BLOWER

Abstract

A blower for use with a hand dryer and the like has a motor; an impeller driven by the motor; a diffuser for directing air from the impeller; and a housing accommodating the motor, the impeller and the diffuser. The motor has a rotor and a stator. The rotor has a shaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotor core, and a protective sleeve surrounding the ring magnet.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201020140173.0 filed in The People's Republic of China on Mar. 22, 2010.

FIELD OF THE INVENTION

This invention relates to an electric blower and in particular, to a blower suitable for use in a hand dryer or air cleaner.

BACKGROUND OF THE INVENTION

A known blower includes a motor with a rotor and a stator, an impeller driven by the motor and a housing with an air inlet and an air outlet and in which the motor and the impeller are accommodated. The rotor has a ring magnet made of bonded NdFeB (neodymium iron boron) rare earth and adhered to a rotor core of the rotor. The blower has a disadvantage of low reliability and usability, because the ring magnet may breakdown when the rotor is rotating at high speed, such as over 15000 rpm (revolutions per minute). At this speed the bonded rare earth magnet tends to disintegrate due to the forces on the magnet. Even sintered rare earth magnets become physically unstable at rotational speeds above 40,000 rpm. However, modern appliances, such as hand dryers and air cleaners are requiring motors with high rotation speeds and light weight.

SUMMARY OF THE INVENTION

Hence there is a desire for a blower having a permanent magnet rotor which can withstand high speed rotation so as to be suitable for use with a hand dryer or the like.

Accordingly, in one aspect thereof, the present invention provides a blower comprising: a motor with a rotor and a stator; an impeller driven by the motor; a diffuser for directing air from the impeller; and a housing accommodating the motor, the impeller and the diffuser and having an air inlet and an air outlet, wherein the rotor comprises: a shaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotor core, and a protective sleeve tightly surrounding the ring magnet.

Preferably, the protective sleeve is made of metal.

Preferably, the protective sleeve is made of stainless steel plate.

Preferably, thickness of the protective sleeve is between 0.1 mm and 0.3 mm.

Preferably, the ring magnet is a bonded NdFeB rare earth ring magnet or a sintered NdFeB rare earth ring magnet. NdFeB rare earth magnets provide a higher magnetic energy in a smaller lighter package and thus can reduce the size and thus weight of the motor.

Preferably, the rotor has a pair of balance rings that press against the axial ends of the ring magnet to prevent axial movement of the ring magnet with respect to the rotor core.

Preferably, the ring magnet has an axial length that is longer than the axial length of the rotor core and each of the balance rings has a boss that locates within the respective axial end of the ring magnet.

Preferably, the ring magnet is keyed to the rotor core by a tongue in groove connection to prevent rotation of the ring magnet about the rotor core.

Preferably, the diffuser is disposed between the impeller and the motor for directing air from the impeller to the motor via a plurality of air passages and wherein the diffuser supports a bearing for the shaft.

Preferably, the rotor is configured to rotate at a speed greater than 25,000 rpm, preferably greater than 40,000 rpm.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labelled with a same reference numeral in all the figures in which they appear.

Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below.

FIG. 1 shows a blower in accordance with the preferred embodiment of the present invention;

FIG. 2 is a view of the blower of FIG. 1, with a housing removed;

FIG. 3 is a side view of the blower in FIG. 2;

FIG. 4 is a view from below of the blower of FIG. 3, showing an impeller and a diffuser, being parts of the blower;

FIG. 5 is a partially exploded view of a rotor of the blower; and

FIG. 6 is an exploded view of a rotor assembly without a shaft, according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4 illustrate a blower 100 in accordance with the preferred embodiment of the present invention. The blower comprises an impeller 200, a diffuser 300, a motor 400 and a housing 500.

