U.S. patent application number 09/820859 was filed with the patent office on 2001-10-11 for air induction system for engine.
Invention is credited to Itou, Atsushi.
Application Number | 20010027767 09/820859 |
Document ID | / |
Family ID | 18612333 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010027767 |
Kind Code |
A1 |
Itou, Atsushi |
October 11, 2001 |
Air induction system for engine
Abstract
A air induction system actuates two variable mechanisms by the
resonant supercharging and a volume variable mechanism of the air
induction system by a common drive means in order to reduce the
manufacturing cost and to improve the output performance in the
broader range of the engine speed. The air induction system
includes a plurality of independent air intake passages for
supplying the induction air to each engine cylinder which are
sorted into two air intake passage groups, an air expanding chamber
being in communication with the air intake passage groups, a first
switching valve for controlling the communication between the air
expanding chamber, two branch passages for supplying the induction
air into the air expanding chambers, a volumetric chamber, and a
second switching valve for controlling the communication between
the volumetric chamber and the branch passages, an actuator for
driving the first and second switching valves. The first and second
switching valves are controlled to be opened and closed in
accordance with the engine speed range.
Inventors: |
Itou, Atsushi; (Aichi-ken,
JP) |
Correspondence
Address: |
Platon N. Mandros, Esq.
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
18612333 |
Appl. No.: |
09/820859 |
Filed: |
March 30, 2001 |
Current U.S.
Class: |
123/184.38 ;
123/184.57 |
Current CPC
Class: |
F02B 27/0252 20130101;
Y02T 10/12 20130101; F02B 27/021 20130101; Y02T 10/146 20130101;
F02B 27/0284 20130101; F02B 27/0242 20130101 |
Class at
Publication: |
123/184.38 ;
123/184.57 |
International
Class: |
F02M 035/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2000 |
JP |
2000-097756 |
Claims
What is claimed is:
1. An air induction system for a multi-cylinder engine, comprising:
a plurality of independent air intake passages in communication
with respective cylinders of the engine for supplying induction air
thereto; a surge tank connected to the independent air intake
passages for supplying the induction air to the air intake
passages; an air induction passage having first and second branch
passages each exposed to the atmosphere at one end thereof and
connected to the surge tank at another end thereof for inducing the
induction air into the surge tank; a volumetric chamber disposed
between the branch passages; a first switching valve disposed in
the surge tank for selectively interrupting and establishing fluid
communication between first and second sections the surge tank; a
second switching valve separating the volumetric chamber from the
first and second branch passages for selectively interrupting and
establishing fluid communication between the volumetric chamber and
the first and second branch passages; and a drive mechanism common
to the first and second switching valves for operating the first
and second switching valves in response to the magnitude of engine
speed.
2. The air induction system according to claim 1, wherein the
second switching valve comprises a hollow cylindrical member having
openings provided in a cylindrical surface thereof, and wherein the
volumetric chamber is formed in the hollow portion of the
cylindrical member.
3. The air induction system according to claim 2, wherein the
second switching valve is rotatable about a longitudinal axis of
the cylindrical member.
4. The air induction system according to claim 1, wherein the
independent air intake passages are grouped into two groups, the
intake order of which is not continuous and wherein each section of
the surge tank is arranged to be fluidly connected to a respective
group of the intake passages, in response to the first switching
valve being operated to divide the surge tank into the
sections.
5. The air induction system according to claim 1, wherein the drive
mechanism includes an actuator, and further comprising: a first
shaft formed on the first switching valve and connected to the
actuator; a second shaft formed on the second switching valve; a
transmitting portion provided between the first shaft and the
second shaft for transmitting rotational force from the actuator
while providing phase-contrast between the first shaft and the
second shaft; a biasing means for providing a biasing force
opposing the rotational force provided to the second switching
valve by the actuator; and a stopper for preventing the second
switching valve from rotating beyond a predetermined angle; wherein
the first and second switching valves have respective different
opening and closing periods.
6. The air induction system according to claim 1, wherein the surge
tank and the air induction passage form a first air expanding
chamber for enlarging the volume of the air induction system in
accordance with the engine speed.
7. The air induction system according to claim 1, wherein the air
induction passage and the volumetric chamber form a second air
expanding chamber for enlarging the volume of the air induction
system in accordance with the engine speed.
8. The air induction system according to claim 1, wherein the surge
tank, the air induction passage, and the volumetric chamber form a
third air expanding chamber for enlarging the volume of the air
induction system in accordance with the engine speed.
Description
RELATED INVENTION
[0001] This application is based on and claims priority under 35
U.S.C..sctn. 119 with respect to Japanese Application No.
2000-097756 filed on Mar. 31, 2000, the entire content of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to air induction
systems. More particularly, the present invention pertains to an
air induction system having a variable air induction mechanism
varying characteristics of the air induction system and a variable
volumetric mechanism in order to obtain the dynamic effects of the
induction air.
[0004] 2. Background of the Related Arts
[0005] Conventionally known air induction systems supercharge the
induction air, improve the charging efficiency to fill the engine
combustion chamber with the induction air, and improve the output
performance of the engine by utilizing dynamic effects of the
induction air supplied to the combustion chamber of the engine.
