Intake air control device for an internal combustion engine

An intake air control device including a reed valve passage for supplying intake air via reed valves, and a sub intake passage for creating a swirl in the combustion chamber. The intake air control device further comprises a main intake passage for supplying intake air without passing same through the reed valves. A selection unit selects a passage through which the intake air is passed in response to a current engine driving condition, by selecting the sub intake passage when the current engine driving condition is a low engine speed and low engine load driving condition, selecting the reed valve passage when the current engine driving condition is a low engine speed and high engine load driving condition, and selecting the main intake passage when the current engine driving condition is a high engine speed driving condition.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an intake air control device for an 
internal combustion engine, the device comprising a reed valve passage for 
supplying intake air via reed valves, to thereby prevent a back flow of 
intake air, and a sub intake passage for creating a swirl in a combustion 
chamber. 
2. Description of the Related Art 
Japanese Unexamined Patent Publication No. 58-210322 discloses an intake 
air control device comprising a reed valve passage in which reed valves 
are arranged, and a sub intake passage, for creating a swirl in a 
combustion chamber, having a control valve and bypassing the reed valves. 
In the above intake air control device, when in a low engine speed and low 
engine load driving condition, the sub intake passage is opened by the 
control valve so that all of the intake air is supplied to the combustion 
chamber and passes through the sub intake passage, whereby a good 
combustion can be obtained by the creating of a swirl in the combustion 
chamber. When in a low engine speed and high engine load driving 
condition, the sub intake passage is closed by the control valve so that 
all of the intake air passes through the reed valve passage and is 
supplied to the combustion chamber, whereby a back flow of intake air is 
prevented by the reed valves and the control valve and it is possible to 
obtain a higher torque, to thus increase the charging efficiency. 
In a high engine speed driving condition, a large amount of intake air is 
required, and therefore in the above intake air control device, the intake 
air is supplied to and passes through the reed valve passage in this 
driving condition. The reed valves are relatively large and are arranged 
in a reed valve passage having a large cross section, but a considerable 
pressure loss is generated when the reed valves are fully open to allow a 
large amount of intake air to pass therethrough, and thus a desired torque 
cannot be obtained and a sufficient amount of intake air is not supplied 
to the combustion chamber, and accordingly, a considerable pressure loss 
occurs. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide an intake air 
control device for an internal combustion engine, which device ensures 
that a sufficient amount of intake air is supplied during a high engine 
speed condition, and can maintain the same effect during a low engine 
speed condition. 
According to the present invention there is provided an intake air control 
device comprising: a main intake passage leading to a combustion chamber 
and allowing an amount of intake air required in a high engine speed 
driving condition to pass therethrough; a reed valve passage leading to 
the combustion chamber and having reed valves for allowing a sufficient 
amount of intake air required in a low engine speed and high engine load 
driving condition to pass therethrough only from upstream to downstream 
thereof; a sub intake passage leading to the combustion chamber for 
creating a swirl therein; detection means for detecting a current engine 
driving condition, all of the detected engine driving conditions being 
divided into a low engine speed and low engine load driving condition, a 
low engine speed and high engine load driving condition and high engine 
speed driving condition, each corresponding to a required amount of intake 
air; and selection means for selecting a passage through which the intake 
air is passed in response to said current engine driving condition, by 
selecting the sub intake passage when the current engine driving condition 
is a low engine speed and low engine load driving condition, selecting the 
reed valve passage when the current engine driving condition is a low 
engine speed and high engine load driving condition, and selecting the 
main intake passage when the current engine driving condition is a high 
engine speed driving condition. 
