WO1997018614A1

WO1997018614A1 - Motor having bearing assembly with alignment surface which contacts surface of stator within stator bore

Info

Publication number: WO1997018614A1
Application number: PCT/US1996/018163
Authority: WO
Inventors: Deno J. Rogakos; Craig A. Ham; Ralph J. Unterborn
Original assignee: Itt Automotive Electrical Systems, Inc.
Priority date: 1995-11-14
Filing date: 1996-11-13
Publication date: 1997-05-22
Also published as: EP0861516A1

Abstract

A motor includes a stator having a stator bore defined therein, the stator having a linear surface within the stator bore which spans the entire length of the stator. The motor further includes a rotor positioned in the stator bore. The motor additionally includes a bearing assembly positioned to contact the linear surface of the stator, wherein (1) the bearing assembly has a support surface for rotatably supporting the rotor, and (2) the support surface is fixed in relation to the stator so that no relative movement occurs between the support surface and the stator. A method of positioning a rotor within a stator bore of a stator is also disclosed.

Description

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OTOR HAVING BEARING ASSEMBLY WITH ALIGNMENT SURFACE WHICH CONTACTS SURFACE OF STATOR WITHIN STATOR BORE

Background of the Invention The present invention generally relates to electric motors, and more particularly relates to an apparatus and method for rotatably mounting a rotor within a stator bore.

Various electric motor designs include a stator having a cylindrical bore therethrough. An end cap assembly is mounted on each end of the stator. The end cap assembly may be comprised of multiple parts. Each end cap assembly is usually secured to a surface on a respective end face of the stator. Each end cap assembly provides a bearing surface on which the rotor is mounted so as to be rotatably supported within the stator bore. Alignment of the rotor relative to the stator bore is a critical feature in certain types of motors. For example, in motors which have a very small air gap (such as 0.005 inch) between the rotor and the stator, a 0.001 inch variation in this air gap size would represent a 20% variation in the air gap. Such a variation would significantly impact torque production of the motor.

Accurate alignment of the rotor relative to the stator bore has heretofore depended upon maintaining tight tolerances of the dimensions of the parts which position the rotor relative to the stator bore. These parts include all of the parts which are mechanically interposed between the stator and the rotor. Also, the physical dimensions of the stator itself would need to possess tight tolerances, with particular focus on the dimensions of the stator end faces relative to the stator bore . It would therefore be desirable to provide a motor which has accurate alignment of the rotor relative to the stator bore that is inexpensive to manufacture. It would further be desirable to provide a motor which has accurate alignment of the rotor relative to the stator bore that facilitates ease of assembly.

Summary of the Invention In accordance with one embodiment of the present invention, there is provided a motor which includes a stator having a stator bore defined therein, the stator having a linear suri ace within the stator bore which spans the entire length of the stator. The motor further includes a rotor positioned m the stator bore. The motor additionally includes a bearing assembly positioned to contact the linear surface of the stator, wherein (1) the bearing assembly has a support surface for rotatably supporting the rotor, and (2) the support surface is fixed m relation to the stator so that no relative movement occurs between the support surface and the stator.

Pursuant to another embodiment of the present invention, there is provided a method of positioning a rotor within a stator bore of a stator, with the stator having a linear surface withm the stator bore which spans the entire length of the stator. The method includes the steps of: (1) providing a bearing assembly having an alignment surface and a support surface, (2) positioning the alignment surface n contact with the linear surface of the stator, (3) supporting the rotor with the support surface, and (4) maintaining the support surface fixed in relation to the stator so that no relative movement occurs between the support surface and the stator. According to yet another embodiment of the present invention, there is provided a motor which mcludes a stator having a stator bore defined therein, the stator having a linear surface withm the stator bore which spans the entire length of the stator. The motor further mcludes a rotor positioned in the stator bore. The motor additionally includes a bearing assembly having an alignment surface and a support surface, wherein (1) the alignment surface is secured to the linear surface of the stator, and (2) the support surface rotatably supports the rotor.

It is therefore an object of the present invention to provide a new and useful motor.

It is another object of the present invention to provide an improved motor.

It is moreover an object of the present invention to provide a new and useful method of positioning a rotor within a stator bore of a stator. It is still another object of the present invention to provide an improved method of positioning a rotor within a stator bore of a stator.

It is also an object of the present invention to provide a motor which provides accurate alignment of a rotor relative to a stator bore that is inexpensive to manufacture.

It is still another object of the present invention to provide a motor which provides accurate alignment of the rotor relative to the stator bore that facilitates ease of assembly. The above and other objects, features, and advantages of the present invention will become apparent from the following description and attached drawings. Brief Description of the Drawings Fig. 1 is a fragmentary cross-sectional view of a first embodiment of an electnc motor which incorporates the features of the present invention therein;

Fig. 2 is an enlarged view of a portion of Fig. 1 which is encircled and indicated as Fig. 2;

Fig. 3 is a fragmentary cross-sectional view of a linear surface of the stator of Fig. 1; Fig. 4 is a fragmentary cross-sectional view of a second embodiment of an electric motor which incorporates the features of the present invention therein; and

Fig. 5 is an enlarged view of a portion of Fig. 4 which is encircled and indicated as Fig. 4.

