Patent Application
20080030100
Now, a vehicle alternator of an embodiment according to the present invention will be described below in detail with reference to the accompanying drawings. However, the present invention is construed not to be limited to such an embodiment described below and technical concepts of the present invention may be implemented in combination with other known technologies or the other technology having functions equivalent to such known technologies.
A vehicle alternator of an embodiment according to the present invention will be described below in detail with reference to the accompanying drawings.
As shown in
The rotor 2 takes the form of a structure that includes a pair of front and rear pole cores 22 carried on a shaft 23 in a face-to-face relationship so as to sandwich a field winding 22 composed of a copper wire would in a cylindrical and concentric shape therebetween. Each pole core 22 has six claw portions that are formed at circumferentially and equidistanly spaced positions. In addition, the front pole core 22 has a front end face 22F carrying thereon a front cooling fan 25 fixedly secured to the front pole core 22 by welding or the like for drawing cooling wind streams FW through a plurality of air-intake windows 7a formed on the drive frame 7 to blow out the cooling wind streams FW in axial and radial directions. Likewise, the rear pole core 22 has a rear end face 22R carrying thereon a rear cooling fan 26 fixedly secured to the rear pole core 22 by welding or the like for drawing cooling wind streams RW through a plurality of ventilation windows (not shown) formed on the rear frame 8 to blow out the cooling wind streams RW in axial and radial directions.
In addition, the shaft 23 has a rear end portion 23a carrying thereon two collector rings (slip rings) 27 at axially spaced positions. The slip rings 27 are electrically connected to both ends of the field coil 21 to supply electric power from the brush device 4 to the field winding 21. The stator 3 includes a stator core 32, sandwiched between the drive frame 7 and the rear frame 8 for support in a fixed place, and a three-phase stator winding 33 or the like.
The brush device 4 plays a role as a device to allow excitation current to flow from the commutator device 5 to the field winding 21 of the rotor 2. The brush device 4 includes two brushes 41 held in pressured contact with the two slip rings 27 provided on the rear end portion 23a of the shaft 23 of the rotor 2. When assembling the vehicle alternator 1 of the present embodiment onto a vehicle, the brush device 4 is placed on a mounting position set such that the brushes 41 are located beneath the slip rings 27 so as radially extend downward and pressed in radially upward directions.
The commutator device 5 serves to rectify a three-phase alternating voltage, that is, an output voltage of the three-phase stator winding 33, to obtain a D.C. output power. The rear cover 10 serves to cover electric component parts such as the brush device 4, the commutator device 5 and the IC regulator 6 or the like mounted on an outside face of the rear frame 8 to protect these component parts. The rear cover 10 is fixedly secured to the outside face of the rear frame 8 by tightening bolts, extending therefrom, with metal nuts with the commutator device 5 being sandwiched.
The drive frame 7 and the rear frame 8 accommodate therein the rotor 2 and the stator 3 to allow the rotor 2 to rotate about the rotary shaft 23, and the stator 3 is fixedly secured so as to have a given clearance with respect to an outer periphery of the pole core 22 of the rotor 2.
Further, the drive frame 7 and the rear frame 8 have, in addition to front and rear end walls provided with the air-intake windows, front and rear outer circumferential portions formed with discharge windows in areas radially aligned with front and rear axial extensions of the stator windings 33 axially protruding from axial end faces of the stator core 32. Thus, the front and rear cooling winds are caused to be brown out of the alternator 1 through the discharge windows.
Next, reference is made to
As shown in
The brush holder 43 includes a substantially box-like case, made of synthetic resin, which has a base end portion, whose front and rear sidewalls have opening portions 43a formed in areas facing the slip rings 27. The brush holder 43 has a bottom portion 43b placed in opposition to the opening portions 43a, which have discharge ports 45 extending in slant directions to discharge foreign particles P to the outside the brush holder 43.
The springs 44 are disposed in spaces between the bottom portion 43b of the brush holder 43 and end portions 41a of the brushes 41 at base ends thereof under preliminarily compressed conditions to generate given loads. Further, an appropriate amount of clearance CL is provided between each of sidewalls 43c of the brush holder 43 and an outer periphery of each brush 41 to enable each brush 41 to smoothly move. The brush holder 43 has a wire holder portion 43d formed in an area near the bottom portion 43b of the brush holder 43 and has a metal fitting 46 to which the power supply wire 42 is electrically and mechanically connected by a suitable method such as soldering.
Further, the brush device 4 has a slip ring cover 47 serving as a cover member for surrounding the slip rings 27. The slip ring cover 47 is used with the brush holder 43 in combination therewith to have a function defining a ventilation window passage 47a between an inner wall of a lower end portion of the slip ring cover 47 and the adjacent sidewall 43c of the brush holder 43. In addition, liquid droplets such as water droplets or the like are kept away from the slip rings 27 and the brushes 41 and liquid droplets are prevented from intruding the opening portion 43a of the brush holder 43. In addition, the ventilation window passage 47a, defined between the slip rings 27 and the collector0ring cover 47, is opened toward the brush holder 43 as viewed from side areas of the slip rings 27.
The brush device 4, formed in such a structure, is suitably placed such that the brushes 41 are placed beneath the slip rings 27 with the most typical exemplified structure being shown in
Next, the operation of the brush device 4 of the alternator 1 is described below.
In operation, upon receipt of a drive power from a prime mover, the rotor 2 is caused to rotate with the accompanied rotations of the slip rings 27. Meanwhile, since the brush device 4 is fixedly supported on the rear frame 8 to be non-rotatable, no rotations of the brushes 41 occur. The brushes 41 is supplied with electric power from an external source via the electric power supply wire 42 and pressed toward the slip rings 27 by means of the springs 44. Under such a state, the brushes 41 are held in sliding contact with the slip rings 27 to apply electric power to the field coil 21 through the slip rings 27.
