Improving the Performance of Luna Moped By Using Continuously Variable Transmission System

Transcription

1 Improving the Performance of Luna Moped By Using Continuously Variable Transmission System Mr. Chandan Raval Department of Mechanical Engineering Abstract Our first target to create new vehicle is the less fuel an engine consumes, more comfortable riding, more safety, less friction between its components in vehicle, more efficient vehicle and the fewer pollutants produces, so human can breathe clean air with comfortable driving. In today s world, Luna moped is obsolete because of its less power producing, less load caring capacity, less maximum to minimum speed range. To achieve gain in these areas, we have to challenge the conventional thinking associated with power train functions & design of it. Luna mopped uses 59.57cc engine with power train as centrifugal clutch for increase speed of vehicle, which is limited in range. Energy of Luna transmission is consumed in transmission system. This will allow the engine to operate at or near to its best break specific fuel consumption rate, which means the engine fuel economy and its performance will improve. For Luna cvt works like turbocharger or speed booster, provides infinite gear ratio. So, we can keep acceleration some different - different level and then applying cvt system which provides different - different speed output at same acceleration level. Keywords - Luna moped; continuous variable transmission (CVT); Mechanical linkages; Statics performance; Modeling of system; Testing of system. I. Introduction Energy supply and pollution emissions have become major issues because of the prevalence of automotive transportation, leading to forecasts of oil shortages and price increases. The use of Internal Combustion Engines (ICE) in transportation also increases pollution emissions, which must be prevented to sustain the quality and viability of life on Earth. To achieve better fuel economy and lower emissions, a great deal of research had been conducted on improving the efficiency of the power train, developing other energy sources, and shifting from the concept of conventional power train vehicles to Electric Vehicles (EV), Hybrid Electric Vehicles (HEV), and Fuel Cell Electric Vehicles (FCEV). To improve the efficiency of the power train, manual or automatic multilevel transmissions and CVTs have been developed to satisfy vehicle performance requirements and to improve ICE efficiencies. CVT is different from Manual Transmission (MT) and Automatic Transmission (AT) in that it offers a continuously variable gear ratio between desired limits without shift shock, allowing the power source to operate in its high efficiency region. New developments in gear reduction and manufacturing have led to ever-more-robust CVTs, which in turn allows them to be used in more diverse automotive applications. CVTs are also being developed in conjunction with hybrid electric vehicles. As CVT development continues, costs will be reduced further and performance will continue to increase, which in turn makes further development and application of CVT technology desirable. AIM: To analyze the performance of the Automatic Transmission and the CVT for a vehicle less than 80cc engine like Luna moped. To compare the Automatic Transmission and CVT Transmission In form of speed variation. To study the possibility using CVT for a Luna under 80cc engine. Good Performance as acceleration capability. Provide Easy driving as an automatic driving. SCOPE:

2 Providing Smooth Acceleration. Facilitating Powerful Driving Performance. Providing Better Transmission Efficiency and Torque Capacity. Reducing Amount of Slippage which occurs in most of the belt. To improve durability. To improve drive ability. A. Working of CVT The two variable pulleys are made up of tapered discs. The radius of the pulleys can be changed by changing the clearance between the discs. As the pulley changes their radius relative to one another they create infinite number of gear ratios between minimum to maximum and everything in between. ω 1 = input shaft angular velocity ω 0 = output shaft angular velocity Figure 1: CVT system In a chain CVT system, the plates and rocker pins, as depicted in Fig. 2b, transmit tractive power from the driver pulley to the driven pulley. Unlike a belt CVT, the contact forces between the chain and the pulleys are discretely distributed in a chain CVT drive. This leads to impacts as the chain links enter and leave the pulley groove. Hence, excitation mechanisms exist, which are strongly connected to the polygonal action of chain links. This causes vibrations in the entire chain CVT system, which further affects its dynamic performance. Both belt and chain CVT systems fall into the category of friction-limited drives as their dynamic performance and torque capacity rely significantly on the friction characteristic of the contact patch between the belt/chain and the pulley. B. Types of CVT Pulley Based CVT: In this most common CVT system, there are two V-belt pulleys that are split perpendicular to their axes of rotation, with a V-belt running between them. Toroidal CVT: Toroidal cvt are made up of discs and rollers that transmit power between the discs. There are two type half and full Toroidal. Hydrostatic CVT: Hydrostatic transmissions use a variable displacement pump and a hydraulic motor. All power is transmitted by hydraulic fluid. Infinitely Variable Transmission: A subset of CVT designs are called infinitely variable transmissions (IVT or cvts), Somehow same as cvt. Cone Cvt: A cone CVT varies the effective gear ratio using one or more conical rollers. Figure 2: pulley type CVT system

