Bearing cage with antenna and method for detecting failure of a bearing cage

A bearing unit comprising:

• a bearing providing a bearing cage having a bearing cage main body made of a polymer material and configured to accommodate at least one row of rolling elements of a bearing, and
• a passive resonant circuit including an antenna coil attached to the cage main body, wherein
• the antenna coil is formed as a conductive layer directly attached to the cage material of the bearing cage main body and is designed to have a breaking point lower than a breaking point of the cage material, and
• a transmitter including a primary antenna is connected to a ring or a seal of the bearing, wherein
• the primary antenna is configured to send and receive signals to and from the antenna coil, and
• a signal processing unit,
• the signal processing unit is configured to monitor a response signal from the antenna coil received by the primary antenna and to generate a warning upon detecting that no response signal is received or that a change in the amplitude or that a change in resonance frequency of the response signal has occurred,
• a second passive resonant circuit mounted in proximity to the transmitter on a stationary part of the bearing that is not subject to wear or damage and which is configured to emit a second response signal upon receiving an interrogation signal from the primary antenna, and wherein
• the processing unit is configured to generate a warning that the transmitter is defective if neither a first response signal from the passive resonant circuit on the cage nor the second response signal is received.