INTAKE CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to an intake control device for an internal

combustion engine.

2. Description of the Related Art

[0002] It is known that the amount of air to be drawn into the combustion chamber of

an internal combustion engine may be increased using an inertia charging effect. Japanese

Patent Application Publication No. 7-197823 (JP-A-7- 197823) describes an intake control

device for an internal combustion engine having two intake passages with different lengths

from a surge tank to a combustion chamber and a passage length switching valve for

switching the length of the intake passage from the surge tank to the combustion chamber

depending on the operating condition of the internal combustion engine so that an inertia

charging effect may be used to increase the amount of air to be drawn into the combustion

chamber.

[0003] It is also known that the combustion is improved when the air drawn into the

combustion chamber forms a tumble flow in the combustion chamber. The intake control

device for an internal combustion engine described in JP-A-7- 197823 has a tumble switching

valve for forming a tumble flow of air in the combustion chamber in the intake passage

upstream of the combustion chamber. When closed, the tumble switching valve partially

closes the intake passage so that air can flow downstream along only one side of the tumble

switching valve, that is, air flows downstream through only a portion of the intake passage to

form a tumble flow of air into the combustion chamber.

[0004] The intake passage is partially closed by the tumble switching valve to form a

tumble flow of air in the combustion chamber in the intake control device for an internal

combustion engine described in JP-A- 7-197823, whereas there is also an intake device, as

described in, for example, Japanese Patent Application Publication No. 2002-70566

(JP-A-2002-70566), in which an intake passage is partitioned into two passages and one of

the passages may be closed by a tumble control valve at the upstream end of the partition so

that air flows into the combustion chamber only through the other path to form a tumble flow

of air in the combustion chamber.

[0005] Also in the intake device described in JP-A-2002-70566, two intake passages

with different lengths to the combustion chamber are formed and the length of the intake

passage to the combustion chamber is switched with a variable intake length valve depending

on the operating condition of the internal combustion engine so that an inertia charging effect

can be used to increase the amount of air to be drawn into the combustion chamber as much

as possible.

[0006] However, if a configuration in which an intake passage is divided into two

passages by a partition and one of the passages may be closed by a tumble control valve at the

upstream end of the partition to form a tumble flow of air in the combustion chamber is

adopted, as in the intake device described in JP-A-2002-70566, even when the length of the

intake passage to the combustion chamber is switched with the variable intake length valve in

order to achieve an inertia charging effect, a sufficient inertia charging effect may not be

achieved depending on the operating condition of the tumble control valve because the

volume of the intake passage to the combustion chamber changes largely.

SUMMARY OF THE INVENTION

[0007] The present invention provides an intake control device for an internal

combustion engine in which the length of the intake passage to the combustion chamber may

be changed and in which an internal space in the intake pipe is partitioned into two intake

passages by a partition to form a tumble flow of air in the combustion chamber.

[0008] A first aspect of the present invention is an intake control device for an internal

combustion engine including: a surge tank; a first intake passage that extends from the surge

tank and is connected to a combustion chamber; a second intake passage that extends from the

surge tank and is connected to the first intake passage; an intake passage length-changing

valve provided upstream of a connection point where the second intake passage connects to

the first intake passage , that opens and closes the first intake passage; a partition disposed in

the first intake passage that partitions an internal space in the first intake passage downstream

of the connection point along an axis of the first intake passage to form two partitioned intake

passages; a tumble control valve that opens and closes one of the partitioned intake passages,

wherein when the tumble control valve closes one of the partitioned intake passages air drawn

into the combustion chamber through the open partitioned intake passage forms a tumble flow,

the intake control device characterized in that: the length of the second intake passage from

the surge tank to the first intake passage is longer than the length of the first intake passage

from the surge tank to the connection point; and the cross-sectional area of the second intake

passage is smaller than the cross-sectional area of the first intake passage from the surge tank

to the connection point.

[0009] In the second aspect of the present invention, the connection point is closer to

the surge tank than to the combustion chamber, in the first aspect.

[0010] In the third aspect of the present invention, the connection point is adjacent to

the surge tank, in the second aspect.

[0011] In the fourth aspect of the present invention, the second intake passage is

connected to the first intake passage from a direction generally perpendicular to the partition,

and the tumble control valve opens and closes the partitioned intake passages formed on the

side opposite the side on which the second intake passage is connected to the first intake

passage with respect to the partition, in the first to third aspects.

[0012] In the fifth aspect of the present invention, the tumble control valve is attached

to the partition and is rotatable about a pivot shaft that is attached to the partition, in the first

to fourth aspects.

[0013] In the sixth aspect of the present invention, the tumble control valve has a

plate-shaped valve element that is rotatable about the pivot shaft, and the plate-shaped valve

element of the tumble control valve is parallel to the partition when the tumble control valve

has opened the one of the partitioned intake passages, in the fifth aspect.

[0014] In the seventh aspect of the present invention, the pivot shaft of the tumble

control valve is attached to the partition at an end of the partition that is near the combustion

chamber, and the plate-shaped valve element of the tumble control valve is in or near the

same plane as the partition when the tumble control valve has opened the partitioned intake

passage, in the fifth or sixth aspect.

[0015] In the eighth aspect of the present invention, the intake passage

length-changing valve has a plate-shaped valve element, and the plate-shaped valve element

of the intake passage length-changing valve is in or near the same plane as the partition when

the intake passage length-changing valve has opened the first intake passage, in any one of the

first to seventh aspects.

[0016] In the ninth aspect of the present invention, a periphery on the combustion side

of the plate-shaped valve element of the intake passage length-changing valve is adjacent to

the surge tank side end of the partition when the intake passage length-changing valve has

opened the first intake passage, in the eighth aspect.

[0017] In the tenth aspect of the present invention, the intake passage length-changing

valve has two plate-shaped valve elements independently ratatable through different ranges

about two adjacent pivot shafts or one common pivot shaft, and a periphery of one of the

plate-shaped valve elements of the intake passage length-changing valve is adjacent to the

surge tank side end of the partition and a periphery of the other plate-shaped valve element of

the intake passage length-changing valve is adjacent to an end face on the surge tank side of

the second intake passage connected to the first intake passage when the intake passage

length-changing valve has closed the first intake passage, in the ninth aspect.