The present invention will be more fully understood from the description of 
preferred embodiments of the invention set forth below, together with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a first embodiment of the present invention. In this figure, 
reference numeral 1 designates a reed valve assembly having four side 
walls 1a, 1b, 1c, 1d (only 1d is not shown), defining an inside space 2a 
wherein a control valve 3 pivoting on a shaft 3a is mounted. Each of the 
side walls 1a, 1b, 1c, 1d is provided with a pair of openings 1e extending 
in a longitudinal direction upstream of the control valve 3, and a pair of 
reed valves 1f and stoppers 1g thereof are mounted at the each of the side 
walls 1a, 1b, 1c, 1d to cover the openings le and opening only outward 
therefrom. All of these reed valves 1f can allow an amount of intake air 
required during a low engine speed and high engine load driving condition 
to pass therethrough, because a longitudinal length of the reed valve 
assembly 1 can be freely selected and the reed valves 1f can be relatively 
large. 
A main intake passage 2 leading to a combustion chamber 20 via an intake 
valve 21 consists of the inside space 2a of the reed valve assembly 1, an 
upstream space 2b, and a downstream space 2c, and is formed so as to allow 
an amount of intake air required during a high engine speed driving 
condition to pass therethrough. A space 4a surrounding the reed valve 
assembly 1 called a reed valve passage 4 is communicated with the 
downstream space 2c, and intake air is passed therethrough via the reed 
valves 1f. 
A sub intake passage 5 for creating a swirl in the combustion chamber 20 
communicates the inside space 2a downstream of the reed valves 1f with 
the downstream space 2c, at a point close to the intake valve 21. 
The control valve 3 closes the inside space 2c downstream of a opening 5a 
of the sub intake passage 5 formed in the lower side wall 1c, when in a 
first pivoted position as shown by a dotted line, and closes the inside 
space 2c upstream of the opening 5a when in a second pivoted position as 
shown by a chain line. The lower side wall 1c at a point close to the 
opening 5a and the upper side wall 1a at a point opposite to the opening 
5a are provided with recess 1h, respectively, allowing the control valve 3 
to be pivoted between the first pivoted position and the second pivoted 
position. 
A step motor 6 for driving the control valve 3 is mounted outside of the 
main intake passage 2, and is controlled by the electronic control unit 
(ECU) 50. 
The ECU 50 is constructed as a digital computer and includes a ROM (read 
only memory) 52, a RAM (random access memory) 53, a CPU (microprocessor, 
etc.) 54, an input port 55, and an output port 56. The ROM 52, the RAM 53, 
the CPU 54, the input port 55, and the output port 56 are interconnected 
by a bidirectional bus 51. 
A distributor 30 is provided with a crank angle sensor 31 connected to the 
input port 55. An accelerator pedal sensor 41 for detecting a degree of 
opening of an accelerator pedal 40 is also connected to the input port 55, 
via an AD converter 59. The output port 56 is connected to the step motor 
6 via a drive circuit 57. 
The ECU 50 operates the control valve 3 according to a flow chart shown in 
FIG. 2. 
At step S1, a current engine speed is detected on the basis of a signal 
from the crank angle sensor 31, and the routine goes to step S2. 
At step S2, a current engine load is detected on the basis of a signal from 
the accelerator pedal sensor 41, and the routine goes to step S3. 
At step S3, a search is made for a current engine driving condition, on the 
basis of the current engine speed and load, and the routine goes to step 
S4. 
At step S4, the control valve 3 is actuated on the basis of the current 
engine driving condition. 
The search at step S3 is carried out by using a first engine speed-load map 
shown in FIG. 3, in which all of the engine driving conditions are divided 
into three driving conditions I, II, and III corresponding to a required 
amount of intake air. The actuating at step S4 is carried out as follows. 
When in the low engine speed and low engine load driving condition I, which 
includes an idling condition, the control valve 3 is pivoted by the step 
motor 6 to the first pivoted position (shown by the dotted line), whereby 
the control valve 3 serves as first closing means for closing the main 
intake passage 2 consisting of the inside space 2a of the reed valve 
assembly 1, the upstream space 2b and the downstream space 2c, between a 
branched point (the opening 5a) of the sub intake passage 5 and a merging 
point (an opening of the sub intake passage 5 leading to the downstream 
space 2c) Accordingly, almost the entire amount of intake air passes 
through the sub intake passage 5, and thus a good combustion can be 
obtained by a swirl created thereby in the combustion chamber 20. 