The housing 500 comprises a first housing member 510 and a second housing member 520. The first housing member 510 accommodates the impeller 200 and the diffuser 300 and forms a volute for the impeller. A second housing member 520 accommodates the motor 400. The first housing member 510 comprises a circular side wall 512 and a bottom wall 514. The second housing member 520 comprises a hollow cylinder 522 with an end plate 524. A flange 526 extends outwardly and radially from the lower open end of the cylinder 522 adjacent to the first housing member 510. The flange 526 is fixedly assembled with the side wall 512 of the first housing member 510, preferably by crimping the side wall 512 to the flange. An air inlet 516 is formed at the center of the bottom wall 514 of the first housing member 510 and air outlets 523 are formed on the hollow cylinder 522 of the second housing member 520, at the upper, closed end thereof. A boss 525 is formed in the end plate 524 with a hole arranged for holding a bearing 433. Preferably, the first housing member 510 is a stamped sheet metal part while the second housing member 520 is an injection molded plastics material part.

In FIGS. 2 to 4, the blower is shown with the housing removed to show the impeller, diffuser and motor disposed within the housing. The impeller 200 is fixed to and rotates with a shaft 442 of the motor 400. The impeller 200 comprises a cover 220, a base 240 and a plurality of curved blades 260. The cover 220 has an opening 222 formed at center thereof and opposite to the air inlet 516. The plurality of blades 260 are disposed between the cover and the base, extending in a generally radial manner from the opening and evenly distributed circumferentially to form a plurality of flow passages through which air passing through the opening 222 flows when the impeller is rotating. Each blade 260 has a plurality of tabs 262 on each of the two long edges and holes corresponding to the tabs 262 are formed in the cover 220 and the base 240. A tab 262 and a corresponding hole constitute a clamp structure. The blades 260 are firmly fixed between the cover 220 and the base 240 by crimping or otherwise deforming the tabs after they have been inserted into the holes to prevent their removal, in a manner generally known in the art.

The diffuser 300 is arranged between the impeller 200 and the motor 400 and fixedly mounted to the housing 500. The diffuser 300 is provided with a circular body 320 which has an outer diameter larger than the impeller 200 and is fitted to an inner surface of the circular side wall 512 of the first housing member 510. A bearing holder with a through hole is formed at center of the circular body 320 for holding a bearing 445 for the shaft 442. A plurality of diffusing structures 340 integrally formed with the circular body 320 are evenly arranged at outer periphery of one surface of the circular body 320 facing the impeller 200. Each diffusing structure 340 and the inner surface of the circular side wall 512 of the first housing member 510 defines a diffusing passage 342 which guide the air flow axially as well as circumferentially. A plurality of air guides 360 integrally formed with the circular body 320 are evenly arranged on one surface of the circular body 320 facing the motor 400. Air passages 362 are formed between adjacent air guides 360 and guide the air flow from the diffusing passages into the hollow body 522 of the second housing 520, to be exhausted from through the outlets 523. Thus the diffuser 300 channels or guides the air flow from the impeller 200 into the hollow body 522. Pressured air exiting from the impeller 200 flows into the air passages 362 via the diffusing passages 342 and then are guided to the motor 400 by the air passages 362 so as to be expelled from the blower 100 through the air outlets 523 of the second housing member 520.

The motor 400 is a brushless motor with a permanent magnet rotor 440 and a stator 420 surrounding the rotor 440. The stator 420 is fixed to the second housing member 520 and comprises a stator core 422 and windings (not shown in the figures) wounded on teeth 424 of the stator core 422. In the embodiment shown, there are six stator poles formed by six teeth 424. The rotor 440 comprises a shaft 442, a rotor core 444 fixed to the shaft 442, and a ring magnet 446 fixed to the rotor core 444. The shaft 442 is rotatably supported by two bearings 443 and 445. The ring magnet 446 is a bonded NdFeB rare earth ring magnet to lower the cost of the blower 100. Alternatively the ring magnet 446 may be a sintered NdFeB rare earth ring magnet. A pair of balance rings 441 are attached to the shaft at respective axial ends of the ring magnet 446 to clamp the ring magnet 446 in an axial direction. A protective sleeve 448 is applied to the ring magnet 446 and the pair of balancing rings 441. The protective sleeve 448 is preferably made of stainless steel plate with a thickness of about 0.1 mm-0.3 mm, which will not significantly effect performance of the motor but has good mechanical strength to endure centrifugal and electromagnetic forces to prevent the ring magnet 446 from breaking up when the rotor 440 is rotating at high speed over 25,000 rpm (even over 40,000 rpm).

