Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~39245
BRAKE SERVO A~SEMBLY FOR AN
AUTOMATIC POWER TRANSMISSION
BRIEF DESCRIPTION OF THE INVENTION
My invention comprises improvements in a trans-
mission system of the type illustrated in U.S. patent No.
3,404,575. That patent shows a gear system that comprises
a compound planetary gear unit with two torque input
elements and two torque reaction elements. Clutch means
are provided for connecting selectively the turbine of a
torque converter to either one or the other or both of the
torque input elements. The impeller of the torque conver-
ter i5 connected to a vehicle engine crankshaft.
An output gear element of the gear system is con-
nected to a driven shaft, which in turn is connected to
the vehicle traction wheels through a driveshaft and
differential mechanism.
A reaction element of the gear system is con-
nected to a brake drum which is surrounded by a brake band.
A piston for a fluid pressure operated servo is connected
at the operating end of the brake band by means of a strut,
and the reaction end of the brake band is connected by
means of a strut to a reaction point on the stationary
transmission housing. The latter strut is formed with a
precalibrated length so that adjustment of the brake servo
would not be required after final assembly.
The operating end of the brake band is connected
mechanically to one end of the associated strut prior to
the final assembly operation and a corresponding connection
is established between one end of the reaction strut and
the reaction end of the brake band. These connections
facilitate final assembly of the brake band and the trans-
mission mechanism and their lengths, or the length of onestrut, can be calibrated so that it is unnecessary to pro-
vide for brake band adjustment for any particular trans-
mission installation. The connection between each of the
band ends and their respective strut is achieved by means
of a roll pin that extends through registering openings in
the strut and in the end of the brake band. According to
., '`' ~
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another embodiment the connection is established by means
of a tab formed on the brake band ends and an opening in
the adjacent end of the strut that registers with the tab.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS
Figure 1 shows an automatic power transmission
mechanism having a brake band servo capable of using the
improvements of my invention.
Figure 2 is a cross-sectional assembly view of
a brake band for use in the construction of Figure 1.
Figure 2A is a detail view of a brake band end
as seen from the plane of section line 2A-2A of Figure 2.
Figure 3 is a view similar to Figure 2 showing
- an alternate embodiment for the brake band strut retaining
. .
means.
Figure 3A is a detail view of a brake band end
as seen from the plane of section line 3A-3A of Figure 3.
PAR~ICULAR DESCRIPTION OF THE INVENTION
In Figure 1 numeral 10 designates an internal
combustion engine for an automotive vehicle driveline.
Numeral 12 designates a driven shaft which is adapted to
be connected to vehicle traction wheels 14 through a drive
shaft and a differential-and-axle assembly. A hydrokinetic
torque converter 16 is situated between the engine 10 and
a multiple ratio gear assembly indicated generally by
reference character 18.
The converter 16 includes a bladed impeller 20,
a bladed turbine 22 and a bladed stator 24. The turbine,
the impeller and the stator are arranged in known fashion
in a torus circuit. The impeller is connected drivably ~o
engine crankshaft 26,and turbine 22 is connected to a tur-
bine shaft 28. The stator 24 is mounted on a stationary
stator sleeve shaft 30. An overrunning brake 32 anchors
the stator 24 against rotation in a direction opposite to
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the direction of rotation of the impeller, but which per-
mits freewheeling motion of the stator in the direction
of rotation of the impeller.
The gear assembly 18 comprises a pair of sun
gears of differential diameter, the larger sun gear being
shown at 34 and the smaller sun gear being shown at 36.
A first set of long planet pinions 38 mesh with sun gear
34 and also with ring gear 40. A set of short planet
pinions 42 mesh with small sun gear 36 and with the long
planet pinions 38. The planet pinions 42 and the planet
pinions 38 are rotatably supported on a common carrier
44. Ring gear 40 is connected drivably to power output
shaft 12. Small sun gear 36 is connected to intermediate
shaft 46 and large sun gear 34 is connected to sleeve
shaft 48. The carrier 44 is adapted to be braked against
the transmission housing by means of an overrunning brake
50 located between the carrier and a transmission center
support 52 which is connected to the housing. Carrier 44
defines a friction brake drum 54 about which is positioned
brake band 56.
A forward drive friction clutch 58 is adapted to
connect the turbine shaft 28 to the intermediate shaft 46.
It includes friction discs carried by clutch element 60 and
by intermediate shaft 46 which are adapted to be engaged
drivably by fluid pressure operated clutch servo 62.
Clutch element 60 forms also a part of high-and-reverse
clutch 64 which establishes a driving connection between
the larger sun gear 34 and the clutch element 60. Clutch
64 includes a clutch servo 66 having an annular piston
that engages clutch discs carried by brake drum 68 and by
companion clutch element 60. A brake band 70 surrounds
the drum 68 and is engaged and released by a ~luid pres-
sure operated brake servo 72.
Brake band 56 for the carrier 44 is applied and
released by fluid pressure operated brake servo 74. Brake
servo 72, unlike brake servo 74, is a double acting servo.
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It is applied when fluid pressure is admitted to the pres-
sure chamber 76 on the left hand side of the piston 78.
