Note: Descriptions are shown in the official language in which they were submitted.
~L31~3~
-- 1 --
The invention relates to a process ~or producing
crank-shafts and crank-journals, the crank-webs, produced
individually and subsequently joined together, being pro-
vided ~ith bores and the crank-journals being hollow. The
invention also relates to an assembled crank shaft con-
sisting of at least crank-webs and crank-journals with
joints therehetween produced by plastic deformation, for
which purpose the ends of the journals are inserted into
apertures in the crank-webs. Crank-shafts of this kind,
especially if they have several cranks, are used mainly in
internal combustion engines, the most severe and highly
stressed field of application for them. In addition to
this, crank-drives may be found in many other areas of
con~rol and energy conversion, frequently in the form of
crank~shafts with a single crank.
Crank-shafts for smaller piston-engines, especially
Otto and Diesel engines, are often cast in a mould or forged
in one piece in a die; the journals are then machined and
~hardened. Since these operations have to be carried out on
a workpiece having a plurality of cranks, they are rela-
tively costly. Crank-shafts for larger engines, on the
other hand, are assembled from individual parts such as
~3~31~77
-- 2
are availablP taking into account production-technical
facilities. Typical solutions are given in DE-B-16 25 579
where the joint between the two parts extends through the
webs, and in DE-B-20 23 364 whexe the journals are divided.
The individual parts are always connected by welding, even
in those cases where the crank-shaft is to be assembled
from pressed plate metal parts positioned side by side.
(DE-C-498 170). The person skilled in the art also knows
(DE-C-848 728) that in order to save weight, the crank-
shaft may be hollow and that journals and webs may be madeof different materials each of which is better suited for
accommodating the differsnt specific loads. From DE-A-19
22 488, an intermediate layer is known which serves to
imp~ove the adhesion between the individual parts connected
by electron beam welding. DE-A-19 51 097 shows that before
the individual parts are assembled, a finished driving
element (in this case a gear) may be slid on to one of
them (in this case a bearing-iournal) and then fixed. In
the same publication the person skilled in the art will
find the proposal to design the individual parts of the
joint in such a way that prior to welding they may be
inserted into each other to provide an assembly aid. US
patent 4,622,864 discloses a crank-shaft for internal
combustion engines which iæ buiIt up from individual crank-
webs and partly hollow journals, the parts being connectedtogether positively by thermal contraction.
For connecting the crank-shaft to the pistons it is
common to use divided connecting rods which are also
relatively expensive to produce and require special atten-
tion during assembly in order to ensure accurate concentricrunning of the journals, especially if the frequently used
friction bearings are replaced by roller bearings. The
method of fixing tubes in bores of other parts by expanding
the former is known from heat exchanger technology where
both mechanical and hydraulic expanding devices are used.
(DE-AS-26 16 523).
~3~313~7 7
-- 3 --
It is the object of the invention to provid2 a
cost-effective process for producing assembled crank-sha~ts
in the case of which the individual parts may be made of
materials which are particularly suitable for the different
specific loads to be expected. The individual parts will
be finish-machined prior to being joined so that apart
from straightening and precision alignment no subsequent
machining is required. The crank-shafts produced in
accordance with the invention will be provided with lubri-
cating channels which are easier to produce and also havegood emergency runningproperties. As the production
process is accompanied by the installation of driving
elements such as bearings and connecting rods, these will
at the same time be simplified and given improved running
properties.
It is furthermore the purpose of the present in-
vention to make available an assembled crank-shaft which
is satisfactorily adapted to the said production process
and possesses connections which are high in strength and
low in weight.
This purpose is accomplished in that the journals
are expanded ln ,situ by plastic deformation and are brought
to baar in corresponding bores in the crank-webs with a
permanent elastic prestress therein~ Because the webs
have been deformed elastically, they spring back on to the
journals after completion of the expansion process, as a
result of which a connection is produced which can even
withstand the high torques to be transmitted.
The expansion process requires the use of relatively
ductile materials for the journals. These may be subjected
to a conventional method of surface hardening, but a
process according to claim 2 seems more advantageous. It
is then possible to manufacture the bearing bushes of a
material which is optimized in respect of its bearing
properties, for example its hardness.