[0018] In the eleventh aspect of the present invention, the length and passage

cross-sectional area of the first intake passage and the length and passage cross-sectional area

of the second intake passage are set such that air is drawn into the combustion chamber

through the first intake passage with the aid of an inertia charging effect when the engine

speed is higher than a predetermined engine speed and that air is drawn into the combustion

chamber through the second intake passage with the aid of an inertia charging effect when the

engine speed is lower than a predetermined engine speed, in any one of the first to tenth

aspects.

[0019] In the twelfth aspect of the present invention, the intake passage

length-changing valve keeps the first intake passage open and the tumble control valve keeps

the partitioned intake passage open when the engine load is lower than a predetermined

engine load in an engine load range that the internal combustion engine is operating at lower

load than full load or close to full load and the internal combustion engine is performing

stoichiometric combustion in which the air fuel mixture in the combustion chamber is burned

at an air-fuel ratio equal to or close to theoretical air fuel ratio, the intake passage

length-changing valve keeps the first intake passage open and the tumble control valve keeps

one of the partitioned intake passages closed when the engine load is higher than a

predetermined engine load in an engine load range that the internal combustion engine is

operating at lower load than full load or close to full load and the internal combustion engine

is performing lean-burn combustion in which the air fuel mixture in the combustion chamber

is burned at an air-fuel ratio greater than theoretical air-fuel ratio, the operation of the intake

passage length-changing valve and the operation of the tumble control valve are controlled

depending on the engine speed when the engine load is equal to or close to full load, in any

one of the first to eleventh aspects.

[0020] In the thirteenth aspect of the present invention, in the case where the operating

condition of the internal combustion engine is divided into a low speed operating condition, a

low-intermediate speed operating condition, an intermediate-high speed operating condition,

and a high speed operating condition in order of increasing engine speed, the intake passage

length-changing valve keeps the first intake passage closed and the tumble control valve

keeps one of the partitioned intake passages closed when the engine load is equal to or close

to full load and the internal combustion engine is in the low speed operating condition, the

intake passage length-changing valve keeps the first intake passage closed and the tumble

control valve keeps the partitioned intake passage open when the engine load is equal to or

close to full load and the internal combustion engine is in the a low-intermediate speed

operating condition, the intake passage length-changing valve keeps the first intake passage

open and the tumble control valve keeps one of the partitioned intake passages closed when

the engine load is equal to or close to full load and the internal combustion engine is in the

intermediate-high speed operating condition, and the intake passage length-changing valve

keeps the first intake passage open and the tumble control valve keeps the partitioned intake

passage open when the engine load is equal to or close to full load and the internal

combustion engine is in the high speed operating condition, in the first to twelfth aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of the invention will become

apparent from the following description of example embodiments with reference to the

accompanying drawings, wherein like numerals are used to represent like elements and

wherein:

FIG. 1 is a view illustrating an intake control device for an internal combustion engine

according to a first embodiment of the present invention, in which an intake passage

length-changing valve has closed a main intake passage and a tumble control valve has closed

one of partitioned intake passages;

FIG. 2 is a view illustrating, as in the case with FIG. 1, the intake control device for an

internal combustion engine according to the first embodiment of the present invention, in

which the intake passage length-changing valve has closed the main intake passage and the

tumble control valve has opened the partitioned intake passages;

FIG. 3 is a view illustrating, as in the case with FIG. 1, the intake control device for an

internal combustion engine according to the first embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has closed one of the partitioned intake passages;

FIG. 4 is a view illustrating, as in the case with FIG. 1, the intake control device for an

internal combustion engine according to the first embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has opened the partitioned intake passages;

FIG. 5 is a view illustrating a tumble flow of air (air-fuel mixture), which is formed in a

combustion chamber;

FIG. 6 is a view illustrating an engine operating condition divided into a plurality of

ranges depending on the engine speed N and the engine load L;

FIG. 7 is a view illustrating an intake control device for an internal combustion engine

according to a second embodiment of the present invention, in which an intake passage

length-changing valve has closed a main intake passage and a tumble control valve has closed

one of partitioned intake passages;

FIG. 8 is a view illustrating, as in the case with FIG. 7, the intake control device for an

internal combustion engine according to the second embodiment of the present invention, in

which the intake passage length-changing valve has closed the main intake passage and the

tumble control valve has opened the partitioned intake passages;

FIG. 9 is a view illustrating, as in the case with FIG. 7, the intake control device for an

internal combustion engine according to the second embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has closed one of the partitioned intake passages;

FIG. 10 is a view illustrating, as in the case with FIG. 7, the intake control device for an

internal combustion engine according to the second embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has opened the partitioned intake passages;

FIG. 11 is a view illustrating an intake control device for an internal combustion engine

according to a third embodiment of the present invention, in which an intake passage

length-changing valve has closed a main intake passage and a tumble control valve has closed

one of partitioned intake passages;

FIG. 12 is a view illustrating, as in the case with FIG. 11, the intake control device for an

internal combustion engine according to the third embodiment of the present invention, in

which the intake passage length-changing valve has closed the main intake passage and the

tumble control valve has opened the partitioned intake passages;

FIG. 13 is a view illustrating, as in the case with FIG. 11, the intake control device for an

internal combustion engine according to the third embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has closed one of the partitioned intake passages; and

FIG. 14 is a view illustrating, as in the case with FIG. 11, the intake control device for an

internal combustion engine according to the third embodiment of the present invention, in

which the intake passage length-changing valve has opened the main intake passage and the

tumble control valve has opened the partitioned intake passages.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Example embodiments of intake control device for an internal combustion

engine according to the present invention will now be described. In the following

description, the "upper side" in the drawings is referred to as "upper," the "lower side" as

"lower," "right side" as "right," "left side" as "left," and the "right and left direction" as

"lateral direction."

[0022] FIG. 1 to FIG. 4 illustrate a first embodiment of an intake control device for an

internal combustion engine according to the present invention. As shown in FIG. 1, the

intake control device of the first embodiment has a surge tank 1, and an intake pipe (which is

hereinafter referred to as "main intake pipe") 3 extending obliquely leftward and downward

from a lower side of the surge tank 1 and connected to an intake port 2. The main intake

pipe 3 extends generally straight from the surge tank 1 to the intake port 2 and connected to

the intake port 2 such that it is aligned with the intake port 2. The main intake pipe 3 and the

intake port 2 together form an intake passage (hereinafter "main intake passage") 5 that

extends from the surge tank 1 to a combustion chamber 4.

