U.S. patent application number 09/795390 was filed with the patent office on 2001-09-06 for two-stroke engine.
Invention is credited to Berqmann, Lars, Klimmek, Axel, Linsbauer, Peter, Rosskamp, Heiko.
Application Number | 20010018899 09/795390 |
Document ID | / |
Family ID | 7632985 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010018899 |
Kind Code |
A1 |
Rosskamp, Heiko ; et
al. |
September 6, 2001 |
Two-stroke engine
Abstract
The invention relates to a two-stroke engine in a portable
handheld work apparatus such as a motor-driven chain saw or the
like. A combustion chamber (3) is formed in the cylinder (2) of the
two-stroke engine (1). The combustion chamber (3) is delimited by
the piston (5). The piston (5) drives the crankshaft (7) via a
connecting rod (6) and the crankshaft (7) is rotatably journalled
in the crankcase (4). The two-stroke engine includes several
transfer channels (14), which, referred to a symmetry plane (49),
lie on opposite-lying sides (47, 48) with the plane partitioning
approximately the outlet (10). The transfer channels (14) connect
the crankcase (4) with the combustion chamber (3). A first end (20)
of each transfer channel (14) opens via an entry window (12, 15)
into the combustion chamber (3); whereas, the second end (19) of
each transfer channel opens to the crankcase (4). Each transfer
channel (14) is connected, between its ends (19, 20) to an air
channel (22a, 22b) via a membrane valve (21). Air is supplied by
the air channel (22a, 22b) via an adjustable throttle (31, 32). In
order to be able to adapt the stratified charge principle of the
engine to an occurring operating point, each transfer channel (14)
on one side (47, 48) is connected to a gas supplying air channel
(22a, 22b) and to configure the air channels (22a, 22b) separately
from each other such that the volumes of the fluid flows (40, 41)
can be adjusted differently from each other. The gas flows (40, 41)
are supplied via the air channels (22a, 22b).
Inventors: |
Rosskamp, Heiko; (Adelberg,
DE) ; Klimmek, Axel; (Schwaikheim, DE) ;
Linsbauer, Peter; (Remshalden, DE) ; Berqmann,
Lars; (Welzheim, DE) |
Correspondence
Address: |
Walter Ottesen
P.O. Box 4026
Gaithersburg
MD
20885-4026
US
|
Family ID: |
7632985 |
Appl. No.: |
09/795390 |
Filed: |
March 1, 2001 |
Current U.S.
Class: |
123/73A ;
123/73B; 123/73PP |
Current CPC
Class: |
Y02T 10/12 20130101;
F02B 2075/025 20130101; F02B 33/446 20130101; F02B 33/04 20130101;
Y02T 10/146 20130101; F02B 25/22 20130101; F02B 33/44 20130101;
F02M 23/03 20130101; F02B 63/02 20130101 |
Class at
Publication: |
123/73.00A ;
123/73.0PP; 123/73.00B |
International
Class: |
F02B 033/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2000 |
DE |
100 09 793.6 |
Claims
What is claimed is:
1. A two-stroke engine including a two-stroke engine in a portable
handheld work apparatus, the two-stroke engine comprising: a
cylinder having a cylinder wall; a piston mounted in said cylinder
to undergo a reciprocating movement along a stroke path between top
dead center and bottom dead center during operation of said engine;
said cylinder and said piston conjointly delimiting a combustion
chamber; a crankcase connected to said cylinder; a crankshaft
rotatably mounted in said crankcase; a connecting rod connecting
said piston to said crankshaft to permit said piston to drive said
crankshaft as said piston reciprocates in said cylinder; a
mixture-preparation device for supplying an air/fuel mixture; an
intake channel for conducting said air/fuel mixture into said
crankcase; said cylinder having a discharge opening formed therein;
a plurality of transfer channels connecting said crankcase to said
combustion chamber; a first portion of said transfer channels being
disposed on one side of a symmetry plane extending through said
cylinder so as to partition said discharge outlet; a second portion
of said transfer channels disposed on the other side of said
symmetry plane; each of said transfer channels having a first end
defining an entry window opening into said combustion chamber; said
entry window being formed in said cylinder wall and being
controlled by said piston as said piston moves in said cylinder;
each of said transfer channels having a second end opening into
said crankcase; a first plurality of air channels connected to
corresponding ones of said first portion of transfer channels; a
second plurality of air channels connected to corresponding ones of
said second portion of said transfer channels; gas supply means for
supplying a gas flow to each of said air channels; said first
plurality of air channels being configured separately from each
other so that the volumes of the gas flows thereto can be adjusted
differently; said second plurality of air channels being configured
separately from each other so that the volumes of the gas flows
thereto can be adjusted differently; a check valve for connecting
each of said air channels to the transfer channel corresponding
thereto at a location between said first and second ends thereof so
as to permit the gas flow to flow from said air channel into the
transfer channel; and, a throttle device connected to said air
channels for effecting the different adjustment of the volumes of
the gas flows in the separately configured air channels.
