An Experimental Study on the Very Slow Reduction of Torque in a Variable Capacity Type Fluid Coupling

A fluid coupling of variable capacity type can attain continuous change of rotational speed by changing the fluid capacity. It is widely used，but the flow characteristics and torque curve is not understood yet. In our experiment, the torque curve shows some unstableness. In some cases the transmitted torque is reduced very slowly for over 10 minutes. In other cases the torque and rotational speed of output shaft becomes unsteady. We found that the length of partition plate affects the former instability by viewing the flow near the balance hole. The plate controls the flow quantity from the balance hole, and the fluid capacity in the coupling is changed by this flow. The flow behind the coupling affects the transmitted torque via this flow