JPH0479221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to small electric motors of the type commonly used in axial air impeller devices found in computers, copiers, and the like. In particular, the present invention
An improved molded plastic housing with at least one radial end wall and an axial extension serving as a mount for an annular stator, as well as a housing for a central shaft and its bearings. This central axis is operatively associated with an annular rotor of the motor disposed diametrically outwardly of the stator and in the center of the stator, and may include a rotor of the permanent magnet type.

BACKGROUND OF THE INVENTION In a construction with an air impeller in which a small electric motor is associated, a rotor with permanent magnet elements is arranged diametrically outwardly of the rotor and rotatably driven by the rotor, and the rotor comprises a permanent magnet element. A molded plastic air impeller may be provided to force air to flow axially through the interior.

In motor and housing constructions of the type described above, it is common practice to provide a metal insert within the axial plastic housing extension for receiving and retaining the bearing that pivots the central motor shaft. Although such a structure is generally satisfactory, it lacks economy, ease of assembly,
Lacks convenience. This is particularly disadvantageous for small, high capacity motor and air impeller systems where every cent saved is highly desirable.

PROBLEM SOLVED BY THE INVENTION It is an overall object of the invention that an elongated body extending integrally axially from a radial end wall of the housing acts as a stator mount and a pivoting element for the shaft; An object of the present invention is to provide an improved molded plastic housing in which the bearings are fitted and held directly within the elongated body of the housing, so that a reliable yet resilient bearing seat can be provided very economically.

Another object of the invention is to effectively align and maintain bearings, significantly facilitating assembly;
It is also an object to provide an improved molded plastic housing of the type described above which provides improved damping of vibration and noise transmission.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention includes an annular stator and a rotor arranged diametrically inside and outside, and an annular stator and a rotor operably associated with the rotor. A molded plastic housing for a compact electric motor that rotates and has a central shaft diametrically disposed within the rotor is provided. The housing includes at least one radially extending end wall, a centrally positioned, integrally molded stator housing, and a tubular housing portion that pivots on a shaft extending radially from the end wall. ing. The radially extending tubular housing portion has intermediate axially spaced ends. First and second bearings are each provided at one of the ends to rotatably receive and retain the shaft. The flexibility of each of the ends is increased by at least three axially extending thinned regions spaced along the circumference of the shaft. The length of this thinned region is approximately equal to the length of the associated bearing within the end. The bearing fits in the end of the tubular portion extending in an interference fit at least in the thin region. At least in the thin region, the inner diameter of the tubular extension is made slightly smaller, so that the bearing and the tubular extension housing portion are interference fitted in this thin region. In this manner, the bearing is efficiently maintained in axial alignment even when there is a slight difference in tolerance between the outer diameter of the bearing and the inner diameter of the end.

The thinned region at the end of the tubular elongated housing section and the reduced diameter provide the flexibility necessary to receive the bearing in an interference fit;
Moreover, the structural integrity of the tubular elongated housing portion is maintained, thereby providing an effective attachment to the annular stator. That is, the stator can be mounted on and around the tubular elongate housing portion and securely held in place. If desired, the axial circumferential positioning of the stator can be facilitated by the provision of small axial ribs extending outwardly from the tubular elongated housing portion.

Reducing the diameter of the end of the elongated tubular housing portion can be achieved by providing a thinner region with a small flat portion extending along the inner diameter of the elongated tubular housing portion. The outer diameter surface of the bearing engages this flat surface, so that the bearing is held elastically and reliably, and the bearing can be easily aligned in the axial direction. The tubular elongated housing portion may also be formed with a small shoulder portion to position the bearings axially relative to and relative to the shaft in which they are receivable.

Examples Preferred embodiments of the present invention will be described below. Referring to FIGS. 1 to 3, the illustrated motor/air impeller unit has a total of 10 units.
It includes a substantially rectangular housing indicated by , an air impeller having a plurality of air moving blades 12, 12 (five shown in the drawing), and a rotor 14. The rotor 14 includes a cup-like member for mounting an annular permanent magnet rotor 16, which cup-like member is operatively secured to a second cup-like member 18 for mounting the axial air movable vanes 12, 12. . In FIG. 2, the shaft 20 is attached to the inside or center of the cup-shaped member and extends downward in a cantilevered manner. The shaft 20 is journaled in first and second bearings, or front and rear bearings 22,24. These bearings 22, 24 are axially spaced apart within a housing section generally indicated at 26 and extend axially from a radial housing section 28 in FIG. The radial housing portion 28 includes spoke-like components 30,
30 to the rectangular outer housing portion. Thus, the motor and fan are held in appropriate positions within the shroud.
This shroud has a cylindrical shape as shown in FIGS. 1 and 4.

The radial housing portion 28 has a generally cup-like shape as shown, and has a printed circuit board 3 therein.
4 are arranged. In addition, the motor stator 36
are mounted on and around the tubular housing portion 26. Therefore, the tubular housing part 2
6 must have the necessary structural rigidity to support the stator 36, and must also provide a resilient yet secure housing for the bearings 22, 24 that it receives and directly holds. .

