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Dynamic Analysis of a Valve Train System, Used in a Four Stroke Engine

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Dynamic Analysis of a Valve Train System, Used in a Four Stroke Engine Faculdade de Engenharia da Universidade do Porto Dynamic Analysis of a valve train system, used in a four stroke engine João António dos Reis Nogueira Working version Dissertation of MIEM Dissertation for a Master’s Degree in Mechanical Engineering Supervisor: Professor Doutor Jorge H. Seabra Second Supervisor: Eng. César Ferreira July 2014 c João António dos Reis, 2014 Dynamic Analysis of a valve train system, used in a four stroke engine João António dos Reis Nogueira Dissertation for a Master’s Degree in Mechanical Engineering [email protected] DEMec - Department of Mechanical Engineering CETRIB - Section of Vibrations, Tribology and Industrial Maintenance Faculdade de Engenharia da Universidade do Porto Porto, Portugal Abstract The internal combustion engine (ICE) plays an important role in our society and much work is done into improving it’s efficiency, power output and reliability. In the motorcycle world, two types of engine are being used: the two-stroke and the four-stroke engines. The latter requires the use of an auxiliary system to control the opening and closing of the valves - the valve train. Traditionally, the valve train uses eccentric lobes to actuate rocker arms that open the intake and exhaust valves while the closing of the valves is done by the force of springs which are compressed during the opening of the valves. The portuguese motorcycle manufacturer AJP Motos SA developed a new valve train - InnerCam - that promises the reliability and stability of more complex systems while retaining the smaller size and low gravity center of some simpler, yet less reliable, systems. Previously analysis work led to functioning prototypes that reveal the grand potential of the system. However, these tests also revealed an unidentified issue that caused a power loss in a small range of engine speeds. A new kinetic and dynamic analysis, as well as a vibration analysis on the system, are needed in order to identify the source of the power loss, mentioned above, that required to model the real mechanism into simpler systems that allow an easier approach and an expedite analysis without compromising the accuracy of the results. This work revealed that the profiles for the valve displacement, velocity and ac- celeration are similar to the theoretical profiles required for the good engine op- eration, which helps to validate the InnerCam concept as a valid system with commercializing potential. The dynamic analysis performed also showed that the engine’s acceleration isn’t an influence to the system’s dynamic balance, neither is the variable point of contact between the rollers and the cam path. However, this variation in the point of contact implies very sharp changes in rotational speed and direction, which may increase the rate of wear of these components’ surfaces. The vibration analysis was performed on the exhaust sub-system and it revealed that the resonance frequency of this system is well above the range of excitation frequencies that the system supports (from 2000 to 12000 rpm). This rules out resonance issues, such as the source of the power loss that was previously described. i ii Resumo O motor de combustão interna (ICE) desempenha um papel importante na nossa sociedade e bastante trabalho tem sido feito para melhorar a sua eficiência, potên- cia e durabilidade. No mundo do motociclismo, são utilizados dois tipos de motor: motores a dois tempos e motores a quatro tempos. Este último requer o uso de um sistema auxiliar para controlar a abertura e fecho das válvulas - o trem de válvulas. Tradicionalmente, o trem de válvula usa lóbulos excêntricos para acionar os braços que abrem as válvulas de admissão e de escape, enquanto o fecho das válvulas é feito pela força das molas que são comprimidas durante a abertura das válvulas. O fabricante de motos português AJP Motos SA desenvolveu um novo trem de válvulas - InnerCam - que promete a durabilidade e estabilidade dos sistemas mais complexos, mantendo as pequenas dimensões e baixo centro de gravidade de alguns sistemas mais simples, mas menos fiáveis. O trabalho de análise anterior levou a protótipos que revelam o grande potencial do sistema em funcionamento. No entanto, estes testes também revelaram uma perda de potência anormal numa pequena gama de velocidades do motor. Uma nova análise cinemática e dinâmica, bem como a análise de vibrações sobre o sistema, foi necessária, no sentido de tentar explicar a perda de potência. Isto exigiu modelar o sistema em sistemas mais simples, que permitiram uma aproximação mais fácil e uma análise expedita sem comprometer a precisão dos resultados. Este trabalho revelou que os perfis de deslocamento, velocidade e aceleração são semelhantes aos perfis teóricos necessários para o bom funcionamento do motor, o que ajuda a validar o conceito InnerCam como um sistema pertinente com po- tencial de comercialização. A análise dinâmica também mostrou que a aceleração do motor não influencia o equilíbrio dinâmico do sistema, nem o ponto de contato variável entre os pinos