U.S. patent application number 09/894139 was filed with the patent office on 2001-11-01 for control device and device for generating swirls in internal combustion engine.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Komuro, Ryoichi, Ohsuga, Minoru, Yamaguchi, Junichi.
Application Number | 20010035154 09/894139 |
Document ID | / |
Family ID | 14070386 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035154 |
Kind Code |
A1 |
Yamaguchi, Junichi ; et
al. |
November 1, 2001 |
Control device and device for generating swirls in internal
combustion engine
Abstract
A control device in an internal combustion engine, interlocking
with a device to generate swirls in a combustion chamber of the
internal combustion engine by providing bypass passages which allow
air to bypass a throttle valve for regulating Intake air flow rate
of the internal combustion engine to control an output power of the
internal combustion engine and allow the air to flow in from the
side of atmosphere to communicate with air intake ports for
respective cylinders on the downstream side of the throttle valve
The device comprises sensors to detect a vehicle speed, a gear
position, an opening of an accelerator, an intake air flow rate and
the like and a processor to determine an operating state of the
internal combustion engine such as a rotating speed, a torque and
the like based on the signals from the sensors, calculating an
operating condition of the internal combustion engine according to
the strength of swirl to be generated based on the operating state,
outputting the calculated values as control signals.
Inventors: |
Yamaguchi, Junichi;
(Hitachi-shi, JP) ; Ohsuga, Minoru; (Katsuta-shi,
JP) ; Komuro, Ryoichi; (Katsuta-shi, JP) |
Correspondence
Address: |
CROWELL & MORING, L.L.P.
P.O. Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
14070386 |
Appl. No.: |
09/894139 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09894139 |
Jun 29, 2001 |
|
|
|
08943097 |
Aug 4, 1997 |
|
|
|
Current U.S.
Class: |
123/308 ;
123/399 |
Current CPC
Class: |
F02D 41/0002 20130101;
F02D 43/00 20130101; F02D 37/02 20130101; F02B 31/085 20130101;
Y02T 10/40 20130101; F02D 2041/0015 20130101; Y02T 10/12 20130101;
F02B 31/08 20130101; F02M 35/1085 20130101; F02M 35/10216 20130101;
F02B 2031/006 20130101 |
Class at
Publication: |
123/308 ;
123/399 |
International
Class: |
F02B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 1993 |
JP |
PCT/JP93/00944 |
Claims
1. A control device in an internal combustion engine, interlocking
with a device to generate swirls in a combustion chamber of the
internal combustion engine by providing bypass passages which allow
air to bypass a throttle valve for regulating intake air flow rate
of the internal combustion engine to control an output power of the
internal combustion engine and allow the air to flow in from the
side of atmosphere to communicate with air intake ports for
respective cylinders on the downstream side of the throttle valve,
which comprises: sensors to detect a vehicle speed, a gear
position, an opening of an accelerator, an intake air flow rate and
the like; and a processor to determine an operating state of the
internal combustion engine such as a rotating speed, a torque and
the like based on the signals from the sensors, calculating an
operating condition of the internal combustion engine according to
the strength of swirl to be generated based on the operating state,
outputting the calculated values as control signals.
2. A control device in an internal combustion engine according to
claim 1, wherein an injection timing of fuel is output as a signal
for the operating condition of the internal combustion engine.
3. A control device in an internal combustion engine according to
any one of claim 1 and claim 2, wherein an ignition timing is
output as a signal for the operating condition of the internal
combustion engine.
4. A control device in an internal combustion engine according to
any one of claim 1, claim 2 and claim 3, wherein an injection
direction of fuel is output as a signal for the operating condition
of the internal combustion engine.
