Manufacture of electric motor component

The modular conical stator pole provides an improved conical stator assembly on electrical machines. The improved conical stator pole assembly comprises a plurality of stator poles, each pole comprising an assembly having a coil secured on a soft magnetic composites (SMC) stator pole tooth by inserting a winding support through the open core of the coil and attaching a back iron and a stator face to either end of the winding support. Each stator pole having a parallelogram shaped cross section for forming a conical shaped rotor space when the stator poles are assembled having the back irons bearing against each other to space the coils apart and form a conical shaped outside profile of the stator pole assembly. The conical stator having a small end and a big end. The tooth comprising a winding support integrally molded with either the back iron or the face.

BACKGROUND OF THE INVENTION

The present invention relates to electrical machines and more particularly a design and method of manufacture for a conical stator assembly.

Electric motors and generators have a stationary element, termed a stator and movable or rotating elements termed the rotor. The interaction between the stator and the rotor is caused by the interaction on a magnetic field generated by either the stator or the rotor. Such magnetic field is usually generated or induced by electric currents in a winding placed on either the stator or the rotor or both. The forces imparted on the rotor are a function of the interaction of the stator and the rotor magnetic fields and the moment arm of the rotor calculated by the radial displacement of the magnetic field of the rotor with respect to the axis of the rotor. Such stator winding usually comprises a plurality of coils wound around a winding support. The winding support is usually comprised of a soft magnetic material which traditionally is made of laminations of selected steel materials. The laminations are insulated from each other in order to reduce eddy currents.

It's become known to replace laminated steel materials of the stator or rotor cores with ferro magnetic powder particles. These ferro magnetic particles are compacted in a powder metallurgy operation to form the winding support. The ferro magnetic power particles themselves are electrically insulated from each other so the resulting compacted product exhibits a low eddy current loss in a manner similar to the use of stacks of laminated steel materials. Such use of compacted metal particles comprised of ferro magnetic powder particles for cores electrical machines is disclosed in U.S. Pat. Nos. 6,956,307 B2, 6,300,702 B1 and 6,441,240 B1.

Prior art motor designs use a significant amount of air space and can be large and heavy when assembled making shipping the assembled electric motor costly. When installing or maintaining, prior art motors require special handling due to the size and weight. Furthermore, prior art motors are not designed to be modular and capable of being broken down to separately shipped components. Design changes often require motor manufacturers to retool a facility to manufacture a different design. Retooling is generally very expensive and requires down time from production while the tooling is modified or replaced.

Conventional prior art motors use large amounts of copper in the windings to form each pole of the stator. The magnetic field generated is related to the amount and placement of the copper as well as the current in the windings. Power density may be increased by increasing the effective use of the copper and maximizing the inner surface area of the stator. Increasing the power density of the motor may also be accomplished by forming a modular shaped segment from the ferro magnetic particles to conform the electric motor to the space available.

Prior art symmetrically shaped cylindrical motors do not maximize the available mounting space available in installation locations. It is desirable that the stator fill as much of the open space as is practical to improve performance by optimizing the interaction between the electromagnetic field of the stator and the rotor. This produces a more efficient motor generator. It is further desirable to maximize the radial space available in order to advantageously use the increased radial dimension of a conical design to increase the moment arm to increase available torque at the drive shaft of the motor. Such terminology is deemed as the power density of the motor.

SUMMARY OF THE INVENTION

The modular conical stator pole provides an improved conical stator assembly on electrical machines and, more specifically an improved conical stator assembly for use in electrical motors and generators. The improved conical stator pole assembly comprises a plurality of stator poles. The conical stator having a small end and a big end. Each stator component dimensioned to a tapered assembly of predetermined length. Adjacent stator components are assembled to form a tapered stator pole, a plurality of tapered stator poles are assembled circumferentially about an axis to form a conical shaped stator assembly.

Each stator pole component comprises a winding and a tooth. The tooth comprises a back iron, body and a face. A winding is created either by winding directly onto the tooth body, or by prewinding on a bobbin having an open core and inserting the tooth into the bobbin, or by winding around a mandrel to form an open core and inserting the wound coil over the tooth in the open core. The conical shape may be formed by molding the face of each stator pole component in a trapezoidal shape having a tapering cross section to form the overall interior and exterior conical shape of the conical stator. Alternatively, the back iron may be molded with a trapezoidal shape thus forming the conical shape. The back iron and face may have a parallelogram shaped cross section to dispose the face at an angle to the axis forming the conical shaped rotor space. In either configuration the rotor space is formed in a conical shape with the face of each pole component having a concave radial cross-sectional shape about the axis of the stator while the axial dimension is disposed in a non-parallel relation to the axis creating the conical shaped rotor space.

