WO2023026978A1

WO2023026978A1 - Bearing device

Info

Publication number: WO2023026978A1
Application number: PCT/JP2022/031367
Authority: WO
Inventors: 隼人川口
Original assignee: Ntn株式会社
Priority date: 2021-08-24
Filing date: 2022-08-19
Publication date: 2023-03-02
Also published as: JP2023030949A; KR20240050370A; CN117836527A

Abstract

This bearing device uses rolling bearings to support a vehicle drive motor, or a rotation shaft included in the transmission connected to the vehicle drive motor, with respect to a housing. The bearing device suppresses bearing ring costs while avoiding reduction in insulation film reliability or the mass producibility of bearing rings of the rolling bearings. To this end, the rolling bearing (1) has a bearing ring (3) which is attached to a rotation shaft (21) or a housing (10), a fitting surface (3b) of one bearing ring (3) that fits with the one member (10) is formed from an insulation film (7), and the fitting surface (3b) and the housing (10) have a clearance fit.

Description

bearing device

The present invention relates to a bearing device having a rolling bearing between a rotating shaft and a housing included in a motor for driving a vehicle or the like, and more particularly to insulating the bearing ring of the rolling bearing.

In general, automobiles such as electric vehicles (EV) and electric hybrid vehicles (HV) and vehicles for industrial machinery are equipped with a drive system including a drive motor and a transmission. A rotating shaft of the drive motor or transmission is supported by a rolling bearing.

When incorporating a rolling bearing into a drive motor or a transmission connected thereto, a potential difference may occur between the housing and the rotating shaft interposed by the rolling bearing. A drive motor needs to have a high frequency for inverter control in order to achieve high efficiency, but the higher the frequency, the more likely the current will flow through the rolling bearings.

If the fitting surface of the bearing ring attached to one of the rotating shaft and the housing is conductive, the electric current due to the potential difference described above will flow through the rolling bearing and discharge will occur in the elastic contact area between the raceway surface and the rolling elements. Electrolytic corrosion may occur on the rolling elements. In order to prevent this, conventionally, the fitting surface of the bearing ring is formed with an insulating coating (Patent Document 1).

　Increasing the impedance of rolling bearings is effective in preventing electrolytic corrosion. In the bearing device disclosed in Patent Document 1, the body of the bearing ring of the rolling bearing is a metal ring, and the outer circumference or inner circumference of the metal ring on the side opposite to the raceway surface is provided with a ground surface for the fitting surface of the bearing ring, and Form a dent that is radially recessed from the base surface, cover the peripheral surface of the metal ring on the base surface side with an insulating coating so as to follow the shape of the dent, or cover the surface on the base surface side so as to fill the dent is covered with an insulating film to reduce the capacitance between the bearing ring and the mating rotating shaft or housing, thereby increasing the impedance.

JP 2007-298060 A

However, as in Patent Document 1, one or more groove-like dents are formed on the metal ring, or a large number of dents are formed in a distributed arrangement, and the insulating coating is formed in a shape that follows the dents. In this case, a large number of recessed covering portions recessed from the fitting surface of the bearing ring are formed on the entire circumference of the insulating coating, and a gap is formed between the recessed covering portion and the mating fitting surface of the bearing ring. There is a concern that the thermal conductivity between the mating mating parts will deteriorate, and that the heat dissipation of the rolling bearing will be adversely affected.

In addition, since the recessed covering portion is formed in the insulating coating, it becomes difficult to mold the insulating coating, resulting in low mass productivity.

In addition, since there are corners and bent portions in the recessed covering portion, stress is concentrated at the bent portions, and the insulating coating is easily cracked or peeled off, lowering reliability.

In addition, since it is necessary to process a recess on the peripheral surface of the metal ring on the base surface side, the cost of the bearing ring increases.

On the other hand, it is possible to reduce the capacitance by increasing the thickness of the insulation coating over the entire surface without forming a recess in the metal ring, but this increases the amount of material used for the insulation coating, which increases the cost of the bearing ring. In addition, there is also a concern that the heat dissipation will decrease.