5. A control device in an internal combustion engine, interlocking
with a device to generate swirls in a combustion chamber of the
internal combustion engine by providing bypass passages which allow
air to bypass a throttle valve for regulating intake air flow rate
of the internal combustion engine to control an output power of the
internal combustion engine and allow the air to flow in from the
side of atmosphere to communicate with air intake ports for
respective cylinders on the downstream side of the throttle valve,
which comprises: sensors to detect a vehicle speed, a gear
position, an opening of an accelerator, an intake air flow rate and
the like; and a processor to determine an operating state of the
internal combustion engine such as a rotating speed, a torque and
the like based on the signals from the sensors, determining number
of the bypass passages to be used based on the operating state and
a lean burn control signal.
6. A control device in an internal combustion engine according to
claim 5, wherein an injection timing of fuel is output as a signal
for the operating condition of the internal combustion engine.
7. A control device in an internal combustion engine according to
any one of claim 5 and claim 6, wherein an ignition timing is
output as a signal for the operating condition of the internal
combustion engine.
8. A control device in an internal combustion engine according to
any one of claim 5, claim 6 and claim 7, wherein an injection
direction of fuel is output as a signal for the operating condition
of the internal combustion engine.
9. A swirl generating device in an internal combustion engine to
generate swirls in a combustion chamber of the internal combustion
engine by providing bypass passages which allow air to bypass a
throttle valve for regulating intake air flow rate of the internal
combustion engine to control an output power of the internal
combustion engine and allow the air to flow in from the side of
atmosphere to communicate with air intake ports for respective
cylinders on the downstream side of the throttle valve, wherein: a
plurality of said bypass passages are provided; and the swirl
generating device in an internal combustion engine comprises a
mechanism varying the number of the bypass passages to be used
according to an operating state of the internal combustion
engine.
10. A swirl generating device in an internal combustion engine
according to claim 9, which generates at least two swirls having
different center axes when said bypass passages are communicated
with said air intake port.
11. A control device in an internal combustion engine having a
swirl generating device according to any one of claim 9 and claim
10, wherein an injection direction of fuel is output as a signal
for the operating condition of the internal combustion engine.
12. A control device in an internal combustion engine having a
swirl generating device according to any one of claim 9, claim 10
and claim 11, which comprises: sensors to detect a vehicle speed, a
gear position, an opening of an accelerator, an intake air flow
rate and the like; and a processor to determine an operating state
of the internal combustion engine such as a rotating speed, a
torque and the like based on the signals from the sensors,
determining number of the bypass passages to be used based on the
operating state and a lean burn control signal.
13. A control device in an internal combustion engine according to
any one of claim 9, claim 10, claim 11 and claim 12, wherein an
injection timing of fuel is output as a signal for the operating
condition of the internal combustion engine.
14. A control device in an internal combustion engine according to
any one of claim 9, claim 10, claim 11, claim 12 and claim 13,
wherein an ignition timing is output as a signal for the operating
condition of the internal combustion engine.
15. A control device in an internal combustion engine according to
any one of claim 9, claim 10, claim 11, claim 12, claim 13 and
claim 14, wherein an injection direction of fuel is output as a
signal for the operating condition of the internal combustion
engine.
Description
TECHNICAL FIELD
[0001] The present invention relates to an engine and, more
particularly, to a lean burn engine system in which swirls are
generated in the combustion chamber corresponding to the operating
state of the engine to improve the combustion even in a lean
air-fuel ratio
BACKGROUND ART
[0002] The prior art of improving combustion capability by
generating swirls in the combustion chamber of an engine is known.
Further, there is also known a technology to improve fuel
consumption rate in which lean air-fuel ratio operation of an
engine is performed during a low load operating period in order to
decrease pumping loss of the engine.
