A fail-safe magnetorheological clutch excited by permanent magnets for the disengagement of automotive auxiliaries

Abstract

This work was carried out in the framework of a funded project aimed at evaluating the feasibility of an ad hoc clutch for the disengagement an auxiliary device, i.e. the vacuum pump used with the powerbrake in diesel engine vehicles, when its operation is not required. In this way it is possible to improve the overall vehicle efficiency. Strict design specifications were defined with reference to available room, torque transmission, absence of axial loads and fail-safe operation. A magnetorheological clutch with permanent magnets was conceived to fulfil the technical requirements. Different clutch geometries were compared with particular reference to the fail-safe operation and torque capabilities. After an iterative procedure, in which both mechanical design and magnetic field analyses were considered, the most promising solution was defined and a prototype was built and tested. A four-pole sliding permanent magnet was adopted to generate the magnetic field. The experimental results validated the developed models and demonstrated the feasibility developed models and demonstrate the feasibility of the proposed solution. A principle for the automatic clutch actuation is also presented.

An innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization

“…A solution, which proved to be effective and reliable in the on/ off control strategy, is described in details in [2,10]. The magnet, by means of an o-ring seal, splits the chamber in two hermetically separated parts.…”

“…It was developed in a framework of a project aimed to reduce the energy consumption of the vacuum pump in a servo assisted brake system for automotive applications [2,3]. The clutch was interposed between the cam shaft and the vacuum pump in order to disengage the pump when its operation is no longer necessary.…”

Design and development of a hybrid Magneto-Rheological clutch for safe robotic applications

“…The use of permanent magnets (PMs) as the primary actuation source in MR clutches has received less attention though. A fail-safe MR device excited by permanent magnets was proposed in [2]. The device was designed to engage and disengage a power brake vacuum pump from a diesel engine.…”

Optimization of a Novel Magneto-Rheological Device With Permanent Magnets

“…Finally, very few examples of fluid excitation based on a pure PMs system can be found in literature [15,[17][18][19][20][21][22][23][25][26][27][28]. This solution has some advantages with respect to the conventional wired excitation system.…”

“…As for magnetorheological brakes or clutches, many solutions based on the shear mode have been developed in the past years [13][14][15][16][17][18][19][20]. In these devices, the use of MR fluids allows to obtain smooth and steady transmissible/braking torque, with many potential applications especially when simple structure, smooth, reliable and variable compliance are desirable characteristics (i.e., in automotive industry, robotics, and gym/fitness equipments).…”