Generally, the dynamic effects of the induction air utilized in the
air induction system of the engine includes the inertia effect and
the resonance effect. Supercharging effects due to the inertia
effect and the resonance effect can be obtained when the engine rpm
and the natural frequency of the air induction system are
synchronized. The natural frequency is determined by the length and
the sectional area of the air intake passage, and the average
volume during the air intake period. It is known that the engine
rpm and the natural frequency of the air intake system are
synchronized by reducing the sectional area of the air intake
passage and by expanding the length of the air intake passage at
lower engine speed range. The engine rpm and the natural frequency
of the air intake system are also synchronized by enlarging the
sectional area of the air intake passage and by shortening the
length of the air intake passage at higher engine speed.
Accordingly, in general, the range of the engine rpm for obtaining
the supercharging effects by the dynamic effects of the induction
air is broadened by air induction systems provided with mechanisms
varying the length of the air intake passage and the volume of
plenum.
[0006] Japanese Patent Laid-Open Publication No. S60-169627
discloses a variable air induction system utilizing the foregoing
effects. The air induction system according to the aforementioned
prior art includes an air intake passage having two branch passages
diverged at a predetermined diverging portion, an air expanding
chamber provided on the downstream side of the branch passages, and
a plurality of independent air intake passages for respective
cylinders whose order of air induction does not overlap one
another. The air induction system according to the aforementioned
prior art further includes a first bypass for communicating two air
expanding chambers, and a second bypass for communicating two
branch passages at a position between the diverging portion and the
air expanding chamber. The air induction system according to the
aforementioned prior art further includes first and second
switching valves for opening and closing the first and second
bypasses respectively in accordance with the rpm of the engine.
Thus, the air induction system according to the aforementioned
prior art is capable of changing the frequency by which the inertia
effects and the resonance effects can be obtained by varying the
volume of the air expanding chamber and the length of the air
intake passage by controlling the opening and closing of the first
and second switching valves provided in the branch passages and the
air expanding chamber in accordance with the engine rpm.
[0007] It is also known that the output performance of the engine
at higher speed ranges is improved by expanding the volume of the
plenum downstream of the throttle valve provided on the air
induction system of the engine. When the engine revolves at high
speed, the amount of the induction air required in the combustion
chamber is increased. This brings the necessity to supply the
induction air in a larger amount than the volume of the air
induction system of the engine. As a result, the induction air is
introduced from an end of the air induction system exposed to the
atmosphere. In a four-cycle engine, for instance, pistons are
descended during the intake stroke period and the pistons work in
order to intake the induction air to the combustion chamber. Since
the induction air is introduced from the end of the air induction
system exposed to the atmosphere, the induction air enters a
complicatedly structured air induction system structured in order
to obtain the inertia effect and the resonant effect. This causes a
very large resistance to the induction air. In this case, the work
by the pistons is reduced in accordance with the resistance caused
by the flow of the induction air and not all work of the pistons is
used for intaking the induction air (that is called pumping
losses). That is, the power of the pistons is declined. Provided
that the volume of the air induction system can be enlarged when
the engine is at the high rpm range, the necessary volume of the
induction air for combustion can be supplied to the combustion
chamber from the air induction system (not from the end of the air
induction system exposed to the atmosphere). Thus, the work of
piston in order to intake the induction air to the engine can be
reduced to supply the larger amount of the induction air to the
combustion chamber and to improve the output performance of the
engine.
[0008] In the aforementioned prior art, the use of a plurality of
switching valves is necessary in order to control the communication
of the air intake passages and a plurality of the drive means, and
control means are necessary for operating the switching valves.
Hence, the number of members comprising the switching valve and the
drive means is increased as well as the assembling time due to a
complicated structure, which increases the manufacturing cost. In
addition, it is difficult to arrange all members in a limited space
of the engine compartment.
[0009] In the aforementioned prior art, the volume of the air
induction system cannot be expanded. When the volume of the air
induction system downstream of the throttle valve is expanded,
another problem arises, i.e., the delay of the response of engine
at lower and middle engine speed range. The output of the engine is
variably controlled in accordance with the amount of the induction
air introduced into the air intake passages by the increase and
decrease of the sectional area of the air intake passages caused by
the opening and closing of the throttle valve operated in
accordance with the operation of throttle pedal. Since the
induction air increased by the opening of the throttle valve is
first supplied to the combustion chamber of the engine after
fulfilling the volume of the air induction system downstream of the
throttle valve when the volume of the air intake passage at the
downstream of the throttle valve is large, a lag between the
operation of the throttle pedal by the vehicle driver and the
increase of the engine output is created. The lag makes the driver
feel that the engine response is slow.
[0010] According to the aforementioned reason, it is favorable that
the volume of the air intake passage be increased only at the
higher speed range of the engine. However, in order to achieve this
goal, another pair of air expanding chambers, switching valves,
drive means, and control means are necessary to be provided to the
air induction system. The air induction system would also need to
have a structure capable of controlling the communication between
the air induction system and the additional air expanding chamber.
Since the structure according to the foregoing condition is further
complicated compared to the aforementioned prior art, it is
difficult to achieve the goal.