In general, the brushes 41 are made of material such as graphite and the slip rings 27 are made of material such as copper. With sliding operations of the both of these members, the brushes 41 gradually wear, generating wear particles P. The wear particles P pass through a clearance between the brushes 41 and the sidewalls 43c of the brush holder 43 and are directed downward due to actions of gravity. The wear particles P pass through the brush holder 43 to the bottom portion 43b thereof, upon which the wear particles P are expelled from the discharge ports 45.
Thus, no wear particles P accumulate on the bottom portion 43b. In addition, the discharge ports 45 are formed with slants 45a, respectively, in the form of substantially maze patterns. This prevents foreign matters such as water droplets or other liquid droplets from entering an inside of the brush holder 43 from the outside.
Here, first and second Comparison Examples of the related art, wherein brush devices with related art structures are placed beneath the slip rings, are described below for comparison to the brush device of the present embodiment.
Of the brush devise of the related art structures, the first Comparison Example is of the type in which brushes are placed on slip rings so as to extend upright in nature.
With the brush devise 104 used in a status with brushes 141 placed beneath the slip rings 27, liquid such as water droplets L easily intrude an inside of a brush holder 147 from ventilation passages 147a of a slip ring cover 147. This causes corrosions to occur on internal component parts such as the slip rings 27.
With the progress of corrosions occurring on the slip rings 27, degradation occurs in a proper sliding contact between the brushes 141 and the slip rings 27, inducing remarkable wears of the brushes 141. When this takes place, the brushes 141 and the slip rings 27 produce wear particles P. The wear particles P drop through a holder opening 143a of the brush holder 143 into spaces between bottom walls of the brushes 141 and a bottom wall 143b of the brush holder 143 and accumulate therein. Thus, an issue arises with the occurrence of disturbances in smooth movements of the brushes 141.
Of the brush devise of the related art structures, the second Comparison Example is of the type in which brushes are placed on slip rings so as to extend downward in nature.
With the brush devise 204 of the second Comparison Example, even if brushes 241 are placed beneath the slip rings 27, no liquid such as water droplets intrude into an inside of a brush holder 243 because a slip ring cover 247 has a ventilation opening directed downward in communication with the outside.
During the flow of ventilation air streams through the ventilation passage 147a, wear particles P partly pass through the ventilation passage 247a to the outside. However, a major part of the wear particles P drop through a holder opening 243a of the brush holder 243 into spaces between bottom walls of the brushes 241 and a bottom wall 243b of the brush holder 243 and accumulate therein. This results in the occurrence of disturbances in smooth movements of the brushes 141.
As will be apparent from the foregoing description, with the brush device of the present embodiment, the brush holder 43 includes the discharge ports 45 for expelling the foreign materials such as wear particles P. Thus, even with the brush device 4 located in a state with the brushes 41 placed beneath the slip rings 27, that is, even under a circumstance where a holder opening 43a faces upward to allow the brushes 41 to be forced upward, the foreign matters such as the wear particles P, resulting from the wears of the brushes 41 due to the sliding contact between the brushes 41 and the slip rings 27, are expelled through the discharge ports 45 in a highly reliable manner.
This prevents the accumulation of the brush wear particles in the brush holder 43, thereby precluding the disturbances from occurring in movements of the brushes 41. Specifically, the discharge ports 45 are formed on the bottom portion 43b in areas in opposition to the holder opening 43a of the brush holder 43, thereby reliably preventing the foreign matters such as the brush wear particles from accumulating in the bottom portion 43b.
Further, the discharge ports 45 are formed with the slants 45a, respectively, in the form of the maze patterns, thereby preventing liquid such as the water droplets or the like from entering the inside of the brush holder 43 from the outside while making it possible to expel the foreign matters such as the brush wear particles P of the outside in a highly reliable manner.
Furthermore, the brush device 4 of the present embodiment additionally includes the slip ring cover 47 for covering the slip rings 27. The slip ring cover 47 has the ventilation window passage 47a, formed between the slip rings 27 and the slip ring cover 47, which is opened in face with the brush holder 43 as viewed from the slip rings 27. Thus, with the brush device 24 installed to allow the brushes 41 in the areas beneath the slip rings 27, the ventilation window passage 47a is directed toward the ground. This prevents the foreign matters such as the water droplets or the like from entering the inside of the brush device 4.
Thus, the brush device 4 of the present embodiment suppresses an increase in temperature due to frictional heats developed with the brushes 41 and the slip rings 27 in sliding contact with each other while ensuring the slip ring cover 47 to have increased waterproof. In addition the provision of the discharge ports 45 formed in the brush holder 43 at the bottom portion 43b thereof makes it possible to reliably expel the foreign matters such as the brush wear particles.
While the specific embodiment of the present invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure.
While the present invention has been exemplarily described in detail with reference to the specific embodiment with the brush holder 43 having the discharge ports 45 formed on the bottom portion 43b, the discharge ports 45 may be formed in other areas of the brush holder 43 in opposition to the holder opening 43a thereof or in areas close proximity to such other areas because such areas enable the brush wear particles or the like to be reliably expelled. For instance, the discharge ports 45 may be formed on the sidewalls 43c of the brush holder 43.
Thus, the particular arrangement disclosed is meant to be illustrative only and not limited to the scope of the present invention, which is to be given the full breadth of the following claims and all equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-211107 | Aug 2006 | JP | national |