As shown in FIGS. 3 and 4, a tubular housing portion 26 is integrally formed with a radial housing portion 28 and is centrally located within and extends axially from the housing portion 28. There is. The tubular housing portion 26 has an intermediate portion 38 and opposite ends 40, 40 which serve to receive and retain the bearings 22, 24.

According to the invention, each of the ends 40, 40 has its flexibility enhanced by at least three axially extending thinned regions spaced apart along the axial circumference. It has been increased. As shown, four such reduced-diameter thinner regions are preferably provided, and slots 42, 42 are preferably provided as shown in FIGS. 4 and 5. These slots 42, 42
opens radially outward as shown, and
As shown in FIGS. 3 and 4, the ends are open in the axial direction. As shown in the figure, the thickness of the tubular housing portion 26 is approximately 1/2 or more of that of the slots 42, 42. According to the invention, this degree of thinning is at least one-half the thickness of the tubular elongated housing part.

The axial dimensions of the slots can vary, but are preferably no more than 1/3 of the circumference of the tubular elongate housing section, and as shown, each Approximately 1/4
Preferably, there are four slots 42, 42 extending across. Due to the dimensional relationship mentioned above,
Additionally, by using a molded plastic housing made from polybutylene terephthalate,
The bearings 22 and 24 have a desired degree of elasticity and can be held securely. Bearing 2
2 and 24 include conventional rolling bearings, sleeve bearings, and the like.

By forming molded shoulder portions 44, 44 within tubular elongate housing portion 26, bearings 22,2
4 can be easily positioned accurately in the axial direction. As is well known, a degree of precision in the molding process can provide a precise, square shoulder portion and improve the degree of alignment of the bearing. As shown in FIG.
By interfering with the slightly reduced diameter portion of the bearing, it is possible to hold and align the bearing. In particular, the inner diameter surface 46 of the tubular elongate housing portion 26 is diametrically constricted slightly at the regions or slots 42,42. As shown in FIG. 5, flat portions 48, 48 are provided for this purpose. Alternatively, of course, the reduction in diameter is also possible by providing a region of somewhat larger diameter in the middle of the slots 42,42. In either case, the bearing 2 shown in FIG.
2 includes at least four flat portions 48, 4 of FIG.
8, and the opposite or rear bearing 24 is similarly mounted in axial alignment with these flats. At the rear of the shaft 20, a snap ring 50 engages the rear bearing 24 and secures it in a convenient position, and a disc bearing 52 on the front of the shaft connects the bearing 22 and the central hub portion 54 of the cap-like member. and then the bearing 2
2 is fixed in a convenient position relative to its seat portions 44,44.

The stator 36 is mounted on and around the tubular housing section 26 and provides the necessary strength of the tubular elongate housing section by substantially thickening the walls of the intermediate section 38 and between the slots 42, 42. and rigidity can be obtained. Additionally, the structural integrity of the tubular housing portion 26 with respect to the radial housing portion 28 is such that the fin-like component 5 has a substantial thickness.
6, 56, these fin-like elements 56, 56 connect the tubular housing part 26 to the radial housing part 28 at the slots 42, 42.

As shown in the drawings, slots 42, 42 are axially aligned in the embodiment disclosed in FIGS. 1-5. In the optional embodiment of FIGS. 6-8, slots 42a, 42a are
Although substantially identical to the slots 42, 42 described above, the front portion of the tubular housing portion 26a is offset in the axial circumferential direction with respect to the slots 42a, 42a at the rear thereof. The tubular housing portion 26a is provided with radially extending ribs. This rib is 6
It extends in the axial direction at 2 and can be used to attach a stator to the circumference of the shaft during assembly. 8th
In the figure, the flat parts 48a, 48a are designed to be interference-fitted with the bearings installed in the tubular housing part, as in FIG. 5, and in FIGS. Similarly, shoulder portions 44a, 44a are provided.

From the above discussion, it will be appreciated that molded plastic housings can utilize plastic materials such as polybutylene terephthalate to provide the robustness, stiffness, strength, etc. necessary for the construction of air impellers for small motors of the type described above. Such plastics are relatively resistant to attack by chemicals, water, oil, etc., and are also excellent electrical insulators. this is,
This is an important point in constructing a small air impeller unit. Plastics also significantly dampen vibration and noise transmission;
It can be manufactured by an economical molding method.
The bearing of the present invention is resiliently and firmly held in alignment and direct engagement with the tubular housing portion, resulting in a relatively simple assembly process. Additionally, the bearings effectively align and maintain alignment while providing the structural integrity necessary for mounting the tubular stator. In this way, it is possible to assemble a small motor efficiently, to have excellent operational efficiency, and to construct it extremely economically.