rolantes e a came. No entanto, esta variação no ponto de contacto implica mudanças muito agressivas na velocidade de rotação e sentido de rotação, que podem acelerar o desgaste das superfícies destes componentes. A análise de vibrações foi realizada para o sub-sistema de escape e revelou que a frequência de ressonância deste sistema está situada bem acima da gama de frequências de excitação que o sistema tem de suportar (2000-12000 rpm). Isto elimina os problemas de ressonância, como a fonte de perda de energia descrita anteriormente. iii iv Acknowledgements I would like to acknowledge and express my sincere gratitude to some people without whom I wouldn’t be able to present this thesis or even finish the master’s degree. First of all, I thank my parents, Antero e Isabel, for all the trust and continued support. I stand where I am thanks to them. Secondly, I’d like to acknowledge my entire family, specially my uncle António, as well as Frederica Oliveira, for all the help and support for this thesis. Thirdly, I’d like to express my greatest gratitude to the Prof. Jorge Seabra, Prof. José Dias Rodrigues and Eng. César Ferreira, that provided me the tools, guidance and patience for this thesis to be done. For this, I also thank all the staff at CETRIB who warmly welcomed as one of them. Fourthly, I’d like to acknowledge and thank Pedro Noronha, Carlos Vieira, Diogo Moura, Mário Oliveira,Pedro Soares, Eduardo Moreira, João Mata, Salvador Costa, Ana Ribeiro, Ana Oliveira, Susana Costa, Raquel Camacho, Samuel Pinho, Daniel Laranjinha, Luísa Vieira, Hugo Carvalho, Daniel Freitas, Guaicaipuro Neves, Ri- cardo Martins, Marta Rolo, Leonor Madureira, Carlos Oliveira, Joana Coutinho, Marta Conceição, Inês Mesquita, Luísa Louro and all my friends who accompanied me to this day. You may never know how much you’ve helped me get here, but nevertheless, thank you. Finally, I would like to thank AJP Motos SA for their collaboration and assistance for this thesis, as well as Faculdade de Engenharia da Universidade do Porto and all their staff for their contribution to this work. João Nogueira v vi “Opportunity is missed by most people because it is dressed in overalls and looks like work.” Thomas A. Edison vii viii Contents 1Introduction 1 1.1 DissertationOutline .......................... 3 2TheengineforthePR5 5 2.1 Technical information about the engine . 8 2.2 ValveTrains............................... 8 2.2.1 Stateoftheart......................... 10 2.2.2 Typical kinematic profiles for valve trains . 21 3InnerCam 25 4DynamicAnalysis 33 4.1 Exhaustsub-system .......................... 34 4.1.1 Geometric Properties . 36 4.1.2 Kinematics ........................... 37 4.1.3 Dynamics ............................ 43 4.2 Intakesub-system ........................... 53 4.2.1 Geometric properties . 55 4.2.2 Kinematics ........................... 55 4.2.3 Dynamics ............................ 56 4.3 ModelResults.............................. 58 4.3.1 ExhaustSub-system . 63 4.3.2 IntakeSub-system ....................... 71 4.4 Influence of engine acceleration in the valve train dynamics . 81 4.5 Influence of variable point of contact between the cam and roller . 88 5VibrationAnalysis 93 6ConclusionsandFutureWork 99 6.1 Conclusions............................... 99 6.2 FutureWork .............................. 101 References 103 ABenchmarkingtestes 105 ix x CONTENTS BSteel’stechnicalsheet 109 CThermaltreatmentappliedtoInnerCamcomponents 111 List of Figures 2.1 4 stroke engine diagram, with separated strokes [5]......... 6 2.2 4 stroke engine diagram, with separated strokes[2]......... 7 2.3 Technical information of the standard engine [8].......... 9 2.4 Example of a Single Overhead Valve system [9]........... 12 2.5 An example of a Double Overhead Cam valve train [11]...... 13 2.6 Honda Unicam engine. It’s possible to see that only one camshaft, with two cam lobes, is used. [12]................... 13 2.7 Two valve side engine example [2]. 14 2.8 Example of a Four-Valve Pent-Roof Cylinder Head. [13]...... 16 2.9 Desmodromic valve train used in Ducati motorcycles [14]..... 17 2.10 Example of a sleeve valve system [15]. 19 2.11 Theoretical lift profile, velocities and accelerations of the valves. In the dotted lines, it shows the common real kinematic behaviour instead of the theoretical behaviour. [7]............... 23 3.1 Innercam valve train - schematic representation (springs are not represented). 27 3.2 InnercamCamshaft. .......................... 28 3.3 Innercam camshaft’s cam paths. The inner path (dotted lines) cor- respondstotheexhaustsub-system. 29 3.4 Rockerarm-schematicrendering. 30 3.5 Lift profiles measured through valve timing by AJP Motos SA . 31 4.1 Exhaust sub-system schematics - position for non-actuated rocker arm ................................... 34 4.2 Exhaust sub-system schematics - position for actuated rocker arm 35 4.3 ( )-DiscretevaluesgivenbyAJPMotosSA . 37 4.4 Process of calculating the angle ................... 42 4.5 Freebodydiagramofthecamshaft . 45 4.6 Freebodydiagramoftheexhaustrockerarm . 46 4.7 Freebodydiagramoftheexhaustvalve . 48 4.8 Free body diagram of the exhaust cam follower / roller . 49 4.9 Freebodydiagramoftheexhaustsub-system .
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