SUMMARY OF THE INVENTION
[0011] In light of the foregoing, it is an object of the present
invention to provide an air induction system which is capable of
improving the performance at broader range of engine speed with low
manufacturing cost and simple structure.
[0012] To attain the above object, the following technical means is
provided with the air induction system of the present invention
which includes a plurality of independent air intake passages in
communication with respective cylinders of the engine for supplying
air thereto, a surge tank connected to the independent air intake
passages for supplying the induction air to the air intake
passages, an air induction passage having first and second branch
passages each exposed to the atmosphere at one end and connected to
the surge tank at another end for introducing the induction air
into the surge tank, and a volumetric chamber disposed between the
branch passages. The air induction system further includes a first
switching valve disposed in the surge tank for selectively
interrupting and establishing fluid communication between first and
second sections of the surge tank, and a second switching valve
separating the volumetric chamber from the first and second branch
passages for selectively interrupting and establishing fluid
communication between the volumetric chamber and the first and
second branch passages. The first and second switching valves being
operated by a common drive mechanism in accordance with the
magnitude of the engine speed.
[0013] According to the foregoing technical means, by providing the
volumetric chamber between the branch passages, the volume of the
air induction system can be varied to improve the output
performance of the engine at the higher speed range. Further, by
the function of the second switching valve for controlling the
communication between the branch passages and the volumetric
chamber, the volumetric chamber can be used only when the expansion
of the volume of the air intake passage is necessary at a higher
engine speed range and not used when the engine response is delayed
by the expanded volume of the air intake passages such as at a
lower and a middle engine speed range. Accordingly, both the
improvement of the engine output performance and an assurance of
good response can be achieved. Further more, since the first and
the second switching valves can be operated by a common drive
means, the number of the switching valves can be increased without
increasing the number of drive means and control means. Thus, the
manufacturing cost can be reduced and a simple structure can be
achieved.
[0014] It is favorable that the second switching valve comprises a
rotary switching valve formed with two openings in a hollow
cylinder and the hollow portion of the rotary switching valve forms
the volumetric chamber.
[0015] It is further favorable that a first shaft is formed on the
first switching valve and is connected to the drive means, a second
shaft is formed on the second switching valve, and a transmitting
portion is provided between the first and the second shafts for
transmitting the rotation force of the drive means while providing
phase-contrast between the first and the second shafts. A biasing
means opposes the rotational force provided to the second switching
valve by the drive means, and a stopper blocks the rotation of the
second switching valve from exceeding a predetermined angle of
movement. It is favorable that the air induction system of the
present invention is structured to have different periods for
opening and closing the first and the second switching valves.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0016] The foregoing and additional features and characteristics of
the present invention will become more apparent from the following
detailed description considered with reference to the accompanying
drawing figures in which like reference numerals designate like
elements and wherein:
[0017] FIG. 1 is a perspective view of an air induction system of
an engine of the embodiment according to the present invention:
[0018] FIG. 2 is a perspective view of a second switching valve of
the embodiment according to the present invention:
[0019] FIG. 3 is a perspective view of a first switching valve of
the embodiment according to the present invention;
[0020] FIG. 4 is a cross sectional view of the air induction system
of the embodiment according to the present invention;
[0021] FIG. 5 is a cross sectional view showing a first switching
mode of the second switching valve of the embodiment according to
the present invention;
[0022] FIG. 6 is a cross sectional view of a second switching mode
of the second switching valve of the embodiment according to the
present invention;
[0023] FIG. 7 is a cross sectional view of a third switching mode
of the second switching valve of the embodiment according to the
present invention;
[0024] FIG. 8 is a cross sectional view showing first through
fourth switching modes of the first switching valve of the
embodiment according to the present invention:
[0025] FIG. 9 is a cross sectional view showing a first operation
position of a transmitting portion of the embodiment according to
the present invention;
[0026] FIG. 10 is a cross sectional view showing a second operation
position of the transmitting portion of the embodiment according to
the present invention;
[0027] FIG. 11 is a cross sectional view showing a third operation
position of the transmitting portion of the embodiment according to
the present invention;
[0028] FIG. 12 is a cross sectional view showing a fourth operation
position of the transmitting portion of the embodiment according to
the present invention;
[0029] FIG. 13 is a schematic view of the air induction system of
which the first and second switching valves are controlled in order
to have characteristics during lower engine speed range;
[0030] FIG. 14 is a schematic view of the air induction system of
which the first and second switching valves are controlled to have
characteristics during mid-low engine speed range;
[0031] FIG. 15 is a schematic view of the air induction system of
which the first and second switching valves are controlled to have
characteristics during mid-high engine speed range;
[0032] FIG. 16 is a schematic view of the air induction system of
which the first and second switching valves are controlled to have
characteristics during higher engine speed range; and
[0033] FIG. 17 is a schematic graph showing the relationship
between the characteristics of the engine torque and the engine rpm
according to the air induction system of the embodiment according
to the present invention,
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0034] An embodiment of the present invention of the air induction
system will be explained referring to FIGS. 1 through 17.
