Generating the pressure to control the gear ratio of a continuously variable transmission in a car
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Lodz University of Technology
Publication date: 2016-12-20
The Archives of Automotive Engineering – Archiwum Motoryzacji 2016;74(4)
Continuously variable transmission used in gearboxes allows to reduce the driver's participation in the process of controlling the drive system while driving by using automatic gear ratio control, and due to its flexibility, enables the internal combustion engine to operate in the area of its greatest efficiency. Moreover, it can be used in hybrid drive systems using mechanical energy accumulators. Finding references to empirical correlations including the effect of various signals interfering with the operation of a gearbox equipped with a continuously variable transmission in literature was very difficult, therefore the aim of this study was to bench test the impact of those signals and to define characteristics for controlling pressures in the transmission pulley actuators to achieve the preset gear ratio and the ability to transfer torque. The study was conducted at a test stand simulating the behaviour of an internal combustion engine and the resistance to the movement of a car under steady and transient states. The result were establishing the characteristics for controlling the pressure in the pulley actuators and finding the effects of temperature and rotational speed of pulleys. While verifying the interfering effect of temperature, it was observed that its effect on the oil was not critical. Temperature had the greatest impact on the operation of solenoid valves, which were responsible for the process of adjusting and maintaining the pressure. Then, with the ability to control pressures in the pulley actuators, maps were created.
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