Note: Descriptions are shown in the official language in which they were submitted.
~214812
DRIVE LINE FOR A TRACK-LAYING VEHI~LE X1551
This invention relates to a drive line for a
~rac~-laying vehicle such dS a military tank,
and in particular to a drive iine employing
speed shaft steering.
The invention consists in ~ drive line for a
trac:~ iaying venicle 'navlng ,?eed shaC.
steer.ng, comprising two track drive sh~fts and
a drive transmission whose output drives a shaft
coupled to both track drive shafts by way of
epicyclic gears having furt'ner inputs for
steering, whereby the said shaft normally
rotates while the vehicle is stationary,
characterised in that the ~rive transmission has
a continuously-variable ratio, and in that the
drive transmission drives the shaft by way of a
transfer system operable in at least low regime
I and low regime II modes, the transfer system
having a summing epicyclic gear arranged to sum
the input and the output of the drive trans-
mission and to provide a summed output, and
coupling means for coupling the said summed
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output to the said shaft in either rotational
sense to select either Low regime I or low
regime II modes, low regime I being operable for
~ehicle velocities from rest to ~ cirst
S predeter~ined velocity, and 'ow regime II being
operabLe from the first to a second, higher,
pre(letermined velocity.
I.~ the preferred orm of drive line, ~he
- coupling means changes mode synchronously
between low regime I and low regime II, the said
shaft being stationary at the changeover point.
L~oreover, in the preferred embodiment the
transfer system is further operable in a high
regime mode in which the said summing epicyclic
gear is locked and links the output of the drive
transmission directly to the input of the
coupling means, the input of the drive
transmission being free to rotate relative to
the transfer system.
In order that the invention may be better
understood, two preferred embodiments will now
be described with reference to the accompanying
drawings, wherein:-
~2~4812
-- 3 --
Figure ] is a schematic diagr~m of a drive line
Eor a trac'~-'3ying vehi~le ha~ ;pee~ snaft
-,r,~ ing,
FiJure 2 is ~ liagram showing .~ lrive 'ir.e .n
accordance ~i.h ,~ st ~ lellt of -he
invention and
Fi,;.u-e 3 is .~ diagra~ , drive line In
accordance with a second e.~Dodi~ent of ~he
invention.
iO Figure 1 is a schematic illus~ration of a ;lrive
line for a track-laying vehicle naving speed
shaft steering and incorporating a continuously-
variable ratio steering transmission, in
accordance with the invention of our 3ritish
patent application number 8322936. The drive
line of Figure l is described in detail in our
co-pending application, and no ~ore than 3 brief
description will be yiven ~ere.
Drive I from the-tank engine is coupled both to
a summing epicyclic gear J and to the input of a
continuously-variable ratio transmission K, for
ex~mple of the toroidal race rolling traction
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-- 4 --
type. The olltpllt o~ ~he ~ontinuously-variable
ratio steering transmission K is coupled both to
a further inpllt of t'ne summing epicycLic gear ~,
and also .hrough s~it~-lble gearing P to a urther
summing epicyclic gear M whose output drives one
of the tank ~racl~ ~rive shafts. The sut~ut of
'he summing epicyclic gear J is connecs~d via
suitable ge~ring ~ ~o a further summing
epicyclic gear L whose output drives ~he ,th~r
_a.ik ~-~ack ~rive shaft. Each summing epicyclic
gear L, `1 has a Eurther input driven i/ ~y the
tank engine. The tank nas speed shaft steering,
as opposed to null shaft steering, i.e. there is
a rotating steering input to both epicyclics L,
M when the tank and its track drive shafts are
slationary.
Figure 2 shows the first embodiment of the ~rive
line according to the invention. Tn this
example, a continuously-variable ratio
transmission 100 acts as a steer variator, and a
similar continuously-variable ratio transmission
200 transmits driving power from the engine
through a transfer system to a cross shaft 18,
l9 and thence to respective tank track drive
shafts 20, 30~
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mhe steer variator 100 receives its drive input
from the engine crankshaft 1 by way of gearing
2, 3. Geari~lg 3 is soupled to the input sha
of the steer variator and also to the ~-1nnulus 53
of a simple epicyclic gear 3. The outp~. shaft
8 of the steer ~a.iator is connected at one end
through gearing 81, 82 to the sun gear ~1 of a
si,~ple epicyclic gear 7 whl-h supplies lrive to
drive shaft 20. The other end of the output
shaft 8 of the steer variator 100 is connected
to the sun gear 51 of the simple epicyclic gear
5, of which the planet carrier 52 is connected
to drive the sun gear 61 of simple epicyclic
gear 6 by way of yearing 5~, 55.
As explained in our co-pending patent
application referred to above, the simple
epicyclic gear 5 causes the gears 54 and 81 to
rotate in opposite rotational senses. The
change of ratio introduced by the simple
-0 epicyclic gear 5 is compensated for by suitably
selecting the ratio of gearing 55 and 82; in
this example, gearing 55 provides a ratio of
- 2.86 and gearing 82 a ratio of + 1Ø Simple
epicyclic gear 6 sums the drive from the cross
lZ1481Z
6 --
shaft (at 18) and from the steer variator to
provide a steered output on drive shaft 30.