~ 31)387?7
-- 4 --
The journals are expanded in such a way that the
bearing-bushes are fixed in their position but undergo no
or only very slight elastic deformations.
If baaring-bushes are used, the journals are ex-
panded along their entire length and the bearing-bushes
are also deformed elastically. In this way a particularly
close connection between bearing-bushes and journals is
achieved.
In a further process ~mbodiment pressing the bearing
bushes into the web bores provided for this purpose pro~
duces a provisional connection which serves as an assembly
aid and which is replaced by the subsequent expansion of
the journal.
This type of process is less suitable for bearing-
bushes made of a relatively hard and brittle mat~rialbecause its surface tends to form cracks when expanded
elastically. In such a case it is advisable to apply the
variant according to which only those parts of the hearing-
bushes are expanded which project into the bores of the
webs and whose surface is thus not required as a bearing
face. This face could be excluded from the prscess of
hardening the bearing-bushes. By using bearing-bushes
provided with collars as proposed in claim 13, they are
provided with a stop when being introduced into the bores
and, furthermore, they are reinforced to such an extent
that the effects of the elastic deformation at the ends
cannot be passed on to the central part used as a bearing.
According to another configuration, undivided
roller-bearings may be fitted to the journals prior to
joining. Since the joining is carried out without heat
and no danger of metal being ejected from the weld, a
danger which cannot be completely eliminated when progres-
sive welding is used, this does not damage the bearings.
~303~
Furthermore, undivided connecting rods may be slid
onto the journals ~imultaneously with the roller-bearings
proposed hereinbefore. Since the crank-shafts produced
by the process accoxding to the invention are improved to
such an extent that the life thereof is no longer the
factor which limits the durability of machine as a whole,
easy repairability of the connecting rods and bearings may
be dispensed with.
In the case of friction bearings, the choice o~
sintered material for the bearing-bushes ensures a uniform
and easily quantifiable lubrication of the bearing faces.
In addition, according to claim 6, the sintered material
makes it possible to store certain quantities of a solid
lubricant which, i~ the actual oil supply to the bearings
fails, provides the bearings with certain emergenay running
properties.
In a further embodiment according to claim 8, a
sealinq layer may be provided between the journal and web
faces to be ~oined in order to seal the ends of the lubri-
cating channels preferably designed as continuous grooves.In a further embodiment of the process according to claim
9, a soft metal, for example copper, is used for the
sPaling layer.
A crank-shaft according to the invention is charact-
erized in that formed on the crank-journals are straight,
externally smooth tubular portions as connecting regions
which are inserted into straight, axially parallel or
equiaxial through-bores in the crank-webs and are secured,
by plastic expansion of the tubular portions, with per-
manent elastic prestress, in the through-apertures. Crank-
shafts of this kind, of simplified de~ign, may be produced
in such a manner that only the crank-webs are forgings or
stampings, whereas all other components may be made from
normal bar or tubular material. ~he hydraulic connection
is effected by methods known E~er se in that the connections
87~7
-- 6 --
of the tubular members are inserted into corresponding
through-bores in the crank-webs and are then expanded by
means of an inserted pressure-medium probe by radial
plastic deformation, the deformation of the crank-web in
the surrounding area remaining elastic and a prestress
being maintained between the parts, even a~ter removal of
the hydraulic pressure, the said prestress being capable
of transferring the necessary tor~ue. The bending moments
arising may be favourably supported in that ~ross-sectional
changes in the crank-journals are provided ad~acent the
connecting regions, whereby the end-surfaces may support
themselves on the crank-webs.
According to one satisfactory design, complete one-
piece cranks with a journal and two adjoining webs may be
produced in one piece, only the basic journal being in-
serted, as normal or rotating parts, into corresponding
apertures and being secured hydraulically. The advantage
of this is that the diameter of the connecting region to
be expanded may be made relatively large and that all
connecting locations are coaxial with each other. This
substantially simplifies the production process, since all
connections may be produced simultaneously by means of a
single continuous probe having a plurality of expanding
sections. The advantage o~ this is that various types of
crank-shaft, differing as regards the number and position
of the cranks, i.e. crank-shafts for a three- and four-
cylinder engine of the same series, may be produced with a
single-standard crank.
