integrally without joints by injection molding.

[0025] As shown in FIGS. 3, 5, and 6, the rolling bearing 10 includes a raceway ring 11, another raceway ring 12 that faces the raceway ring 11 in the radial direction, a plurality of rolling elements 13 disposed between the raceway ring 11 and the other raceway ring 12, and a cage 14 that holds the rolling elements 13.

[0026] Here, the circumferential direction around the central axis of the raceway ring 11 of the rolling bearing 10 is referred to as the "circumferential direction", the direction along the central axis is referred to as the "axial direction", and the direction perpendicular to the central axis is referred to as the "radial direction". Note that the axial direction corresponds to the left - right direction in FIG. 5, and the radial direction corresponds to the up - down direction in FIG. 5. Also, the concepts of the "inner or outer side of the cylindrical resin part" and the "other inner or outer side of the cylindrical resin part" mean the inside and outside in the radial direction. The "inner side" means the side approaching the central axis of the raceway ring 11 in the radial direction, and the "outer side" means the side away from the central axis of the raceway ring 11 in the radial direction.

[0027] The raceway ring 11, the other raceway ring 12, and the rolling elements 13 are each formed of a metal, for example, steel.

[0028] The rolling bearing 10 has bearing main dimensions defined in standard specifications such as JIS standards and ISO standards, for example.

[0029] The raceway ring 11 and the other raceway ring 12 each have a fitting surface that defines the bearing inner diameter or the bearing outer diameter of the bearing main dimensions, both end width surfaces that define the bearing width of the bearing main dimensions, and chamfers on both sides with a chamfer width defined in the bearing main dimensions.

[0030] Note that in the illustrated example, the case where the raceway ring 11 to which the insulating cover 1 for the bearing is attached is the outer ring is shown.

[0031] The fitting surface 11a formed at the central portion of the outer periphery of the track wheel 11 has a cylindrical surface shape along the axial direction. The chamfer 11b formed on the fitting surface 11a side of the track wheel 11 is continuous over the entire circumference in the circumferential direction with a cross-sectional shape that becomes radially farther from the fitting surface 11a as it becomes axially farther from the fitting surface 11a. The width surfaces 11c respectively formed at both axial ends of the track wheel 11 are continuous over the entire circumference in the circumferential direction with a constant width along the radial direction.

[0032] The shaft insulating cover 1 is designed to be attached to the track wheel 11 on the premise of the specified dimensions of the fitting surface 11a, the chamfer 11b, and the width surface 11c of the track wheel 11, so that the track wheel 11 with the shaft insulating cover 1 can insulate the required part of the corresponding mechanical element.

[0033] In the illustrated example, as the required part of the corresponding mechanical element, the bearing seat Hi and the shoulder Hs of the housing surrounding the shaft S provided in the rotating electrical machine are assumed, and it is assumed that a relative potential difference may occur between the potential of the housing having the bearing seat Hi and the shoulder Hs and the potential of the shaft S.

[0034] Examples of such a rotating electrical machine include an electric motor of an EV vehicle, an e-Axle, etc. At present, the mainstream system voltage of EV vehicles is 400V, but it is expected that the voltage will increase to about 1000V in the future. When the system voltage is 1000V, the relative potential difference of the shaft S with respect to the bearing seat Hi and the shoulder Hs of the housing is considered to be about 1 / 10 of the system voltage. That is, the voltage applied to the rolling bearing 10 interposed between the housing having the bearing seat Hi and the shoulder Hs and the shaft S is expected to be about 100V. Therefore, the shaft insulating cover 1 is designed to be able to insulate against an applied voltage of 100V.

[0035] As shown in FIGS. 1 and 2, the first cylindrical resin surface 2 and the second cylindrical resin surface 3 extend in a substantially concentric cylindrical shape with each other. As shown in FIGS. 3, 5, and 6, the first cylindrical resin surface 2 is fitted into the fitting surface 11a of the track wheel 11. The second cylindrical resin surface 3 is fitted into the bearing seat Hi of the corresponding mechanical element. The cylindrical resin portion formed with the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is radially sandwiched between the fitting surface 11a of the track wheel 11 and the bearing seat Hi of the corresponding mechanical element.

[0036] A radial tightening allowance is set between the fitting surface 11a of the track wheel 11 and the first cylindrical resin surface 2. By setting this tightening allowance, radial contact between the first cylindrical resin surface 2 and the fitting surface 11a of the track wheel 11 is ensured, and elastic tightening at the contact portion is realized, so that the mounting strength can be obtained to prevent the insulating cover 1 for bearing from falling off the track wheel 11 due to its own weight. The insulating cover 1 for bearing is attached to the track wheel 11 by being press-fitted into the fitting surface 11a of the track wheel 11 on the first cylindrical resin surface 2. At this time, as shown in FIGS. 3 to 6, the first cylindrical resin surface 2 is in a fitted state fitted into the fitting surface 11a of the track wheel 11. On the other hand, the second cylindrical resin surface 3 is clearance-fitted with the bearing seat Hi of the corresponding mechanical element.

