Arrangement for securing a clutch to a crankshaft

In order to secure the flywheel (5) of a motor vehicle friction clutch (3) to the output end of a crankshaft (23) of an internal combustion engine, it is proposed that the flywheel (5) is fastened to the output end of the crankshaft (23) by means of an axially detachable centric clamping arrangement (21). The flywheel (5) is hereby supported on a pipe end (37) of the crankshaft (23). Conical expansion elements (45), which may be axially displaced by means of a centric screw element (43) to generate radial clamping forces, are inserted into the centric cavity formed by the pipe end (37). The screw element (43) is structured in such a way that it may be screwed through the hub (27) of a clutch disc (9) of the friction clutch onto the crankshaft (23) by means of a screw attachment tool (51). The friction clutch (3) may thus be preassembled together with the flywheel (5) to form a structural unit before it is secured to the crankshaft (23) .

BACKGROUND OF THE INVENTION 
The invention relates to an arrangement for coaxially securing an input 
component of a clutch, in particular of a friction clutch, to an output 
end of a crankshaft rotatable around an axis of rotation in an internal 
combustion engine of a motor vehicle. 
Conventional friction clutches in motor vehicles generally include a 
single- or twin-part flywheel, onto which a pressure plate unit is 
detachably screwed. The pressure plate unit includes an axially movable 
contact plate, which is arranged to be rotationally fixed, but axially 
movable on a clutch housing screwed to the flywheel and is biased towards 
the flywheel by a pressure spring, usually a diaphragm spring. The contact 
plate and the flywheel form friction surfaces for a clutch disc arranged 
between them, the hub of which is supported to be rotationally fixed, but 
axially movable on an input shaft of a gear arranged downstream of it in 
the drive section of the motor vehicle. The flywheel is, moreover, screwed 
onto an end flange of the crankshaft of the internal combustion engine by 
means of a plurality of screws arranged around the axis of rotation of the 
crankshaft. 
Viewed in axial direction, the clutch disc and the diaphragm spring in 
conventional friction clutches cover the screws securing the flywheel to 
the end flange of the crankshaft. Consequently, when assembling a friction 
clutch the flywheel must first be screwed onto the end flange, before the 
clutch disc can be put in place and the pressure plate unit can be screwed 
onto the flywheel. This assembly procedure is not only time-consuming, but 
also has the disadvantage that the friction clutch cannot be checked prior 
to assembly overall, that is including the clutch disc and the flywheel, 
to determine whether assembly regulations have been complied with. 
From DE-A 41 17 571 it is known to arrange holes in both the clutch disc 
and the diaphragm spring, which are axially flush with the screws provided 
for securing the flywheel to the end flange of the crankshaft. In this 
way, the pressure plate unit can be assembled together with the clutch 
disc and the flywheel to form one structural unit, hereafter also referred 
to as a modular clutch, prior to installation on the crankshaft. The 
fastening screws may be tightened through the holes in the clutch disc and 
the diaphragm spring into the end flange of the crankshaft. 
It is known from DE-A 33 15 232 to screw a friction clutch comprising 
flywheel, pressure plate unit and clutch disc, whereby the clutch housing 
borders the flywheel, i.e. is not detachably connected thereto, to the 
output end of the crankshaft by means of a central screw. The output end 
of the crankshaft contains a centric front opening provided with an 
internal thread, into which the central screw is screwed. The central 
screw has a radially projecting flange, which clamps the flywheel against 
the axial face of the output end of the crankshaft. The torque, which may 
be transmitted via the radial flange of the central screw, is however 
comparatively low, since only restricted fastening torques of the central 
screw may be achieved. 
It is known from DE-A 40 13 298, for securing the flywheel of a friction 
clutch, to provide the axially facing surfaces of an end flange of the 
crankshaft and the flywheel with a radial gear tooth system (Hirth 
serration), and to axially fix the flywheel to the output end of the 
crankshaft by means of a central screw. The central screw is provided with 
centric key faces to accommodate a screw attachment tool. 
It is known from the book .Die Motoren der Personenkraftwagen. (Automobile 
Engines), by K. Wiecking and R. Gebauer, Verlag Chr. Belser, Stuttgart, 
1952, page 314, FIG. 341, to secure the flywheel of a conventional 
friction clutch to the output end of the crankshaft of an internal 
combustion engine by means of a cone press-fit joint. The output end bears 
an external cone tapering towards the clutch disc, on which the flywheel 
is mounted by an internal cone of its hub. The output end of the 
crankshaft ends in a screw journal, onto which a nut locking the flywheel 
is screwed. 
Finally, it is known from the German Gebrauchsmuster 90 16 961 to provide a 
clamping joint between a shaft rotating around an axis of rotation and the 
hub of a component concentric to the axis of rotation. Conical elements 
are distributed over the periphery of the hub in conical recesses, and may 
be tightened in axial direction into the corresponding recesses by means 
of screws. The conical elements cause radial deformation of the hub and 
thus generate clamping forces acting on the shaft. 
