Flywheel arrangement with an added mass

A flywheel arrangement with a drive-side transmission element and a driven-side transmission element which is rotatable relative to the drive-side transmission element includes at least one annular added mass fastened to at least one of the transmission elements. In order to produce the added mass, a blank formed from strip material is shaped in its longitudinal direction to form a ring, so that the corresponding ends of the blank are directed toward one another with a predetermined intermediate gap and are fixed in this position relative to one another by a retaining mechanism.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is directed to a flywheel arrangement with a drive-side 
transmission element and a driven-side transmission element with an added 
mass fastened to at least one of the transmission elements. 
2. Description of the Related Art 
German reference DE 43 39 421 A1 discloses a flywheel arrangement with a 
transmission element on the drive side in the form of a first flywheel and 
a transmission element on the driven side in the form of a second 
flywheel, wherein the second flywheel is rotatable relative to the first 
flywheel. An annular added mass is fastened to one of the flywheels, 
namely the flywheel on the drive side. This added mass is provided, 
according to FIG. 1, at the side facing the crankshaft. On the other hand, 
according to FIG. 7, an annular added mass having an angular cross section 
is fastened to the transmission side of the flywheel on the drive side. 
Accordingly, the location at which such added masses can be arranged can 
be freely selected. 
While the above German reference shows the advantages of an added mass of 
this kind, the manufacturing effort is considerable, especially when this 
added mass has an angular cross section as shown in FIG. 7. Such annular 
added masses are often produced from solid material by chip-removing or 
cutting machining. The material cost and production cost are accordingly 
very high. If this problem is avoided by producing the added mass in 
multiple parts, a precise alignment of these parts relative to one another 
is problematic because unwanted imbalances are easily introduced in the 
flywheel arrangement. 
SUMMARY OF THE INVENTION 
The object of the invention is to develop an added mass in a flywheel 
arrangement that is produced at the lowest possible expense in materials 
and costs. 
This object is met by forming the added mass from a blank made of a strip 
material that is shaped in its longitudinal direction to form a ring so 
that the longitudinal ends of the blank are directed toward one another 
with a predetermined intermediate gap and are fixed in this position by a 
retaining means. Through the use of a blank produced from strip material, 
the blank can be dimensioned with respect to length such that when it is 
shaped to form a ring, it retains the exact diameter required by the added 
mass. It is recommended that work processes to be carried out on this 
blank are performed before the blank is shaped into a ring, since these 
work processes can be carried out on a flat structural component part 
substantially more simply and more economically than with a 
multi-dimensional structural component part. For example, open locations 
in the form of cut out portions, notches or recesses can be produced by a 
punching process, wherein supplementary functions can be performed through 
these open locations in the subsequent flywheel. It is conceivable, for 
example, to provide cut out portions that are suitable for inserting tools 
such as a wrench to access corresponding fasteners. Further, notches or 
recesses may be used as signaling means during the rotation of the 
flywheel arrangement, and accordingly of the added mass, wherein the 
signals are used for controlling the motor by acting as ignition marks. 
As soon as these open locations are formed in the blank, the blank can be 
worked into the shape of a ring. Different methods are possible for 
maintaining this ring shape. For example, a rim that is usually provided 
at the flywheel arrangements in the form of a gear ring or toothed rim can 
be pushed over an axial area of the ring acting as added mass. In this 
configuration, the rim acts as retaining means for the ring by holding the 
ring under radial pretensioning. Prior to placing the rim over the ring, 
the ring may be pretensioned such that the gap between the ends of the 
ring is closed. In this condition, the rim easily slips over the ring and 
the ring is released in the rim to hold the ring in the rim. The ring and 
rim may also be assembled by fixedly connecting the two ends of the ring 
by welding them together or simply by fixing them together temporarily 
until some other means can be used after the ring is mounted to prevent 
them from springing apart as was described above. 
