Flow control device of a helically-shaped intake port

A helically-shaped intake port comprising a helical portion formed around an intake valve and a substantially straight inlet passage portion tangentially connected to the helical portion. A bypass passage is branched off from the inlet passage portion and connected to the helical portion. A rotary valve is arranged in the bypass passage and actuated by a vacuum operated diaphragm apparatus. The rotary valve is opened when the amount of air fed into the cylinder of an engine is increased beyond a predetermined value. A cooling water passage is arranged beneath and near the bypass passage.

BACKGROUND OF THE INVENTION 
The present invention relates to a flow control device of a 
helically-shaped intake port of an internal combustion engine. 
A helically-shaped intake port normally comprises a helical portion formed 
around the intake valve of an engine and a substantially straight inlet 
passage portion tangentially connected to the helical portion. However, if 
such a helically-shaped intake port is so formed that a strong swirl 
motion is created in the combustion chamber of an engine when the engine 
is operating at a low speed under a light load, that is, when the amount 
of air fed into the cylinder of the engine is small, since air flowing 
within the helically-shaped intake port is subjected to a great flow 
resistance, a problem occurs in that the volumetric efficiency is reduced 
when the engine is operating at a high speed under a heavy load, that is, 
when the amount of air fed into the cylinder of the engine is large. 
In order to eliminate such a problem, the inventor has proposed a flow 
control device in which a bypass passage, branched off from the inlet 
passage portion and connected to the helix terminating portion of the 
helical portion, is formed in the cylinder head of an engine. A normally 
closed type flow control valve, actuated by an actuator, is arranged in 
the bypass passage and opened under the operation of the actuator when the 
amount of air fed into the cylinder of the engine is larger than a 
predetermined amount. 
In this flow control device, when the amount of air fed into the cylinder 
of the engine is large, that is, when the engine is operating under a 
heavy load at a high speed, a part of the air introduced into the inlet 
passage portion is fed into the helical portion of the helically-shaped 
intake port via the bypass passage. This reduces the flow resistance of 
the helically-shaped intake port and, thus, enables high volumetric 
efficiency. 
This flow control device, however, is just the embodiment of the basic 
principle of operation. In order to commercialize such a flow control 
device, various problems remain to be solved, for example, how to reduce 
manufacturing time and manufacturing cost, how to easily manufacture the 
flow control device, and how to obtain reliable flow control device 
operation. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a flow control device with 
a helically-shaped intake port, which has a construction suited for 
commercializing the basic principle of operation proposed by the inventor. 
According to the present invention, there is provided a device for 
controlling the flow in a helically-shaped intake port of an internal 
combustion engine, said intake port comprising a helical portion formed 
around an intake valve, and a substantially straight inlet passage portion 
tangentially connected to the helical portion and having a helix 
terminating portion, said device comprising: a bypass passage branched off 
from the inlet passage portion and connected to the helix terminating 
portion of the helical portion, said bypass passage having a bottom wall; 
a normally closed rotary valve arranged across said bypass passage for 
controlling the flow area of said bypass passage; a cooling water passage 
arranged beneath and near the bottom wall of said bypass passage; and 
actuating means for actuating said rotary valve in response to the change 
in the amount of air fed into the intake port to open said rotary valve 
when said amount of air is increased beyond a predetermined value. 
The present invention may be more fully understood from the description of 
preferred embodiments of the invention set forth below, together with the 
accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, reference numeral 1 designates a cylinder 
block, 2 a piston reciprocally movable in the cylinder block 1, 3 a 
cylinder head fixed onto the cylinder block 1, and 4 a combustion chamber 
formed between the piston 2 and the cylinder head 3; 5 designates an 
intake valve, 6 a helically-shaped intake port formed in the cylinder 
head, 7 an exhaust valve, and 8 an exhaust port formed in the cylinder 
head 3. A spark plug (not shown) is arranged in the combustion chamber 4. 
