A power element-valve housing combined type thermal expansion valve has a diaphragm (19) in an element (20) and a driving member (22) for driving a valve body (18) in a housing (10) by a diaphragm deflection. The diaphragm has a center opening surrounded by a tubular projection (34), the driving member has an outer flange (22b) coaxially supporting the diaphragm and a heat-balance containing blind hold opened to a heat sensitive working fluid in a sealed chamber in the element. A diaphragm catch (36) fits on the projection's periphery and is airtightly welded with a coaxial annular ridge (30) on a supporting surface of the flange to sandwich the diaphragm with the flange. <IMAGE> <IMAGE>
