Note: Descriptions are shown in the official language in which they were submitted.
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The invention concerns a spur change gear
unit, which can be switched when under load by means of
a double clutch.
Such units are known, but they have hardly
been applied in automatic gears for passenger and goods
vehicles.
This is not only due to the problem which is
caused by the selection mechanism, but also because of
the relatively high construction cost for the size of
the gear mechanism.
From the DE-PS 883 691 such a gear mechanism
is known, where four gear sets and six clutches not to
the load switchable clutches lead to five forward
gears. The favourable positioning of the two layshafts
in relationship to the two concentrically to each other
positioned drive shafts and the coaxial take off shaft
result, as shown in Figure 2, in a relatively
favourable change gear, which needs little space. The
disadvantages of this construc~ion are that there is no
reverse gear and when in one gear set - usually near
the gear take off - an intermediate wheel is added in
order to achieve a suitable reverse gear, this
represents in reality a four speed gear. The wastage
of space for the gears because of the many clutches and
for controlling them is too high. Furthermore,
synchronizers are needed for modern clutches which
results in higher costs.
It is therefore an aim of the present
invention provide a spur change gear having reduced
construction space and cost for the gears and
especially for the gear selection measured by the
advantages gained in the graduation of gears, including
the reverse gears.
In one aspect of the present invention there
is provided a spur change-speed gear unit shiftable
under load and comprising an input shaft, a
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double-clutch assembly formed by two first clutches
which are arranged to be engaged alternately under load
upon selection of successive forward gear ratios and
which are connected on their input sides to said input
shaft and on their output sides are respectively fixed
to a hollow driving shaft and to a radially-inner
driving shaft extending coaxially through said hollow
shaft, an output shaft coaxially aligned with said
driving shafts, first and second lay shafts disposed
parallel to, but offset from, said driving shafts, a
plurality of gear trains including a first gear train
for transmitting drive between the hollow driving shaft
and the first lay shaft, and a second gear train for
transmitting drive between the radially inner driving
shaft and the second lay shaft, and second clutches
selectively engageable in different combinations to
engage various gear ratios of the gear unit, in which
the arrangement of the gear unit is such that when the
unit is operating in at least one gear ratio both the
lay shafts and components of both the first and second
gear trains are simultaneously operative.
While in DE-PS 883 691 the first gear ratio
(gear set II) e.g. in 1st and 2nd gear, or the second
gear ratio (gear set I) e.g. in 2nd and 4th gear, are
used respectively and with that the torque-apart from
the direct gear - is directed via the first and second
layshafts, the construction in this application uses
the first two gear sets as well as the two layshafts
for the torque transmission for several gears
simultaneously, so that a considerably higher degree of
integraiion of the gear elements - wheels and switch
clutches - is achieved. In this way with the same
effect more gears can be gained or of course for the
same number of useful gears less effort is needed.
In accordance with one embodiment according to
the invention useful reverse gears can further be
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achieved favourably. Under certain circumstances this
can be a great advantage. Apart from that this gear
assembly with its positioning of the switch clutches
utilizes the structural space advantageously.
In accordance with a further embodiment
according to the invention it shows that this gear
construction is especially suitable for additions. If
in a generally known way a further gear path is added
near the take off further forward gears and as shown in
a further embodiment, further reverse gears can be
achieved. Under certain circumstances this can be of
advantage.
With the gear arrangement according to a still
further embodiment, the reverse gear assembly is
mounted on a separate shaft so that a short
construction length is achieved without considerably
increasing the gear cross section because this shaft
can easily be placed between the two layshafts. The
favourable axial dimension is largely due to the
assembly in third and fourth gear sets (double gear
wheel).
In order to give an approximate comparison in
construction efforts, the gear elements - gear wheels,
load switchable clutches, and clutches - are added in
the following table and then divided by the useable
gears, so that the resulting figure can be evaluated
technically as well as for the individual assemblies
according to that shown in the accompanying drawings
regarding their multiple use. For the gear assembly
DE-PS 882 691 a second intermediate wheel was added in
the second column, as this gear does not show a
provision for a reverse gear. The comparison in each
case is demonstrated with all useable gears and also
only with one reverse gear. Additionally it must be
taken into account, that the construction effort for a
switch clutch is much greater than for a gear wheel,
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that applies to the gear itself and above all to the
gear selection.
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Further details of the invention are given
bel~w by examples and drawings.
Figure 1 - gear diagram of a spur change gear
with double c~utch and switch clutches~and two
lay shafts as well as with coaxially positioned drive
and take off shafts.