FIGS. 4 through 6 schematically illustrate the shape of the 
helically-shaped intake port 6 illustrated in FIG. 2. As illustrated in 
FIG. 5, the helically-shaped intake port 6 comprises an inlet passage 
portion A, the longitudinal central axis of which is slightly curved, and 
a helical portion B, formed around the valve stem of the intake valve 5. 
The inlet passage portion A is tangentially connected to the helical 
portion B. 
As illustrated in FIGS. 4, 5 and 8, the side wall 9 of the inlet passage 
portion A, which is located near the helical portion B, has on its upper 
portion an inclined wall portion 9a which is arranged to be directed 
downwards. The width of the inclined wall portion 9a is gradually 
increased toward the helical portion B. As illustrated in FIG. 8, the 
entire portion of the side wall 9 is inclined at the connecting portion of 
the inlet passage portion A and the helical portion B. The upper half of 
the side wall 9 is smoothly connected to the circumferential wall of a 
cylindrical projection 11 (FIG. 2) which is formed on the upper wall of 
the intake port 6 at a position located around a valve guide 10 of the 
intake valve 5. The lower half of the side wall 9 is connected to the side 
wall 12 of the helical portion B at the helix terminating portion C of the 
helical portion B. In addition, the upper wall 13 of the helical portion B 
is connected to a steeply inclined wall D at the helix terminating portion 
C of the helical portion B. 
As illustrated in FIGS. 1 through 6, bypass passages 14, branched off from 
the inlet passage portions A of the corresponding intake ports 6 and 
having a substantially uniform cross-section, are formed in the cylinder 
head 3. Each of the bypass passages 14 is connected to the helix 
terminating portion C of the corresponding intake port 6. Each of the 
inlet openings 15 of the bypass passages 14 is formed on the side wall 9 
at a position located near the inlet open end of the inlet pasage portion 
A of the corresponding intake port 6. Each of the outlet openings 16 of 
the bypass passages 144 is formed on the upper end portion of the side 
wall 12 at the helix terminating portion C of the corresponding intake 
port 6. 
In addition, valve insertion bores 17, extending across the corresponding 
bypass passages 14, are formed in the cylinder head 3. Rotary valves 18, 
each functioning as a flow control valve, are inserted into the 
corresponding valve insertion bores 17. 
Referring to FIG. 10, each of the valve insertion bores 17 is a cylindrical 
bore drilled downwardly from the upper surface of the cylinder head 3 and 
having a uniform diameter over the entire length thereof. The valve 
insertion bore 17 extends downward beyond the bypass 14 and, thus, a 
recess 19 is formed on the bottom wall of the bypass passage 14. An 
internal thread 20 is formed on the upper portion of the valve insertion 
bore 17 and a rotary valve holder 21 is screwed into the internal thread 
20. The rotary valve holder 21 has a circumferential flange 22 on the 
outer circumferential wall thereof. A seal member 23 is inserted between 
the flange 22 and the cylinder head 3. A bore 24 is formed in the rotary 
valve holder 21, and a valve shaft 25 of the rotary valve 18 is rotatably 
inserted into the bore 24. A thin plate-shaped valve body 26 is fixed onto 
the lower end of the valve shaft 25, and an arm 27 is fixed onto the top 
end of the valve shaft 25 by means of a bolt 29 via a washer 28. A ring 
groove 30 is formed on the outer circumferential wall of the valve shaft 
25 at a level which is almost the same as that of the top end face of the 
rotary valve holder 21, and a C-shaped positioning ring 31 (FIG. 12) is 
fitted into the ring groove 30. The positioning ring 31 engages with a 
frustum-shaped face 32 formed on the inner periphery of the top end wall 
of the rotary valve holder 21 for retaining the valve body 26 at a 
predetermined position. A seal member 34, surrounded by a reinforcement 
frame 33, is fitted onto the upper portion of the rotary valve holder 21. 