[0037] As shown in FIG. 5, the first protruding resin portion 4 is formed so as to be axially hooked on the side surface of one axial side of the track wheel 11 (the right side in FIG. 5. Hereinafter, the side corresponding to this side is referred to as the "right side") when the first cylindrical resin surface 2 is in a fitted state fitted into the fitting surface 11a of the track wheel 11.

[0038] The first cylindrical resin surface 2 and the second cylindrical resin surface 3 have the same width, but this width is shorter than the total width of the inner and outer circumferences of the shaft insulating cover 1. Among the shaft insulating cover 1, the resin portion outside the width of the first cylindrical resin surface 2 constitutes the first protruding resin portion 4. The first protruding resin portion 4 is continuous with the right side of the first cylindrical resin surface 2 over the entire circumference in the circumferential direction and extends in a flange shape from this continuous portion. The first protruding resin portion 4 is overlapped with the right width surface 11c of the race ring 11 at its flange-shaped portion. The first protruding resin portion 4 abuts axially against the shoulder Hs of the corresponding mechanical element at its flange-shaped portion and is axially sandwiched between the right width surface 11c of the race ring 11 and the shoulder Hs.

[0039] The above-described fitting state is a state in which the first cylindrical resin surface 2 and the second cylindrical resin surface 3 face the entire fitting surface 11a of the race ring 11 in the radial direction and the first protruding resin portion 4 is axially hooked on the right side surface of the race ring 11. In this fitting state, the first protruding resin portion 4 can completely cover the right width surface 11c and the chamfer of the race ring 11 from the radially outer side and the axially right side. When a sufficient creepage distance can be ensured by the resin surface of the shaft insulating cover 1 between the right side surface of the race ring 11 and the shoulder Hs of the corresponding mechanical element, in the case of a mechanical element without a shoulder Hs, etc., when there is no problem with insulation between the race ring 11 and the corresponding mechanical element, it is not necessary for the first protruding resin portion 4 to cover the entire right side surface of the race ring 11.

[0040] According to the IEC60664-1 Ed2.0 standard, regardless of the material group of the insulating material forming the creepage surface, if the creepage distance is 0.3 mm, it is possible to insulate up to an effective voltage of 100 V. That is, in the rolling bearing 10 interposed between the bearing seat Hi and the shoulder Hs of the corresponding mechanical element and the shaft S, the creepage distance required to achieve insulation against the assumed applied voltage of 100 V is 0.3 mm or more. For example, when the thickness of the first protruding resin portion 4 is 0.3 mm or more, it is not necessary for the first protruding resin portion 4 to shield the entire right side surface of the race ring 11 and the shoulder Hs of the corresponding mechanical element.

[0041] The axial protruding length of the first cylindrical resin surface 2 and the first protruding resin portion 4 of the second cylindrical resin surface 3 is provided to be longer than the full width of the track wheel 11. In this way, when the first cylindrical resin surface 2 and the second cylindrical resin surface 3 protrude axially from the left side surface of the track wheel 11 in the above-described fitting state, it is possible to prevent other elements that destroy the insulation of the rolling bearing 10, such as a housing lid, from being arranged near the track wheel 11 on the side opposite to the shoulder Hs of the corresponding mechanical element (left side).

[0042] As the resin forming the insulating cover 1 for the bearing, for example, one having a dielectric breakdown strength of 500 V / mm or more can be adopted. Here, the dielectric breakdown strength means a value measured by a test method conforming to ASTM D149 Step-by-Step Test.

[0043] Also, as the resin forming the insulating cover 1 for the bearing, for example, one having a comparative surface electric resistance index of 600 V or more can be adopted. Here, the comparative surface electric resistance index means the CTI value measured in the tracking resistance test conforming to IEC60112 standard. Examples of such resins include PPS and PPA. Further, the resin forming the insulating cover 1 for the bearing may be either a thermoplastic resin or a thermosetting resin, and may contain a reinforcing material such as glass fiber.

[0044] As shown in FIGS. 3, 5, and 6, the first cylindrical resin surface 2 has irregularities (2b, 2a) formed by a convex 2a which is a surface portion capable of contacting the fitting surface 11a of the track wheel 11 in the radial direction and a concave 2b which is a surface portion incapable of contacting the fitting surface 11a in the radial direction at a plurality of locations in the circumferential direction. Also, the second cylindrical resin surface 3 has irregularities (3b, 3a) formed by a convex 3a which is a surface portion capable of contacting the bearing seat Hi of the corresponding mechanical element in the radial direction and a concave 3b which is a surface portion incapable of contacting the bearing seat Hi in the radial direction at a plurality of locations in the circumferential direction.

