Internal combustion engine

An internal combustion engine has a reciprocating piston moving in a cylinder. A crank shaft is mounted in the interior of the crankcase. A connecting rod connects the piston to the crankshaft. The crankcase has a venting device for pressure compensation of the interior of the crankcase. The venting device has a venting line having a channel extending in a rotary component of the engine.

BACKGROUND OF THE INVENTION 
The present invention relates to an internal combustion engine having a 
reciprocating piston which is connected by a connecting rod to a 
crankshaft for driving further rotary components of the motor. The 
crankshaft is supported in a crankcase that is provided with a venting 
device for pressure compensation in the interior of the crankcase, whereby 
the venting device has a venting line extending outwardly from the 
interior of the crankcase. 
In such internal combustion engines, especially four-stroke engines or 
engines of similar construction having a separate lubrication system, it 
must be ensured for proper functioning that over the course of time no 
impermissibly high pressure will be built in on the interior of the 
crankcase. It is thus known to provide the crankcase with a compensation 
system by which the excess pressure within the crankcase can be released 
to the atmosphere. However, since in the crankcase oil mist is present, it 
must be ensured that oil will not be dispensed uncontrollably into the 
atmosphere but is contained within the crankcase. Accordingly, complicated 
separating devices must be provided which, however, do not reliably ensure 
proper separation. 
It is therefore an object of the present invention to provide a crankcase 
venting device for internal combustion engines, especially four-stroke 
internal combustion engines, which ensures a high degree of separation 
(retention of oil) while at the same time ensures proper venting of the 
crankcase. 
SUMMARY OF THE INVENTION 
Since according to the present invention, the venting line is provided 
within a rotary component of the motor and this venting line provides the 
direct connection between the interior of the crankcase and a chamber, the 
flow-conducting channels are thus subjected to rotation. The resulting 
centrifugal forces can be used to separate oil and fuel vapors from the 
air. For the conventional operating rpm of the internal combustion engine, 
for example, a range of 2,000 to 15,000 rpm, a safe and reliable 
separation is ensured. 
The venting line is preferably a central bore in the rotary component or 
can be provided as an axial groove in the mantle surface of the shaft on 
which the rotary component is mounted. 
In both cases the inlet, provided within the interior of the crankcase and 
connected to the venting line, may be covered by an air-permeable material 
whereby the fine oil mist that is entrained in the venting air will be 
separated from the air flow within the material of the fabric, non-woven 
etc. in the form of small droplets and is then mechanically precipitated 
by centrifugal forces resulting from the rotation of the component and 
returned into the crankcase. For increasing the separation effect, the 
venting line can have a widened portion, i.e., a portion having a larger 
diameter, which can be embodied as a cone. Expediently, within the cone a 
rebound plate or a truncated cone structure, widening in the direction of 
the venting line, may be positioned, both having an edge which, together 
with the inner wall of the cone, provides a narrow annular gap. Within the 
narrow annular gap the air-permeable material may be positioned, which is 
preferably a textile or metal fabric, so that the air exiting the interior 
of the crankcase will pass through the fabric and the entrained oil 
droplets will then be retained within the fabric, whereby small droplets 
will convert into bigger ones in the air-permeable material and separated 
by centrifugal force caused by rotation. The oil droplets flow along the 
wall of the inlet portion or the cone back into the interior of the 
crankcase. The oil precipitated in the air-permeable material positioned 
at the inlet is thus constantly removed so that the fabric cannot become 
plugged.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will now be described in detail with the aid of 
several specific embodiments utilizing FIG. 1 through 14. 
The crankcase 2 represented in FIG. 1 is a component of known internal 
combustion engine 1 with a piston 3 that reciprocates within a cylinder 
3a. The piston 3 is connected by a connecting rod 4 to a crankshaft 5 that 
is driven in rotation by the piston 3. The connecting rod 4 is secured 
with a connecting rod bearing 6 on the crank bolt 7 which is secured 
eccentrically to the longitudinal axis 8 of the crankshaft 5 between two 
crank arms 9. The crankshaft 5 is secured at its ends 10 in crankshaft 
bearings 11 which are inserted into bearing housings 12 of the crankcase 
2. The crankcase bearings 11 in the shown embodiment are roller bearings. 
In FIGS. 1 and 3, only one end 10 of the crankshaft 5 supported in the 
crankshaft bearing 11 is represented. 