FIG. 6 illustrates an exploded view of a rotor assembly of a second embodiment with the shaft omitted. In use, the rotor assembly shown would be fitted to a rotor shaft such as shaft 442 of FIG. 5. The rotor assembly comprises a rotor core 444 which has a central hole for being press fitted onto the shaft. A ring magnet 446 is fitted to the rotor core. The ring magnet is coupled to the rotor core by a tongue and groove connection comprising two grooves 451 formed in the inner surface of the ring magnet which receive or mate with two ridges or tongues 450 formed on the outer surface of the rotor core. Of course the locations of the tongues and grooves may be reversed and the number of tongues and grooves may be different. The tongue and groove connection prevents the ring magnet from rotating about the rotor core. The axial length of the rotor core may be less than the axial length of the ring magnet such that a small chamber may be formed at each the end of the magnet once fitted to the rotor core. The balance rings each have a boss 449 which locates within a respective chamber when fitted to the rotor core. The balance rings may be pressed onto the shaft to hold the ring magnet axially with respect to the shaft and the rotor core. However, preferably the balance rings 441 are fixed to the rotor core with the bosses 449 contacting the rotor core. Fixing may be by any suitable means such as by bolts passing through the rotor core from one balance ring to the other. The protective sleeve 448 which fits over the ring magnet 446 to support the ring magnet against the forces trying to destroy the ring magnet during high speed rotation. The protective sleeve, in this embodiment, has the same axial length as the ring magnet.

The blower in accordance with the present invention is particularly suitable for air processing apparatus such as hand dryers and air cleaners.

The advantages of embodiments of the present invention include that reliability of the blower can be improved because the added protect sleeve can prevent the ring magnet from being broken and cost of the blower is low because a ring magnet made of bonded NdFeB rare earth is adopted.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

Claims

1. A blower comprising: a motor with a rotor and a stator; an impeller driven by the motor; a diffuser for directing air from the impeller; and a housing accommodating the motor, the impeller and the diffuser and having an air inlet and an air outlet, wherein the rotor comprises: a shaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotor core, and a protective sleeve tightly surrounding the ring magnet.

2. The blower of claim 1, wherein the protective sleeve is made of metal.

3. The blower of claim 2, wherein the protective sleeve is made of stainless steel plate.

4. The blower of claim 1, wherein thickness of the protective sleeve is between 0.1 mm and 0.3 mm.

5. The blower of claim 1, wherein the ring magnet is a bonded NdFeB rare earth ring magnet.

6. The blower of claim 1, wherein the ring magnet is a sintered NdFeB rare earth ring magnet.

7. The blower of claim 1, wherein the rotor has a pair of balance rings that press against the axial ends of the ring magnet to prevent axial movement of the ring magnet with respect to the rotor core.

8. The blower of claim 7, wherein the ring magnet has an axial length that is longer than the axial length of the rotor core and each of the balance rings has a boss that locates within the respective axial end of the ring magnet.

9. The blower of claim 1, wherein the ring magnet is keyed to the rotor core by a tongue in groove connection to prevent rotation of the ring magnet about the rotor core.

10. The blower of claim 1, wherein the diffuser is disposed between the impeller and the motor for directing air from the impeller to the motor via a plurality of air passages and wherein the diffuser supports a bearing for the shaft.

11. The blower of claim 1, wherein the rotor is configured to rotate at a speed greater than 25,000 rpm, preferably greater than 40,000 rpm.