Brushless dynamo electric machine with access to rectifier assembly

To replace a diode assembly in a brushless dynamo electric machine without removal of the rotor or separation of the housing along a split line, a sealed cap is located at a position near the end of the hollow rotor. The parts for maintaining the diode housing in operation position can all be slidably removed for permitting each removal and replacement of the diode housing.

DESCRIPTION 
1. Technical Field 
This invention relates to brushless dynamo electric machines commonly used 
as generators which have a common rotor shaft for an exciter unit and a 
main generator unit where the rotors are electrically interconnected by a 
rectifier assembly. More particularly, this invention relates to a novel 
structure allowing easy access to the rectifier assembly for its removal 
or exchange without the need for splitting the housing or removing the 
rotor. 
2. Background Art 
Brushless generators are conventionally formed of a permanent magnet 
generator, an exciter, and a main generator. Typically, relatively low 
levels of power are generated by the permanent magnet generator which is 
made up of a permanent magnet field carried by a generator rotor and which 
induces electrical energy in a stationary generator output winding. The 
power from this winding is rectified and subjected to known control 
parameters before being fed to a stationary field winding of the exciter. 
The exciter includes an output winding carried by the rotor and as the 
same rotates within the magnetic field generated by the exciter field 
winding, electrical energy is induced in the exciter output winding. This 
energy will be an alternating current, not untypically, will be three 
phase. 
The resulting alternating current is rectified by means of a rectifier 
carried within the rotor and rotating therewith as shown for example, in 
U.S. Pat. Nos. 4,621,210 granted Nov. 4, 1986 and 4,329,603 granted May 
11, 1982. The rectified direct current is supplied to the main field 
winding of the main generator. The main field winding, being carried by 
the rotor and when energized with direct current and when rotated, 
provides a rotating magnetic field which in turn induces an alternating 
current in a stationary main armature output winding. Power thus generated 
may be taken from the stationary main armature output winding to a point 
of use by a system that is operative without need for the presence of 
brushes, slip rings or commutators. In aircraft power generating 
applications, the generators may be coupled mechanically to the aircraft 
engine. In the case of jet engines, the coupling is frequently in the 
engine gearbox with the generating system being housed in the same cowling 
as the engine itself. 
The rotating rectifier consists of individual diodes and interconnecting 
wires from the exciter rotor armature and to the D.C. main field which is 
mounted on the rotor shaft. During operation, the electrical losses in the 
rectifier diodes are dissipated as heat which must be carried away to 
prevent over temperature and resulting failure of diodes. 
A problem has existed because of a servicing requirement which calls for 
withdrawal or exchange of rectifier units from time to time. Such 
rectifier withdrawal in the past has required the housing parts to be 
split along a split line and the rotor removed to allow the rectifier 
assembly to be withdrawn from the interior of the hollow rotor shaft for 
exchange. Such a procedure is time consuming. Since the rectifier assembly 
is one of the more vulnerable components in the integrated drive generator 
which may be of the general type shown in U.S. Pat. No. 4,609,842 granted 
Sept. 2, 1986, the procedure is one which is required from time to time. 
DISCLOSURE OF INVENTION 
A major object of the present invention is to provide a novel structure 
allowing the rectifier assembly to be removed from the interior of the 
rotor shaft without splitting the dynamo housing and without removal of 
the rotor shaft. 
A further object is to provide a novel sealed cover which is removable from 
the dynamo housing at a position near the rectifier assembly so that 
access is available through an open end of the hollow rotor shaft. 
Another object of the invention is to provide an arrangement for the wiring 
of the exciter unit armature to extend through an open end of the hollow 
rotor shaft to a terminal connector on the rectifier assembly which is 
easily accessible through the removable cap. When removal of the rectifier 
assembly is desired, the exciter wire terminal can first be removed 
totally from a position inside the hollow rotor without cutting or 
destroying the wire. 
A yet further object of the invention is to provide an assembly of parts 
all of which are insertable through the exposed end of the hollow rotor 
which includes diode housing for the rectifier assembly together with 
means engaged with the open end of the rotor shaft for securing the diode 
housing against axial movement along the rotor shaft. As a further 
feature, ducting is provided for supplying coolant to the diodes in the 
diode housing through end walls that allow a flow of coolant in the 
direction of the rotor axis. 
