Patent US5268607 - Molded resin motor housing

1 2

FIG. 2 is a cross-sectional end view of the same as

MOLDED RESIN MOTOR HOUSING sembly along line 2—2 of FIG. 1 also showing flange

portions in phantom line.

TECHNICAL FIELD FIG. 3 is a cross-sectional view of the assembly taken

... . A . « i . • , 5 along line 3—3 of FIG. 2.

My mvention relates to small electric motors having pfG 4 .g a , ^ vjew Qf ^

cup-shaped housings and, in particular, to direct current ... tQ a w^dshield wi drive casti

(DC) motors with permanent magnets and of the type FIG 5 is a simplified croSs-sectional view through an

used to power auxiliary systems in automobiles. injection mold for making the assembly.

BACKGROUND OF INVENTION 10 DETAILED DESCRIPTION

Small electric motors are used for many purposes in A windshield wiper motor housing assembly 10 is automobiles. For example, a fully equipped automobile illustrated in FIGS. 1 through 3 as a preferred embodiincludes individual motors for powering each wind- ment of my invention. The assembly 10 includes a cupshield wiper system, fan, and window lift system and 15 shaped housing 12 having an open end 14 and a closed three additional motors for powering each adjustable end 16. The housing 12 is molded of a resin material seat. Electric motors are also used as sunroof, mirror, such as AMODEL A-1565 HS NT from Amoco Perand antenna drives. formance Products, Inc. of Atlanta, Ga. The preferred

Ordinarily, these motors have metal housings that are resin is a sixty-five percent glass and mineral reinforced

formed from drawn steel cans. C-shaped permanent 20 polyphthalamide that exhibits high stiffness and good

magnets are attached to the sides of the can with adhe- dimensional stability at elevated temperatures,

sives, clips, or screws that are tapped into the magnets. An armature bearing 18 in the form of a thin sleeve

The steel body of the can functions as a flux ring sur- havin8 inner and «"« cylindrical surfaces 20 and 22 is

rounding the magnets. A self-centering bearing is molded m place withm the closed end 16 of the housing.

«„j „. „ „i„„„j J „f,i„ „„„ „„j „<• „„„„ 25 The armature bearing 18 is also preferably made of a

mounted at a closed end of the can. One end of an arma- ^ . , , °___T *,_„,. ,' ^

. f. . • , . . . , . resin material such as TORLON 4203L from the same ture shaft is journaled in the bearing, and the armature . „ _,, - , ^ . , ... u a. v ".-i* J -.i. .i. u ■ . i- . •.. manufacturer. The preferred resin material of the annashaft can be tilted with the bearing into alignment with „ , ... , -j • j .i_ . fi_-.fi.

, . , . , r 6 ture bearing 18 is a polyamide-imide that exhibits high

another bearing earned m a housing cover th Jd wear ^J^nce at elevated temperatures,

The drawn steel cans are expensive and add consider- 3Q ]ow ... and a w he_ meUi im than thfi fesin

able weight to the motors. The self-centenng beanngs material of the housing 12 t0 permit the armature bear,

also add cost and require additional clearance between ing t0 be molded in piace within the housing.

the armature and the permanent magnets to align the A flange M is molded at the open end 14 of the hous

armature shaft between the bearings. The additional mg for mounting the housing assembly 10 on a cover

clearance detracts from motor performance. 35 portion 26 of a wiper drive casting 28 shown in FIG. 4.

SUMMARY OF THE INVENTION Mounting holes 30 are formed through the flange 24 for

aligning the housing assembly 10 with similar mounting

My new electric motor housing assembly overcomes holes formed in the cover portion 26. Fasteners 32 in the problems with prior drawn steel housings by replacing form of screws or rivets extend through the mounting the steel housings with resin housings and feromagnetic 40 holes in the flange 24 and cover portion 26 for attaching flux rings. The resin material weighs much less than the the housing assembly 10 to the wiper drive casting 28. steel and can be more easily formed to a desired shape. Both the mounting holes 30 and the inner cylindrical The flux rings are also much easier to form. In addition, surface 20 of the armature bearing are molded within armature bearings and magnet mounts can be molded in the housing 12 in positions that are centered with redesired positions within the housing. 45 spect to a central axis 34. This eliminates the need for

One example of my motor housing assembly includes angularly adjusting the armature bearing into alignment

a cup-shaped housing that is injection molded from a w'tn tne central axis.