[0035] Referring to FIG. 1, a throttle body 2 for controlling the
amount of the induction air flowing in an air induction system 10
is mounted on the most upstream portion of the air induction
system. Branch passages 16a, 16b dividing an air intake passage
into two passages are provided downstream of the throttle body 2.
The first and second branch passages 16a, 16b are in communication
with a surge tank 14 functioning as an air expanding chamber. A
plurality of independent air intake passages 12 for supplying the
induction air to a combustion chamber of respective cylinders (not
shown) of the engine 1 are connected to the surge tank 14. A
control valve unit 15 is provided which a includes hollow
cylindrical housing 15e with a bottom at one end and which further
includes a first switching valve 20 and a second switching valve 30
disposed in the housing. The control valve unit 15 is formed on the
surge tank 14 and extends into a space disposed between the first
branch passage 16a and the second branch passage 16b in a direction
perpendicular to the longitudinal direction of the surge tank 14.
An opening 15c of the housing 15e is provided in a flange portion
15d formed on the peripheral surface of the surge tank 14, the
opening 15c receiving an actuator (driving means) 3 (shown in FIG.
4). After the first and second switching valves 20, 30 are arranged
in respective predetermined positions in the control valve unit,
the actuator 3 is then fixed to the flange portion 15d.
[0036] FIG. 2 shows a perspective view of the first switching valve
20 of the embodiment of the present invention.
[0037] As shown in FIG. 2, the first switching valve 20 includes a
first and a second disc member 21, 22 positioned in parallel
maintaining a predetermined distance, and a rectangular valve
portion 23 therebetween. The width of the rectangular valve portion
23 is equal to the distance between the first and the second disc
members 21, 22 and the length thereof is equal to the diameter of
the first and the second disc members 21, 22. A first shaft 24
projects from the first disc member 21 and is connected to the
actuator 3. The second disc member 22 is provided with a first
transmitting shaft 25. The first transmitting shaft 25 includes a
cylindrical shaft portion 25a and a lug 26 projecting in a radial
outward direction. The second disc member 22 is provided with a
seal member 33 on the circumferential surface. The seal member 33
maintains an airtightness of the first switching valve 20 by
contacting the interior surface of the housing 15e when the first
switching valve 20 is inserted into the housing 15e.
[0038] FIG. 3 is a perspective view of the second switching valve
30 of the embodiment of the present invention.
[0039] As shown in FIG. 3, the second switching valve 30 includes a
cylinder 30a having a pair of openings 32 arranged in a
circumferential surface 31 symmetrically relative to a central axis
of the cylinder. The cylinder 30a has a hollow cylindrical shape
with bottoms at both ends. A second transmitting shaft 36 projects
from a bottom surface portion 34 which is adjacent to the first
switching valve 20 (shown in FIG. 2) and opposing the first
transmitting shaft 25 (shown in FIG. 2). As shown in FIG. 3, the
second transmitting shaft 36 having an incomplete cylindrical shape
forms a contacting portion 37 on the circumferential end surface.
The contacting portion 37 transmits rotational force by contacting
the convex portion of the first transmitting shaft 25 (shown in
FIG. 2). A second shaft 38 of the switching valve 30 is inserted
into a bearing 15b (shown in FIG. 4) of the control valve housing
15e for rotatably supporting the second switching valve 30. A
stopper 39 is provided on the bottom of the switching valve 30 for
preventing rotation of the second switching valve 30 by contacting
a stopper supporting portion 15a (shown in FIG. 4) provided on the
bottom portion of the control valve housing 15e. The second
switching valve 30 is provided with a return spring (biasing means)
4 for providing a biasing force opposing the rotational direction
to the second switching valve 30 when the second switching valve 30
is rotated by the actuator 3, for example a motor.
[0040] The circumferential surface 31 of the second switching valve
30 is provided with another seal member 33 for sealing the second
switching valve 30 by contacting the interior peripheral surface of
the control valve housing 15e.
[0041] FIG. 4 is a sectional view of the air induction system of
the embodiment of the present invention shown in FIG. 1.
[0042] Referring to FIG. 4, communication between the first and
second branch passages 16a and 16b and the control valve unit 15
disposed therebetween is established by a communication portion 17.
The communication between the control valve unit 15 and the first
and second branch passages 16a, 16b is established by keeping the
position of the opening portions 32 aligned with the opening of the
communication portion 17 by rotating the second switching valve 30
driven by the actuator 3.
[0043] The control valve unit 15 is also in communication with the
surge tank 14. The first switching valve 20 is provided at a
location where the control valve unit 15 and the surge tank 14 are
in communication. The first switching valve 20 is rotated by the
actuator 3 selectively to a position where the surge tank 14
functions as a single air expanding chamber, and a position where
the surge tank 14 functions as first and second air intake
passages.
[0044] The stopper supporting portion 15a projecting from the
bottom of the control valve housing 15e prevents a further rotation
of the second switching valve 30 by contacting the stopper 39 of
the second switching valve 30 when the second switching valve 30 is
rotated to a predetermined angle. The bearing 15b is formed on the
bottom of the control valve housing 15e and receives the second
shaft 38 of the second switching valve 30. The first shaft 24 of
the first switching valve 20 is connected to the actuator 3. The
first switching valve 20 and the second switching valve 30 are
connected via the first transmitting shaft 25 and the second
transmitting shaft 36 for transmitting the rotational force of the
actuator 3. The first switching valve 20 and the second switching
valve 30 are rotatably supported by the actuator 3 and the bearing
15b.
