International patent classification is a general international patent literature classification. The classification number obtained by classifying patent documents (specifications) with the international patent classification table is called the international patent classification number, which is usually abbreviated as IPC number. IPC adopts the classification principle of combining function with application, with function as the main and application as the auxiliary. In the hierarchical form, the technical contents are marked as follows: Department-Division-Class-Class-Group-Group, and a complete classification system is gradually formed.