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