An ISO standard tooth profile has a symmetric pressure angle of 20°. However, the load capacity can be increased with respect to bending and contact pressure by increasing the pressure angle on the meshing side of an asymmetric tooth. Accordingly, we analyzed the torque transmission capacity of asymmetric gears with various pressure angles. We calculated the deflection and bending stress of teeth by the finite element method and found the root stress taking into account the load-sharing ratio. Hertzian contact stress was calculated with respect to contact pressure. Normal vector load was converted into a torque, and torque capacity was evaluated when the stress reached the allowable stress for each case. Reduced bending stress because of an increase in tooth thickness and decreased transmission torque because of a reduction in the base circle radius work together to maximize the load capacity for bending at a pressure angle of around 30°. Maximum load capacity with respect to contact pressure is achieved when the pressure angle is made 45° by increasing the radius of the contact surface. Both strength with respect to bending and contact pressure are found, and the torque transmission capacity of the gear is determined by the lower value of the two. For low-strength materials such as flame-hardened steel, damage due to contact pressure is expected for all forms of gears and the greatest torque capacity was at a pressure angle of 45°. In the case of assuming 800 Hv and an inclusion size $$ \sqrt{\boldsymbol{A}}=50 $$  μm for a high-strength material, the greatest torque transmission capacity is obtained at a pressure angle of 30°. In the case of assuming a moderate-strength material such as case-hardened steel, an optimal form exists at which strength with respect to bending and strength with respect to contact pressure are equal.

中文翻译：

---

齿形不对称齿轮的负载能力评估

ISO标准齿廓的对称压力角为20°。但是，通过增大非对称齿的啮合侧的压力角，可以增加相对于弯曲和接触压力的负载能力。因此，我们分析了不同压力角下非对称齿轮的扭矩传递能力。我们通过有限元方法计算了牙齿的挠曲和弯曲应力，并找到了考虑到负载分担比的根应力。相对于接触压力计算赫兹接触应力。将法向矢量负载转换为扭矩，并在每种情况下应力达到允许应力时评估扭矩容量。由于齿厚增加而减小的弯曲应力，以及由于基圆半径减小而导致的传递扭矩减小，共同发挥了最大作用，以使压力角约为30°时弯曲的能力最大。当通过增加接触面的半径使压力角为45°时，可获得相对于接触压力的最大负载能力。找到了相对于弯曲和接触压力的强度，并且齿轮的扭矩传递能力由两者的较低值确定。对于诸如火焰硬化钢之类的低强度材料，所有形式的齿轮都可能因接触压力而损坏，并且最大扭矩容量为45°的压力角。对于高强度材料，假设为800 Hv且夹杂物尺寸$$ \ sqrt {\ boldsymbol {A}} = 50 $$μm，则在30°的压力角下可获得最大的扭矩传递能力。在假定诸如表面硬化钢的中等强度材料的情况下，存在最佳形式，在该最佳形式下，抗弯强度和相对于接触压力的强度相等。