Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
~ IMPROVED BLOCKING ~IN FOR A
TRANSMISSIDN SYNCHRO~IZER ASSEMBLY
S ~ACKGROUND OF TH~ INVENTION
l. Field of the Invention-
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The pxesent invention relates in general to motor
vehicle transmissions and i~ particular to an improved
blocking pin ~or a transmission ~ynchronizer assembly.
Synchronizing clutches, such as are used in
transmission gearings for motor vehicles, are typically
~hiftable in oppo~ite direction~ from a neutral position to
either of two different ~peed ratio or drive positions.
Clutches of this type typically include a single, toothed
element and two friction elements, the toothed element
having clutch teeth ~ormed on opposite ends thereof and the
friction elements having a fxiction face formed on
outwardly facing ends thereof. ~he two friction elements
can be connected by a plurality of blocking pins, each
having a blocking shoulder formed thereon to prevent the
toothed element from shifting at undesired times. The
blocking pin~ can each include a notch formed thereon to
position the toothed element accurately in a neutral
position between the two drive positions.
The toothed element and friction face at one end of
the synchronizer assembly coact with a respective
complementary element and face on a member in one gear
drive means whil~ the toothed element and friction face at
the other end of the synchronizer assembly coact with a
respective complem~ntary element and face on a member in
another gear drive means. The synchronizer assembly
elements are shiftable as a unit in one direction or the
other by applying a shifting foree to the toothed element
until the friction face of the friction element at one end .
of the synchronizer a~sembly engages with the complementary
friction face on the gear drive means. The toothed elemen~
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is then, after synchronization of the speeds of the output
shaft and the gear drive means, shiftable axially relative
to the fri~tion ~lement~ a~ the shifting force is continued
.to b~ applied such that the toothed element is brought into
5 engageme~t with the coacting ~gear drive means element.
2. Description of the Prior Art
United States Patent No. 2,384,439 to Carnagua et al.
discloses a positive clutch mechani5m wherein the shift
frDm a lower ratio, such as a second speed, to a higher
i 10 ratio, 8uch as a direct drive, is effected automatically in
~3 response ~o a decelerating tor~ue load transmitted from the
lo~er ratio driving member to the clutch mechanism. The
ds~nshift from the higher ratio to the lower rat~o may be
effected by a torque responsive means under the control of
15 tbe operator in moving the engine throttle control in a
tbrot~le opening direction. The torque responsive
re~hanism energizes both a frictional synchronizing Y
echanism and a positive clutch means. Blocking pins in
~ frictional synchronizing mechanism can include a recess
20 or gx~ove positioned on either side of the neutral position
-~ess for positioning a shift sleeve in a desired gear
io. Similar grooves are illustrated in U~ited States
F~tent No. 3,086,633 to Winter.
~nited States Patent No. 2,425,203 to Peterson et al.
25 ~loses a synchro~izing clutch having a blocking shoulder
c~ blo~king tooth arran~ement whereby blocking takes place
o~y when a shift is bei~g made from a lower speed drive
~o a higher speed drive or, if desired, from a higher
~r ratio into a l~wer gear drive wherein the vehicle is
3~ is~otion and a member in the gear train i~ rotating.
~bcking does .not take plsce when a shift:is.being made
m a lower gear drive wh~n the vehicle is stationary or
member in the lower gear drive is not rotating.
Vnited States Patent No. 2,900tO59-to Zittrell et al. .
35 ~closes an ~mproved synchronization device having a
~tion shift member and a push do~ sleeve which ean be
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locked until synchronism is xeached. Locking members are
guided so as to be radially movabl~ on a riction ring
~reely rotatable within the anner part of the gear ~hift
61eeves. The locking members have sloping rounded surfaces
S at each end, the inwardly directed ends of which fit
opposing surfaces ~ituated on the inner pcrtion of the gear
shift sleeve and ar~ effected in the peripheral direction.