The seal portion 34a of the seal member 34 is pressed in contact with the 
outer circumferential wall of the valve shaft 25 by means of an elastic 
ring 35 which is inserted around the outer circumferential wall of the 
seal member 34. Consequently, the bypass passage 14 is completely shielded 
from ambient air by means of the seal members 23, 34. Since the seal 
member 34 is fixed onto the rotary valve holder 21, the valve shaft 25 
rotates relative to the seal portion 34a of the seal member 34 when the 
rotary valve 18 rotates. Consequently, it is preferable that the inner 
surface of the seal portion 34a of the seal member 34 be covered by a thin 
layer made of tetrafluoroethylene for reducing the frictional resistance 
between the seal member 34 and the valve shaft 25. 
As illustrated in FIG. 10, the valve body 26 has a width which is slightly 
smaller than the inner diameter of the valve insertion bore 17, and the 
valve body 26 is arranged so that the lower end thereof is slightly spaced 
from the bottom wall of the recess 19. On the other hand, as ilustrated in 
FIGS. 2 and 3, a cooling water passage 36 is formed in the cylinder head 3 
at a position located beneath and near the bypass passage 14, and the 
exhaust port 8 is arranged laterally to and near the bypass passage 14. 
Referring to FIG. 13, the tip of the arm 27 fixed onto the tope end of the 
valve shaft 25 is connected via a connecting rod 43 to a control rod 42 
which is fixed onto a diaphragm 41 of a vaccum operated diaphragm 
apparatus 40. The diaphragm apparatus 40 comprises a vacuum chamber 44 
separated from the atmosphere by the diaphragm 41. A compression spring 45 
for biasing the diaphragm 41 is inserted into the vacuum chamber 44. 
An intake manifold 47, equipped with a compound type carburetor 46 
comprising a primary carburetor A and a secondary carburetor B, is mounted 
on the cylinder head 3. The vacuum chamber 44 is connected to the interior 
of the intake manifold 47 via a vacuum conduit 48. A check valve 49, 
permitting air to flow from the vacuum chamber 44 into the intake manifold 
47, is arranged in the vacuum conduit 48. In addition, the vacuum chamber 
44 is connected to the atmosphere via an atmosphere conduit 50 and a 
control valve 51. This control valve 51 comprises a vacuum chamber 53 and 
an atmospheric pressure chamber 54 which are separated by a diaphragm 52. 
In addition, the control valve 51 further comprises a valve chamber 55 
arranged adjacent to the atmospheric pressure chamber 54. The valve 
chamber 55 is connected, on one hand, to the vacuum chamber 44 via the 
atmosphere conduit 50 and, on the other hand, to the atmosphere via a 
valve port 56 and an air filter 57. A valve body 58, controlling the 
opening operation of the valve port 56, is arranged in the valve chamber 
55 and connected to the diaphragm 52 via a valve rod 59. A compression 
spring 60 for biasing the diaphragm 52 is inserted into the vacuum chamber 
53. The vacuum chamber 53 is connected to a venturi portion 62 of the 
primary carburetor A via a vacuum conduit 61. 
The carburetor 46 is a conventional carburetor. Consequently, when the 
opening degree of a primary throttle valve 63 is increased beyond a 
predetermined degree, a secondary throttle valve 64 is opened. When the 
primary throttle valve 63 is fully opened, the secondary throttle valve 64 
is also fully opened. The level of vacuum produced in the venturi portion 
62 of the primary carburetor A is increased as the amount of air fed into 
the cylinder of the engine is increased. Consequently, when a great vacuum 
is produced in the venturi portion 62, that is, when the engine is 
operating at a high speed under a heavy load, the diaphragm 52 of the 
control valve 51 moves toward the right in FIG. 13 against the compression 
spring 60. As a result of this, the valve body 58 opens the valve port 56 
and, thus, the vacuum chamber 44 of the diaphragm apparatus 40 becomes 
open to the atmosphere. At this time, the diaphragm 41 moves downward in 
FIG. 13 due to the spring force of the compression spring 45 and, thus, 
the rotary valve 18 is rotated and fully opens the bypass passage 14. 