When in the low engine speed and high engine load driving condition II, the 
control valve 3 is pivoted by the step motor 6 to the second pivoted 
position (shown by the chain line), whereby the control valve 3 serves as 
second closing means for closing the main intake passage 2, between a 
branched point (the opening 1e in each of the side walls 1a, 1b, 1c, 1d of 
the reed valve assembly 1) of the reed valve passage 4 and a merging point 
(an opening of the passage 4 leading to the downstream space 2c), and 
upstream of the branched point of the sub intake passage 5. Accordingly, 
the entire amount of intake air passes, via the reed valves 1f, from the 
space 4a surrounding the reed valve assembly 1 to the downstream space 2c 
and is supplied to the combustion chamber 20, whereby a back flow of 
intake air is prevented by the control valve 3 and the reed valves 1f, and 
accordingly, the charging efficiency is increased and a higher torque is 
obtained. 
When in the high engine speed driving condition III the control valve 3 is 
pivoted by the step motor 6 to a third pivoted position as shown by the 
solid line, to open the main intake passage 2. Accordingly, a large amount 
of intake air required in this driving condition passes through the main 
intake passage 2 and is supplied to the combustion chamber 20, without 
passing through the reed valves 1f, to thereby ensure a sufficient supply 
thereof, and avoid a drop in the torque. 
In the first embodiment, the manufacturing costs thereof can be reduced 
because the single control valve 3 serves as both the first and the second 
closing means. 
FIG. 4(A) shows a second embodiment; here only the difference between the 
first and second embodiments is explained, as follows. 
A reed valve assembly 1' is formed such that the control valve 3 and 
portions of each side walls 1a, 1b, 1c, 1d surrounding the valve 3 from 
the reed valve assembly 1 in the first embodiment are omitted. A space 4a 
surrounding the reed valve assembly 1' communicates a sub intake passage 5 
via a portion 2'c of the downstream space 2c close to an inside space 2a 
of the reed valve assembly 1'. 
FIG. 4(B) shows an enlarged view of a control valve 3'. As shown in the 
figure, reference numeral 3'a designates a pivoting shaft arranged in the 
portion 2'c of the downstream space 2c. The control valve 3' is slidable 
mounted on a shaft of a bolt 3'b having a head and fixed in the pivoting 
shaft 3'a, and is biased toward the head by a spring 3'c inserted in the 
shaft of the bolt 3'b. The control valve 3' is movable toward the pivoting 
shaft 3'a against the spring 3'c, and is driven together with the pivoting 
shaft 3'a by a step motor 6 controlled by an ECU (not shown), such as the 
ECU 50 in the first embodiment, and can be pivoted between a first pivoted 
position as shown by the dotted line and a second pivoted position as 
shown by the chain line. 
When in the low engine speed and low engine load driving condition I, which 
includes an idling condition, the control valve 3' is pivoted by the step 
motor 6 to the first pivoted position (shown by the dotted line), whereby 
the control valve 3' serves as third closing means for closing the main 
intake passage 2 consisting of the inside space 2a of the reed valve 
assembly 1', the upstream space 2b and the downstream space 2c containing 
the portion 2'c, between the branched point and the merging point of the 
sub intake passage 5, and downstream of the merging point of the reed 
valve passage 4. When in the low engine speed and high engine load driving 
condition II, the control valve 3' is pivoted by the step motor 6 to the 
second pivoted position (shown by the chain line), whereby the control 
valve 3 serves as the second closing means for closing the main intake 
passage 2, between the branched point and the merging point of the reed 
valve passage 4, and upstream of the branched point of the sub intake 
passage 5. When in the high engine speed driving condition III, the 
control valve 3' is pivoted by the step motor 6 to a third pivoted 
position as shown by the solid line, to thereby open the main intake 
passage 2. Accordingly, the second embodiment can obtain the same effects 
as the first embodiment. 