3 C. Background And Brief History Leonardo de vinci sketched his idea of CVT in the year 1490.In automotive applications; the history of CVTs has begun in the early era of car development, and certainly in the same period of conventional automatics. In early 1930s, General Motors had developed a fully Toroidal CVT and conducted extensive testing before eventually deciding to implement a conventional stepped-gear automatic due to cost concerns. General motor Research reworked on CVTs in the 1960s, but none ever saw their production. British manufacturer Austin used a CVT for several years in one of its smaller cars, but it was dropped due to its high cost, poor reliability, and inadequate torque transmission. Many CVTs in the early stage used a simple rubber band and come system, like the one developed by a Dutch firm, Daf, in However, the Daf s CVT could only handle a 0.6L engine, and severe problem with noise and rough stars eventually to hurt its reputation. The electron mechanical CVT based on metal belt is not yet available in the market, but in early 90 s electromechanical CVT based on dryhybird rubber belt has been applied for motor cycle. Now, almost all CVTs in the market use the van Doorne Company s steel push belt as the transmission element. This steel pushing belt was first introduced in D. Advantages and Benefits The clunking sound of a shifting transmission is familiar to all drivers. By contrast, a CVT is perfectly smooth and naturally changes its ratio discretely such that the driver or passenger feels only steady acceleration. Theoretically, a CVT would cause less engine fatigue and would produce a more reliable transmission, as the harshness of shifts and discrete gears force the engine to run at a less than optimal speed [20]. CVTs offer improved efficiency and performance. Table I shows the power efficiency of a typical five speeds automatic, which is the percentage of engine power transmitted through the transmission. This yields an average efficiency of 86%, compared with typical manual transmission with 97% efficiency [21]. By comparison, Table II shows the efficiency range for several CVT designs. Table 1: Efficiency versus gear ratio for automatic transmission Table 2: Efficiency of various CVT designs

4 These CVTs offer improved efficiency over conventional automatic transmission, and their efficiency depends less on driving habit than manual transmission. Since CVT allows an engine to run at its most efficient point virtually independent of the vehicle speed, a CVT equipped vehicle yields fuel economy benefits when compared with a conventional transmission. Testing by ZF Getrie is GmbH for U.S. Environmental Protection Agency City and Highway Cycles several years ago found that the CVT uses at least 10% less fuel than a 4 speed automatic transmission. The CVT was more than one second faster in 0~100Km/h acceleration tests than that of manual transmission. E. Challenges and Limitations The progress in CVT development has been slowly for a variety of reasons, with much of the delay in its development can be attributed to the lack of demand, while the conventional manual and automatic transmission have long offered sufficient performance and fuel economy. In addition, this problem is also possibly influenced by unsuccessful efforts to develop a CVT that can match the torque capacity, efficiency, size, weight, and manufacturing cost of step-ratio transmission. One of the major complaints with previous CVTs is the slippage in drive belt or rollers. This is caused by the lack of discrete gear teeth, which form a rigid mechanical connection between two gears; friction drivers are inherently prone to slip, especially at high torque. For many years, the simple solution to this problem has been by limiting the usage of CVTs only in cars with relatively low torque engine. Another solution is by employing a torque converter, but this reduces the CVT s efficiency. With the improvements in manufacturing technique, technology material processing, metallurgy, advance electronic control and advance engineering, CVTs can be applied in cars with high torque engine. In the need of a CVT to operate at the optimal transmission ratio at any speed, the selection of the ratio has to be addressed. Manual transmissions have manual controls, where the desired gear ratio totally depends on the driver to shift it and automatic transmissions have relatively simple shifting algorithms between three to five gears. However, CVTs require a more complex algorithm to accommodate an infinite division of speed and transmission ratios. II. Literature Review C. Zhu, H. Liu, J. Tian, Q. Xiao and X. Du [3] Specification of the experimental setup for testing CVT Mass of flyweight 63.5 g, Number of flyweight 3, Wedge angle of driving pulley 28, Wedge angle of driven pulley 30, Wedge angle of the belt 30, Length of the belt 1207 mm, Belt length density 0.58 kg/m, Angle of torque cam slot 36.5, Driving to driven axis distance 308 mm, Maximum speed ratio 3, Minimum speed ratio 1, Stiffness of primary spring 15.6 N/mm, Stiffness of secondary spring 7.58 N/mm, Minimum diameter of drive pulley 90 mm, Maximum diameter of driven pulley 270 mm, Torque cam gyration radius 44.5 mm. Different type of losses are coming with using rubber belt as CVT transmission system. The power loss of the CVTs includes the torque loss and the speed loss. The torque loss of the rubber V-belt drives resulted mainly from hysteresis losses in the materials when the belt was bent on and off the pulleys and the radial sliding losses as the belt is continuously wedged into and out of the pulleys. Power loss will be around 10%, torque loss around 75% & speed loss around 15%. Figure 3: efficiency vs. engine speed -40 Nm,--30 Nm, -*-20 Nm.

