CN-122001161-A - Low impedance ground for an electric motor

CN122001161ACN 122001161 ACN122001161 ACN 122001161ACN-122001161-A

Abstract

A motor grounding system includes a hollow cylinder filled with a conductive medium. Rotary seals are attached to the hollow cylinder at opposite ends of the hollow cylinder to retain the conductive medium within the hollow cylinder. A rotor shaft is positioned within the motor, the rotor shaft having a hollow center that internally receives the hollow cylinder. The metal tube is connected to electrical ground. The metal tube is slidably inserted through the hollow center of the hollow cylinder, and the rotor shaft is conductively connected to the electrical ground through the metal tube and the conductive medium.

Inventors

A. Fatimi
Z. Strand
S.J.Zhou
J.M. Gaines
J P Spicer

Assignees

通用汽车环球科技运作有限责任公司

Dates

Publication Date: 20260508
Application Date: 20241218
Priority Date: 20241101

Claims (10)

1. A motor grounding mechanism comprising: A hollow cylinder filled with a conductive medium; A rotary seal attached to the hollow cylinder at opposite ends thereof to retain the conductive medium within the hollow cylinder; A rotor shaft positioned within the motor, the rotor shaft having a hollow center that internally accommodates the hollow cylinder, and A metal tube connected to an electrical ground, the metal tube slidably inserted through the hollow center of the hollow cylinder, the rotor shaft conductively connected to the electrical ground through the metal tube and the conductive medium.
2. The motor grounding mechanism of claim 1, wherein the motor includes a housing defining the electrical ground, the metal tube fixedly connected to the housing.
3. The motor grounding mechanism of claim 2, wherein the rotor shaft rotates relative to a longitudinal axial centerline of the rotor shaft, the rotor shaft extending through the housing and being caused to rotate by passing current through the windings.
4. The motor grounding mechanism of claim 1, wherein the metal tube is stationary during operation of the motor, wherein the hollow cylinder is fixed to and co-rotates with the rotor shaft.
5. The motor grounding mechanism of claim 1 including a biasing member defining one of a spring and a garter spring positioned behind a seal lip, the seal lip acting in one of lateral compression and vertical compression, the biasing member providing one of an axial force and a radial force to maintain contact between the seal lip and a shaft surface of the rotor shaft.
6. The motor grounding mechanism of claim 1 including a flexible spring loaded tip for maintaining contact with said hollow cylinder and compensating for cylinder surface irregularities.
7. The motor grounding mechanism of claim 1, wherein the hollow cylinder forms a first cylinder member and a second cylinder member and includes an airtight seal between the first cylinder member and the second cylinder member to prevent contaminants and moisture from entering the grounding mechanism.
8. The motor grounding mechanism of claim 1, comprising a slot on at least one of a cylinder surface of the hollow cylinder and an inner diameter surface of the hollow cylinder that directs air into the rotor shaft to enhance ventilation and cooling of the motor during operation.
9. The motor grounding mechanism of claim 1 including a passageway formed in said hollow cylinder to direct the passage of oil to enable cooling of said rotor and said electrically conductive medium.
10. The motor grounding mechanism of claim 1, comprising a surface feature extending from the metal tube, the surface feature defining a fin that enhances contact with the conductive medium, wherein the conductive medium defines a conductive grease.

Description

Low impedance ground for an electric motor Technical Field The present disclosure relates to grounding of an electric motor. Background During operation of the electric vehicle, one or more electric motors may be used for propulsion of the vehicle. The motor includes a rotor that rotates axially to generate, via friction, a low impedance charge that needs to be dissipated. Providing a ground path to the axially rotating motor rotor is complex and may be provided using an external ground path. Thus, while the current systems and methods of discharging charge from an operating motor achieve their intended purpose, there is still a need for a new and improved system and method for grounding the vehicle motor rotor. Disclosure of Invention According to several aspects, a motor grounding system includes a hollow cylinder filled with a conductive medium. Rotary seals are attached to the hollow cylinder at opposite ends of the hollow cylinder to retain the conductive medium within the hollow cylinder. A rotor shaft is positioned within the motor, the rotor shaft having a hollow center that internally receives the hollow cylinder. The metal tube is connected to electrical ground. A metal tube is slidably inserted into the hollow center of the hollow cylinder and the rotor shaft is conductively connected to electrical ground through the metal tube and conductive medium. In another aspect of the present disclosure, an electric motor includes a housing defining an electrical ground, a metal tube fixedly connected to the housing. In another aspect of the present disclosure, the rotor shaft rotates relative to a longitudinal axial centerline of the rotor shaft, the rotor shaft extends through the housing, and is inductively rotated by passing current through the windings. In another aspect of the present disclosure, the metal tube is stationary during operation of the motor, wherein the hollow cylinder is fixed to and co-rotates with the rotor shaft. In another aspect of the present disclosure, a biasing member defining one of the spring and the garter spring is positioned behind the seal lip, the seal lip acting in one of lateral compression and vertical compression, the biasing member providing one of an axial force and a radial force to maintain contact between the seal lip and a shaft surface of the rotor shaft. In another aspect of the present disclosure, a flexible spring-loaded tip is used to maintain contact with the hollow cylinder and to compensate for irregularities in the surface of the cylinder. In another aspect of the disclosure, the hollow cylinder is formed as a first cylinder and a second cylinder and includes a hermetic seal between the first cylinder and the second cylinder to mitigate contaminants and moisture from entering the grounding mechanism. In another aspect of the present disclosure, a slot on at least one of the cylinder surface of the hollow cylinder and the inner diameter surface of the hollow cylinder directs air into the rotor shaft to enhance ventilation and cooling of the motor during operation. In another aspect of the present disclosure, passages formed in the hollow cylinder direct oil therethrough to enable cooling of the rotor and the conductive medium. In another aspect of the present disclosure, surface features extending from the metal tube define fins that enhance contact with a conductive medium that defines a conductive grease. According to several aspects, a motor grounding system includes a vehicle having a motor positioned in a housing. The rotor shaft of the motor, which rotates axially within the housing, has a hollow center. The hollow cylinder has a cylinder cavity communicating with the hollow center of the rotor shaft. A plurality of rotary seals are connected to the hollow cylinder. An electrical ground is formed between the rotor shaft, the hollow cylinder and the housing to dissipate parasitic voltages generated by rotation of the rotor shaft. In another aspect of the present disclosure, a cartridge assembly includes conductive grease filled within a hollow cylinder, and a plurality of rotary seals are connected in the hollow cylinder on opposite ends of the hollow cylinder to retain the conductive grease within the hollow cylinder. In another aspect of the present disclosure, a metal tube connected to the housing defines an electrical ground, the metal tube slidably inserted through the rotary seal and the hollow center of the hollow cylinder and extending into and in contact with the conductive grease, the rotor shaft conductively connected to the electrical ground through the metal tube and the conductive grease that internally receives the hollow cylinder, and wherein the metal tube remains stationary and the hollow cylinder rotates with the rotor shaft during operation of the motor. In another aspect of the disclosure, the hollow cylinder is made of two parts, including an inner part and an outer part, with an airtight seal and a plurality of air passages