A haptic operating device having a magnetorheological braking device, a fixed holder, and two braking components. One braking component is non-rotatably connected to the fixed holder. Both braking components are continuously rotatable relative to one another about a rotation axis. A first braking component extends along a rotation axis and comprises a magnetically conductive core. The second braking component comprises a hollow casing part extending around the first braking component. At least one circumferential braking gap filled with a magnetorheological medium is between the first and second braking components. An electrical coil, surrounding the core and around the rotation axis, is between the casing part and the core. Two different radial braking gap portions and a disk contour are formed at a first braking gap portion between the casing part and the core, and a plurality of rolling bodies are arranged as magnetic field concentrators at the periphery of the core in a second braking gap portion.

A magnetorheological braking device with a fixed mount and with two braking components. One of the two braking components is non-rotatably affixed to the mount and the two braking components are continuously rotatable relative to one another. A first braking component extends in the axial direction. The second braking component has a hollow shell part that extends around the first braking component. A peripheral gap is filled with a magnetorheological medium. The first braking component has an electric coil and a core made from a magnetically conductive material. Magnetic field concentrators on the core and/or magnetic field concentrators on the shell part protrude into the gap, which results in a peripheral gap with a variable gap height. A magnetic field of the electric coil runs through the core and the magnetic field concentrators and through the gap into a wall of the shell part.

A magnetorheological braking device has two braking components that are continuously rotatable relative to one another. A first braking component extends in the axial direction and the second braking component includes a hollow casing extending around the first braking component. A peripheral gap is filled with a magnetorheological medium. The first braking component has an electric coil and a magnetically conductive core which extends in the axial direction. A star contour with magnetic field concentrators on the core and/or on the shell part project into the gap, which results in a peripheral gap region with a variable gap height. The electric coil is wound around the core such that a magnetic field runs through the core and the magnetic field concentrators and through the gap into a wall of the casing. A star contour is formed by a stack of star plates.

A sleeve or case for a mobile device, such as a smartphone or tablet or other types of hand-held device or mobile smart device, has a sleeve part for at least partially enclosing the mobile device and an input device arranged in the sleeve part for controlling the mobile device which can be received in the sleeve part. The input device includes a movable control element and a magnetorheological brake. Any movement of the control element can be selectively damped by way of the magnetorheological brake.

A haptic operating device having a magnetorheological braking device, a stationary holder, and two brake components. One of the brake components is connected to the holder for fixed rotation therewith. The brake components can be continuously rotated relative to one another about a rotation axis. A first brake component extends along the rotation axis and has a magnetically conductive core. The second brake component has a hollow casing part extending around the first brake component. Axially spaced apart peripheral braking gap portions formed between the first and second brake components are at least partially filled with a magnetorheological medium. At least one third braking gap portion is located axially between a first and a second braking gap portion. A first electric coil is assigned to the first braking gap portion and a separately controllable second electric coil is assigned to the second braking gap portion.

A magnetorheological fluid includes: a first metal magnetic particle having an average particle diameter of 5 m or more; a second metal magnetic particle having an average particle diameter of 500 nm or less; and an ionic liquid having a cationic group and an anionic group, in which the cationic group is one or more selected from the group including a quaternary ammonium ion, an imidazolium ion, a pyridinium ion, and a phosphonium ion, and the anionic group is one or more selected from the group including a tetrafluoroborate ion, a hexafluorophosphate ion, a trispentafluoroethyl trifluorophosphate ion, and a bis(trifluoromethanesulfonyl)amide ion.