The tooth may be formed of ferrous magnetic metal powder particles. These particles are processed to generally be mutually insulated. The ferrous magnetic metal powder particles are pressure formed into the predetermined shape for the tooth tip and the back iron in a powder metal operation by die compacting and heat treating. The tooth body may be formed integral to the back iron for inserting the body into the open core of the coil and securing the coil by attaching the face to the body, or forming the body integral to the face with the back iron attached to the body for securing the coil in place. The tooth body may be disposed perpendicular to the stator axis of perpendicular to the stator face.

The stator face may be formed as a fully formed face of the stator pole having one or more, spaced tooth bodies extending therefrom. For example, a stator face having three tooth bodies attached, extending radially away from the stator face and spaced from each other may be formed. Three coils, each coil having an open core may be assembled onto the stator face having one coil disposed over each tooth body. A back iron and face are secured to each tooth body having the coil intermediate the back iron and the face to hold the coil on the tooth body. The back iron may be a three segment shape or may comprise three discrete back irons as discussed herein for securing the three coils on the spaced tooth bodies extending from the stator face. This integral stator face provides additional support to hold the coils in spaced relation and minimizes magnetic field disruptions caused by discrete edges between separate stator faces in a stacked component design. The back iron and the conical face on the tooth tip may both be formed with a single tooth body holding a single winding on the stator pole.

The conical stator assembly is formed of a plurality of stator pole means each comprising a generating means electrically connected to an electrical power supply, a support means formed of ferrous magnetic metal powder particles, the support means defining a field supporting and directing means holding the generating means in spaced relation to the axis of the rotor. The field pole means assembled with other field pole means to form a multi-pole stator. The trapezoidal shapes and complex angles of the support means disposing the generating means in spaced relation to the axis of the stator forming a conical rotor space and/or a conical outside stator shape.

It's a feature of the present invention that such an improved conical stator assembly comprises a shape for optimizing the power density of the motor and maximizing available torque by increased moment arm at the big end of the conical design and increasing the active length of the stator. The conical design provides a larger moment arm at the big end for transferring the reactionary force of the interaction of the stator magnetic field and the rotor magnets to provide increased torque compared to a cylindrical design.

Torque is increased by the increased moment arm of the larger radial displacement of the rotor coils with respect to the axis of the rotor. This increased displacement takes advantage of the conical shape of the stator. Furthermore, the conical shape provides increased active length on the stator pole for increasing the flux conducted to the rotor. the modular shape allows the motor to securely fit into the space available based on the particular application.

Further, the rotor may be axially moved with respect to the stator. The rotor is moved in a direction of from the small end of the conical shape towards the large end of the conical shape to uniformly change the air gap between the rotor and stator to decrease back emf and weaken the rotor flux allowing an increased speed range for a permanent magnet motor design. This increase in air gap reduces the loses of the motor and the corresponding flux density exponentially.

Each stator component may be shipped as individual components for assembly in the field by a machine assembly team. Most motor failures are in the bearings or windings. The modular design allows the coil to be removed from the stator component, a new coil slipped onto the tooth body and the motor reassembled. Furthermore, in the event of a component failure, a modular stator component part of the electrical machine may be shipped for replacement without replacing the entire motor. In this way each pole of the conical shaped stator is maintainable at the motor site.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1, the conical shaped stator10comprises a plurality of stator poles12assembled circumferentially about a stator axis14. Each pole12comprises a modular molded tooth16. The tooth16comprises a stator face18and a tooth body120(FIG. 3b). The stator face18has a generally rectangular shape tilted at an axial angle to define the conical shaped interior surface20defining a rotor space22. A rotor24is rotatably mounted in the rotor space. The rotor24is axially aligned along the axis14of the stator and held in place by bearings or the like (not shown) to rotate in the rotor space. The rotor comprises a core26having a plurality of magnets28disposed along the outer perimeter30. The magnets28are isolated from each other by dividers32. Each magnet28defines a pole on the rotor24. the outer perimeter30is precisely machined to maintain a predetermined air gap34between the rotor24and the stator10.

The stator10surrounds the rotor space with the plurality of spaced stator face18portions of each pole12. The stator faces18are formed having an arcuate inner surface36, a generally flat outer surface38and a pair of substantially similar axial ends40.

The arcuate inner surface36is axially concave forming a circular cross sectioned interior space20. The tooth16may be formed of soft magnetic composites (SMC) comprising ferrous magnetic metal powder particles. These particles are processed to generally be mutually insulated. The ferrous magnetic metal powder particles are pressure formed into the predetermined shape for the tooth16in a powder metal operation by die compacting and heat-treating.

Continuing to refer toFIG. 1, the tooth16further comprises a back iron56on the outside of the tooth16. The back iron56is attached to the tooth16to secure a coil54disposed on the tooth16between the tooth face18and the back iron56. The back iron56has edges68for bearing against adjacent poles12to hold the coil54of each pole in spaced relation to each other coil54on the adjacent poles12.