In view of the above background, the problem to be solved by the present invention is to provide a bearing device for supporting a rotating shaft included in a vehicle driving motor or a transmission connected to the vehicle driving motor with a rolling bearing to a housing. It is an object of the present invention to reduce the cost of a bearing ring provided in a rolling bearing while avoiding deterioration in the mass productivity of the bearing ring and the reliability of an insulating coating.

In order to achieve the above object, the present invention provides a rotating shaft included in a vehicle driving motor or a transmission connected to the vehicle driving motor, a housing provided around the rotating shaft, and a and a rolling bearing for supporting the rotating shaft, the rolling bearing comprising an inner bearing ring, an outer bearing ring, and interposed between the inner bearing ring and the outer bearing ring. and a retainer for holding the plurality of rolling elements, wherein one of the inner bearing ring and the outer bearing ring is connected to the rotating shaft and the housing. and a fitting surface of said one bearing ring that fits into said one member is made of an insulating coating, wherein said fitting surface and said one member , a clearance-fit configuration was adopted.

According to the above configuration, the insulating coating forming the fitting surface of one of the bearing rings and the one member, which is the mating member, are loosely fitted. By reducing the contact area with the capacitor, that is, by reducing the capacitance, a high impedance can be realized. Therefore, it is possible to reduce the film thickness of the insulating coating while eliminating the need to form a recessed covering portion in the insulating coating, thereby avoiding deterioration in the mass productivity of one bearing ring and the reliability of the insulating coating. The cost of the bearing ring can be suppressed.

Here, the vehicle drive motor in the present invention refers to an electrical device that converts electrical energy and outputs rotation that serves as a vehicle drive source, and an electrical device that converts input rotation into electrical energy during regenerative braking of the vehicle. It means what corresponds to at least one.

In addition, the transmission in the present invention means a device that converts the input rotational speed and transmits it to the output side, and a continuously variable transmission that can continuously change the speed conversion ratio (reduction ratio, gear ratio), The concept includes a fixed-ratio transmission in which the speed conversion ratio is fixed, and the fixed-ratio transmission includes what is called a speed reducer or a speed increaser that has only one type of speed conversion ratio. included.

A fitting clearance of 0.005 mm or more is preferably set between the fitting surface and the one member. In this way, in a bearing size that has a proven track record in applications for supporting a rotating shaft included in a vehicle driving motor or a transmission connected to a vehicle driving motor, the fitting surface of one bearing ring and the one member are The contact area can be reduced to about half or less compared to the case where there is no fitting clearance between them, and high impedance can be realized. Accordingly, it is possible to reduce the cost by thinning the insulating coating.

More preferably, the fitting clearance is 0.02 mm or more. By doing so, the aforementioned contact area can be reduced by about 70%, and the insulating coating can be made even thinner.

The film thickness of the insulating coating is preferably 0.05 mm or less. When the film thickness of the insulating coating is reduced to 0.05 mm or less in this way, the deformation of the insulating coating due to the radial load acting on the contact portion between the fitting surface of one bearing ring and the one member is reduced, thereby reducing the contact area described above. expansion can be suppressed and high impedance can be ensured.

The insulating film is preferably a fired film containing at least one of ceramics, polyphenylene sulfide resin, polyamideimide resin, and epoxy resin. These materials are suitable as insulating coating materials in terms of insulation resistance, dielectric breakdown voltage, mechanical strength, workability, and the like.

As described above, the present invention provides a bearing device for supporting a rotating shaft included in a vehicle driving motor or a transmission connected to a vehicle driving motor with a rolling bearing to a housing, by adopting the above configuration. It is possible to reduce the cost of the bearing ring while avoiding deterioration in the mass productivity of the bearing ring provided in the rolling bearing and the reliability of the insulating coating.