Detailed Description of the Preferred Embodiment

While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling with the spirit and scope of the invention as defmed by the appended claims.

Referring to Fig. 1, there is shown a first embodiment of an electric motor 10 which incorporates the features of the present invention therein. The motor 10 mcludes a stator 12 having a stator bore 14 defmed therein. The stator 12 includes a plurality of intermediate lamina segments 13 and an end lamina segment 15 positioned at each end thereof (only one end lamina segment 15 is shown in Fig. 1) . Each of the plurality of intermediate lamina segments 13 is made from a low carbon steel or a silicon steel. Each of the end lamina segments 15 is made from aluminum or a non-magnetic stainless steel. It should be noted that the end lamina segments 15 are made from a material which has relatively low permeability in relation to the permeability of the material from which the mtermediate lamina segments 13 are made. The motor 10 further mcludes a rotor 16 which is positioned withm the stator bore 14. An air gap (not shown) is located between the rotor 16 and the stator 12. In operation, the rotor 16 rotates with respect to the stator 12. The rotor 16 mcludes a rotor bore 17. A sleeve bearing 19 is mounted to the rotor 16 withm the rotor bore 17 as snown in Fig. 1. The sleeve bearing 19 rotates along with the rotor 16 during operation of the motor 10.

The motor 10 additionally mcludes a bearing assembly 18. The bearing assembly may be made from an anodized alummum material. As shown Fig. 2, the bearing assembly 18 includes an alignment surface 20 which contacts a linear surface of the stator 12 withm the stator bore 14. The linear surface of the stator 12 spans the entire length of the stator. What is meant herein by the phrase "the stator has a linear surface withm the stator bore which spans the entire length of the stator" is that the stator 12 possess a surface S positioned withm the stator bore 14 in which a cross- section thereof would define a line which extends from one end of the stator 12 to the other end of the stator as shown in Fig. 3. Note that surface S does not possess any notches or apertures defmed at any position along its entire length including its end portions. The bearing assembly 18 further mcludes a support member 22 having a support surface 24. The support member 22 of the bearing assembly 18 is positioned withm the rotor bore 17 so as to contact the sleeve bearing 19 as shown m FIGS. 1 and 2. As positioned above, the rotor 16 is rotatably supported on the support surface 24 of the support member 22 with the stator bore 14.

It should be noted that the contact of the alignment surface 20 with the linear surface S of the stator 12 within the stator bore 14 positions the support surface 24 of the support member 22 relative to the linear surface S of the stator 12 within the stator bore 14. The bearing assembly 18 is secured to the stator 12 so that the alignment surface 22 and the support surface 24 are fixed in relation to the stator 12 so as to prevent relative movement between the stator 12 and the alignment surface 22, as well as between the stator 12 and the support surface 24.

Referring now to Fig. 4, there is shown a second embodiment of an electric motor 30 which incorporates the features of the present invention therein. The motor 30 mcludes a stator 32 having a stator bore 34 defmed therein.

The stator 32 includes a plurality of intermediate lamina segments 33 and an end lamina segment 35 positioned at each end thereof (only one end lamina segment 35 is shown in Fig. 4) . Each of the plurality of intermediate lamina segments 33 is made from a low carbon steel or a silicon steel. Each of the end lamina segments 35 is made from aluminum or a non-magnetic stainless steel. It should be noted that the end lamina segments 35 are made from a material which has relatively low permeability in relation to the permeability of the material from which the intermediate lamina segments 33 are made.

The motor 30 further includes a rotor 36 which is positioned with the stator bore 34. An air gap (not shown) is located between the rotor 36 and the stator 32. In operation, the rotor 36 rotates with respect to the stator 32.

The motor 30 additionally includes a bearing assembly 38. As shown in Fig. 5, the bearing assembly 38 mcludes an inner race 40, an outer race 42 and a plurality of ball bearings 44. The outer race 42 is secured to the stator 12 while the inner race 40 is secured to the rotor 36. The plurality of ball bearings 44 are secured between the inner race 40 and the outer race 42.

The outer race 42 mcludes an alignment surface 46 and a support surface 48. The alignment surface 46 contacts a linear surface of the stator 32 within the stator bore 34. The linear surface of the stator 32 spans the entire length of the stator. The linear surface of the stator 32 has similar characteristics to the linear surface S of the stator 12 discussed above with regard to motor 10 of FIGS. 1-3. The support surface 48 supports the ball bearings 44 and the inner race 40, which in turn supports the rotor 36. As arranged above, the rotor 36 is rotatably supported within the stator bore 3 .

It should be noted that the contact of the alignment surface 46 with the linear surface of the stator 32 within the stator bore 14 positions the support surface 48 of the outer race 42 relative to the linear surface of the stator 32 within the stator bore 3 . The outer race 42 of the bearing assembly 38 is secured to the stator 32 so that the alignment surface 46 and the support surface 48 are fixed in relation to the stator 32 so that no relative movement occurs between the stator 32 and the alignment surface 46, as well as between the stator 32 and the support surface 48.