Figure 2 - a diagram showing the clutches engaged
in the respective gear and the drive transmissions
for a gear according to Figure 1.
Figure 3 - a gear diagram as in Figure 1, but
with an additional gear set.
Figure 4 - a diagram as Figure 2, but in
accordance with gear diagram in Figure 3.
Figure 5 - a gear diagram as Figure 5, but
with a different reverse gear assembly.
Figure 6 - a diagram as Figure 2, but in
accordance with gear diagram Figure 5.
Figure 7 - a gear diaqram as Figure 3, but with
two reverse gear assemblies.
Figure 8 - a diagram as Figure 2, but in
accordance with gear diagram Fiyure 7.
Figure - a further gear diagram, especially with
a reverse gear assembly on an additional reverse
gear shaft.
~5 Figure 10 - a diagram as Figure 2, but in
accordance with gear diagram Figure 9.
The spur change gears as in drawings 1,3,5 and 7
have in common, that the double clutch A/B is
connected with the input shaft 1 via the outex
plate clutch. The first load switchable clutch
A is always fixed to a radially inside situated
drive shaft 2 and a first driving gear which as
well as to one half of the respective switch clutch
C via the inner plate clutch. The load switchable
- 35 clutch B is connected with a second driving gear
wheel 31 via the inner plate clutch and via a
drive sleeve shaft (3~. Furthermore the first
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gear ratio in the second gear set II is
formed by first driving gear wheel 21 and by the
gear wheel 61 which is firmly fixed on the second
layshaft. The drawings 1,3,5 and 7 have the
positioning of a clutch F,F' on the second
layshaft 6 in common, this makes it possible to
connect the layshaft with a rotatinq geax wheel
62 which is engaged with the second driving gear
wheel 31.
According to a desired construction this
clutch can be positioned axially between the two gear
~` sets F, but also outside, i.e. outside the
constant towards the direction of the input shaft.
The clutch F,F' is therefore able to connect
the two gear sets. Consequently the torque
can be transmitted from the first load switchable
clutch A to the second layshaft direct as well as
via the clutch F,F' the wheel 62 and the second
drive wheel 31 ~to the first layshaft 5.
Furthermore it is possible to drivè additionally
the first driving gear ~heel 21 in the opposite
direction via the same clutch F,F', driving of the
load switchable clutch B via the drive sleeve shaft
3 and the second driv ng gear wheel 31. The
positioning of this clutch is especially important
in connection with gaining one gear each at the
beginning and the end of the forward transmission
series - steep gradient gear and fast gear. As
can be seen in diagrams 2, 4, 6 and 8 a hill gear
can be obtained via clutch 4, clutch F,F' in
connection with afurther clutch E,K on the first
layshaft 5 and a fast gear vai clutch B, switch
clutch F,F' and the clutch for the direct gear C.
Figures 1, 3 and 7 have in common that on the
first làyshaft 5 in axial extension principally
between the first gear ratio, gear set I
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and gear set II, there is another reverse
gear assembly with a reverse gear clutch J
as well as a reverse gear wheel 54, which is
engaged via an intermediate wheel 55 withthe first
driving gear wheel 21 on the radially
inner drive shaft 2. For construction purposes
the reverse gear change can be positioned outside
as shown on diagrams 3 and 7, but it does not
change the principle of this assembly.
The positioning of the reverse gear on one of
the twolayshafts is especially important, as a
, reverse gear each is ob~ned via the load switchable
clutch A, as well as via the ~oad switchable clutch
B.
In Figure 1 is additionally on the first
layshaft a fixed clutch member, which serves the
double clutch D and E. This clutch member is able
to connect the first layshaft with its gear wheel
52 in the third wheel traction and the gear wheel
and the gear wheel 52 in the fou~th gear set.
Coaxially to the two drive shafts 2 and 3, a take
off shaft is firmly connected with the second half C2
of the clutch C - for the ~irect gear - and two
gear wheels ., 41 in the third and 42 in the fourth
gear set. The second layshaft 6 carries the
rotating gear wheel 63 in the thir~ wheel traction,
which can be connected with this second layshaft
via the clutch 61.
In Figure 3 the spur change gear has an additional
wheel track to diagram 1, so that on the first
layshaft there is fixed a clutch member of a clutch
K. The clutch K is able to connect the rotating
gear wheel 57 on the shaft 5 with this shaft. Also
in the fifth gear set the take off shaft 4
carries the fixed gear wheel 43 which is engaged
with the rotating gear wheel 57 un the first lay-
shaft. The fourth gear set is engaged with a further
wheel 64' on the second lay shaft ~ by.a clutch H.
