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Патент USA US2115657

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April 26, 1938-
Filed April 9, 1936
2 Sheets-Sheet l
April 26, 1938.
Filed April 9‘, 1936
2 Sheets-Sheet 2
Patented ‘Apr. ‘26', 1933
TERNAL oormus'rlon
Herbert Jose! Venediger, Chemnitz. Germany, 88''
to Auto
Aktiengeselischatt. .
Chemnitz, Germany
Application April 9, 1936, Serial No. ‘73,561
In Germany April 9, 1935
5 Claims.
This invention relates to a two-stroke internal
combustion engine with port scavenging, in which
the scavenging and inlet-ports are arranged on
both sides oi‘the outlet ports ‘placed side by side
5 and lie at about the same height.
ing the cylinder expands laterally there will still 5
Even it actually the scavenging stream'enter- _
be considerable partsv of the cylinder unscav
enged, as shown in Figs. 1-3, where the unscav-Q
enged zones adjoining the cylinder wall (11 are in
dicated with horizontal hatching, and the zones
enclosed by the scavenging streams and also re- 10
ious scavenging passages conduct the scavenging
air against the cylinder wall lying opposite the‘
outlet passages.
1-3 in broken lines.
Engines with outlet and scavenging ports in
such position are known. In the known engines
however, the arrangement is such that the var
m. The breadth of the scavenging streams due
to the breadth-oi the passages are shown in Figs.
.maining unscaveng'ed, are‘ indicated byvcross- _
These engines have a number of disadvantages.‘ ; hatching. The horizontally hatched zone indi
In the case of mixture compressing engines they cated by 3 is greatest in Fig. 1; in Fig. 2 there
have high fuel consumption, unsatisfactory run _ are two such zones, but in Fig. 3 the zone 3 is very
ning with throttle control, non-uniform heating small and in view of the lateral expansion of the 15
scavenging stream, is negligible.
of the cylinder and piston parts and the like,
' .
Figs. 2: and 3 show a cross-hatched residual
' vIn .the accompanying drawings Figs. 1-4 show .' gas zone 4, which is absentin Fig. 1, but is great.
a two-stroke internal combustion engine of a . est in Fig. 3. In order to understand this zone
4 reference is made to Fig. 4 showing the arrange-3 2o
20 possible (Fig. 1) or of a hitherto known (Figs.
as a result of inadequate scavenging.
2-4) construction. Figs. 1-3 are cross-sections ment of the scavenging passages S1, S2 according
to Fig. 2.; The longitudinal‘section (Fig; 4) is‘so
through the zones of the control passages ar
ranged at the same dead centrepolnt, and Fig. 4‘ taken that it passes through the outlet passage _
is a longitudinal section of the cylinder. Figs. 5 ' A1, The scavenging stream entering through
to ‘l ‘are cross sections through a cylinderaccorda the scavenging passage S1 is indicated by l’ as 25
ing to the invention, the section being taken' at long as it is moving upwards towards the cylin
the height of the exhaust and scavenging ports, der head and with I’.’ when it?ows downwards
again to the piston b. The same applies for the
~ and these ?gures include a plan view of the pis
ton head and diagrammatic illustrations of the‘ scavenging stream 2.‘ Between the upwardly and
downwardly ?owing scavenging streams 1', 2'- 30
30 paths of‘ scavenging. Figure 8=is a longitudinal
section of the cylinder shown in Figures 5' to '7. a and l", .2" lies the residual gas zone 4,. Above
, Figure 9 is ‘a cross section through a cylinder in the piston b and near the rear cylinder wall or
there isformed a further piston end zone 5, not
which the scavenging ports have a di?erent po
sitionaseompared with the scavenging ports of
hitherto mentioned. This is greater the more‘35
5 to '_7. Figure 10 is a partial section‘ steeply are the scavenging passages inclined.
The above explanation makes the principal
through the cylinder with side elevation of the
piston.’ Figure 11 is a longitudinal section disadvantages of this known scavenging oper
through a cylinder with additional scavenging ation clear. At the same time the ‘known uniform '
35 _-Figures
portsjin. the rear cylinder wall. Figure 12 is a , heating of the piston and cylinder wall is made ,
cross section through the cylinder shown-in Fig-‘
ure 11_ at the height of the. exhaust and scaveng
ing ports. Figures 13 to 15 are crossfsectional
views similar to Figure 11, in which the addi
tional scavenging ports' are designed di?'erently.
clear. The more acute is the angle p enclosed ‘10
by the scavenging streams l, 2, the smaller is the
central loss oi.’ scavenging duet“ - direct escape
into the outlet passages (short circuit), but the .
greater ‘the residual gas zone I, see Figs. l-iiyso'
’- Two outlet passages A1, A: .and two scavenging _ that in general when the zone 3 decreases the zone 45
passages ‘S1, Sz-are assumed ‘by way ‘of example. . 4 increases, and vice versa. The zone 5 is greater
the greater is the angle between the scavenging
Fig. 1 shows a possible arrangement of the scav
‘enging passages S1, S2, which is so chosen'that passages and the horizontal‘plane.