1 is a longitudinal front view showing a main part of a bearing device according to an embodiment of the invention; Side view of the bearing device of FIG. Schematic diagram showing an example of use of the bearing device shown in FIG. Enlarged view of the contact portion between the bearing ring and the housing shown in FIG. Sectional view showing a contact portion of a comparative example with respect to FIG. Graph showing the relationship between bearing ring and housing fit clearance and contact area in the calculation model

A bearing device according to an embodiment as an example of the present invention will be described with reference to FIGS. 1 to 6 of the accompanying drawings.

The bearing device shown in FIGS. 1 to 3 includes a housing 10, a rotating shaft 21 of a vehicle driving motor 20, and a rolling bearing 1 supporting the rotating shaft 21 with respect to the housing 10.

This bearing device is used as part of the rotation transmission device incorporated in the drive system of the vehicle. The rotation transmission device illustrated in FIG. 3 includes a vehicle drive motor 20 and a transmission 30 connected to the vehicle drive motor 20 . The transmission 30 comprises a plurality of rotating shafts 31-33, gears 34-36 provided on the respective rotating shafts 31-33, and a plurality of

rolling bearings

37, 38 supporting the

rotating shafts

31, 32, 33. Prepare. A rotating shaft 21, which is the motor shaft of the vehicle driving motor 20, is connected to a rotating shaft 31, and both

shafts

21, 31 rotate together. When the vehicle driving motor 20 serves as a driving source, the rotation input to the rotation shaft 31 of the transmission 30 is input from the rotation shaft 21 serving as the output shaft of the vehicle driving motor 20 , and the transmission 30 rotates the rotation input to the rotation shaft 31 . is reduced and output from the rotary shaft 33. When the vehicle driving motor 20 serves as a regenerative brake, the transmission 30 accelerates the rotation input to the rotating shaft 33 from the traveling wheel side and outputs it from the rotating shaft 31 to the rotating shaft 21 of the vehicle driving motor 20. It becomes a gearbox.

The rolling bearing 1 that supports the rotating shaft 21 and the rolling bearing 37 that supports the rotating shafts 31 to 32 are deep groove ball bearings. A rolling bearing 38 that supports the rotating shaft 33 is a tapered roller bearing.

As shown in FIGS. 1 and 2, the rolling bearing 1 is interposed between the inner bearing ring 2, the outer bearing ring 3, and the inner bearing ring 2 and the outer bearing ring 3. It has a plurality of rolling elements 4 and a retainer 5 that holds the plurality of rolling elements 4 .

In addition, hereinafter, the direction along the bearing center axis (not shown, hereinafter the same) of the rolling bearing 1 will be referred to as the "axial direction". A direction orthogonal to the axial direction is called a “radial direction”. Also, the direction along the circumference around the center axis of the bearing is referred to as the "circumferential direction". In FIG. 1, the bearing center axis is the center axis of the inner bearing ring 2 which is the rotating ring. FIG. 1 shows a cross section of an imaginary plane containing the bearing central axis. The axial direction corresponds to the horizontal direction in FIG. 1, and the radial direction corresponds to the vertical direction in FIG.

The inner bearing ring 2 is an annular member having a raceway surface 2a on the outer peripheral side that contacts the rolling elements 4 and a fitting surface 2b that is fitted to the rotating shaft 21 on the inner peripheral side.

The outer bearing ring 3 is an annular member having a raceway surface 3a on the inner peripheral side that contacts the rolling elements 4 and a fitting surface 3b on the outer peripheral side.

The rolling elements 4 are made of steel balls.

The retainer 5 is an annular bearing component that keeps the plurality of rolling elements 4 interposed between the inner and

outer raceway surfaces

2a and 3a at a predetermined circumferential interval.

The housing 10 has a fitting surface 10a provided around the rotating shaft 21. This fitting surface 10a is formed in the shape of a cylindrical surface. The housing 10 is made of, for example, an aluminum-based material.

The entire inner bearing ring 2 is made of steel.