2. The two-stroke engine of claim 1, wherein said throttle device
includes an adjustable throttle for each of said air channels.
3. The two-stroke engine of claim 1, a transfer channel of said
first portion and a transfer channel of said second portion lie at
approximately the same elevation and conjointly defining a transfer
channel pair; and, said throttle device includes a common
adjustable throttle connected to the air channel of said first
plurality and the air channel of said second plurality connected to
the corresponding ones of said transfer channels of said pair.
4. The two-stroke engine of claim 1, said throttle device including
throttle elements for said air channels and said throttle elements
being mounted for pivotal movement about a rotational axis.
5. The two-stroke engine of claim 4, wherein said throttle elements
are throttle flaps.
6. The two-stroke engine of claim 4, wherein said
mixture-preparation device includes a throttle flap; and, coupling
means for position-dependently coupling said throttle elements to
said throttle flap.
7. The two-stroke engine of claim 6, wherein said throttle elements
are throttle flaps; and, said coupling means including levers
attached to corresponding ones of said throttle flaps and actuating
arms interconnecting said levers.
8. The two-stroke engine of claim 7, wherein said actuating arms
are adjustable in length and translation ratios and/or lost motion
are adjustable.
9. The two-stroke engine of claim 1, wherein said air channels are
defined by at least one of the following: external pipes, tubing,
components defining said air channels and cavities in the cylinder
block.
10. The two-stroke engine of claim 1, further comprising an air
filter mounted upstream of said mixture-preparation device; said
air filter having an air filter housing having a base; said
throttle device including a throttle housing connected to said base
and said air channels being connected to said throttle housing;
and, said throttle device including throttle elements mounted in
said throttle housing for adjusting the gas flows to said air
channels.
11. The two-stroke engine of claim 10, wherein said
mixture-preparation device is a carburetor having a carburetor
housing separate from said throttle housing and said carburetor
housing is at a predetermined spacing from said throttle housing;
and, said air channels are connected to said throttle housing
separated one from the other.
12. The two-stroke engine of claim 11, wherein said throttle device
includes a first throttle unit for a selected number of said air
channels and a second throttle unit for the remainder of said air
channels; said first throttle unit is connected to said air filter
housing and said second throttle unit is connected to said first
throttle unit; and, said throttle units are accommodated in said
throttle housing.
13. The two-stroke engine of claim 12, wherein said throttle
housing is formed as one piece with said air filter base.
14. The two-stroke engine of claim 10, wherein said air filter
housing defines a clean space and includes a partition wall
partitioning said clean space into two chambers separated from each
other; said mixture-preparation device is connected to one of said
chambers and said throttle device is connected to the other one of
said chambers.
15. The two-stroke engine of claim 12, further comprising
electrical positioning device adjusting said first and second
throttle units independently of each other.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a two-stroke engine as used,
especially, as a drive engine in a portable handheld work apparatus
such as a motor-driven chain saw, brushcutter, cutoff machine,
blower apparatus or the like.
BACKGROUND OF THE INVENTION
[0002] Mixture-scavenged two-stroke engines are used especially in
portable handheld work apparatus because of the low weight and high
power realization. In order to improve the exhaust-gas performance
of mixture-scavenged two-stroke engines, German patent publication
2,650,834 discloses, in the context of a four-stroke engine,
supplying essentially fuel-free gas (preferably air) via the
transfer channels disposed close to the outlet and to introduce a
rich mixture via the transfer channels which are remote from the
outlet. Here air is already present ahead of the rich mixture in
the transfer channels remote from the outlet. In this way, the
mixture scavenging losses are intended to be reduced and therefore
the exhaust-gas quality improved.
