Universal joint and monitoring and early warning method and system for working state of universal joint

The invention discloses a universal joint and a monitoring and early warning method and system for the working state of the universal joint, the universal joint comprises a cross shaft, shaft necks are formed at the four ends of the cross shaft, shaft sleeves are arranged outside the shaft necks, and a closed chamber is formed between the shaft sleeves and the shaft necks, and the method comprises the steps that S100, the working temperature value t, the environment temperature value T, the vibration acceleration value A and the pressure value P are collected, a temperature rise threshold value Tmax, a vibration acceleration threshold value Amax and a pressure threshold value Pmax are set; s200, the working temperature value t and the environment temperature value T are subtracted to obtain a temperature rise value T; s300, T is compared with Tmax, A is compared with Amax, and P is compared with Pmax; if T is greater than or equal to Tmax, giving out early warning; if A is greater than or equal to Amax, givin