| 摘要 |
PURPOSE:To reduce the working period and the speed of revolution of a cooling fan, by differentiating the detected output from a temperature sensor, which detects the temperature of cooling water for an engine by time, and by controlling the drive of a cooling fan based on the value obtained by differentiation. CONSTITUTION:A temperature sensor 12 is arranged to a cooling water pipe 3 of an engine 1, and the detected output from said temperature sensor 12 is put into both a comparator 13 to compare the output with the predetermined, reference voltage Es, and into a differential circuit 16. When the temperature exceeds the set value theta1, the detected value also exceeds ES, and then a comparator 13 closes a switch 14a. On the other hand, the output from a differential circuit 16 is put into a control circuit 18 through a comparator 17. A switch 18a is closed when the differentiated value is positive number, that is, the time when the temperature rises, while the switch 18a is opened when the differentiated value is a negative number, that is, the time when the temperature drops. Accordingly, a cooling fan driving motor 11 is driven through a drive circuit 15, when the temperature of cooling water is above theta1 and the temperature is rising at the same time, but the fan is stopped while the temperature is dropping. |