5 H. Zheng, W. S. Lim* and S. W. Cha [2] The simulation program developed in the previous part provides a range of results that can be used to validate the program. The results are obtained when the CVT output torque Tq and the throttle position are fixed. As shown in graph as spring constant increase CVT efficiency improve but it reduced with shelve angle increases. Figure 4: efficiency vs. spring constant Figure 5: efficiency vs. pulley angle As shown in graph as spring constant increase from 1840N/m to 1880 N/m CVT efficiency improve from 86-90% but it reduced with shelve angle increases from As shown in graph as mass of roller increase CVT efficiency reduced & as mass of roller is high the speed of driver pulley will be low. As shown in graph different the points illustrated in figure are operating points of the power source, and the speed of the power source is greater for smaller CVT. Figure 6: efficiency vs..roller weight Figure 7: pulley speed vs. mass of roller Da Wen Ge, Sugeng Ariyono And Daw Thet Thet Mon [4 ] The current paper reviews the state-ofthe-art research on control of friction-limited continuously variable transmissions. As CVT development continues, costs will be reduced further and the performance will continue to improve,

6 which in turn make further development and application of the CVT technology desirable. Hence, excitation mechanisms exist, which are strongly connected to the polygonal action of chain links. This causes vibrations in the entire chain CVT system, which further affects its dynamic performance. Both belt and chain CVT systems fall into the category of friction-limited drives as their dynamic performance and torque capacity rely significantly on the friction characteristic of the contact patch between the belt/chain and the pulley. Table 3: Efficiency versus gear ratio for automatic transmission Table 4: Efficiency of various CVT designs The current paper not only addresses the state of the art research accomplished towards understanding CVT dynamics and control, but also hopefully highlights the challenges/directions for future research, which could foster better understanding and designing of such systems and their controllers. M. Anand Partheeban [9] Rather than selecting one of four or five gears, a CVT constantly changes its gear ratio to optimize engine efficiency with a perfectly smooth torque-speed curve. This improves both gas mileage and acceleration compared to traditional transmissions. The main aim of M.Anand is to develop a mechanical continuous variable Transmission system in four wheelers provides a good torque and transmission efficiency. The A typical automatic uses four or five such gears, while a manual normally employs five or six. The continuously variable transmission replaces discrete gear ratios with infinitely adjustable gearing through one of several basic CVT designs. Depending on the Adjustable Variable pulley diameter the speed reduction ratio varies. Table 5: Different diameter of pulley and speed ratio

7 A power split function is available for the CVT which expands the power capacity of the belt CVT. At low speeds, the belt only carries part of the input power. It is possible to shift the power flow in the system from the gear to the CVT unit in a continuous manner. R. Pfiffner*, L. Guzzella, C.H. Onder [11] As described earlier, the system starts on the stationary best efficiency curve G: Then the engine speed is quickly raised to approximately 3500 rpm by changing the gear ratio of the CVT as fast as possible, before the engine gets back on the best efficiency curve for stationary operation G at 1 s: Actually, it get son the quasi-static best efficiency curve O which coincide with G for engine speed values greater than 2800 rpm: After the system efficiency curve O for a relatively long time ð8:6 sþ before it leaves it again to return to the final stationary operating point on G: has reached O; it stays on this quasi-static best efficiency curve O for a relatively long time ð8:6 sþ before it leaves it again to return to the final stationary operating point on G. The optimal solution therefore consists of bringing the system to the O curve as fast as possible, and to keep the system on this curve as long as possible. Figure 8: Torque vs. Engine speed Compared to the best of the current approaches, the expected fuel economy improvements are in the range of 2.5% to 5% for the downsized and supercharged engine analyzed in this paper. Based on this optimal solution, a new simplified control strategy was derived which can realize almost the same fuel economy benefits, but with a substantially lower control complexity. It is shown that the well-known single track modified classical strategy can be adjusted such that it coincides with the simplified optimal control strategy. Sergio Lolly [8] A SAE publication entitled A Theoretical and Experimental Procedure for Design Optimization of CVT Belts by Sergio Lolly describes a theoretical and experimental method for designing CVT belts. In this paper Lolly develops equations that determine the stress within the belt and provides a method for determining the tensile forces seen within the belt. Lolly uses a method of finite element modelling to determine stresses and uses this information to predict the lifespan of a CVT belt. As shown the difference in system of conventional and CVT based. They discuss the CVT s various advantages and disadvantages, and help to determine the overall CVT efficiency at different operating speeds and loading conditions. In this paper they discuss the design of a manual transmission to be used with a Salisbury style CVT. This particular CVT works in the same way as the Team Industries CVT. The difference is in the operation of the flyweights in the primary pulley.