While the invention has been illustrated and described in detail in the drawings and foregomg description, such illustration and description is to be considered as exemplary and not restrictive character, it being understood that only the preferred emoodiments have been shown and described and that all changes and modifications that come withm the spirit of the invention are desired to be protected.

Claims

What is claimed is:

1. A motor, comprising: a stator having a stator bore defmed therein, said stator having a linear surface withm the stator bore which spans the entire length of said stator; a rotor positioned in the stator bore; and a bearing assembly positioned to contact the linear surface of said stator, wherein (1) said bearing assembly has a support surface for rotatably supporting said rotor, and (2) the support surface is fixed in relation to said stator so that no relative movement occurs between the support surface and said stator.

2. The motor of claim 1, wherein: said rotor has a rotor bore defmed therein, and said bearing assembly includes a support member which defines the support surface, and said support member is positioned the rotor bore.

3. The motor of claim 2, further comprismg a sleeve bearing secured to said rotor within the rotor bore, wherem: the support surface of said bearing assembly contacts said sleeve bearing.

4. The motor of claim 3, wherein: said bearing assembly mcludes an alignment surface which contacts the linear surface of said stator, and said alignment surface positions the support surface of said bearing assembly relative to the linear surface of said stator within the stator bore.

5. The motor of claim 1, wherein said bearing assembly includes: an outer race which contacts the linear surface of said stator, the outer race defining the alignment surface and the support surface, an inner race secured to the rotor, and a plurality of ball bearings secured between the outer race and the inner race.

6. The motor of claim 1, wherein the stator includes: a plurality of mtermediate lamina segments, and an end lamina segment positioned adjacent to one of said plurality of intermediate lamina segments, said end lamina segment having relatively low permeability in relation to the permeability of the intermediate lamina segments.

7. The motor of claim 6, wherein said bearing assembly mcludes an alignment surface which contacts the end lamina segment.

8. The motor of claim 1, wherein: the stator includes a plurality of intermediate la ma segments, an interface is mechanically interposed between the plurality of intermediate lamma segments and said bearing assembly, and the interface has relatively low permeability n relation to the permeability of the intermediate lamma segments.

9. A method of positioning a rotor withm a stator bore of a stator, with the stator having a linear surface within the stator bore which spans the entire length of the stator, comprising the steps of: providing a bearing assembly having an alignment surface and a support surface; positioning the alignment surface in contact with the linear surface of the stator; supporting the rotor with the support surface; and maintaining the support surface fixed in relation to said stator so that no relative movement occurs between the support surface and said stator.

10. The method of claim 9, further comprising the steps of: providing a rotor bore with the rotor; providing the bearing assembly with a support member which defmes the support surface; and positioning the support member within the rotor bore.

11. The method of claim 10, further comprising the steps of: securing a sleeve bearing to the rotor within the rotor bore; and positioning the support member within the sleeve bearing.

12. The method of claim 9, wherein the bearing assembly includes an outer race, an inner race and a plurality of ball bearings, and further comprising the steps of: securing a portion of the outer race to the linear surface of the stator; securing the inner race to the rotor; and securing the plurality of ball bearing between the outer race and the inner race.

13 . A motor , comprising : a stator having a stator bore defmed therein, said stator having a linear surface withm the stator bore which spans the entire length of the stator; a rotor positioned in the stator bore; and a bearing assembly having an alignment surface and a support surface, where (1) the alignment surface is secured to the linear surface of the stator, and (2) the support surface rotatably supports said rotor.

14. The motor of claim 13, wherein: said rotor has a rotor bore defmed therein, and said bearing assembly mcludes a support member which defines the support surface, and said support member s positioned in the rotor bore.

15. The motor of claim 14, further comprising a sleeve bearing secured to said rotor within the rotor bore, wherein: the support surface of said bearing assembly contacts said sleeve bearing.

16. The motor of claim 15, wherein said alignment surface positions the support surface of said bearing assembly relative to the linear surface of said stator.

17. The motor of claim 13, wherein said bearing assembly includes: an outer race which contacts the linear surface of said stator, the outer race defining the alignment surface and the support surface, an inner race secured to the rotor, and a plurality of ball bearings secured between the outer race and the inner race.

18. The motor of claim 13, wherein the stator includes: a plurality of intermediate lam a segments, and an end lamma segment positioned adjacent to one of said plurality of mtermediate lam a segments, said end lamma segment having relatively low permeability in relation to the permeability of the intermediate lamina segments.

19. The motor of claim 18, wherein said bearing assembly includes an alignment surface which contacts the end lam a segment.

20. The motor of claim 13, wherein: the stator mcludes a plurality of intermediate lamma segments, an interface is mechanically interposed between the plurality of intermediate lam a segments and said bearing assembly, and the interface has relatively low permeability in relation to the permeability of the intermediate lam a segments.