Simple epicyclic gear '- sums the drive From the
~ross shaff (19) and .rom ~he steer varlator to
provide a steered output on drive shaft 20.
The ~rive 'ine or the inver:~lon employs speed
snaft steerlng, which means that _he sun gears
~1, .1 as ,iell as -he annuli ~3, '3 of simple
epicyclic gears G, 7 respectively are made to
rotate when the tank drive shafts 30, ,0 are
stationary. Both the steering input (from
gearing 55, 82) and the cross shaft 18, 19 are
rotating when the tank is stationary. The
invention lies particularly in the manner in
which drive is supplied from the drive
transmission 200 fo the track drive shafts 20,
30.
transfer system comprising an epicyclic gear
arrangement 12, 13, 15 and brake B and a
~0 coupling means consisting of clutches Cl, C2 and
gears 16, 17 allows the drive line to be
operated in four distinct regimes for optimising
its performance. The four drive regimes are:
l'Z148~2
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reverse, low I, low II and high, corresponding
respectively to tank speeds in reverse, low
forwar~, medium forward and high forward.
Input shaft 10 of drive variator 200 is joined
to the iun gear of simple epicyclic gear 12 of
which 'he planet carrier may be held Dy a brake
B and of which the annulus is connected to the
planet ~,arrier of a second simple epicyclic gear
13. The output shaft 11 of the drive variator
200 is connected to the sun gear of the second
simple epicyclic gear 13. The annulus 15 of the
second simple epicyclic gear 13 provides an
output in one rotational sense to gear 16, and
in the opposite rotational sense to gear 17 of
the coupling means. The coupling means employs
clutches CL and C2 to engage to the cross shaft
18, 19 either gear 16 or gear 17 according to
the reyime selected. A clutch H is operable, in
two of the regimes, to lock the planet carrier
to the annulus in the second simple epicyclic
gear 13.
For the reverse regime, clutch H is engaged and
clutch Cl is engaged. The input shaft 10
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-- 8 --
rotates freely relative to the transfer system
since brake B is not applied. Output shaft 11
drives annulus 15 directly, which in turn drives
the cross shaft through gear 16 and clutch Cl.
The high regime, for the highest forward speeds,
is engaged by engaging cl~tch L~ and engaging
clutch C2. It operates in tr.e same way as the
reverse regime except that annulus 15 rotates
gear 17 in the opposite rotational sense. For
low I regime clutch H is not engaged, clutch Cl
is engaged, and brake B is applied. Simple
epicyclic gears 12, 13 then act to sum the
inputs from input shaft 10 and output shaft 11
and supply a summed output through annulus 15
and gear 16 to clutch Cl. For low II regime,
clutch C2 is engaged instead of clutch Cl,
effectively reversing the drive to the cross
shaft.
The cross shaft 18, 19 is stationary only at the
changeover between low I regime and low II
regime, allowing this change to proceed
synchronously. Thus, as the tank proceeds
forwards from rest, it commences in low I regime
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g
with the cross shaft being decelerated as the
tank is accelerated. At a first æredetermine.1
forward speed, when the cross shaft is
stationary, the change of regimes is effected.
Upon further acceleration of the tank, the cross
shaft accelerates in the opposite direction
until a second predeterminea forward speed is
attained. The transfer system is preferably
designed for synchronous change between low II
and high regimes, so that there is no relative
movement between the plates of clutch H at the
second predetermined forward speed. As the tank
accelerates in high regime, the cross shaft
accelerates from its second predetermined
forward speed to its highest speed.
Figure 3 shows the second embodiment of the
invention, which also operates in the four
regimes. The only significant difference from
the first embodiment is that the clutch H is
replaced by clutches F and R, and a third simple
epicyclic gear 14. This second drive line is
more efficient than the first, since losses in
the variator 200 are significantly reduced, but
this is at the expense of the extra clutch and
gearing 14.
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For high regime, both clutches F and R are
engaged, ~nd have the same effect as the clutch
H of ~igure 2. For reverse regime only clutch R
is en~aged. For iow I and Iow LI regimes, the
S brake 3 is applied, clutcn R .s disengaged and
clutc:h F is engaged. .;part from these
iifferences, the transfer system operates in .he
same way as in the first emDodimerlt of Figure ~.
The principal advantage obtained by the
invention, which is apparent ln both embodiments
described above, is that the same transfer
system is used for both parts of the low regime,
low I and low II, enabling smaller variators to
- be employed than would otherwise be the case for
1~ an equivalent performance.
A further advantage with the second embodiment
arises from the provision of both clutches F and
R. In slippery conditions, for example, it is
sometimes desirable to start the tank from rest
~o with both clutches engaged; they then act
effectively as a transmission brake, preventing
the sudden acceleration of only one track.
Moreover, with both clutches F and R engaged, a
-- 1 1 --
neutral turn can be achievec`., with the tracks
being propelled in opposite rotational senses
while ~he tank is stationar~.