It is perfectly acceptable for the ends of the ring to extend within the 
area of an open location. This has the advantage that the resulting joint 
gap will not lead to erroneous signal detection, 
It will be appreciated that this shaping process is carried out in a 
relatively simple manner, provided that the blank in the form of a flat 
structural component part is shaped into a ring. However, it is more 
difficult to produce a ring with an angular cross section, although a 
solution for this is likewise provided for. For this purpose, 
interruptions are produced in a punching process, possibly in the same 
punching process in which the above-mentioned open locations are produced, 
wherein these interruptions extend from one side of the blank toward the 
opposite side, but only over part of the width of this blank, a tongue 
being formed therebetween in each case. It is clear that these tongues, in 
view of their small dimensions in the longitudinal direction of the blank, 
will offer relatively slight resistance to the shaping of the blank into a 
ring. This is still the case, moreover, when the tongues are subsequently 
bent relative to the rest of a ring formed in this way to produce the 
angular cross section. In this way, an added mass of the desired cross 
section is formed without the need for high tangential forces or the 
introduction of stresses in the material due to high shaping forces. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of the disclosure. For a better understanding of the invention, its 
operating advantages, and specific objects attained by its use, reference 
should be had to the drawing and descriptive matter in which there are 
illustrated and described preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
Referring initially to FIG. 1, a flywheel arrangement 100 includes a 
transmission element 1 on its drive side in the form of a flywheel 2. The 
flywheel 2 has a primary flange 4 which extends on the radial outer side 
of the flywheel 2. A radial inner end of flywheel 2 is connected with a 
hub 5 by fastening means 7 which further serve to connect the flywheel 
arrangement 100 to a crankshaft 8 (shown schematically in dash-dot lines) 
of a driving means, such as for example, an internal combustion engine 
(not shown). 
The primary flange 4 comprises an axial portion 10 in its outer 
circumferential area. A cover plate 12 extends radially inward and is 
fastened to this axial portion 10. A grease chamber 13 which is filled at 
least partially with viscous medium is formed axially between the primary 
flange 4 and the cover plate 12. Elastic elements 16 of a torsional 
vibration damper are inserted within the grease chamber 3. These elastic 
elements 16 are controllable by control elements 15 that are provided on 
the sides of the grease chamber 3 at the primary flange 4 and at the cover 
plate 12. The elastic elements 16 are supported at a hub disk 18 which is 
connected by rivets 19 in the radial inner region with a flywheel 20 which 
acts as a transmission element 22 on the driven side of the flywheel 
arrangement 100. Flywheel 20 is rotatably supported by a bearing 23 on the 
hub 5 of the transmission element 1 on the drive side. Both transmission 
elements 1 and 22 are rotatable about a center axis 35 of the flywheel 
arrangement 100. A seal 14 for the grease chamber 13 seals an area between 
the above-mentioned hub disk 18 and the cover plate 12. 
A clutch housing 25 of a friction clutch of conventional construction is 
held at the second flywheel 20 by fastening means 24. The clutch housing 
25 holds a contact pressure spring 28 with retaining rings 27. The contact 
pressure spring 28 is acted upon during a clutch release (the clutch is 
constructed in a known manner and is therefore not shown) through spring 
tongues 29 which project radially inward. The radially outer region of the 
contact pressure spring 28 acts on a pressure plate 30. A clutch disk 33 
with friction facing 32 is disposed at the second flywheel 20. Pressure 
plate 30 is supported by friction facings 32 of the clutch disk 33. The 
clutch disk 33 includes a clutch disk hub 34 in its radially inner region 
having a rotary connection with a gear shaft, not shown, by means of a 
conventional toothing. 
The transmission element 1 on the drive side of the flywheel arrangement 
100 includes, on the crankshaft side, an added mass 40 fastened to the 
primary flange 4 by means of a weld seam 43. The added mass 40 engages the 
axial portion 10 of the primary flange 4 and is enclosed by a toothed rim 
42. The toothed rim 42 acts as retaining means 67 for the added mass 40 in 
a manner that will be described hereinafter. The added mass 40 is shown on 
the drive side in FIG. 1 only by way of example and can likewise be 
provided at the side which faces the second flywheel 20 as is shown, for 
example, in FIG. 7 of German Reference DE 43 39 421 A1. 
The added mass 40 will be discussed more fully as follows: FIG. 2 once 
again shows, in an enlarged view, the added mass 40 fastened to the 
primary flange 4 of the drive-side transmission element 1 by weld seam 43. 
Referring now to FIG. 3, the connection is produced with a plurality of 
pins 44 formed at the crankshaft side of the primary flange 4 considered 
in the circumferential direction, wherein the pins 44 engage openings 45 
in the added mass 40. The openings 45 are formed in such a way that they 
have a smaller diameter adjacent to the primary flange 4 compared with the 
crankshaft side. As soon as the added mass 40 is placed on the primary 
flange 4, a secure connection is achieved by compressing the pins 44 to 
form heads on the pins 44. 