[0045] As shown in FIGS. 1 and 2, the unevenness (2b, 2a) of the first cylindrical resin surface 2 and the unevenness (3b, 3a) of the second cylindrical resin surface 3 extend over the entire width of the first cylindrical resin surface 2 or the second cylindrical resin surface 3, respectively.

[0046] As shown in FIGS. 1 and 2, the protrusions 2a of the first cylindrical resin surface 2 and the protrusions 3a of the second cylindrical resin surface 3 are formed at a constant pitch over the entire circumference in the circumferential direction. Also, the recesses 2b of the first cylindrical resin surface 2 and the recesses 3b of the second cylindrical resin surface 3 are formed between the corresponding adjacent protrusions 2a or 3a in the circumferential direction, and are in the shape of grooves connecting the adjacent protrusions 2a or 3a. These unevennesses (2b, 2a, 3b, 3a) extend in a direction orthogonal to the circumferential direction and cross the first cylindrical resin surface 2 or the second cylindrical resin surface 3. In the drawing, the direction in which these unevennesses (2b, 2a, 3b, 3a) extend is set as the axial direction.

[0047] The unevenness (2b, 2a) of the first cylindrical resin surface 2 and the unevenness (3b, 3a) of the second cylindrical resin surface 3 are continuously connected in a wave shape that advances without interruption over the entire circumference in the circumferential direction with a constant period and in the radial direction with a constant amplitude. The first cylindrical resin surface 2 is composed of three or more protrusions 2a and recesses 2b equally arranged in the circumferential direction, and the second cylindrical resin surface 3 is the same.

[0048] Each of the protrusions 2a, 3a is the highest in the radial direction with respect to the adjacent recesses 2b, 3b at the central portion in the circumferential direction of the protrusions 2a, 3a, and becomes lower in the radial direction as it goes from the central portion in the circumferential direction to both sides in the circumferential direction. The height change rate of each of the protrusions 2a, 3a per unit length in the circumferential direction is set lower the closer it is to the central portion in the circumferential direction. Each of the recesses 2b, 3b is the lowest in the radial direction with respect to the adjacent protrusions 2a, 3a at the central portion in the circumferential direction of the recesses 2b, 3b, and becomes higher in the radial direction as it goes from the central portion in the circumferential direction to both sides in the circumferential direction. The height change rate of each of the recesses 2b, 3b per unit length in the circumferential direction is set lower the closer it is to the central portion in the circumferential direction.

[0049] As shown in FIG. 3, the radial tightening allowance for press-fitting the fitting surface 11a of the track wheel 11 and the shaft insulating cover 1 is set based on the diameter of the virtual circle that contacts the circumferential center portion of each convex 2a of the first cylindrical resin surface 2 and the diameter of the fitting surface 11a.

[0050] As shown in FIGS. 4 to 6, the fitting clearance between the track wheel 11 with the shaft insulating cover 1 and the bearing seat Hi of the corresponding mechanical element is set based on the diameter of the virtual circle that contacts the circumferential center portion of each convex 3a of the second cylindrical resin surface 3 and the diameter of the bearing seat Hi of the corresponding mechanical element. The fitting clearance is usually set to less than 0.3 mm.

[0051] As shown in FIGS. 1 and 2, when the unevenness (2b, 2a) of the first cylindrical resin surface 2 and the unevenness (3b, 3a) of the second cylindrical resin surface 3 are formed, the thickness of the resin can be reduced at the recesses 2b and 3b (that is, the rigidity of the shaft insulating cover 1 can be partially reduced). Therefore, when press-fitting the fitting surface 11a of the track wheel 11 and the second cylindrical resin surface 3 of the shaft insulating cover 1, it becomes easier to expand and contract in the circumferential direction at the recesses 2b and 3b, so the cylindrical resin portion having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is more likely to deform in the radial direction to reduce the tightening allowance. In particular, when the recesses 2b of the first cylindrical resin surface 2 and the recesses 3b of the second cylindrical resin surface 3 face each other in the radial direction as in the illustrated example, the thickness between the first cylindrical resin surface 2 and the second cylindrical resin surface 3 becomes particularly thin at the facing portion, so it becomes particularly easy to expand and contract in the circumferential direction during the above-mentioned press-fitting.

[0052] Note that the shaft insulating cover 1 has no weld. If a weld occurs in the recesses 2b and 3b during injection molding, it will become a vulnerable part for expansion and contraction in the circumferential direction, which is not preferable. When setting the circumferential pitch of the recesses 2b and 3b to be small as in the illustrated example, it is difficult to control the resin flow so that no weld occurs in the recesses 2b and 3b when adopting injection molding using a pinpoint gate. If the shaft insulating cover 1 is formed by injection molding using a disk gate, the occurrence of welds can be eliminated.

