Multiple fan system having means for reducing beat frequency oscillations

• US 6,257,832 B1
• Filed: 02/04/1999
• Issued: 07/10/2001
• Est. Priority Date: 02/04/1999
• Status: Expired due to Term

• Current Assignee: Dell USA LP (Dell Technologies Inc.)
• Original Assignee: Dell USA LP (Dell Technologies Inc.)
• Inventors: Lyszkowski, Keith Alan, Wallace, Douglas E. Jr.
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): ROBINSON, DANIEL LEON
• Application Number:
  US09/245,145
• Time in Patent Office: 887 Days
• Field of Search: 417/2, 240/4, 218/6, 2 8/9, 165/87, 364/175, 700/70, 361/695
• US Class Current: 417/2
• CPC Class Codes: F04D 29/661 especially adapted for elastic fluid pumps
• CPC Class Codes: G06F 1/20 Cooling means

Abstract

A multiple fan system including at least two simultaneously operated fans. Each of the fans are operable as a constant speed fan and as an oscillating speed fan. Not more than one of the fans is operated as a constant speed fan. Each fan not being operated as a constant speed fan is operated as an oscillating speed fan. A fan controller operates each oscillating speed fan in a mode whereby a respective acoustic emission having a range of frequency different than any other oscillating speed fans is produced.

Claims

1. A computer system in combination with a multiple fan system, comprising:

a microprocessor mounted in a chassis;

an input coupled to provide input to the microprocessor;

a mass storage coupled to the microprocessor;

a video controller coupled to the microprocessor;

a memory coupled to provide storage to facilitate execution of computer programs by the microprocessor; and

a multiple fan ventilating system mounted in the chassis, the multiple fan system including;

at least two simultaneously operated fans, each fan being capable of operating as a constant speed fan or as an oscillating speed fan, one of the fans always being operated as a constant speed fan, and simultaneously, each other fan always being operated as an oscillating speed fan; and

a fan controller capable of controlling a plurality of fans, the fan controller operating each of the oscillating speed fans within a different range of speed from each other oscillating speed fan, the controller providing an output voltage having a varying duty cycle and providing an oscillating fan speed profile having an oscillating speed range.

2. The computer system of claim 1 wherein the fan controller includes a waveform generating portion coupled to a duty-cycle modulator portion.

3. The computer system of claim 1 wherein each of the fans is electrically operated by a DC voltage and the fan controller varies the DC voltage provided to the oscillating speed fans.

4. The computer system of claim 1 wherein each of the fans is electrically operated by a DC voltage and the fan controller utilizes a continuously varying duty-cycle for varying the DC voltage provided to the oscillating speed fans.

5. The computer system of claim 1 wherein each of the fans is electrically operated by a DC voltage and the fan controller includes a wave generator and a duty-cycle modulator for varying the DC voltage.

6. The computer system of claim 1 wherein the multiple fan system includes two oscillating speed fans and wherein the fan controller operates the first fan within a first range of speed and the second fan within a second range of speed.

7. The computer system of claim 2 wherein the duty cycle modulator portion is coupled to a voltage relay device.