[0045] The seal members 33 provided on the disc members 21, 22 of
the first switching valve 20 and on the bottom portion 34 of the
second switching valve 30 blocks communication between the surge
tank 14 and the branch passages 16a, 16b via the control valve unit
15 by contacting the interior circumferential surface of the
control valve housing 15e.
[0046] FIGS. 5-7 are sectional views of the attaching portion of
the second switching valve of the embodiment of the present
invention. FIG. 5 shows a first switching position, FIG. 6 shows a
second switching position, and FIG. 7 shows a third switching
position of the second switching valve 30.
[0047] Referring to FIGS. 5-7, the communication portion 17 and the
second switching valve 30 are provided between the first branch
passage 16a and the second branch passage 16b. The cylinder 30a of
the second switching valve 30 includes an inner chamber 40,
hereinafter referred to as a volumetric chamber. When the two
openings 32 formed in the second switching valve 30 become aligned
with the communication portion 17 upon rotation of the second
switching valve 30 by the actuator 3, a further air expanding
chamber is defined by the volumetric chamber 40 due to the
communication established between the first branch passage 16a and
the second branch passage 16b (via the volumetric chamber 40 and
the communication portion 17). Thus, the volume of the air intake
system is increased by an amount equal to the volume of the
volumetric chamber 40. Each of the openings 32 has an arc shape
(see FIG. 5) whose angular length corresponds to a central angle A.
The openings 32 are spaced apart by a portion of the
circumferential surface 31 having another arc shape whose angular
length corresponds to a central angle B. It is favorable that
A=120.degree. and B=60.degree..
[0048] The second switching valve 30 is maintained at a first
(closed) switching position (position K) in FIG. 5. The first
switching position corresponds to the initial attaching position
when no rotational force is applied by the actuator 3.
[0049] Referring to FIG. 5, since the openings 32 of the second
switching valve 30 are maintained at a position non-aligned with
the communication portion 17, the communication portion 17 is
closed by the circumferential surface 31 of the second switching
valve 30. Consequently, the branch passage 16a and the branch
passage 16b function as independent passages respectively.
[0050] Referring to FIG. 6, the second switching valve 30 is
maintained at a second (open) switching position (position L) after
being rotated by angle B from the position K of FIG. 5 by the
actuator 3. The openings 32 and the communication portion 17 are
maintained in alignment with each other to establish communication
between the first branch passage 16a and the second branch passage
16b via the volumetric chamber 40 and the communication portion
17.
[0051] The second switching valve 30 is maintained at a third
(open) switching position (position M) after being rotated by the
angle B from the L position by the actuator 3 in FIG. 7. When the
second switching valve 30 is rotated by the actuator 3, the
openings 32 is rotated. However, since the openings 32 are still
maintained at a position aligned with the communication portion 17,
the communication between the first and the second branch passages
is maintained via the volumetric chamber 40.
[0052] FIG. 8 is a sectional view of the attaching portion of the
first switching valve 20 of the embodiment of the present
invention. Position F corresponds to a first switching position,
position G corresponds to a second switching position, position H
corresponds to a third switching position, and position J
corresponds to a fourth switching position of the first switching
valve.
[0053] As shown in FIG. 8, the surge tank 14 is provided with the
control valve unit 15. The first switching valve 20 is disposed in
the control valve housing 15e. The first switching valve 20 is
rotated by the actuator 3 to a position where the surge tank 14
functions as first and second air intake passages, or to a position
where the surge tank 14 functions as a single air expanding
chamber. When the surge tank 14 functions as two air intake
passages, the independent air intake passages 12 are divided into
two cylinder groups which do not have their intake periods
overlapping.
[0054] The first switching position F of FIG. 8 (solid lines)
corresponds to the initial attaching position of the first
switching valve 20 (before the rotational force of the actuator 3
is transmitted). The valve portion 23 is maintained in a state
(opening condition) where the communication of the surge tank 14 in
the control valve unit 15 is not disturbed, to enable the surge
tank 14 to function as a single air expanding chamber. Position G
corresponds to the second switching position after the valve
portion 23 has been rotated by the angle B from the F position by
the actuator 3. At the second switching position G, since the valve
portion 23 interrupts the communication between two separate
portions 14a, 14b of the surge tank 14 (closed condition), the
surge tank 14 is divided into two chambers functioning as first and
second air intake passages, respectively. Position H corresponding
to the third switching position shows the condition after the valve
portion 23 of the surge tank 14 has been rotated by the angle B
from the position G by the rotational force of the actuator 3.
Since the valve portion 23 is in a closed condition, the surge tank
14 is divided into two chambers as mentioned above. Position J
corresponding to the fourth switching position occurs after the
valve portion 23 has been rotated by the angle B from the position
H. As shown in FIG. 8, the valve portion 23 is placed in the same
position as the initial attaching position (the first switching
position) shown as the position F because now the portion 23 will
have been rotated by 180 degree from the first switching position.
