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Axial fan and control method thereof

  • US 10,570,740 B2
  • Filed: 01/09/2018
  • Issued: 02/25/2020
  • Est. Priority Date: 04/20/2012
  • Status: Active Grant
First Claim
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1. A control method of an axial flow fan, comprising the steps of:

  • providing a pulse width modulation signal;

    calculating whether a duty cycle of the pulse width modulation signal is lasted for a period of time; and

    determining the duty cycle of the pulse width modulation signal when the duty cycle of the pulse width modulation signal is lasted for the period of time;

    wherein the axial flow fan comprises a fan frame and a single impeller, the fan frame has a frame body, a base and a plurality of connecting members, the base is disposed at a central portion of one side of the frame body, the connecting members connect the frame body and the base, the single impeller is accommodated in the frame body and disposed at the base, the single impeller has a rotating shaft, a hub and a plurality of blades disposed around the outer periphery of the hub, each of the blades has a camber line, an edge end and a hub end, a straight line connecting the edge end and the hub end and a projection line of each of the blades on a tangent plane of the rotating shaft form a stagger angle in a cross section from the hub end to the edge end of the blade, wherein a tangent line tangent to the camber line at the edge end and a tangent line tangent to the camber line at the hub end form a camber angle in the cross section from the hub end to the edge end of the blade;

    when the duty cycle is in a stop range, controlling the axial flow fan to stop operating, wherein the stop range is between a first value and a second value, and the second value is greater than the first value;

    when the duty cycle is in a second range, controlling the axial flow fan to rotate forwardly, wherein the forward-rotation range is between a third value and a fourth value, the fourth value is greater than the third value, and the third value of the forward-rotation range is greater than the second value of the stop range; and

    when the duty cycle is in a third range, controlling the axial flow fan to rotate reversely, wherein the reverse-rotation range is between a fifth value and a sixth value, the sixth value is greater than the fifth value, and the fifth value of the reverse-rotation range is greater than the fourth value of the forward-rotation range.

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