Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a device for inhibiting
rotation between two relatively rotatable members, such as
a multiple friction disc brake which is liquid cooled.
Multiple friction disc brakes of the liquid cooled
type disclosed herein are suitable for use in fixed and mobile
installations. The brake herein is configured for use in a
land vehicle and is adapted for use as a retarder in such a
vehicle.
Some of the more salient problems with brakes of ~ ;
this type include uniform cooling of the discs by the cooling
liquid and parasitic energy consumption by the retarder when
it is unapplied. Several United States patents teach that
more uniform cooling of the discs may be obtained by flowing
the cooling liquid radially inward over the discs. However,
each of these patents disclose features which cause relatively
high parasitic energy consumption either directly or
indirectly by the brake.
An object of the invention is to provide a multiple
friction disc brake of the liquid cooled type which is low
in direct and indirect parasitic energy consumption.
The present invention resides in a device for
inhibiting rotation between two relatively rotatable mebers,
the device including a housing, shaft means rotatably
disposed within the housing, first and second sets of inter-
lea~ed friction discs having oppositely facing friction sides.
The discs are respectively secured against rotation relative
to the housing and shaft means, and means is provided for
selectively squeezing the disc sets together to inhibit
rotation of the shaft means relative to the housing. Flow
passage means is defined by the discs for directing cooling
liquid between the radially inner and outer extents of the
discs. In the present invention, there is provided a
plurality of internal splines defined on the inside diameter
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of the second set of discs, and a plurality of external
splines is defined by the shaft means and slideably receives
the internal splines for rotatably securing the second set
of discs to the shaft means. The external splines have a
depth in excess of the radially inwardly projecting extent
of the internal splines for forming axially extending flow
passages directing substantially all of the cooling liquid
between an end of the shaft means and the discs sets.
In a specific embodiment of the invention, the
housing is secured against rotation, and the housing defines
passage means circumferentially disposed about the outer
periphery of the disc sets for porting the cooling liquid
radially inward through the flow passage defined by disc
sets and through the axially extending flow passages defined
by the external splines.
BRIEF DESCRIPTION OF THE DRAWING
The preferred embodiment of the invention is shown
in the accompanying drawing in which:
` FIGURE 1 is an elevational view of a retarder
sectioned along line 1-1 of FIGURE 2; and
FIGURE 2 is a sectional view of the retarder taken
along line 2-2 of FIGURE 1.
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DETAILED DESCRIPTI O~ OF THE DR~WI~G
Referring now to the drawing, therein is shown a retarder
10 adapted to be interposed between an unshown transmission output
and a drive or propeller shaft for a drive axle of a land vehicle.
Retarder 10 broadly includes a drive shaft assembly 12 having a
through shaft 13 and a beveled input gear portion 13a, a non-
rotating or fixed housing assembly 14, a pair of tapered roller
bearings 16 and 18 carried by the housing assembly and rotatably
supporting and retaining the shaft assembly against axial movement
relative to the housing assembly, a set of rotor friction discs 20
axially moveable relative to the housing and shaft assemblies and
fixed to rotate with the shaft assembly, a set of stator friction
discs 22 axially moveable relative to the housing and shaft
assemblies and fixed against rotation relative to the housing
assembly, an annular piston 24 having a generally Z shaped cross
section and operative to squeeze the discs into frictional
interengagement, an inlet port 26 for introducing a pressurized
cooling liquid from an unshown supply pump to an annular area 28
radially outward of the disc sets and defined by the non-rotating
housing assembly, and an outlet port 30 for the discharge of the
cooling liquid from an area radially inward of the disc sets.
Looking now at the retarder in greater detail, shaft
assembly 12 includes through shaft 13, bevel gear portion 13a,
; a set of splines 13b, a threaded end portion 13c, a generally .
cylindrically shaped member 32 having internal splines 32a engaging
splines 13b, an output member 34 having internal splines 34a
engaging splines 13b, and a nut 36 for preventing axial movement
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of members 32 and 34 in combination with a shoulder portion 13d.
Cylindrical member 32 includes a plurality of deep, external
splines 32b for slidably retaining the rotor discs against
rotation relative to shaft assembly 12 and for providing axially
extending flow passages 32c for cooling liquid flowing to outlet
port 30 after the liquid has flowed radially inward over the disc
sets.
Housing assembly 14 includes a partially shown outer
housing member 38, an inner housing support member 40, and an end
cover member 42. Members 40 and 42 are secured to the outer
housing member by a plurality of bolts 44. The broken away or
unshown portion of outer housing member 38 is configured for
attachment to a transmission housing at an angle for facilitating
a meshing engagement of beveled input gear portion 13a of through
shaft 13 with a beveled output gear of the transmission. In a
preferred orientation of the outer housing member, the inlet and
outlet ports 26 and 30 are positioned above the maximum height of
the friction discs to insure total flooding of the disc sets by
cooling liguid. Of course, this flooding effect can be obtained
by placing only the outlet port high or by placing a portion of
an unshown outlet line high.