At the fourth switching position, the valve 23 is maintained in an
open condition to establish a communication between the surge tank
portions 14a, 14b to make the surge tank function as a single air
expanding chamber.
[0055] FIGS. 9-12 show a sectional view of the first transmitting
shaft 25 and the second transmitting shaft 36 of the embodiment of
the present invention and the respective operation conditions when
the first transmitting shaft 25 is rotated by the actuator 3.
[0056] FIG. 9 shows the condition that the first transmitting shaft
25 and the second transmitting shaft 36 are located at respective
initial attaching positions, i.e., position P and position Q,
respectively. The second transmitting shaft 36 has a hollow
cylindrical shape in which there is formed a recess of an angular
length A. The second transmitting shaft 36 telescopingly receives
the shaft portion 25a of the first transmitting shaft 25, which
portion 25a has a smaller outside diameter than the inside diameter
of the hollow cylinder of the second transmitting shaft 36. The lug
26 provided on the first transmitting shaft 25 is spaced from the
contacting portion 37 of the recess by angle B when the lug 26 is
at the midpoint of the recess. As noted earlier, it is favorable if
the angle A is 120.degree. and the angle B is 60.degree..
[0057] FIG. 10 shows the condition that the first transmitting
shaft 25 and the lug 26 are rotated by the angle B to the second
operation position (the position Q). The lug 26 contacts the
contacting portion 37 of the recess portion of the second
transmitting shaft 36. The actuator 3 only rotates the shaft 25 by
angle B, so the shaft 36 is not caused to rotate. Accordingly, the
second transmitting shaft 36 is maintained at the initial attaching
position (position Q).
[0058] FIG. 11 shows the condition that the first transmitting
shaft 25 and the lug 26 are rotated by a further angle B to be
moved to the third operation position (position R) by the actuator
3. The lug 26 contacts the contacting portion 37 of the second
transmitting shaft 36 to rotate the second transmitting shaft 36 by
the angle B.
[0059] In FIG. 12, the shaft 25 and lug 26 have been rotated by an
additional angle B, thereby also rotating the shaft 36 by an
additional angle B, to position S.
[0060] FIGS. 13-16 are schematic views of the air induction system
of the embodiment of the present invention showing the condition of
the first and the second switching valves 20, 30 and the
characteristic relationship of the air induction system.
[0061] In FIG. 13, the first switching valve 20 and the second
switching valve 30 are positioned at the first switching position
corresponding to the initial attaching position, i.e., a closed
position K for valve 30, and an open position F for valve 20. In
consequence, the air induction system has a first natural frequency
formed by the branch passages 16a, 16b, the surge tank 14
(functioning as the single air expanding chamber), and the
independent air intake passages 12. FIG. 14 shows the condition
that the first switching valve 20 is at the second switching
position G, the second switching valve 30 is still at the first
switching position K, and thus both of the first and second
switching valves 20, 30 are closed. According to this condition,
the independent air intake passages 12 are divided into two groups
in which the intake stroke of each passage keeps equal interval and
the intake strokes of the independent air intake passages 12 do not
overlap one another. As the result, the air induction system has a
second natural frequency. FIG. 15 shows the condition that the
first switching valve 20 is at the third switching position H, and
the second switching valve 30 is at the second switching position
L, whereby the first switching valve 20 is closed, and the second
switching valve 30 is open. In this condition, the independent air
intake passages 12 are kept divided into two groups in which the
intake strokes of the passages keep equal interval and do not
overlap one another and the air intake system has a third natural
frequency higher than the second natural frequency. In this
condition, the volumetric chamber 40 and upstream portions of the
branch passages 16a, 16b function as an air expanding chamber. FIG.
16 shows the condition that the first switching valve 20 is at the
fourth switching position J, and the second switching valve 30 is
at the third switching position M, and thus the first and the
second switching valves 20, 30 are open. The air induction system
has a fourth natural frequency formed by the surge tank 14
(functioning as the single air expanding chamber), the volumetric
chamber 40 and two branch passages 16a, 16b. The expanded volume
equals the total volume of the surge tank 14, the volumetric
chamber 40, and the two branch passages 16a 16b.
[0062] FIG. 17 is a schematic graph showing the relationship
between the engine rpm and the output torque.
[0063] In FIG. 17, the engine rpm is shown along a horizontal axis
and the output torque of the engine is shown along a vertical axis.
The relationship between the engine rpm and the output torque of
the air induction system shown in FIGS. 13, 14, 15, 16 is
illustrated in FIG. 17 as lines W, X, Y, and Z respectively. FIG.
17 includes a first predetermined rpm number N1, a second
predetermined rpm number N2, and a third predetermined rpm number
N3.
[0064] Referring to figures, the operation of the air induction
system of the engine of the embodiment of the present invention at
lower engine speed, at mid-low engine speed, at mid-high engine
speed, and higher engine speed will be explained as follows.