The outer bearing ring 3 consists of a metal ring 6 having a raceway surface 3a on the inner peripheral side and an insulating coating 7 covering the outer circumference and both side surfaces of the metal ring 6.

The metal ring 6 is made of steel.

The insulating coating 7 is made of a coating layer made of a non-metallic material having insulating properties. The insulating coating 7 entirely follows the cylindrical outer diameter surface of the metal ring 6 . The film thickness of the insulating coating 7 is uniform over the entire surface. In FIG. 1, the thickness of the insulating coating 7 is greatly exaggerated in order to make it easier to understand.

Insulation coating 7 is made of at least one of ceramics, polyphenylene sulfide resin (PPS), polyamideimide resin (PAI), and epoxy resin from the viewpoint of insulation resistance, dielectric breakdown voltage, mechanical strength, workability, etc. is preferably a fired film containing In the case of ceramics, epoxy resins, and polyamide-imide resins, a baked film can be formed by heating the coated material. In the case of epoxy resins and polyamide-imide resins, it is also possible to bake them while including a curing agent.

Examples of ceramics include alumina (Al ₂ O ₃ ) and titania (TiO ₂ ). For example, the insulating coating 7 can be formed by forming a ceramic coating on the outer circumference of the metal ring 6 and impregnating the ceramic coating with an insulating synthetic resin such as PPS or PAI.

Also, the insulating coating 7 may be, for example, a synthetic resin composition containing at least one of PPS, PAI, and epoxy resin as a matrix resin and containing fibrous material that contributes to strengthening the matrix resin.

The film thickness of the insulating coating 7 can be, for example, 0.0010 mm or more and 1.0 mm or less. If the film thickness is unnecessarily thick, the cost will increase, so it is preferable to set the film thickness to 1.0 mm or less.

In particular, when a fired film containing PAI as a main component or a fired film containing PAI as a matrix resin is used as the insulating film 7, the film thickness of the insulating film 7 should be 0.005 mm or more, .100 mm or less is preferred. In this case, considering wear due to creep of the outer bearing ring 3 and insulating properties, it is more preferable that the film thickness of the insulating coating 7 is 0.010 mm or more and 0.050 mm or less.

A fitting surface 3b of the outer bearing ring 3 is made of an insulating coating 7. This fitting surface 3b is formed in the shape of a cylindrical surface that defines the outer diameter of the bearing ring 3 on the outer side.

The fitting surface 3b of the outer bearing ring 3 is fitted with the fitting surface 10a of the housing 10. A fitting surface 2 b of the inner bearing ring 2 is fitted with a rotating shaft 21 .

The maximum outer diameter of the fitting surface 3b of the outer bearing ring 3 is smaller than the minimum inner diameter of the fitting surface 10a of the housing 10. That is, the fitting surface 3b of the outer bearing ring 3 is loosely fitted with the housing 10 as one member of the rotating shaft 21 and the housing 10. As shown in FIG. The fitting clearance set between the fitting surface 3b of the outer bearing ring 3 and the fitting surface 10a of the housing 10 corresponds to the difference between the minimum inner diameter of the fitting surface 10a and the maximum value of the fitting surface 3b.

The portions where the housing 10 as one member and the outer bearing ring 3 as one bearing ring, which is a mating member, can come into contact in the radial direction are only the mutual fitting surfaces 3b and 10a. . The insulating coating 7 forming the fitting surface 3b cuts off a circuit through which a leakage current from the drive motor 20 flows, prevents electric discharge between the inner and outer bearing rings 2, 3 and the rolling elements 4, thereby preventing discharge between the inner and outer raceways. To prevent electrolytic corrosion of

rings

2, 3 and rolling elements 4.

As shown in FIG. 4, between the fitting surface 3b of the outer raceway ring 3 and the fitting surface 10a of the housing 10, a gap g is formed between the

fitting surfaces

3b and 10a over most of the region in the circumferential direction. While _a occurs, both

fitting surfaces

3b and 10a are in contact at the rest of the circumferential direction. A contact portion between the

fitting surfaces

3b and 10a is deformed by a radial load applied to the rolling bearing 1. As shown in FIG. Therefore, the contact portion between the

fitting surfaces

3b and 10a has a width Wa in a direction along a plane orthogonal to the radial load direction (downward direction in FIG. 4).

