Shaft arrangement with a discharge device for diverting electrical currents from a rotor of an electric machine

Abstract

Shaft arrangement (1) comprising a housing (9) and a shaft (2) rotatably mounted as a rotor in the housing (9) and a discharge device (12) for discharging electrical currents from the rotatably mounted shaft (2), wherein the discharge device (12) comprises a contact element (15) slidably held in a guide housing (16) for forming an electrically conductive sliding contact between the contact cylinder (15) and the guide housing (16), and wherein the guide housing (16) is rotationally fixed in a recess of the housing (9), and wherein the contact cylinder (15) has a contact surface (15a) which bears against the end face (5, 5') of the shaft (2), and wherein the contact cylinder (15) is electrically conductively connected to the guide housing (16) directly or indirectly on the opposite side of the contact surface (15a), the electrically conductive connection being made via a strand (20) made of a low-resistance material, thereby characterizedthat the guide housing (16) is made of plastic with a cover (18) made of metal arranged at the front and bonded to it in a plastic injection molding process, and that the wire (20) is contacted on one side at the contact cylinder (15) and on the other side at the cover (18), and that the cover (18) is electrically connected to the housing (9).

Description

[0001] The invention relates to a shaft arrangement with a discharge device for discharging electrical currents from a rotor of an electric machine. State of the art

[0002] It is common practice to use a grounding device for rotating shafts in inverter-fed electric motors and other rotating electrical machines. Such grounding devices are known in a variety of embodiments and are often called grounding rings or grounding devices, to prevent harmful current flow through the rolling bearings during operation of the electrical machine. If the current is not grounded, it can flow through the rolling bearings and cause electrical corrosion, reducing the bearing life. In a typical strategy, grounding devices such as grounding rings are used in a fixed housing that prevents rotation of the grounding device. Bristles or other contact elements of the fixed grounding device can then be arranged in an axial or radial distribution on a rotating rotor shaft to create an electrical grounding path for excess current.For this purpose, the bristles or contact elements are contacted with the stator via connecting wires, so that the electric current flows through the discharge device and not through the bearings.

[0003] From WO 2022 / 135 715 A1, a current-discharge device for dissipating electrical currents from a rotor of an electric machine formed with a shaft is known. The current-discharge device has a slidable contact element housed in a casing, which forms an electrically conductive sliding contact between a contact surface of the contact element and an end face of the shaft. The contact element is electrically connected to the casing, which forms a guide, via a stranded wire. The casing or a cover element of the guide is made of a low-resistance material, e.g., aluminum, aluminum alloy, copper, or brass.

[0004] In this previously known discharge device, the contact element is held in a housing, which is designed as a one-piece, open-on-one turned part made of aluminum. In an alternative known embodiment, the housing is made in two parts and comprises a tube element and a cover element. The tube element and the cover element are connected to each other such that the tube element is open on one side and serves to receive the contact element.

[0005] Both of the aforementioned known designs are expensive to manufacture. The two-part housing also requires increased assembly effort.

[0006] WO 2023 / 247 441 A1 discloses a discharge device for discharging electrical currents from a rotor part of a machine formed with a shaft, with a movable contact element received in a guide device, wherein the contact element is spring-loaded to form a sliding contact on the shaft.

[0007] Brush arrangements for a commutator device of an electric machine are known from US 2 382 799 A and DE 10 2010 064 234 A1.

[0008] The object of the invention is to provide a shaft arrangement comprising a housing and a shaft mounted as a rotor rotating in the housing and a discharge device, which is characterized by simple assembly and cost-effective manufacturing. Description of the invention

[0009] The problem is solved with a wave arrangement according to the features of claim 1.

[0010] The shaft arrangement according to the invention, comprising a housing, a shaft rotatably mounted as a rotor in the housing, and a discharge device for dissipating electrical currents from a rotatably mounted shaft, includes a contact element slidably held in a guide housing to form an electrically conductive sliding contact between the contact cylinder and the guide housing. The contact cylinder has a contact surface that abuts the end face of the shaft, and the contact cylinder is electrically connected, either directly or indirectly, to the guide housing on the opposite side of the contact surface. The guide housing is made of plastic with a metal cover arranged at its end face and bonded to it by a plastic injection molding process.

[0011] According to the invention, the electrically conductive connection is made via a stranded wire made of a low-resistance material, wherein the wire is contacted on one side with the contact cylinder and on the other side with the cover. Preferably, the metal is brass.

[0012] The contact cylinder is electrically connected to the lid on the opposite side of the contact surface.

[0013] By manufacturing the guide housing as an injection-molded plastic part with an injected cover made of a low-resistance material, a guide housing is provided that is cost-effective in terms of material and can be produced using a simple injection molding process. This eliminates the need to assemble the cover and the pipe element separately.

[0014] Material costs can be saved by manufacturing the pipe element from a plastic material.

[0015] In a preferred embodiment, the discharge device has a spring-loaded contact cylinder that rests against the shaft end face. This ensures a sliding contact between the shaft and the contact element. Description of the characters Fig. Figure 1 shows a shaft with a discharge device in a longitudinal section. Fig. Figure 2 shows the discharge device in a detailed longitudinal section view.

[0016] The single figure shows a shaft assembly 1 consisting of a shaft 2 and a housing 9 or a bearing assembly and a discharge device 12. In an electric machine, the shaft 2 is the rotor and the housing 9 is the stator.

[0017] In this embodiment, shaft 2 has a cavity, the shaft interior 3. Shaft 2 is attached to the [unclear text] in the Fig. The end shown in Figure 1 is stepped in its diameter. In the exemplary embodiment, two steps can be seen, which end in a tapered wave region 4.

