Planar four-bar mechanism teaching demonstration instrument

The utility model discloses a planar four-bar mechanism teaching demonstration instrument comprising a machine frame, frame connecting rods and a connecting rod. There are two frame connecting rods. One of the two frame connecting rods is a fixed-length frame connecting rod, and the other frame connecting rod is a variable-length frame connecting rod. One end of the fixed-length frame connecting rod is slidably connected on the machine frame, and the other end is hinged with the connecting rod. One end of the variable-length frame connecting rod is fixedly connected on the machine frame, and the other end is slidably hinged on the connecting rod. One end, which is positioned outside the hinged point of the variable-length frame connecting rod and the connecting rod, of the connecting rod is provided with a chalk sleeve. A chalk can be arranged in the chalk sleeve to be used for drawing a connecting rod curve. One side, which faces a blackboard, of the machine frame is provided with multiple magnetic blocks. Multiple planar four-bar mechanisms can be demonstrated by the planar four-bar mechanism teaching demonstration instrument so that the planar four-bar mechanism teaching demonstration instrument is convenient to use and excellent in the demonstration effect.