[0003] Supplied fuel-free gas, especially air, is not advantageous
in all operating states for reducing scavenging losses. Thus, in
the case of idle, an adequately rich ignition-ready mixture has to
be provided in the combustion chamber; whereas, in high rpm ranges,
a slightly lean mixture is advantageous. Furthermore, there is only
a narrow window of time available for introducing the mixture at
high engine speed which, in the case of advanced air, is further
limited. In German patent publication 2,650,834, a throttle flap is
suggested in the gas supplying air channel to adjust the quantity
of the advanced air in the transfer channel remote from the
outlet.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to improve a two-stroke
engine to achieve a complete introduction of mixture at reduced
scavenging losses independently of the charging principle at every
operating point of the engine.
[0005] The two-stroke engine of the invention includes a two-stroke
engine in a portable handheld work apparatus. The two-stroke engine
includes: a cylinder having a cylinder wall; a piston mounted in
the cylinder to undergo a reciprocating movement along a stroke
path between top dead center and bottom dead center during
operation of the engine; the cylinder and the piston conjointly
delimiting a combustion chamber; a crankcase connected to the
cylinder; a crankshaft rotatably mounted in the crankcase; a
connecting rod connecting the piston to the crankshaft to permit
the piston to drive the crankshaft as the piston reciprocates in
the cylinder; a mixture-preparation device for supplying an
air/fuel mixture; an intake channel for conducting the air/fuel
mixture into the crankcase; the cylinder having a discharge opening
formed therein; a plurality of transfer channels connecting the
crankcase to the combustion chamber; a first portion of the
transfer channels being disposed on one side of a symmetry plane
extending through the cylinder so as to partition the discharge
outlet; a second portion of the transfer channels disposed on the
other side of the symmetry plane; each of the transfer channels
having a first end defining an entry window opening into the
combustion chamber; the entry window being formed in the cylinder
wall and being controlled by the piston as the piston moves in the
cylinder; each of the transfer channels having a second end opening
into the crankcase; a first plurality of air channels connected to
corresponding ones of the first portion of transfer channels; a
second plurality of air channels connected to corresponding ones of
the second portion of the transfer channels; gas supply means for
supplying a gas flow to each of the air channels; the first
plurality of air channels being configured separately from each
other so that the volumes of the gas flows thereto can be adjusted
differently; the second plurality of air channels being configured
separately from each other so that the volumes of the gas flows
thereto can be adjusted differently; a check valve for connecting
each of the air channels to the transfer channel corresponding
thereto at a location between the first and second ends thereof so
as to permit the gas flow to flow from the air channel into the
transfer channel; and, a throttle device connected to the air
channels for effecting the different adjustment of the volumes of
the gas flows in the separately configured air channels.
[0006] Each transfer channel on a side of the symmetry plane is
connected to a gas supplying air channel. The gas supplying
channels are configured so that they are substantially separate
from each other. In this way, it is possible to adjust the volumes
of the gas flows in the air channels independently of each other so
that the quantity and the distribution of the air, which is
introduced ahead of the air/fuel mixture to reduce the mixture
scavenging losses, can be metered so as to be adapted to the
operating state of the engine.
[0007] For a two-stroke engine having (n) transfer channels
(n.gtoreq.3), this makes possible the metering of the bypass air
for reducing the mixture scavenging losses with this metering of
the bypass air being adapted to an operating point of the engine.
In this connection, the engine can be operated over a wide range in
accordance with the stratified charge principle as well as in
accordance with the principle of advanced air in the transfer
channels close to the outlet as well as in the transfer channels
remote from the outlet with an appropriate control of the
gas-supplying air channels.
[0008] In the principle of advanced air, a volume of air is
advanced into the transfer channel ahead of the air/fuel mixture
thereby facilitating scavenging of the combustion chamber in
advance of the next combustion. This reduces the amount of
uncombusted fuel discharged to the atmosphere. More specifically,
little of the air/fuel mixture which follows the advanced air is
discharged because the discharge outlet is already almost closed or
closed by the time that the air/fuel mixture reaches the combustion
chamber behind the scavenging volume of air.
[0009] Advantageously, each air channel is assigned a preferably
adjustable throttle. To reduce the need of components, a common
adjustable throttle is assigned to the transfer pair of the
overflow channels which lie approximately at the same elevation and
are on opposite-lying sides of a plane of symmetry of the cylinder.