On the other hand, in the case wherein the opening degree of the primary 
throttle valve 63 is small, since the vacuum produced in the venturi 
portion 62 is small, the diaphragm 52 of the control valve 51 moves toward 
the left in FIG. 13 due to the spring force of the compression spring 60. 
As a result, the valve body 58 closes the valve port 56. In addition, in 
the case wherein the opening degree of the primary throttle valve 63 is 
small, a great vacuum is produced in the intake manifold 47. Since the 
check valve 49 opens when the level of vacuum produced in the intake 
manifold 47 becomes greater than that of the vacuum produce in the vacuum 
chamber 44 and since the check valve 49 closes when the level of the 
vacuum produced in the intake manifold 47 becomes smaller than that of the 
vacuum produced in the vacuum chamber 44, the level of the vacuum in the 
vacuum chamber 44 is maintained at the maximum vacuum which has been 
produced in the intake manifold 47 as long as the control valve 51 remains 
closed. If a vacuum is produced in the vacuum chamber 44, the diaphragm 41 
moves upward in FIG. 13 against the compression spring 45. As a result, 
the rotary valve 18 is rotated and closes the bypass passage 14. 
Consequently, when the engine is operating at a low speed under a light 
load, the bypass passage 14 is closed by the rotary valve 18. In the case 
wherein the engine speed is low even if the engine is operating under a 
heavy load and in the case wherein the engine is operating under a light 
load even if the engine speed is high, since the vacuum produced in the 
venturi portion 62 is small, the control valve 51 remains closed. 
Consequently, when the engine is operating at a low speed under a heavy 
load and at a high speed under a light load, since the level of the vacuum 
in the vacuum chamber 44 is maintained at the above-mentioned maximum 
vacuum, the bypass passage 14 is closed by the rotary valve 18. 
As mentioned above, when the engine is operating at a low speed under a 
light load, that is, when the amount of air fed into the cylinder of the 
engine is small, the rotary valve 18 closes the bypass passage 14. At this 
time, the mixture introduced into the inlet passage portion A moves 
downward, while swirling, along the upper wall 13 of the helical portion 
B. Then, since the mixture, while swirling, flows into the combustion 
chamber 4, a strong swirl motion is created in the combustion chamber 4. 
When the engine is operating at a high speed under a heavy load, that is, 
when the amount of air fed into the cylinder of the engine is large, since 
the rotary valve 18 opens the bypass passage 14, a part of the mixture 
introduced into the inlet passage portion A is fed into the helical 
portion B via the bypass passage 14 having a low flow resistance. Since 
the flow direction of the mixture stream flowing along the upper wall 13 
of the helical portion B is deflected downward by the steeply inclined 
wall D of the helix terminating portion C, a great vacuum is produced at 
the helix terminating portion C, that is, in the outlet opening 16 of the 
bypass passage 14. Consequently, since the pressure difference between the 
vacuum in the inlet passage portion A and the vacuum in the helix 
terminating portion C becomes large, a large amount of the mixture is fed 
into the helical portion B via the bypass passage 14 when the rotary valve 
18 opens. As mentioned above, when the engine is operating at a high speed 
under a heavy load, since the rotary valve 18 opens, the entire flow area 
of the intake port 6 is increased and a large amount of the mixture is fed 
into the helical portion B via the bypass passage 14 having a low flow 
resistance. As a result of this, it is possible to obtain a high 
volumetric efficiency. In addition, by forming the inclined wall portion 
9a, the flow direction of a part of the mixture introduced into the inlet 
passage portion A is deflected downward. As a result of this, since the 
part of the mixture flows into the helical portion B along the bottom wall 
of the intake port 6 without swirling, the flow resistance of the intake 
port 6 becomes small. This makes it possible to further increase 
volumetric efficiency when the engine is operating at a high speed under a 
heavy load. 
