Rotating electrical machine

A rotating electrical machine includes a flange provided at one end of a hollow frame in an axial direction; a rotor including a shaft, the shaft being rotatably supported by the flange; and a stator fixed to an inner section of the frame, the stator surrounding the rotor. The rotor includes a first rotor core and a second rotor core arranged in the axial direction and having recesses formed in the axial direction, and a rotor-core space defined by the recesses that are formed in the first rotor core and the second rotor core and that face each other.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-059770, filed Mar. 16, 2010. The contents of the application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to rotating electrical machines.

2. Discussion of the Background

Japanese Unexamined Patent Application Publication No. 2002-281721 discloses a rotating electrical machine suitable for use as a large-capacity rotating electrical machine. The rotating electrical machine has a combination of the number of poles and the number of coils suitable for using the rotating electrical machine as a permanent magnet synchronous motor. Accordingly, an induced voltage waveform is close to a sine wave, and the amplitude of a cogging torque is reduced so that the required skew angle can be reduced. Therefore, even when the capacity of the rotating electrical machine is increased, the influence of unbalanced attractive force is small.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a rotating electrical machine includes a flange provided at one end of a hollow frame in an axial direction; a rotor including a shaft, the shaft being rotatably supported by the flange; and a stator fixed to an inner section of the frame, the stator surrounding the rotor. The rotor includes a first rotor core and a second rotor core arranged in the axial direction and having recesses formed in the axial direction, and a rotor-core space defined by the recesses that are formed in the first rotor core and the second rotor core and that face each other.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The external structure of a rotating electrical machine10according to an embodiment of the present invention will be described with reference toFIGS. 1 and 3.FIG. 1is a side view of the rotating electrical machine10,FIG. 2is a front view of the rotating electrical machine10, andFIG. 3is a top view of the rotating electrical machine10.

Referring toFIGS. 1 to 3, the rotating electrical machine10is a large motor having an extremely high output. The rotating electrical machine10is fixed with bolts (not shown) to a bracket B with a plate-shaped flange unit12provided therebetween. The rotating electrical machine10is fixed such that a shaft11extends horizontally. Four rings13for suspending the rotating electrical machine10with a crane are provided at the top of the rotating electrical machine10. A surface of the rotating electrical machine10is covered by a cover14, and four cooling fans15are provided at each side of the rotating electrical machine10. An encoder unit16that controls the position and speed of the motor is provided at the back of the rotating electrical machine10. A connector unit17through which power is supplied is provided above the encoder unit16.

The fans15are provided at the opposite sides of the rotating electrical machine10so as to face each other in a plan view of the rotating electrical machine10as viewed in an axial direction of the shaft11.

Internal Structure of Rotating Electrical Machine10

The internal structure of the rotating electrical machine10will now be described with reference toFIG. 4.FIG. 4is a side sectional view of the rotating electrical machine10. The shaft11is provided so as to extend through a rotating shaft of the rotating electrical machine10in the axial direction. The rotating electrical machine10includes the flange unit12at one end of a substantially rectangular, hollow frame20in the axial direction. The rotating electrical machine10also includes a lid unit18at the other end of the frame20in the axial direction. The shaft11is rotatably supported by bearings21and22provided on the flange unit12and the lid unit18, respectively.

Structure of Rotor Unit30

A rotor unit30is fixed to the shaft11. The rotor unit30rotates together with the shaft11. The rotor unit30includes a first rotor core31A and a second rotor core31B. The first rotor core31A and the second rotor core31B are arranged next to each other in the axial direction. Magnets32are provided on the outer peripheral surfaces of the first rotor core31A and the second rotor core31B. The magnets32are permanent magnets. The shaft11has a shape including step portions having different outer diameters. A rotor-core attachment portion11ais provided at a central section of the shaft11in the axial direction, where the outer diameter of the shaft11is the largest. The rotor cores31A and31B are fixed with bolts33to rotor-core attachment surfaces11band11c, respectively, which are side surfaces of the rotor-core attachment portion11ain the axial direction. The method for fixing the rotor cores31A and31B is not particularly limited, and the rotor cores31A and31B may instead be fixed using keys, spannrings, or the like.

