Radial bearing

Abstract

To provide a radial bearing that can have high electric erosion resistance over a long period and is adaptable to high speed rotation.SOLUTION: A radial bearing 100 in this invention is a radial bearing which has an inner ring 110, an outer ring 120, and a main rolling element 130 arranged between the inner ring 110 and the outer ring 120 and comprises: an annular inner ring slinger 150 fixed to the inner ring 110; an annular outer ring slinger 160 fixed to the outer ring 120; and a sub rolling element 180 arranged between the inner ring slinger 150 and the outer ring slinger 160 and coming in axial contact with the slingers 150 and 160 thereby rolling, wherein each of the inner ring slinger 150, the outer ring slinger 160, and the sub rolling elements 180 has electric conductivity, and an oil film parameter between the sub rolling element 180 and the inner ring slinger 150 and an oil film parameter between the sub rolling element 180 and the outer ring slinger 160, are smaller than an oil film parameter between: the main rolling element 130; and the inner ring 110 and the outer ring 120.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a radial bearing having an inner ring, an outer ring, and main rolling elements disposed between the outer ring and the inner ring.

Background Art

[0002] In recent years, with the development of electric cars (EVs) and hybrid cars (HVs), the number of high-voltage components installed in a single automobile has been increasing. When the current of these high-voltage components is applied to a bearing, electrical erosion occurs on the surface of the rolling elements of the bearing, the raceway surfaces of the outer and inner rings, which contributes to damage.

[0003] Measures against electrical erosion are to ground the electric charge (stray current) caused by high-voltage components to the surrounding case. As an example of electrical erosion, Patent Document 1 discloses an electric vehicle power transmission device including "a motor, an inverter as a high-frequency controller connected to the motor coil and changing the direction of current by a switching element, a resistor provided on the power transmission path from the motor shaft to the drive wheels and providing electrical resistance at a position downstream of the motor shaft, and an earth connection body electrically connecting between the downstream position on the power transmission path from the resistor and the vehicle body."

Prior Art Documents

[0004] [[ID=30—31]] [[ID=32—36]] [[ID=37—38]] [[ID=39—41]] [[ID=42—44]] [[ID=45—47]] [[ID=48—50]] [[ID=51—53]] [[ID=54—56]]

[0005] [[ID=57—59]] ​​​​​By incorporating an earthing connector as described in Patent Document 1, electrolytic corrosion can be reduced. However, when a sliding brush is used as the earthing connector as in Patent Document 1, the sliding brush wears down during bearing operation. As a result, the electrolytic corrosion resistance deteriorates with prolonged use. Wear becomes particularly pronounced when the bearing is rotated at high speeds, which further shortens the bearing's lifespan. Therefore, there is room for further improvement in the technology of Patent Document 1.

[0006] In view of these problems, the present invention aims to provide a radial bearing that can achieve high resistance to electrolytic corrosion over a long period of time and can handle high-speed rotation. [Means for solving the problem]

[0007] To solve the above problems, a typical configuration of the radial bearing according to the present invention is a radial bearing having an inner ring, an outer ring, and main rolling elements disposed between the inner ring and the outer ring, comprising an annular inner ring slinger fixed to the inner ring, an annular outer ring slinger fixed to the outer ring, and secondary rolling elements that roll in axial contact between the inner ring slinger and the outer ring slinger, wherein the inner ring slinger, outer ring slinger, and secondary rolling elements are conductive, and the oil film parameter between the secondary rolling elements and the inner ring slinger and outer ring slinger is smaller than the oil film parameter between the main rolling elements and the inner ring and outer ring.

[0008] The secondary rolling element should have a rougher surface than the primary rolling element. Furthermore, the raceway surface of the slinger should have a rougher surface than the raceway surface of the inner or outer ring. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a radial bearing that can achieve high resistance to electrolytic corrosion over a long period of time and can also handle high-speed rotation. [Brief explanation of the drawing]

[0010] [Figure 1]This is a diagram illustrating the radial bearing according to this embodiment. [Figure 2] This diagram illustrates the relationship between oil film parameters and dielectric strength. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely illustrative to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are not shown or described.