[0053] As shown in FIGS. 3 and 4, the first cylindrical resin surface 2 includes a second protruding resin portion 2c that is axially hooked on the side surface on the side opposite to one axial side of the track wheel 11 (the left side in FIGS. 3 to 5; hereinafter, the side corresponding to this opposite side is referred to as the "left side") in the above-described fitting state. As shown in FIGS. 1, 2, and 4, among the three or more protrusions 2a of the first cylindrical resin surface 2, a plurality of protrusions 2a spaced apart in the circumferential direction include the second protruding resin portion 2c, and the other protrusions 2a do not include the second protruding resin portion 2c. Each second protruding resin portion 2c is composed of a part located on the left side of the fitting surface 11a of the track wheel 11 in the above-described fitting state among the central portions in the circumferential direction of the protrusion 2a, and protrudes higher in the radial direction than the remaining portion of the central portion.

[0054] These second protruding resin portions 2c are located on the same circumference, and the diameter difference between the diameter of the contact circle with respect to these second protruding resin portions 2c and the diameter of the fitting surface 11a of the track wheel 11 is larger than the radial tightening allowance between the other portion of the convex 2a and the fitting surface 11a of the track wheel 11. For this reason, if the radial height of each second protruding resin portion 2c is larger than necessary, it becomes difficult to fit the first cylindrical resin surface 2 onto the fitting surface 11a of the track wheel 11. To avoid this, the radial height of the second protruding resin portion 2c is provided to be 0.3 mm or less. If the radial height of the second protruding resin portion 2c (see FIGS. 1 and 2) is 0.3 mm or less, during the above-mentioned fitting, each second protruding resin portion 2c will not become a special obstacle, and the second protruding resin portion 2c (see FIG. 4) will be at a height that can catch on the chamfer 11b on the left side of the track wheel 11, making it possible to improve the fitting property when attaching the shaft insulating cover 1 to the track wheel 11. On the other hand, in the use state where the second cylindrical resin surface 3 of the track wheel 11 with the shaft insulating cover 1 (see FIGS. 5 and 6) is loosely fitted into the bearing seat Hi of the corresponding mechanical element, although the radial displacement of the second cylindrical resin surface 3 is restricted by the bearing seat Hi, there is a possibility that the first cylindrical resin surface 2 may be displaced radially due to thermal expansion or the like with respect to the fitting surface 11a of the track wheel 11. The radial height of the second protruding resin portion 2c is provided to be larger than the fitting clearance between the track wheel 11 with the shaft insulating cover 1 and the bearing seat Hi of the corresponding mechanical element in order to ensure the anti-loosening property due to the catching of the second protruding resin portion 2c on the chamfer on the left side of the track wheel 11. Note that the second protruding resin portion 2c only needs to be at at least one place in the circumferential direction as long as it can ensure the axial facing arrangement between the second protruding resin portion 2c and the left side surface of the track wheel 11 in the use state of the rolling bearing 10.

[0055] When fitting the first cylindrical resin surface 2 of the shaft insulating cover 1 onto the fitting surface 11a of the track wheel 11, each second protruding resin portion 2c first contacts the chamfer on the right side of the track wheel 11. The cylindrical resin portion having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is elastically deformed by the radial component of the vertical resistance force from the track wheel 11 generated at each contact portion. As a result, each second protruding resin portion 2c is allowed to reach the fitting surface 11a. When each second protruding resin portion 2c passes over the fitting surface 11a of the track wheel 11 and reaches the left chamfer 11b, the cylindrical resin portion having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 elastically returns. Each convex 2a of the first cylindrical resin surface 2 (however, it is the central portion in the circumferential direction other than the second protruding resin portion 2c and is located between the first protruding resin portion 4 and the second protruding resin portion 2c) and the fitting surface 11a of the track wheel 11 are in a superimposed fitting state. At this time, each second protruding resin portion 2c is in a position where it can be axially hooked on the left chamfer 11b of the track wheel 11 as shown in FIG. 4, and the first protruding resin portion 4 (see FIG. 5) is in a position where it can be axially hooked on the right side surface (particularly the width surface 11c) of the track wheel 11. Thereby, the attachment of the shaft insulating cover 1 to the track wheel 11 is completed.

[0056] In addition, in order to make the above-mentioned fitting property better, it is preferable to form an insertion guide surface that becomes lower in the radial direction from the top of each second protruding resin portion 2c (see FIGS. 1 and 2) toward the left. In the illustrated example, by making each second protruding resin portion 2c hemispherical, the above-mentioned insertion guide surface is formed.

