Initiative Tribology Design Of Involute Helical Cylindrical Gear Transmission

According to the authoritative estimates, wear and friction energy accounted for about1/3of total energy. Recent studies show that, the money by saving gains is equal to50times research and development investment funds, these savings are not only realistic and important, it does not need to invest a lot of money. The purposes of studying on the tribological is to reduce the loss caused by the surface friction and wear, improve the production efficiency, improve product performance, reduce the failure parts, and save valuable resources.The recent contact fatigue strength design procedure of the involute cylindrical gear transmission is usually ascertained the main dimensions of gear based on Hertz theory first. Then the lubrication conditions are passive checking. It always has a result that in some gear driven especially low-speed heavy-duty gear will fail because of poor lubrication. Therefore, it is necessary to synchronize design of the lubricating conditions in the strength design. This design method is called the initiative tribology design of gear transmission.This article, based on based on the Hertz theory and the theory of elastohydrodynamic lubrication, combines the existing gear surface contact fatigue strength design whith the lubrication design formula organically, establishes initiative tribology design model of involute helical cylindrical gear transmission. Based on this model, the computer program is developed by VB language; then using this program,31different conditions are calculated, analyzing theoretically the influence of the gear driven design result from the gear speed, precision grade, transmission power (load), lubricant viscosity and the thickness of oil film. The contents of this paper can be summarized, main results as follows:1. While keeping the accuracy grade, oil film thickness, lubricant viscosity and other parameters unchanged, the small gear pitch circle diameter d decreases with increasing gear rotational speed n. When the gear rotational speed is low, the value of d according to the lubrication and tribology design model calculated sharply reduced with the increase of rotational speed n;In the condition of medium speed, d curve is relatively flat, along with the change of n. For high-speed transmission, the results based on the three design model calculation converge gradually. Needs to be emphasized is that under any operating conditions, the results according to tribological design model can meet the strength conditions and lubrication requirements at the same time.2. For medium and heavy-load gear transmission, when the gear speed n is relatively low, the result calculated on the basis of the theory of strength design can not meet the lubrication requirements. An advice at this time that use the tribological model to design which is proposed in this paper; when the gear speed n is higher, the current strength design results can basically satisfy the lubrication requirements; when the gear transmission is in a state of medium speed, in order to meet the lubrication requirements, by current strength theory to design the size increases by more than50%.3. Under the premise of keeping the gear speed, precision grade, transmitted power (load) and lubricant viscosity fixed, the value of d based on the lubrication and tribology design models increased almost linearly with the increase of oil film thick λ.4. Under the same working condition, the gear precision grade is higher, the small gear pitch circle diameter d is smaller, but the accuracy level of influence on the result of the design is not very obvious. When the precision grade from grade7up to grade6, d values decrease about10%or so. 5. With the increase of lubricant viscosity η, the small gear pitch circle diameter d monotony decline. Especially when the viscosity η<0.15(Pa·s), d sharply decreases with the increase of η. Since then, the d value decreases very slowly. Therefore, under certain conditions, devotion to use high viscosity of lubricant, can achieve the effect of the wasted effort.The innovation of this paper is developing a computer program and establishing a man-machine conversation interface. If the basic parameters of gears are known, Strength design, lubrication design and tribology design can be completed by using this program within seconds. The shortcomings is that the tooth surface roughness effect and tooth surface transient thermal effect are ignored when the lubrication design model is built, so the practicality of lubrication design model is effected. Beside, at low speed, the gear size calculated by this model is bigger, leading to increase the cost. It is further to account whether the cost is far less than the benefits of gear extending-life.