resin material. A flux ring is molded in place within a A steel flux rinS 38 als0 having inner and outer cylm"

center portion of the housing; an armature bearing is drical surfaces 40 and 42 is mounted in place within the

molded in place within a closed end of the housing; and 50 houslnS 12 Preferably, the flux nng 38 is molded in

alignment elements for mounting a housing cover are Plaf m * P0TM I ""^ ...

molded in place within an open end of the housing. surfa5f £ °? the flu,x ... f ^central

., . . ,, , , ■ .if 3X15 34. The inner cylmdncal surface 40 of the flux nng

Also, protrusions are molded through openings in the ., _r * 1 «•

flux n for h ldin erman nt ma nets in lace provides a mounting surface for locatmg a pair of per

ux nng or o mg permanen magne s in p ace J5 manent magnets 44 and 46 within the housing assembly

against the flux nng. 10. Since the inner cylindrical surfaces 20 and 40 of the

Inner cylmdncal surfaces of both the flux nng and beari and flux nng can be mounted mde

the armature beanng are centered wnhin the housing dent of any diametrai variations of their respective

with respect to alignment elements. This helps to re- outer cyiindncai surfaces 22 and 42, a gap between an

duce runout of a motor armature and assures a precise ^ armature coil (not shown) and the permanent magnets

positional relationship between the armature and the 44 and 46 can be reduced for improving motor perfor

magnets. Motor performance is improved by reducing mance.

an amount of clearance space between the armature and A slot 48 is formed through the periphery of the flux

the magnets. ring 38 to provide some mounting flexibiliy for molding

DRAWINGS ^5 t'le ^UX nn^ w'l^'n nousmS 12. A series of apertures

50 are also formed through the flux ring in positions

FIG. 1 is an perspective view of my new motor hous- diametrically opposed to the slot 48. Respective protru

ing assembly. sions 52 and 54 are molded through the slot 48 and the

apertures 50 for holding the magnets 44 and 46 in place against the flux ring 38. The magnets 44 and 46 can be inserted between the protrusions 52 and 54 through the open end 14 of the housing.

The protrusions 52 and 54 are shaped to grip opposite 5 sides of the magnets 44 and 46 similar to a dovetail fastener for press fitting the magnets against the flux ring 38. Molded stop lands 56 hold the magnets 44 and 46 in place against movement toward the closed end 16 of the housing. The flux ring 38 is also made with tabs 10 58 that can be folded against ends of the magnets 44 and 46 for preventing movement of the magnets toward the open end 14 of the housing. Alternatively, the protrusions could be formed with tapers to secure the magnets against such movement with an interference fit. 15

Openings 60 are formed through an exterior surface of the housing 12 for exposing the outer cylindrical surface 22 of the flux ring to atmosphere. Any excess heat retained in the flux ring is dissipated to the atmosphere through the openings 60. A vent 62 permits air circulation between an interior of the housing 12 and the atmosphere.

The motor housing assembly 10 of FIGS. 1 through 3 is connected in FIG. 4 to the wiper drive casting 28. A second armature bearing 68 is mounted in the casting 28 for rotatively supporting an armature shaft 70 that extends through the cover portion 26. The two armature bearings 18 and 68 are aligned with each other and the central axis 34 by the fasteners 34. A worm gear 72 is 3Q fashioned at the end of the armature shaft 70 for driving a worm wheel 74. A shaft 76 driven by the worm wheel 74 rotates a crank arm 78 of a wiper linkage mechanism (not shown). Brackets 80 mount the wiper drive casting 28 in a vehicle. 35

The housing 12 is preferably injection molded within a mold cavity formed by mold parts such as those shown in FIG. 5. The mold includes top and bottom halves 82 and 84. The top half 82 includes a machined portion 86 that forms the closed end 16 of the housing ^ and two slide portions 88 and 90 that form the housing periphery. The bottom half 84 of the mold includes a machined portion 92 that forms the open end 14 of the housing and a core portion 94 that forms the housing interior. 45

The top and bottom mold halves 82 and 84 are relatively movable in the directions indicated by arrow 96, and the two slide portions 88 and 90 are relatively movable in the directions indicated by arrows 98 and 99 for exposing the core portion 94. The armature bearing 18 50 is mounted on a small diameter section of the core portion 94, and the flux ring 38 is mounted on a concentric large diameter section of the core portion 94. The machined portion 92 of the bottom mold half includes posts 100 for forming the mounting holes 30 in positions 55 that are centered with respect to a central axis 102, which is also the central axis of the core portion 94. Accordingly, the inner cylindrical surfaces 20 and 40 of the armature bearing and flux ring, as well as the mounting holes 30 of the flange, are centered with respect to 60 each other within the bottom mold half 84.