[0057] Even if the tightening allowance between the first cylindrical resin surface 2 of the shaft insulating cover 1 and the fitting surface 11a of the track wheel 11 is tightly formed, when the first cylindrical resin surface 2 is fitted into the fitting surface 11a of the track wheel 11, the cylindrical resin portion having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is particularly likely to elastically expand and contract in the circumferential direction at the plurality of recesses 2b, 3b. For this reason, the cylindrical resin portion is likely to elastically deform in the radial direction until the fitting surface 11a of the track wheel 11 and the first cylindrical resin surface 2 have the same diameter as a whole. As a result, adverse effects such as a decrease in the bearing internal clearance and a decrease in the roundness of the raceway on the rolling bearing 10 are less likely to occur.

[0058] On one hand, the clearance between the second cylindrical resin surface 3 of the track wheel 11 with the shaft-bearing insulating cover 1 and the bearing seat Hi of the corresponding mechanical element varies depending on the dimensional accuracy in the radial direction of the first cylindrical resin surface 2 and the second cylindrical resin surface 3 that face the fitting surface 11a of the track wheel 11 in the radial direction. If the dimensional accuracy in the radial direction of the second cylindrical resin surface 3 is loosened, the above-mentioned clearance may become smaller, and there is a concern that the fitting surface pressure between the three components, namely, the shaft-bearing insulating cover 1, the fitting surface 11a of the track wheel 11, and the bearing seat Hi, will increase, which may have an adverse effect on the rolling bearing 10, such as a decrease in the internal clearance of the bearing. In particular, the coefficient of linear expansion of the shaft-bearing insulating cover 1 made of resin is generally several times larger than that of the track wheel 11 and the bearing seat Hi made of metal such as steel. Therefore, compared with the change in the radial dimensions of the fitting surface 11a of the track wheel 11 and the bearing seat Hi due to the temperature change during the use of the rolling bearing 10, the change in the radial dimensions of the first cylindrical resin surface 2 and the second cylindrical resin surface 3 due to the temperature change is larger. If the resulting clearance is small, with the temperature change during use, the protrusions 2a, 3a of the shaft-bearing insulating cover 1 will press the fitting surface 11a of the track wheel 11 and the bearing seat Hi in the radial direction, and the fitting surface pressure between the protrusion 2a and the fitting surface 11a, and the fitting surface pressure between the protrusion 3a and the bearing seat Hi may increase. When these fitting surface pressures tend to increase, since the recesses 2b, 3b form a space on both circumferential sides of the protrusions 2a, 3a, the resin part forming the protrusions 2a, 3a can escape into the space. That is, the protrusions 2a, 3a are radially pressed between the fitting surface 11a of the track wheel 11 and the bearing seat Hi and are flattened and spread toward the recesses 2b, 3b. As a result, the fitting surface pressure between the protrusions 2a, 3a of the shaft-bearing insulating cover 1, the fitting surface 11a of the track wheel 11, and the bearing seat Hi of the corresponding mechanical element is reduced, so that the rolling bearing 10 is less likely to be affected as described above.

[0059] In this way, by ensuring the prevention of the shaft insulating cover 1 from coming off the track wheel 11 with the first protruding resin portion 4 and the second protruding resin portion 2c, it is possible to prevent the shaft insulating cover 1 from coming out of the track wheel 11 without tightly setting the tightening margin between the fitting surface of the track wheel and the first cylindrical resin surface. Also, by improving the circumferential stretchability at each recess 2b, 3b, good fitability of the first cylindrical resin surface 2 to the fitting surface 11a of the track wheel 11 can be ensured. Moreover, since the fitting pressure between the fitting surface 11a and the bearing seat Hi can be reduced due to the ease of crushing of each protrusion 2a, 3a, it is possible to relax the dimensional accuracy of the diameter of the virtual circle in contact with the first cylindrical resin surface 2 (the difference in the radial height of the protrusion 2a) and the diameter of the virtual circle in contact with the second cylindrical resin surface 3 (the difference in the radial height of the protrusion 3a) to such an extent that it can be ensured by injection molding. At the same time, it is possible to stably maintain the insulation during the use of the rolling bearing 10 and prevent the above-mentioned adverse effects on the rolling bearing 10.

[0060] Note that in order to suppress the circumferential expansion / contraction amount at each recess 2b, 3b and make each protrusion 2a, 3a more easily crushable in the radial direction, it is preferable to increase the total number of unevenness (2b, 2a, 3b, 3a) in the circumferential direction. In the illustrated example, the unevenness (2b, 2a) of the first cylindrical resin surface 2 and the unevenness (3b, 3a) of the second cylindrical resin surface 3 are equally distributed at 60 locations in the circumferential direction, respectively.