Inner housing member 40 includes a plurality of axially
extending notches or internal splines 40a for slidably retaining
the stator discs against rotation, a plurality of circularly
arrayed passages 40b (FIGURE 2) directing cooling liquid from
annular area 28 to the outer perip~ery of the disc sets, an end
portion 40c providing support for an annular reaction ring 46
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secured by a plurality of countersunk screws 48, an outlet passage
consisting of annular grooves 40d and 40e and a plurality of
passages 40f for communicating passages 32c with outlet port 30,
and a plurality of circularly arrayed blind bores 40g retaining
springs 50 which bias piston 24 to the deactuated position away
from the friction disc sets. Annular groove 40d is sealed from
annular area 28 and the housing area containing bevel gear
portion 13a via ring seals 52 and 54. Annular groove 40e is
sealed fxom the housing area containing bearing 16 via a ring
seal 56. A bleed passage 40h allows a small amount of cooling
liquid to flow into the area containing bearing 16 for lubricating
the bearing. This lubricating liquid is drained from the housing
area containing the bevel gear via an unshown return passage.
To insure an even distribution of cooling liquid to the outer
periphery of the disc sets, passages 40b flare out to the right
(see hidden line 40i in FIGURE 1) so that the outlet of liquid
therefrom extends the axial extent of the disc sets.
The inside diame~er 46a of annular reaction ring 46 extends
radially inward beyond the inside diameter Of disc sets 20 and 22
and into a necked down portion 32d of deep splines 32b adjacent
to annular outlet groove 40e. This arrangement forces the flow
of cooling liquid in flow passageS32c radially inward beyond the
disC sets and tends to even out the radial inflow distribution of
cooling liquid from the disc sets along the axial extent of
passageS32c.
End cover member 42 in combination with housing member 40
and piston 24 defines an annular chamber 58 for applying pressur-
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ized fluid via a fluid inlet port 42a to actuate or move piston
24 to the left and 'rictionally squeeze the disc sets together
against t~e reaction provided by reaction ring 46. Annular
chamber 58 is sealed by ring seals 60 and 62. A bleed passage
42b allows a small amount of cooling liquid into the area con-
taining bearing 18 for lubricating the bearing. This area is
drained by an unshown drain passage and is sealed at its rightward
end by a seal 64 carried by an annular ring 66. Ring 66 is secured
to end cover member 42 via a plurality of bolts 68.
An important feature of the instant retarder relates to the
fact that annular area 28 and passages 40b are formed by non-
rotating members of the housing to negate centrifugal pumping or
rotation of the cooling liquid rather than being formed in a
rotating housing,which rotating housing would tend to pump or
impart a radially outward pressure to the cooling liquid, thereby
requiring a pressure increase of the cooling liquid with a
resultant energy consumption increase by the supply pump pressur-
izing the cooling liquid. This energy consumption is in effect
a parasitic energy consumption caused by the design of the retard-
er.
Referring now mainly to FIGURE 2 which shows half of arotor disc and half of a stator disc, rotor discs 20 are each
annular in shape and are each retained for rotation with shaft
assembly 12 via internal splines 20a which slidably receive
splines 32b of member 32. Further, each rotor disc is formed with
smooth oppositely facing friction sides 20b to minimize centrifugal
pumping and rotation of the cooling liquid by the discs rather than
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with cooling liquid flow grooves which would tend to pump and
rotate the cooling liquid. Such pumping of the cooling liquid
directly increases the parasitic energy consumption of the retard-
er and in the instant retarder such pumping and rotation opposes
radial infl~w of the cooling liquid, whereby the pressure of
the cooling liquid must be increased with a resultant indirect
energy consumption increase by the supply pump pressurizing
the cooling liquid.
Stator friction discs 22 are each annular in shape, are
each retained against rotation relative to housing assembly 14
via external splines 22a which slidably receive splines 40a of
housing member 40, and are each provided with a plurality of
grooves 22b on their oppositely facing friction sides 22c. Grooves
22b in combination with smooth sides 20b of the rotor discs
provide stationary passages which allow the flow of cooling liquid
radially inward over the discs from non-rotating area 28 and
passages 40b into deep splines 32c.
The preferred embodiment of the invention has been
disclosed for illustration purposes. Many variations and
modifications of the preferred embodiment are believed to be
within the spirit of the invention. The following claims are
intended to cover the inventive portions of the preferred embodi-
ment and variations and modifications believed to be within the
spirit of the invention.