Note, in the first embodiment, if a degree of stiffness of the reed valves 
1f is too low, a part of intake air in the low engine speed and low engine 
load driving condition I is supplied via the reed valves 1f without 
passing through the sub intake passage 5, whereby the intended swirl 
becomes weak, and if the degree of stiffness is too high, the reed valves 
1f provide a considerable resistance to intake air in the low engine speed 
and high engine load driving condition II, whereby the required amount of 
intake air cannot be supplied to the combustion chamber 20. Accordingly, 
the degree of stiffness of the reed valves 1f must be very carefully 
selected. 
Nevertheless, according to the second embodiment, in the low engine speed 
and low engine load driving condition, all of the intake air, containing a 
part of intake air passed via the reed valves 1'f, passes only through the 
sub intake passage 5 and is supplied to the combustion chamber 20, due to 
the closing of the main intake passage 2 downstream of the merging point 
of the reed valve passage 4, and accordingly, the degree of stiffness of 
the reed valves 1'f may be relatively low, and thus the selection of the 
reed valves 1'f is simplified. 
FIG. 5 shows a third embodiment; here only the difference between the third 
and second embodiments is explained, as follows. 
The intake air control device of the third embodiment comprises first and 
second control valves 7 and 8, and two step motors 9 and 10 for driving 
the valves 7 and 8, respectively. These step motors 9 and 10 are connected 
to an output port 56 of an ECU 50' via corresponding drive circuits 57 and 
58, and are controlled by the ECU 50'. The first control valve 7 closes 
the main intake passage 2 in the first pivoted position of the control 
valve 3' used in the second embodiment, and the second control valve 8 
closes the main intake passage 2 in the second pivoted position of the 
control valve 3'. Accordingly, the first control valve 7 serves as the 
third closing means explained in the second embodiment, and the second 
control valve 8 serves as the second closing means explained in the second 
embodiment, whereby the third embodiment can obtain the same effects as 
the second embodiment. 
Note, in the low engine speed and low engine load driving condition I which 
includes an idling condition, if a back flow of exhaust gases occurs, by 
which the intake and exhaust valves are opened simultaneously at the end 
of exhaust stroke, the combustion becomes unstable. 
According to the third embodiment, when in this driving condition I, the 
first control valve 7 closes the main intake passage 2 between the 
branched point and the merging point of the sub intake passage 5, and 
downstream of the merging point of the reed valve passage 4, as the third 
closing means, and at the same time the second control valve 8 closes the 
main intake passage 2 between the branched point and the merging point of 
the reed valve passage 4, and upstream of the branched point of the sub 
intake passage 5, as a fourth closing means, whereby all of the intake air 
passes from the passage 4, via the reed valves 1"f, to the sub intake 
passage 5 and is supplied to the combustion chamber 20, so that a more 
stable combustion can be obtained by the creating of a swirl, and further, 
to prevent a back flow of exhaust gases by the reed valves 1"f and the 
second control valve 8. 
FIGS. 6(A) and 6(B) show a modification of the third embodiment, when an 
intake air control device is used in a engine having two intake valves. As 
shown in FIG. 6(B), a main intake passage 2 is divided into two passages 
downstream of the first control valve 7, and intake air is fed to the 
combustion chamber 20 via two intake valves 21a and 21b. A sub intake 
passage 5 leads to the main intake passage 2 at a point close to the 
intake valve 21a. 
A fuel injector 60 has two injection holes for injecting fuel toward the 
two intake valves 21a and 22a, respectively, and accordingly, the amount 
of fuel to be injected can be divided into two, and thus an atomization 
thereof can be accelerated when the fuel collides with the back side of 
the intake valves 21a and 21b. 
If the injector 60 is arranged downstream of the first control valve 7, as 
shown in the third embodiment, a desired ratio of the air-fuel mixture in 
the combustion chamber 20 cannot be obtained in the low engine speed and 
low engine load driving condition, because the intake air in this driving 
condition passes only through the sub intake passage 5 and is supplied 
only via the intake valve 21a and there is less intake air flowing to the 
combustion chamber 20 via the other intake valve 21b, and thus an amount 
of fuel injected toward the another intake valve 21b is atomized but this 
atomized fuel does not easily flow in the combustion chamber 20. 
