| 摘要 |
<p>A viscous fluid clutch for driving a cooling fan (18) of an internal combustion engine comprises a fluid shear gap between a rotor (10) and a casing (11, 12) from which a scoop pump (22) pumps fluid to a reservoir (20). Fluid flow between the clearance gap and the reservoir is controlled by a valve (50) actuable by a temperature dependent force (e.g. pressure from a temperature controlled valve unit (40), or a bimetallic element (71, 71'', Figs 2 and 4) opposed by pressure generated by the (or one of the) scoop pumps (22). The valve (50) may be either in the return line (24) or at the supply port (26) of the fluid shear gap. The temperature dependent force and the scoop pump pressure may act on separate pistons (121, 63'', Figs 7,8) acting in opposition on a lever (113).</p> |
