The present invention relates to a clamping unit for an injection-moulding machine, which has rotary joints and, in particular, toggle joints with joint faces that are moved in relation to one another. Such joints must be lubricated adequately and reliably. The object of the present invention is therefore to present a clamping unit for an injection-moulding machine that provides simple, low-cost and reliable lubrication and allows good sealing of the joints. According to the invention, a magnet device designed for holding a magnetofluid is therefore provided in the region of the joint faces of at least one of the joints.