.The hitherto known engines with. the above
the scavenging jets l, 2 flowing through ‘the scav- ,
enging passages meet at about thecentre of the{ identi?ed port arrangement, that is accordingto 50
Figs.’ 2 and 3, use a ?at or slightly arched piston‘ I
In'Fig. 2, the jets I, 2 'meét, for example, ' head and‘leave the ‘guiding of-the scavenging
at the rear cylinder wall m, but in Fig.
ac: _ streams exclusively to the scavenging passage and» '
count of the greater inclination of the passages,
55 they meet on .the- other side of the cylinder wall -
the rear cylinder wall.
' '
The invention beginsirom the fact that in this 55
wayacomplete scavenging cannot be obtained and
that in fact no scavenging operation can dispense
with the guiding of the scavenging streams by the
piston or other suitable guiding devices. It also
goes a substantial step further and imposes the
requirement for which it also gives the solution,
thatthe directive actionon the scavenging streams
through the scavenging operation must be vari
able in such a manner that the scavenging opera
10 tion shown in Figs. 14 must be carried through
continuously as phases of the scavenging. The
scavenging streams l, 2 must therefore ?rst be so
together with the streams lb, 21) form the whole
scavenging stream l, 2. They therefore take ap~
proximately the direction shown in Figs. 6 and
8. When ?owing upwards towards the cylinder
head they remove for the most part the residual
gas zone 4 remaining from the ?rst stage of the
scavenging. The small amount of residual gas
1 then remaining is indicated by cross hatching
in Fig. 2.
Third stage, according to Figs. 7 and 8
The working piston is now in the lower dead
mutually directed for the purpose of avoiding the
centre position. A part of the scavenging medium
zones 3 that they would ?rst meet on the far side
16 of the rear cylinder wall m (Fig. 3), then a part
of the scavenging streams must ?ow in such a
manner as shown in Fig. 2 that the residual gas
flows as described in the ?rst stage; a further part
flows as in the second stage, while the remaining
part ?ows towards the centre of the cylinden
without any noticeable deflection by the guide‘
zone 4 is diminished, and ?nally further part
streams must be split 011 in such a manner that
they meet approximately in the centre of the
cylinder, as shown in Fig. 1, so as to remove the
residual gas zone 4 entirely.
_ This is carried into eifect according to the con
structional example of the invention by the
scavenging passages according to the invention
being directed approximately towards the centre
of the cylinder and by the piston b having a sym
metrically shaped guiding device which con
tinually de?ects the scavenging streams l, 2 dur
30 ing the scavenging operation.
For this purpose the piston head is ?tted with
a disc-like plate which is substantially bell
shaped in outline and the height of which di
minishes in the direction of the outlet passages.
35 The boundary curves e1, e: of the outline are
preferably connected together by a rounded part
1‘, which is preferably approximately semi-cir
Figs. 5-7 each show cross-sections through the
cylinder passing through the outlet passages A1,
A: and the scavenging passages 81, S: with a plan
view of the piston. Fig. 8 shows a longitudinal
section through the cylinder and piston, with a
diagrammatic illustration of the scavenging op
eration according to the invention. This is di
vided, according to the invention, into the fol
device, forming part streams lo, 20, and then
?ows to the cylinder head. By this means the
small amount of exhaust gas remaining from the
second stage is completely driven out. I
When the piston b moves back (upward stroke)
the three stages are repeated in the reverse se
quence. The reversing of the sequence is very
important because by this means the scavenging
streams are guided towards the rear cylinder
wall and kept away from the outlet. Thus accord
ing to the invention satisfactory scavenging is
obtained, while the outflow losses are diminished.
The heights of the guiding device 0 of the piston
are made greater the greater is the angle which
the scavenging passages make with the horizontal
plane. The rear cylinder wall need not be con
tinuous as in the example. Further scavenging
and inlet ports may be provided there, which at
the best will open into the cylinder with a steep 35
upward inclination. Their streams will then
preferably extend in such a manner that they as
sist the part currents la and 2a and lb and 21).
According to the invention the shape and dis
tribution of mass of the guide device 0 is so chosen 40
that the centre of gravity thereof falls in the
axis of the cylinder. By this means a tilting of
the piston is avoided.