In this modification, the injector 60 is arranged between the first control 
valve 7 and second control valve 8, and accordingly, the fuel injected 
under driving conditions other than the low engine speed and low engine 
load driving condition I is atomized by an impact thereof with the two 
intake valves 21a and 21b, respectively, and flows in the combustion 
chamber 20 together with the intake air, and the fuel in the low engine 
speed and low engine load driving condition I is atomized and collides 
with the first control valve 7, which is closed in this driving condition, 
and becomes a mixture having a desired air/fuel ratio before the intake 
air passes through the sub intake passage 5. Accordingly, a desired ratio 
of the mixture can be always obtained in the low engine speed and low 
engine load driving condition I. 
FIG. 7 shows a fourth embodiment; here only the difference between the 
fourth and second embodiments is explained, as follows. 
A reed valve assembly 100 consists of an outside member 100A similar to the 
reed valve assembly 1' in the second embodiment and an inside member 100B 
joined telescopically to the outside member 100A. A control valve 11 is 
arranged at a part farthest downstream of an inside space 2d of the inside 
member 100B biased toward a downstream direction by a spring 12 with 
respect to the outside member 100A. The control valve 11 can pivot about a 
shaft 11a freely only in a anticlockwise direction in FIG. 7(A), and thus 
is suitably chamfered. 
A arm 13 mounted at a drive shaft 13a is arranged downstream of the control 
valve 11, and an end of the arm 13 bears against the control valve 11 at a 
point higher than the drive shaft 13a on FIG. 7(A). The drive shaft 13a is 
connected to a step motor 14 controlled by a ECU (not shown), such as the 
ECU 100 of the first embodiment. 
In the fourth embodiment, in the low engine speed and low engine load 
driving condition I, which includes the idling condition, the arm 13 is 
pivoted to a first pivoted position as shown in FIG. 6(A), and accordingly 
the control valve 11 serves as sixth closing means for closing the main 
intake passage 2 consisting of the inside spaces 2a and 2d of the reed 
valve assembly 100, the upstream space 2b and the downstream space 2c, 
between the branched point of the reed valve passage 4 and the merging 
point of the sub intake passage 5, and at the same time, the inside member 
100B serves as fifth closing means for blocking the merging point of the 
reed valve passage 4 and the branched point of the sub intake passage 5 
from the main intake passage 2 under a condition in which the reed valve 
passage 4 is communicated with the sub intake passage 5. Accordingly, all 
of the intake air passes from the reed valve passage 4, via the reed 
valves 100f, to the sub intake passage 5 and is supplied to the combustion 
chamber 20, and thus the same effects as in the third embodiment can be 
obtained. 
In the low engine speed and high engine load driving condition II, the arm 
13 is pivoted in a clockwise direction to a second pivoted position, as 
shown in FIG. 7(B), so that the control valve 11 still closes the inside 
space 2d and the inside member 100B is slid in a upstream direction 
against the spring 12, and accordingly the merging point of the reed valve 
passage 4 is communicated with the downstream space 2c of the main intake 
passage 2. 
At this time, the control valve 11 serves as the second closing means 
explained in the first embodiment, so that intake air is passed, via the 
reed valves 100f, through the main intake passage 2 and is supplied to the 
combustion chamber 20, whereby a higher torque can be obtained to thus 
increase the charging efficiency, as in the above-mentioned embodiments. 
In the high speed driving condition, the arm 13 is pivoted in a 
anti-clockwise direction to a third pivoted position, as shown in FIG. 
7(C), so that the end of the arm 13 is separated from the control valve 
11, and accordingly, the control valve 11 is opened by the force of the 
intake air, and thus the main intake passage 2 is opened and the intake 
air passes therethrough, to thereby ensure a sufficient supply thereof as 
in the above embodiments. 