The outwaxdly directed ends of the sloping rounded surfaces
meet opposite surfaces of the push dog sleeve and ~re ' .
10 effected in the axial direction. The opposite surfaces
arranged in the inner part of the gear shift sleeve axe r
formed in marginal recesses of the inner part which allow
space for partial rotation of the friction ring relative to
the inner part so as to permit radial movement of the ~.
15 locking members during rotation of the friction ring. ~.
SUMMARY O~ THE INVENTION
The present invention relates to an improved blocking
pin for a transmission synchronizer assembly. The assembly
includes a toothed element which is rotatable with an
output shaft and adapted to be selectively engaged with a
gear drive means for rotating the output shaft. A
synchronizing friction element rotatable with the toothed
element is adapted to be selectively engaged with a
friction face of the gear drive means. A plurality of
blocking pins are provided to slidably mount the toothed
element coaxially with respect to the fricti4n element.
Each of the ~locking pins includes a central recessed
portion for retainlng the toothed element in..a first,
typically non-engaged or neutral, position relative to the - ~
friction element. An inclined ramp portion is prouided on ~'
each blocking pin having a first end adjacent to an edge of
the neutral recessed portion and a second end recessed in
the blooking pin for retaining the toothed element in a
second, typically engaged, position re~ative to the
. friotion element. Locking means are resiliently.retained
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in the toothed element and urged into frictional engagement
with each of the blocking pins for eooperating with the L
rece5sed portions and the ramp portions to selectively
xçtain the toothed element in the engaged position.
I~ is an object of the present invention to reduce the
time required to shift ~rom one gear to the next in a
synchronized multi-speed transmi~sion.
It is another object of the present invention to
maintain the gear-changing elements of a synchronized
multi-speed transmission in a generally planar relati~nship
during shifting.
Other objects and advantages of the present invention
will become apparent to those skilled in the art from the
following detailed description of the preferred embodiment
when read in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is ~ sectional elevational view illustrating
the upper half of a prior art transmission synchronizer
assembly utilizing conventional blocking pins, wherein the
transmission synchronizer assembly is shown in a neutral
position.
Fig. 2 is a sectional elevation similar to Fig. 1,
wherein the prior art transmission synchronizer assembly is
shown in a selected gear engaging position.
Fig. 3 is a sectional elevational view illustrating
the upper half of a transmission ~ynchronizer assembly
utilizing improved blocking pins in accordance with the
present invention, wherein the transmission synchronizer
assembly is shown in a neutral position.
Fig. 4 is a sectional elevational view similar to Fig.
3 t wherein the transmission synchronizer assembly is shown
in a selected gear engaging position.
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DETAILED DESCRIPTION oF-~rHE PREFERRED EMBODIMEN~
~ R~ferxing now to the drawings, there is illustrated in
~igs. 1 and ~ the upper h~lf of a transmission synchroni~er .
assembly 10 which is known in the art. The transmis~ion
5 synchronizer assembly 10 includes a toothed element, such .
as a disk-shaped shift sleeve 12 having an outer annular
channel 14 connected by a generally flat central portion 16
to an enlarged inne~ sleeve portion 18. The outer annular ~
channel 14 cooperates with a manually operable shift fork ~-.
~not shown) to apply an axial shiftin~ force to the
transmission synchronizer assembly 10. The inner sleeve
portion 18 has a plurality of inwardly-extending splines 20
for engaging a drive~ output shaft (not shown) of the
transmission synchronizex assembly 10.
The inner sleeve portion 18 also includes a first
plurality of outwardly-extending splines 22 (only one is ;
illustrated) formed on one side of the shift sleeve 12 and
a second plurality of outwardly-extending splines 24 (only
one is illustrated) formed on the other side ~f the shift
sleeve 12. ~he first and second pluralities of
outwardly-extendin~ splines 22 and 24 are provided to
cooperate with respective first and second gear drive means
(not shown) which are each connected to an input shaft (not
shawn) in a known manner to selectively rotate the output
~5 shaft at two different 5peed ratios with respect to the
sp~ed of the input shaft.