[0003] By combining the above technologies, during a low load
operating period an engine is operated under condition of lean
mixture and generating swirls to improve the combustion capability
for decreasing fuel consumption rate, which is well known as
so-called lean burn engine technology
[0004] In the technology of this type, the swirl is preferably
adjusted in an optimum strength corresponding to the operating
condition of the engine More particularly, during a low load
operating period the swirl is strengthened to improve the
combustion capability, and during a high load operating period the
swirl is weakened to suck a great amount of air to increase the
output power. In order to realize the above, a technology is
described in, for example, Japanese Patent Application Laid-Open
No.61-58921 (1986) where an engine of two intake valve type is
constructed such that one of the intake valves composes a straight
port having an intake control valve, and the other composes a
helical port having a bypass passage opened by the intake control
valve. With this construction, during a low load operating period,
the intake control valve is held close to suck air through only the
passage in the side of the helical port to generate a strong swirl
in the combustion chamber. On the other hand, during a high load
operating period, the intake control valve is held open to suck air
through the helical port and the straight port and further through
a bypass passage communicating from the straight port side to the
helical port side to increase the output power by increasing the
amount of intake air.
[0005] However, in such an engine constructed as above, when the
engine is operated under various conditions, there arise problems
as follows.
[0006] Firstly, there is essentially only one mechanism to generate
an optimum swirl, and consequently it is not possible to set
operating conditions of the engine in which optimum swirl is
generated except only one condition. Therefore, for example, when
the engine is set so as to generate an optimum swirl during a low
load operating period in a state of holding the intake control
valve closed, during an intermediate load operating period of the
engine the sufficient intake air flow rate cannot be supplied
through only the helical port and consequently there arises a
problem in that the operating range of the engine capable of
operating with lean air-fuel ratio is narrowed. In the contrary,
when the engine is set so as to generate an optimum swirl during an
intermediate load operating period, during a low load operating
period of the engine there arises a problem in that the swirl is
weakened due to decrease in the speed of intake air flow.
[0007] During a high load operating period of the engine, there
arises a problem in that the output power is decreased due to
decrease in the intake air flow rate comparing to the case of a
conventional engine which has two straight ports although a large
amount of air flow is sucked through the helical port and the swirl
is weakened by the bypass passage.
[0008] Further, in the engine constructed as described above, one
large swirl is generated in the horizontal or in a tilting
direction inside the combustion chamber. However, there is a
problem in that such a large swirl has a small effect to improve
the combustion because the rotating energy of large swirl has
relatively a small effect on mixing air and fuel. Especially in a
spark ignition engine of fuel injecting type, in a case of having
two intake valves as described above, the mist from a fuel
injection valve is generally formed in bi-directional mist flows
directing from the intake pipe to the intake valves. However, the
mist is attached to the wall of the intake pipe passage or the wall
of the combustion chamber. During an intermediate load operating
period of the engine, the fuel is blown aside in the combustion
chamber by the large swirl in the horizontal or in a tilting
direction described above, which causes a problem in that the fuel
near the wall is exhausted without burning to increase HC content
in the exhaust gas, or the fuel consumption rate is increased.
Furthermore, there is a problem in that only a part of the
combustion chamber becomes at a high temperature during combustion
period to increase NO.sub.x content in the exhaust gas.
DISCLOSURE OF THE INVENTION
[0009] The items of the problems to be solved by the present
invention are as follows.
[0010] Firstly, to provide means for generating a swirl having a
proper strength in a wide operating region of an engine.
[0011] Secondarily, to provide means which has a good suction
characteristic to suppress decrease in the output power during a
high load operating period of the engine, and is capable of
generating a swirl having a proper strength during an intermediate
and low load operating period.
[0012] Thirdly, to provide such a swirl and swirl generating means
that the swirl is capable of effectively mixing fuel and air, the
mist of the fuel does not attach to the wall of intake pipe or the
wall of combustion chamber, the ignitability is good, the
combustion efficiency is high, and the exhaust gases such as HC,
NO.sub.x and the like are suppressed to be generated.
[0013] In order to solve the above problems, the present invention
can provide the following means.