The throttle is configured like an air throttle in a membrane
carburetor and therefore has a throttle flap or cylinder which can
be adjusted in a simple manner for controlling the volume flow.
Here, it is advantageous that the throttle element of an air
channel is position-dependently coupled to the throttle flap of the
mixture-preparation device. This position-dependent coupling can be
linear but can also be configured to be adapted to a curve, for
example, progressively opening and can also include lost motion in
order to make possible a time-dependent delayed opening of the air
throttle element with reference to the carburetor throttle flap.
This is achieved in a simple manner with the configuration of
actuating arms or cam discs which connect the throttle flap levers
of the various throttle flaps to each other. The coupling function
is determined by the form and length of the actuating arms and cam
discs. It is practical to be able to adjust the lengths of the
actuating arms.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will now be described with reference to the
drawings wherein:
[0011] FIG. 1 is a side elevation view, partially in section, of a
two-stroke engine having transfer channels lying on opposite sides
of the cylinder;
[0012] FIG. 2 is a section view taken through a cylinder of a
two-stroke engine having an air filter mounted thereon and an
exhaust-gas muffler;
[0013] FIG. 3 is a detail view showing a longitudinal section
through a transfer channel with the air channel connected thereto
via a membrane valve; and,
[0014] FIG. 4 is a schematic showing a cascade arrangement of the
throttles of the air channel.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0015] The two-stroke engine 1 shown in FIG. 1 includes essentially
a cylinder 2 and a piston 5 movable up and down in the cylinder.
The piston 5 imparts rotational movement to a crankshaft 7 via a
connecting rod 6. The crankshaft 7 is arranged in the crankcase 4.
The piston 5 is held at the end of the connecting rod 6 by a piston
bolt 5a to facilitate pivotal movement of the connecting rod.
[0016] A combustion chamber 3 is formed in the cylinder 2 and this
chamber is delimited by the base 13 of the piston 5. The combustion
chamber 3 includes an outlet 10 through which the combustion gases
are directed away after a work stroke. The air/fuel mixture, which
is needed to operate the engine 1, is supplied to the crankcase 4
from a mixture-preparation device 8 via an inlet 11 and an intake
channel 9 which is connected to the inlet 11. The
mixture-preparation device 8 is preferably a membrane
carburetor.
[0017] In the embodiment shown, the inlet 11 is slot-controlled by
the wall surface 30 of the piston 5. In the start position of the
piston 5 shown in FIG. 1, the inlet 11 is completely closed by the
wall surface 30. The configuration of the inlet 11 can preferably
be as a membrane inlet. The air/fuel mixture, which is already
drawn into the crankcase 4, is therefore compressed with a further
movement of the piston 5 in the direction of arrow 50 toward bottom
dead center and flows into the combustion chamber via transfer
channels 14 of which one is shown in section in FIG. 3.
[0018] As shown in FIGS. 1 and 2, two transfer channels 14 are
arranged in the embodiment on each side of a symmetry plane 49 of
the cylinder 2. The symmetry plane 49 includes the cylinder axis 17
and partitions the outlet 10, that is, the outlet window. The
number of transfer channels 14 is given here only by way of
example; n-channels (n.gtoreq.3) are possible.
[0019] The first end 20 of a transfer channel 14 lies opposite the
cylinder head 18 and opens into the combustion chamber 3 via an
entry window 12 or 15 in the cylinder wall 16; whereas, the second
end 19 of each transfer channel 14 faces toward the crankcase 4 and
opens thereto. As shown in FIG. 1, the entry window 15 is assigned
to the two channels 14 close to the outlet 10 and the entry window
12 is assigned to the two channels 14 remote from the outlet
10.
[0020] As shown especially in FIG. 3, in this embodiment, each
transfer channel 14 runs in the cylinder wall 16 essentially
parallel to the cylinder axis 17. The transfer channel 14 can,
however, also have a configuration departing from the embodiment
shown. Thus, the transfer channel can run curved in the flow
direction.