It is released when both the pressure chamber 76 and the
opposed pressure chamber 80 are pressurized. Brake band
56 is applied when pressure is admitted to the pressure
chamber 82 of the servo 74. Brake band 56 is released by
spring 84 acting on the piston 86.
Overdrive operation in the low speed ratio is
obtained by engaging clutch 58. Turbine torque then is
delivered to sun gear 36 through shaft 46. Carrier 44
acts as a reaction member since it is braked by the over-
running brake 50 against the housing. With the ring gear
40 acting as a torque output element, the output shaft 12
is driven at its lowest speed ratio. An upshift to the
intermediate speed ratio is achieved by engaging the brake
band 70 thus anchoring the sun gear 34. The overrunning
bra!ce 50 freewheels in this condition. Clutch 58 is
engaged during operation in each of the overdriving
ratios.
Direct drive operation is achieved by disengag~
ing the br~ke 70 and applying both clutches 58 and 64
simultaneously. This locks together the elements of the
gearing for rotation in unison to establish a 1:1 speed
ratio.
Reverse drive operation is achieved by dis-
engaging the clutch 58 and engaging the clutch 64. The
brake band 56 is applied so that the carrier 44 acts as
a reaction member as the ring gear 40 is driven in a
reverse direction relative to the direction of motion of
the sun gear 34.
I have shown in Figure 1 in schematic form the
elements of the automatic control valve system. This
includes a fluid pressure governor 88 connected to the
output shaft 12. A transmission throttle valve 90, which
is actuated by an engine intake manifold pressure sensitive
transducer 92, supplies a torque sensitive pressure signal
to the control valve system 94. The governor 88 supplies
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a speed signal to the same control valve system. Pressure
for the control valve system is supplied by an engine
driven pump 97. The valve system responds to the signals
from the throttle valve to the governor to distribute
control pressure from the pump to the brake servos and the
clutch servos to establish the shift sequence, previously
described. The transducer 92 responds to a vacuum signal
from the engine intake manifold 96. A driver controlled
accelerator pedal 98 adjusts the position of the throttle
valve blade in the throat of the carburetor associated with
the manifold 96.
In Figure 2 I have shown in detail the servo and
the brake band assembly for the carrier 44 illustrated
schematically in Figure 1. Numeral 100 designates the
transmission housing. Brake drum 54 is surrounded by
brake band 56. The internal surface of the brake band 56
is formed with a semi-circular bend 104 and the operating
end of the brake band 56 is formed similarly with a semi-
circular bend 106. The anchor end of the brake band 56 is
nested in a brake band adaptor 108, which defines a contin-
- uation of the internal friction surface of the brzke band._ A reaction strut is disposed between the anchor end of the
brake band 56 and a reaction pin 114 which is received in
opening 116 in the housing 100. Reaction pin 114 is pro-
vided with a groove 118 which receives a recess 120 in the
adjacent end of the strut 112. This is best seen in
Figure 2A.
The end of the strut adjacent the brake band is
provided with an opening 122 which is aligned with an
opening extending in a generally radial direction with res-
pect to the brake band as shown at 124. Opening 124
extends through the adaptor 108 and through the bend 104 of
the brake band 56. A roll pin 126 extends through the
aligned openings 122 and 124 thereby retaining the strut
112 in its assembled condition.
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The operating end of the band is connected to
servo piston rod 128 by means of brake band strut 130.
The end of the strut 130 adjacent the brake band is
received in the bend 106 and is formed with an openinig
132 which is aligned with an opening 134 formed in the
bend 106 and the adaptor 110. A roll pin 136 is received
through the aligned openings 134 and 132 thereby retain-
ing the strut 130 in its assembled condition.
The piston rod 128 is positioned slidably in
opening 138 in the housing 100. It is attached to servo
piston 86, which is slidably positioned in brake operating
cylinder 142. The outboard end of the piston rod 128 is
provided with a notch 144 which receives the adjacent end
of the strut 130.
The length of the strut 112 can be chosen to
suit any particular application. This makes it unneces-
sary to provide a mechanical adjustment in the servo to
compensate for slack in the brake band. It is possible
to use a common servo and piston rod for any of a variety
of transmission installations merely by choosing the
correct blank for strut 112 as well as for the strut 130.
In this way the dimension "X" shown in Figure 2, which is
a critical dimension, can be maintained. The roll pins
that are used with the brake band ends and with the asso-
ciated struts make it possible to assemble the brake bandassembly during high volume manufacturing operations with
no difficulty.
In the embodiment of Figures 3 and 3A I have
provided an alternate means for attaching the ends of the
brake band struts to the ends of the brake band. In the
Figure 3 and Figure 3A embodiment the operating end of
the brake band is provided with a tab 136'which extends
radially inwardly toward the center of the band. The tab
144 is received within the opening 132' in the strut 130'.
This tab connection is used in lieu of the roll pin 136
shown in Figure 2. In a similar fashion the anchor end of
the brake band is provided with a tab 126' which extends
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radially inwardly and which is received in opening 122'
in the brake band strut 112'. Tab 126'serves the purpose
of a roll pin 126. In other respects the construction of
Figure 3 is the same as the construction of Figure 2, and
the elements of the Figure 3 construction have been iden-
tified by similar reference characters although prime
notations are added.