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Figure 5 corresponds principally to ~igure
1, with the difference that the reverse gear
assembly is not placed on the first layshaft
between the two gear ratios, but on the
second layshaft 6, near the ~rive, where a reverse
gear clutch J' can provide the connection
of the layshaft with a reverse gear wheel 64,
which is gear linked via an intermediate wheel 65
for torque reversal with the fixed ~ear wheel
42 on the drive shaft in the fourth gear set.
It is not the practice, but it can be an
advantage to add to the spur change gear in Figure 3
a further reverse gear assembly in order to
obtain more load switchable reverse gears. That
is achieved by positioning on the second layshaft
6 an additional reverse gear assembly with a
clutch J" and a reverse gear wheel 67,
which is connected with a gear wheel 43 via an
intermediate wheel 68 on the take off shaft.
Of course it is possible to use the
lay out according to Figure 7 only with thls
reverse gear assembly and not to use the reverse
gear assembly J in the region of the driving
constants.
Figure 9 di~fers from the Figures 1, 3, 5
and 7 with the positioning of driving elements.
However the basic idea of multiple use of clutches
and gear wheels in a double clutch gear with two
countershafts remains the same in this example.
A common factor is also the positioning of a clutch
on the second layshaft 60 between the two
gear ratios, gear sets I and II, as well as
the positioning of the reverse gear assembly in
the region of the gear sets even if a separate
reverse gear shaft 7 is provided~ To simplify the
drawing~ this reverse gear shaft is placed level
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with the remaining shafts, whereas in the construction
it is basically placed between the lay shafts 50, 60
and the drive shafts - radially inner drive shaft 20
and drive sleeve shaft 30. Also the input shaft 10
is connected with the double clutch A/B by the plate
clutch. The first load switchable clutch A is fixed
to a radially inside situated drive shaft 2 and a
first driving gear wheel as well as to one half F1
of the switch clutch F via the inner plate c~utch.
The load switchable clutch B is connected with a second
driving gear wheel 31 via the inner plate clutch and
via a drive sleeve shaft 30. Coaxially to the two
drive shafts is a take off shaft 40 with the clutch
member F2 in the direction of the drive and near the
take off fixed. This shaft carries a rotating double
gear wheel 44/45 which is placed in the third,
and fourth gear sets respectively whereby this
double gear wheel can be connected with the take off
shaft via the clutch J, the gear connection in
the third gear set is via the gear wheel 510 on the
first lay shaft 50, it is fixed to this. The first
lay shaft 50 carries also the rotating gear wheel 520
in the first gear set with the coordinated clutch D and
- in the second gear set the gear wheel 530 with the
coordinated clutch E.
Also the second lay shaft 60 is gear linked with
the double gear wheel 44/45 on the take off shaft
in the fourth gear set II via a gear wheel 610 which
is fixed on the lay shaft. The lay shaft carries also
in the first gear set the rotating gear wheel 620
with the coordinated clutch 61 and in the second gear
set II the rotating gear wheel 630 with the coordinated
clutch H. The gear wheel 520 on the first lay shaft
S0 is gear linked to a fixed reverse gear wheel 71
on the reverse gear shaft 7. A further reverse gear
wheel 72 with a coordinated reverse gear clutch C
rotates on this reverse gear shaft and is gear linked
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to driving gear wheel 21 on the radially inner drive
in the second gear set.
T~e Figures 2, 4, 6, 8 and 10 do not need additional
explanations as the load switchable clutches A and B
as well as the engaged clutches C to K for the use
in respective gears can easily be read from these
tables. It can further be seen which gear trains are
completed by the respective gear paths upon
changing up or down. It can also be easily recognised,
that in the foxward gears, the clutches A ànd B are
alternatively used. A~so concerning the reverse gears
the load switchable clutches A and B are alternatively
used, but this conaition has not necessarily to be
adhered to concerning forward- and reverse gear series.
Finally the transmission ratios in all gears are
displayed in these tables.
The invention is not limited to the illustrated
spur change gears, but it is also possible e.g. to
construct gear assemblies with a larger number of
useful gears on the basis of this principle.
It is furthermore possible to vary the gear
connections slightly e.g. in Figure 9 the fixed reverse
gear wheel 71 can be gear linked with driving gear
wheel 31 and the rotating reverse gear wheel 72
with the rotating gear wheel 630 on the second
lay shaft 60.
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