2. why are the sizes of gears usually different in width and B2 > B1?3. briefly describe the design points of the gear parts working diagram
3. the main points of the design of gear working diagram are as follows:1) select the horizontal position of the axis, draw the main view, and then draw other views if the spokes, keyway, structure and size are expressed;2) marking the size of gear and its shape and position tolerances, such as the top of the tooth, the runout of the end face, the symmetry of the keyway, etc.3) mark the surface roughness, and the roughness of the contact surface is higher;4) according to the "gear manual" or "mechanical design manual" or "mechanical design" teaching materials for tolerance group values, and in the upper right corner of the drawing list mark the number of gear teeth and tolerances, the specific format refer to the specification of gear working diagram;5) write requirements for heat treatment, no fillet, chamfer requirements, and deburring requirements6) fill out the spare parts list
. a small gear and a big gear bearing force and reaction force, so the same size, but in the reverse direction. The design is based on the size, the gear tooth width coefficient to calculate the same tooth width, namely pitch diameter tooth width = tooth width coefficient * small gear, but need round. In order to prevent the mutual axial wrong two gear assembly after the dynamic contact width decreases, so the width of the small gear tooth based on the calculated value of widening 5~10mm
. due to the small gear tooth meshing gear meshing frequency than the large number, which is a small number of gear tooth surface contact, and the contact due to relative sliding will produce friction and wear, such as adhesive wear and abrasive wear, due to repeated stress contact fatigue pitting wear, in order to balance the two gear the wear, so to improve the small gear tooth surface hardness;