The rotor cores31A and31B include rotor-core outer peripheral portions34to which the magnets32are attached, rotor-core inner peripheral portions35at which the rotor cores31A and31B are attached to the rotor-core attachment portion11a, and rotor-core central portions36that connect the rotor-core outer peripheral portions34to the rotor-core inner peripheral portions35. The rotor-core outer peripheral portions34are shaped so as to protrude from both sides of the rotor-core central portions36in the axial direction. Thus, the first rotor core31A and the second rotor core31B have recesses formed in the axial direction.

The rotor unit30is provided with a rotor-core space37that is defined mainly by the rotor-core outer peripheral portions34, the rotor-core central portions36, and the rotor-core attachment portion11a. In other words, the rotor unit30is provided with the rotor-core space37defined by the recesses that are formed in the first rotor core31A and the second rotor core31B and that face each other. Owing to the rotor-core space37, the weight of the rotor unit30is reduced. Therefore, the inertia of the rotor unit30is reduced and the efficiency of the motor is increased. With the above-described structure, a rotating electrical machine having a light structure suitable for increasing the size thereof in accordance with the increasing capacity can be provided.

Structure of Stator Unit40

A stator unit40is provided so as to surround the rotor unit30with an air gap therebetween at the outer periphery of the rotor unit30. The stator unit40includes a first stator core41A and a second stator core41B. The first stator core41A and the second stator core41B are arranged next to each other in the axial direction. The first stator core41A and the second stator core41B are fixed to an inner section of the frame20.

A reinforcing plate42made of metal, such as steel or stainless steel, is provided between the first stator core41A and the second stator core41B so as to extend substantially parallel to the flange unit12. With this structure, a rotating electrical machine having a high-rigidity structure suitable for increasing the size thereof in accordance with the increasing capacity can be provided.

The first stator core41A, the second stator core41B, and the reinforcing plate42are positioned with respect to each other by a pin43inserted therethrough, and are fixed to the frame20. Thus, the rigidity of the stator unit40is increased.

The pin43is a single component, and extends through the first stator core41A, the reinforcing plate42, and the second stator core41B from one end of the frame20to the other end of the frame20in the axial direction. Thus, the rigidity of the stator unit40is further increased.

Description of Detailed Shape of Reinforcing Plate

The detailed shape of the reinforcing plate42will now be described with reference toFIGS. 5A and 5B.FIGS. 5A and 5Bare sectional views of the stator unit40, whereFIG. 5Ais a sectional view ofFIG. 4taken along line VA-VA andFIG. 5Bis a sectional view ofFIG. 4taken along line VB-VB. As illustrated inFIG. 5A, the first stator core41A includes a plurality of teeth51, and coils (not shown) are wound around the teeth51. In addition, as illustrated inFIG. 5B, the reinforcing plate42includes a plurality of tongue portions52that have slightly larger width and height than those of the teeth51around which the coils are wound. Accordingly, deformation of the teeth51can be prevented and the coils can be easily inserted. With the above-described structure, a rotating electrical machine that can be easily manufactured can be provided.

Description of Reinforcing Structure Including Reinforcing Bars

A reinforcing structure of the rotating electrical machine10including reinforcing bars will now be described with reference toFIG. 6.FIG. 6is a side view of the rotating electrical machine10in the state in which the cover14is removed. The above-described reinforcing plate42is provided at a central section of the rotating electrical machine10in the axial direction. A reinforcing bar61is attached to the frame20at each of the opposite sides of the frame20in a plan view of the frame20as viewed in the axial direction of the shaft11. The reinforcing bar61extends in a direction perpendicular to the reinforcing plate42. In addition, reinforcing bars62aand62bare diagonally attached to the frame20in an inclined manner so as to intersect each other.

With this structure, a rotating electrical machine having a high-rigidity structure suitable for increasing the size thereof in accordance with the increasing capacity can be provided. More specifically, since the reinforcing structure including the above-described reinforcing bars is used, the frame20is strongly reinforced. As a result, even when the rotating electrical machine10is a motor having extremely large size and capacity, the rotating electrical machine10can be supported in a cantilever manner by fixing the flange unit12to the bracket B in a state such that the shaft11is substantially horizontal.

