| The transmission ratio of helical gear and worm drive mechanism is big, drives smooth and can be self-locked, it is used to transmit power of two spaces interlaced shaft. Plastic helical gear is easy to design and machining, light weight, good self-lubrication, low noise and low manufacturing cost, it is widely used in the field of automotive, machinery, electrical appliances. Therefore, the research on plastic helical gear and steel worm drive mechanism has very important application value.Based on the project of " Automatic control clutch system of small passenger car ", the project number is 2012GH710902, the main research in this thesis is theoretical and experimental study on parameters design, transmission efficiency, self-locking of plastic helical gear and steel worm drive mechanism, dynamic finite element of tooth surface stress is analyzed. The research provides the guidance for parameters design, material selection, process selection of helical gear and worm drive mechanism, which has practical value.According to the analysis on input and output power of helical gear and worm, transmission efficiency, transmission conditions and self-locking condition have been researched, the influence of pressure angle, spiral angle and friction coefficient for the transmission efficiency and self-locking has been analyzed. The transmission efficiency and self-locking performance test has been done. The results shows that the transmission efficiency decreases along the increases of friction coefficient, yet the self-locking capability enhances. The transmission efficiency increases along the increases of spiral angle, and the self-locking capability weakens. The transmission efficiency decreases along the increases of pressure angle, and the self-locking capability enhances. The spiral angle is about 5.2 ° and the friction coefficient is about 0.09, which is the self-locking critical reference value of plastic helical gear and steel worm. The research on influence of design parameters for transmission efficiency and self-locking of helical gear and worm drive has a instructive significance to measuring worm gearings’ transmission efficiency and self-locking in the parameter design stage.Dynamic finite element is conducted to analysis the plastic helical fear and steel worn transmission mechanism of a certain vehicle automatic control clutch system, tooth surface stress distribution and changing condition of plastic helical gear when meshing have been researched. When the number of teeth is 69, the pressure angle is 10.5 °, spiral angle is 5.16 °, three teeth of the helical gear and worm drive mechanism in this thesis are the main meshing tooth, the maximum stress of tooth surface changes smaller. Tooth surface meshing point of helical gear moves along addendum to tooth root, then moves back a smaller displacement along meshing point track in the direction of addendum after near the tooth root. There is an angle between meshing track and helical gear end face. Higher contact stress appears on tooth root of helical gear. The smaller material modulus of elasticity of helical gear, the longer meshing time. The research can provide a reference to carry out simulation analysis work of gear and worm drive products in enterprise.The plastic helical gear and steel worm drive mechanism has been applied in a certain vehicle automatic control clutch system in enterprise according to the parameter selection method in this thesis, the mechanical strength and transmission performance can meet the operating requirement. The regularity of helical gear and worm transmission parameters for transmission efficiency and self-locking, dynamic contact finite element analysis process in this thesis has been applied to the new product research and development of worm drive in enterprise, which has a guiding significance to series of product design of gear and worm drive. |
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