How to apply for a new patent after upgrading an existing patented product?

Hello, first of all, the utility model can only be a product, not a method, so your technology must first be clear that it is not a method, but a product, and it cannot be ambiguous in the claims. Secondly, when you say that a new component C has been added, you can write it like this: a xxx, which is composed of A and B, is characterized by also including C, and explains the position of C or its composition relationship with other components. It is best not to define c with functions.