[0014] Initially, a plurality of sub-air-intake passages are
provided separately from the main passage of air-intake pipe The
total sum of the cross-sectional areas the sub-air-intake pipes is
made smaller than the cross-sectional area of the main air-intake
passage. The outlet of the sub-air-intake passage opens to a
position near an intake valve inside the main air-intake passage,
and is directed to the gap portion between the intake valve and a
corresponding intake valve sheet such that air enters from the
outer side opposite to the facing side of the two intake valve
sheets. The fuel mist enters from the inner side of the two intake
valve sheets facing to each other to prevent interference with the
intake air when swirls are generated The respective sub-air-intake
passages are constructed such that air enters toward at least two
positions inside the combustion chamber- The pipe diameter and the
pipe length of the sub-air-intake passage is preferably determined
in such a relation as to effectively utilize the inertia effect of
the intake air.
[0015] Further, means for closing the main passage and means for
closing at least one of the sub-air-intake passages depending on
the operating state of the engine are provided.
[0016] During a low load operating period of the engine, the main
passage and a part of the sub-air-intake passages are kept close,
and, thereby, swirls are generated inside the combustion chamber by
the air flowing through the remaining sub-air-intake passages.
During an intermediate load operating period, the main passage is
kept closed and number of sub-air-intake passages are increased,
and, thereby, the need of increasing intake air flow rate is coped
with and plural swirls having different center axes are generated
in the combustion chamber. When the engine enters into a high load
operation, an intake control valve in the main passage is opened
and a large amount of intake air is introduced to keep the torque
of the engine.
[0017] The ignition timing of the mixed gas is delayed comparing to
the case of a conventional engine without swirl if the combustion
speed is increased by the generated swirls. And In a state where
the swirls are not generated such as at a high load operating
state, the ignition timing is set to the same condition as in a
conventional engine.
[0018] Therein, fuel is injected in advance of the ignition timing
by the time interval during which the fuel mist is mixed with the
generated swirls and the mixed portion reaches near a spark plug to
be ignited. The device is constructed such that the direction of
fuel injection is directed toward swirls when the swirls are
generated.
[0019] By constructing the device as described above, the present
invention has the following effects.
[0020] Firstly, since the cross-sectional area of the air-intake
passage can be changed in multi-step by varying the number of
sub-air-intake passages, the swirls generated inside the combustion
chamber can be set to a proper strength within the wider operating
region of the engine comparing to a conventional engine. Thereby,
the total efficiency of combustion in various operating condition
of the internal combustion engine can be improved.
[0021] Secondarily, the amount of intake air flow rate sucked
through the sub-air-intake passages is increased due to the inertia
effect of intake air through the sub-air-intake passages. Thereby,
the region for operating the engine with generating swirls can be
expanded.
[0022] Thirdly, since there is no need to provide swirl generating
means such as a helical port in the main air passage, the
air-intake flow resistance of the main passage is small and the
larger amount of air can be sucked during a high load operating
period.
[0023] Fourthly, a plurality of swirls can be generated inside the
combustion chamber by using a plurality of sub-air-intake passages.
Thereby, the disturbance in the combustion chamber can be increased
with the same intake-air flow rate comparing to the case where
there is only one swirl, and consequently the mixing of air and
fuel is promoted to improve the efficiency of combustion.
[0024] Fifthly, since the injection timing of fuel, the ignition
timing and the direction of fuel injection are adjusted such that
plural swirls are generated around fuel mist and at the same time
the fuel is not interfered with intake air, the fuel can be
prevented from blowing aside near the wall of the combustion
chamber. Thereby, harmful components such as HC, NO.sub.x and the
like in the exhaust gas are decreased.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a top view showing the construction of a first
embodiment in accordance with the present invention.
[0026] FIG. 2 is a side view showing the construction of the first
embodiment in accordance with the present invention.
[0027] FIG. 3 is a view showing the operation during a low Load
operating period of the first embodiment in accordance with the
present invention.
[0028] FIG. 4 is a view showing the operation during a intermediate
load operating period of the first embodiment in accordance with
the present invention.
