A switchable one-way clutch is provided for selectively switching between operating as a one-way clutch and a bi-directional locking clutch. The clutch includes a housing, and an outer race and an inner race, which is fixed rotationally to the housing. The clutch also includes a roller cage assembly having a plurality of rollers contactable with the inner race and the outer race. A roller cage is configured to position and contain the plurality of rollers therein. The clutch also includes an annular drag plate contacting the inner race. The drag plate is rotationally fixed to the roller cage and is moveable in an axial direction relative to the roller cage. An electromagnet assembly is configured to magnetize in response to electric energy. Via selective magnetization to attract the drag plate axially, the clutch can switch between operating modes.

An electromagnetic clutch includes a field core including a coil storage groove, and a rotor including a core storage groove. The coil storage groove is formed by an inner cylindrical portion, an outer cylindrical portion, and a bottom portion. The bottom portion of the field core wholly projects to the outside of the core storage groove. The outer peripheral surface of the inner cylindrical portion and the inner peripheral surface of the outer cylindrical portion include a first transition surface and a second transition surface, respectively, on the bottom portion side. Each of the first transition surface and the second transition surface includes a tilting surface that gradually narrows the groove width of the coil storage groove along with an increase in a distance from the side of the opening of the coil storage groove.

A field core unit for an electromagnetic clutch can include: a field coil generating a magnetic flux; a magnetic part provided with an annular-shaped insertion groove encompassing lower and side portions of the field coil such that the magnetic flux flows through the magnetic part; and a field core configured such that an upper surface thereof is open and an interior space is formed therein. The magnetic part can be inserted into the field core.

An electromagnetic actuating device for a torque transmission system includes a shell arranged around an axis X, the shell being fixed relative to the axis X. The shell includes walls defining an annular cavity which houses a coil and at least partially a plunger which is able to move axially along the axis X to actuate a coupling device.

A soft actuator includes a power input shaft, and multiple electromagnetic clutches are coaxially installed in series on the power input shaft. A bending elastic part is arranged between the thrust plate of each electromagnetic clutch and the gear frame of the electromagnetic clutch. The bending elastic part is installed on the sleeve of the gear frame and in contact with the baffle of the gear frame. The bending elastic part is connected with the clutch output gear of the electromagnetic clutch through the gear frame. The gear frame is fixedly connected with the clutch output gear and rotates coaxially.

A yoke includes an annular groove in which an exciting coil is stored, and a first through hole formed in the bottom of the annular groove. A terminal housing includes a boss portion fitted in the first through hole and a connecting concave portion located on the opposite side of the annular groove with respect to the boss portion. The boss portion includes a second through hole extending in a direction parallel to the center line of the first through hole. An external connecting terminal is buried in the terminal housing. The external includes a coil extraction hole continuing to the second through hole. The extraction end of the exciting coil is soldered to the terminal in a state in which the extraction end is passed through the second through hole and the coil extraction hole.

An electromagnetic clutch includes a field core including a coil storage groove, and a rotor including a core storage groove. The coil storage groove is formed by an inner cylindrical portion, an outer cylindrical portion, and a bottom portion. The bottom portion of the field core wholly projects to the outside of the core storage groove. The outer peripheral surface of the inner cylindrical portion and the inner peripheral surface of the outer cylindrical portion include a first transition surface and a second transition surface, respectively, on the bottom portion side. Each of the first transition surface and the second transition surface includes a tilting surface that gradually narrows the groove width of the coil storage groove along with an increase in a distance from the side of the opening of the coil storage groove.

A bistable electromagnetic clutch is provided that includes a first part, a second part and an spring part. The first part includes a yoke with a plurality of iron cores, and an electromagnetic coil on each of the iron cores. The second part includes a moving carrier disc and a magnetic conductive disc that is fixed on a side of the moving carrier disc that is away from the yoke. Several magnets are fixed on the moving carrier disc, and the iron cores and the magnets are provided in a correspondence relation. The spring part is configured to keep the moving carrier disc and the yoke in normally separated positions. Two adjacent electromagnetic coils form a group, two electromagnetic coils in a same group are wound to form a group of windings with identical magnetic polarities, and corresponding two magnets form a group of magnetomotive forces with identical magnetic polarities.

A yoke includes an annular groove in which an exciting coil is stored, and a first through hole formed in the bottom of the annular groove. A terminal housing includes a boss portion fitted in the first through hole and a connecting concave portion located on the opposite side of the annular groove with respect to the boss portion. The boss portion includes a second through hole extending in a direction parallel to the center line of the first through hole. An external connecting terminal is buried in the terminal housing. The external includes a coil extraction hole continuing to the second through hole. The extraction end of the exciting coil is soldered to the terminal in a state in which the extraction end is passed through the second through hole and the coil extraction hole.

A coil housing has an inner ring, which is shaped into an annular form and is placed on an inner side of an electromagnetic coil in a radial direction of a rotational axis. A thermal fuse is placed on an inner side of a coil inner peripheral end of the electromagnetic coil in the radial direction, so that the thermal fuse can be placed in such a manner that the thermal fuse does not limit a length of the electromagnetic coil in a direction of the rotational axis by using a radial thickness of the inner ring that is indispensable as a part of a structure of a magnetic circuit. Thus, it is possible to sufficiently limit occurrence of limiting of a size of the electromagnetic coil that is caused by the placement of the thermal fuse.