Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-05-26
2001-09-18
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S263000, C310S216006
Reexamination Certificate
active
06291918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an alternator for a vehicle such as a passenger automotive vehicle or a truck.
2. Description of the Related Art
To reduce the aerodynamic resistance in a traveling condition, a vehicle body is often formed into a slanted nose shape. Securing a sufficient residential space for a passenger compartment is earnestly demanded. To satisfy these requirements, engine rooms of automotive vehicles have recently been becoming so narrow and crowded that only a limited space is available for installing an alternator. In addition, the temperature of a region around the alternator is often high. Meanwhile, to improve fuel economy, the rotational engine speed tends to be reduced during an idling condition. The rotational speed of the alternator decreases in accordance with the reduction of the rotational engine speed. On the other hand, there is a need for supplying increasing electric loads such as safety control devices, etc. Thus, a high power generating ability of the alternator is strongly required. In other words, a compact high-power alternator for a vehicle is required. Especially, it is desirable that the power generating performance of an alternator is good even when the alternator is operated at a low rotational speed.
Furthermore, it is highly desirable that noises leaking from vehicles should be reduced. Providing a quiet passenger compartment leads to increased product appeal. To this end, the engine noises have recently been lowered. On the other hand, alternators for vehicles which operate at high rotational speeds tend to generate fan noises which may annoy passengers and, wind blocking sounds, and magnetic sounds.
In a general alternator for a vehicle, the greatest heating source is the stator. To attain a high power output and a high efficiency of an alternator, it is conceivable to reduce the resistance of a winding on the stator and thereby to reduce heat loss. Specifically, an electric conductor having a great cross-sectional area is used for the winding. In addition, it is conceivable to increase the ratio of a conductor-occupied area in each slot in the stator to an unoccupied area. This ratio is hereinafter referred to as the space factor.
In a prior-art alternator for a vehicle, a stator has inner circumferential surfaces opposing a rotor and is formed with teeth. Tips of the teeth have magnetic-flux collecting projections extending in circumferential directions. Therefore, open ends of slots in an iron core of the stator are smaller in width than inner portions of the slots. The thickness of an electric conductor for a winding is limited by the width of the open end of each slot. To increase the power output of the prior-art alternator during operation at a low rotational speed, a great length of the magnetic-flux collecting projections is necessary. As the length of the magnetic-flux collecting projections is increased, the open ends of slots are narrower so that a thinner electric conductor is required for the winding. The thinner electric conductor causes an increased resistance of the winding.
Japanese published unexamined patent application 63-194543 discloses that an electric conductor for a winding has portions to be placed in slots, and these portions are previously made into a shape having an approximately rectangular cross-section as shown in FIG.
10
. The portions of the electric conductor are placed into the slots as shown in FIG.
11
(A). Then, edges of a stator around the slots are plastically deformed into magnetic-flux collecting projections as shown in FIG.
11
(B).
In the prior-art structure of Japanese application 63-194543, the plastic deformation needed to make the magnetic-flux collecting projections results in deteriorated magnetic characteristics. As a result, the magnetic-flux collecting effect is reduced. Thus, it is difficult to attain a desired alternator power output. Especially, it is difficult to provide an increased alternator power output during operation at a low rotational speed.
In the prior-art structure of Japanese application 63-194543, the plastic deformation causes a strain in the stator, decreasing the circularity of the inner circumferential surfaces of the stator and hence forming an uneven air gap between the stator and a rotor.
The uneven air gap increases magnetic noise during operation of the prior-art structure.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems, an object of this invention is to provide a compact high-power alternator for a vehicle.
It is another object of this invention to provide a low-noise alternator for a vehicle which outputs an increased power during operation at a low rotational speed.
The present invention is directed to an alternator for a vehicle which comprises a rotor; a stator located outward of the rotor and opposing the rotor; and a frame supporting said rotor and said stator; wherein said stator comprises an iron core and a plurality of electric conductors, said iron core having a plurality of slots, said electric conductors being placed in said slots, said slots having openings, said openings having a width smaller than a width between inner walls defining said slots, the width of said openings of said slots being smaller than a minimal width of said electric conductors.
Thereby, the resistance of the electric conductors is reduced, and the heat loss is reduced during power generating operation. Thus, it is possible to attain a high alternator power output. Since the projecting portions of the stator teeth edges which serve for collecting the magnetic flux are relatively long if the winding diameter remains the same, the inner circumferential surfaces of the stator iron core can be closer to smooth cylindrical surfaces. Thus, it is possible to reduce the wind noise caused by the ruggedness of the inner surfaces of the stator iron core and the radially outward winds caused by the LUNDEL-type pole core during the rotation of the rotor.
In one aspect of the present invention, the slots have two end surfaces in an axial direction of said stator iron core of the stator which are formed with end surface openings as inlets for said electric conductors. Thus, the width of the openings of the slot inner circumferential side can be set without being limited by the width of the electric conductors.
In another aspect of the present invention, openings in inner sides of said slots are narrower than a width of electric conductor accommodating portions of said slots, and are narrower than the minimal width of said electric conductors before said electric conductors are placed into said slots. Thus, it is unnecessary to deform the iron core teeth edges between the slots after the electric conductors are placed into the slots.
Thereby, the projecting portions of the teeth edges of the stator iron core which serve for collecting the magnetic flux can be made into a desired shape without being shaped by plastic deformation. Thus, the material for the projecting portions for collecting the magnetic flux is prevented from being deteriorated in magnetic characteristic, and it is possible to attain an adequate effect of collecting the magnetic flux. Therefore, the power output at a low speed is improved. Since a shape distortion of the teeth edges by plastic deformation is absent, the true circularity of the inner circumferential surfaces of the stator iron core is well maintained. Thus, it is possible to make uniform the air gap between the rotor and the magnetic pole. Thereby, it is possible to suppress the magnetic noise due to an unevenness of the air gap during the generation of electric power.
In another aspect of the present invention, the electric conductors may use electric conductors which have a circular cross-section with a diameter greater than the width of said openings of the slots.
In another aspect of the present invention of claim
5
, a cooling fan is disposed at least at one axial end of said rotor opposing said stator. Therefore, winds can be driven from the cooling fan toward the coil end
Kusase Shin
Shiga Tsutomu
Umeda Atsushi
Denso Corporation
Jones Judson H.
Pillsbury & Winthrop LLP
Ramirez Nestor
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