[0029] FIG. 5 is a view showing the operation during a high load
operating period of the first embodiment in accordance with the
present invention.
[0030] FIG. 6 is an embodiment of a flow chart for setting the
opening of a control valve.
[0031] FIG. 7 is a view showing an injection timing of fuel, an
ignition timing and a direction of fuel injection in a case where
swirl is not generated.
[0032] FIG. 8 is a view showing an injection timing of fuel, an
ignition timing and a direction of fuel injection in a case where
swirl is generated.
[0033] FIG. 9 is a graph showing the limit region for lean air-fuel
ratio and the operable region of the engine in a case where one
sub-air-intake passage is used in the construction of the first
embodiment in accordance with the present invention.
[0034] FIG. 10 is a graph showing the limit region for lean
air-fuel ratio and the operable region of the engine in a case
where two sub-air-intake passages are used in the construction of
the first embodiment in accordance with the present invention.
[0035] FIG. 11 is a graph showing the limit region for lean
air-fuel ratio and the operable region of the engine in the first
embodiment in accordance with the present invention.
[0036] FIG. 12 is a graph showing the limit region for lean
air-fuel ratio and the operable region of engine in a conventional
engine with swirl generating mechanism.
[0037] FIG. 13 is a graph showing the limit region for lean
air-fuel ratio and the operable region of engine in a conventional
engine without swirl generating mechanism.
[0038] FIG. 14 is a top view showing the construction of a second
embodiment in accordance with the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0039] The embodiments of the present invention will be described
in detail below, referring to the accompanying drawings.
[0040] FIG. 1 and FIG. 2 show a first embodiment according to the
present invention. A main passage 110 of an independent air-intake
pipe is directed toward a combustion chamber 103 of an engine
having two intake valves 102. An intake control valve 107 is
provided in the main passage 110, and sub-air-intake passages 101a
and 101b are provided in the upstream of the air-intake control
valve such as to bypass the main passage 110. The total
cross-sectional area of the two sub-air-intake passages 101a and
101b is made such as to become 1/5 to 1/2 of the cross-sectional
area of the upstream of the main passage 110. The intake control
valve 107 is constructed such as to have a larger cross-sectional
area than the cross-sectional area of the upstream of the main
passage 110 and the inlet of the sub-air-intake passage 101b can be
closed with the intake control valve 107.
[0041] A fuel injection valve 105 forms two mist flows flowing from
the main passage 110 toward the inner side of the two intake valves
102 facing to each other, that is, directing in two directions 106a
and 106b toward the center portion of the combustion chamber.
[0042] The outlets of the sub-air-intake passages 101a and 101b
open to a position near the intake valve 102. The air flows flowing
through the sub-air-intake passages 101a and 101b become jet flows
which enter into the combustion chamber 103 through the gaps
between the intake valve and the corresponding valve sheet from the
outer side of the two intake valves 102 facing to each other, that
is, from the side near the wall of the combustion chamber to
generate two swirls 111a, 111b. Therein, the swirl 111a is formed
such as to envelop the mist 106a; and the swirl 111b is formed such
as to envelop the mist 106b. And each of the swirls circulates
along the top surface of a piston 112 and then flows toward a spark
plug 104. Operation of the intake control valve 107 is performed by
a stepping motor 201, and setting of the opening of the intake
control valve is performed by a computer 202.
[0043] FIG. 3 shows the operating state during a low load operating
period of the first embodiment in accordance with the present
invention. The intake control valve 107 is set to a angle .theta.1
where the main passage 110 and the sub-air-intake passage 101b are
kept close. The air 108 flowing in the upstream of the main passage
110 passes through the sub-air-intake passage 101a and generates a
swirl 111a inside the combustion chamber 103. Since the jet flow
from the sub-air-intake passage 101a is small comparing to the size
of the combustion chamber, the air flow sucked through the intake
valve 102 can be put aside and therefore a swirl 111a can be
generated with a small amount of air flow rate. Although the swirl
111a circulates such as to envelop the fuel mist 106a, 106b, the
mist is not blown aside toward the wall of the combustion chamber
since the air flow rate is small. Thereby, the combustion can be
performed well.