Cooling Operation Using Fans

Next, a cooling operation using the fans15will be described with reference toFIG. 7.FIG. 7is a schematic diagram illustrating the cooling operation performed by the fans15. As illustrated inFIG. 7, rotation directions of the fans15are set such that air blows into the rotating electrical machine10. The fans15are disposed symmetrically to each other with respect to the axial line of the rotor unit30. The air from the fans15at an upper section (at one side of the axial line) hits the stator unit40and absorbs heat from the stator unit40. Then, the air is reflected by the stator unit40and is discharged from the top of the rotating electrical machine10. The air from the fans15at a lower section (at the other side of the axial line) hits the stator unit40and absorbs heat from the stator unit40. Then, the air is reflected by the stator unit40and is discharged from the bottom of the rotating electrical machine10. The rotating electrical machine10is fixed to the bracket B in a cantilever manner with the flange unit12provided therebetween, and no obstacle is placed above or below the rotating electrical machine10. Therefore, the cooling air that hits the stator unit40smoothly flows out of the rotating electrical machine10. Therefore, the rotating electrical machine10with an extremely high output that generates high-temperature heat can be effectively cooled. With this structure, a rotating electrical machine having a structure for effectively dissipating the generated heat that increases with the increasing capacity can be provided.

The fans15are fixed to the frame20or the reinforcing bars62aand62b. In the case where the fans15are provided on the reinforcing bars62aand62b, the air from the fans15hits the reinforcing bars62aand62band is diffused, so that the cooling efficiency can be increased.

As described above, the rotating electrical machine10according to the present embodiment includes the reinforcing plate42and the reinforcing bars62aand62bin the frame unit, so that the rotating electrical machine10can be supported in a cantilever manner using the flange unit. In addition, the cooling effect can be further increased by placing the fans15at appropriate positions. In the case where the fans15are provided on the side surfaces of the frame20, the fans15function as reinforcing members for reinforcing the side surfaces of the frame20. Therefore, the rigidity of the frame20can be further increased.

An embodiment of the present invention has been described above. However, it is apparent to those skilled in the art that various alterations can be made to the embodiment, and such alterations are also within the technical scope of the present invention.

Description of Rotor Skew

For example, in the above-described embodiment, the rotor unit30is not skewed. However, the rotor unit30may be skewed. Skewing of the rotor unit30will now be described with reference toFIGS. 8A and 8B.FIGS. 8A and 8Bare schematic diagrams illustrating skewing of the rotor unit30.FIG. 8Aillustrates a rotor-core attachment surface72, andFIG. 8Billustrates a rotor-core inner peripheral portion35. The rotor-core attachment surface72is either of the rotor-core attachment surfaces11band11c, and has internal thread portions71formed therein. The internal thread portions71are arranged along a circumference at a constant pitch (at24positions inFIG. 8A). Bolt insertion holes (first holes73a), the number of which corresponds to the number of bolts necessary for providing torque resistance, are formed in the rotor-core inner peripheral portion35. The first holes73aare arranged along a circumference at a constant pitch (at 6 positions inFIG. 8B). Additional bolt insertion holes (second holes73b, third holes73c, and fourth holes73d), the number of which corresponds to the number of bolts necessary for providing torque resistance, are also formed in the rotor-core inner peripheral portion35. The second holes73b, the third holes73c, and the fourth holes73dare arranged at a constant pitch at positions shifted from the first holes73aby predetermined angles (α, β, and γ). With this structure, the rotor unit30can be skewed with relatively large freedom. In the case where each of the first rotor core31A and the second rotor core31B has the above-described structure, the rotor unit30can be skewed at an angle other than the predetermined angles (α, β, γ), for example, at (α−β) or (α+β). When the rotor unit30is skewed, cogging thrust can be reduced and smooth control can be achieved.

In the above-described embodiment, the fans15are attached to the cover14or the frame20. However, the fans15may instead be attached to the inclined reinforcing bars62aand62b. In such a case, the fans15function as structural components and the rigidity of the frame20can be increased. In addition, when the inclined reinforcing bars62aand62bare positioned at the centers of the fans15, the cooling air is evenly divided so as to flow along both sides of each of the reinforcing bars62aand62b. Therefore, the reinforcing efficiency can be further increased.

The rotating electrical machine10is not limited to a motor, and may instead be a generator.

In addition to the above-described examples, methods of the above-described embodiment and modifications may be used in combination as appropriate.