[0012] Figure 1 is a diagram illustrating a radial bearing 100 according to this embodiment. As illustrated in Figure 1, the radial bearing of this embodiment comprises an inner ring 110, an outer ring 120, main rolling elements 130, and a cage 140. The main rolling elements 130 are held by the cage 140 and are positioned between the inner ring 110 and the outer ring 120, and roll between them.

[0013] In this embodiment 100, an annular inner ring slinger 150 is fixed to the inner ring 110, and an annular outer ring slinger 160 is fixed to the outer ring 120. The inner ring slinger 150 and the outer ring slinger 160 are not in contact. The inner ring slinger 150 has a raceway surface 152, which is a circular groove, and the outer ring slinger 160 has a raceway surface 162, which is a circular groove, that faces the inner ring slinger 150. The auxiliary rolling elements 180 are arranged in the gap formed by these opposing raceway surfaces 152 and 162. The auxiliary rolling elements are held by a cage 170 to maintain a constant distance from each other.

[0014] The auxiliary rolling element 180 is in axial contact with the inner ring slinger 150 and the outer ring slinger 160, and conducts current while rolling between them. The auxiliary rolling element 180 may be in contact with the inner ring slinger 150 and the outer ring slinger 160 by being sandwiched between them, or it may be in contact with both the inner ring slinger 150 and the outer ring slinger 160 due to its own weight or centrifugal force during bearing rotation. What is important here is that in the radial bearing 100, since the auxiliary rolling element 180 is in axial contact, in principle the auxiliary rolling element 180 does not receive the main load (external force) applied to the radial bearing 100. Furthermore, even if an axial load is applied, the inner ring slinger 150 and outer ring slinger 160 are annular members made of thin plates, so they will bend and therefore cannot withstand the axial load with the auxiliary rolling element 180.

[0015] The main rolling elements 130 and secondary rolling elements 180 described above are both made of metallic material and are electrically conductive. The radial external force applied to the radial bearing 100 is borne by the inner ring 110, outer ring 120, and main rolling elements 130. On the other hand, the impedance of the path passing through the secondary rolling elements 180 is set lower than the impedance of the path passing through the main rolling elements 130. This allows charges (stray currents) originating from high-voltage components to be grounded to surrounding components by energizing the inner ring slinger 150, outer ring slinger 160, and secondary rolling elements 180. Therefore, it is possible to effectively suppress electrolytic corrosion caused by energization in the inner ring 110, outer ring 120, and main rolling elements 130, and to obtain high electrolytic corrosion resistance.

[0016] In particular, in the radial bearing 100 of the present embodiment, the oil film parameters between the auxiliary rolling elements 180, the inner ring slinger 150, and the outer ring slinger 160 are set to be smaller than the oil film parameters between the main rolling elements 130, the outer ring 120, and the inner ring 110. Thereby, in the radial bearing 100, the impedance of the path through the auxiliary rolling elements 180 is set lower than the impedance of the path through the main rolling elements 130. The oil film parameter Λ can be obtained by the formula "oil film parameter Λ = minimum oil film thickness / √(raceway surface roughness^2 + rolling surface roughness^2)".

[0017] FIG. 2 is a diagram illustrating the relationship between the oil film parameter and the breakdown voltage. As illustrated by the approximate straight line S in FIG. 2, the breakdown voltage increases as the oil film parameter Λ (lambda) of the oil film formed between a plurality of members increases. Then, the charge passes through the path with a small oil film parameter Λ.

