Flow Control Device of a Helically-Shaped Intake Port

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, 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 thus, enabling 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 a reliable flow control device operation.

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 which has an intake passage connected to said intake port and has a carburetor having a venturi portion, 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; normally closed valve means arranged in said bypass passage for controlling the flow area of said bypass passage; a vacuum operated apparatus having a vacuum chamber and connected to said valve means for actuating said valve means in response to a change in the level of vacuum produced in said vacuum chamber; and control means having a vacuum port which interconnects said vacuum chamber to said intake passage, a check valve which cooperates with said vacuum port and opens said vacuum port when the level of vacuum in said intake passage becomes greater than that of vacuum in said vacuum chamber, an atmosphere port which interconnects said vacuum chamber to the atmosphere and has a flow area which is slightly larger than that of said vacuum port, a vacuum cavity connected to the venturi portion of said carburetor, and an air valve which cooperates with said atmosphere port and is actuated in response to a change in the level of vacuum produced in said valve cavity for opening said atmosphere port to open said valve means when the level of vacuum in said venturi portion becomes greater than a predetermined level.

The present invention may be more fully understood from the description of a preferred embodiment of the invention set forth below, together with the accompanying drawings.

In the drawings:

FIG. 1 is a plan view of an internal combustion engine according to the present invention;

FIG. 2 is a cross-sectional view taken along the line II--II in FIG. 1;

FIG. 3 is a perspective view schematically illustrating the shape of a helically-shaped intake port;

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is a cross-sectional view taken along the bypass passage in FIG. 3;

FIG. 6 is a cross-sectional view taken along the line VI--VI in FIG. 4;

FIG. 7 is a cross-sectional view taken along the line VII--VII in FIG. 4;

FIG. 8 is a cross-sectional view taken along the line VIII--VIII in FIG. 4;

FIG. 9 is a perspective view of a rotary valve; and

FIG. 10 is a view illustrating the entirety of a flow control device.

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. 3 through 5 schematically illustrate the shape of the helically-shaped intake port 6 illustrated in FIG. 2. As illustrated in FIG. 4, 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. 3, 4, and 7, the side wall 9 of the inlet passage portion A, which is located near the helix axis 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 towards the helical portion B, and as is illustrated in FIG. 7, the entire portion of the side wall 9 is inclined at the connectig 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.

As illustrated in FIGS. 1 through 5, bypass passages 14, branched off 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, and each of the bypass passages 14 is connected to the helix terminating portion C of the corrresponding 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 passage portion A of the corresponding intake port 6, and each of the outlet openings 16 of the bypass passages 14 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, and rotary valves 18, each functioning as a flow control valve, are inserted into the corresponding valve insertion bores 17. The rotary valves 18 are inserted into the corresponding bypass passages 14, and as illustrated in FIG. 9, each of the rotary valves 18 comprises a thin plate-shaped valve body 19, and a valve shaft 20 formed in one piece on the valve body 19. The valve shaft 20 is rotatably supported by a guide sleeve 21 fitted into the valve insertion bore 17. The valve shaft 20 projects upwardly from the top face of the guide sleeve 21, and an arm 22 is fixed onto the projecting tip portion of the valve shaft 20.

Referring to FIG. 10, the tip of the arm 22 fixed onto the top end of the valve shaft 20 is connected via a connecting rod 43 to a control rod 42 which is fixed onto a diaphragm 41 of a vacuum operated diaphragm apparatus 40. The diaphragm apparatus 40 comprises a vacuum chamber 44 separated from the atmosphere by the diaphragm 41, and 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 46a and a secondary carburetor 46b, is mounted on the cylinder head 3, and the vacuum chamber 44 is connected to the interior of the intake manifold 47 via a vacuum conduit 48, a vacuum control valve device 49 and a vacuum conduit 50. As illustrated in FIG. 10, the vacuum control valve device 49 comprises three housings, that is, a first housing 51, a second housing 52, and a third housing 53 which are interconnected to each other by using, for example, an ultrasonic welding. A vacuum introduction chamber 54 is formed in the first housing 51 and connected to the interior of the intake manifold 47 via the vacuum conduit 50. An interior passage 55, extending on the axis of the vacuum control valve device 49, is formed in the second housing 52 and has a vacuum port 56 and an atmosphere port 57 at opposite ends thereof. As will be hereinafter described in detail, the atmosphere port 57 has a flow area which is slightly larger than that of the vacuum port 56. In the embodiment illustrated in FIG. 10, the atmosphere port 57 has a diameter of 0.8 mm, and the vacuum port 56 has a diameter of 0.6 mm. The interior passage 55, connected to both the atmosphere port 57 and the vacuum port 56, is connected to the vacuum chamber 44 of the diaphragm apparatus 40.