According to an advantageous embodiment of the
above, the basic journals are d~signed so as to be in one
piece, with steps in the outer diameter at the ends forming
the connecting regions.
According to a further embodiment, the basic jour-
nals may also be produced from a continuous tubular portion
and a slid-on sleeve with a larger diameter, with the
~.3~3~
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connection between the tubular member and the sleeve also
being effected by hydraulic expansion, just like the
connection between the connecting regions and the crank-
webs, the advantage here being that the use of standard
parts is taken further and the process o~ turning the end
regions is eliminated, and it is particularly advantageous
that the process of connecting the tubular portion and the
sleeve can take place simultaneously with the process of
connecting the connecting region with the crank-web,
requiring merely the use of pressure probes with longer
expanding portions.
An advantageous detail of the invention consists in
that in the end face of a bearing portion with the larger
diameter of the crank-journal, at the transition to the
connecting regions, undercuts are provided into which the
elastically deformed material of the crank-webs may enter
after deformation.
In a second basic embodiment of the invention, the
displacement and the crank-journals may be inserted into
the crank-webs in the way described and connected to these.
In a simple design permitting the use of standard parts,
the crank-journal consists o~ a smooth tubular portion.
To increase the bending strength and to achieve the re-
quired overlap of displacement journals and basic journal
in the case of short-stroke engines, the crank-journal
used may comprise a central portion with an increased
diameter arranged eccentrically relative to the connecting
regions, but this requires a considerable amount of machi-
ning.
For some applications it may be advantageous to use
crank-journals inserted exclusively into the crank-webs
and joined by hydraulic deformation if the said crank-webs
are in the form of discs, in order to act directly as
bearings in a manner know ~E_~, so that a simple turnPd
part may replace two crank-wsbs and one basic journal
13~31~7~7
-- 8 --
portion. This completes the transition to a disc-crank-
shaft, whereby disc-members, wikh crank-journals at op-
posite ~nds, act simultaneously as a bearing seat or
bearing surface ~or a roller- or friction-bearing.
It is of course particularly advantageous in respect
of being able to modify the entire design, if both the
crank-journals and the hasic journals are inserted into
the crank-webs, with the joints being produced in the way
referred to.
With shafts of the above-mentioned type, a par-
ticular problem consists in ensuring the supply of lubri-
cating oil from the basic bearing-journals to the connect-
iny rod bearing-journals, because as a rule at least one of
the journals is tubular. To solve this problem it is
proposed to inserk sleeves or journals with a smaller
diameter with sealed regions at their ends into the
through-bores of the bearing-journals, thereby producing
annular-cylindrical oil connecting spaces within the
iournals. To save weight, the inserted sleeves or journals
may be made of a light-weight material such as plastics or
light metal.
A preferred embodiment of the production process
consists in producing them in stages from one end to the
other, especially if the crank-journals are inserted and
joined as wellf because then free accessibility is ensured
from one end ~or introducing a straight pressure agent
probe. However, it is also possible to use pressure agent
probes whose expanding portions are arranged at an angle.
If only the basic journals are inserted, it is possible -
as already mentioned - to produce all connections in one
operation.
The crank-shaft as produced in accordance with the
invention provides one particular advantage in that un-
divided bearing-bushes and/or connecting rod eyes or pre-
~31~3~3~7
assembled connecting rods may be slid on to the displace-
ment journals prior to joining. Such connecting rods with
undivided eyes have considerable advantages in respect of
strength and weight. This process does not make the repair
of bearings impossible because the bearing-journals may be
pressed out axially and replaced with the. bearing-bushss,
and because of the purely elastic deformation of the crank
web material a subsequent connection with new bearing-
journals will not cause any prohlems.