For pressure compensation within the crankcase 2, a crankcase venting 
device 13 is provided which has a venting line 15 extending from the 
interior 14 of the crankcase 2 to the exterior of the engine. The venting 
line 15 is provided in the form of a channel 16, 17 in a rotary component 
of the engine, in the shown embodiment in the crankshaft 5, whereby the 
channel 16, 17 provides a connection between the interior 14 of the 
crankcase 2 and a chamber 18 which is vented into the atmosphere, 
preferably into the air intake system of the combustion engine 1. 
The chamber 18 is expediently formed between the crankshaft bearing 11 and 
an outer crankshaft seal 19 whereby the crankshaft bearing 11 delimits the 
chamber 18 relative to the crankcase interior 14 and the crankshaft seal 
19 provides an oil and gas tight sealing action in the outward direction. 
The chamber 18 is penetrated by the crankshaft 5 and is thus in the form 
of an annular chamber. In order to provide a sealing action between the 
chamber 18 and the crankcase interior 14, the crankshaft bearing 11 is 
embodied as a sealed bearing. It may be expedient to provide between the 
crankshaft bearing 11 and the chamber 18 a further crankshaft seal 20, as 
is shown in FIG. 2. 
The chamber 18 is connected with an outwardly extending line 21 which opens 
into the intake manifold of the engine or into the atmosphere at a 
suitable location. 
In the embodiment according to FIG. 1, the channel of the venting line 15 
is preferably embodied as a central bore in the crankshaft 5, i.e., in the 
inner portion of the end 10 facing the interior 14 of the crankcase 2. As 
shown in FIG. 1, at the end face 28 of the crank arm 9 facing the 
connecting rod 4, a widened inlet portion in the form of a cone 22 is 
provided which is positioned radial-symmetrically to the longitudinal 
center axis of the crankshaft 5 and whose tapered end 23 is connected to 
the venting line 15. The central bore 16 extends to a radial transverse 
bore 25 which provides communication between the central channel or bore 
16 and the chamber 18. The transverse bore 25, can be embodied as a blind 
bore, as is shown, or as a through bore. The central bore 16 is provided 
as a blind bore beginning at cone 22. 
A rebound plate 26 is arranged within the cone 22 and extends 
perpendicularly to the inlet 24 at a spacing to the inlet opening. The 
rebound plate 26 is positioned radial-symmetrically to the longitudinal 
axis 8 of the crankshaft 5 and delimits with its outer edge 29 an annular 
gap 30 which is defined by the wall of the cone 22 and the edge 29 of the 
rebound plate 26. The rebound plate 26 is connected by stays, preferably, 
a ring element 31, to the cone 22 whereby the ring element expediently is 
embodied of air-permeable material 32, especially a textile or metal 
fabric. It may be expedient to embody the rebound plate 26 also of an 
air-permeable material 32, i.e., a fabric. 
The embodiment according to FIG. 3 corresponds substantially to FIG. 1 so 
that identical parts are referenced with the same reference numerals. The 
venting line 15 is an axial groove 17 in the outer mantle of the 
crankshaft 5, whereby the axial groove 17 extends from the interior 14 of 
the crankcase 2 into the chamber 18. Between the crankshaft bearing 11 and 
the crank arm 9, a cone 33 consisting of sheet metal, plastic, or other 
stiff materials is arranged on the inner portion of the antenna of the 
crankshaft 5. The cone 33 widens in a direction toward the crank arm 9 and 
forms an outlet funnel similar to cone 22. The cone 33 embraces with its 
tapered end 23 the inner end of the axial groove 17 which provides the 
inlet for the venting line 15. The tapered end 23 sealingly connects to 
the inner ring 34 of the crankshaft bearing 11 so that pressure 
compensation will take place exclusively via the cone 33 (outlet funnel 
22). A truncated cone 35 is fastened within the outlet funnel 22 on the 
crankshaft 5 whereby the truncated cone 35 widens in the direction toward 
the tapered end 23 of the funnel structure 22. Between the edge 29 of the 
truncated cone 35 and the wall of the cone 33, an annular gap 30 is formed 
through which the crankcase gases can flow into the venting line 15, 
respectively, the axial groove 17 and from there into the chamber 18. In 
the embodiment according to FIG. 3, the opening of the venting line 15 can 
be covered by an air-permeable material 32, for example, a fine mesh 
textile or metal fabric, non-woven etc. whereby the material or fabric can 
be attached directly or indirectly to the crankshaft. This ensures that 
the material 32 or the fabric rotates with the crankshaft so that 
sufficient centrifugal forces will act on oil retained in the material for 
precipitation therefrom. The separation effect which is realized simply by 
providing a centrifugal force, is further improved by the fabric also 
being rotated so that venting of the air from the crankcase directly into 
the atmosphere is possible. 
