Valve unit

A valve unit, in particular an EGR valve unit, comprises a converting mechanism for converting the rotary movement of a drive shaft (28) in a linear movement for actuating a slideable actuating shaft (20) attached a valve closing member (18). The converting mechanism comprises a driving member (32), an actuating member (34) and a supporting member (36). The actuating member (34) is connected to the driving member (32) by a first, revolute joint (B) and the actuating member (34) is connected to the supporting member (36) by a second, revolute joint (C). The driving member (34) is coupled to the drive shaft (28) by a third joint (A) and the supporting member (36) is pivotally mounted onto the valve body (12) by a fourth joint (D). The actuating member (34) comprises a fifth joint (E) by means of which an axial actuating force is transmitted to the actuating shaft (20). The the positions of the joints (A; B; C; D; E) are selected in such a way that, for the operating angle range of the drive shaft (28), the fifth joint (E) remains substantially aligned with the actuating shaft (20).