Drilling machine and transmission structure thereof

A transmission structure of a drilling machine comprising:

• a housing in which a first accommodation groove, a second accommodation groove, a third accommodation groove, and a fourth accommodation groove are defined;
• a drive shaft housed in the first accommodation groove, at least one guide shaft accommodated in the second accommodation groove, a speed shaft housed in the third accommodation groove, and a driven shaft accommodated in the fourth accommodation groove;
• a drive gear connected on the drive shaft and directly driven by a motor;
• at least one guide gear coupled on the at least one guide shaft and meshing with the drive gear;
• a speed change gear assembly connected on the speed shaft and including a connection gear, at least two speed change gears which are coaxially connected and have different diameters respectively, wherein the connection gear meshes with the at least one guide gear;
• a driven gear assembly coupled on the driven shaft and moving upward and downward along the driven shaft, and the driven gear assembly including at least two driven gears which are coaxially connected and corresponding to at least two speed change gears respectively, wherein the at least two driven gears have different diameters respectively, and the driven shaft drives a drill bit of the drilling machine;
• wherein when the driven gear assembly moves downward, one of the at least two driven gears with a larger diameter meshes with the first speed change gear so that the driven shaft rotates at a low speed;
• when the driven gear assembly moves upward, another of the at least two driven with a smaller diameter meshes with the second speed change gear so that the driven shaft rotates at a high speed.