[0021] As shown in FIGS. 2 and 3, the transfer channel 14, which is
configured closed toward the piston, is connected to a preferably
outer air channel (22a, 22b) between the first end 20 and the
second end 19. A check valve 21 closes the flow connection between
the air channel (22a, 22b) and the transfer channel 14 and opens
into the transfer channel 14. In the embodiment shown, the check
valve 21 is configured as a membrane valve. In the open position
corresponding to FIG. 3, the membrane 23 clears an outlet slot 24
which faces toward the roof 25 of the transfer channel 14. In the
open position shown, the membrane 23 is held by a sheet metal
support 26 which, together with the connecting piece 27 of the air
channel, is fixed to the outer cylinder wall 29 by an attachment
screw 28.
[0022] In lieu of the membrane valve 21, the inflow of low-fuel air
or fuel-free air is also advantageous via a slot-controlled window
in the cylinder wall 16 and, if required, a peripheral slot in the
piston skirt.
[0023] As shown in FIG. 2, four transfer channels 14 are provided
in the embodiment and these channels lie on opposite-lying sides
(47, 48) of the symmetry plane 49. The transfer channels 14 on side
47 are connected to gas-conducting air channel (22a, 22b),
respectively, and the transfer channels 14 on side 48 are connected
to gas-conducting air channel (22a, 22b), respectively. The air
channels (22a, 22b) are configured as gas-conducting air channels
separate from each other. Here, it is provided that the volumes of
the essentially fuel-free gas flows (40, 41) can be adjusted
differently from each other in the air channels (22a, 22b). For
this purpose, a preferably adjustable throttle (31, 32) is assigned
to each of the air channels (22a, 22b). As shown in the embodiment,
it is practical to assign common, especially adjustable, throttles
(31, 32) to the air channels (22a, 22b), respectively. These air
channels (22a, 22b) open into the transfer channels 14 of a
transfer pair. A transfer pair is formed by the transfer channels
14 which lie at approximately the same elevation on opposite-lying
sides 47 and 48 of the symmetry plane 49.
[0024] The throttles (31, 32), which are assigned to corresponding
ones of the air channels (22a, 22b) of a transfer pair, comprise a
pivotable throttle element such as a cylinder and especially a
throttle flap (33, 34) which is pivotally mounted in corresponding
throttle housings (35, 36), respectively, about a rotational axis
37. The air channel 22a connects to the throttle housing 35 and the
air channel 22b connects to the throttle housing 36. On the clean
air side of an air filter 42, clean air is supplied to the transfer
channels 14 via the throttle housings 35 and 36. The air channels
22 are configured as external pipes and/or tubing 22 as shown in
the embodiment.
[0025] It can also be practical to configure the air channels by
components forming the housing and/or cavities in the cylinder
block. The air channels (22a, 22b) branch from the air filter
housing 43. The air filter 42 functions to filter the combustion
air supplied to the mixture-preparation device 8. The air filter
housing 43 is mounted upstream of the mixture-preparation device 8
in the flow direction 38 of the inflowing combustion air.
Advantageously, the clean space 60 of the air filter 42 is
partitioned by a partition wall 61 into two chambers 62 and 63
separate from each other. The mixture-preparation device 8 is
connected to one chamber 62; whereas, the other chamber 63 is
connected via the throttles (31, 32) to the air channels (22a,
22b). In this way, a passing of fuel into the air channels is
avoided.
[0026] As shown in FIG. 2, the throttle flap housings 35 and 36 are
configured separate from each other as well as separate from the
carburetor housing of the mixture-preparation device 8. The
throttle housings 35 and 36 can be configured as a common housing
component; however, throttle channels 44 and 45 are configured
separately from each other for separately metering the volumes.
[0027] FIG. 4 shows a cascade arrangement with mutually separate
throttles (31, 32). The throttle 31 is connected to the clean air
chamber 63 of the air filter 42; whereas, the second throttle 32 is
connected downstream of the first throttle 31 to the housing 35
thereof. The air channels 22a and 22b are, in turn, connected
separately from each other to the throttles 31 and 32.
[0028] Each of the throttle elements or throttle flaps (33, 34) of
the air channels (22a, 22b) is connected via a pivot shaft to a
throttle flap lever (46a, 46b) so as not to rotate relative thereto
and, via these throttle elements (33, 34), the opening widths (that
is, the passthrough cross section) of the throttle channels 44 or
45 can be adjusted.
