Development of Plastic Gear for Power Transmission : Abnormal Wear on the Tooth Root and Tooth Fracture near Pitch Point

The Use of Cooling Holes to Decrease the Amount of Thermal Damage on a Plastic Gear Tooth

“…The highest temperature of the tooth surface is located near the pitch point region. In addition, the inner temperature was about 10°C lower than that of the tooth surface [4]. The heat generated in the plastic gears is a result of not only the frictional heat between the tooth surfaces but also of the heat caused by the hysteresis loss in the viscoelastic materials; it is, therefore, difficult to calculate the amount of the heat generated or the temperature distribution within the gear.…”

“…The temperature of the tooth surface was measured using a non-contact type temperature sensor Fig. 1 (a) Heat source and temperature distribution [4] and (b) heat accumulation area Fig. 2 Gear heat transfer model [5,6] [9, 10].…”

“…This decrease in strength decreases the wear resistance of the material, and the plastic gear contact zones are worn down because of the high surface temperatures. Polyamide gears have poor thermal conductivities, because of which polyamides exhibit the highest tooth surface temperature at the center of the tooth, which results in mechanical degradation [4,10,22]. In this study, three types of plastic gears were manufactured, including a standard gear (Fig.…”

“…However, in terms of power transmission, they exhibit some weaknesses, such as insufficient load capacity, as well as poor heat resistance and heat sensitivity. Moreover, their mechanical strengths decrease with increases in the tooth temperature [2,3]; therefore, it is difficult to estimate their service lives [4,5]. Plastic gears are primarily used in non-lubricated conditions.…”

Overload and Lifetime Test of Machine Cut Polymer Gears

“…The failure at pitch circle occurs when the strength of teeth decreases because of loosening material triggered by the high temperature. A study found that the fracture of teeth generally occurs near the pitch circle that is caused by abnormal wear [7]. This type of failure takes place typically in case of unlubricated gears [8].…”