Abstract
For a caged spiral power spring, its moment of inertia varies with the time in energy storage and is closely related to the states of spring strip. Due to continuous changing of the shape in energy storage, calculation of variable moment of inertia for spiral power spring is a highly challenging but important issue. A general analytical model and calculation method of variable moment of inertia for spiral power spring are proposed in this article. First, the contraction process of spiral power spring in energy storage is clearly revealed and analytical model of spiral power spring on the basis of contraction process is presented. In terms of the contraction characteristic, a general calculation method based on divisions of stage and state for variable moment of inertia is put forward. Finally, a spiral power spring is designed, and a prototype of the spring is developed. The proposed model and general calculation method are applied into the prototype to calculate its variable moment of inertia, and they are evaluated by a developed experimental scheme.
Highlights
Due to the advantages of low torque change, relatively large curvature variability, and high security, spiral power spring (SPS) is widely utilized in industry for energy storage, such as an actuator,[1] timekeeping device,[2] energy storage equipment,[3] and driven toys
A general analytical model and calculation method based on the divisions of stage and state for variable moment of inertia of SPS are proposed in this article
The states of the spring in energy storage process involve three types, which are clamped to the internal wall of housing, free state, and wound down on the inner shaft
Summary
Due to the advantages of low torque change, relatively large curvature variability, and high security, spiral power spring (SPS) is widely utilized in industry for energy storage, such as an actuator,[1] timekeeping device,[2] energy storage equipment,[3] and driven toys. A general analytical model and calculation method based on the divisions of stage and state for variable moment of inertia of SPS are proposed in this article. If radius of curvature for a portion of strip coils uncaged in the free configuration is less than cA, those strips will wound down on the inner shaft after caged Those strips would not contribute to energy storage, resulting in unnecessary waste of materials. For the caged spiral spring, when an external torque imposed on the spring rotates the inner shaft, the strip coils clamped to the internal wall of the housing will successively go into free space from the boundary point B. The states of the spring in energy storage process involve three types, which are clamped to the internal wall of housing, free state, and wound down on the inner shaft. Considering a general case, we suppose that a portion of strip coils is clamped to the internal wall, and the remaining strips are in a free state
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