Engine cooling fan coupling system controlled in concert with a cooling

Abstract

An automotive vehicle engine having a coolant circulation system with a radiator, a fan, and a thermostatic valve for controlling coolant flow through the radiator. This thermostatic valve starts to open at a first temperature, is fully opened at a second temperature, and is partly opened at an intermediate third temperature. A system for coupling the fan to a rotation engine member includes: a first member rotationally coupled to the rotating member; a second member rotationally coupled to the fan; and a mechanism for providing rotational coupling between the first and second members. The degree of rotational coupling is lower when a first control valve is closed than opened, and is lower when a second control valve is closed than opened. The first control valve is opened when and only when the temperature of air passing the radiator is greater than a determinate temperature; and the second control valve is opened when engine coolant temperature rises from below to above a fourth temperature, while being closed when it drops from above to below a fifth temperature substantially lower than the fourth temperature. The fourth and fifth temperatures are substantially higher than the third temperature, differing therefrom respectively by first and second temperature differences, the second of which is substantially less than the first and the fifth temperature is higher than the second temperature.