8 Belt CVT Toroidal CVT Metal v belt Dry hybrid Chain Half Full Transmission Torque,Nm or less Starting Device Yes Yes Yes Yes No Engine Applied 2.5L or less 1L or less 2L 3.5L 5.5L Feature Less slip No hydraulics Long life Speed ratio control Torque control Operated By M/H/E E/H/M H/E H/E H Table 6: Compression of CVT III. Conclusions Today, only a handful of cars worldwide make use of CVTs, but the applications and benefits of continuously variable transmissions can be increased based on today s research and development. As automakers continue to develop CVTs, more and more vehicle lines will begin to use them. The usage of CVT in the automobile makes the transmission easier in operation as it has an advantage that it has fewer number of gear arrangement. The vehicle acceleration simulation displays that the CVT can provide a continuously variable ratio change and thus a smooth and continuous acceleration change. It is more comfortable for the driver and the passengers to ride a vehicle equipped with a CVT. The simulation of the vehicle acceleration performance presents that both the driveability and the fuel economy for the vehicle with a CVT are better than the one with a standard or a multi-ratio automatic transmission. A power split function is available for the CVT which expands the power capacity of the belt CVT. At low speeds, the belt only carries part of the input power. It is possible to shift the power flow in the system from the gear to the CVT unit in a continuous manner. Increased sales will prompt further development and implementation, and the cycle will be repeated infinitum. Moreover, increasing development will foster competition among manufacturers automakers from Japan, Europe, and the U.S. are already either using or developing CVTs which will in turn lower manufacturing costs. Any technology with inherent benefits will eventually reach fruition; the CVT has only just begun to blossom. References 1. Allen, Mark and LeMaster, Robert. A Hybrid Transmission for SAE Mini Baja Vehicles. SAE Publication C. H. ZHENG, W. S. LIM and S. W. CHA Performance Optimization Of CVT For Two-wheeled Vehicles International Journal of Automotive Technology 16 November C. ZHU, H. LIU*, J. TIAN, Q. XIAO and X. DU Experimental Investigation on the Efficiency Of The Pulleydrive CVT International Journal of Automotive Technology 30 May Da Wen Ge, Sugeng Ariyono and Daw Thet Thet Mon A Review On Continuously Variable Transmissions Control N.C.M.E. IN Malaysia MAY 2010.

9 5. Kluger, Michael A. and Long, Denis M. An Overview of Current Automatic, Manual and Continuously Variable Transmission Efficiencies and Their Projected Future Improvement. SAE Publication Lingyuan kong, robert G. Parker Steady Mechanics Of Layered, Multi-band Belt Drives Used In Continuously Variable Transmissions SCIENCE DIRECT PUBLICATION 6 April Lolli, Sergio. A Theoretical and Experimental Procedure for Design Optimization of CVT Belts. SAE Publication M. Anand partheeban Design and Fabrication of Continuous Variable Transmission in Four Wheelers SAE publication December, Mabie, Hamilton H. and Charles F. Reinholtz. Mechanism and Dynamics of Machinery, Fourth Edition. New York: John Wiley and Sons, R. Pfiffner, L. Guzzella, C.H. Onder Fuel-optimal Control of CVT Power Trains science direct publication 18 January XChristopher Ryan Willis A Kinematic Analysis and Design of a Continuously Variable Transmission 19 January 2006 Blacksburg, VA. 12. Z.John h. Gibbs Actuated Continuously Variable Transmission For Small Vehicles a thesis presented to the graduate faculty of the university of akron may, 2009