Gear Measurement SRM University（齿轮测量 SRM大学）.pdfVIP

Gear Measurement Topics • Introduction • Gear schematics • Types of gears • Measuring gears What is a gear ? A gear is a wheel with teeth that mesh together with other gears. Gears change the : • speed • torque (rot. force) • direction of rotating axles. What is a gear ? (cont’d) • Purpose : to transmit rotary motion and force. • Gears are used in groups of two or more. • A group of gears is called a gear train. • The gears in a train are arranged so that their teeth closely interlock or mesh. • The teeth on meshing gears are the same size so that they are of equal strength. The spacing of the teeth is the same on each gear. Gear schematic Figure : Gear schematic Gear schematic (cont’d) • Base circle : The circle from which involute form is generated. Only the base circle on a gear is fixed and unalterable. • Pitch circle : It is an imaginary circle most useful in calculations. An invinite number of pitch circles can be chosen, each associated its own pressure angle. • Pitch Circle Diamter (PCD) : Diameter (D) of a circle which by pure rolling action would produce the same motion as the toothed gear wheel. This is the most important diameter in gears. • Module : Defined as the length of the pitch circle dia. per tooth  D ( ) = ; = , = number of teeth module m D PCD N N • Circular pitch (CP) : The arc distance measured around the pitch circle from the f