[0044] FIG. 4 shows the operating state during a intermediate load
operating period of the first embodiment in accordance with the
present invention. The intake control valve 107 is set to a angle
.theta.2 where the main passage 110 is kept close and the
sub-air-intake passage 101b is kept open. The air 108 flowing in
the upstream of the main passage 110 passes through the
sub-air-intake passages 101a and 101b and generates two swirls 111a
and 111b inside the combustion chamber 103. The swirls 111a and
111b circulate such as to envelop the fuel mist 106a and 106b,
respectively. The swirls 111a and 111b promote the mixing of air
and fuel further than in a case of single swirl with the same
intake air flow rate, and the mist is not blown aside toward the
wall of the combustion chamber. Thereby, the combustion can be
performed well.
[0045] FIG. 5 shows the operating state during a high load
operating period of the first embodiment in accordance with the
present invention. The intake control valve 107 is set to a angle
.theta.3. Therein, most of the intake air 108 passes through the
main passage 110 to be sucked into the combustion chamber 103.
Since there is no swirl generating means such as a helical port and
consequently the suction flow resistance is low, a large amount of
air can be sucked. Thereby, a required output power can be
obtained. Therein, although the sub-air-intake passages 101a and
101b are kept open, each of the air flow rates passing through each
of passages is approximately proportional to each of the
cross-sectional areas. Therefore, the air flow rates passing
through the sub-air-intake passages 101a and 101b are small and
consequently generate no swirl.
[0046] Although, in order to make the explanation simple, the
description in this embodiment has made on the cases where the
intake control valve 107 shuts ON or OFF, that is, opens or closes
the respective passages, it is possible to set the passages in a
half-open state, for example, to set the opening of the control
valve 107 in such a state that the main air passage 110 is
half-open. This can expand the region of operating condition of the
engine where swirls are generated.
[0047] FIG. 6 shows a flow chart for setting the opening of the
intake control valve when the present invention is applied to an
engine in a vehicle. In the first place, the intention of a driver
is detected, and the required rotating speed and the required
torque of an engine are calculated. The intention of the driver is
defined as a value of required shaft power calculated from, for
example, the degree of a pushing-down amount of an accelerator
pedal or the change in the pushing-down amount. The operating
condition of the engine, that is, the rotating speed and the torque
required now are calculated from the value and information on
vehicle speed and gear position. Next, what swirls to be generated
in the combustion chamber is optimum to the condition set based on
the information is searched by referring to a map of engine control
value.
[0048] First, it is judged whether the condition is suitable for a
single directional swirl or not. If it is suitable for a single
directional swirl state, the opening of the intake control valve is
set to .theta.1 as shown in FIG. 3. If it is not suitable for a
single directional swirl state, it is judged whether the condition
is suitable for a bi-directional swirl state or not. If it is
suitable for a bi-directional swirl state, it is judged whether the
condition is in the region where the intake air flow rate can be
sufficiently supplied only by the sub-air-intake passages or not.
If the intake air flow rate can be sufficiently supplied only by
the sub-air-intake passages, the opening of the intake control
valve is set to .theta.2 as shown in FIG. 4 to generate
bi-directional swirls. If the intake air flow rate cannot be
sufficiently supplied only by the sub-air-intake passages, the
opening of the intake control valve is set to .theta.2' which is an
intermediate state of .theta.2 as shown in FIG. 4 and .theta.3 as
shown in FIG. 5. Thereby, the operating region with bi-directional
swirls can be expanded by supplying an additional air flow through
the main passage by nearly the same amount of the air flow rate
through the sub-air-intake passages at maximum. If the condition is
not suitable either for a single directional swirl state nor a
bi-directional swirl state, the opening of the intake control valve
is set to .theta.3 to hold the main passage open. As described
above, swirls suitable for an operating state can be generated in
the combustion chamber and it is, therefore, possible to realize a
lean burn combustion by improving combustion.
