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Researchers at the UC Davis HEV Center have developed a new design of a continuously variable transmission for use in all vehicle sizes. They have implemented this design by modifying a conventional pulley-type CVT both significantly increasing the efficiency and allowing for implementation in hybrid powertrains. The CVT is a pulley-type transmission in which a chain or belt is used to transmit torque from the input shaft to the output drive shaft. The hydraulically controlled pulleys allow for an infinite number of transmission ratios in a specified range, eliminating the need for discrete shifts. With drivability characteristics better than that of an automatic transmission and higher efficiency, the CVT is a considerable alternative. Modifications have been developed at UCDavis and Gear Chain Industries for conventional CVTs that increase the efficiency.

Test methods and data acquisition system specifications are described for measurements of the energy consumption of the control system of a servo-pump continuously variable transmission (CVT). Dynamic measurements of the power consumption of the servo-pump CVT control system show that the control system draws approximately 18.9 W-hrs of electrical energy over the HWFET cycle and 13.6 W-hrs over the 505 cycle. Sample results are presented of the dynamic power consumption of the servo-pump system under drive cycle conditions. Steady state measurements of the control power draw of the servo-pump CVT show a peak power consumption of 271 W, including lubrication power. The drive-cycle averaged and steady state energy consumption of the servo-pump CVT are compared to conventional CVT pump technologies.

The objective of this paper is to indicate the design principals of a Continuously Variable Transmission that is physically about the size of a conventional manual transmission for the same power and torque with an equal or better efficiency and durability. The CVT will be designed for use in either a hybrid electric drive or a conventional vehicle with the addition of a torque converter and reverse gear. The design objectives are as follows: 1. About the same size as a 5 or 6 speed manual transmission for North-South engine orientation and rear wheel drive. 2. About the same weight as the 5 or 6 speed manual transmission 3. Cost about the same or less 4. Much smaller than a comparable performance rated automatic transmission 5. Fewer parts than manual transmissions and less than 1/30th of the part count of an automatic. 6. Ratio span greater than equivalent manual or automatic transmissions. 7.

In an effort to improve the Continuously Variable Transmission and evaluate its performance with different modifications, a conventional CVT was redesigned to incorporate an energy efficient Servo Hydraulic Control (SHC) system and to substitute a different torque transmitting element, a Gear Chain Industry (GCI) chain for the Van Doorne Transmissie (VDT/Bosch) belt. Various loaded and unloaded tests were performed on the CVT while using the GCI Chain and VDT Belt in the Stock and Servo Hydraulic configuration. An analysis of the various configurations was made and key features of each element have been outlined.

The objective of the advanced transmission system concepts such as the Continuously Variable Transmission (CVT) and Hybrid Electric Drives is to improve fuel efficiency, lower emissions and reduce powertrain part count while not impacting cost. The control of the system, however, can greatly affect the final fuel consumption, performance and emissions for any of the possible configurations. This paper describes an engine control philosophy for a hybrid electric CVT powertrain concept with the fewest number of mechanical parts but with many modes of operation such as: 1. All electric operation 2. Regenerative braking to maintain the battery charge at a desired level. 3. Engine charge for maintaining the battery state of charge 4. Highway cruise efficiency. 5. Power enhancement by use of the electrical energy for passing and highway maneuvers. 6.

The standard vehicle propulsion system and its controls are compared with a flywheel propulsion system. Different concepts of control and various system configurations are explored. Some considerations for the design of a general purpose automatic flywheel transmission vehicle are presented and discussed. Specifications required for a flywheel transmission system which can achieve substantial mileage improvements and provide high performance are presented. The resulting vehicle would have performance of 0–60 mph in less than 10 seconds and achieve 50 miles per gallon on the Federal Urban Driving Cycle (FUDC) at an inertia weight of 3,000 lb. Higher mileages are possible for lighter vehicles. Fuel economy is achieved by (1) engine operation only at minimum BSFC, (2) elimination of engine idle, (3) recovery of energy from braking and (4) minimizing transmission losses.

The flywheel energy-storage unit is examined as a tool for engine load management. The control decision to store or retrieve energy is formulated and discussed. Vehicle dynamics are simulated on a digital computer in combination with dynamic programming techniques to obtain optimal operation policy. The simplified algorithm is explained, as well as the cost-function criteria and optimization constraints. The sensitivity of the optimal path and the vehicle gas-mileage improvements are elaborated. The study of losses indicates that the transmission is the largest energy sink in the power train. The result of this study provides an indication of the appropriate real-time control policy.

The Continuously Variable Transmission (CVT) concept has been available for many years. Reliability, durability, efficiency and controllability have been problems in the past. All but controllability have been greatly improved recently. This paper outlines the special control considerations necessary in CVT system design. Stressed is the concept of ideal engine operation and independent operation of engine and transmission control systems.

The design and evaluation of a control system for a continuously variable transmission (CVT) vehicle is presented in this paper. Studied and simulated are the following three topics: design and evaluation of the control system with a CVT vehicle in acceleration, deceleration and to the sensitivity of the system with respect to changing characteristics of the engine (hot, cold, age). It is shown that the control system proposed here could insure good stability and controllability not only for acceleration of the system but also for deceleration operation, provided that a pulse width modulated (PWM) fuel control scheme for the engine is employed in the system. It seems that the control system designed in this paper is not complicated and does not have large sensitivity with respect to variation of the characteristics of the components of the system and provides the best possible fuel efficiency.