Method and apparatus for controlling a variable speed fan in an image forming device

Abstract

An improved variable speed fan controller for use in devices such as laser printers. The controller automatically adjusts its output signal to fans such that a fan quickly settles into an appropriate operating speed, even if the fan has been newly installed into the equipment. The controller can store values in non-volatile memory, if desired, to keep track of recent changes in the fan's operating parameters and corresponding control signal values. The controller is able to control relatively inexpensive fans that don't necessarily operate at a predictable fan rotating speed under repeatable conditions and control signals, by controlling the fan to an initial or predetermined rotating speed; if the fan isn't running within a suitable range of rotational speeds, then determining whether a fine or coarse adjustment should be made to the fan's rotational speed. The controller makes appropriate adjustments until the fan's rotational speed is within acceptable operating tolerances.

Description

TECHNICAL FIELD [0001] The present invention relates generally to image forming equipment and is particularly directed to equipment of the type which includes a fan for cooling. The invention is specifically disclosed as a variable speed fan and controller that quickly settles into an appropriate operating speed, even if the fan has been newly installed into the equipment. BACKGROUND OF THE INVENTION [0002] In many modern electronic devices a cooling fan is used to regulate the temperature of the device during operation. In most laser printers, this is an especially important design element due to the presence of an active heating element, typically a fuser that melts the toner to the paper. In such equipment, the cooling fan must be controlled in such a way so as to strike a suitable balance between two competing goals of controlling the internal temperature of the device and minimizing the acoustic impact of the device upon its environment. The designer can always install a fan th...

AI Technical Summary

Benefits of technology

The present invention provides a fan control circuit and operating method that can control inexpensive fans with low-frequency tachometer output signals. The circuit includes a processing circuit, memory circuit, output circuit, and input circuit. The circuit can automatically adjust the fan's rotational speed to a desired speed, and can make fine and coarse adjustments as needed. The circuit can also store additional operating parameters for future use. The fan control circuit can be used with a variety of fans and can be easily integrated into existing systems. The invention also provides a method for determining the fan's actual rotating speed and adjusting the control signal accordingly. Overall, the invention provides a cost-effective solution for controlling fans with low-frequency tachometer output signals.

Problems solved by technology

The designer can always install a fan that blows more air, but this approach quite often causes a greater noise level that usually is undesirable.

The frequency of the “tach” signal in these low cost fans is generally too low to provide enough information for a host device to use conventional motor control means for actively controlling the speed of the fan.

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