Division Mobile Working Machinery Prof. Dr.-Ing. Dr. h.c. K.-Th. Renius c/o Institute of Automotive Engineering Prof. Dr.-Ing. B. Heißing Technische Universität München Energy Optimized Pressure Controlled Clamping System for Continuously Variable Chain Transmissions Bernhard Stöckl (presented by Roland Mölle) 2004 International Continuously Variable and Hybrid Transmission Congress September 23-25, 2004
Stöckl 2004 Motivation: Increase of efficiency by reducing hydraulic losses Background: Frictional power transmission requires clamping force Clamping and ratio control of the converter via hydraulics (high forces and dynamics at small required space) Aim: Energy-saving hydraulic system (pressure controlled) for continuously variable transmission: Oil flow and pressure only on demand Introduction
Stöckl 2004 Constant Flow System (PIV Drives) Pressure by throttling a constant oil flow Torque sensors provide torque proportional pressure and act as pump in case of high torque gradients Pressure Controlled System (Van Doorne Transmissie) Fixed displacement pump sets pressure in secundary clamping cylinder via pressure relief valve Torque information delivered by electronic engine controller „Torque Fuse“ to avoid torque peaks New Pressure Controlled System (LTM/FTM) Oil flow and pressure only on demand Torque measured directly at shafts of transmission Pump function of torque sensors Existing Clamping Systems
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 New pressure controlled clamping hydraulics Md New torque sensor (Pilot operated) pressure control valve Electronic pressure controlled pump Clamping cylinder Pressure sensor n 22 n 11 n 12 n 21 Md p U p U p U Speed sensor Valve for venting CVT-controller for ratio and clamping pressure
Stöckl 2004 Hydraulic assembly at test rig Valve for opening venting circuit Pressure control valve From pump To tank Pressure sensor Hydraulic rotating union
Stöckl 2004 Chain converter transmission at test rig Clamping cylinder Speed transducer Chain Gear wheels
Stöckl 2004 Clamping cylinder Movable plate Speed transducer Cup spring Sensor plate “1” “2” Connection to pressure control valve Chain Tube for venting circuit Sensor chamber Ball ramps Speed Connection to tank while venting Variator design and venting circuit
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 Torque measurement: Gearwheels are seperated by ball ramp Torque causes twist of ball ramps until axial force (results from torque) is balanced by spring; twisting angle is detected by speed transducers Amount of torque is calculated from twisting angle Speed transducer “1” “2” Gearwheel Movable plate Sensor chamber Torque F spring F axial F hydraulic F spring Functions of ball ramps
Stöckl 2004 Speed transducer “1” “2” Gearwheel Movable plate Sensor chamber Torque F spring F axial F hydraulic F spring Torque measurement: Gearwheels are seperated by ball ramp Torque causes twist of ball ramps until axial force (results from torque) is balanced by spring; twisting angle is detected by speed transducers Amount of torque is calculated from twisting angle Functions of ball ramps
Stöckl 2004 Laboratory torque measurement shaft Torque sensor of the variator Measured torque by novel torque sensor compared to signal of measurement shaft
Stöckl 2004 Speed transducer “1” “2” Gearwheel Movable plate Sensor chamber Torque F spring F axial F hydraulic F spring Torque measurement: Gearwheels are seperated by ball ramp Torque causes twist of ball ramps until axial force (results from torque) is balanced by spring; twisting angle is detected by speed transducers Amount of torque is calculated from twisting angle Pump function: Movable plate pumps oil into system as soon as pressure is to low for a safe transmission of torque Functions of ball ramps
Stöckl 2004 Speed transducer “1” “2” Gearwheel Movable plate Sensor chamber Torque F spring F axial F hydraulic F spring Torque measurement: Gearwheels are seperated by ball ramp Torque causes twist of ball ramps until axial force (results from torque) is balanced by spring; twisting angle is detected by speed transducers Amount of torque is calculated from twisting angle Pump function: Movable plate pumps oil into system as soon as pressure is to low for a safe transmission of torque Functions of ball ramps
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl different oil supply systems for pressure controlled hydraulics: Constant pressure circuit (57 bar = const.) Controlled supply pressure (higher clamping pressure plus 10 bar) Optimised constant flow system (6 l/min) Comparison of hydraulic losses at characteristic operation points => Drive train management should tolerate a certain decrease of engine speed before changing transmission ratio
