Abstract: A cooling fan device uses a cooling fan coupled to an engine via a fan clutch to generate cooling air flow for a radiator. The cooling fan device includes an electronic control unit configured to control an engagement rate of the fan clutch. The electronic control unit is configured to execute a first calculation process, a second calculation process, and an upper limit guarding process, thereby controlling the engagement rate based on a value of a coolant temperature requested engagement rate that has been subjected to an upper limit guarding process. A first upper limit rotation speed is set to a lower speed when a vehicle speed is relatively low than when the vehicle speed is relatively high.

Abstract: A cooling fan device includes an electronic control unit that controls an engagement rate of a fan clutch. The electronic control unit executes a first calculation process that calculates an air conditioner requested engagement rate, a second calculation process that calculates, as a first guard value, a value of an engagement rate at which a fan rotation speed increases at a specified speed and an upper limit guarding process that sets a value of the air conditioner requested engagement rate to the first guard value when a calculated value of the air conditioner requested engagement rate in the first calculation process exceeds the first guard value. The electronic control unit further controls the engagement rate of the fan clutch based on a value of the air conditioner requested engagement rate after execution of the upper limit guarding process.