As mentioned above, when the engine is rotating at a low speed under a 
light load, the rotary valve 18 closes the bypass passage 14. At this 
time, if fuel is accumulated in the bypass passage 14 located upstream of 
the rotary valve 18, when the rotary valve 18 opens, the fuel thus 
accumulated is fed into the cylinder of the engine. As a result of this, 
since the air-fuel mixture fed into the cylinder of the engine becomes 
temporarily rich, a problem occurs in that the exhaust emission will 
deteriorate. However, in the present invention, as illustrated in FIG. 10, 
since a gap is formed between the lower end of the valve body 26 and the 
bottom wall of the recess 19, fuel flows into the helical portion B via 
that gap. This makes it possible to prevent fuel from accumulating in the 
bypass passage 14. 
In the present invention, since the rotary valve 18 is inclined, it is 
necessary to form the recess 19 on the bottom wall of the bypass passage 
14 for receiving the lower end of the valve body 26. Normally, if the 
recess 19 is formed on the bottom wall of the bypass passage 14, fuel 
easily accumulates in the recess 19. Nevertheless, in the present 
invention, since the cooling water passage 36 and the exhaust port 8 are 
arranged in the vicinity of the bypass passage 14, as previously 
mentioned, the bottom wall of the recess 19 is heated by the cooling water 
of the engine and the exhaust gas. As a result of this, the vaporization 
of fuel located within the recess 19 is promoted. This makes it possible 
to suppress fuel from accumulating in the recess 19. 
FIG. 14 illustrates another embodiment of the rotary valve 18. In this 
embodiment, the valve body 26 and the valve shaft 25 are separately 
formed, and a projection 70 formed in one piece on the top of the valve 
body 26 is fitted into a bore 71 formed on the lower end of the valve 
shaft 25. In addition, in this embodiment, instead of using the seal 
member 23 (FIG. 10), an O ring 72 is inserted between the cylinder head 3 
and the flange 22 of the rotary valve holder 21. 
FIG. 15 illustrates a further embodiment of the rotary valve 18. In this 
embodiment, a disc-shaped enlarged portion 73 is formed in one piece on 
the lower end of the valve shaft 25. A thin plate-shaped valve body 26 is 
welded to the enlarged portion 73 after the valve body 26 is fitted into a 
diametrically extending groove 74 formed on the lower surface of the 
enlarged portion 73. In addition, on O ring 75 is inserted between the 
valve shaft 25 and the rotary valve holder 21. The bypass passage 14 is 
shielded from ambient air by means of the O ring 75. Consequently, in this 
embodiment, it is possible to omit the seal member 34 illustrated in FIG. 
14. 
According to the present invention, since the rotary valve can be assembled 
to the cylinder head by merely inserting the rotary valve into the valve 
insertion bore, the assembling operation of the rotary valve becomes very 
easy. In addition, since the rotary valve has a small size and a simple 
construction, the manufacturing cost of the rotary valve can be reduced 
and the rotary valve can be easily assembled to the cylinder head even if 
the cylinder head little space on the upper face thereof. Furthermore, 
since the bypass passage is formed so that the inner wall thereof is 
heated by the cooling water of the engine and the exhaust gas, the 
vaporization of fuel in the bypass passage is promoted. Since the bypass 
passage is formed so that fuel can pass through the rotary valve even if 
the rotary valve is closed, it is possible to suppress fuel from 
accumulating in the bypass passage when the rotary valve is closed. As a 
result, since there is no changer that a rich air-fuel mixture will be fed 
into the cylinder of the engine immediately after the rotary valve opens, 
good exhaust emission can be obtained. 
While the invention has been described with reference to specific 
embodiments chosen for purposes of illustration, it should be apparent 
that numerous modifications could be made thereto by those skilled in the 
art without departing from the spirit and scope of the invention.