These and other objects of the invention will become more fully apparent 
from the claims, and from the description as it proceeds in connection 
with the drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
An integrated drive generator as illustrated in the drawings is connected 
to be driven by a prime mover through a transmission (not shown) that 
maintains the rotor speed constant during normal operation of an aircraft 
over a wide range of engine speeds. The integrated drive generator housing 
traditionally is formed of pieces including those shown at 8 and 9 that 
are held together by bolts 10 along a break line at 11. 
The main generator armature 12 which supplies current to the utilization 
circuit is conventionally mounted to the housing part 8 as by threaded 
fasteners 14. The rotationally mounted main generator field winding 16 is 
supplied with current from an exciter 20 having a stationary field winding 
22 and a rotating armature 24. The output of the exciter armature 24 is 
connected to diodes 26 which are part of the rectifier assembly and 
thereby rectify the alternating current output from the armature 24 and 
supply a D.C. current to the main generator field winding 16 which rotates 
concomitantly with the armature 24 of exciter 20. 
Rectifier diodes 26 are mounted to rotate with the hollow rotor shaft 27 
which supports the rotors of both the main generator and the exciter so 
that no brush, commutator or slip ring is required. 
In accordance with one aspect of the present invention, the shaft 27 is 
hollow and the rectifier bridge circuit formed of diodes 26, which 
customarily is connected to be a three phase full wave rectifier or a 
three phase half wave rectifier as shown in U.S. Pat. No. 4,329,603, may 
be installed as a sub-assembly on a framework within a cylindrically 
shaped diode housing 30. The diode housing 30 is positioned between the 
exciter unit 20 and the field winding 16 of the main unit. 
In FIG. 2, the rectifier positive terminal pin 32 and negative at terminal 
pin 34 are shown as being received in sockets that are electrically 
connected to the main generator field winding 16 that rotates with shaft 
27. The pins 32 and 34 are of a type which allow for easy separation from 
their respective sockets when the diode housing 30 is removed for 
servicing and for easy insertion when a diode housing 30 is replaced. The 
sockets are anchored to the rotor shaft 27 by socket support housing 35 to 
furnish firm positioning for the diode housing 30. 
Hollow rotor shaft 27 is shown in FIG. 2 to be supported by rollers 36 
forming a bearing located radially outwardly from the diode housing 30 and 
positioned in housing part 9. The opposite end of shaft 28 is supported by 
a bearing 38 in housing part 8 that is shown in FIG. 1. The end of the 
hollow rotor shaft 27 shown at the left side of FIGS. 1, 2 and 4 is, in 
accord with another feature of the invention, not supported outboard of 
the exciter 20 and thus the exciter is cantilever mounted outboard of the 
bearing rollers 36. 
With reference to FIG. 4 the exciter rotor 28 is shown mounted at the end 
of the rotor shaft 27. Stationary coolant oil spray orifices 29 are 
mounted to provide more efficient cooling of the overhung exciter 20. The 
cooling efficiency is increased by positioning one or more stationary 
orifices 29 in a wall of a stationary housing part to direct cooling oil 
onto the inside surface at an outboard position of one end winding of the 
exciter. This produces a turbulent flow at the winding surface which will 
give better cooling than where the coolant flow is laminar. 
With reference to FIGS. 2 and 3, diode housing 30 has three internally 
threaded terminals 40, one for each phase of the exciter armature 24, that 
receive respective externally threaded fasteners 42 which secure the ring 
tongue terminals 43 which are crimped to the exciter output leads 50 (see 
FIGS. 2 and 4) as part of the electrical connection between the respective 
exciter armature terminals and the input terminals to the diodes 26 in the 
diode housing 30. Each end wall of the diode housing 30 that is transverse 
to the rotational axis has a central aperture through which coolant is 
circulated. Manifold 44, through which fasteners 42 extend, has a central 
aperture 46 in transversely extending end walls through which a transfer 
tube 48 extends. The transfer tube 48 connects with a transfer support 
liner 49 for conveying coolant to the diodes in diode housing 30. 