A plurality.of apertures 26 (only one is illustrated)
are formed in the central portion 16 of the shift sleeva
12. Typically, six such apertures 26 are foxmed in the
ce~tral portion 16 and are spaced equidistantly
therearound. Each aperture 26 has a conventional blocking
pi~ 28 extending therethrough. Each blocking pin 28
includes an enlarged side re~ion 30 and a generally flat
tapered cam surface 32. In practice, the blocking pins 28
are disposed around the shift sleeve 12 such that the.side
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portions 30 are oriented in alternating fashion
sequentially about the shift sleeve 12.
Each blocking pin 28 also includes a central recessed
portion 34 formed on a generally flat inner surface 36 of
the pin 28, as shown most clearly in Fig~ 2. A locking
means is resiliently retained in central portion 16 of
shift sleeve 12 for cooperating with the recessed portion
34 of each blocking pin 28 so as to releasably retain the
shift sleeve 12 in a first position, such as the
non-engaged or neutral position illustrated in Fig. 1. The
locking means can include an outwardly-extending detent 38
which is slidably retained in and axially extending
aperture 39 formed in the central portion 16 of the shift
sleeve 12. The detent 38 is urged into frictional
engagement with the blocking pin 28 by a spring 40.
The ends of each blocking pin 28 are attached in a
known manner to respective synchronizing friction elements,
such as synchronizer races or cones 42 and 44. Each of the
synchronizer races 42 and 44 is an annular member having a
2n generally flat, threaded, tapered inner surface 46. A
plurality of axially extending channels 48 are formed in
the inner surfaces 46 of each of the synchronizer races 42
and 44. The threaded inner surfaces 46 and the axially
extending channels 48 of the synchronizer races 42 and 44
provide a path for draining transmission fluid or other
lubricant from the region of the inner surface 46 such that
a reliable frictional engagement with the corresponding
friction face in the selected gear drive means can be
obtained.
When it is desired to shift the transmission
synchronizer assembly 10 out of the first or neutral
position illustrated in Fig. 1 into a second or gear
engaging position, a shifting force is applied to the outer
annular channel 14 of the shift sleeve 12 by means of the
shift fork. Initially, the entire transmission
synchronizer assembly 10 slides a short distance along the
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~utpu~ shaft, typically .030 to .090 inch~s, until ~h~ .
inner sur~ace 46 of the synchroni.zer race 42 frictionally ~
e~gages the corresponding friction face of the desired ge~r .~.-
driYe meansG Such frictional engagement ~6 necessary to
synchronize the speeds of rotation of the input and output
shafts during the gear shifting process. After such ~peed
synchronization, additio~al ~hifting force causes the shift
sleeve 12 to slide axially with respect to the synchronizer
race 42 into the second position illustrated in Fig. 2,
~h~rein the first gear drive me~ns i8 engaged.
Durinq the above-described gear shifting process, it
will be appreciated that the shifting force applied to the .
shift sleeve 12 causes the detent 38 to overcome the urging
of the spring ~0 and retract inwardly withi~ the apertuxe
39 formed in the central portion 16 of the shift sleeve 12. .
Once removed from the recessed portion 34 of the bloc~ing
pin 28, the detent 38 slides along the flat inner surface
of the pin 28 until the shift sleeve 12 reaches the second
position. As disclosed in the prior art, a second recess
~not shown) may be ~ormed in the blocking pin 28 such that
the ~etent 38 may extend therein to releas~bly retain the
shift sleeve 12 in the ~econd position. A similar .
structur~ may be utilized to move the shift sleeve 12
towards the other synchro~izing race 44 into a third
position, wherein the second gear drive means is engaged.