Thus, the fourth embodiment can obtain the same effects as those of the 
third embodiment, and the manufacturing costs thereof can be reduced 
because only the step motor 14 for driving the arm 13 is used, in contrast 
to the third embodiment used the two step motors 9 and 10. 
Next, in the third embodiment, a case in which the search at step S3 of the 
flow chart shown in FIG. 2 is carried out by using a second engine 
speed-load map as shown in FIG. 8, and then the actuating at step S4 is 
carried out in accordance with a table shown in FIG. 8, is explained. In 
this map, the low engine speed and high engine load driving condition II 
in the first map shown in FIG. 3 is divided into low engine speed and 
middle engine load driving conditions IIa, IIb, and low engine speed and 
high engine load driving condition IIc corresponding to a required amount 
of intake air. 
Note, when the reed valves 1"f prevent a back flow of the intake air, a 
piston must exert a greater compression force, until the intake valve 21 
is closed, from a bottom dead center of a compressing stroke thereof. This 
greater compressing force is increased when the timing of the intake valve 
21 is retarded. 
When in the low engine speed and middle engine load driving condition IIa, 
IIb, even if a back flow of the exhaust gases occurs, the combustion 
remains relatively stable and a higher torque is not required. 
Accordingly, at step S4, the first and second control valve 6 and 7 are 
opened in these driving conditions similar to the high engine speed 
driving condition III, to thereby reduce the fuel consumption because the 
greater compression force by the piston is not required. 
In the other driving conditions I, IIc, III, the first and second control 
valves 6 and 7 are in the same open or closed condition as mentioned 
above. 
Further, when in the low engine speed and middle engine load driving 
condition IIa, in which a relatively small amount of intake air is 
required, the first control valve 6 is partly opened, corresponding to the 
required amount of intake air, and the second control valve 7 is fully 
opened so that a part of the required amount of intake air passes through 
the main intake passage 2 and the remainder of the required amount of 
intake air passes through the sub intake passage 5. 
Accordingly, a swirl is also created in the combustion chamber 20 at this 
time, whereby the fuel consumption is reduced and a good combustion is 
obtained, due to the swirl. 
In all of the above embodiments, that the main intake passage 2 can be 
opened in the low engine speed and middle engine load driving condition 
IIa, IIb, as in the high engine speed driving condition III, whereby the 
fuel consumption at this time can be reduced. 
In the first embodiment, the control valve 3 can be pivoted in a clockwise 
direction, corresponding to the required amount of intake air, from the 
first pivoted position, and in the second embodiment, the control valve 3' 
can be pivoted in an anti-clockwise direction, corresponding to the 
required amount of intake air, from the first pivoting position. 
Accordingly, in the first and second embodiments, the main intake passage 2 
can be partly opened downstream of the branched point of the sub intake 
passage 5 and fully opened upstream of the control valve 3 or 3', in the 
low engine speed and middle engine load driving condition IIa in which a 
relatively small amount of intake air is required, whereby the fuel 
consumption at this time can be reduced and a good combustion can be 
obtained due to the swirl. 
According to the present invention, in the low engine speed and low engine 
load driving condition, a stable combustion is obtained as usual, and in 
the low engine speed and high engine load condition, the charging 
efficiency is increased to allow the required amount of intake air to be 
supplied via the reed valves to thereby obtain a higher torque as usual, 
and in the high engine speed driving condition, a large required amount of 
intake air can be supplied through the main intake passage 2 without 
passing through the reed valves, to ensure a sufficient supply thereof. 
Further, in the low engine speed and middle engine load driving condition, 
the intake air is supplied without passing through the reed valves, and 
accordingly, the fuel consumption at this time is reduced because the 
greater compressing force of the piston is not required. 
Furthermore, when the required amount of intake air is relatively small in 
the low engine speed and middle engine load driving condition, a swirl can 
be created in the combustion chamber, and accordingly, a good combustion 
can be obtained at this time. 
Although the invention has been described with reference to specific 
embodiments thereof, it should be apparent that numerous modifications can 
be made thereto by those skilled in the art, without departing from the 
basic concept and scope of the invention.