Radial bearing

Abstract

To provide a radial bearing that can has 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 bearing having 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, the radial bearing 100 includes 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. Each of the inner ring slinger 150, the outer ring slinger 160 and the sub rolling element 180 has electric conductivity. The hardness of the sub rolling element 180 is lower than that of the main rolling element 130.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 the bearing, electric 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. Therefore, countermeasures against electric erosion are desired in automobiles.

[0003] Countermeasures against electric erosion are to ground the electric charge (stray current) caused by high-voltage components to the surrounding case. As an example of electric 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 applying an electric resistance at a position downstream of the motor shaft, and a ground connection body electrically connecting between a position downstream of the resistor on the power transmission path and the vehicle body".

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] 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 a main rolling element 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 a secondary rolling element that rolls in axial contact between the inner ring slinger and the outer ring slinger, wherein the inner ring slinger, the outer ring slinger, and the secondary rolling element are conductive, and the hardness of the secondary rolling element is lower than the hardness of the main rolling element.

[0008] The main and secondary rolling elements described above are made of steel, and it is preferable that the main rolling elements are heat-treated, while the secondary rolling elements are not. [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 the Rockwell hardness and dielectric breakdown voltage of electrode materials. [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 this invention, the hardness of the auxiliary rolling element 180, which is made of metal, is set lower than that of the main rolling element 130, thereby setting the impedance of the path passing through the auxiliary rolling element 180 lower than the impedance of the path passing through the main rolling element 130.

[0017] Figure 2 illustrates the relationship between the Rockwell hardness of electrode materials and dielectric breakdown voltage, with Rockwell hardness used as the hardness in Figure 2 (Source: Hideo Watanabe, et al.: "Recent Trends in Vacuum Circuit Breakers," Journal of the Institute of Electrical Engineers of Japan, Vol. 102, No. 6, pp. 465-472 (1982)). Figure 2 plots the dielectric breakdown voltage for each Rockwell hardness when Bi, Al, Cu, SUS alloy, Mo, and Cu-W alloy are used as electrode materials, and an example of the linear curve S of the approximation function is shown. From the graph in Figure 2, it can be seen that even if the insulator remains the same, the dielectric breakdown voltage increases as the hardness of the electrode material increases.

[0018] In the radial bearing 100 of this embodiment, the insulator is an oil film formed on the surfaces of the main rolling elements 130 and the secondary rolling elements 180. The dielectric breakdown voltage is the voltage at which the insulator (oil film) electrically breaks down, loses its insulating properties, and begins to conduct electricity.

[0019] In the radial bearing 100 of this embodiment, the electrical paths are a path through the main rolling element 130 and a path through the auxiliary rolling element 180. Electricity will flow through the path that experiences dielectric breakdown earlier. Therefore, in the radial bearing 100 of this embodiment, the hardness of the auxiliary rolling element 180 is set lower than that of the main rolling element 130. Consequently, the path through the auxiliary rolling element 180 experiences dielectric breakdown earlier, and electricity mainly flows through the auxiliary rolling element 180, the inner ring slinger 150, and the outer ring slinger 160. Therefore, current flow through the main rolling element 130, the inner ring 110, and the outer ring 120 can be prevented.

[0020] One method to achieve the effects described above is to use steel for the main rolling element 130 and the secondary rolling element 180, and to apply a heat treatment to the main rolling element 130 while not applying a heat treatment to the secondary rolling element 180. This makes it possible to increase the hardness of the main rolling element 130 and decrease the hardness of the secondary rolling element 180.

[0021] However, such a configuration is merely an example and does not exclude the use of other materials or the presence or absence of quenching treatment. In the radial bearing 100, the secondary rolling elements 180 having the structure of an axial bearing are basically not subjected to external loads. Therefore, the secondary rolling elements 180 do not require high rigidity and various materials can be used. Specifically, copper or aluminum can be used for the secondary rolling elements 180. Since copper and aluminum are confirmed in the graph of FIG. 2, it is certain that the breakdown voltage will be low. Furthermore, since any conductive material having a lower hardness than quenched steel should exhibit behavior in accordance with the present invention, soft iron, brass, or other alloys may be used.

[0022] Also, since an electric current flows through the secondary rolling elements 180, it is conceivable that electric erosion will occur in the secondary rolling elements 180, the inner ring slinger 150, and the outer ring slinger 160. However, since no external load is applied to the secondary rolling elements 180, it does not affect the rotational performance of the radial bearing 100. In other words, by causing electric erosion in the secondary rolling elements 180 that do not affect the function of the radial bearing 100, electric erosion of the main rolling elements 130 is avoided. And since conduction is achieved by rolling elements (secondary rolling elements 180) instead of brushes, it is possible to cope with high-speed rotation.

[0023] 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 they also belong to the technical scope of the present invention.

Industrial Applicability

[0024] 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 Reference Numerals

[0025] 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

[Claim 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 main rolling element and the auxiliary rolling element are made of steel. The hardness of the auxiliary rolling element is lower than the hardness of the main rolling element. A radial bearing characterized in that the main rolling elements are heat-treated, and the secondary rolling elements are not heat-treated.

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