SUMMARY OF THE INVENTION 
The invention provides an easy to handle and nonetheless operationally safe 
arrangement to coaxially secure an input component of a clutch, in 
particular a friction clutch, to an output end of a crankshaft, which is 
rotatable around an axis of rotation, in an internal combustion engine of 
a motor vehicle. 
This aim is achieved according to the invention in that the output end of 
the crankshaft is in the form of a pipe end concentric to the axis of 
rotation, onto which pipe end the input component of the clutch with a 
centric hub opening is mounted, and that conical expansion elements are 
inserted in a centric cavity formed by the pipe end, which may be axially 
displaced by means of a centric screw element to generate radial clamping 
forces. 
In this way, a clamping joint between the input component of the clutch and 
the output end of the crankshaft may be provided or released again by a 
single screw element. This not only simplifies handling, but also the 
manufacture of the fastening arrangement, since all the components 
required here extend concentrically to the axis of rotation of the 
crankshaft and can therefore be manufactured simply and precisely. 
The clutch is preferably a friction clutch, but hydrodynamic clutches or 
torque converters may also be secured in the same manner. The input 
component concerned may be a flywheel of the internal combustion engine, 
which can be a one-mass flywheel or a flywheel having two masses which may 
be rotated relative to one another around the axis of rotation. The term 
conical expansion elements relates to any elements, which permit radial 
expansion forces to be exerted on the pipe end by means of axial 
displacement of the expansion elements in relation to the pipe end, e.g. 
conical spreaders which may be drawn into the cavity by means of the screw 
element. The screw element may in this case be screwed to the pipe end or 
an adjacent area of the output end of the crankshaft. 
Both the conical expansion elements and the screw element can be separate 
structural components in this case. However, in an expedient embodiment 
these components form an integral part. The screw element in this case has 
a conical external thread to form the conical expansion elements and is 
screwed into an internal thread of the pipe end. The pipe end preferably 
has at least one radially continuous slot extending axially at least over 
a part of the pipe end. This ensures higher elasticity in radial direction 
so that an acceptable clamping joint may be produced even where the 
starting torque of the screw element is comparatively low. For expedience, 
several slots may be provided over the periphery. 
The pipe end preferably has an axial stop for the input components of the 
clutch. This ensures that the axial position of the clutch is exact before 
the clamping joint is closed. 
The outer casing of the pipe end and the inner casing of the hub opening of 
the input component are advantageously cylindrical. Such joint surfaces 
may be produced accurately with sufficiently low tolerances to prevent 
tilting errors and suchlike. However, it can be expedient to improve the 
impact stability of the clamping joint by providing the outer casing of 
the pipe end with an external thread and the inner casing of the hub 
opening of the input component with an internal thread screwed onto the 
external thread. In this embodiment, the input component is screwed onto 
the pipe end before the clamping joint is closed. This type of fastening 
provides a joint which is not only frictionally engaged but also 
positive-locking and is particularly secure, especially in the case of 
sporadic or sudden load application. 
The arrangement according to the invention for securing the clutch to the 
crankshaft is particularly suitable for modular clutches, i.e. friction 
clutches, in which the clutch disc acting as output component of the 
friction clutch is joined together with the flywheel and the pressure 
plate unit comprising the contact plate, the clutch housing and the 
pressure spring, to form a structural unit prior to installation of the 
friction clutch. The screw element is in this case expediently provided 
with tool working surfaces, which through a hub opening in the clutch disc 
provided for coupling with a gear input shaft, are accessible for a screw 
attachment tool which may be inserted axially through the hub opening. In 
this way the expansion elements, which are initially only provisionally 
fixed to the crankshaft by means of the screw element, may be centrically 
clamped through the hub opening of the clutch disc after mounting of the 
clutch component. The clamping joint is clamped and released in a single 
work step. The screw element is preferably provided with a centric 
contoured hole to accommodate the screw attachment tool to allow better 
guidance of said tool. The contoured hole and the hub opening of the 
clutch disc expediently have like cross-sectional contours, generally in 
the form of an internal gear tooth system, and this simplifies manufacture 
and guidance of the screw attachment tool in the hub opening of the clutch 
disc, with a suitable tool design. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to, and forming part 
of, this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

FIG. 1 shows a motor vehicle friction clutch 3 rotating during operation 
around an axis of rotation 1 with a flywheel 5, a pressure plate unit 7 
and a clutch disc 9. The pressure plate unit 7 comprises a clutch housing 
11, which is secured detachably or undetachably to the flywheel 5, a 
contact plate 13, which is attached in a manner not shown in more detail, 
e.g. by means of tangential leaf springs, so that it is rotationally fixed 
but axially movable on the clutch housing 11, and a pressure spring, in 
this case in the form of a diaphragm spring 15. The diaphragm spring 
clamps the contact plate 13 against the flywheel 5 forming a matching 
contact plate by means of friction linings 17 of the clutch disc 9. The 
friction linings 17 are disengaged and the friction clutch 3 is released 
by axial movement of the tongues 19 of the diaphragm spring 15. 
