Optimization of Clutch Pedal Vibration without Compromising the Overall Efficiency of the Clutch System 2021-28-0247
The clutch pedal in manual transmission plays a significant role in defining the comfort of driver as the component is one of the end user’s direct interface in the vehicle. Whenever driver operates the clutch pedal, comfort and NVH refinement should be felt over the complete pedal travel. The expectations of customer on NVH refinements, such as pedal vibration felt on foot during actuation, becomes the part of perceived quality and hence addressing the concern is very crucial. Due to advancements of technology and down-sizing of engines, NVH becomes the challenging area where the clutch pedal vibrations need to be eliminated to improve the comfort.
In this paper we are explaining the problem statement and NVH solution to eliminate the clutch pedal vibration observed during clutch pedal actuation. Pedal vibrations were very severe at 10% clutch pedal pressed condition, and the same tends to diminish till 50% clutch pedal pressed condition. From initial position (0% clutch pedal pressed condition) to 10% clutch pedal pressed condition and after 50% clutch pedal pressed condition, the vibrations are not felt. Through Fast Fourier transform (FFT) analysis of measured results, it is found that the peak-to-peak linear acceleration of this clutch pedal vibration was between 3 to 8 m/s2 in idle condition. Also, it is found that the vibrations are following 0.5 engine excitation order and its harmonics (Frequency: 6.67 Hz) at idle condition. Such Low frequency high amplitude vibration creates numbness on the foot.
Trials were conducted by varying the opening pressure and location of vibration cancellers on clutch high pressure pipe and by introducing flexible hoses of various stiffness and lengths and plastic pipes with various profiles in between the clutch high pressure pipe along with the foresaid dampers. While the higher opening pressure damper with the low stiffness rubber hose solves the pedal vibration concern, clutch system reserve in the total pedal travel got deteriorated thereby affecting the gear shifting quality of the system. This paper explains the effective method for finding optimal solution to resolve clutch pedal vibration concern without compromising the pedal travel and load efficiency of clutch system and significance of location of pedal vibration canceller in addressing the concern.