[0061] The shaft insulating cover 1 (see FIGS. 3 to 6) is as described above, and has a first cylindrical resin surface 2 formed on one side inside and outside of the cylindrical resin part so as to be fitted into the fitting surface 11a of the track wheel 11, a second cylindrical resin surface 3 formed on the other side inside and outside of the cylindrical resin part, and a first protruding resin part 4 that axially catches on the side surface on one axial side (the right side in FIG. 5) of the track wheel 11 when the first cylindrical resin surface 2 is fitted into the fitting surface 11a of the track wheel 11. The first cylindrical resin surface 2, the second cylindrical resin surface 3, and the first protruding resin part 4 are integrally formed, and the first cylindrical resin surface 2 includes a second protruding resin part 2c that axially catches on the side surface on the side opposite to the one axial side (the left side in FIGS. 4 and 5) of the track wheel 11 in the fitting state. Both of the cylindrical resin surfaces 2 and 3 of the first cylindrical resin surface 2 and the second cylindrical resin surface 3 are formed with irregularities (2b, 2a, 3b, 3a).

[0062] When the shaft insulating cover 1 fits the first cylindrical resin surface 2 into the fitting surface 11a of the track wheel 11 and is in a fitting state where the first protruding resin part 4 and the second protruding resin part 2c axially catch on the side surfaces on both sides of the track wheel 11, the shaft insulating cover 1 can be attached to the track wheel 11. When the track wheel 11 with the shaft insulating cover 1 is fitted into the bearing seat Hi of the corresponding mechanical element, the cylindrical resin part having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is sandwiched between the bearing seat Hi and the fitting surface 11a of the track wheel 11. Therefore, insulation can be achieved between these two, Hi and 11a. Thus, insulation of the rolling bearing 10 can be achieved without performing insert molding of insulating resin on the track wheel 11.

[0063] Also, the shaft insulating cover 1 prevents the shaft insulating cover 1 from coming off the track wheel 11 by using the first protruding resin part 4 and the second protruding resin part 2c to prevent the shaft insulating cover 1 from coming out of the track wheel 11 without tightly setting the tightening allowance between the fitting surface 11a of the track wheel 11 and the first cylindrical resin surface 2.

[0064] Further, in the shaft insulating cover 1, since at least one of the first cylindrical resin surface 2 and the second cylindrical resin surface 3 of the shaft insulating cover 1 is formed with unevenness (2b, 2a, 3b, 3a), even if the tightening margin between the fitting surface 11a of the race ring 11 and the first cylindrical resin surface 2 becomes large, due to the improved circumferential stretchability at the recesses 2b, 3b, it is possible to fit the first cylindrical resin surface 2 into the fitting surface 11a of the race ring 11. Also, when the mating surface pressure among the shaft insulating cover 1, the fitting surface 11a of the race ring 11, and the bearing seat Hi of the corresponding mechanical element becomes high, the protrusions 2a, 3a are radially pressed between the fitting surface 11a of the race ring 11 and the bearing seat Hi of the corresponding mechanical element and are flattened downward so as to expand toward the recesses 2b, 3b, thereby reducing each mating surface pressure.

[0065] Therefore, by adopting the first protruding resin portion 4, the second protruding resin portion 2c, and at least one of the unevenness (2b, 2a, 3b, 3a), the shaft insulating cover 1 can relax the dimensional accuracy in the radial direction of the first cylindrical resin surface 2 and the second cylindrical resin surface 3, while stably maintaining the insulation during the use of the rolling bearing 10 and preventing adverse effects on the rolling bearing 10.

[0066] Also, the shaft insulating cover 1 can achieve good detachability of the shaft insulating cover 1 with respect to the race ring 11 based on a slight press - fitting with respect to the fitting surface 11a of the race ring 11, a retaining property using the minute second protruding resin portion 2c capable of overcoming the fitting surface 11a of the race ring 11, and the improved circumferential stretchability due to the formation of the recesses (2b, 3b). As a result, it is also possible to separately discard or reuse the race ring 11 and the shaft insulating cover 1, thereby reducing the environmental load.

[0067] In addition, the shaft insulating cover 1 is provided such that the first protruding resin portion 4 is overlapped with the width surface 11c on one axial side (right side) of the track wheel 11. When fitting the track wheel 11 with the shaft insulating cover 1 into the corresponding mechanical element, the first protruding resin portion 4 is sandwiched between the width surface 11c on one axial side (right side) of the track wheel 11 and the shoulder Hs of the corresponding mechanical element, and insulation can be achieved between these two, 11c and Hs. Also, the concern that the shaft insulating cover 1 separates axially from the track wheel 11 during the use of the rolling bearing 10 can be eliminated.

[0068] In addition, the shaft insulating cover 1 is provided such that the radial height of the second protruding resin portion 2c is 0.3 mm or less, improving the fit of the first cylindrical resin surface 2 to the fitting surface 11a of the track wheel 11. Also, even in the state of use of the rolling bearing 10 where the second cylindrical resin surface 3 and the bearing seat Hi of the corresponding mechanical element are in an interference fit, a state where the track wheel 11 and the second protruding resin portion 2c face each other axially is ensured, maintaining the anti - detachment property of the shaft insulating cover 1 by the second protruding resin portion 2c. Thus, insulation of the rolling bearing 10 can be achieved stably.