In the embodiment according to FIG. 4, another rotating component, in 
particular, a gear wheel 36, is provided which is preferably a part of the 
valve drive of the four-stroke engine and this rotary component is used 
for embodying the venting device 13. The gear wheel 36 is fixedly attached 
to the shaft 37 which is arranged in the bearing 39 in the housing 40 of 
the internal combustion engine. The gear wheel 36 has a sleeve portion 38 
which embraces the shaft 37 and supports a sleeve 41 comprised of fabric, 
non-woven etc. The sleeve portion 38 has a radial bore 42 aligned with the 
transverse bore 25 and opening into the central blind bore 16 of the shaft 
37. The central bore 16 is a blind bore extending from the axial end face 
of the shaft 37 which is positioned in the bearing recess open to the 
atmosphere. The valve drive thus communicates directly with the interior 
14 of the crankcase. When high pressure is present, air can flow via the 
sleeve 41, the radial bore 42, the transverse bore 25, and the bore 16 to 
the atmosphere. The fine oil mist, which is entrained in the air, is 
retained in the fabric of the fabric sleeve 41 and will form larger oil 
droplets which are then radially removed by rotation of the sleeve 41 due 
to centrifugal forces. The sleeve 41 is fixedly attached to the sleeve 
portion 38 and rotates thus at the same rpm as the gear wheel 36. The gear 
wheel 36, in order to avoid a liquid oil slump on the sleeve 41, is of a 
cup-shaped design, as is shown in FIG. 4. Oil droplets which fly off the 
sleeve 41, will reach the cup wall, then flow along the cup wall and over 
the edge back into its crankcase 2. 
In the embodiment according to FIG. 5, a gear wheel 43 is shown which is 
driven in rotation by the crankshaft. The gear wheel 43 is mounted on a 
pin 44 secured in the housing. The gear wheel 43 rotates on the pin 44 
having a central bore 16 extending therethrough. It communicates at its 
ends with the axial transverse bores 25, 45. The transverse bore 25 facing 
the interior 14 of the crankcase is positioned axially upstream of the 
gear wheel 43 and is covered by a sleeve 41 which rotates on the pin and 
is fixedly secured to the gear wheel 43. At the other end of the central 
bore 16, the transverse bore 45 provides a connection to the chamber 18 
which is formed between the housing 40 and the gear wheel 43 by providing 
a corresponding shaft seal 20. The chamber 18 is connected by a line 21 to 
the atmosphere or the air intake system of the internal combustion engine. 
The end face of the gear wheel 43 facing away from the chamber 18 is 
advantageously provided with radial vanes 46 which accelerate the oil mist 
in the centrifugal direction. This further improves the oil separation 
from the air flow into the atmosphere and will make it possible to 
eliminate, depending on the resulting degree of separation, the 
arrangement of a fabric or non-woven sleeve 41. In the embodiment 
according to FIG. 5, for the purpose of increasing the separation effect, 
a sleeve 41 is provided adjacent to the separation surfaces along the path 
to the venting line so that an optimal high degree of separation of the 
entrained oil can be achieved which allows venting of the chamber 18 
directly into the atmosphere. 
In the embodiment according to FIG. 5, the sleeve 41 is radially supported 
by the vanes 46. Accordingly, even at high rpm the lifting of the sleeve 
41 from the pin 44 is prevented. 
In the embodiment according to FIG. 6, the venting line is in the form of a 
plurality of axial bores 16 in the vicinity of the center of the gear 
wheel 43. The inlets 24 of the bores 16 are covered by a cap 47 facing the 
interior 14 of the crankcase, whereby the cap 47 is fixedly connected to 
the gear wheel 43 and is comprised of an air-permeable material, fabric, 
sieve, fleece, etc. The gear wheel 43 has an extended bearing portion 48 
which projects past the inlets 24 in the axial direction and rests at the 
bottom of the cap 47. 
The embodiment according to FIG. 7 corresponds to the embodiment of FIG. 6. 
