A method of adjusting positions of dots in an original halftone image for improving quality of printed images, the original halftone image including a plurality of pixels containing either dots to be printed or blank spaces. A single unit includes copper blocks, an insulating substrate with a conductive pattern, an IGBT chip, a diode chip, a collector terminal pin, implant pins fixed to the chips by solder, a printed circuit board having the implant pins fixed thereto, an emitter terminal pin, a control terminal pin, a collector terminal pin, and a resin case having the above-mentioned components sealed therein. In other words, the control characteristics of the target value are determined correspondingly to the air conditioning load characteristics of a building, and the target value is altered according to the control characteristics and based on the insideoutside temperature difference between an indoor set temperature and an outside air temperature. Variations in a drive torque of the drilling mechanism are determined. The clad piping or tubing formed in also disclosed.