Development of Hydraulic-Electric Hybrid Car - Example

Development hydraulic-electric hybrid car: (Authors’ Name) (Institutional Affiliation) Environmental Studies (Lecturer) May 31, 2013 Development of hydraulic-electric hybrid car Executive Summary Purpose The aim of this project is to develop the first world’s hydraulic-electric hybrid car. Design Problem Electric cars incur excessive inefficiency under weighty loading since both batteries and motors gets less efficient due to high current utilization. The aim of Cafe85 hydraulic-electric hybrid is thus to accelerate the car at low speeds by the use of hydraulic power, hence minimizing the weight on the electric driveline in the moments when the largest power amounts are required. Customer Requirements Upon conducting interviews with the car manufacturers, car owners, observation of potential users and actual users as well as the potential users, our team was able to establish the requirements of the customers for Cafe85 hydraulic-electric hybrid car. Table A illustrates a full list of customer requirements, together with detailed description of each requirement. Table A: Customer Requirements Customer Requirements Objectives Comfortable feel in the course of acceleration Natural feel and smooth acceleration for the driver Plumbing efficiency Reduced frictional loses through evading redundant bends satisfactory top speed acceleration Hydraulic motor can accelerate a car to 27M/H Reliable components There should be no failure on components Lightweight The components should be light as possibly could Safety Driving the car should be safe under normal circumstances Aesthetics The car should have a professional look as well as eye pleasing Ease of service All car components needs to be accessible Ease of use Feel and use of a common car needs to be familiar Car function maintained Load and passenger amounts should not be changed The priorities of the customer requirements were based on satisfactory top speed acceleration, aesthetics, and that the car retained the function. The Engineering Specifications Upon the establishment of customer requirements, the team was able to devise the engineering specifications required to accomplish the project. Table B illustrates the specifications that the team devised together with the target units and values that underpin them. Our target values are slightly changed from the previous model since we have established a better system understanding as well as the requirements required to attain the goals of our project. Table B Engineering Specifications The Specifications Units Target Value Ratio of gear from the pump and motor to the shaft drive n/a 7.9:1 Slow-fill pump flow rate L/s 0.04-0.05 Accumulator pressure of the high-side MPa 15-30 Pump side loading N 0 – 5 Motor side loading N 0 – 5 Gear’s material strengths Mpa 400 – 1000 Geometry fitting pressure loss % 0 – 20% Fluid working temperature K 275 – 325 Hydraulic fitting size mm 8 – 24 Layout (components space) M3 0.2 – 0.4 Compatible components Yes/No Yes The specifications for engineering were developed based on customer requirements interpretation. Also, various specifications which were established were done so in order for the product to stand a reasonable working chance. For instance two constraints were the all components space volume and the necessary material strength. The mentioned constraints have made us to emphasize on the design which occupies the least space and developed using materials or parts that can work with the desired loads. Quality Function Diagram Upon establishing the engineering specifications and requirements of the customer, the team was able to develop Quality Function Diagram (see Appendix A). To start with, the percentage weights of every customer requirements were worked out by comparing every requirement to one another. Thereafter, the correlation template or matrix was developed, illustrating the degree to which every specification affects the requirements of the customer. Subsequently, the team was able to establish which engineering specifications and customer requirements highly ranked for our product design. With regards to the requirements of customer; safety, retaining the function of the car, and project transferability were the three items which were ranked as the most important. Whereas the on the engineering specifications, the three most ranked items included; the components spaces, high-side accumulator pressure attainability, and gears’ material strengths (Society of Automotive Engineers of Japan, 2010). Concept Generation This part outlines process of concept generation. Because it is very critical for the concept design to fulfill all the requirements of the customer, the team has to develop a Function Analysis System Technique diagram (FAST) for our product design. The FAST structure assumes the major function of the product and divides it into meticulous sub-functions which are required for the description of the main function. The sub-functions would then be utilized as principles for developing the design concepts. The Function Analysis System Technique structure for our product design is illustrated in Figure 1. The team established that the major function of this product would be to improve electric car performance. Thus, it was divided into sub-functions such as assures safety, captures energy, assist launch, assures reliability, assures convenient, improve the product and please senses. Then the two subsequent columns outline the methods deployed to attain the goals indicated in sub-functions. For instance, car launched is supported by the hydraulic motor propelled by fluid discharged by the high-pressure accumulator (Fujinami, 2008). To ensure safety, the team could employ a pressure discharge value becoming a form of emergency switch and energy could be captured as high-pressure accumulator pressurized fluid by using slow-fill or brake pump. The remainder of the diagram could be interpreted in a similar method Relying on the FAST structure, three major parameters for the design was developed, and they include; box placement reduction, clutch selection and reduction type. A number of the parameters for the design from the FAST were excluded since they have been determined already. Moreover, the concept of regenerative braking would be reserved for future research and development. Every design parameter for the concept designs were established through brainstorming, reviewing the requirements of the customer from the QFD and taking some parts of the car’s major components for example suspension and transmission (reverse engineering). Concerning the reduction type, the team developed four concept designs: sprockets and chain, hub bike wheel, spur gear and pulleys and belts. All the reduction types operate