Shaft arrangement of an axially acting shaft grounding and method for shaft grounding

Abstract

Shaft arrangement (1) having a shaft (2) which is supported at least on one side in a housing (9) or bearing cover via a bearing, having a shaft grounding (12) in which an oil supply is provided, characterized in that the shaft grounding (12) is arranged coaxially to the shaft (2) on the end side.

Description

Technical Field

[0001] The present invention relates to a shaft assembly having a shaft, a support device, and a shaft grounding device.

[0002] Furthermore, the present invention relates to a method for grounding a shaft. Background Technology

[0003] In converter-fed motors and other rotating electrical machines, grounding devices are typically used for the rotating shaft. Grounding rings or other grounding devices are used to prevent harmful current from flowing through the rolling bearings. If the current is not grounded, it may flow through the rolling bearings and cause electro-corrosion, which shortens the bearing's lifespan. In a typical strategy, grounding devices, such as grounding rings, are used in a fixed housing that prevents rotation of the grounding device. The bristles or other contact elements of the fixed grounding device can then be run on the rotating rotor shaft to provide an electrical grounding path for excess current. The current can preferably flow through the grounding device and not through the bearing, thereby preventing or reducing bearing corrosion.

[0004] An electrical grounding mechanism is known from US 4,515,417 B1. The prior art provides a grounding device that prevents electrolytic corrosion in the bearings of an electrically rotating machine. The grounding device has a centrifugal contact point between a conductive end cap and the inner surface of a rotor shaft. The contact portion includes a spring-preloaded contact element that extends inward in the rotor shaft and contacts a portion of the end cap that extends into the rotor shaft. When the rotor is stationary or rotating at a low speed, the contact element maintains electrical contact between the rotor shaft and the end cap. However, as the rotor speed increases, inertia tends to cause the contact element to move radially outward against the spring preload, causing the contact element to stop establishing electrical contact between the rotating rotor shaft and the end cap.

[0005] Document DE 10 2021 214 533 A1 discloses a shaft assembly having a rotatably supported shaft and a shaft grounding device that is in contact with the ground at one end.

[0006] US 5,661,356 A discloses a grounding system for an AC or DC motor, wherein a conductive brush is in elastic contact with a conductive element that is detachably secured to a rotating component, such as a motor shaft or a tachometer shaft.

[0007] DE 10 2004 050 477 A1 includes a commutator disposed on the shaft of an electric motor, wherein the commutator has an oil-slinging structure and a recovery structure.

[0008] US 2010 / 0 127 585 A1 includes a grounding mechanism for an electric motor rotor, the grounding mechanism having a shaft end defining a longitudinal axis and having a first axial end portion, a second axial end portion, and a plurality of axial shaft end sections, including a fastening section adjacent to the first axial end portion and adapted to be pressed into an electric motor housing, an electrical contact section adjacent to the second axial end portion, and a sealing section extending between the fastening section and the contact section. The fastening section has a first diameter, the contact section has a second diameter larger than the first diameter, and the sealing section has a third diameter larger than both the first and second diameters. The grounding mechanism also includes an electrical grounding ring that can be positioned about the shaft end and adapted such that the electrical grounding ring can be pressed into an axially extending bore defined by the rotor shaft of the electric motor. The electrical grounding ring includes an outer circumference having a cylindrical outer surface and an inner circumference having an electrical contact interface. The outer surface is adapted to contact a rotor shaft in an axially extending bore. The electrical contact interface is configured to electrically connect the electrical grounding ring to a shaft end by contacting the shaft end in a circumferential direction around a grounding section. The grounding mechanism also includes a sealing element that can be positioned around the shaft end and is also adaptable to be pressed into an axially extending bore defined by the rotor shaft of the motor. The sealing element includes a cylindrical outer surface and a sealing lip that extends radially inward and is configured such that the sealing lip forms a fluid seal with the shaft end by contacting the shaft end in a circumferential direction around a sealing section.

[0009] Attempts to axially mount the shaft grounding device failed because the contact surface between the shaft and the grounding device was in a moist, oil-covered environment, and sealing was costly. However, the oil at the contact surface reduces discharge capability and should be avoided. Reduced discharge capability is accompanied by poor bearing voltage suppression and increased electromagnetic waves emitted through the output axial environment of the drive system.

[0010] The purpose of this invention is to provide an improved solution for axially mounted shaft grounding devices. Summary of the Invention

[0011] The objective is achieved by means of a shaft assembly having a shaft supported on at least one side in a housing or bearing cover via a bearing, the shaft assembly having a shaft grounding device having an oil supply portion to at least the bearing, and the shaft grounding device being coaxially contacted with the shaft at the end side.

