Plate clutch for a motor vehicle

The invention is directed to a plate clutch with improved heat removal characteristics. For this purpose, additional axial and radial aerating openings are arranged in the torque-transmitting teeth of the clutch housing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is directed to a plate clutch having inner plates and outer 
plates and a housing with an internal toothing through which a torque is 
transmitted to said outer plates. 
2. Description of the Related Art 
Prior art plate clutches are known, for example, from German Patent 
Application 195 45 972.5. This known plate clutch is a clutch for a racing 
car and is outfitted with plates made from carbon material. Clutches of 
this type of construction are subjected to high thermal and mechanical 
stresses. In this connection, high loading occurs in the toothing region 
between the plates and the corresponding teeth. The area pressure at these 
locations is determined by the quantity of teeth and the dimensioning of 
the teeth. Although the area pressure in this region is reduced by a large 
quantity of teeth, the large quantity of teeth reduces the possible 
ventilation cross sections in the clutch housing. Accordingly, at least 
temporary temperature build ups must be accounted for in the design of 
these clutch housings. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to provide a plate clutch with 
improved heat removal characteristics. 
According to the invention, this object is met by a plate clutch with inner 
and outer plates and a housing having an internal toothing for 
transmitting torque to the outer plates, wherein the teeth of the internal 
toothing include first teeth and second teeth and axially extend along the 
entire axial length of the housing. The first teeth have longitudinal bore 
holes for receiving fastening screws. At least one of the second teeth is 
arranged between each adjacent pair of the first teeth. The housing has 
radial passages positioned between adjacent teeth of the internal 
toothing. By introducing longitudinal openings in the second teeth which 
communicate with radial openings through the radially inner ends of the 
second teeth to the longitudinal openings, the ventilation cross section 
as well as the surface of the plate clutch is appreciably increased. This 
improves the removal of heat substantially. In addition, the mass and mass 
moment of inertia of the housing are also reduced. At the same time, the 
temperature distribution is made more homogeneous along the circumference 
of the clutch housing. 
According to a further feature of the invention, the radial openings of the 
second teeth have essentially the same axial extension as the radial 
passages located between the teeth. This provides for an optimal aeration. 
It is further suggested that the radial openings open out radially inwardly 
preferably within the head region of the second teeth. A construction of 
this type is advantageous with respect to the mechanical strength of the 
housing. However, it is also easily possible to make the radial openings 
bigger than the head region of the second teeth; in this case, however, it 
is necessary to coordinate the size of the radial openings with the 
longitudinal openings with respect to strength. 
According to a further feature of the invention, the radial passages and 
the radial openings are divided into at least two rows in the axial 
direction and are separated from one another by at least one 
circumferentially extending, continuous web. Dividing the radial passages 
and radial openings axially into at least two rows in this way makes it 
possible to produce a particularly rigid housing. 
This web, of which there is at least one, is arranged axially in such a way 
that it is situated in radial alignment with one of the outer plates. An 
arrangement of this kind ensures that neither the air conduction nor the 
removal of abrasion is impeded by the web. 
It is further suggested that the fastening screws are constructed in the 
manner of expansion screws with guide regions in the axial end areas of 
the longitudinal bores and a reduced diameter therebetween, wherein radial 
openings are likewise arranged in the first teeth in the region of reduced 
diameter. As a result of this step, not only is the housing also 
ventilated in this region, but the fastening screws which are also 
subjected to heat by the flywheel are also ventilated.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
FIG. 1 shows a longitudinal section through a plate clutch 1. The clutch 1 
is concentrically arranged about an axis of rotation 4. The left side of 
the plate clutch 1 shown in FIG. 1 is fastenable to a flywheel (not shown) 
by fastening screws (see FIG. 5) which pass through a clutch cover 5 and 
through longitudinal bores 15 of a clutch housing 13. The clutch 1 has a 
hub 2 which is arranged so as to be fixed with respect to rotation by a 
toothing 3 and so as to be axially displaceable on a corresponding 
counter-toothing of a gear shaft (not shown). A plurality of outer plates 
11 and inner plates 10 are alternately stacked along the axial direction 
within the clutch housing 13. The hub 2 has an outer toothing 8 in its 
radially outer area. A corresponding toothing on the inner plates 10 
engages the outer toothing 8 so that the inner plates 10 are fixed with 
respect to rotation relative to the hub 2. An inner toothing 9 is arranged 
in the clutch housing 13. A corresponding toothing on the outer plates 11 
engages the inner toothing 9 so that the outer plates 11 are fixed with 
respect to rotation relative to the clutch housing 13. 