A similar connection is shown in FIG. 4, wherein the pins 44 shown in FIG. 
3 are replaced by rivets 47. However, in view of the fact that the primary 
flange 4 adjoins the grease chamber 13, the solution according to FIG. 3 
is preferred for the sake of better sealing, since in FIG. 3, the primary 
flange 4 is formed without interruptions or breaks on the grease chamber 
side. 
Referring now to FIGS. 5 to 7, the added mass 40 is constructed as a ring 
52 with an angular cross section, wherein the ring 52 has an axial region 
54 and a radial region 56. FIG. 5 shows notches 58 in the axial region 54 
of the ring 52, while FIG. 6 shows recesses 59 in this axial region. The 
recesses 59 and the notches 58 thus form open locations 74 in the axial 
region 54 which can be used, for example, as signal transmitters in 
conjunction with a motor control. Such open locations 74 may be used, for 
example, as ignition markings. Additional open locations 74 are shown in 
FIG. 7, in which cut out portions 57 are shown in the radial region 56 of 
the ring 52. These cut out portions 57 may be required, for example, to 
allow the insertion of tools in the event that such access is necessary at 
the location in question for repairs or adjustments of the flywheel 
arrangement 100. 
The present added mass 40 is produced in a particularly advantageous manner 
according to the invention. For this purpose, as can be seen particularly 
from FIGS. 8 and 9, a flat strip material is cut to a length that is 
selected such that when this strip material is worked into a circular 
shape, the resulting ring 52 has the required diameter for embracing the 
axial portion 10 of the primary flange 4. The shaping is preferably 
effected in this case by rolling. 
With respect to the strip material which is cut to the correct size, a 
blank 60 is formed which can subsequently be provided with cut out 
portions 57, notches 58 and/or recesses 59, if needed, preferably by means 
of at least one punching process. Independent from the production of these 
open locations 74, interruptions 48 are provided proceeding from one side 
70 of the blank 60 and extending toward the other side 72 of the blank 60, 
but are not continued all the way to the other side 72. As a result, 
tongues 50 are formed between every two interruptions 48. 
The blank 60 formed in this way is subsequently shaped in the manner 
described above to form a ring 52, wherein this ring initially has only 
one axial region. The tongues 50 are then bent, wherein the bending region 
is preferably situated in the end region of the interruptions 48. Because 
of the small width by which the tongues 50 extend in the circumferential 
direction, this bending is accomplished, in contrast to a closed ring, 
with relatively little force and without substantial displacement of 
material, so that this area of the ring 52 remains virtually free of 
stresses. 
There are different possible procedures for maintaining the annular shape 
of the ring 52 deformed in this way. In the solution shown in FIG. 1, the 
blank 60 is so dimensioned prior to working into the annular shape that a 
relatively large intermediate gap 65 (FIGS. 5 to 7) remains in the ring 52 
between the two ends 62 and 63. The ring 52 is then pressed together until 
the intermediate gap 65 is eliminated and the two ends 62 and 63 therefore 
contact one another. Subsequently, a rim 42, for example, a toothed rim 
according to FIG. 1, is placed on the ring 52 that is pretensioned in this 
way. When the ring 52 is relaxed, the radial outer side of its axial 
region 54 contacts the inner circumference of the toothed rim 42 so that 
the toothed rim 42 acts as retaining means 67 for the ring 52. The toothed 
rim 42 is preferably dimensioned in such a way that the ring 52 is held 
under radial pretensioning. Of course, other methods are also conceivable, 
for example, that of shrinking on the toothed rim 42. In order to do 
without compression of the ring 52 for placing on the toothed rim 42, the 
two ends 62, 63 can also be temporarily held together by spot welds. 
If a rim 42 is not used as retaining means 67, it is also conceivable to 
permanently connect the two ends 62, 63 by means of a weld seam 68. In 
this case, the weld seam 68 acts as retaining means 67. 
According to FIG. 10, the ends 62, 63 of the ring 52 are arranged in the 
region of die notch 58. This is advantageous for preventing erroneous 
signal detection. The ends 62, 63 could also extend within the area of 
another open location 74, for example, a cut out portion 57 or a recess 
59. 
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.