Abstract
Wet clutch is a widely used machine element in the agricultural machines be-cause it allows the transmission of high torque with a more user-friendly turn on/off. In this article, the control of a wet clutch pack using a proportional valve in the power take-off unit is investigated. A wet clutch package is implemented on the transmission direct PTO shaft and actuate the power take-off unit of an ag-ricultural tractor. A one-dimensional mathematical model of the wet clutch and the electro-hydraulic control system was developed. Several actuation cases were simulated, and responses of all circuit elements were evaluated. Based on these predictions, test procedures with out-put torque values 300 and 600 N-m were set at 1.900 rpm unloaded engine speed. Variables, including speed, pres-sure, and temperature, were recorded in the experiments. The test and simulation results were compared. The clutch pressure increase was 10% under-predicted while the mainline pressure drop was 1% over-predicted. The proposed 1-D model can be further improved indeed. Yet, the acceptable agreement between the model and tests, offer less costly trial-and-error in the design and tune-up of future systems.
Highlights
Background and ObjectivesWet clutches are being used more than ever in highway, agricultural, and construction vehicles as well as mining machinery, marine power and maneuvering systems, textile and packaging machines, presses, machine tools, and other production machines to transfer power and torque
Input and output shaft velocities, clutch and mainline pressures, piston force, displacement, speed and acceleration, centrifugal force on the piston, spring force on the clutch, stiffness and damping coefficients, Coulomb friction coefficient, the fluid flow and pressure changes at the proportional valve ports are predicted as functions of time
The control of a wet clutch pack using a proportional valve in the power take-off unit of an agricultural tractor is investigated
Summary
Background and ObjectivesWet clutches are being used more than ever in highway, agricultural, and construction vehicles as well as mining machinery, marine power and maneuvering systems, textile and packaging machines, presses, machine tools, and other production machines to transfer power and torque. Due to its high torque carrying capacity and ease of use, wet clutches are preferred in tractor tail shafts in recent years to power auxiliary equipment. When wet clutches are compared to dry clutches, their dimensions, torque carrying capacities, heat removal, and temperature control make their functional lifetime much longer [2]. Their functioning is influenced by variables such as the load, transmission fluid temperature, engine torque, and power. To use an electro-hydraulic proportional valve and to maintain the pressure constant behind the valve, the pressure relief valves must work in harmony. If the specified variables are ignored, the friction elements in the clutch, such as the friction discs, wear out quickly due to sliding friction, reduce the life span and lead to failure in brief periods (Fig. 1)
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