Gear Optimization for Noise Reduction of EPB Actuator

Abstract

As the demand for passenger cars that are equipped with EPB(electric parking brake) system increases, the automotive parts companies have tried to develop the EPB on all vehicle. As the range of EPB application expands, customer demand for noise reduction during EPB operation also increases. In order to reduce the EPB operating noise, the optimum design of the EPB actuator two-step train gear was carried out. First of all, three gear design factors, such as pressure angle, helical angle, and gear type, were changed to verify the impact on EPB operation noise. As a result of this, the change of transmission error, contact ratio and specific speed were confirmed using KISSSOFT which is gear analysis program. Theoretically, the gear train which has small transmission error, large contact ratio, certain specific slide(-3~+3) is advantageous for noise reduction. As a result of the analysis, it was confirmed that the transmission error is reduced when the pressure angle is reduced, and the contact ratio increases when the helical angle is increased. Also, when the gear type is changed from spur gear to helical gear, transmission error is reduced and contact ratio is increased, which is the most advantageous for noise reduction. The actual sample was manufactured and evaluated in five combinations. The result of the evaluation confirmed that the sample with the reduced pressure angle was the best to reduce noise. It was expected that changing the gear type from spur to helical would be the most advantageous for noise reduction. However, if the shaft rigidity is not strong enough to support thrust which is occurred by gear type change, the load noise increased at the end of EPB operation. The gear optimization of EPB actuator showed the following: First, In the no-load section, it was found that noise reduction can be achieved by optimization of the main gear design factor. Second, in the load section, if the stiffness of the shaft is weak, the noise increases at the end of operation due to thrust. In the future, the EPB actuator will be designed using this gear optimization process to reduce the EPB operation noise.