However, instead of the cap 47 a ring 49 is provided which is fixedly 
connected to the bearing portion 48 of the gear wheel 43 and is preferably 
inserted into the axial depression 50 of the gear wheel 43. The bores 16 
of the venting line 15 open into the depression 50 and are thus covered 
axially by the ring 49 comprised of filter fabric, filter fleece or a 
similar material. It may be expedient to arrange according to the 
embodiment of FIG. 5 on the end face of the gear wheel 43 facing the 
chamber 18 radial vanes 46 which support the filter ring 49 radially and 
function as mechanical precipitators where the oil mist will be 
precipitated and removed due to the rotation of the gear wheel 43. 
In the embodiment according to FIG. 8, the crankcase venting device is 
provided in a different component of the internal combustion engine in a 
separate venting component 51 which is driven by a corresponding drive 
device, in the embodiment a gear wheel pair, by the crankshaft of the 
internal combustion engine. In FIG. 9, the venting component 51 is shown 
in an enlarged representation. It is comprised substantially of a gear 
wheel 52 with an axial bearing portion 53 in the form of a short shaft 
that is positioned in a matching bearing 54 of the housing 40. The venting 
line 15 is a throughbore in the gear wheel 52 and the short shaft 53. The 
inlet 24 of the venting line 15 is covered by a filter fleece 55 which 
rotates together with the gear wheel 52. The venting line 15 opens into 
the chamber 18 which is positioned between the housing 40 and an 
expediently placed cap and is connected by a line 21 to the atmosphere. 
The advantage of a separate venting component 51 is that it can be designed 
freely according to constructive specifications for any suitable location 
within the internal combustion engine. 
The embodiment according to FIGS. 10 and 11 shows schematically a further 
design of a crankcase venting device in which a venting component 51 
rotates with a shaft, for example, the crankshaft 5. The transverse bore 
25 extending radially to the central bore 16 has a widened inlet portion 
60 having an inner wall 61 at which the oil mist entrained in the air flow 
will precipitate and will be removed by centrifugal force due to the 
rotation in the direction of arrow 62 to be returned into the crankcase. 
The air removed via the central bore 16 is thus substantially free of oil 
particles. 
In the embodiment according to FIGS. 12 and 13, the separation is realized 
by radial vanes 46 which are arranged radially to the inlet 24 into the 
venting line 15. The oil mist which is entrained in the air flow 56 into 
the inlet 24 of the venting line 15 is accelerated centrifugally by the 
vanes 46 and is radially returned into the crankcase. 
It should be noted that the separation effect is primarily the result of 
the centrifugal force acting on the liquid components of the oil mist, as 
is shown especially in FIGS. 10 through 13. The arrangement of an 
additional filter sieve, fabric etc. in front of the inlet 24 is therefore 
not a requirement. The arrangement of such a filter fleece, however, can 
improve the oil separation to an optimal level. 
In the embodiment according to FIG. 14, a crankshaft 5 has mounted thereon 
a venting component 51 which is comprised substantially of a disc 70 which 
has radial bores 71 distributed about the circumference 72 of the disc and 
opening into widened inlet sections 73. In the widened inlet section 73 
fabric inserts 74 are positioned which are secured by a collar 75 
embracing the disc and thereby radially securing the inserts 74. On the 
end face facing the crank arms 9, the disc 70 has inlet bores 76 by which 
the pressure compensation of the crankcase interior 14 is realized via the 
central venting lines 16. In the bores 16 a throttle 77 is arranged which 
reduces the bore cross-section to a size that is expedient for venting. It 
is thus ensured that at the inlet of the crankcase venting device minimal 
flow velocities are present in order to avoid entrainment of oil droplets 
into the venting channels. The oil entrained in the air entering the inlet 
bores 76 will be precipitated in the fabric inserts, fleece inserts etc. 
within the inlet section 73. Due to the centrifugal force, the oil is then 
returned via the removal bores 78 arranged in the disc 70 into the 
crankcase interior 14. The inlet sections 73 open into the bores 71 that 
have a reduced diameter and are congruent to the transverse bores 25 in 
the crankcase 5. They provide communication to the central removing bores 
16. In the flow direction toward the atmosphere, the throttle 77 is 
arranged in order to determine a suitable flow cross-section. It should be 
mentioned that with the basic construction according to FIG. 14 a 
sufficient separation can be achieved without use of fabric or fleece 
inserts. 
The specification incorporates by reference the disclosure of German 
priority document 198 24 041.4 of May 29, 1998. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.