Further details of the invention may be gathered
from the following description of the preferred examples
of embodiment illustrated in the drawing attached hereto,
wherein-
Fig. 1 shows a crank-shaft in accordance with the
invention with a short stroke in a ~irst configuration,
with a detail to an enlarged scale;
Fig. 2 shows a crank-shaft in accordance with the
invention with a short stroke in a second configuration
and a modified detail;
Fig. 3 shows a part of a crank-shaft }n accordance
with the invention with a long stroke in a first configura-
tion with an enlarged detail;
Fig. 4 shows a part of a crank-shaft in accordance
with the invention with a long stroke in a second con-
figuration.
Fig. 1 illustrates a crank-shaft l with two cranks
2, 3 arranged opposite each other, comprising two crank or
connecting rod bearing-journals 41~ 51 and thrae bearing-
journals 61, 71~ 81. The connection between the journals
is effected by crank-webs 91~ 10~ , 121. The basic
bearing journals form the bearing portions 50, 51, 52.
With a short crank-shaft of the type illustrated the basic-
journal 71 does not necessarily have to be designed as abearing area, and even with longer crank-shafts it is
possible to design only every second basic journal as a
~303a~7
-- 10 --
bearing area. Diameters can remain unchanged. In the
embodiment illustrated, two crank-webs gl, 101; 111, 12
are designed to be integral with the intermediate crank-
journal, and preferably they are produced in the form of a
forging. To save weight, the crank-journal 41 has been
provided with a through-bore 13 which also passes through
the crank-webs, whereas the crank-journal 51 has to be
solid. Each of the crank-webs comprises a coaxial through
aperture 14, 1~, 16, 17 into which the connecting portion~
18, 19, 20 and 21 are inserted. The basic journal 61
comprises only one connecting portion 18 and, for example
for being connected to a flywheel or a rotation damper, it
is arranged behind the bearing portion 50, whereas the
connecting journals 71 and 8l each comprise two connecting
portions 19, 20; 21, 22, with the latter for example
representing the connecting facility for a further crank-
web. The crank-webs 91 and 101 have been provided with
bolted-on counter weights 23, 24, whereas the crank-webs
111 andd 121 have been provided with counterweights 25, ~6
which are either cast on or forged on. The crank-journals
41~ 51 have each been provided with oil supply bores 27,
28 which extend at an angle, whose exit is at the friction
face of the bearing and which are in communication with
khe through-bore 29 in the central basic journal 71.
~rom this through-bore there runs a radial oil supply bore
30 whose exit is at the journal friction Eace 51. A sleeve
31 which has a smaller diameter and is sealed at its ends
is inserted into the through-bore 29 in order to form an
annular-cylindrical lubricant space 32. A journal 34
which has a smaller diameter and is sealed at its ends is
inserted into the through-bore 33 of the connecting rod
journal 41 in order to form an annular-cylindrical lubri-
cant space 35. The journal 34 and the sleeve 31 are
preferably made of a light material such as light metal or
plastics and they may be either pre~ed in or bra~ed in.
In the solid crank~journals 51' the oil supply bore 28
may continue as far as the bearing friction face. The
~ ~138~7
detail Z referes to an undercut 36 in the end face o~ the
bearing portion of the basic journal 71 at the transition
to the connecting region in order to avoid a notch effect
when expanding the connection re~ion.
Fig. 2 shows a further embodiment of the crank-
shaft l with two cranks 2, 3, with both the crank-journals
42' 52 and the basic journals 62, 72' 82 being connected
to the crank-webs 92' 12, 112, 122 by joining, with the
crank-webs having both through-bores 14, 15, 16, 17 for
10 receiving connecting portions 1~, l9, 20, 21, of the basic-
journals and through-bores 35, 37; 3~, 39 for receiving
connecting portions 40, 41; 42, 43 of the crank journals
42~ 52. The basic-journal 82 is completely identical to
the basic-journal 81 of Fig. 1 and also comprises a second
15 connecting portion 22, whereas the basic-journals 62~ 72
each consist of a continuous tubular piece 44, 45 and
slid-on sleeves 46, 47 which are connected to each other
by hydraulic expansion in particular.
