Patent Application
20110133680
The present invention relates to a method of controlling the speed of a cooling fan.
Fans are used to direct cooling air to a variety of vehicle components, such engine cooling system components, cab heating, cooling and ventilation units, etc. Such fans produce acoustic noise at an amplitude and frequency which is dependent upon the speed of the fan. The noise produced at the fan is transferred through structural components to an observer, such as the vehicle operator. The noise amplitude may have maximums and minimums which occur at one or more fan speeds due to resonances. Fan speed is typically controlled either manually by operator setting of speed, or automatically in response to a desired temperature set by an operator or by some other requirement. In such a control system, the fan speed may be set to operate at a speed that produces a high level of acoustic noise. This results in operator discomfort and customer dissatisfaction. It would be desirable to control the speed of such a fan so that the fan does not run for long periods of time at speeds which produce noise maximums.
Accordingly, an object of this invention is to provide a method for controlling the speed of a fan so that the fan does not run for long periods of time at speeds which produce noise maximums.
This and other objects are achieved by the present invention, wherein a fan speed control system includes a cooling fan driven by a motor, a motor driver for driving the motor at a speed corresponding to a fan speed control signal, and an electronic control unit (ECU) for generating the fan speed control signal as a function operator and/or sensor inputs. The method includes generating a fan speed control signal and communicating the fan speed control signal to the motor driver so that the motor driver drives the motor at a speed corresponding to the fan speed control signal. If the fan speed control signal is at a level below a noisy fan speed range, then the ECU maintains the fan speed control signal below the noisy fan speed range until the ECU commands a fan speed above the noisy fan speed range. If the fan speed control signal is at a level above the noisy fan speed range, then the ECU maintains the fan speed control signal at a level above the noisy fan speed range until the ECU commands a fan speed below the noisy fan speed range. The method may also include generating a minimum fan speed control signal so that the motor driver drives the motor at a lowest speed that will allow the cooling fan to provide a desired cooling effect.
Referring to
The ECU 20 executes an algorithm 100 represented by
At step 102 the ECU 20 executes a known basic fan speed control algorithm which generates a fan speed control signal as a function of the temperature sensed by sensor 22 and operator inputs (not shown). Preferably, this basic algorithm attempts to run the fan motor 16 at the lowest speed which will achieve the desired cab temperature.
According to the present invention, in addition, at step 104, if the fan speed control signal is at a level below the noisy fan speed range, then the ECU 20 maintains the fan speed control signal below the noisy fan speed range until the ECU 20 commands a fan speed above the noisy fan speed range. When such a higher fan speed is commanded, the ECU 20 will generate fan speed control signals which will rapidly cause the speed of the fan motor 16 to increase to a fan speed faster than the noisy fan speed range.
Also, at step 106, if the fan speed control signal is at a level above the noisy fan speed range, then the ECU 20 maintains the fan speed control signal at a level above the noisy fan speed range until the ECU 20 commands a fan speed below the noisy fan speed range. When such a lower fan speed is commanded, the ECU 20 will generate fan speed control signals which will rapidly cause the speed of the fan motor 16 to decrease to a fan speed slower than the noisy fan speed range. With this method, the fan speed will not remain for long periods at speeds at or near the maximum noise speed. Preferably, this method operates in both the Auto and Manual modes of the ECU 20. With this method, Noise levels would be reduced, and the operator environment would be more pleasant, causing improved customer satisfaction.
While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.