Figs. 3 and 4 illustrate a similar transmission
synchronizer assembly 50 utilizing an improved blocker pin
52 in accordance with the present invention. The
structures of the shift sleeve 12 and the synchronizer - a
30 races 42 and 44 are identical to that described above and, - ~-
accordingly, identical reference..numerals are utilized to
descri~e these elements. ..The improved blocking pin S2
includes an enlarged.side region 54, a generally flat ~
tapered cam sur~ace 56, and a central recessed portion 58 .-
res?ectively similar.to the side portion 30, cam surface
32, and central recessed portion 34 described above. The
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blocking pin 52 additionally inGludes a pair of inclined .
ramp portions 60, each extending from a first end adjacent
to an edge Qf the central recessed portion 58 outwardly
toward a second end recessed to form recesse~ portion 62 in
5 the blocking pin 52. Although any desired incline may ~e ~,~
utilized for the ramp portion 60, it has been found
desirable that a gradual ramp of approximately twelve
degrees yield~ desirable results. o
In operation, when the applied shifting force begin~
10 to move t~e shi$t sleeve 1~ with respect to the
synchronizer races 42 and 44, the detent 38 will initially ,
be pushed radially inwardly within the aperture 39. .
However, once completely removed from the central recessed
portion 58, the deten~ 38 will begin to move axially
15 outwardly under the urging of the spring 40 as the shift
slee~e 12 slides farther along the inclined ramp portion 60 ~c
until it reaches the fully recessed portion 62 of the
second position illu~trated in Fig. 4~ ~
The in~lined ramp portions 60 provide several
20 significant advantages over the prior art blocking pins 28. P
The frictional engagement of the detent 38 with the
inclined ramp portion 60 of the blocking pin 52 generates
forces which tend to "pull" the shift sleeve 12 toward ~he
selected gear engaging position. It ha-s been ~ound that
25 the additional force required to return the shift sleeve 12
to the neutral position is insignificant. The frictional .
engagement of the detent 38 with the inclined ramp portion
60 also generates forces which reduce the time required to
shift from on~ gear engaging position to the other gear
30 engaging position. For example, if the transmission . x~
synchronizer assembly 50 is in the second position near the .
synchronizer race 42, as illustrated in Fig. 4, and it is
desired to shift to the third position near the other
synchronizer race 44, a shifting force is initially applied
35 to the shift sleeve 12. If the in~lined ramp portions 60
of the present invention were not present, the shift sleeve
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12 would initially move to the neutral position before the
transmission synchronizer assembly 50 would slide ac a unit
along the output shaft until the synchroni~er race 44
engages the riction~1 face of the second gear drive means.
~owever, when the inclined r~mp port~ons 60 are present in
the blocking pin 52, the transmission synchronizer assembly
50 will shift slightly along the output shaft as a unit in
the relationship illustrated in Fig. 4 until the _
synchronizer race 44 engages the friction face of the ~
lO second gear drive means. Thereafter, the shift sleeve 12 .
will move through the first or neutral position i~to the~.
third position. Also, it can be seen that the
above-descxibed movement o~ the transmis~ion synchronizer
assembly 50 causes the first synchroni~er race 42 to be
15 pulled out of frictional engagement with the first gear
drive means sooner than would otherwise occur. This
movement minimizes the effect due to runout.
Additionally, the present invention tends to maintain
the synchronizer races 42 and 44 in a generally planar
20 relationship with the shift ~leeve 12 during the shifting
process. The detents 38 in the shift sleeve 12 exert small
uniform forces about the synchronizer race 42 or 44 which
the shift sleeve 12 i5 moving towards. Such forces tend to
prevent cocking or other misalignment of the synchronizer
25 races 42 and 44.
In accordance with the provisions of the patents
statutes, the prinoiple and mode of operation of the
present invention have been explained and illus.trated in
its preferred embodiment. However, it must be apprec.iated L
30 that the present invention may be practiced otherwise-than -
3S specifically explained.:and illustrated without departing .
~rom its spirit or scope~ .
