Experimental Study of Comfortableness during Hydrodynamic Torque Converter Lockup in a Construction Machinery

Abstract

The comfortableness during hydrodynamic torque converter lockup in a construction machinery is investigated in this study. A motor grader is chosen as a typical construction machinery. Standard ramps are used to simulate stable working load. It is found that at conditions of flat road, the hydrodynamic torque converter locks at coupling condition, resulting in small acceleration fluctuation, little vibration dose value (VDV), and comfortable process. At ramp conditions, the hydrodynamic torque converter uses a traditional lockup strategy, which is possible to extend lockup status to higher load range. However, before the lockup process, the speed and torque differences between impeller and turbine wheels are larger. During the lockup process, the large speed difference leads to high engine inertia energy releasing rate. The large torque difference leads to high demanded engine torque change, which extends the engine adjustment ability and causes torque fluctuation. With a joint effect, three obvious acceleration fluctuations are observed, the VDVs become larger, and the lockup process becomes uncomfortable. As load increases, the comfortableness intends to get worse.