WO1997024791A1

WO1997024791A1 - Salient pole motor noise reducer

Info

Publication number: WO1997024791A1
Application number: PCT/US1996/019805
Authority: WO
Inventors: William A. Harris
Original assignee: Honeywell Inc.
Priority date: 1995-12-29
Filing date: 1996-12-13
Publication date: 1997-07-10

Abstract

A motor having a salient pole rotor (12) using a noise mitigating disk (34) at each end of the rotor. The rotor, when rotating, has a tendency to pump air into the motor through slots between the poles of the rotor. The air is forced back out of the motor through slots between the poles of the stator, through air vents in the motor housing, and/or through slots between the poles on the rotor. This air pumping causes an annoying noise, such as a siren effect, in certain environments. The disks placed on the shaft and flush at the ends of the rotor greatly reduce the air pumping, thereby reducing the noise to a negligible level, and resulting in a relatively quiet motor when functioning.

Description

SALIENT POLE MOTOR NOISE REDUCER BACKGROUND OF THE INVENTION

Noisy motors are a nuisance in certain applications. For instance, cooling motors in ventilation systems, such as in a building, automobile or a computer, are preferred to be quiet as possible to keep the environmental noise level at a minimum. Some motors, such as salient pole motors, make more noise than other motors. Switch reluctance motors and permanent magnet rotor motors are some examples of noisy motors. However, such motors are necessary for certain applications. There are various noise sources in, for instance, a switched reluctance motor. Of these sources, a siren effect is caused by the high points ofthe rotor passing the slots in the stator This rotor in conjunction with the stator, functions as a pump causing air to be pumped in and out of each ofthe stator slots. Such pumping occurs at an audible frequency and at a volume sufficiently loud to be an unacceptable nuisance.

Efforts to make such motors quiet have included putting sound-insulating housings over the motors, filling in the open areas with nonmagnetic substances, using rotor lamination stacks that extend beyond the pole areas with nonmagnetic material. These and other apparent solutions have been met with obvious and significant difficulties.

Despite the years of operation of switch reluctance and other salient pole motors, no one has conceived the present invention to the knowledge ofthe present inventor who is skilled and knowledgeable in the art.

SUMMARY OF THE INVENTION At each end of the stack of magnetic metal laminations ofthe rotor in the motor, a thin, non-magnetic, preferably nonmetal disk is added which virtually eliminates the siren-effect noise.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows an end view of a salient pole motor. Figure 2 is a side view ofthe motor showing the flow of pumped air. Figure 3 illustrates the invention on a motor. DESCRIPTION OF THE EMBODIMENT

Figure 1 shows a motor 10 having a rotor 12 with salient poles 14. Rotor 12 rotates with shaft 16. Poles 14 may be non-magnetized in a switched reluctance motor or magnets in a permanent magnet motor. Stator 18 has stator poles 20 which have windings. Stator 18 and rotor 12, including the respective poles 20 and 14, are made up of laminations of magnetic material.

When rotor 12 rotates, air is pumped in through slots 22 between rotor poles 14 and expelled through stator slots 24 as shown by arrowed lines 26 and 28 of Figure 2.

Also, the pump air may be expelled through stator vents 30 as indicated by arrowed lines 32. If the stator slots 24 are filled in with a material, then the pumped air flow enters toward the center of rotor 12 in slots 22 and exits toward the periphery of slots 22 or through vents 30. As noted above, filling slots 22 is impractical because weight is added to rotor 12, rotor 12 tends to get hot and such material tends to come loose due to vibration and high revolutions per minute (RPM).

To solve the long-time existent problem noted above, the present invention involves the placement of a thin, nonmagnetic (preferably nonmetal) disk 34 at each end ofthe rotor 12 lamination stack as shown in Figure 3. Disks 34 extend from the shaft 16 diameter to approximately the outer edge of rotor slots 22 and rotor poles 14. Disks 34 are flush with the end surfaces of rotor 12. Disks 34 have a preferable thickness 36 of 0.015 to 0.020 inch, even though disk thickness 36 can, depending on the material, reasonably be between less than a thousandth of an inch to a quarter of an inch or larger. Depending on how much the flow of pumped air is to be restricted, diameter 38 of disks 34 may be between the edge of rotor slots 22, closest to shaft 16, and the edge of stator slots 24 furthest from shaft 16. The center hole of disk 34 has a diameter 38 that is approximately the same as the diameter of shaft 16; however, disk 34 may be free to rotate relative to shaft 16. Disks 34 may be made from plastic or other like material. Disks 34 are merely placed on the shaft inside the motor end housing next to rotor 12. Disks 34 significantly reduce the amount of air pumped into and out of slots 22 and 24, respectively, or vents 30. The reduction of pumped air flowing in motor 10 results in a very small or negligible noise level of motor 10 during operation.

Claims

THE CLAIMS

1. A silent salient pole motor comprising: a housing means; a stator having a pole structure, situated on the inside periphery of said housing means; a rotor having salient poles and a center shaft situated within said stator, the center shaft being supported by said housing; and a first disk situated at a first end of said rotor for reducing a flow of air caused by a pumping action of said rotor when rotating, thereby reducing motor noise.

2. The motor of claim 1 further comprising a second disk situated at a second end of said rotor for further reducing the flow of air caused by the pumping action of said rotor when rotating, thereby reducing motor noise.

3. The motor of claim 2 wherein each of said disks has an outside diameter that is between an edge ofthe poles of said rotor closest to the center shaft, and an edge ofthe poles of said stator closest to a perimeter of said housing.

4. The motor of claim 3 wherein each of said disks has a thickness between 0.001 inch and 0.250 inch.

5. The motor of claim 4 wherein each of said disks is composed of a non-metal material.

6. The motor of claim 5 wherein each of said disks has a center hole having a diameter approximately the same size as the diameter ofthe center shaft.