[0018] Therefore, the oil film parameter (for example, A) between the auxiliary rolling elements 180, the inner ring slinger 150, and the outer ring slinger is set to be smaller than the oil film parameter (for example, B) between the main rolling elements 130, the inner ring 110, and the outer ring 120 (however, A < B). Then, the breakdown voltage in the auxiliary rolling elements 180, the inner ring slinger 150, and the outer ring slinger becomes C, and the breakdown voltage in the main rolling elements 130, the inner ring 110, and the outer ring 120 becomes D (however, C < D). Thereby, the charge mainly flows through the "auxiliary rolling elements 180, the inner ring slinger 150, and the outer ring slinger 160". Therefore, energization of the main rolling elements 130, the inner ring, and the outer ring can be prevented.

[0019] As a method for obtaining the above-described effects, it is preferable to set the surface roughness of the auxiliary rolling element 180 to be larger than that of the main rolling element 130. As another method, it is preferable to set the surface roughness of the raceway surfaces 152 and 162 of the inner ring slinger 150 and the outer ring slinger 160 to be larger than that of the raceway surfaces 112 and 122 of the inner ring 110 and the outer ring 120. By these means, since the denominator on the right side of the above-described formula becomes larger, the oil film parameters between the auxiliary rolling element 180, the inner ring slinger 150, and the outer ring slinger 160 can be set to be small.

[0020] In addition, since an electric current flows through the auxiliary rolling element 180, it is conceivable that electric corrosion may occur in the auxiliary rolling element 180, the inner ring slinger 150, and the outer ring slinger 160. However, since no external load is applied to the auxiliary rolling element 180, it does not affect the rotational performance of the radial bearing 100. In other words, by causing electric corrosion to occur in the auxiliary rolling element 180 that does not affect the function of the radial bearing 100, electric corrosion of the main rolling element 130 is avoided. And since conduction is achieved by the rolling element (auxiliary rolling element 180) instead of the brush, it is possible to cope with high-speed rotation.

[0021] As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. Needless to say, the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Industrial Applicability

[0022] The present invention can be used as a radial bearing having an inner ring, an outer ring, and main rolling elements disposed between the outer ring and the inner ring.

Explanation of Signs

[0023] 100...Radial bearing, 110...Inner ring, 112...Raceway surface, 120...Outer ring, 122...Raceway surface, 130...Main rolling element, 140...Cage, 150...Inner ring slinger, 152...Raceway surface, 160...Outer ring slinger, 162...Raceway surface, 170...Cage, 180...Secondary rolling element

Claims

1. A radial bearing having an inner ring, an outer ring, and a main rolling element disposed between the inner ring and the outer ring, An annular inner ring slinger fixed to the inner ring, An annular outer ring slinger fixed to the outer ring, The inner ring slinger and the outer ring slinger are provided with a secondary rolling element that rolls in contact with each other in the axial direction. The inner ring slinger, the outer ring slinger, and the auxiliary rolling element are electrically conductive. The oil film parameter between the auxiliary rolling element and the inner ring slinger and the outer ring slinger is smaller than the oil film parameter between the main rolling element and the inner ring and the outer ring. A radial bearing characterized in that the secondary rolling element has a greater surface roughness than the primary rolling element.

2. A radial bearing having an inner ring, an outer ring, and a main rolling element disposed between the inner ring and the outer ring, An annular inner ring slinger fixed to the inner ring, An annular outer ring slinger fixed to the outer ring, The inner ring slinger and the outer ring slinger are provided with a secondary rolling element that rolls in contact with each other in the axial direction. The inner ring slinger, the outer ring slinger, and the auxiliary rolling element are electrically conductive. The oil film parameter between the auxiliary rolling element and the inner ring slinger and the outer ring slinger is smaller than the oil film parameter between the main rolling element and the inner ring and the outer ring. A radial bearing characterized in that the raceway surface of the inner ring slinger has a rougher surface than the raceway surface of the inner ring, or the raceway surface of the outer ring slinger has a rougher surface than the raceway surface of the outer ring.

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