[0023] The intake control device also has an intake pipe (hereinafter "sub-intake

pipe") 6 extending from the right side of the surge tank 1 and connected to the main intake

pipe 3. The sub-intake pipe 6, which extends generally straight to the right from the surge

tank 1 a prescribed length, turns around and extends generally straight to the left, is connected

to the main intake pipe 3 at a point 7 which is closer to the surge tank 1 than to the

combustion chamber 4 and, in particular, adjacent to the surge tank 1. An intake passage

(hereinafter "sub-intake passage") 8 extending from the surge tank 1 to the main intake pipe 3

(that is, the main intake passage 5) is formed by the sub-intake pipe 6.

[0024] The length of the sub-intake passage 8 from the surge tank 1 to the main intake

passage 5 is longer than that of the main intake passage 5 from the surge tank 1 to a

connection point S between the sub-intake passage 8 and the main intake passage 5. The

passage cross-sectional area of the sub-intake passage 8 is smaller than that of the main intake

passage 5 from the surge tank 1 to the connection point S between the sub-intake passage 8

and the main intake passage 5.

[0025] A valve (hereinafter "intake passage length-changing valve") 11 having a

plate-shaped valve element 10 rotatable about a pivot shaft 9 to open and close the main

intake pipe 3 is disposed upstream of the point S (which is hereinafter referred to as "intake

pipe connection point") where the sub-intake pipe 6 is connected to the main intake pipe 3.

The intake passage length-changing valve 11 shown in FIG. 1 and FIG. 2 has closed the main

intake pipe 3 and the intake passage length-changing valve 11 shown in FIG. 3 and FIG. 4 has

opened the main intake pipe 3.

[0026] A partition 14 that partitions an internal space in the main intake passage 5

along the axis of the main intake passage 5 into two intake passages 12 and 13 is disposed

downstream of the intake pipe connection point S in the main intake passage 5. The

partition 14 is a flat plate and disposed such that the width direction of a plane including the

plate is perpendicular or generally perpendicular to the central axis of the combustion

chamber 4. At the end of the partition 14 near the surge tank 1, a valve (which is hereinafter

referred to as "tumble control valve") 17, having a plate-shaped valve element 16 rotatable

about a pivot shaft 15 attached to the end of the partition 14 to open and close the partitioned

intake passage 12, is disposed. The tumble control valve 17 shown in FIG. 1 and FIG. 3 has

closed the partitioned intake passage 12, and the tumble control valve 17 shown in FIG. 2 and

FIG. 4 has opened the partitioned intake passage 12. When the tumble control valve 17 has

opened the partitioned intake passage 12, the plate-shaped valve element 16 of the tumble

control valve 17 is parallel to the partition 14, and, in particular, on the same or generally the

same plane as the partition 14 as shown in FIG. 2 and FIG. 4.

[0027] The sub-intake pipe 6 is connected to the main intake pipe 3 such that the axis

of the sub-intake pipe 6 immediately upstream of the point where it is connected to the main

intake pipe 3 is perpendicular or generally perpendicular to the width direction of a plane

including the partition 14. Also, the sub-intake pipe 6 is connected to the main intake pipe 3

from a direction perpendicular or generally perpendicular to the partition 14. The partitioned

intake passage 12, which is opened and closed by the tumble control valve 17, is the

partitioned intake passage on the side opposite the side on which the sub-intake pipe 6 is

connected to the main intake pipe 3 with respect to the partition 14. In FIG. 1, a fuel

injection valve 18 and an intake valve 19 are also shown.

[0028] When the intake passage length-changing valve 11 has closed the main intake

passage 5 and the tumble control valve 17 has closed the partitioned intake passage 12 (that is,

in the state shown in FIG. 1), air flows from the surge tank 1 through the sub-intake passage 8

into the main intake passage 5, and flows into the combustion chamber 4 only through the

partitioned intake passage 13, which is not closed by the tumble control valve 17. When the

intake passage length-changing valve 11 has closed the main intake passage 5 and the tumble

control valve 17 has opened the partitioned intake passage 12 (that is, in the state shown in

FIG. 2), air flows from the surge tank 1 through the sub-intake passage 8 into the main intake

passage 5, and flows into the combustion chamber 4 through both the partitioned intake

passages 12 and 13.

[0029] When the intake passage length-changing valve 11 has opened the main intake

passage 5 and the tumble control valve 17 has closed the partitioned intake passage 12 (that is,

in the state shown in FIG. 3), air mainly flows from the surge tank 1 directly into the main

intake passage 5, and flows into the combustion chamber 4 only through the partitioned intake

passage 13, which is not closed by the tumble control valve 17. When the intake passage

length-changing valve 11 has opened the main intake passage 5 and the tumble control valve

17 has opened the partitioned intake passage 12 (that is, in the state shown in FIG. 4), air

mainly flows from the surge tank 1 directly into the main intake passage 5, and flows into the

combustion chamber 4 through both the partitioned intake passages 12 and 13.

[0030] Among the shapes of the intake passage through which air flows from the

surge tank 1 into the combustion chamber 4 shown in FIG. 1 to FIG. 4, the inertia charging

effect, which is achieved at a lower engine speed, is highest when the intake passage

length-changing valve 11 and the tumble control valve 17 are in the state shown in FIG. 1,

second highest when in the state shown in FIG. 2, third highest when in the state shown in FIG.

3, and lowest when in the state shown in FIG. 4. In other words, the length and passage

cross-sectional area of the main intake passage 5 and the length and passage cross-sectional

area of the sub-intake passage 8 are set to be the longest and the smallest when the intake

passage length-changing valve 11 and the tumble control valve 17 are in the state shown in

FIG. 1, second longest and smallest when the intake passage length-changing valve 11 and the

tumble control valve 17 are in the state shown in FIG. 2, third longest and smallest when the

intake passage length-changing valve 11 and the tumble control valve 17 are in the state

shown in FIG. 3, and the shortest and the largest when the intake passage length-changing

valve 11 and the tumble control valve 17 are in the state shown in FIG. 4.