The flywheel 5 is detachably secured to the output end of a crankshaft 23 
rotating around axis 1 in a motor vehicle internal combustion engine, 
which is not shown in further detail. The clutch disc 9 itself has a hub 
27 provided with an internal toothing 25, by means of which the clutch 
disc 9 is coupled so that it is rotationally fixed but axially movable on 
an input shaft of a motor vehicle shift transmission (not shown in further 
detail), which may be arranged in a pilot bearing 29 of the crankshaft. 
The friction clutch 3 is what is known as a .modular clutch., which may be 
installed in one work step on the crankshaft 23 as a preassembled, 
complete structural unit comprising the pressure plate unit 7 as well as 
the flywheel 5 and the pressure plate unit 7 as well as the flywheel 5 and 
the clutch disc 9. During preassembly, the clutch housing 11, diaphragm 
spring 15, contact plate 13 and clutch disc 9 are preassembled, whereby 
the clutch disc 9 has already been centered. The entire structural unit 5, 
9, 11, 13 and 15 may then be mounted on the output end of the crankshaft 
23 and secured to the crankshaft 23 in one work step by means of the 
clamping arrangement 21. 
As shown best in FIG. 3, the flywheel 5 has a hub 31 with a centric, 
cylindrical hub opening 33, with which it is mounted on a cylindrical 
outer surface 35 of an axially protruding, centric pipe attachment 37 of 
the crankshaft 23 at the output end of the crankshaft 23 to form a narrow 
pass. An axial stop 39 of the crankshaft 23 positions the flywheel 5 in 
axial direction. 
The inner circumferential surface of the pipe attachment 37 is provided 
with an approximately conical internal thread 41, into which is inserted a 
screw element 43 (FIGS. 1 and 2) concentric to the axis of rotation 1. The 
screw element 43 has an approximately conical external thread 45 on its 
outer periphery, which is screwed into the internal thread 41 of the pipe 
end 37 with its smaller diameter first. The screw element 43 expands the 
pipe end 37 radially. The radial compressive forces generated hereby 
frictionally engage the hub 31 of the flywheel 5 at the output end of the 
crankshaft 23. To increase its radial flexibility, the pipe end 37 is 
provided with radially continuous slots 47 extending axially at least over 
part of the length of the pipe end 37. The slots 47 are distributed in 
peripheral direction and, if need be, may all be omitted. For installation 
of the modular clutch, the screw element 43 is essentially loosely 
inserted into the pipe end 37 and then the flywheel 5 of the modular 
clutch 3 is mounted on the pipe end 37. The screw element 43 has a 
contoured centric hole 49, the cross-sectional contour of which is 
preferably the same as the cross-sectional contour of the inner tooth 
system 25 of the clutch disc 9, which means that the same production tools 
may be used for the manufacture of both the hub 27 and the screw element 
43. In order to clamp the clamping joint 21, the shaft 53 of a screw 
attachment tool 51 is first passed through the hub 27 of the clutch disc 9 
into the contoured hole 49 of the screw element 43. The end of the shaft 
53 is provided with a coupling contour 55 corresponding to the contoured 
hole 43. The screw element 43 is screwed through the hub 27 of the clutch 
disc 9 into the pipe end 37 by means of the screw attachment tool 51, 
whereby the pipe end 37 expands and the clamping joint between the pipe 
end 37 and the hub 31 of the flywheel 5 is clamped. The shafts 53 of the 
screw attachment tool 51 may in this case be guided in the pilot bearing 
29 with a suitable extension, to ensure that the fastening procedure is 
carried out with a high degree of precision. After the clamping joint 21 
has been clamped, the screw attachment tool 51 is withdrawn so that the 
shift transmission may be installed with its input shaft first into the 
modular clutch. 
The inner surface of the opening 33 of the hub 31 of the flywheel 5 and the 
outer surface 35 of the pipe end 37 may each be in the form of smooth 
cylindrical joint surfaces so that the flywheel 5 is exclusively engaged 
frictionally on the pipe end 37. As indicated at 57 in FIG. 3, however, 
the outer surface 35 and the inner surface 33 may also be provided with a 
thread. The flywheel 5 is in this case screwed onto the pipe end 37 until 
it abuts the stop shoulder 39 before the clamping joint 21 is clamped and 
is thus both frictionally and positively engaged on the crankshaft 23 
after the clamping arrangement 21 is clamped. The clamping arrangement 21 
explained above permits the modular clutch 3 including the flywheel 5 to 
be fastened quickly and securely to the crankshaft 23. In the same way, 
the modular clutch 3 may also be very easily released from the crankshaft 
23 again. It goes without saying that in modular clutches 3 with a 
detachable pressure plate unit 7 on the flywheel 5, the pressure plate 
unit 7 may be removed as well as a unit from the flywheel 5, as is usual 
in conventional clutches. 
In the embodiments explained above, the conical external thread 45 of the 
screw element 43 forms an integral part with expansion elements connected 
thereto for radial expansion of the pipe end 37. It goes without saying 
that these expansion elements may possibly also be separate from the screw 
element, for example in the form of an additional cone element, which is 
then drawn into the pipe end 37 by the screw element, which may be screwed 
to the crankshaft 23 by means of a standard cylindrical thread. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.