in the same way, apart from the hub bike wheel that has one part clasped on the hydraulic motor, while the other side clasped on the spline shaft. Nonetheless, the hub bike wheel must be fitted as the front car wheel. The design would in overall remain the same for the hub bike wheel; however the motor and pump placement as well as the size of the accumulator would be different. Three possible options are available for 1-way clutch that satisfies the requirements of the customer. In essence, Concept 1 (the over-running clutch), and Concept 2 (1-way bearing) are quite the same, with the 1-way bearing being the simpler and cheaper. Concept 3 (Pawl and Ratchet) also locks 1-way and freely runs the other way. With regards to the box placement reduction, the team established three probable sites over the transmission. The First concept deploys an enlarged shaft mating with the transmission gear box shaft. For the Second concept, the existing transmission box would have the reduction box welded on it. The Third concept deploys rear axle being joined with the hydraulic motor. Morphological Chart This chart was developed to create high-degree concepts on the major design parameters of this product. Because the existing machines have hydraulic system already mounted on the electric car, our core design parameters are targeted at the reduction box design concept. Table C illustrates the project’s morphological chart. Table C The Morphological chart of the project Design Parameters Concept (one) Concept (two) Concept (three) Concept (four) Clutch Selection 1-way bearing Overrring Clutch Pawl and Ratchet Reduction Type Spur gears Hub bike wheel Sporockets and chain Pulleys and belt Placement Reduction Box Enlarged shaft Welded over the transmision Rear axle motor drive Source: (Bosch, 2011). Concept Evaluation With respect to clutch selection, the team settled on Concept 2 (1-Way bearing) due to its low price, manufacturability, and compact size. The selected bearing fulfills all the technical requirements of the design product for instance the maximum speed of (4000 RPM) and the maximum torque of (193 Nm). The reduction box is established to be fitted on the enlarged shaft mating with the transmission gear box shaft which is Concept 1. The Second concept for the placement of the reduction box requires sophisticated machining, something which cannot be feasible due to the time constraints coupled with limited access to machineries. The Third concept with regards to the reduction box poses potential setback linked to differential. As a result of the existing differential within the transmission system, torque could not be deployed directly to one of the rear axles. Detail Design Hydraulic drivetrains are capable of being used to efficiently and quickly release and store large energy amounts, thus rendering them attractive particularly for car applications, which comprise considerable amounts of go- and-stop driving (Bosch, 2011). The hydraulic car can use and capture huge portion of energy usually lost in car braking. The hydraulic hybrid technique can improve fuel or energy economy as well as performance in acceleration. The hydraulic system launch will keep energy through the hydraulic pump in the course of braking the car. Upon the inclusion of the hydraulic launch technology for car acceleration, there would be no burdening on the electric batteries in the course of acceleration and the general efficiency as well as range of the Cafe85 would be enhanced. In the course of acceleration, after passing on the hydraulic motor, the pressure of the hydraulic fluid is lost and is kept on the accumulator’s low-side as shown in the engineering drawing. When there is no usage of the hydraulics for the car acceleration, the high-side accumulators would be re-charged by the slow-fill pump. While the car is utilizing electric motor (during cruising) the valves get aligned in a manner that the fluid in circulating freely within the system with no flow via the motor or pump. As regards to the Design expo, a valve for emergency stop was connected directly at the high-end pressure accumulator terminals and the other high-pressure accumulator due to safety purposes for capped off. When the valve for emergency stop is engaged, it will prevent the accumulator (high-pressure) to discharge fluid. This could be applied when a leak happens when the accumulator if full. Figure 2: Engineering Diagram for High Pressure Accumulator Upon devising the engineering diagram for the hydraulic elements, the team feels that we have more efficiently utilized constraints and components of the system. Following the testing stage of the design, a couple of modifications were essential. Concerning safety, we made sure that the hydraulic engineering plan was installed properly to evade any broken fittings and lines. We also appended support cable clasps on the hydraulic fittings which incur high pressure to avoid these lines causing potential risk in case they broke. The other safety value to the Cafe85 was the check valve for the emergency stop for the accumulators of high pressure. When the knob of this valve is pressed it disallows accumulators (high pressure) for discharging pressure. This could be used when a line broke, stopping the release of any extra pressure on to the accumulators. Because this knob for emergency stop is situated within the cab of Cafe85 in order to allow the driver to push it without exiting the car. Conclusion and Recommendations We have successfully developed a hydraulic drive on the electric car. Whereas this fulfills the limited objective of this project, there is still more work to be done. Some of the future tasks include; the inclusion of the regenerative braking technique, the engineering design needs to be redesigned to increase efficiency and reduce pressure drops and advance measures needs to be undertaken to create the controls. In the design implementation a space has been left to allow mounting of the regenerative hydraulic pump, utilizing similar driveshaft which was mounted for acceleration. So as to attain this, the team recommends using another sprocket reduction from the regenerative motor to the driveshaft. As opposed to the drive we used, albeit 1-way bearing would not be suitable and a more complex mechanism for the clutch would be needed. References Fujinami, H. (2008). Front Line of Brake Control”, Journal of Society of Automotive Engineers of Japan (Dec. 2007) in Japanese. Noguchi, M. (2009).Trends and Future Views on Steering System Technology, Koyo Engineering Journal No. 159. Society of Automotive Engineers of Japan, Inc. (2010). Handbook of Society of Automotive Engineers of Japan (Mar. 2010) in Japanese. http://www.parker.com/ Bosch. (2011). Automotive Handbook 4th Edition. SAE. Appendix A Read More