[0031] As the intake passage, through which air flows, becomes longer and narrower,

a higher inertia charging effect may be achieved at a low engine speed. That is, as the length

of the intake passage is longer and the cross-sectional area of the intake passage is smaller,

synchronous engine speed regarding so-called intake pulsation will be lower. Therefore,

when the engine speed is the lowest, the highest inertia charging effect may be achieved by

the intake passage length-changing valve 11 and the tumble control valve 17 being controlled

to the state shown in FIG. 1, and when the engine speed is the second lowest, the highest

inertia charging effect may be achieved by the intake passage length-changing valve 11 and

the tumble control valve 17 being controlled to the state shown in FIG. 2. When the engine

speed is the third lowest, the highest inertia charging effect may be achieved by the intake

passage length-changing valve 11 and the tumble control valve 17 being controlled to the state

shown in FIG. 3, and when the engine speed is the highest, the highest inertia charging effect

may be achieved by the intake passage length-changing valve 11 and the tumble control valve

17 being controlled to the state shown in FIG. 4.

[0032] When the tumble control valve 17 has closed the partitioned intake passage 12

as shown in FIG. 1 and FIG. 3, air flows into the combustion chamber 4 only through the

partitioned intake passage which is not closed by the tumble control valve 17, and a tumble

flow of air (air-fuel mixture) is formed in the combustion chamber 4 as indicated by a

reference symbol F in FIG. 5. In FIG. 5, a cylinder head 20, a cylinder block 21, a piston 22,

an exhaust valve 23, an exhaust port 24, spark plug 25 are also shown.

[0033] The control of the intake passage length-changing valve 11 and the control of

the tumble control valve 17 are next described. The internal combustion engine performs

lean-burn combustion, in which the air-fuel mixture in the combustion chamber 4 is burned at

an air-fuel ratio higher than the stoichiometric air-fuel ratio (lean air-fuel ratio) when the

engine operating condition is in a range X shown in FIG. 6 (that is, the engine load is not

equal to or close to full load, the engine speed is relatively low, and the engine load is in a

relatively low range) , and the internal combustion engine performs a stoichiometric

combustion, in which the air-fuel mixture in the combustion chamber 4 is burned at an air-fuel

ratio equal to or close to the stoichiometric air-fuel ratio when the engine operating condition

is in the range Y shown in FIG. 6 (that is, the engine load is not equal to or close to full load,

the engine speed is relatively high, and the engine load is in a relatively high range). When

the internal combustion engine is controlled as the above-mentioned, the intake passage

length-changing valve 11 and the tumble control valve 17 are controlled as described below.

[0034] When the engine operating condition is in the range Y and the internal

combustion engine is performing stoichiometric combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 open as shown in FIG.

4. That is, when the internal combustion engine performs stoichiometric combustion, the

engine load is relatively high and therefore the amount of air to be drawn into the combustion

chamber 4 (which is hereinafter referred to as "intake air amount") must be increased to a

relatively large level. When the intake passage length-changing valve 11 and the tumble

control valve 17 are controlled as described above, pumping loss is reduced and the intake air

amount can be relatively large because air flows into the combustion chamber 4 through the

entire main intake passage 5.

[0035] When the engine operating condition is in the range X and the internal

combustion engine is performing lean-burn combustion, the intake passage length-changing

valve 11 is controlled to keep the main intake passage 5 open and the tumble control valve 17

is controlled to keep the partitioned intake passage 12 closed as shown in FIG. 3. That is, the

internal combustion engine performs lean-burn combustion, the engine load is relatively low

and therefore the intake air amount does not have to be increased very much but good

combustion must be achieved with a small amount of fuel. When the intake passage

length-changing valve 11 and the tumble control valve 17 are controlled as described above, a

tumble flow of air (air-fuel mixture) is formed in the combustion chamber 4, as shown in FIG.

5, because air flows into the combustion chamber 4 only through the partitioned intake

passage 12. Then, mixing of fuel and air is promoted, and good combustion is achieved with

a small amount of fuel.

[0036] In the case where the range in which the engine load is equal to or close to full

load is divided into a low speed range Zl, a low-intermediate speed range Z2, an

intermediate-high speed range Z3, and a high speed range Z4 in the ascending order of engine

speed as shown in FIG. 6, when the engine operating condition is in one of the ranges Zl to

Z4 and the internal combustion engine performs full-load combustion, in which the air-fuel

mixture in the combustion chamber 4 is burned at an air-fuel ratio equal to or close to the

stoichiometric air-fuel ratio or at an air-fuel ratio lower than the stoichiometric air-fuel ratio

(rich air-fuel ratio), the intake passage length-changing valve 11 and the tumble control valve

17 are controlled as described below.

[0037] When the engine operating condition is in the low speed range Zl and the

internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 closed and the

tumble control valve 17 is controlled to keep the partitioned intake passage 12 closed as

shown FIG. 1. That is, when the internal combustion engine performs full-load combustion,

the engine load is very high and therefore the intake air amount must be increased as much as

possible. When the engine operating condition is in the low speed range Zl, an inertia

charging effect may be achieved and the intake air amount may be vary large by the shape of

the intake passage (the shape of the intake passage through which air flows from the surge

tank 1 into the combustion chamber 4) being as narrow and long as possible because of the

relation with the engine speed. Therefore, when the intake passage length-changing valve 11

and the tumble control valve 17 are controlled as described above, a very large amount of air

flows into the combustion chamber 4 by an inertia charging effect because the length and

passage cross-sectional area of the main intake passage 5 and the length and passage

cross-sectional area of the sub-intake passage 8 are set to be the longest and narrowest.

[0038] When the engine operating condition is in the low-intermediate speed range Z2

and the internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 closed and the

tumble control valve 17 is controlled to keep the partitioned intake passage 12 open as shown

in FIG. 2. That is, when the internal combustion engine performs full-load combustion, the

engine load is very high and therefore the intake air amount must be increased as much as

possible. When the engine operating condition is in the low-intermediate speed range Z2, an

inertia charging effect may be achieved and the amount of air may be very large by the shape

of the intake passage being the second narrowest and longest because of the relation with the

engine speed. Therefore, when the intake passage length-changing valve 11 and the tumble

control valve 17 are controlled as described above, a very large amount of air flows into the

combustion chamber 4 by an inertia charging effect because the shape of the intake passage is

at its second narrowest and longest.

[0039] When the engine operating condition is in the intermediate-high speed range

Z3 and the internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 closed as shown in FIG.

3. That is, when the internal combustion engine performs full-load combustion, the engine

load is very high and therefore the intake air amount must be increased as much as possible.