A diaphragm spring 7 is swiveably movably supported in the clutch cover 5 
for swiveling about spacer pins 6. The diaphragm spring 7 is operatively 
connected for applying a contact pressure force in its radial outer area 
via a pressure plate 12 for pressing all of the plates 10, 11 toward the 
flywheel and into frictional engagement with each other so that torque may 
be transmitted through the inner plates and outer plates 10, 11 from the 
clutch housing 13 to the gear shaft connected via toothing 3 to the hub 2. 
The clutch 1 is released by a clutch release system that acts on the 
radial inner end region of the diaphragm spring 7 for swiveling the 
diaphragm spring 7 around the bearing of the spacer pins 6 and thus 
cancelling its clamping force relative to the pressure plate 12 in its 
radial outer area. The annular clutch housing 13 is centered at the clutch 
cover 5 as well as at the flywheel via corresponding centering collars. It 
has radial passages 18 which enable a ventilation of the interior of the 
plate clutch 1, so that the temperature level inside the plate clutch can 
be limited and the abrasion particles created by abrasion occurring at the 
surfaces of the plates can be removed. 
FIGS. 2 to 5 show details of the plate clutch 1 which present additional 
ventilation of a plate clutch housing 13. FIG. 2 shows a side view of the 
clutch housing 13 and FIG. 3 shows a sectional view of the clutch housing 
13. The clutch housing 13 is an annular structural component part which 
includes radially inwardly projecting first and second teeth 14 and 17 
which correspond to a corresponding set of teeth on the outer plates 11. 
In this connection, the first teeth 14 have longitudinal bores 15 for 
receiving fastening screws 16. At least one second tooth 17 which is not 
intended for receiving a fastening screw but is likewise provided with a 
longitudinal opening 19 is arranged between every two first teeth 14 
arranged in the circumferential direction. The longitudinal openings 19 of 
the second teeth 17 are in communication with radial openings 20 which are 
shown in FIGS. 3 and 4. These radial openings 20 accordingly supplement 
along the circumference the already existing radial passages 18 which are 
arranged between the first teeth 14 and the second teeth 17. Further, it 
can be seen from FIGS. 3 and 4 that each of the radial passages 18 and the 
radial openings 20 are divided in two sections along the axial direction 
such that a circumferentially extending continuous web 21 remains between 
the two sections. This web 21 increases the stability of the clutch 
housing 13. Viewed along the axial direction, the axial position of the 
web 21 is arranged in such a way that it is aligned with one of the outer 
plates 11. Further, FIGS. 3 and 4 in combination with FIG. 5 show that 
radial openings 22 may also be arranged in the area of the longitudinal 
bores 15 of the first teeth 14. This is especially useful when the 
fastening screws 16 are constructed as expansion screws in accordance with 
FIG. 5. These fastening screws 16 are guided in their axial end areas of 
the longitudinal bores 15 by guide regions and have a reduced diameter 24 
axially between these guide regions 23. Accordingly, it is possible also 
to enable removal of heat in this region of the clutch housing 13 which in 
the present case serves also to stabilize the temperature of the fastening 
screws 16 which are also subjected to heat by the flywheel. 
The features described in FIGS. 2 through 5 increase the ventilation cross 
sections of highly loaded clutches so that radial ventilation is improved 
on the one hand and the surface area is increased on the other hand. 
Therefore, an improved removal of heat is achieved through both convection 
and radiation. This also produces an appreciable reduction in mass and in 
the moment of inertia which is a very desirable characteristic in race car 
clutches. 
The invention is not limited by the embodiments described above which are 
presented as examples only but can be modified in various ways within the 
scope of protection defined by the appended patent claims.