Air Cooled Rotor For Dynamo-electric Machine

Abstract

An air cooled rotor for a dynamo-electric machine having insulating members formed of plastic positioned at opposing end walls of the laminated core structure of the rotor. Each insulating member has a hollow hub which is disposed about the rotor shaft to provide an axially extending passageway having an air inlet at its outer end and a disc at its opposite inner end. The discs bear against the end walls of the core structure and provide radial passageways having their inner ends communicating with the inner ends of the axially extending passageways and their outer open ends serving as air outlets. Flow of air is induced through the axially extending and radial passageways responsive to the pressure differential of air at the inlets of the axially extending passageways and air at the outlets of the radial passageways during rotation of the rotor. The flow of air through the axially extending and radial passageways effects cooling of the dynamo-electric machine.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Dynamo-electric machines often are provided with fans for flowing air through the machines to effect cooling thereof.

2. Description of the Prior Art

It has been the practice heretofore to provide on the shaft of the rotor of a dynamo-electric machine a fan to circulate air through the machine and effect cooling thereof. The fan may be a separate unit mounted on the rotor shaft or an end plate of a core structure may be formed with fan blades to circulate cooling air through the machine. This is objectionable because the fan increases the cost of the dynamo-electric machine and also increases the weight of the rotor. Further, fans of the kind heretofore provided create turbulent air currents which often adversely affect the efficiency of the dynamo-electric machine.

SUMMARY OF THE INVENTION

It is an object of my invention to provide an improvement for air cooling the rotor of a dynamo-electric machine which eliminates the need to employ a separate fan to induce flow of air through the machine. I accomplish this by employing insulating elements at the ends of a rotor core structure which are formed of plastic and shaped to provide passageways for air having inlets and outlets for air, the air inlets being nearer to the axis of rotation of the core structure than the air outlets. The passageways in the insulating elements are developed in such manner that, when the core structure is rotating, air accelerates during its flow through the passageways with a consequent decrease in potential energy at the air outlets, so that air is discharged by centrifugal force from the air outlets at a higher velocity than the velocity at which air enters the air inlets. This is due to the pressure differential of air at the outlets and at the inlets which induces flow of air through the passageways when the core structure is rotating, such flow of air promoting cooling of the dynamo-electric machine.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing, FIG. 1 is an elevation view of a rotor of a dynamo-electric machine embodying my invention;

FIG. 2 is a front view of an end plate of the rotor shown in FIG. 1;

FIG. 3 is a side view of the end plate shown in FIG. 2;

FIG. 4 is a fragmentary rear perspective view of the end plate shown in FIGS. 2 and 3;

FIG. 5 is an enlarged sectional view taken at line 5-5 of FIG. 4;

FIG. 6 is an elevation view of a detail of the rotor shown in FIG. 1; and

FIG. 7, which is a sectional view taken at line 7-7 of FIG. 1, more or less diagrammatically illustrates the rotor to bring out details more clearly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing, I have shown my invention as applied to a rotatable member 9 of a dynamo-electric machine including a shaft 10 which is journaled for rotation and upon which is mounted a rotatable core structure 11. The core structure 11 comprises a stack of laminations 12 having spaced teeth 14 defining slots 15 arranged to receive a winding 16 having ends 17 which project beyond the opposing end walls 11a of the core structure. At one end the winding 16 is connected to a commutator 18 mounted on the shaft 10. An insulating member 19 formed of suitable plastic material is provided at each end wall 11a of the core structure 11 to support the ends 17 of the winding 16.

In accordance with my invention the insulating members 19 are formed to promote circulation of cooling air through the dynamo-electric machine. Each insulating member 19 comprises a central hollow hub 20 of cylindrical form which is fixed to the shaft 10 and a plate or disc 21 which extends radially outward from one end of the hub 20 and is normal or perpendicular to the axis of the shaft 10. The discs 21 are similar in appearance to the laminations 12 and are provided with teeth 22 defining slots 23 which are in alignment with the slots 15 of the laminations 12.

As best shown in FIG. 7, the hubs 20 of the insulating members 19 extend axially inward from regions 24 at the opposing ends of the core structure 11. The inner ends of the hubs 20, which are adjacent to the opposing end walls 11a of the laminated core structure 11, flare outward at 25 and the discs 21 project radially outward at 26 from the flared inner ends of the hubs.

The inner surfaces of the hubs 20 are formed with spaced axially extending ridges 27 which extend radially inward. The inner extremities of the ridges 27 frictionally grip the shaft 10 to hold the insulating members 19 in position at the ends of the core structure 11. The gaps formed between the ridges 27 at the inner surfaces of the hubs 20 define axially extending passageways 28 through which air is drawn inward from the regions 24 to the flared portions 25 of the hubs 20 during rotation of the core structure 12, as will be explained presently. At the inner flared portions 25 of the hubs 20 the air flowing through the passageways 28 changes its direction and flows radially outward through passageways 29 defined by the end walls 11a of the core structure and the teeth 22 of the insulating members 19 which are U-shaped in section and include closed ends 21a forming parts of the radially extending plates or discs 21 and spaced walls 21b extending therefrom toward the end walls 11a of the core structure. The outer extremities of the walls 21b physically contact the end walls 11a of the core structure to provide the radial passageways 29 from which air is discharged at openings 30 at the extreme outer ends of the teeth 22.

