Balance bar connecting structure for key and satellite shaft structure for same

A balance bar connecting structure for a key, comprising:

• two satellite shaft modules, each of which includes a base body and a satellite shaft member movably arranged on the base body;
• and
• a balance bar member having a connecting bar section, two linkage sections respectively bent in a same direction from both ends of the connecting bar section, and two sliding sections respectively bent relative to each other from the two linkage sections, wherein the connecting bar section comprises a single straight bar pivotally connected between the two base bodies such that a first end of the single straight bar is connected at a center of one of the satellite shaft modules and a second end of the single straight bar is connected at a center of another satellite shaft module, and the two linkage sections face the two satellite shaft members, respectively, so that the two sliding sections are cooperatively connected to the two satellite shaft members, wherein each linkage section extends through a center of a base body of one of the two satellite shaft modules and is at least partially contained within the base body;
• wherein the two satellite shaft members are each provided with a sliding groove so as to allow the two sliding sections to slide transversely in the sliding grooves, respectively.