When the engine operating condition is in the intermediate-high speed range Z3, an inertia

charging effect may be achieved and the amount of air may be very large by the shape of the

intake passage being the third narrowest and longest because of the relation with the engine

speed. Therefore, when the intake passage length-changing valve 11 and the tumble control

valve 17 are controlled as described above, a very large amount of air flows into the

combustion chamber 4 by an inertia charging effect because the shape of the intake passage is

at its third narrowest and longest.

[0040] When the engine operating condition is in the high speed range Z4 and the

internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 open as shown in FIG.

4. That is, when the internal combustion engine performs full-load combustion, the engine

load is very high and therefore the intake air amount must be increased as much as possible.

When the engine operating condition is in the high speed range Z4, an inertia charging effect

may be achieved and the intake air amount may be very large by the shape of the intake

passage being as wide and short as possible because of the relation with the engine speed.

Therefore, when the intake passage length-changing valve 11 and the tumble control valve 17

are controlled as described above, because the shape of the intake passage can be the widest

and shortest, a very large amount of air flows into the combustion chamber 4 by an inertia

charging effect.

[0041] When the main intake passage 5, the sub-intake passage 8, the intake passage

length-changing valve 11, and the tumble control valve 17 are constituted and arranged as in

this embodiment, a higher inertia charging effect may be achieved because the volume of the

intake passage from the surge tank 1 to the combustion chamber 4 hardly changes.

[0042] A second embodiment of the intake control device for an internal combustion

engine according to the present invention is described next. FIG. 7 to FIG. 10 illustrate the

second embodiment. In this embodiment, the main intake passage 5 and the sub-intake

passage 8 are the same as those in the first embodiment. However, in this embodiment, the

partition 14, the intake passage length-changing valve 11, and the tumble control valve 17 are

different from those in the first embodiment.

[0043] The intake passage length-changing valve 11 in this embodiment, which is

disposed upstream of the intake pipe connection point (the point where the sub-intake pipe 6

is connected to the main intake pipe 3) S in the main intake pipe 3 and rotatable about the

pivot shaft 9 to open and close the main intake pipe 3, has two plate-shaped valve elements

1OA and 1OB which are rotatable independently through different ranges about the pivot shaft

9 as a common pivot shaft. The intake passage length-changing valve 11 shown in FIG. 7

and FIG. 8 has closed the main intake pipe 3 and the intake passage length-changing valve 11

shown in FIG. 9 and FIG. 10 has opened the main intake pipe 3.

[0044] A partition 14 for partitioning an internal space in the main intake passage 5

along the axis of the main intake passage 5 into two partitioned intake passages is disposed

downstream of the intake pipe connection point S in the main intake passage 5. The

partition 14 is a fiat plate and disposed such that the width direction of a plane including the

plate is perpendicular or generally perpendicular to the central axis of the combustion

chamber 4. Also, the partition 14 extends toward the surge tank 1 such that a periphery of

the valve element 1OA of the intake passage length-changing valve 11 is adjacent to the surge

tank 1 side end of the partition 14 when the intake passage length-changing valve 11 is in the

state shown in FIG. 7.

[0045] The plate-shaped valve element 16 of the tumble control valve 17 is disposed

such that it is rotatable about a pivot shaft 15 attached to an intermediate portion of the

partition 14, in particular, a part of the partition 14 slightly on the surge tank 1 side from the

center thereof, to open and close the partitioned intake passage 12. The tumble control

valve 17 shown in FIG. 7 and FIG. 9 has closed the partitioned intake passage 12, and the

tumble control valve 17 shown in FIG. 8 and FIG. 10 has opened the partitioned intake

passage 12. When the tumble control valve 17 has opened the partitioned intake passage 12,

the plate-shaped valve element 16 of the tumble control valve 17 is parallel to the partition 14,

and, in particular, on the same or generally the same plane as the partition 14 as shown in FIG.

8 and FIG. 10.

[0046] The partitioned intake passage 12, which is opened and closed by the tumble

control valve 17, is the partitioned intake passage on the side opposite the side on which the

sub-intake pipe 6 is connected to the main intake pipe 3 with respect to the partition 14.

When the intake passage length-changing valve 11 is in the state shown in FIG. 10, it is

parallel to the partition 14 and, in particular, on the same plane or generally the same plane as

the partition 14.

[0047] When the intake passage length-changing valve 11 and the tumble control

valve 17 are in the state shown in FIG. 7, air flows from the surge tank 1 through the

sub-intake passage 8 into the main intake passage 5, and flows into the combustion chamber 4

only through the partitioned intake passage 13, which is not closed by the tumble control

valve 17. When the intake passage length-changing valve 11 and the tumble control valve

17 are in the state shown in FIG. 8, air flows from the surge tank 1 through the sub-intake

passage 8 into the main intake passage 5, and flows into the combustion chamber 4 through

both the partitioned intake passages 12 and 13. When the intake passage length-changing

valve 11 and the tumble control valve 17 are in the state shown in FIG. 9, air mainly flows

directly into the main intake passage 5, and flows into the combustion chamber 4 only

through the partitioned intake passage 13, which is not closed by the tumble control valve 17.

When the intake passage length-changing valve 11 and the tumble control valve 17 are in the

state shown in FIG. 10, air mainly flows from the surge tank 1 directly into the main intake

passage 5, and flows into the combustion chamber 4 through both the partitioned intake

passages 12 and 13.

[0048] The shape of the intake passage (the shape of the intake passage, through

which air flows from the surge tank 1 into the combustion chamber 4) is the narrowest and

longest when the intake passage length-changing valve 11 and the tumble control valve 17 are

in the state shown in FIG. 7, second narrowest and longest when in the state shown in FIG. 8,

third narrowest and longest when in the state shown in FIG. 9, and the widest and shortest

when in the state shown in FIG. 10.

[0049] When the tumble control valve 17 has closed the partitioned intake passage 12

as shown in FIG. 7 and FIG. 9, air flows into the combustion chamber 4 through the

partitioned intake passage 13, which is not closed by the tumble control valve 17, and, as

described in association with the first embodiment, a tumble flow of air (air-fuel mixture) is

formed in the combustion chamber 4.