[0065] When the engine rpm is less than the first predetermined
number N1 (lower engine speed), the actuator 3 is not driven. As
shown in FIG. 8, the first switching valve 20 of the air intake
system 10 is in the first switching position to form one single air
expanding chamber by establishing the communication of the two
sections 14a, 14b of the surge tank 14. As shown in FIG. 5, the
second switching valve 30 is in the first switching position to
block the communication between the branch passages 16a, 16b and
the volumetric chamber 40. Accordingly, the air intake system shown
in FIG. 13 is formed when the engine rpm is equal to or less than
the first predetermined number N1. That is, the air intake system
includes the expanded volume formed by the independent air intake
passages 12 and the surge tank 14 (functioning as a single air
expanding chamber) having a first natural frequency. As shown as
Win FIG. 17, when the engine rpm is less than the first
predetermined number N1, the first natural frequency of the air
intake system and the frequency of the induction air pulsation
become resonant to provide the supercharging effect by the
interference among the independent air intake passages thereby to
obtain the maximum output torque.
[0066] When the engine rpm is equal to or more than the first
predetermined number N1 and less than the second predetermined
number N2 (mid-low engine speed), the first switching valve 20 is
rotated by the angle B by the actuator 3 to divide the surge tank
14 into two air intake passages as shown at the position G of FIG.
8. Since the rotational force of the actuator 3 is not transmitted
from the first transmitting shaft 25 to the second transmitting
shaft 36, the second switching valve 30 remains at the position
shown in FIG. 5. That is, the second switching valve 30 is
maintained at the fist switching position, wherein the branch
passages 16a, 16b function as independent passages. Accordingly,
when the engine rpm is equal to or more than the first
predetermined number N1 and less than the second predetermined
number N2, as shown in FIG. 14, the air induction system of the
embodiment of the present invention includes the longest air intake
passage in this embodiment and has a second natural frequency. In
the engine speed range shown as X in FIG. 17 whose engine rpm is
equal to or more than the first predetermined number N1 and less
than the second predetermined number N2, the second natural
frequency of the air intake system and the frequency of the air
induction pulsation become resonant to provide the inertia effect
and the resonance effect to obtain the maximum output torque.
[0067] When the engine rpm is equal to or more than the second
predetermined number N2 and less than the third predetermined
number N3 (mid-high revolution speed), the first switching valve 20
is rotated by the angle B to divide the surge tank 14 into two
smaller chambers 14a, 14b functioning as first and the second air
intake passages as shown at the position H of FIG. 8. Since the
rotational force of the actuator 3 is transmitted to the second
switching valve 30 via the first transmitting shaft 25 and the
second transmitting shaft 36, the second switching valve 30 is
moved to the second switching position (shown in FIG. 6) to
establish the communication between the first branch passage 16a
and the second branch passage 16b via the communication portion 17
and the volumetric chamber 40. Accordingly, as shown in FIG. 15,
the air induction system 10 includes an air intake passage shorter
than the one in FIG. 14 and longer than the one in FIG. 13 and has
a third natural frequency. The air induction system has different
natural frequencies based on the number of engine rpm at the low
engine speed range and the mid-low engine speed range. As shown as
Y in FIG. 17, when the engine rpm is equal to or more than the
second predetermined number N2 and less than the third
predetermined number N3, the inertia effect and the resonance
effect can be obtained to provide the maximum output torque.
However, the engine output torque cannot be obtained when the
engine rpm is equal to or more than the third predetermined number
N3.
[0068] When the engine rpm is equal to or more than the third
predetermined number N3 (higher engine speed), the first switching
valve 20 is rotated by angle B by the actuator 3 to establish the
communication of the two sections 14a, 14b of the surge tank 14 as
shown at the position J of FIG. 8 to form a single air expanding
chamber. As shown in FIG. 12, the rotational force of the actuator
3 is transmitted to the second switching valve 30 via the first
transmitting shaft 25 and the second transmitting shaft 36 to
rotate the second switching valve 30 by the angle B. As the result,
the switching position of the second switching valve 30 is changed
to establish communication between the first branch passage 16a and
the second branch passage 16b via the communication portion 17 and
the volumetric chamber 40. Thus, the air induction system comprises
the surge tank 14 (functioning as a single air expanding chamber),
the first and the second branch passages 16a, 16b, and the
volumetric chamber 40 and includes two short air intake passages
having the length of the independent air intake passages 12. In
this case, since the volume of the air induction system 10 is
expanded to the maximum volume in the embodiment of the present
invention, the pumping losses can be reduced and the maximum output
torque can be obtained when the engine rpm is equal to or more than
the third predetermined number N3 as shown as Z of FIG. 17.
Although the engine response may be delayed due to the expanded air
volume, the influence thereof can be reduced since the expanded
volume of the air induction system is needed only at high engine
speed range when the engine rpm is equal to or more than the third
predetermined number N3, in other words, when the amount of
induction air per time is large.
[0069] By obtaining the foregoing effects, the air induction system
of the embodiment of the present invention can be structured to
have the foregoing characteristics in accordance with the engine
rpm by rotating the first and the second switching valves 20, 30 by
the actuator 3, which enables the air induction system of the
engine to provide an appropriate output torque of the engine and to
prevent slow engine response.