[0049] FIG. 7 and FIG. 8 show an embodiment of changing the
injection timing of fuel, the ignition timing and the direction of
fuel injection depending on the strength of swirls. The fuel
injection valve 105 used is an air assist injector which promotes
atomization by air and bends the fuel mist flow by the air for
atomization to change the direction of fuel injection.
[0050] FIG. 7 shows a case where swirl is not generated. Air 108
flows through the main passage 110, its velocity is slow and
consequently the speed of combustion is also slow. Therefore, in
order to ignite the fuel well when a piston 112 comes to near the
top dead point of compression, it is necessary to set the injection
timing of fuel earlier and also to set the ignition timing earlier.
The injecting direction of the fuel mist 106 is set such as to
direct a little downward in the figure from the direction of the
line connecting between the fuel injection valve, and the two
intake valves and most amount of fuel is injected in that direction
with considering that the mist is drifted by the air flow from the
main passage 110. Thereby, dense mixture can be formed near a spark
plug 104. FIG. 8 shows a case where swirl is generated. Air 108
flows through the sub-air-intake passage 101 and generates a swirl
111 having a high velocity. Therein, the speed of combustion is
fast. Therefore, in order to ignite the fuel well when a piston 112
comes to near the top dead point of compression, it is necessary to
set the injection timing of fuel later than in the case of FIG. 7
and also to set the ignition timing later. Since the fuel does not
interfere with the intake air, the injecting direction of the fuel
mist 106 is set such as to direct in the direction of the line
connecting between the fuel injection valve and the two intake
valves more directly than in the case of FIG. 7. Thereby, as
described in connection with FIG. 4, mixing of the fuel and the air
can be promoted, and the fuel mist can be suppressed to attach to
the wall of the air intake pipe or the wall of the combustion
chamber.
[0051] FIG. 9, FIG. 10 and FIG. 11 show the limit region for lean
air-fuel ratio and the operable region of the engine in the
construction of the first embodiment in accordance with the present
invention in a case where one sub-air-intake passage is used, in a
case where two sub-air-intake passages are used, and in a case
where the number of the sub-air-intake passages is varied according
to the chart shown in FIG. 6, respectively. FIG. 12 and FIG. 13
show the limit region for lean air-fuel ratio and the operable
region of engine in a conventional engine with swirl generating
mechanism and without swirl generating mechanism, respectively.
[0052] The region outside boundary in each of the figures indicates
the region where the engine cannot operate with the rotating speed
and the torque at the point. Each of the numbers in the figure
indicates the limit of lean air-fuel ratio in each of the regions.
According to the embodiment, it can be understood that the engine
according to the present invention has a wide region where the
engine can be operated with lean air-fuel ratio, and can keep the
same high output power as an engine without swirl generating
mechanism can.
[0053] FIG.14 shows the construction of a second embodiment
according to the present invention. A main passage 110 of an
air-intake pipe is directed toward a combustion chamber 103 of an
engine having two intake valves 102. An intake control valve 107 is
provided in the main passage 110, and sub-air-intake passages 101a,
101b, 101c and 101d are provided in the upstream of the air-intake
control valve such as to bypass the main passage 110. The total
cross-sectional area of the four sub-air-intake passages 101a to
101d is made such as to become 1/5 to 1/2 of the cross-sectional
area of the upstream of the main passage 110. The intake control
valve 107 is constructed such as to have a larger cross-sectional
area than the cross-sectional area of the upstream of the main
passage 110 and each of the inlets of the sub-air-intake passages
101c and 101b, 101d can be closed with the opening of the intake
control valve 107 one-by-one. A fuel injection valve 105 forms two
mist flows 106a and 106b directing from the main passage 110 to the
two intake valves 102.
