An Alternative Variable Valve Timing System for Heavy Duty Vehicles Daniel Olovsson Mikael Eriksson Civilingenjör, Maskinteknik 2016 Luleå tekniska universitet Institutionen för teknikvetenskap och matematik “The best or nothing at all.” – Gottlieb Daimler Abstract The ability to control engine valve timing has the potential to alter the engine performance over the entire operating range. The outcome of valve timing technology enables the possibility to increase efficiency, lowering emissions, increase engine torque, etc. One of the simplest ways to obtain a variable valve timing is to use cam phasers. The dynamics of a hydraulic cam phaser has been studied, three concepts with the purpose to control such an element has been developed using simulation driven product development. Focus have been on robustness, simplicity and implementation. A final concept using on/off solenoids to control a torque driven cam phaser has been designed and simulated in GT- SUITE which validated its performance and functionality. A dynamic model was built in Simulink which simulated the behaviour of the cam phaser and provided tools for optimizing the rotor design. By combining the knowledge of mechanical- and control engineering at Scania, the development process of such machine elements was effective. The outcome of this thesis has given a new perspective in understanding these components and their potentials. Preface This is a master thesis written by Mikael Eriksson and Daniel Olovsson which was conducted at Scania CV AB in Södertälje, Sweden during the first semester of 2016. The work was performed as a final course in Mechanical Engineering at Luleå University of Technology, with Pär Marklund as supervisor. Acknowledgement ‘Our deepest gratitude to our colleagues at Scania. Their guidance, optimism and genuine encouragement led to the success of this thesis. We would like to thank Pär Marklund, our supervisor at the university. To Henrik Flemmer and our supervisor Anders Larsson, thank you for giving us the opportunity to be a part of this journey.’ Contents ACRONYMS ............................................................................................ II LIST OF FIGURES ................................................................................ III NOMENCLATURE ............................................................................... VI 1 INTRODUCTION ............................................................................ 1 1.1 BACKGROUND ............................................................................................... 1 1.1.1 Variable Cam Phasing ........................................................................... 1 1.1.2 Problem Statement .................................................................................. 4 1.2 OBJECTIVE ..................................................................................................... 5 1.2.1 Oil Control Unit ..................................................................................... 5 1.2.2 Phase Angle Stability .............................................................................. 5 2 METHOD .......................................................................................... 6 2.1 NEED OF PRODUCT ...................................................................................... 7 2.1.1 Product Characteristics ............................................................................ 8 2.1.2 Product Specification ................................................................................ 9 2.2 DEVELOPMENT PROCEDURE ................................................................... 11 2.2.1 Oil Control Unit ................................................................................... 11 2.2.2 Phase Angle Stability ............................................................................ 11 2.2.3 Scope ..................................................................................................... 11 2.2.4 Limitation ............................................................................................. 12 2.3 MODELLING ................................................................................................ 13 2.3.1 Understanding GT-SUITE ................................................................. 14 3 RESULTS .......................................................................................... 15 3.1 OIL CONTROL UNIT ................................................................................... 15 3.2 DETAIL DESIGN .......................................................................................... 17 3.2.1 Cam Phaser Assembly .......................................................................... 