[0069] In addition, the shaft insulating cover 1 has unevenness (2b, 2a, 3b, 3a) on the first cylindrical resin surface 2 and the second cylindrical resin surface 3 respectively. Since the recesses (2b, 3b) of the unevenness on the first cylindrical resin surface 2 and the second cylindrical resin surface 3 face each other in the radial direction, the opposing part of the recesses (2b, 3b) is particularly thin and easily expands and contracts in the circumferential direction. Therefore, compared with the case where only one of the first cylindrical resin surface and the second cylindrical resin surface has unevenness, the fit of the first cylindrical resin surface 2 to the fitting surface 11a of the track wheel 11 can be improved.

[0070] In addition, the shaft insulating cover 1 has the unevenness (2b, 2a, 3b, 3a) of the cylindrical resin surfaces 2 and 3 equally distributed at a plurality of positions in the circumferential direction, enabling the cylindrical resin portion having the first cylindrical resin surface 2 and the second cylindrical resin surface 3 to expand and contract evenly in the circumferential direction, and preventing the tightening allowance from becoming particularly small in a partial region in the circumferential direction when fitting to the fitting surface 11a of the track wheel 11.

[0071] In addition, the rolling bearing 10 including a raceway ring 11 into which the shaft insulating cover 1 is fitted, another raceway ring 12 facing the raceway ring 11, and a plurality of rolling elements 13 disposed between the raceway ring 11 and the other raceway ring 12 can prevent electric erosion inside the bearing even when a voltage of 100 V is applied between the shaft S and the bearing seat Hi and shoulder Hs of the housing.

[0072] In the shaft insulating cover 1, an example in which the unevenness (2b, 2a, 3b, 3a) extends in the axial direction is shown. However, it is only necessary that the unevenness extends so as to form concave spaces on both circumferential sides of the convex portion over the entire width of the cylindrical resin surface, and it is also possible to extend the unevenness in a direction inclined with respect to the axial direction. For example, when a draft angle for improving the mold release property during injection molding is provided, the unevenness extends in a direction slightly inclined with respect to the axial direction.

[0073] In the shaft insulating cover 1, an example in which the unevenness (2b, 2a, 3b, 3a) is equally arranged in the circumferential direction is shown. However, it is not necessary to arrange them equally in the circumferential direction, and they may be provided in an uneven shape. The key is to appropriately determine the shape of the unevenness, the circumferential arrangement, the radial height of the convex portion with respect to the concave bottom, etc. so that the fitting property with respect to the fitting surface of the raceway ring and the reduction of the fitting surface pressure among the three corresponding mechanical elements of the shaft insulating cover and the raceway ring can be realized with the dimensional accuracy in the radial direction obtained by injection molding.

[0074] In addition, an example in which the shaft insulating cover 1 is fitted into the fitting surface 11a of the raceway ring 11 which is the outer ring is shown. However, it is also possible to change it to a shaft insulating cover fitted into the fitting surface of the other raceway ring 12 which is the inner ring. In this case of change, it is only necessary to arrange the first protruding resin portion and the second protruding resin portion on the outer periphery of the cylindrical resin portion of the shaft insulating cover, and thus the illustration and detailed description are omitted.

[0075] Also, in the shaft-bearing insulating cover 1, the first protruding resin portion 4 in the shape of a flange that entirely covers the right-width surface 11c of the track wheel 11 has been exemplified. However, when a sufficient space distance for insulation can be ensured on both sides of the track wheel 11, it is not necessary to form the first protruding resin portion in the shape of a flange. A second embodiment as an example thereof is shown in FIG. 7. In the following, only the differences from the first embodiment will be described, and the same reference numerals will continue to be used for the components corresponding to those in the first embodiment.

[0076] The shaft-bearing insulating cover according to the second embodiment is symmetric with respect to a virtual radial plane that bisects its entire width. Accordingly, the first protruding resin portion 4 is provided symmetrically with respect to the second protruding resin portion 2c in terms of surface. The first protruding resin portion 4 will catch axially on the chamfer on the right side of the track wheel 11 shown in FIG. 5. The shaft-bearing insulating cover that is symmetric in terms of surface as in the second embodiment can be fitted from either the left or right side with respect to the track wheel. Also, among the shaft-bearing insulating covers shown in FIG. 7, the right peripheral edge portion that protrudes more to the right than the first protruding resin portion 4 abuts axially against the shoulder Hs of the corresponding mechanical element shown in FIG. 5, contributing to ensuring a sufficient space distance for insulation between the right-width surface 11c of the track wheel 11 and the shoulder Hs.