The conical design shown inFIG. 1applies torque on the rotor24as a function of the magnetic force interacting between the stator pole12and the magnet28on the rotor24and the moment arm measured from the air gap34to the axis14. The moment arm is larger adjacent the large end104and smaller adjacent the small end102of the stator assembly10. The stator face18is disposed at a non-parallel circumferential orientation to the stator axis14to form the conical interior surface20of the conical stator10for rotatably accepting a conical shaped rotor therein.

Referring toFIG. 2, the poles12are removably assembled about the axis14to form a multi-pole12stator10. Each pole is formed of a ferrous magnetic metal powder particles are pressure formed into the predetermined shape. The poles are individual field generating systems using the coil54as a generating means and the tooth tip14as a magnetic field carrying means to support and direct the magnetic field generated by the coil to interact with the magnets28of the rotor24. The axial end42adjacent the small end102has a first circumferential length and the axial end44adjacent the large end104has a second circumferential length, the first length being smaller than the second length due to the conical arcuate shape of the tooth16. The angled orientation of the axial dimension of the stator face18to the axis of the stator may increase the active length of the entire stator pole12by as much as 10%.

It should be understood the rotor magnets28may be permanent magnets28or electro magnets positioned and oriented to form a magnetic pole on the rotor24. The coil54is connected to an electrical device60which may be a power supply66to create a current in the coil54to generate a magnetic field for interaction with the magnets28of the rotor24. Coil54is electrically connected by conductor64having connecting means62for electrical connection to power supply66.

The electric motor stator10shown has six of twelve poles12illustrated having adjacent back irons56of adjacent poles12butted against each other and adjacent stator faces18of adjacent stator poles12spaced from each other. The stator assembly portion10is illustrated as one stator component12long. However as discussed above, a modular conical stator pole12may have a plurality of stator components stacked axially to form a stator pole12having a plurality of coils54held in spaced relation and axially aligned.

The motor10is easily constructed and maintained by the use of individual components12. The stator components12are circumferentially assembled to define the rotor space12. This modular approach allows an individual component12to be replaced and maintained in place without replacing the electric motor.

Referring toFIGS. 3aand3b, a stator pole12assembled together and in exploded view. The conical stator assembly10has a conical interior surface20and a rotor24shown in offset outline. The rotor24is spaced from the10by air gap34. Each stator pole12is equally radially spaced from the axis14to interact with the magnets28on the rotor24. The conical shaped rotor24has a small end122and a large end124.

The coil54comprises a plurality of windings of a conductive material preferably copper or aluminum wire. The wire is insulated along its length to prevent short circuit connections between the windings. The coil54may be toroidal or rectangular in shape having an open core70(FIG. 3) and is held in place by the tooth16. The coil54may be wound directly on the tooth body120or may be formed separately as a bobbin or winding on a mandrel. A magnetic field generated by the coil54is conducted and shaped by the tooth16at the stator face18and directed into the rotor space22.

Continuing to refer toFIGS. 3aand3b, the stator component12may be formed of ferrous magnetic metal powder particles that are processed to be generally mutually insulated from the other particles. The particles are pressure formed into a desired, predetermined shape. The tooth16comprising a face18, back iron56and tooth body120may be molded having the tooth body120integrally molded with the back iron56or the tooth face18. The tooth body120acts as a winding support for the coil54as well as a flux conductor or guide to shape and support a magnetic field generated by current in the wire64energizing the coil54. In the embodiment ofFIGS. 3a,3b,4aand4b, the tooth body120is integrally formed with the back iron56,156on a first end126of the tooth body120and the tooth face attached to a second end128of the tooth body120.

The coil54supported between the first end126and the second end132. The second end128of the tooth body120extends through the open core70and into pocket137and is thereby removably attached to the tooth face18using adhesive or fasteners. The tooth face18has a tooth pocket137formed therein for receiving the second end128.

Referring toFIGS. 4aand4b, tooth pocket137may be a through passage opening into the concave face118of tooth116. The tooth116comprises a back iron156, a tooth body120and a tooth face118having a concave inner surface. The coil154is disposed around the tooth body120and secured between the face118and the back iron156. The second end128may have a concave surface136adapted to align with the tooth face118to form a portion of the concave inner surface20of the rotor space22(FIG. 1) as the second end is disposed in the pocket137

Referring toFIG. 5, a cross section portion of a conical shaped stator assembly10is shown sectioned along a radius of the stator10. The cross section of each stator pole12has a parallelogram shape having the ends perpendicular to the axis14and the sides (face and back iron)18,56oriented at an acute angle to the axis to form the conical shape. The parallelogram shaped tooth16may be formed by molding the face18in a planar configuration, the body radially oriented and the back iron formed to have angled ends that when assembled with the winding support and the face create a parallelogram shape having the sides tapering away from the axis to form the conical shape. Alternatively, the stator assembly may be assembled to conical shape having a radially extending cross section tapering along the axis to form the overall conical shape98of the rotor space22stator. The back iron56may be molded with a trapezoidal shape (FIG. 3a) thus forming the conical shape88. In either configuration the rotor space22is formed in a conical shape98causing the adjoining faces18to form a concave surface20about the axis14of the stator10while the axial dimension is disposed in a non-parallel relation to the axis14creating the conical shaped rotor space22.

