The reduction of consumption and emissions is a key fac- tor in modern vehicle design. The overall vehicle efficiency is pursued in several ways, including the reduction of consumption of the auxiliary devices (e.g. water pumps, oil pumps, vacuum pumps etc.). In this paper, using two different smart materials (i.e. magnetorheological fluids and shape memory alloys) a de- vice aimed at disengaging the vacuum pump was developed. The conceived device is composed of a magnetorheological (MR) clutch excited by permanent magnets coaxially manufac- tured with a sliding spline sleeve moved by shape memory alloys (SMA) springs. In the MR clutch, the magnet can move under the effect of a passive pneumatic system. The magnetic field in the fluid varies with the magnets displacement and as a result two steady positions are possible: the engaged clutch (ON) and the disengaged clutch (OFF). The torque in the ON configuration is high enough to drive the vacuum pump during normal operating conditions, whereas the low torque value in the OFF condition guarantees power saving up to 150 W. In particular operating conditions (i.e. at low environmen- tal temperatures) the torque necessary to start the vacuum pump may exceed the maximum transmissible torque of the MR clutch. For this reason a sliding spline sleeve, actuated by two SMA springs which counteract the force of two traditional springs was developed. A dummy plain sliding sleeve with SMA and con- ventional springs was numerically developed and tested. The fairly good agreement of the results confirmed the feasibility of the combined SMA/MR device.
Development and testing of a hybrid SMA/MR passive clutch
BUCCHI, FRANCESCO;FORTE, PAOLA;FRENDO, FRANCESCO
2014-01-01
Abstract
The reduction of consumption and emissions is a key fac- tor in modern vehicle design. The overall vehicle efficiency is pursued in several ways, including the reduction of consumption of the auxiliary devices (e.g. water pumps, oil pumps, vacuum pumps etc.). In this paper, using two different smart materials (i.e. magnetorheological fluids and shape memory alloys) a de- vice aimed at disengaging the vacuum pump was developed. The conceived device is composed of a magnetorheological (MR) clutch excited by permanent magnets coaxially manufac- tured with a sliding spline sleeve moved by shape memory alloys (SMA) springs. In the MR clutch, the magnet can move under the effect of a passive pneumatic system. The magnetic field in the fluid varies with the magnets displacement and as a result two steady positions are possible: the engaged clutch (ON) and the disengaged clutch (OFF). The torque in the ON configuration is high enough to drive the vacuum pump during normal operating conditions, whereas the low torque value in the OFF condition guarantees power saving up to 150 W. In particular operating conditions (i.e. at low environmen- tal temperatures) the torque necessary to start the vacuum pump may exceed the maximum transmissible torque of the MR clutch. For this reason a sliding spline sleeve, actuated by two SMA springs which counteract the force of two traditional springs was developed. A dummy plain sliding sleeve with SMA and con- ventional springs was numerically developed and tested. The fairly good agreement of the results confirmed the feasibility of the combined SMA/MR device.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