The greater the deformation of the insulating coating 7 due to the radial load, the greater the width Wa of the contact portion. As the width Wa of the contact portion increases, the contact area between the

fitting surfaces

3b and 10a increases. In order to suppress deformation of the insulating coating 7 due to radial load, the thickness of the insulating coating 7 is preferably 0.05 mm or less.

Here, the capacitance C due to the insulating coating 7 can be expressed by the following [Equation 1].

In [Equation 1], _ε0 is the dielectric constant of a vacuum, _εm is the dielectric constant of the insulating coating material, S is the contact area between the

fitting surfaces

3b and 10a, and d is the thickness of the insulating coating 7. From [Formula 1], it can be seen that the contact area S should be reduced in order to reduce the capacitance C, that is, to increase the impedance.

If the inner diameter of the fitting surface 10a of the housing 10 is reduced to change to the fitting surface 10b shown in FIG. Since the clearance becomes smaller than the example shown in FIG. 4 and the clearance _gb becomes smaller as a whole, the width Wb of the contact portion between the

fitting surfaces

3b and 10b becomes larger than the width Wa in the example shown in FIG. It becomes larger than the example, which is disadvantageous for high impedance. 4 and 5, the widths Wa and Wb are exaggerated in order to make it easier to understand the change in the contact area due to the difference in the fit clearance.

We calculated the relationship between the fitting clearance and the contact area, assuming a bearing size that has been used to support the rotating shafts of vehicle drive motors and transmissions. The calculation result is shown in FIG. Here, the calculation model was set to model number 6207 (bearing outer diameter φ72 mm).

As is clear from the graph in FIG. 6, when the fit clearance is 0.005 mm or more, the contact area can be reduced by more than half compared to when there is no fit clearance. In particular, when the fitting clearance is 0.020 mm or more, the contact area can be reduced by about 70%.

Therefore, by setting a fitting clearance of 0.005 mm or more, more preferably 0.020 mm or more, between the fitting surface 3b of the outer bearing ring 3 and the fitting surface 10a of the housing 10 shown in FIG. In a bearing size that has a proven track record for supporting rotating shafts such as motors for driving vehicles, the contact area between both

fitting surfaces

3b and 10a is reduced by 50% or more, more preferably by 70% or more to achieve high impedance between both

fitting surfaces

3b and 10a. It can be seen that it is possible to realize Therefore, even if the same capacitance is obtained, the film thickness of the insulating coating 7 is reduced by 50% or more when the fitting clearance is 0.005 mm or more. can be reduced by 70% or more, and the cost of the insulating coating 7 can be reduced.

The bearing device shown in FIGS. 1 to 4 is as described above, and includes a rotating shaft 21 included in a vehicle driving motor 20, a housing 10 provided around the rotating shaft 21, and a A rolling bearing 1 for supporting a rotating shaft 21 is provided, and the rolling bearing 1 comprises an inner bearing ring, an outer bearing ring, and a plurality of roller bearings interposed between the inner bearing ring and the outer bearing ring. and a retainer for holding the plurality of rolling elements, and one bearing ring 3 of the inner bearing ring and the outer bearing ring is connected to one of the rotating shaft and the housing. It is attached to a member (housing 10), and of one bearing ring 3, the fitting surface 3b that fits into one member 10 is made of an insulating coating 7, and the fitting surface 3b of one bearing ring 3 and one member 10 are loosely fitted, so that the contact area between the insulating coating and one member is reduced based on the fitting clearance, the capacitance is reduced, and high impedance is realized. be able to. As a result, in this bearing device, the outer circumference of the metal ring 6 is not recessed to increase the impedance, and the film thickness of the insulating coating 7 is reduced, so that one bearing ring 3 can be mass-produced and the insulating coating 7 can be reduced. The cost of one bearing ring 3 can be suppressed while avoiding deterioration in reliability.

