Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Short cardan ~oint and vehicle transmission equipped with
such a joint, and preferably with an electric retarder.
The invention relates to cardan joints comprising a
first fork or jaw integraI with an assembly flange, a
second fork or jaw integral wi-th a shaft section and a
journal cross whose four journals are mounted in twos on
the two forks with interpositioning of needle bearings or
similar.
It also relates to transmissions equipped with ~uch
cardan joints, which transmissions transmit the drive
torque from the gearboxes to the rear axles of the
vehicles.
For some of these transmissions, attempts are made
to shorten as much as possible the distance dl between the
centre O of the journal and the face F of application of
the flange of the joint against the associated flange of
the transmission.
This is in particular the case for certain
transmissions equipped with electric eddy current
retarders, or such equipment extends the transmission and
such an e~tension may raise serious problems.
Thus, in mcdern rear-engined coaches, the overall
length of the engine-gearbox assembly and that of the rear
axle, particularly of hypoid type, have increased latterly
without the respective locations` of these members ~being~
` modified.
Now, in ~the transmissions considered equipped with
electric retarders, the rotor of~the retarder is generally
30 ~mounted on a "gearbox flange" whlch~is cantilevered at the
output of a "nose" forming part of the ca~sing of the
; gearbox and whlch is estended~by a splined sleeve force
fitted~ in a complementary splined end inside the
gearbox.~
It is then against~the external face of this gearbox
flange that the flange~of the cardan joint the nearest to
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this gearbox is mounted.
Now, the distance d2 between the external face F on
which the gearbox flange is fitted and the front plane P
of the gearbox, against which is applied the mount
comprising the above nose, cannot be reduced below a
relatively large value if said gearbox flange is to
support the rotor of an electric retarder.
By way o indication, this distance d2 is ~or
example abou~ 115 mm for~a re-tarder whose outer diameter
is about 500 mm.
One of the essential aims of the invention is to
shorten as much as possible the distance D formed of the
sum of the two above distances dl and d2, i.e. the
distance between the centre O of the journal cross and
plane P.
For this, the distance dl is adjusted.
To give this distance dl a particularly low value,
the cardan joints of the above kind according to the
invention are essentially characterized in that the flange
integral with one of their two forks, which flange has, in
a way known per se, a flat or substantially flat end face
and is perforated with fixing holes, is formed axially
wi-th two through holes adapted to receive the arms of the
other fork when the bending angle of the joint is large,
which apertures are separated from each other by a central
spacer.
In preferred embodiments, recourse is further had to
one and/or other of the following arrangements :
- the contour of the flat end face of the flange of the
joint is circular,
- the fork integral with the flange of the joint is formed
b~ two parallel lugs f~ormed~respectively with two coaxial
bearings and the bases of these -two lugs are joined
together by three parallel spacers defining the above
apertures in twos,
~ - the central spacer has the~shape ot a thick =ylindrical
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bar whose cross section has the general shape of a
curvilinear triangle,
- the two end spacers are defined outwardly by a
cylindrical face of revolution about the axis of the
flange and inwardly by portions of a sphere centred on the
centre of the journal cross,
- the flange o the transmission on which the flange of
the cardan joint is fixed is itself formed with two
cavities disposed opposite apertures in the flange of the
joint and adapted to receive also the arms of the other
fork when the bending angle of the joint us large,
- in a vehicle transmission equipped with at least one
cardan joint of the above defined kind fixed on a "gearbox
flange" carrying the rotor of an electric retarder, this
rotor is fixed on said gearbox flange on an enlarged
periphery of this flange, via a tubular insert of the kind
described in the patent FRANCE no. 89 08045.
Apart from these main arrangements, the invention
comprises certain other arrangements which are preferably
used at the same time and which will be more explicitly
discussed hereafter.
In what follows, one embodiment of the invention
will be described with reference to the accompanying
drawings in a way which is of course in no wise
limitative.
Figure 1 of these drawings shows in axial section a
part of a vehicle transmission equipped with~an electric
;retarder and comprising~ a cardan joint according to the
invention;
~Figures 2 and;3 show on a larger scale, respectively
in an end view in the direction of arrow II of figure 3
and in axial section~through III-III of figure 2, one of
the~parts~forming~said~cardan~joint.
