A pulley unit has a hub configured to be connected to a crankshaft, a pulley coaxial to the hub and supported in a rotationally free manner with respect thereto, a clutch interposed between the hub and the pulley, and an actuator for controlling the clutch. The clutch has an inner disc rotationally coupled to the hub and having an engagement portion housed inside the pulley, a mobile member axially movable between an engagement position in which the mobile member rotationally couples the pulley to the engagement portion of the inner disc and a disengagement position in which the pulley is rotationally free with respect to the inner disc, and an elastic element acting on the mobile member to push it towards the engagement position.

A pulley unit has a hub configured to be connected to a crankshaft, a pulley coaxial to the hub and supported in a rotationally free manner with respect thereto, a clutch interposed between the hub and the pulley, and an actuator for controlling the clutch. The clutch has an inner disc rotationally coupled to the hub and having an engagement portion housed inside the pulley, a mobile member axially movable between an engagement position in which the mobile member rotationally couples the pulley to the engagement portion of the inner disc and a disengagement position in which the pulley is rotationally free with respect to the inner disc, and an elastic element acting on the mobile member to push it towards the engagement position.

A rotational coupling includes input and output hubs disposed about a rotational axis and an attachment ring disposed about the axis on one side of the input hub opposite the output hub. A flexible, multi-coil body such as a cable is disposed radially outwardly of the input and output hubs and couples the hubs together for rotation upon rotation of the input hub in one rotational direction. The body has ends coupled to the output hub and attachment ring. A torque limiter includes a torque transmission plate configured to rotate with the input hub and an armature plate fixed against rotation. The torque transmission plate and armature plate are configured to move axially together along the axis of rotation. An electromagnet disposed on one side of the torque limiter opposite the input hub attracts the plates in a second axial direction away from the attachment ring when energized.

A rotational coupling includes input and output hubs disposed about a rotational axis and an attachment ring disposed about the axis on one side of the input hub opposite the output hub. A flexible, multi-coil body such as a cable is disposed radially outwardly of the input and output hubs and couples the hubs together for rotation upon rotation of the input hub in one rotational direction. The body has ends coupled to the output hub and attachment ring. A torque limiter includes a torque transmission plate configured to rotate with the input hub and an armature plate fixed against rotation. The torque transmission plate and armature plate are configured to move axially together along the axis of rotation. An electromagnet disposed on one side of the torque limiter opposite the input hub attracts the plates in a second axial direction away from the attachment ring when energized.

A clutch system includes a rotary input member, a wrap spring clutch and a rotary output member. The wrap spring clutch has a first end, a second end, and a plurality of coils. The stiffness of the wrap spring clutch is selected such that, when transmitting less than a selected coil engagement torque, the clutch system transmits torque helically from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member. When transmitting more than the selected coil engagement torque, the clutch system transmits torque in parallel from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member, and from the rotary input member through the coil engagement surface, to the first end, and into the rotary output member.

In an aspect, a clutch assembly is provided that uses an electromagnet to generate a magnetic circuit which drives an armature to a position whereat it engages the clutch to operatively connect a rotating member to a stationary member. In embodiments wherein the armature initially rotates with the rotating member, the magnetic circuit passes through the stationary member. In embodiments wherein the armature is initially stationary, the magnetic circuit extends through the rotating member.

In an aspect, a clutch assembly is provided that uses an electromagnet to generate a magnetic circuit which drives an armature to a position whereat it engages the clutch to operatively connect a rotating member to a stationary member. In embodiments wherein the armature initially rotates with the rotating member, the magnetic circuit passes through the stationary member. In embodiments wherein the armature is initially stationary, the magnetic circuit extends through the rotating member.

An automotive air conditioning assembly including a scroll compressor and a wrap spring clutch. The wrap spring clutch enables the use of a comparatively smaller pulley (a diameter of at most 85 mm) which comparatively increases the compressor speed and hence cooling capacity at a given engine speed. The clutch requires low power (e.g. less than 5 Watts) for continuous operation.

An automotive air conditioning assembly including a scroll compressor and a wrap spring clutch. The wrap spring clutch enables the use of a comparatively smaller pulley (a diameter of at most 85 mm) which comparatively increases the compressor speed and hence cooling capacity at a given engine speed. The clutch requires low power (e.g. less than 5 Watts) for continuous operation.

A rotary clutch uses a wrap spring clutch. An actuator generates a drag force to control the wrap spring clutch to engage or disengage the clutch. The actuator includes an electromagnet, a two-component armature and an axial return spring. The two-component armature includes first and second components threadingly connected one another for relative axial translation as they rotate relative to one another, and an angular position biasing member connecting them. The second component translates axially under magnetic force from the electromagnet, and when stopped by the electromagnet the first armature component translates axially due to their threaded connection. Due to the previous axial movement of the floating component the translation of the first armature component occurs in conditions where the air gap and reluctance of a magnetic circuit is reduced compared to the prior art, and thus the overall strength of the applied magnetic field can be comparatively reduced.