[0077] In the first embodiment and the second embodiment, unevenness is provided on both the first cylindrical resin surface and the second cylindrical resin surface of the shaft-bearing insulating cover, but it is also possible to provide unevenness on only one of them. A third embodiment as an example thereof is shown in FIGS. 8 and 9.

[0078] The shaft-bearing insulating cover according to the third embodiment is such that the first cylindrical resin surface 2 has unevenness (2b, 2a), while the second cylindrical resin surface 3 is formed in a cylindrical surface shape. Therefore, the minimum thickness between the recess 2b of the first cylindrical resin surface 2 and the second cylindrical resin surface 3 is greater than that in the first embodiment.

[0079] The shaft-bearing insulating cover according to a fourth embodiment as another example is shown in FIG. 10. The shaft-bearing insulating cover according to the fourth embodiment employs the first protruding resin portion 4 according to the second embodiment in the third embodiment.

[0080] The shaft insulating cover according to the fifth embodiment as yet another alternative example is shown in FIGS. 11 and 12. The shaft insulating cover according to the fifth embodiment has unevenness (3b, 3a) only on the second cylindrical resin surface 3. On the first cylindrical resin surface 2, a fitting surface 2d along the circumferential direction is formed instead of the unevenness of the first embodiment. The diameter of the fitting surface 2d corresponds to the diameter of the virtual circle that contacts the convex portion of the first cylindrical resin surface in the first embodiment. The first protruding resin portion 4 and the second protruding resin portion 2c are the same as those in the second embodiment.

[0081] In the above-described first to fifth embodiments, an example is shown in which a resin portion continuous over the entire circumference in the circumferential direction is secured with the thickness of the concave bottom between the first cylindrical resin surface 2 and the second cylindrical resin surface 3 of the shaft insulating cover, and the thickness is increased at the convex portion with respect to the concave portion. However, it is also possible to provide unevenness while making the thickness of the resin portion constant throughout the entire area between the first cylindrical resin surface and the second cylindrical resin surface. A sixth embodiment as an example thereof is shown in FIGS. 13 and 14.

[0082] In the shaft insulating cover according to the sixth embodiment, the convex portion 2a of the first cylindrical resin surface 2 and the concave portion 3b of the second cylindrical resin surface 3 face each other in the radial direction, and the concave portion 2b of the first cylindrical resin surface 2 faces the convex portion 3a of the second cylindrical resin surface 3 in the radial direction. The wave shape exhibited by the unevenness (2b, 2a) of the first cylindrical resin surface 2 is along the wave shape exhibited by the unevenness (3b, 2a) of the second cylindrical resin surface 3.

[0083] It should be considered that all the embodiments disclosed this time are illustrative and not restrictive in any way. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0084] 1 Shaft insulating cover 2 First cylindrical resin surface 2a Convex 2b Concave 2c Second protruding resin portion 3 Second cylindrical resin surface 3a convex 3b concave 4 First protruding resin part 10 Rolling bearing 11 Raceway ring 11a Fitting surface 11b Chamfer 11c Width surface 12 Other raceway ring 13 Rolling element

Claims

1. a first cylindrical resin surface formed on one of the inner and outer sides of the cylindrical resin part so as to be fitted into the fitting surface of the track wheel; a second cylindrical resin surface formed on the other of the inner and outer sides of the cylindrical resin part; a first protruding resin part that is axially hooked on a side surface on one axial side of the track wheel when the first cylindrical resin surface is fitted into the fitting surface of the track wheel; and the first cylindrical resin surface, the second cylindrical resin surface, and the first protruding resin part are integrally formed; the first cylindrical resin surface includes a second protruding resin part that is axially hooked on a side surface opposite to the one axial side of the track wheel in the fitted state; a shaft insulating cover in which one or both of the first cylindrical resin surface and the second cylindrical resin surface are formed with unevenness.

2. The shaft insulating cover according to claim 1, wherein the first protruding resin part is provided so as to overlap a width surface on one axial side of the track wheel.

3. The shaft insulating cover according to claim 1, wherein a radial height of the second protruding resin part is provided to be 0.3 mm or less.

4. The shaft insulating cover according to claim 1, wherein the first cylindrical resin surface and the second cylindrical resin surface each have the unevenness, and the recesses of the unevenness of the first cylindrical resin surface and the recesses of the unevenness of the second cylindrical resin surface face each other in the radial direction.

5. The shaft insulating cover according to claim 1, wherein the unevenness of one or both of the cylindrical resin surfaces is equally distributed at a plurality of positions in the circumferential direction.

6. A rolling bearing comprising: the track wheel into which the shaft insulating cover according to any one of claims 1 to 5 is fitted; another track wheel that faces the track wheel in the radial direction; and a plurality of rolling elements disposed between the track wheel and the other track wheel.

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