In principle, the same design is also possible for
the crank-journals 42~ 52~ but in the Figures they are
shown as a smooth tubular portion 49 also comprising the
bearing region (crank-jouxnal 52) and an inwardly o~fset
eccentric 48 positioned between the connecting regions 40
and 4~ (crank-~ournal 4). In this case, too, the crank-
webs have been provided with bolted-on counter-weights 23,
24 and cast-on counter-weights 25, 26. Bores and channel
systems for the supply of lubricating oil have not been
illustrated in this case.
The modified detail refers to a basic journal 83
which is solid and in the case of which only the connecting
regions 21, 22 have been provided with blind holes 53, 54.
According to Figs. 3 and 4, the crank-shaft consists
of a series of webs which are optimized as to design and
material in such a manner as to achieve the most effective
weight:flexural rigidity ratio. Webs lOl are provided
~.3~3~77
- 12 -
with bores 109, 110 into which are inserted, with little
play, bearing-journals 102 made of a particularly ductile
material. They are then expanded with the aid of a probe
103 shown partly broken away. The said probe is supplied
with pressure-fluid through a duct 131, the said fluid
emerging into expansion-areas defined by seals 132 and
thus deforming the said bearing-journals plastically. The
adjacent parts of webs 101, however, are deformed only
elastically. Before the joint is made, bearing-bushes
104, made of a material which is pa~ticularly suitable for
this purpose, e.g. a hardened material, are fitted to
bearing-journals 102. Bearing-bushes 104 may be made of a
porous sintered material which may be impregnated with a
solid lubricant. In any case, an adequate supply of
lubricant passes through bores 111 to webs 101 which can
be fitted without difficulty prior to assembly, and through
lubricating ducts 121 to bearing-journals 102 which, in
this case, may be in the form of mil~ed grooves, for the
sake of simplicity. Also before the joint is made, un-
divided connecting rods 105 may be slid onto bearing-
journals 102. The bearings facilitating movement between
the two parts may be friction-bearings 106 or roller-
bearing 107, both being fitted to bearing-journals 102
be~ore webs 101 are joined thereto. As an aid to assembly
prior to expansion, the possibly thinner ends of bearing-
bushes 104 may be inserted into the bores in webs 101 in
press-fit. In order to ensure that the elastic deformation
of bearing-bushes 104, obtained by expanding the journals,
remains restricted to tapered portion 142, reinforcements
in the form of shoulders 141 may be provided. A sealing
layer 10~, e.g. one made of copper, rubber or plastic, may
be placed between webs 101 and journals 102, ~or the
purpose of sealing this joing from lubricating ducts 111,
121.
~L3~3~
- 13 -
List of ~L~ y~ L
1 Crank-shaft
2, 3 crank
4, 5 crank, displacement,
connecting rod, bearing-
journal
6, 7, 8 kasic journal, main
bearing-journal
9, 10~ 11, 12 crank-web
10 13 under-cut, through-bore
(crank-journal)
14, 15, 16, 17 through-bore,
(basic journal)
18, l9, 20, 21, 22 connecting portion
(basic journal)
23, 24, 25, 26 counter-weight
27, 28 oil supply bore
29 through-bore
(basic jo-lrnal)
20 30 oil supply bore
31 sleeve member
32 lubricant space
33 through-bore
(crank-journal)
25 34 journal member
lubricant space
36, 37, 38, 3~ through-bore
(crank-web)
40, 41, 42, 43 connecting portion
(crank-journal)
44, 45 tubular member
~basic journal)
46, 47 sleeve member
(basic 3ournal)
35 48 eccentric
49 tubular portion
50, 51, 52 bearing portion
53, 54 blind hole
101 crank-web
40 102 tubular member
(basic journal)
9 303~7~
103 pressure medium probe
104 bearing sleeve
(basic journal)
105 connecting rod
5 106 friction-:bearing
107 roller-bearing
108 seal
109 bore (crank-web)
110 bore (crank~web)
10 111 lubricating-oil bore
112 tubular member
(crank-journal)
114 bearing sleeve
(crank~journal)
15 131 pressure-medium duct
132 seal
141 shoulder (bearing sleeve)
142 recess