A check valve 58 for controlling the opening operation of the vacuum port 56 is inserted into the vacuum introduction chamber 54 formed in the first housing 51. The check valve 58 comprises a valve body 59 for closing the vacuum port 56, a spring retainer 60 supported by the valve body 59, and a compression spring 61 inserted between the spring retainer 60 and the upper wall of the vacuum introduction chamber 54 for basing the valve body 59 towards the vacuum port 56. An air valve 62 is integrally assembled to the vacuum control valve device 49 and has a diaphragm 63. A valve 64 for controlling the opening operation of the atmosphere port 57 is fixed onto the central portion of the diaphragm 63, and the peripheral edge portion of the diaphragm 63 is held between the second housing 52 and the third housing 53. An atmospheric pressure chamber 65 is formed between the diaphragm 63 and the second housing 52 and is open to the atmosphere via an air introduction bore 66 formed in the second housing 52 and via an air filter 67. The air filter 67 is supported by a cap 68 fitted onto the second housing 52. A vacuum chamber 69 is formed between the diaphragm 63 and the third housing 53 and connected via a vacuum conduit 70 to vacuum ports 71 and 72 which are open to the venturi portions of the primary carburetor 46a and the secondary carburetor 46b, respectively. An adjusting screw 73 is screwed into the lower end portion of the third housing 53, and a compression spring 75 is inserted between the valve body 64 of the diaphragm 63 and a spring retainer 74 fitted onto the top of the adjusting screw 73 for biasing the valve body 64 towards the atmosphere port 57.

The carburetor 46 is a conventional carburetor. Consequently, when the opening degree of a primary throttle valve 76 is increased beyond a predetermined degree, a secondary throttle valve 77 is opened. When the primary throttle valve 76 is fully opened, the secondary throttle valve 77 is also fully opened. The level of vacuum acting on the vacuum conduit 70 connected to the vacuum ports 71, 72 is increased as the amount of air fed into the cylinders of the engine is increased. Consequently, when the engine is operating at a high speed under a heavy load, that is, when the level of vacuum acting on the vacuum conduit 70 becomes greater than a predetermined level, the diaphragm 63 of the air valve 62 moves downward in FIG. 10 against the compression spring 75. As a result of this, the valve body 64 opens the atmosphere port 57. 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. 10 due to the spring force of the compression spring 45. 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 76 is small, since the level of vacuum acting on the vacuum conduit 70 is small, the diaphragm 63 of the air valve 62 moves upward in FIG. 10 due to the spring force of the compression spring 75. As a result, the valve body 64 closes the atmosphere port 57. In addition, in the case wherein the opening degree of the primary throttle valve 76 is small, a great vacuum is produced in the intake manifold 47. Since the check valve 58 opens when the level of vacuum produced in the intake manifold 47 becomes greater than that of the vacuum produced in the vacuum chamber 44, and since the check valve 58 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 air valve 51 remains closed. If a vacuum is produced in the vacuum chamber 44, the diaphragm 41 moves upward in FIG. 10 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 acting on the vacuum conduit 70 is small, the air valve 62 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.