It will now be understood that air is drawn into the hub passageways 28 at the regions 24 at which the air inlets of the passageways 28 are located and that air is discharged from the passageways 29 at the openings 30 which serve as air outlets. When the core structure 11 is rotating during operation of the dynamo-electric machine, air accelerates during its flow through the passageways 28 and 29 with a consequent decrease in potential energy at the air outlets 30, so that air is discharged by centrifugal force from the openings 30 at a higher velocity than the velocity at which air enters the axially extending passageways 28 at the regions 24. This is due to the pressure differential of air at the discharge openings or outlets 30 and at the inlets or regions 24 which induces flow of air through the passageways 28 and 29 when the core structure 11 is rotating, such flow or circulation of air promoting cooling of the dynamo-electric machine. With this arrangement the air flowing through the passageways 29 effects cooling of the winding 16, particularly the projecting ends 17 thereof, and the opposing end walls 11a of the core structure 11.

In further accord with my invention the interior of the core structure 11 can be cooled by utilizing the insulating elements 19 to promote flow of air from one end wall 11a to the opposing end wall 11a of the core structure through passageways 31 extending axially of the core structure, as shown in FIG. 7. As described above, the core structure 11 comprises a stack of laminations 12. Each lamination is formed with a central opening 12a to provide a core structure having an elongated opening through which the shaft 10 extends and upon which the core structure 11 is mounted. As seen in FIG. 6, the opening 12a in each lamination 12 is generally of circular form and further includes spaced open recesses 12b. When the core structure 12 is mounted on the shaft 12 the open ends of the recesses 12b are closed by the shaft to provide several elongated passageways 31 extending lengthwise through the core structure.

As best seen in FIG. 7, the ends of the passageways 31 of the core structure 11 formed by the recesses 12b communicate with the passageways in the insulating elements 19 at regions between the inlets 24 and the outlets 30 and preferably at the junctures of the passageways 28 and 29. In this way the flow of air induced in the passageways 28 and 29 of the insulating elements 19 also induces flow of air in the longitudinally extending passageways 31 of the core structure 11 formed by the recesses 12b of the laminations 12.

When it is not feasible to employ insulating elements 19 at both ends of the core structure 11 and only a single insulating element 19 is employed at one end of the core structure, such single insulating element 19 can be employed to promote cooling of the winding 16 and rotor 11 at one end of the dynamo-electric machine and also induce flow of air through the passageways 31 to the opposite end of the machine.

Claims

I claim:

1. In a dynamo-electric machine, a rotatable member comprising a shaft and core structure mounted thereon having opposing end walls transverse to the axis of rotation of said member, an insulating element positioned at least at one end wall of said core structure and rotatable therewith, said insulating element being formed to provide at least one passageway for air having an air inlet and an air outlet, the air inlet being nearer to the axis of rotation of said rotatable member than the air outlet to induce flow of air through said passageway responsive to the pressure differential of air at the inlet and air at the outlet produced during rotation of said rotatable member, the air flowing through said passageway functioning to promote cooling of the dynamo-electric machine, and said insulating element comprising a hollow hub disposed about said shaft and spaced therefrom to provide a first part of said passageway and a plate extending radially from said hub at said one end wall to provide a second part of said passageway.

2. A dynamo-electric machine as set forth in claim 1 in which said hub is provided with spaced axially extending ridges which extend radially inward from the inner surface thereof, the inner extremities of said ridges being in physical contact with said shaft.

3. A dynamo-electric machine as set forth in claim 1 in which said plate and said one end wall of said core structure cooperate to provide the second part of said passageway having its inner end communicating with the first part of said passageway and its outer end open and serving as the outlet.

4. In a dynamo-electric machine, a rotatable member comprising a shaft and core structure mounted thereon having opposing end walls transverse to the axis of rotation of said member, an insulating element positioned at least at one end wall of said core structure and rotatable therewith, said insulating element being formed to provide at least one passageway for air having an air inlet and an air outlet, the air inlet being nearer to the axis of rotation of said rotatable member than the air outlet to induce flow of air through said passageway responsive to the pressure differential of air at the inlet and air at the outlet produced during rotation of said rotatable member, the air flowing through said passageway functioning to promote cooling of the dynamo-electric machine, and said core structure having an axially extending passageway from said one end wall to the opposing end wall thereof, said last-mentioned passageway at said one end wall of said core structure being in communication with the one passageway provided by said insulating element at a region thereof between the inlet and the outlet.

5. A dynamo-electric machine as set forth in claim 4 in which said core structure is formed with at least one axially extending recess having an open end closed by said shaft to provide said axially extending passageway.