In order to obtain a piston as light as possible,
according to the invention, the parts b1 adjoin
lowing three principal stages:
ing the outlet ports are made plane and the
First stage, according to Figs. 5 and 8
The working of the piston b with guide device' 0
causes the scavenging passages 81, B2 to be opened
to such an extent that‘ scavenging medium (air,
fuel-air-mixture, combustible gases) can enter
into the cylinder according to its pressure. The
scavenging medium is de?ected without shock
against the rear cylinder wall a: by the guide
in Fig. 9 by' way of example, where the guide
device consists only of two intersected webs. In
this way a working piston can be obtained, the 50
weight and surface of which are scarcely greater
than those of a ?at piston without guide device;
also the combustion space of the engine can be
shaped as desired.
- Figs. 11-15 of the drawings show furthercon
device c_ in i such a manner that the middle
structional example of the engine according to
scavenging streams I, 2 would meet on the far
side of thec'rear cylinder wall. They then ?ow
along the rear cylinder wall upwardly to the cyl
inder head and from there in the direction to
wards the outlet
es A1, A2, as illustrated
the. invention in which the rear cylinder wall
a1 has further scavenging or inlet ports opening
in Fig. 8.
Second stage, according to Figs. 6 and 8
guide device a is made dove-tailed as shown
into it preferably with steep upward inclination,
the streams of which serve for improving the 60
cylinder'?lling or scavenging, preferably for set
ting up and assisting the streams coming from
the other scavenging passages. ‘In Fig. 12, which
is a cross-section of Fig. 11, there is provided
The working piston is now in front of the lower
in the rear cylinder wall 411 a single scavenging
dead centre position. Since the greatest height of -
Passage 8: with steep upward inclination,- the
stream from which combines with the part
streams la from the scavenging passages S1 and
S1. In Figs. 13 to 15 further preferred construc
the guiding device according to the invention is
preferably about as great as the greatest height
70 of the scavenging passages, a part of the scaveng~
ing medium now ?ows over the guiding device
at the points where the height of the guiding de—
vice is smaller than that of the scavenging ports.
These part streams lb, 2b are thus deflected to a
75 less extent than the part streams la, 2a, which
tional forms are illustrated in which the streams
coming from the scavenging passages S; and S4
and ?owing to the cylinderhead improve the
stability of the total stream.
The invention is suitable for two-stroke mix
ture engines and two-stroke Diesel engines, and
In a two-stroke internal combustion engine,
is used with advantage both.“ tor. crank case _ a 3.
wall having scavenging ports, a piston
engines and for engines with separate charging in cylinder‘
controlling the scavenging port,
pumps. In the figures the scavenging passages said cylinder having
ports, and said
are shown equally high. Instead of this they can scavenging ports being exhaust
arranged on both sides of
be constructed with diminishing heights, as the exhaust ports, a ‘guide device having bell
shown in Fig. 10.
According‘ to the invention
shaped plan on the head of said piston with
highest parts at the vertex of the bell and
the same extent as the height of the guide device‘ \\ the
0. In this way the scavenging streamsadapt diminishing in height towards the base of the 10
bell, \said base being adjacent the exhaust ports
the upper controlling edge should fall away to r
10 themselves very satisfactorily to the cylinder .when“ vthe piston is at the bottom of its stroke,
space to be scavenged.
the edge of the bell-shaped guide device at the
What I claim is:-7-
1. In a two-stroke internal combustion engine,
a cylinder wall having an outlet passage therein,
15 said wall having inlet passages symmetrically ar
ranged on each side of‘ said outlet passage and at
the same height, the axes of saidv inlet passages
meeting substantially in the axis of said cylin
der, a piston,'a disc-like guide device of bell
20 shaped outline in plan decreasing in height from
a point adjacent the inlet passages towards the
outlet passages and located on the head of said
periphery otlythe piston being at least as wide as
the part of the \inner cylinder wall occupied by
the exhaust ports and narrower than the part of 15
the inner cylinder wall occupied by the scaveng
ing ports.
, I
4. An internal combustion engine as set forth
in claim 3 in which the part of a cylinder wall
opposite the exhaust ports is provided with ad 20
ditional scavenging and inlet ports which, are
steeply inclined upwardly. ‘
An internal-combustion engine as claimed’
piston, the upper controlling edges of‘ the inlet ; in 5.claim
3; in which the greatest height‘of the
passages decreasing in the same degree as the guide device is substantially as great as the 25
height of the guide device carried on said piston. ‘ height of the scavenging ports.
2. An internal combustion engine as claimed
in claim 1 in which [the guide device extends up
HER-BERT JOSEF 'vnnnmann.
to the part of a cylinder wall opposite the outlet
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