In the vacuum control device 49 as illustrated in FIG. 10, the sizes of the atmosphere port 57 and the vacuum port 56 have a great influence on the opening-closing action of the rotary valve 18, and if the sizes of the atmosphere port 57 and the vacuum port 56 are not suitably determined, there is a danger that the rotary valve 18 remains closed independently of the amount of air fed into the cylinders of the engine. For example, in the case wherein the atmosphere port 57 and the vacuum port 56 are formed so that they have the same flow area, and wherein the diaphragm apparatus 40 is constructed so that the diaphragm 41 moves towards the vacuum chamber 44 when the level of vacuum in the vacuum chamber 44 becomes greater than about -70 through -100 mmHg, if the air valve 62 opens when the level of vacuum in the intake manifold 47 is equal to about -300 mmHg, ambient air flows into the interior passage 55 from the atmosphere port 57, and air in the interior passage 55 flows into the intake manifold 47 via the check valve 48. As a result of this, even if the air valve 62 opens, the pressure in the interior chamber 55 does not become equal to the atmospheric pressure, but vacuum, having a level which is equal to the intermediate level between the atmospheric pressure and vacuum produced in the intake manifold 47, for example, vacuum of -150 mmHg acts on the interior passage 55. Consequently, at this time, since the level of vacuum in the vacuum chamber 44 of the diaphragm apparatus 40 becomes equal to -150 mmHg, the diaphragm 41 is retained at the uppermost position in FIG. 10. Therefore, a problem occurs in that, even if the air valve 62 opens, the rotary valve 18 remains closed.

On the other hand, in order to eliminate the above problem, if the atmosphere port 57 and the vacuum port 56 are formed so that the atmosphere port 57 has a flow area which is more than twice the flow area of the vacuum port 56, since the air valve 62 cannot open, a problem occurs in that the rotary valve 18 remains closed. That is, since the level of vacuum in the vacuum chamber 69 of the air valve 62 is equal to the mean valve of vacuum produced in the venturi portions of the primary carburetor 46a and the secondary carburetor 46b, the level of vacuum in the vacuum chamber 69 is small. Consequently, if a great vacuum acts on the atmosphere port 57, since the force pulling the valve body 64 upward caused by vacuum acting on the atmosphere port 57 becomes stronger than the force pulling the valve body 64 downward caused by vacuum acting on the vacuum chamber 69, a problem occurs in that the air valve 62 cannot open.

As a result of repeatedly conducting experiments in order to eliminate the above-mentioned problems, the inventor has proven that, if the atmosphere port 57 and the vacuum port 56 are formed so that the atmosphere port 57 has a flow area which is slightly larger than that of the vacuum port 56, it is possible to open or close the rotating valve 18 in response to the opening and the closing operations of the air valve 62, respectively. In the embodiment illustrated in FIG. 10, the diaphragm 63 of the air valve 62 has a diameter of about 23 mm. In this case, as mentioned previously, it is preferable that the atmosphere port 57 and the vacuum port 56 have a diameter of about 0.8 mm and about 0.6 mm, respectively. Of course, the optimum sizes of the atmosphere port 57 and the vacuum port 56 are changed dependently of the number and the size of the rotary valves 18. It has been proven that it is preferable that the diameter of the atmosphere port 57 be in a range of 0.6 through 1.5 mm, and the diameter of the vacuum port 56 be in a range of 0.4 through 1.2 in an engine for use in a load vehicle. Of course, also in this case, it is necessary that the atmosphere port 57 has a diameter which is slightly larger than that of the vacuum port 56.

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. Then, this part of the mixture collides head-on against the mixture stream flowing along the upper wall 13 of the helical portion B. As a result of this, since the mixture stream flowing along the upper wall 13 of the helical portion B is decelerated, the swirl motion is weakened. 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 the swirl motion is weakened, 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, making it possible to further increase a volumetric efficiency when the engine is operating at a high speed under a heavy load.

According to the present invention, it is possible to assuredly open the rotary valve when the amount of air fed into the cylinders of the engine is increased beyond a predetermined value. In addition, since the level of vacuum acting on the vacuum chamber of the diaphragm apparatus can be controlled by an integrally formed single vacuum control valve device, it is possible to reduce the size of the flow control device and improve the reliability of the flow control device.

While the invention has been described with reference to a specific embodiment chosen for the purpose of illustration, it should be apparent that numerous modifications can be made thereto by those skilled in the art without departing from the spirit and scope of the invention.