[0054] The outlets of the sub-air-intake passages 101a, 101b, 101c
and 101d open to a position near the intake valve 102. Each of the
air flows flowing through the sub-air-intake passages 101a and 101b
and the air flows flowing through the sub-air-intake passages forms
a pair of jet flows which enter into the combustion chamber 103
through the gaps between the intake valve and the corresponding
valve sheet from the outer side of the two intake valves 102 facing
to each other to generate two swirls 111a, 111b. Therein, the swirl
111a is formed such as to envelop the mist 106a, and the swirl 111b
is formed such as to envelop the mist 106b. And each of the swirls
circulates along the top surface of a piston 112 and then flows
toward a spark plug 104. Operation of the intake control valve 107
is performed by a stepping motor 201, and setting of the opening of
the intake control valve is performed by a computer 202.
[0055] With the construction described above, when the engine is
operated in a low load operating state and, therefore, the amount
of intake air flow rate is small, only the sub-air-intake passage
101a is used and the velocity of intake air can be increased
similar to the first embodiment according to the present invention
shown in FIG. 3. When the load increases and the intake air flow
rate is required to be increased, bi-directional swirls can be
generated using the tow sub-air-intake passages 101a and 101d by
opening the intake control valve 107 similar to the first
embodiment according to the present invention shown in FIG. 4. When
the load is further increases, the amount of intake air flow rate
can be increased with keeping the bi-directional swirls using the
four sub-air-intake passages 101a to 101d by opening the intake
control valve 107 further. It is no need to say that it is possible
to set the opening of the control valve 107 in such a state that
the main air passage 110 is half-open similar to the first
embodiment according to the present invention. This can expand the
region of operating condition of the engine where swirls are
generated.
[0056] Although, in these embodiments, the cases of two and four
sub-air-intake passages have been described, the present invention
is not limited to these cases. Swirls can be generated with
arbitrary number of sub-air-intake passages. Further, although the
cases of one and two swirls have been described, plural swirls can
be generated in the combustion chamber by setting each of the
sub-air-intake passages with varying the position and the direction
of its outlet one-by-one. In this case, it is no need to say that
mixing of air and fuel is promoted to perform good combustion by
changing the injection timing of fuel.
[0057] According to the present invention, since the
cross-sectional area of the air-intake passage can be changed in
multi-step by varying the number of sub-air-intake passages, the
swirls generated inside the combustion chamber can be set to a
proper strength within the wider operating region of the engine
comparing to a conventional engine. Thereby, the combustion in
various operating condition of the internal combustion engine can
be improved, and good combustion can be obtained in a case of lean
combustion.
[0058] Further, since there is no need to provide swirl generating
means such as a helical port in the main air passage, the
air-intake flow resistance of the main passage is small and a high
output power can be kept.
[0059] Furthermore, a plurality of swirls can be generated inside
the combustion chamber by using a plurality of sub-air-intake
passages. Thereby, the disturbance in the combustion chamber can be
increased with the same intake-air flow rate comparing to the case
where there is only one swirl, and consequently the mixing of air
and fuel is promoted to improve the efficiency of combustion.
Therefore, the combustion is stable even in a lean combustion and
the limitation of lean combustion can be expanded, and harmful
components such as HC, NO.sub.x and the like in the exhaust gas can
be decreased.
[0060] Still further, by regulating the injection timing of fuel,
the ignition timing and the direction of fuel injection such that
plural flames are generated around fuel mist and the fuel is not
interfered with intake air, the fuel can be prevented from blowing
aside near the wall of the combustion chamber. Thereby, good
combustion can be performed in and near the center of the
combustion chamber, and harmful components such as HC, NO.sub.x and
the like in the exhaust gas are decreased.
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