Recesses 104 and 106 in the core portion 94 form the protrusions 52 and 54. Slot 48 and apertures 50 permit resin to flow through the flux ring 38 into the recesses 104 and 106 for forming the protrusions 52 and 54. 65 Projections (not shown) on the slide portions 88 and 90 form openings in the housing for exposing portions of the flux ring to atmosphere.

A sprue 108 in the machined portion 86 of the top mold half provides an opening for injecting fiber-filled resin material into the mold. The sprue is aligned with an end of the core portion 94 to introduce turbulence within the resin for better distributing the fibers throughout the mold. After the resin has sufficiently cooled, the slide portions 88 and 90 are opened and the top and bottom mold halves 82 and 84 are separated for removing the molded housing assembly 10 from the core portion 94.

Although my invention has been described for use in a windshield wiper motor, my invention can also be used to provide an improved motor housing assembly for other automotive systems as well as other types of systems that are adaptable for similar improvements.

I claim:

1. An electric motor housing assembly comprising: a molded motor housing having a central axis and

open and closed ends; a flux ring having an inner cylindrical surface and an outer surface and being molded in place within said housing;

an armature bearing having an inner cylindrical surface and an outer surface and being molded in place within said closed end of the housing;

alignment elements for mounting a cover being molded in place at said open end of the housing;

said inner cylindrical surfaces of the flux ring and the armature bearing being molded within said housing in positions defined by different portions of a single mold core parts; and

said inner cylindrical surfaces of the flux ring and the armature bearing, together with said alignment elements, being molded within said housing in positions that are centered with respect to said central axis independently of said outer surfaces of the flux ring and the armature bearing.

2. The assembly of claim 1 further comprising: openings formed through said flux ring between said

inner and outer surfaces of the flux ring; said motor housing including protrusions molded

through said openings in the flux ring; and said protrusions being shaped for securing said flux

ring to said motor housing and for holding magnets

in place against said flux ring.

3. The assembly of claim 2 in which said protrusions are molded as fasteners for press fitting the magnets in place against said flux ring.

4. The assembly of claim 3 in which said flux ring includes tabs that can be folded against ends of the magnets for holding the magnets in place against movement toward said open end of the housing.

5. The assembly of claim 2 in which a flange is molded at said open end of the housing and said alignment elements are holes formed through said flange.

6. The assembly of claim 2 in which said housing is molded from a first resin material.

7. The assembly of claim 6 in which said housing includes an exterior surface and openings molded in said housing for exposing said flux ring within said exterior surface.

8. The assembly of claim 6 in which said armature bearing is made from a second resin material having a melting temperature above that of the first resin material.

9. The assembly of claim 8 in which said first resin material is a polyphthalamide.

5 6

10. The assembly of claim 8 in which said second 14. The housing of claim 13 in which said main body resin material is a polyamide-imide. is molded with stop lands for holding the magnets in

11. A housing for an electric motor comprising: Place against movement toward said closed end of the

a main body molded from a resin material; mam body. . _ .

a magnetic flux ring molded in place within said main 5 . \S-The of cl*lm " TM whlch ^id flux nng

, ° includes tabs that can be folded against ends of the

., y' . _ , magnets for holding the magnets in place against movesaid magnetic flux ring having an inner cylindrical ment toward said open end of the main body

surface and an outer surface that is contiguous with 16 The housing of claim 13 further comprising an

said main body; 10 armature bearing having an inner cylindrical surface

openings formed through said magnetic flux ring and an outer surface and being molded in place within

between said inner and outer surfaces of the flux said closed end of the main body.

ring; 17. The housing of claim 16 in which said inner cylin

said main body of said resin material including pro- drical surfaces of the flux ring and the armature bearing

trusions molded through said openings in said flux 15 are molded within said main body in positions defined

ring; and t>v different portions of a single old core part,

said protrusions being shaped for securing said flux 18- T,he housing of claim 16 further comprising align

ring to said main body and for holding magnets in ment eleme"ts for counting a cover being molded in

, . . ., _ . place at said open end of the main body.

place against said flux ring. 2Q 19. The housing of claim 18 in which ^ mner cyim.

12. The housing ot claim 11 in which said protrusions drical surfaces of the flux

ring and armature bearing,

are molded as fasteners for press fitting the magnets t0gether with said alignment elements, are centered in

against said flux ring. the mam body with respect to said central axis indepen

13. The housing of claim 11 in which said main body . dently of said outer surfaces of the flux ring and the includes a central axis and is molded with an open end 25 armature bearing.

and a closed end. *****

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Patente

Molded resin motor housing