A spiral spring is a special type of helical spring, shaped like a planar Archimedean spiral or concentric spiral. It utilizes a highly elastic metal strip (usually spring steel or stainless steel) to store potential energy during winding. The core working principle is based on Hooke's law of elastic deformation, but manifests uniquely: when one end of the spring is fixed and the other end is subjected to a rotational torque, the metal strip tightens or loosens around its central axis, converting mechanical energy into stored elastic deformation energy, and releasing the energy when the torque is unloaded, returning to its original shape.
This structure avoids the axial space occupation of traditional helical springs, storing energy within a compact planar or cylindrical space. Its torque and rotation angle typically exhibit a good linear relationship. The key to its design lies in precisely controlling the cross-sectional dimensions of the strip, the material's yield strength, and the frictional losses between the spirals to ensure efficient energy conversion and a long service life.
The Precise Process of Energy Storage and Release
Energy storage density is a key performance indicator of a spiral spring. Compared to other types of springs, its uniform stress distribution allows for the storage of more energy within a limited volume. When an external force is applied to the movable end arm, the metal strip winds uniformly from the outside in or from the inside out, generating continuous, smooth bending stress within the material. This process requires the material to possess extremely high fatigue limits and uniform mechanical properties; any microscopic defects can lead to stress concentration and premature failure.
The release process is the reverse of the storage process, but it is not a simple recovery. The spring must provide a stable and controllable torque output upon rebound, which is crucial for the dynamic smoothness of wind-up mechanisms. Engineers optimize the material's elastic modulus and relaxation resistance through heat treatment processes and reduce interlayer friction through surface treatments, achieving an energy release efficiency of over 90% while maintaining reliability for millions of cycles.
