A coupling device for a hydrostatic continuously variable transmission

A coupling device (CL) for a hydrostatic continuously variable transmission (CVT), which is designed such that a hydraulic pump (P) and a hydraulic motor (M) with each other through a closed hydraulic circuit (50, 56, 57) are connected, wherein the capacity of the is the hydraulic pump (P) and / or of the hydraulic motor (M) controlled / regulated such that an input rotation of the hydraulic pump (P) is changed and is output as the output rotation of the hydraulic motor (M), wherein the coupling device comprises (CL): a clutch valve (70) for connecting and disconnecting a high pressure side oil passage (57) and a low pressure side oil passage (56) connecting the closed hydraulic circuit (50, 56, 57) form to the transmission of rotation from the hydraulic pump (P) to the hydraulic motor (M) to control / regulate; to generate a governor mechanism (61, 62) to centrifugal force generated using a through the input rotation of the hydraulic pump (P) one of the input rotational speed of the hydraulic pump (P) corresponding governor force (Fgov), and this governor force (Fgov) in the closing direction of the clutch valve (70) act to make; Clamping means (63), in order to let a clamping force (FSPG) in the opening direction of the clutch valve (70); and a buffer mechanism (78a, 78b, 70c) for attenuating the opening and closing movements of the in accordance with the governor force (Fgov) and the clamping force (FSPG) operated clutch valve (70), characterized in that the clutch valve (70) is arranged such that a valve slide (70) movable in a valve hole (6d) is arranged, which in axial direction of a support shaft (6) for rotatably supporting the hydraulic pump (P) and hydraulic motor ( M) is formed so that the high-pressure side oil passage (57) and the low pressure side oil passage (56) in accordance with the movement of the valve spool (70) in the slide hole (6d) connected or disconnected.