17 3.2.2 Oil Supply and Lock-Pin...................................................................... 19 3.2.3 Operating Sequence Valve Unit ............................................................ 20 3.2.4 Cam Phaser Dimensioning .................................................................... 21 3.3 CONCEPT PERFORMANCE ......................................................................... 24 3.4 PHASE ANGLE STABILITY .......................................................................... 25 4 DISCUSSION ................................................................................... 27 4.1 CONCLUSION ............................................................................................... 29 4.2 FUTURE WORK ............................................................................................ 30 5 BIBLIOGRAPHY.............................................................................. 31 6 APPENDICES ................................................................................. 34 A DEVELOPMENT PROCESS .................................................. 6:1 B ALTERNATIVE OIL CONTROL CONCEPTS ................... 6:4 C 3D-MODEL ............................................................................. 6:8 D OIL CONTROL UNIT CONCEPT EVALUATION ............ 6:10 E PHASE ANGLE STABILITY CONCEPT EVALUATION .. 6:14 F CAM PHASER DYNAMICS .................................................. 6:16 G GT-MODELLING .................................................................. 6:23 H DESIGN SPACE ..................................................................... 6:26 I SIMULINK MODEL .............................................................. 6:29 J GT-MODEL ............................................................................ 6:30 Acronyms VCP - Variable Cam Phasing SI - Spark-Ignition NOx - Nitrogen Oxide VVT - Variable Valve Timing hVCP - Hydraulic Actuated Variable Cam Phasing OPA - Oil Pressure Actuated OCV - Oil Control Valve VFS - Variable Force Solenoid TD - Torque Driven GT - Gamma Technologies CAD - Computer Aided Design II List of Figures Figure 1.1. A typical hVCP unit. 2 Figure 1.2. The hVCP architecture. 2 Figure 1.3. A common lock-pin sequence. 3 Figure 1.4. Schematics of a torque driven hVCP. 4 Figure 1.5. hVCP instability due to lower engine speed, supply pressure and leakage. 5 Figure 2.1. Overlying simulation scheme. 13 Figure 2.2. Block-model schematic setup. 13 Figure 2.3. Example of a GT-model, a check valve. 14 Figure 3.1. Schematics of the final concept. 16 Figure 3.2. Exploded view cam phaser assembly. 17 Figure 3.3. Cylinder body exploded view. 18 Figure 3.4. Cylinder body assembled. 18 Figure 3.5. Control caps. 18 Figure 3.6. Control valve assembly. 18 Figure 3.7. Valve socket. 19 Figure 3.8. Inner rotor grooves. 19 Figure 3.9. Pressurized internal rotor lines. 19 Figure 3.10. The lock-pin and connected lines with grooves. 20 Figure 3.11. Cam phaser holding phase angle. 20 Figure 3.12. Valve unit holding phase angle. 20 Figure 3.13. Cam phaser negative phasing direction. 21 Figure 3.14. Valve unit negative phasing direction. 21 Figure 3.15. Cam phaser positive phasing direction. 21 Figure 3.16. Valve unit positive phasing direction. 21 III Figure 3.17. Amplitude gain with the boundaries. 22 Figure 3.18. Velocity gain with the boundaries. 22 Figure 3.19. Rotor width and vane height factor design space. 23 Figure 3.20. Cam phaser step-response of the final concept. 24 Figure 3.21. Simulated phasing speed map of the final concept. 24 Figure 3.22. Phase Angle error. 25 Figure 3.23. Level plot of the Bode diagram. 25 Figure 3.24. Level plot of the error growth rate. 26 Figure 3.25. Generated RMS-power as a function of valve flow. 26 Figure A.1. The workflow concept generation scheme. 6:1 Figure A.2. Method for generating product concepts. 6:2 Figure B.1. Single on/off concept scheme. 6:5 Figure B.2. Logical signal layout. 6:6 Figure B.3. Selectively, de-activating pilot check valves. 6:6 Figure B.4. Selectively limiting the check valve range. 6:7 Figure B.5. Active-passive operating sequence. 6:7 Figure C.1. 3D-model exploded view final koncept. 6:8 Figure C.2. Assembled 3D-model. 6:9 Figure D.1. Cam torque, energy and delay time 6:10 Figure D.2. Pilot delay setup. 6:10 Figure D.3. Remote spool valve (top) and pilot valve (bottom). 6:11 Figure D.4. Valve lift response. 6:11 Figure D.5. Passive element setup. 6:12 Figure D.6. Cam torque and position of mass. 6:12 Figure E.1. Worst case, high oil temp with low engine speed. 6:15 Figure F.1. Rotor parameters. 6:16 Figure F.2 Internal flow paths between the chambers. 6:17 Figure F.3. Internal leakage across a rotor vane. 6:18 Figure G.1. GT-model of the control system. 6:23 IV Figure G.2. GT-model of the solenoid. 6:24 Figure G.3. GT-model of hVCP coupled