Wind-up spring

The invention discloses a wind-up spring with a spring body, an inner hook and an outer hook being integrated. The spring body is in a curly shape. The inner hook is arranged at one end of the spring body and directly hung on a part in a mounting position. The outer hook is arranged at the other end of the spring body and hung on a bolt. One segment of the inner hook and one segment of the outer hook are removed in a stamping mode. A groove is formed in the part. The inner hook is hung in the groove. The bolt is a bolt provided with a nut. The wind-up spring provided by the invention has the beneficial effects that application of inner hook pins is reduced, the space utilization ratio is increased, the lightweight design is achieved, the danger that the inner hook and the outer hook of the spring slip off in the working process is avoided at the same time, normal operation of a plane volute spring is effectively guaranteed, accordingly emission is effectively reduced, emission of pollutants including nitric o