Referring toFIG. 6a housing100is illustrated having small end102and a large end104to contain the conical10(FIG. 1). An alignment rib106may be disposed on the interior surface108of the housing100radially aligned an alignment channel74on certain stator poles12(FIG. 1). The alignment rib106engages the alignment channel74(FIG. 2) on the stator pole components12to hold the stator components12radially aligned (FIG. 1).

In use, the stator component10is assembled with the coil54held on the tooth16between the back iron56and the tooth face18. The tooth body120is integrally molded to either the tooth face18or the back iron56. The non-integrally molded part is attached using adhesive, fasteners or other fastening techniques. For example if the tooth body120is integrally molded to the back iron56as shown inFIG. 3, the face18is attached to the second end132of the body120spaced from the back iron56. Each coil54has a connector64extending from the winding to electrically connect the coil54to a current source66for providing a magnetic field at the stator pole10or to a power consuming device if the segment is connected as a generator. The axial edges68of adjacent tooth face18may abut against each other to form a smooth concave interior surface20or may be held in spaced relation as shown inFIG. 1. The axial ends of adjacent back iron56components may abut against each other to form the continuous outer conical shape88(FIG. 1,5) of the back iron structure56or may be held in spaced relation by the alignment rib106(FIG. 6).

The stator10is assembled using the following steps not necessarily in the order listed:

Mold a stator pole comprising a tooth16having a tooth body120, a back iron56and a tooth face18from soft magnetic composites (SMC) comprising ferrous magnetic metal powder particles, the back iron56having a trapezoidal shape comprising complex angles for forming a conical shaped stator10when assembled with other similar teeth16, the trapezoidal shape having an outer surface spaced from an axis14of the stator10at a first radial distance adjacent the small end102of the conical shaped stator10and the outer surface spaced a second radial distance adjacent the larger end104of the conical shaped stator10, the second radial distance larger than the first radial distance;

Mold the tooth body integral with either the back iron or the tooth face;

Wind a coil on a mandrel or a bobbin, the coil wound with a predetermined wire having a thickness, the wire wrapped a predetermined number of windings around the mandrel or bobbin forming a plurality of turns and an open core70in the center;

Place the coil on the tooth16having the tooth body120extending through the open core70;

Secure the coil on the tooth body120between the back iron on a first end of the tooth body and the tooth face18on the second end of the tooth body;

Forming a pocket137on the tooth face18if the tooth body is formed integrally with the back iron, the tooth pocket137for receiving the tooth body120therein, the tooth face adapted to be mounted such that an inner surface20of the face is spaced a third radial distance from the axis14of the stator10adjacent the large end104of the stator and spaced a fourth radial distance from the axis of the stator10adjacent the small end102of the stator, the third distance greater than the fourth distance to form the conical shaped rotor space22, attach the tooth face to the tooth by inserting the tooth body into the pocket137to secure the coil54between the tooth face18and the back iron56, the tooth face18fastened to the tooth body120by adhesives or fasteners;

Form a pocket in the back iron56if the tooth body is formed integrally with the tooth face18, The tooth pocket adapted to receive a first end of the tooth body to adapt the back iron to attach to the tooth body to secure the coil in place, Attach the back iron to the tooth by inserting the first end of the tooth body into the pocket on the back iron56to secure the coil54between the tooth face18and the back iron56, the back iron fastened to the tooth body120by adhesives or fasteners; and

Circumferentially assemble a plurality of stator poles12about an axis14, the stator poles held in place by fasteners, a housing100or other known holding means, the stator poles12forming a conical shaped stator assembly10having a conical shaped rotor space22.

In operation, the rotor24may be axially moved in operation to increase or decrease the air gap34between the rotor24and the stator10. The rotor24movement axially with respect to the stator10uniformly changes the air gap across the entire stator assembly. The rotor24is moved in a direction of from the small end102of the conical shaped stator10towards the large end104of the conical shaped stator10to uniformly increase the air gap34between the rotor24and stator10to decrease back emf and weaken the rotor flux allowing an increased speed range for permanent magnet motors.

The present invention has been shown and described with reference to the foregoing exemplary embodiments. It is to be understood, however, that other forms, details, and embodiments may be made without departing from the spirit and scope of the invention which is defined in the following claims.