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 New European Drive Cycle (pass. car) Load, target ratio and speed measured at Autarkic Hybrid Target ratio by drive train management 91.7% less oil volume flow than former constant flow system (6 l/min) Savings of hydraulic power: 80.5% (constant pressure supplied, 70 bar) 86.3% (pressure controlled oil supply, p max +10bar) Vehicle speed Ratio
Stöckl 2004 FTP-72 (passenger car) Load, target ratio and speed measured at Autarkic Hybrid Target ratio by drive train management 93.9% less oil volume flow than former constant flow system (6 l/min) Savings of hydraulic power: 77.9% (constant pressure supplied, 70 bar) 89.4% (pressure controlled oil supply, p max +10bar) Vehicle speed Ratio
Stöckl 2004 Test cycles for tractors No standardised test cycles available for tractors Based on measurements during typical tractor works Average size of field in Bavaria: 1,5 ha ( kW tractor is common) Optimal ratio of length to width of field: 2:1 => length = 173 m Turn on headlands included (change of ratio) Drive train management sets target ratio
Stöckl 2004 Load control mode (drive train management) 96.7% less oil volume flow than former constant flow system (6 l/min) Savings of hydraulic power: 93.6% (constant pressure supplied, 70 bar) 95.8% (pressure controlled oil supply, p max +10bar) Chisel plowing cycle (tractor) Integrated oil flow Target ratio Simulated ratio Load Transmission output speed Measured speed (tractor) Target speed Simulated speed
Stöckl 2004 Engine speed 1050 rpm and higher (drive train management) 85.1% less oil volume flow than former constant flow system (6 l/min) Savings of hydraulic power: 35.7% (constant pressure supplied, 70 bar) 68.9% (pressure controlled oil supply, p max +10bar) Front end loading cycle (tractor) Load Measured speed Target speed Target ratio Integrated oil flow Simulated ratio Simulated speed Transmission output speed
Stöckl 2004 Pressure controlled clamping hydraulics Optimization of clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 Pressure p 2 at output shaft “Clamping force requirement“ for output pulley Over-clamping Former constant flow system (two torque sensors) Clamping pressure at constant flow system, M in =const Torque proportional clamping pressure by throttling a constant oil flow Torque sensors located at in- and output shaft Torque sensors in series => higher pressure sets basic pressure level Ratio controller increases one pressure to reach -ratio
Stöckl 2004 Pressure p 2 at output shaft “Clamping force requirement“ for output pulley Over-clamping Former constant flow system (two torque sensors) Optimized pressure controlled clamping system “Clamping force requirement“ for output pulley Minimum sensor pressure at output input (ball ramp equilibrium) Clamping pressure of constant flow and pressure controlled system, M in =const
Stöckl 2004 Optimized pressure controlled clamping system Both clamping pressures independently Novel torque sensors located at in- and output shaft “Clamping force requirement” must be known -ratio > 1 for ue > 1 => p input > p output Increase of hydraulic power savings from 80% to 83% (test cycle) “Clamping force requirement“ for output pulley Minimum sensor pressure at output input (ball ramp equilibrium) Savings Optimized clamping controller, pressure controlled system, M in =const
Stöckl 2004 Pressure controlled clamping hydraulics Optimized clamping pressure Novel torque sensor Energy consumption at specific operation points Test cycles Outline Conclusion
Stöckl 2004 Conclusion Hydraulic layout and design of chain converter was shown Novel torque sensor: torque measurement and safety function (pump function) Hydraulic power saving potential for different cycles up to 95.8% compared to constant flow system (6 l/min) Tractor test cycles were introduced Optimized clamping pressure for further increase of efficiency (3% for test cycle) was presented
Division Mobile Working Machinery Prof. Dr.-Ing. Dr. h.c. K.-Th. Renius c/o Institute of Automotive Engineering Prof. Dr.-Ing. B. Heißing Technische Universität München Energy Optimized Pressure Controlled Clamping System for Continuously Variable Chain Transmissions Bernhard Stöckl (presented by Roland Mölle) 2004 International Continuously Variable and Hybrid Transmission Congress September 23-25, 2004
Stöckl 2004