[0050] The control of the intake passage length-changing valve 11 and the control of

the tumble control valve 17 are next described. When the engine operating condition is in

the range Y shown in FIG. 6 and the internal combustion engine is performing stoichiometric

combustion, the intake passage length-changing valve 11 is controlled to keep the main intake

passage 5 open and the tumble control valve 17 is controlled to keep the partitioned intake

passage 12 open as shown in FIG. 10. When the internal combustion engine performs

stoichiometric combustion, the intake air amount (the amount of air to be drawn into the

combustion chamber 4) must be increased to a relatively large level. When the intake

passage length-changing valve 11 and the tumble control valve 17 are controlled as described

above, because air flows into the combustion chamber 4 through the entire main intake

passage 5, pumping loss is reduced and the intake air amount can be relatively large.

[0051] When the engine operating condition is in the range X shown in FIG. 6 and the

internal combustion engine is performing lean-burn combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 closed as shown in FIG.

9. That is, the internal combustion engine performs lean-burn combustion, the intake air

amount does not have to be increased very much but good combustion must be achieved with

a small amount of fuel. When the intake passage length-changing valve 11 and the tumble

control valve 17 are controlled as described above, because air flows into the combustion

chamber 4 only through the partitioned intake passage 12, a tumble flow of air (air-fuel

mixture) is formed in the combustion chamber 4. Then, mixing of fuel and air is promoted,

and good combustion is achieved with a small amount of fuel.

[0052] When the engine operating condition is in the low speed range Zl shown in

FIG. 6 and the internal combustion engine is performing full-load combustion, the intake

passage length-changing valve 11 is controlled to keep the main intake passage 5 closed and

the tumble control valve 17 is controlled to keep the partitioned intake passage 12 closed as

shown FIG. 7. When the internal combustion engine performs full-load combustion, the

intake air amount must be increased as much as possible. When the engine operating

condition is in the low speed range Zl, an inertia charging effect may be achieved and the

intake air amount may be vary large by the shape of the intake passage (the shape of the

intake passage through which air flows from the surge tank 1 into the combustion chamber 4)

being as narrow and long as possible because of the relation with the engine speed.

Therefore, when the intake passage length-changing valve 11 and the tumble control valve 17

are controlled as described above, a very large amount of air flows into the combustion

chamber 4 by an inertia charging effect because of the shape of the intake passage is at its

narrowest and longest.

[0053] When the engine operating condition is in the low-intermediate speed range Z2

shown in FIG. 6 and the internal combustion engine is performing full-load combustion, the

intake passage length-changing valve 11 is controlled to keep the main intake passage 5

closed and the tumble control valve 17 is controlled to keep the partitioned intake passage 12

open as shown in FIG. 8. When the internal combustion engine performs full-load combustion,

the intake air amount must be increased as much as possible. When the engine operating

condition is in the low-intermediate speed range Z2, an inertia charging effect may be

achieved and the intake air amount may be very large by the shape of the intake passage being

the second narrowest and longest because of the relation with the engine speed. Therefore,

when the intake passage length-changing valve 11 and the tumble control valve 17 are

controlled as described above, a very large amount of air flows into the combustion chamber

4 by an inertia charging effect because the shape of the intake passage is at its be the second

narrowest and longest.

[0054] When the engine operating condition is in the intermediate-high speed range

Z3 and the internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 closed as shown in FIG.

9. When the internal combustion engine performs full-load combustion, the intake air

amount must be increased as much as possible. When the engine operating condition is in

the intermediate-high speed range Z3, an inertia charging effect may be achieved and the

amount of air may be very large by the shape of the intake passage being the third narrowest

and longest because of the relation with the engine speed. Therefore, when the intake

passage length-changing valve 11 and the tumble control valve 17 are controlled as described

above, a very large amount of air flows into the combustion chamber 4 by an inertia charging

effect because the intake passage is at its third narrowest and longest.

[0055] When the engine operating condition is in the high speed range Z4 shown in

FIG. 6 and the internal combustion engine is performing full-load combustion, the intake

passage length-changing valve 11 is controlled to keep the main intake passage 5 open and the

tumble control valve 17 is controlled to keep the partitioned intake passage 12 open as shown

in FIG. 10. When the internal combustion engine performs full-load combustion, the intake

air amount must be increased as much as possible. When the engine operating condition is

in the high speed range Z4, an inertia charging effect may be achieved and the intake air

amount may be very large by the shape of the intake passage being as wide and short as

possible because of the relation with the engine speed. Therefore, when the intake passage

length-changing valve 11 and the tumble control valve 17 are controlled as described above, a

very large amount of air flows into the combustion chamber 4 by an inertia charging effect

because the shape of the intake passage is at its widest and shortest.

[0056] When the main intake passage 5, the sub-intake passage 8, the intake passage

length-changing valve 11, and the tumble control valve 17 are constituted and arranged as in

this embodiment, a higher inertia charging effect may be achieved because the volume of the

intake passage from the surge tank 1 to the combustion chamber 4 hardly changes.

Especially, the region designated by a reference symbol Wl is a region where the volume of

the intake passage is changed largely (so-called dead volume) when the intake passage

length-changing valve 11 and the tumble control valve 17 are in the state shown in FIG. 1 in

the first embodiment, but such a region where the volume of the intake passage is changed

largely is not formed in the second embodiment as shown in FIG. 7. As a result, a higher

inertia charging effect may be achieved.

[0057] A third embodiment of the intake control device for an internal combustion

engine according to the present invention is next described. FIG. 11 to FIG. 14 illustrate the

third embodiment. In this embodiment, the main intake passage 5 the sub-intake passage 8,

the intake passage length-changing valve 11, and the partition 14 are the same as those in the

second embodiment. However, in this embodiment, the tumble control valve 17 is different

from those in the second embodiment.

[0058] The plate-shaped valve element 16 of the tumble control valve 17 is disposed

such that it is rotatable about a pivot shaft 15 attached to a part of the partition 14 adjacent to

the combustion chamber side end thereof to open and close the partitioned intake passage 12.

The tumble control valve 17 shown in FIG. 11 and FIG. 13 has closed the partitioned intake

passage 12, and the tumble control valve 17 shown in FIG. 12 and FIG. 14 has opened the

partitioned intake passage 12. When the tumble control valve 17 has opened the partitioned

intake passage 12, the plate-shaped valve element 16 of the tumble control valve 17 is parallel

to the partition 14, and, in particular, on the same or generally the same plane as the partition

14 as shown in FIG. 12 and FIG. 14.

[0059] The intake passage length-changing valve 11 shown in FIG. 11 and FIG. 12 has

closed the main intake pipe 3 and the intake passage length-changing valve 11 shown in FIG.