Further, in this bearing device, a fitting clearance of 0.005 mm or more is set between the fitting surface 3b of one bearing ring 3 and the one member 10, so that the rotating shaft 21 of the vehicle driving motor 20 can be moved. Compared to the case where there is no fitting clearance between the fitting surface 3b of the bearing ring 3 and the member 10, the contact area is reduced to about half or less, and the Impedance can be achieved, and the insulating coating 7 can be made thinner to that extent, thereby reducing the cost.

In particular, in this bearing device, the fitting clearance between the fitting surface 3b of one bearing ring 3 and the one member 10 is 0.02 mm or more, so that the aforementioned contact area is reduced by about 70% and insulation is achieved. Coating 7 can be made thinner.

Further, in this bearing device, since the film thickness of the insulating coating 7 is 0.05 mm or less, the insulating coating 7 is not affected by the radial load acting on the contact portion between the fitting surface 3b of the bearing ring 3 and the member 10 on the one hand. By reducing the deformation of the contact area, the expansion of the contact area can be suppressed, and high impedance can be ensured.

Further, in this bearing device, the insulation coating 7 is a fired film containing at least one of ceramics, polyphenylene sulfide resin, polyamideimide resin, and epoxy resin, so that the insulation coating 7 has good insulation resistance and insulation. Breakdown voltage, mechanical strength, workability, etc. can be obtained.

In the illustrated example, the impedance is increased between the housing 10 and the outer bearing ring 3 of the rolling bearing 1 that supports the rotating shaft 21 of the vehicle driving motor 20, but the impedance between the inner bearing ring and the rotating shaft is high. It is also conceivable to attempt impedance conversion. In this case, the fitting surface of the inner bearing ring as one of the bearing rings is configured with an insulating coating, the fitting surface of the inner bearing ring and the rotating shaft as one member are loosely fitted, and the film thickness is Since it is only necessary to set the loose fitting clearance in the same manner, the illustration and explanation thereof will be omitted. In the illustrated example, the present invention is applied to the bearing device that supports the rotating shaft 21 of the motor for driving the vehicle 20. Even when the fitting surface of the bearing ring is formed of an insulating coating, the same application as in the case of the rolling bearing 1 may be applied, so illustration and explanation thereof will be omitted.

The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. Therefore, the scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and scope of equivalents of the scope of the claims.

1, 37, 38 Rolling bearing 2 Inner bearing ring 3 Outer bearing ring 3b Fitting surface 4 Rolling element 5 Cage 7 Insulating coating 10 Housing 20 Motor for driving vehicle 30

Transmission

21, 31 to 33 Rotating shaft

Claims

A rotating shaft included in a vehicle driving motor or a transmission connected to the vehicle driving motor, a housing provided around the rotating shaft, and a rolling bearing supporting the rotating shaft with respect to the housing. prepared,
The rolling bearing includes an inner bearing ring, an outer bearing ring, a plurality of rolling elements interposed between the inner bearing ring and the outer bearing ring, and a plurality of rolling elements. and a retainer for
one of the inner race and the outer race is attached to one member of the rotating shaft and the housing;
In a bearing device in which a fitting surface of said one bearing ring that fits into said one member is made of an insulating coating,
A bearing device, wherein the fitting surface and the one member are loosely fitted.
The bearing device according to claim 1, wherein a fitting clearance of 0.005 mm or more is set between the fitting surface and the one member.
The bearing device according to claim 2, wherein the fitting clearance is 0.02 mm or more.
The bearing device according to any one of claims 1 to 3, wherein the insulating coating has a thickness of 0.05 mm or less.
The bearing device according to any one of claims 1 to 4, wherein the insulating film is a fired film containing at least one of ceramics, polyphenylene sulfide resin, polyamideimide resin, and epoxy resin.