[0018] In this tapered shaft section 4, the shaft 2 is supported by bearings 8 in the housing 9 or in a bearing shield. The outer surface of the shaft 7 is in direct contact with the bearings 8. The housing 9 contains a supply line 10 for lubricating and cooling oil, as well as a return line 11 for the lubricating and cooling oil. The lubricating oil serves at least to lubricate the bearings 8.

[0019] The end face of the wave 2 has a wave edge 6 which surrounds a recessed wave end face 5 in a ring shape.

[0020] The discharge device 12 essentially comprises a guide housing 16 and a contact cylinder 15 with an end-face contact surface 15a. The discharge device 12 projects with its contact cylinder 15 and the contact surface 15a against the recessed shaft end face 5. The contact cylinder 15 is pre-tensioned in the guide housing 16 by a spring 13. The discharge device 12 sits in a recess of the housing 9 and is pressed into the housing 9 up to an edge 14 during assembly. Due to the pre-tension of the spring 13, the contact cylinder 15 of the discharge device is in contact with the shaft end face 5.

[0021] The lubricating oil flowing in via the supply line 10 flows directly into the interior space between shaft 2 and housing 9 in the area of ​​the bearings 8. The rotating shaft 2, more precisely the shaft edge 6, flings the lubricating oil outwards and away from the shaft end face 5. This keeps the shaft end face 5 largely oil-free.

[0022] In the Fig. Figure 2 shows the discharge device in a detailed view without installation in the housing 9 of the shaft arrangement 1.

[0023] Unlike the one in the Fig. In the wave arrangement shown in 1, the rotating wave 2 is designed without a step at its shown end region.

[0024] As previously described, the contact cylinder 15 contacts the end face 5' of the shaft 2 via the contact surface 15a. The contact cylinder 15 is arranged coaxially to the shaft 2 and, when the shaft 2 rotates, forms a sliding contact between the end face 5' of the shaft 2 and the contact surface 15a of the contact cylinder 15. At least the contact surface 15a of the contact cylinder 15 is designed as a carbon brush.

[0025] The contact cylinder 15 is slidably held in the guide housing 16 and spring-loaded towards the end face 5' by means of the spring 13, which is a helical compression spring. The contact cylinder 15 thus forms a sliding contact between the end face 5' of the shaft 2 and the contact surface 15a of the contact element 15.

[0026] The guide housing 16 is tubular and made of a plastic material, and at the end region opposite the contact surface 15a it comprises a cover 18 which is bonded to it in a material-bonded manner. The cover 18 is made of a metal, preferably brass.

[0027] To ensure rotationally fixed mounting of the contact cylinder 15 in the guide housing 16, the contact cylinder 15 has a rectangular, preferably square, cross-section. The receiving bore in the guide housing 16 is adapted to the cross-section of the contact cylinder.

[0028] The guide housing 16 is manufactured using an injection molding process, wherein the cover 18 is made of a low-resistance material, inserted into a mold, and overmolded with a plastic to achieve a material-bonded connection.

[0029] The lid is preferably made of aluminum or brass.

[0030] The lid has a central bore through which a wire 20 passes. The wire 20 is connected to the lid 18 on one side and to the contact element 15 on the other, thus forming an electrical conductor.

[0031] As can be seen from the Fig. As can be seen in Figure 1, the guide device 16 is held in the housing 9. The cover 18 is in contact with the housing 9 to establish an electrical connection. Reference sign 1 Wave arrangement 2nd wave 3 wave interior 4 tapered wave area 5.5' wave face 6 wavy edge 7 Outside Wave 8 bearings 9 cases 10 Oil supply line 11 Oil drainage 12. Drainage device 13 spring 14 Rand 15 contact cylinders 15a Contact area 16 guide housings 18 lids 20 strands

Claims

[1] Shaft arrangement (1) comprising a housing (9) and a shaft (2) rotatably mounted as a rotor in the housing (9) and a discharge device (12) for discharging electrical currents from the rotatably mounted shaft (2), wherein the discharge device (12) comprises a contact element (15) slidably held in a guide housing (16) for forming an electrically conductive sliding contact between the contact cylinder (15) and the guide housing (16), and wherein the guide housing (16) is rotationally fixed in a recess of the housing (9), and wherein the contact cylinder (15) has a contact surface (15a) which bears against the end face (5, 5') of the shaft (2), and wherein the contact cylinder (15) is electrically conductively connected to the guide housing (16) directly or indirectly on the opposite side of the contact surface (15a), the electrically conductive connection being made via a strand (20) made of a low-resistance material this is done characterized by, that the guide housing (16) is made of plastic with a cover (18) made of metal arranged at the front and bonded to it in a plastic injection molding process, and that the wire (20) is contacted on one side at the contact cylinder (15) and on the other side at the cover (18), and that the cover (18) is electrically connected to the housing (9). [2] Shaft arrangement (1) according to claim 1, characterized by that the metal is made of a low-resistance material and is preferably brass. [3] Shaft arrangement (1) according to claim 1 or 2, wherein the discharge device comprises a spring (13) which is arranged in the guide housing (16) such that the contact cylinder (15) is spring-loaded against the shaft end face (5, 5'). [4] Shaft arrangement (1) according to any one of the preceding claims, characterized by , that the lid (18) is made of aluminium. [5] Shaft arrangement (1) according to any one of the preceding claims, characterized by , that the contact cylinder (15) consists at least on one side of a carbon brush and that this brush forms a contact surface (15a) against the shaft end face.

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