[0012] The shaft end side is axially retracted relative to the shaft edge, and the shaft grounding device is axially abutted against the shaft end side.

[0013] The shaft is designed in the contact area such that the incoming oil for bearing lubrication is blocked due to the forward geometry.

[0014] Furthermore, any remaining oil is flung outwards by centrifugal force, and the contact area of ​​the shaft remains dry. Therefore, the function of the shaft grounding device is not impaired.

[0015] The axial edge is composed of a cylindrical or conical shape.

[0016] The shaft grounding device has a spring-loaded contact post that rests against the shaft end.

[0017] The objective is also achieved by means of a method for grounding the shaft in the shaft assembly, wherein the supplied oil is thrown off the shaft end side via the shaft edge.

[0018] This shaft end design prevents the inflow of new oil during operation and allows for the rapid expulsion of existing oil. This ensures excellent oil discharge capability.

[0019] The output function remains unaffected. Efficient bearing voltage suppression is ensured, thereby guaranteeing protection against bearing electrolytic corrosion. Furthermore, EMV emissions via the output shaft are reduced to meet required EMV limits. Attached Figure Description

[0020] Figure 1 The shaft is shown connected to the coaxial grounding device. Detailed Implementation

[0021] The only accompanying drawing shows a shaft assembly 1, which consists of a shaft 2, such as a rotor shaft, and a housing 9 or a bearing assembly.

[0022] In the embodiment, the shaft has a cavity, i.e., an internal space 3. The shaft 2, as shown in the figures, has a stepped change in diameter at its end. Two steps are visible in the embodiment, which terminate in a tapering shaft region 4.

[0023] In the tapering shaft region 4, shaft 2 is supported in housing 9 or bearing cover via bearing 8. The outer side 7 of the shaft is in direct contact with bearing 8. Housing 9 contains inlet lines 10 for lubricating oil and outlet lines 11 for lubricating oil and cooling oil. Lubricating oil is used here at least to lubricate bearing 8.

[0024] The shaft 2 has a shaft edge 6 on its end side, which circumferentially surrounds the retracted shaft end face 5. The shaft grounding device 12 extends to the retracted shaft end face 5 with its contact post 15. The contact post 15 is preloaded within the housing of the shaft grounding device by means of a spring 13. The shaft grounding device 12 is located in a recess of the housing 9 and is pressed into the housing up to the edge 14 during installation. The contact post 15 contacts the shaft end face 5 due to the preload of the spring 13.

[0025] The lubricating oil flowing in via the inlet pipe 10 flows directly into the internal space between the shaft 2 and the housing 9 in the area of ​​the bearing 8. Here, the lubricating oil is thrown off by the rotating shaft 2, more precisely by the shaft edge 6, and from the shaft end face 5. Thus, the shaft end face 5 remains largely oil-free.

[0026] In the illustrated embodiment, the shaft edge 6 is a cylindrical wall, but it is also possible for the shaft edge 6 to be tapered in order to additionally assist the throwing function.

[0027] List of reference numerals

[0028] 1-shaft assembly

[0029] 2-axis

[0030] 3-axis internal space

[0031] 4. Gradual narrowing axial region

[0032] 5. Shaft end face

[0033] 6-axis edge

[0034] 7. Outer side of axis

[0035] 8 bearings

[0036] 9. Shell

[0037] 10. Oil inlet pipeline

[0038] 11. Oil discharge pipeline

[0039] 12-axis grounding device

[0040] 13 Springs

[0041] 14 Edge

[0042] 15 Contact column

Claims

1. A shaft assembly (1) having a shaft (2) supported on at least one side via a bearing in a housing (9) or bearing cover, the shaft assembly having a shaft grounding device (12) wherein an oil supply portion is provided at least to the bearing, characterized in that, The shaft grounding device (12) is coaxially in contact with the shaft (2) at the end side, characterized in that the shaft end side of the shaft (2) is axially retracted relative to the shaft edge (6), and the shaft grounding device (12) is axially abutted against the shaft end side (5), and the shaft edge (6) is cylindrical or conical.

2. The shaft device according to claim 1, characterized in that, The shaft grounding device (12) has a spring-loaded contact post (15) that abuts against the shaft end side (5).

3. A method for grounding a shaft (2) in a shaft assembly (1) according to any one of claims 1 to 2, wherein supplied oil is thrown off from the shaft end side (5) via the shaft edge (6).

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