13 and FIG. 14 has opened the main intake pipe 3. The partitioned intake passage 12, which

is opened and closed by the tumble control valve 17, is on the side opposite the side on which

the sub-intake pipe 6 is connected to the main intake pipe 3 with respect to the partition 14.

[0060] When the intake passage length-changing valve 11 and the tumble control

valve 17 are in the state shown in FIG. 11, air flows from the surge tank 1 through the

sub-intake passage 8 into the main intake passage 5, and flows into the combustion chamber 4

only through the partitioned intake passage 13, which is not closed by the tumble control

valve 17. When the intake passage length-changing valve 11 and the tumble control valve

17 are in the state shown in FIG. 12, air flows from the surge tank 1 through the sub-intake

passage 8 into the main intake passage 5, and flows into the combustion chamber 4 through

both the partitioned intake passages 12 and 13. When the intake passage length-changing

valve 11 and the tumble control valve 17 are in the state shown in FIG. 13, air mainly flows

directly into the main intake passage 5, and flows into the combustion chamber 4 only

through the partitioned intake passage 13, which is not closed by the tumble control valve 17.

When the intake passage length-changing valve 11 and the tumble control valve 17 are in the

state shown in FIG. 14, air mainly flows from the surge tank 1 directly into the main intake

passage 5, and flows into the combustion chamber 4 through both the partitioned intake

passages 12 and 13.

[0061] The shape of the intake passage (the shape of the intake passage, through

which air flows from the surge tank 1 into the combustion chamber 4) is the narrowest and

longest when the intake passage length-changing valve 11 and the tumble control valve 17 are

in the state shown in FIG. 11, second narrowest and longest when in the state shown in FIG.

12, third narrowest and longest when in the state shown in FIG. 13, and the widest and

shortest when in the state shown in FIG. 14.

[0062] When the tumble control valve 17 has closed the partitioned intake passage 12

as shown in FIG. 11 and FIG. 13, air flows into the combustion chamber 4 through the

partitioned intake passage 13, which is not closed by the tumble control valve 17, and, as

described in association with the first embodiment, a tumble flow of air (air-fuel mixture) is

formed in the combustion chamber 4.

[0063] The control of the intake passage length-changing valve 11 and the control of

the tumble control valve 17 are next described. When the engine operating condition is in

the range Y shown in FIG. 6 and the internal combustion engine is performing stoichiometric

combustion, the intake passage length-changing valve 11 is controlled to keep the main intake

passage 5 open and the tumble control valve 17 is controlled to keep the partitioned intake

passage 12 open as shown in FIG. 14. When the internal combustion engine performs

stoichiometric combustion, the intake air amount (the amount of air to be drawn into the

combustion chamber 4) must be increased to a relatively large level. When the intake

passage length-changing valve 11 and the tumble control valve 17 are controlled as described

above, pumping loss is reduced and the intake air amount can be relatively large because air

flows into the combustion chamber 4 through the entire main intake passage 5.

[0064] When the engine operating condition is in the range X shown in FIG. 6 and the

internal combustion engine is performing lean-burn combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 closed as shown in FIG.

13. That is, the internal combustion engine performs lean-burn combustion, the intake air

amount does not have to be increased very much but good combustion must be achieved with

a small amount of fuel. When the intake passage length-changing valve 11 and the tumble

control valve 17 are controlled as described above, a tumble flow of air (air-fuel mixture) is

formed in the combustion chamber 4 because air flows into the combustion chamber 4 only

through the partitioned intake passage 12. Then, mixing of fuel and air is promoted, and

good combustion is achieved with a small amount of fuel.

[0065] When the engine operating condition is in the low speed range Zl shown in

FIG. 6 and the internal combustion engine is performing full-load combustion, the intake

passage length-changing valve 11 is controlled to keep the main intake passage 5 closed and

the tumble control valve 17 is controlled to keep the partitioned intake passage 12 closed as

shown FIG. 11. When the internal combustion engine performs full-load combustion, the

intake air amount must be increased as much as possible. When the engine operating

condition is in the low speed range Zl, an inertia charging effect may be achieved and the

intake air amount may be vary large by the shape of the intake passage (the shape of the

intake passage through which air flows from the surge tank 1 into the combustion chamber 4)

being as narrow and long as possible. Therefore, when the intake passage length-changing

valve 11 and the tumble control valve 17 are controlled as described above, because the shape

of the intake passage is at its narrowest and longest, a very large amount of air flows into the

combustion chamber 4 by an inertia charging effect.

[0066] When the engine operating condition is in the low-intermediate speed range Z2

shown in FIG. 6 and the internal combustion engine is performing full-load combustion, the

intake passage length-changing valve 11 is controlled to keep the main intake passage 5

closed and the tumble control valve 17 is controlled to keep the partitioned intake passage 12

open as shown in FIG. 12. When the internal combustion engine performs full-load

combustion, the intake air amount must be increased as much as possible. When the engine

operating condition is in the low-intermediate speed range Z2, an inertia charging effect may

be achieved and the intake air amount may be very large by the shape of the intake passage

being the second narrowest and longest because of the relation with the engine speed.

Therefore, when the intake passage length-changing valve 11 and the tumble control valve 17

are controlled as described above, a very large amount of air flows into the combustion

chamber 4 by an inertia charging effect because the shape of the intake passage is at its

second narrowest and longest.

[0067] When the engine operating condition is in the intermediate-high speed range

Z3 and the internal combustion engine is performing full-load combustion, the intake passage

length-changing valve 11 is controlled to keep the main intake passage 5 open and the tumble

control valve 17 is controlled to keep the partitioned intake passage 12 closed as shown in FIG.

13. When the internal combustion engine performs full-load combustion, the intake air

amount must be increased as much as possible. When the engine operating condition is in

the intermediate-high speed range Z3, an inertia charging effect may be achieved and the

amount of air may be very large by the shape of the intake passage being the third narrowest

and longest because of the relation with the engine speed. Therefore, when the intake

passage length-changing valve 11 and the tumble control valve 17 are controlled as described

above, because the shape of the intake passage is at its third narrowest and longest, a very

large amount of air flows into the combustion chamber 4 by an inertia charging effect.