One important feature of the construction just described is that the wires 
50 from the exciter armature 24 and connected to threaded terminals 40 are 
introduced into the interior of the rotor shaft 27 through slots 28 at an 
end 29 of the rotor shaft 27 rather than passing through holes in the 
walls of the rotor shaft 47. Where leads pass through holes in the walls 
as might be contemplated, impregnated lacing tape was required to secure 
the leads to the shaft adjacent to their entry into the shaft 27 from the 
exciter armature 24. Such a construction makes withdrawal of the rectifier 
assembly in diode housing 30 from the hollow shaft 27 difficult because of 
the need to cut securing ties and to pull the leads out of the rotor shaft 
27 to leave the interior unrestricted. The hollow interior of shaft 27 
must be free of wires so that diode housing 30 can be slid out from the 
open end of the rotor shaft 27. 
By this feature of the present invention, the three leads 50 from the 
exciter armature 24 are passed directly into respective slots 28 at the 
open end 29 of the rotor shaft (see FIG. 3) and to the threaded terminals 
40 (see FIG. 2). Disconnection and removal from the interior of the rotor 
shaft is easy without the need to cut or otherwise destroy any wire or 
wire securement structure. Reconnection of the wires 50 to terminal posts 
after replacement of the diode housing 30 does not require tape or 
impregnate. The wires 50 are secured by the close fit tolerance of the 
wire insulation and the three slots in the manifold 44 that are adjacent 
to the holes in the manifold into which the terminals 40 extend and 
receive the three threaded fasteners 42. 
To gain access to the interior of the hollow rotor shaft where the diode 
housing is located, a cap 52 is provided. The end of the dynamo housing 9 
near cap 52 is illustrated in FIG. 3 to have six holes 54 through which 
threaded fasteners (not shown) are received in the respective threaded 
holes 56 of the dynamo housing part 9. 
The end face of cap 52 may be provided with a radially extending protrusion 
58 which has a central duct 60 for coolant oil to be supplied to diode 
housing 30 through the open end of hollow rotor shaft 27 by means of the 
transfer tube 48. Coolant is supplied from duct 62 of housing part 9 to 
duct 60 as by means of a nipple 64. The stationary orifices 29 shown in 
FIG. 4 may be part of the interior surface of cap 52 and directly face the 
exciter windings to be cooled without an intervening rotor shaft bearing 
because of the placement of bearing 36 between the rotors of the exciter 
dynamo and the main dynamo. 
One end of coolant transfer tube 40 passes thru the central aperture 46 of 
manifold 4 and into transfer tube support liner 49 and the other end of 
the transfer tube 48 fits into an aperture at the center of cap 52 to be 
in sealed fluid communication with duct 60. The distal end of diode 
housing 30 near terminal pins 32, 34 opens into the central hollow portion 
of the rotor shaft 28 upon which the main generator field winding 16 is 
positioned. 
The manifold 44 is held in position on the diode housing 30 by tabbed 
washer 66 and externally threaded nut 68. Nut 68 is locked in position by 
means of a bendable tab on tabbed washer 66. The open end portion 29 of 
the hollow rotor shaft 27 is threaded to receive nut 68. Upon tightening 
nut 68, the parts are placed under compression against the sockets for 
pins 32 and 34 of the diode housing 30. 
Removal of the diode housing 30 requires first the removal of cap 52 from 
housing section 9. Thereafter, the tabs on washer 66 are unbend and nut 68 
is removed along with washer 66 to expose the wires 50 from the exciter 
armature 24. Removal of the three wires 50 from the three threaded 
terminals 40 allows easy removal of the manifold 44. Thereafter, the diode 
housing 30 is grasped and pins 32 and 34 extracted from their respective 
sockets. 
It is thus apparent that the diode housing 30 can be removed without 
requiring separation of the dynamo housing portions 8 and 9 along split 
line 11. Also, it is apparent from the foregoing description that the 
rotor shaft and its bearings remain in place during this servicing 
procedure. Installation of diode housing 30 and replacement of cap 52 
follows the reverse procedure. Cooling of the exciter is made more 
efficient by the positioning of the bearings 36 inboard of the exciter. 
While only a single embodiment has been described, it is apparent that many 
changes and modifications may be made without departing from the spirit of 
the invention. It is therefore intended that all changes and equivalents 
falling within the scope of the appended claims be covered thereby.