[Brief explanation of drawings]

FIG. 1 is an elevational view of an electric motor driven axial air impeller embodying the improved motor housing of the present invention; FIG. 2 illustrates the improved housing of the present invention; The schematically enlarged vertical sectional view of the motor, impeller, and housing shown in FIG. 3 is an exploded view of the motor, impeller, and housing of FIGS. 1 and 2, with some parts omitted for convenience, and FIG. 4. FIG. 5 is a perspective view of the improved housing of the present invention showing the axially extending portion of the housing with the stator mounted and the shaft pivotally supported; FIG. A schematic enlarged end view, FIG. 6, depicts yet another embodiment of the improved housing of the present invention.
FIG. 7 is a schematic enlarged perspective view, FIG. 7 is an axial sectional view of the housing portion of FIG. 6, and FIG. 8 is an end view of the housing portion of FIGS. 6 and 7. (Explanation of main symbols), 10...Housing, 1
2... Moving blade, 14... Rotor, 18... Cup-shaped member, 20... Shaft, 22, 24... Bearing, 26...
... tubular axially extending housing portion, 28... radially extending housing portion, 36... stator, 38...
Middle part, 40...Both ends, 42...Slot, 4
8... Flat portion, 50... Snap ring, 52... Disk spring, 54... Central hub portion, 56... Fin-shaped component.

Claims (1)

[Scope of Claims] 1. An annular stator and a rotor disposed in a radially inner and outer positional relationship, and an operative relationship with the annular rotor disposed diametrically within the stator. a molded plastic housing for a small electric motor having a rotatable central shaft and at least one radially extending end wall and a centrally located integrally molded stator mount and pivotally supporting the shaft; a tubular housing portion, the tubular housing portion extending axially from the end wall, and further having opposite ends spaced apart from each other in the axial direction at an intermediate position; first and second bearings for rotatably fitting and holding the shaft, at least three diameter-reducing bearings, each of which has opposite end portions spaced apart from each other along the circumference of the shaft and extending in the axial direction; Depending on the thin area,
increasing the flexibility of the associated bearing over at least substantially the entire length thereof, each said bearing and its associated end having a tight fit, at least in said reduced diameter region, and said annular stator connected to said tubular extension; A molded plastic housing characterized by mounting over and around the housing portion. 2. Claim characterized in that the rotor is in the form of an annular permanent magnet with an operably associated air impeller arranged diametrically outwardly and rotatably driven by the rotor. Molded plastic housings for small electric motors as described in scope 1. 3. The flexibility of the bearing-receiving end is increased by forming the reduced-diameter thin region into an axially extending slot that opens radially outward and also opens the axially outer end of each end. A molded plastic housing for a small electric motor as claimed in claim 1. 4. Each end of the elongate tubular housing portion is formed with a slot equally spaced along the axial circumference and having an axially extending open end. Molded plastic housing for small electric motors as described in item 3. 5 the intermediate portion of the tubular elongated housing portion is
Claim 3, characterized in that it extends in an annular manner without interruption, with the axial ends of said slot reaching each axial end, increasing the structural integrity of said intermediate section. Molded plastic housing for small motors. 6. The small electric appliance of claim 3, wherein an axially extending slot at one end of the tubular elongate housing portion is axially aligned with a corresponding axially extending slot at the other end. Molded plastic housing for motors. 7. An axially extending slot at one end is displaced along the axial circumference and is axially misaligned with a corresponding slot at the other end of the axially extending housing part. A molded plastic housing for a small electric motor as claimed in claim 3. 8 an axially extending rib is formed along at least a portion of the tubular axially extending portion of the housing and extends radially outwardly and further engages the stator and urges the stator relative to the housing portion; A molded plastic housing for a small electric motor according to claim 3, characterized in that the housing is positioned along the circumference of the shaft. 9. A molded plastic housing for a small electric motor as set forth in claim 3, wherein the reduced thickness of each said slot is at least one-half the thickness of said tubular axially extending housing portion. 10. A molded plastic housing for a small electric motor as set forth in claim 9, wherein the thickness of each slot is approximately 1/2 or more of the thickness of the axially extending housing portion. 11. The molded plastic housing of claim 3, wherein the axial circumferential dimension of each said slot is less than one third of the circumference of said tubular elongated housing portion. 12. The small electric motor of claim 11, wherein the small electric motor defines four slots, each slot extending approximately one quarter of the circumference of the elongated tubular housing portion. Molded plastic housing. 13. The reduced diameter of the thin region is arranged in the middle of the slot on the inner diameter surface of the tubular elongate housing part, and the same number of flats as the slots are arranged in the middle of the slot and can be engaged with the outer diameter surface of the bearing. A molded plastic housing for a small electric motor according to claim 3, characterized in that it is provided by a section. 14 The plastic of said housing assembly is polybutylene terephthalate, and said rotor is in the form of an annular permanent magnet, and an air impeller is also made of said polybutylene terephthalate and is operably associated with said rotor and rotates. 4. A molded plastic housing for a small electric motor as claimed in claim 3, characterized in that it is arranged diametrically outwardly of the rotor so that it can be rotated by the rotor.