[0068] When the engine operating condition is in the high speed range Z4 shown in

FIG. 6 and the internal combustion engine is performing full-load combustion, the intake

passage length-changing valve 11 is controlled to keep the main intake passage 5 open and the

tumble control valve 17 is controlled to keep the partitioned intake passage 12 open as shown

in FIG. 14. When the internal combustion engine performs full-load combustion, the intake

air amount must be increased as much as possible. When the engine operating condition is

in the high speed range Z4, an inertia charging effect may be achieved and the intake air

amount may be very large by the shape of the intake passage being as wide and short as

possible because of the relation with the engine speed. Therefore, when the intake passage

length-changing valve 11 and the tumble control valve 17 are controlled as described above, a

very large amount of air flows into the combustion chamber 4 due to the inertia charging

effect because the shape of the intake passage is at its widest and shortest.

[0069] When the main intake passage 5, the sub-intake passage 8, the intake passage

length-changing valve 11, and the tumble control valve 17 are constituted and arranged as in

this embodiment, a higher inertia charging effect may be achieved because the volume of the

intake passage from the surge tank 1 to the combustion chamber 4 hardly changes.

Especially, because the region Wl, which is formed when the intake passage length-changing

valve 11 and the tumble control valve 17 are in the state shown in FIG. 1 in the first

embodiment and in which the volume of the intake passage is changed largely, is not formed

in the third embodiment as shown in FIG. 11, a higher inertia charging effect can be achieved.

[0070] Also, according to this embodiment, when the partitioned intake passage 12 is

closed by the tumble control valve 17, a stronger tumble flow of air (air-fuel mixture) is

formed in the combustion chamber 4. For example, if the tumble control valve 17 is

attached to an intermediate part of the partition 14 as in the second embodiment shown in FIG.

7 to FIG. 10, a space W2 downstream of the tumble control valve 17 in the partitioned intake

passage 12 is relatively large when the partitioned intake passage 12 is closed by the tumble

control valve 17, as can be understood with reference to FIG. 7, and air accumulates in the

partitioned intake passage 12 downstream of the tumble control valve 17 while the intake

valve 19 is closed. In this case, when the intake valve 19 is opened and air is drawn into the

combustion chamber 4, the air accumulated in the space W2 downstream of the tumble

control valve 17 in the partitioned intake passage 12 is also drawn into the combustion

chamber 4. Thus, the tumble flow of air (air-fuel mixture) formed in the combustion

chamber 4 may be weakened. However, if the tumble control valve 17 is attached to a part

of the partition 14 adjacent to the combustion chamber 4 side end thereof as in the third

embodiment, the space downstream of the tumble control valve 17 in the partitioned intake

passage 12 is relatively small when the partitioned intake passage 12 is closed by the tumble

control valve 17 as can be understood with reference to FIG. 11 and only a small amount of

air is accumulated in the partitioned intake passage 12 downstream of the tumble control

valve 17 while the intake valve 19 is closed. Thus, the amount of air which drawn into the

combustion chamber 4 from the space downstream of the tumble control valve 17 in the

partitioned intake passage 12 when the intake valve 19 is opened is very small and a much

larger amount of air is drawn into the combustion chamber 4 through the partitioned intake

passage 13, which is not closed by the tumble control valve 17. Therefore, a stronger tumble

flow of air (air-fuel mixture) is formed in the combustion chamber 4.

[0071] Also, in the first embodiment, when the intake passage length-changing valve

11 and the tumble control valve 17 are switched from the state shown in FIG. 2 to the state

shown in FIG. 3, the intake passage length-changing valve 11 and the tumble control valve 17

may be simultaneously switched from the state shown in FIG. 2 to the state shown in FIG. 3.

However, to minimize fluctuations in at least in the torque output from the internal

combustion engine that may occur when the intake passage length-changing valve 11 and the

tumble control valve 17 are switched, the tumble control valve 17 may be switched from the

state shown in FIG. 2 to the state shown in FIG. 3 after the intake passage length-changing

valve 11 is switched from the state shown in FIG. 2 to the state shown in FIG. 3. That is, the

intake passage length-changing valve 11 and the tumble control valve 17 may be switched

from the state shown in FIG. 2 through the state shown in FIG. 4 to the state shown in FIG. 3.

[0072] For the same reason, in the second embodiment, when the intake passage

length-changing valve 11 and the tumble control valve 17 are switched from the state shown

in FIG. 8 to the state shown in FIG. 9, the intake passage length-changing valve 11 and the

tumble control valve 17 may be switched from the state shown in FIG. 8 through the state

shown in FIG. 10 to the state shown in FIG. 9. For the same reason, in the third embodiment,

when the intake passage length-changing valve 11 and the tumble control valve 17 are

switched from the state shown in FIG. 12 to the state shown in FIG. 13, the intake passage

length-changing valve 11 and the tumble control valve 17 may be switched from the state

shown in FIG. 12 through the state shown in FIG. 14 to the state shown in FIG. 13.

[0073] In addition, in the first embodiment, when the intake passage length-changing

valve 11 and the tumble control valve 17 are switched from the state shown in FIG. 3 to the

state shown in FIG. 2, the intake passage length-changing valve 11 and the tumble control

valve 17 may be simultaneously switched from the state shown in FIG. 3 to the state shown in

FIG. 3. However, to minimize fluctuations in at least in the torque output from the internal

combustion engine that may occur when the intake passage length-changing valve 11 and the

tumble control valve 17 are switched, the intake passage length-changing valve 11 may be

switched from the state shown in FIG. 3 to the state shown in FIG. 2 after the tumble control

valve 17 is switched from the state shown in FIG. 3 to the state shown in FIG. 2 . That is, the

intake passage length-changing valve 11 and the tumble control valve 17 may be switched

from the state shown in FIG. 3 through the state shown in FIG 4 to the state shown in FIG. 2.

[0074] For the same reason, in the second embodiment, when the intake passage

length-changing valve 11 and the tumble control valve 17 are switched from the state shown

in FIG. 9 to the state shown in FIG. 8, the intake passage length-changing valve 11 and the

tumble control valve 17 may be switched from the state shown in FIG. 9 through the state

shown in FIG. 10 to the state shown in FIG. 8. For the same reason, in the third embodiment,

when the intake passage length-changing valve 11 and the tumble control valve 17 are

switched from the state shown in FIG. 13 to the state shown in FIG. 12, the intake passage

length-changing valve 11 and the tumble control valve 17 may be switched from the state

shown in FIG. 13 through the state shown in FIG. 14 to the state shown in FIG. 12.

[0075] According to the embodiments of the present invention, a high inertia charging

effect can be achieved regardless of the operating condition of the tumble control valve.