[0029] The throttle flaps 33 and 34 are position-dependently
coupled to the throttle flap of the mixture-preparation device 8 or
to its throttle flap pivot shaft 39. For this purpose, actuating
arms 51, 52a and 52b are arranged between the throttle flap levers
39, 46a and 46b. The actuating arms 51, 52a and 52b are pivotably
attached to corresponding ones of the throttle flap levers 39, 46a
and 46b and switch these levers in series. Here, it is advantageous
that each air throttle flap is coupled via an actuating arm (51,
52b) to the carburetor throttle flap or the air throttle flaps (33,
34) are connected in series one behind the other to the carburetor
throttle flap via actuating arms 51 and 52a. With a rigid coupling
of this kind, each position of the throttle flap in the carburetor
is fixedly assigned a position of the throttle flap in the
air-supplying throttle channels 44 and 45. The actuating arms 51
and 52 are adjustable with respect to their lengths, for example,
by configuration as a threaded rod or the like to provide,
individually, a suitable setting of the particular throttle flap 33
and 34 for the gas-supplying air channels 22a and 22b.
[0030] Not only can the absolute position of the throttle flaps
with respect to each other be influenced, but also the opening
characteristics can be influenced by the configuration and length
of the actuating arms (51, 52) as well as their pivot connection
points on the levers (39, 46a, 46b). Additional configurations are
possible by means of lost motion and cam discs. Accordingly, the
opening of the air throttle can lag behind the opening of the
carburetor throttle flap via lost motion. In this way, the
possibility is provided to operate the same two-stroke engine 1 in
accordance with the principle of advanced air as well as in
accordance with the stratified charge principle.
[0031] For example, if the air supply into the air channels 22a,
which open remote from the outlet, is essentially blocked and air
is supplied, via the channels 22b, exclusively to the transfer
channels 14, which are close to the outlet, then the two-stroke
engine is operated in accordance with the principle of stratified
charge. If the air supply via the air channels 22b, which are close
to the outlet, is reduced by adjusting the throttle flap 34, then,
during an induction phase, only a small amount of air can enter
into the transfer channel 14 which is close to the outlet. For this
reason, in the following charge exchange, first the advanced air
flows in and thereafter at least a component quantity of the
air/fuel mixture passes from the crankcase because of the
overpressure, which builds up in the crankcase 4, and because of
the follow-on flow of the air/fuel mixture. The charge principle of
the engine shifts in the direction of the principle of advanced
air.
[0032] If, in each induction phase, air is supplied to the transfer
channels 14, which are close to the outlet, as well as to the
transfer channels 14, which are remote from the outlet, then this
air is supplied in all transfer channels 14 ahead of the follow-on
air/fuel mixture. The two-stroke engine is then operated
exclusively in accordance with the principle of advanced air.
[0033] The above exemplary descriptions of the different controls
of the fluid (preferably air) supplied into the air channels 22a
and 22b makes clear that the two-stroke engine can be operated in
accordance with a stratified charge operation adapted to the
particular operating point, for example, in dependence upon the
load and/or the engine speed. In practice, the coupling of the
throttle flap levers 39, 46a and 46b via correspondingly suitable
actuating arms 51 and 52 takes place in such a manner that the
kinematic, which results from this coupling, is adapted to the
operating performance of the engine. Here, it can be practical to
make the length L of the actuating arms (51, 52) adjustable so that
the particular operating points can be corrected during service and
maintenance.
[0034] Advantageously, the throttle flaps (33, 34) of the air
throttles 31 and 32 are adjusted independently of each other via an
electric actuating arrangement 55. The actuating arrangement 55
includes a control, such as a microprocessor, which detects
operating data of the engine supplied via signal lines. The
microprocessor evaluates these data and correspondingly activates
the actuating device 55.
[0035] The throttle housings (35, 36) are advantageously fixed on
the base 52 of the air filter 42. The throttle channels 44 and 45
branch out of the clean space 63 of the air filter housing 43. The
throttle housings 35 and 36 can be configured as one part with the
base 53 of the air filter.
[0036] The guidance of the air channels 22 from the throttle
housings 35 and 36 to the transfer channels 14 can be separate as
shown by the example of channels 22a or also can first be common as
shown with channels 22b. The channels 22b divide only in the region
of the cylinder. Also, the air channels can be configured
constructively via housing-forming components or by cavities in the
cylinder block.
[0037] It is understood that the foregoing description is that of
the preferred embodiments of the invention and that various changes
and modifications may be made thereto without departing from the
spirit and scope of the invention as defined in the appended
claims.
* * * * *