~` The cardan Jolnt~in quest~ion~comprises :
- a fixing flange l integral with~a first fork 2 defining
two bearings 3 (figures 2 and 3)~,~ said flange having a
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flat or substantially flat transverse end face with a
generally circular contour adapted to be applied axially
against a complementary flat transverse face of another
flange described further on,
- a second fork 4 defining two other bearings (not shown)
and integral with a shaft section 5,
- and a journal cross 6 comprising four journals 7, 8
adapted for cooperating respectively two by two with the
bearings of the forks 2 and 4 with interpositioning of
needle bearings or similar.
In general, this joint is associated with a second
identical joint provided at the opposite axial end of the
shaft section 5j which provides a homocinetic transmission
between the two end flanges of the two cardan joints, the
assembly forming a double cardan shat.
The problem which arises is that of reducing as much
as possible the distance between the centre O of the
journal cross of one at least of the two cardan joints and
the flat face F for mounting the corresponding flange so
that, for a given distance between the two mounting faces
which are generaIly parallel of the two flanges of the
double cardan shaft, a maximum distance is maintalned
between the centres of the two ~ournal crosses and the
angular free movements of said shaft are hindered as
little as possible.
For thls, two apertures 9 are formed through flange
1 for receiving the two arms of~fork 4 when the axis of
the shaft section 5 is highly slanted with respect to the
axis of the flan~e.
In the preferred embodiment illustrated, ~the 1ange
lO~on which the cardan flange l~is ;to be ~flxed ~has also
been formed with cavities ll disposed opposite apertures 9
and capable of receiving, like~these apertures, the arms
of fork 4.
With these arrangements,~the angular movements of
the shaft section 5 about the~ axls~common to the two
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journals 7 are no longer limited by the arms of said fork
4 abutting against flange 1, which makes it possible, all
other things being equal, to place the centre 0 closer to
face F, i.e. reduce the distance dl.
Thus, by way of example, with a construction of the
kind illustrated in the drawings and corresponding to the
above mentioned dimensions, it is possible to reduce the
value of said distance dl from 85 mm to 55 mm.
The gain thus obtained in shor~ening the axial
distance dl ~lS doubled if the two cardan joints of the
double cardan shaft considered are both construated in the
above way.
In the numerical example which has just been given,
the axial gain obtained is then 60 mm.
In the embodiment illustrated, the first fork 2 is
formed by two lugs having the general form of thick
parallel plates with a triangular contour formed with
bearings 3 and the bases of these two lugs are ~oined
together by three parallel spacers forming part of flange
1, namely a central spacer 11 and two edge spacers 12.
These ~.three spacers define between them in twos the
apertures g. : ,
The central spacer 11 has the form of ;a thick
rectilinear bar whose cross section is defined by an
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isosceles triangle with rounded corners: thus, this bar
has, faoing the ~ournal cross, slantlng faces 111, which
allows the maximum free angular movement of~this journal
cross as can be seen in figure 1. ~
The edge~ spacers~l2 ;are~ mlted ;outwardly by
portions of a continuous~ cylindrical ~face of revolution
121~extending over the~ whole periphery;of flange 1.~ ~
They are~de~flned lnwardly~by portions of a spherical
face 122 centred on the ~entre 0~of journal cross 6.
These can also~bè~sèen in figures 2 and 3 : ~
35 ~ stepped~bores 12~formed in lugs 2, for recèiving
the bolts or stud bolts for~;flxing flange~l on flange 10,
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- annular grooves 13 formed in bearings 3 for
receiving locking washers of the circlip type,
- and parallel teeth 14 provided on the fixing face
of flange 1 and adapted for cooperating with complementary
teeth provided on flange 10.
The gain obtained in shortening the distance d1 is
particularly valuable for vehicle transmissions which are
equipped with electric retarders such as is the case of
: the:preferred one illus~rated in figure 1.
In this transmission, the electric retarder
considered is of the type - known under the trademark
"FOCAL" - which is cantilevered, with a horizontal or
substantially horizontal axis, on the output of the casing
15 of the gearbox of the vehicle considered.
This retarder comprises an inductor stator 16 and an
induced rotor 17.