[0070] The operation of the first switching valve 20 rotated from
the position J to the position F as shown in FIG. 8 and the
operation of the second switching valve 30 rotated from the
position M shown in FIG. 7 to the position K shown in FIG. 5 will
be explained referring to FIGS. 4-14.
[0071] When a rotational force is generated by the actuator 3 to
move the first switching valve 20 from the position J to the
position H (shown in FIG. 8), that is to rotate the first
transmitting shaft 25 from the position S to the position R (shown
in FIG. 12), the first transmitting shaft 25 and the lug 26 are
rotated by the angle B to the position R shown in FIG. 11.
Accompanying that, the lug 26 (the first transmitting shaft 25) and
the contacting portion 37 (the second transmitting shaft 36)
keeping in contact with each other are moved together by the
biasing force of the return spring 4. When the lug 26 is maintained
at the position R by the actuator 3, further rotation of the second
transmitting shaft 36 is prevented. This maintains the second
transmitting shaft 36 at the position R. Accordingly, in accordance
with the rotation of the second transmitting shaft 36, the second
switching valve 30 is rotated from the position M (the third
switching position shown in FIG. 7) to the position L (the second
switching position shown in 6).
[0072] When the first transmitting shaft 25 is rotated by the angle
B by the actuator 3, the second transmitting shaft 36 is rotated by
the biasing force of the return spring 4. The second switching
valve 30 is rotated until rotation of the second transmitting shaft
36 by the biasing force of the return spring 4 is prevented by the
rotational force of the actuator 3. Thus, the first switching valve
20 is maintained at the position G (the second switching position)
and the second switching valve 30 is maintained at the position K
(the first switching position).
[0073] When the second transmitting shaft 36 reaches the position Q
(when the second switching valve 30 comes to the position K), the
rotation of the second switching valve 30 is prevented by the
stopper 39 as well as the stopper supporting portion 15a to
maintain the second transmitting shaft 36 at the initial attaching
position (the position Q). Only the first transmitting shaft 25 can
be moved to the initial attaching position (the position P) by
being rotated through the angle B by the actuator 3. Accordingly,
the first switching valve 20 can be rotated to the position F (the
first switching position) while the second switching valve 30 is
maintained at the position K. Although the second switching valve
30 is rotated by 180 degrees in one direction and rotated in the
other direction to return to the initial attaching position in this
embodiment, the switching valve 30 may be rotated 360 degrees to
return to the initial attaching position.
[0074] As described above, according to the embodiment of the
present invention, the characteristics of the air induction system
such as the dynamic effect of the induction air, the length of the
air intake passage necessary for generating the inertia effect and
the resonance effect, and the volume of the air expanding chamber,
can be varied in accordance with the valve of the engine rpm by
controlling the opening and closing of the first and the second
switching valves 20, 30. Thus, the air induction system can obtain
the maximum dynamic effect of the induction air for broader engine
speed range, which leads to an improvement of the engine output
performance for broader engine speed.
[0075] Although a plurality of switching valves are necessary for
varying the characteristics of the air induction system in order to
obtain the dynamic effect of the induction air for broader speed
range in the conventional air induction system, and a plurality of
drive means and control means are necessary due to the use of a
plurality of switching valves, according to the embodiment of the
present invention, the aforementioned air induction system can be
structured by using a single drive means and the control means.
[0076] The effects of the embodiment according to the present
invention are as follows. The volume of the air induction system
can be expanded by providing the second switching valve
communicating the branch passages with the volumetric chamber to
reduce the pumping losses at high engine speed range. Accordingly,
a larger amount of the induction air can be supplied to the
cylinders of the engine at high engine speed range, and the output
performance of the engine can be improved. In addition, since the
volume of the air induction system is not expanded at the other
engine speed range which does not require the expansion of the
volume of the air induction system, a delay of the engine response
can be prevented.
[0077] Further effects of the embodiment according to this
invention are as follows. By providing the volumetric chamber by
utilizing the second switching valve having a hollow cylindrical
shape with bottoms in the space between the branch passages which
is a dead space in the conventional art, the space in the air
induction system can be used effectively. In addition, this
structure makes it easier to establish communication between the
branch passages and the volumetric chamber. Thus, a second and a
third air expanding chamber can be provided with simple
structure.
[0078] Still further effects of the embodiment according to this
invention are as follows. Since the first switching valve and the
second switching valve are actuated at a predetermined condition,
the opening and the closing of the switching valves can be
controlled to form a complicated structure of the air induction
system by a single drive means. Accordingly, the air induction
system has a plurality of characteristics in accordance with the
range of the engine revolution. By varying the natural frequency of
the air induction system, the engine rpm valve, which provides the
inertia effect and the resonant effect, is changed. Thus, the
output performance of the broader engine rpm range can be
improved.
[0079] The principles, preferred embodiments and modes of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiment disclosed. Further, the embodiment described herein is
to be regarded as illustrative rather than restrictive. Variations
ana changes may be made by others, and equivalents employed,
without departing from the spirit of the present invention.
Accordingly, it is expressly intended that all such variations,
changes and equivalents which fall within the spirit and scope of
the present invention as defined in the claims, be embraced
thereby.
* * * * *