The stator 16 comprises a flange of a substantially
annular shape 18 which carries a ring of coils 19, even in
number, adapted so as to form by their ends two annular
successions of flat magnetic poles with polarities
alternatlng rom one to the next.
Flange 18 is mounted on the gearbox casing 15 - or
more precisely on an intermediate mount 20 itself fixed
against the 1at ront face P of said casing 15 - via a
structure 21 in the form of a star or an apertured bell
and tubular spacers 22.
Rotor 17 comprises two ferromagnetic material discs
23 adapted to surround the stator axially and so~that each
: one travels past a succession of poles of this stator from
30 which they~are separated by~a small olearance or airgap e.
~ Each disc 23 is;connected to~ a fixing ring 24 by a
: ring of curved arms 25 forming ventilation fins and the
: two :fixing ;rings 24 :are~:bolted~ by means of bolt-nut
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systems 26 on an intermed:iate~:annulus:~27.
~ The central:portion of:the~gearbox:~mount 20 has the
form~of a cylindrical nase 29 carrying, via an end bearing
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30, a sleeve 31 whose external axial end is extended
radially by flange 10, called in the present text "gearbox
flange".
The other axial end of sleeve 31 is splined inwardly
at 32 and is force fitted on the end piece 33 of the
gearbox, which is splined externally at 34.
Such force fitting is provided so as to avoid any
10 creation of play and it is then maintained by screwing
axially, into end piece 33, screws 35 whose heads are
applied against a plate 36 itself bearing on sleeve 31.
The rotor annulus 27 is fixed to the gearbox flange
10 in the way explained in the above mentioned patent.
In other words :
- the periphery of this flange 10 is enlarged and
comprises a ring of fixing elements 37,
- and annulus 27 is an external collar provided at an
axial end of a tubular insert 38 ribbed inwardly at 39,
20 whose other axial end is extended by an internal collar 40
itself fixed axially against the enlarged periphery of
flange 10 and flxed thereon.
SuGh fixing is obtained by cooperation of
appropriate means with means 37, these appropriate means
25 being in particular holes 41 and nuts 42 if said means 37
are stud bolts.
As mentioned above, the above described arrangements
make it possible to give a very low value to~the distance
D between plane P and the centre 0 of the~journal cross 6,
30 thls~distance being able to be reduced~to a value of only
170 mm for a retarder whose diameter is about 500 mm; more
precisely, said~ distance D is formed of distance d2
between plane P and face F ;along which the two flanges 10
and l are mutually applied, which distance is difficult to
~; ~ 35 reduce below~ 115 mm when the~gearbox flange 10 supports
the rotor of a retarder, and~distance dl between said face
F and centre 0, which distance~is here reduced to the very
low value of 55 mm.
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Following which, and whatever the embodiment
adopted, a cardan joint is finally obtained in which the
distance between the face of application of the flange and
the centre oE the journal cross is extremely small, which
makes its use very advantageous in a transmission equipped
with an electric retarder of FOCAL type when this
transmission must be very short and so extended to a
minimum by the positioning of such a retarder.
It should be noted that the provision of apertures 9
in flange 1 weakens this flange mechanically.
But such weakening is of no real disadvantage from
the point of view of transmission of drive torques from
journal 6 to the mounting flange 10.
In fact, the whole of such torques is transmitted at
the level of the two lugs 2 and it is thereore solely at
the base of these two lugs, between these bases and the
mounting flange 10, that it is necessary to provide a
large mechanically strong metal section, which is the
case.
In other words, the sole purpose here of spacers 11
and 12 is to maintain the two lugs 2 parallel and spaced
apart, they play no part in the transfer of torque.
This observation may explain the prejudice which
might exist before the invention with respect -to the
recessing of flange 1 which is claimed here.
As is evident, and as it re~sults moreover already
from what has gone before, the invention is in no wise
limited~ to those of its modes of~ application and
embodiments which~have been more especially considered; it
30 embraces, on the contrary,~ all~ the ~ variants thereof,
particularly those in which the cardan joint with
apertured~flange such as defined above, combined possibly
; with a corresponding apertured mountlng flange,~ is used in
a vehicle transmission not ~equlpped~ with an electric
35 retarder of FOCAL type.
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