JP4252670B2 - Engine intake passage structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an intake passage structure of an engine, and more particularly to an intake passage structure that generates a tumble flow suitable for lean combustion.
[0002]
[Prior art]
An intake passage that communicates with the intake port facing the combustion chamber is partitioned by a partition, one passage communicates with the intake port on the center side of the combustion chamber, and the other passage communicates with the edge side of the combustion chamber. By introducing the intake air into the combustion chamber from the passage side communicating with the intake port on the center side, the intake flow velocity is increased to cause a vertical tumble flow in the combustion chamber to stratify the lean air-fuel mixture for stable lean combustion. An intake passage structure has been proposed for development.
[0003]
The intake passage structure divided into two by such a partition uses a sliding throttle valve, and closes one passage when the opening is low, corresponding to the opening of the throttle valve according to the load. As it is, the air-fuel mixture is allowed to flow only from the other passage, and when the opening of the slide increases, the air-fuel mixture is allowed to flow from both passages to increase the intake air flow velocity at a low opening and cause a tumble flow.
[0004]
[Problems to be solved by the invention]
However, the conventionally proposed two-divided intake passage structure can easily close one of the divided passages depending on the load when a sliding throttle valve is used. It cannot be applied as it is to an intake passage having a valve. This is because intake air flows from around the throttle valve, and it is difficult to flow intake air through only one of the divided passages.
[0005]
When a butterfly throttle valve is used in a divided intake passage structure, a movable mechanism such as a control valve that opens and closes one passage must be used in combination.
[0006]
However, if a movable mechanism is provided in the intake passage, the structure becomes complicated, adjustment is troublesome, and synchronization with the throttle valve may be lost due to long-term use, and stable intake control is difficult.
[0007]
The present invention takes the above-described conventional technology into consideration, and in an intake passage equipped with a butterfly throttle valve, the intake passage is divided into two by a partition wall, and has a simple structure and is stable without using a movable mechanism. An object of the present invention is to provide an intake passage structure for an engine that can open and close one of the divided passages.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in an intake passage structure of an engine having a butterfly type throttle valve in an intake passage communicating with an intake port facing a combustion chamber, an intake passage downstream of the throttle valve is provided. The first and second divided passages are divided into two by a partition wall parallel to the valve shaft of the throttle valve, and the first divided passage is formed so as to face the intake port on the center side of the combustion chamber. The second divided passage is formed so as to face the intake port on the edge side of the combustion chamber, and the second divided passage is formed along the end of the valve body on the low opening side of the throttle valve on the second divided passage side. An intake restriction weir that protrudes from the wall surface toward the center of the intake passage, and the weir has a shape along the trajectory of the rotation end of the valve body of the throttle valve, and the valve shaft engine, characterized in that it further provided on the downstream side Providing an intake passage structure.
[0009]
According to this configuration, the intake passage is divided into two parts by dividing the intake passage, and the weir is provided in the second divided passage communicating with the edge side of the combustion chamber. The second divided passage is closed and intake air is introduced into the combustion chamber only from the first divided passage. As a result, during low load operation, the air-fuel mixture is sucked from the center of the combustion chamber of the intake valve toward the exhaust valve, and a tumble flow can be caused in the combustion chamber. As a result, a tumble flow forming function can be obtained with a simple structure without using a movable mechanism, and there is no need for troublesome adjustment work. High functionality is stably maintained.
[0010]
In a preferred configuration example, a fuel escape groove is formed in the central portion of the weir.
[0011]
According to this configuration, the fuel liquefied in the vicinity of the throttle valve does not collect in the weir but flows downstream through the groove provided in the weir and is vaporized by the heat of the intake pipe.
[0012]
In a further preferred configuration example, the partition wall is provided in the vicinity of the valve shaft, and is provided in the vicinity of the valve shaft so as to be offset further to the open side than the valve body in the fully open position.
[0013]
According to this configuration, since the partition wall is close to the valve shaft, intake air leakage and backflow do not occur between the upstream end of the partition wall and the valve shaft. Further, since the partition wall close to the valve shaft is offset further to the open side than the valve body in the fully open position, the operation up to the fully open position of the throttle valve is not hindered.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of an engine according to an embodiment of the present invention.
The engine 1 has a cylinder 2 and a cylinder head 3 mounted on the cylinder 2, and a piston 4 slides in the cylinder 2. The engine 1 is a four-cycle two-valve engine, and a camshaft 5 connected to a crankshaft (not shown) is provided at the center of the cylinder head 3. An intake-side rocker arm 6 and an exhaust-side rocker arm 7 that are slidably in contact with the cams 5a and 5b of the cam shaft 5 are provided. Each rocker arm 6 and 7 drives the intake valve 8 and the exhaust valve 9 to open and close in synchronization with the crank rotation. 8a and 9a are valve springs, respectively.
[0015]
A combustion chamber 10 is formed in the upper part of the cylinder 2 on the upper surface of the piston 4. A spark plug (not shown) is mounted on the cylinder head 3 side facing the combustion chamber 10. Since the engine 1 of this example is a two-valve engine in which the intake valve 8 and the exhaust valve 9 are arranged close to each other at the center of the top of the combustion chamber 10, the spark plug is provided offset from the top of the combustion chamber 10. Yes.
[0016]
An intake port 11 and an exhaust port 12 are formed in the cylinder head 3 facing the combustion chamber 10. An intake valve 8 and an exhaust valve 9 are attached to open end portions of each intake port 11 and exhaust port 12 on the combustion chamber side so as to be opened and closed. The exhaust port 12 is connected to the exhaust pipe 13, and the intake port 11 is connected to the intake pipe 14. A vaporizer 15 connected to an air cleaner (not shown) is attached to the intake pipe 14. An intake passage 16 is formed through the intake pipe 14 and the carburetor 15.
[0017]
The carburetor 15 drives the jet needle 18 attached to the free piston by the balance between the atmospheric pressure and the intake negative pressure in the diaphragm chamber 17, and causes the venturi unit 20 to suck the fuel through the main nozzle 19. A pilot screw 21 for adjusting fuel during idling and a bypass 21a serving as a fuel outlet during low opening are provided on the downstream side of the diaphragm chamber 17. A butterfly throttle valve 24 in which a butterfly valve body 23 is fixed to the valve shaft 22 is mounted in the intake passage 16 of the carburetor 15.
[0018]
The intake passage 16 on the downstream side of the throttle valve 24 is partitioned by a partition wall 25 parallel to the valve shaft 22 and is divided into two vertically. The partition wall 25 is provided along the intake passage 16 from a position close to the valve shaft 22, and an upper first divided passage 26 and a lower second divided passage 27 are formed in the intake passage 16. The upper first divided passage 26 faces the intake port 11 a on the center side of the combustion chamber 10, and the lower second divided passage 27 faces the intake port 11 b on the edge side of the combustion chamber 10. The intake port 11 in the cylinder head 3 is divided into an intake port (first division passage) 11a on the upper side (center side) and a lower (edge side) intake port (first side) by a partition wall 11c formed integrally with the cylinder head 3. Divided into two divided passages) 11b.
[0019]
In the present embodiment, a weir 28 that protrudes from the wall surface of the second divided passage 27 is provided along the end of the valve body 23 on the low opening side of the throttle valve 24. By such a weir 28, at the time of a low load with a small throttle opening, most of the air passes through the upper opening of the throttle valve in the figure . When the opening is very low at the time of idling, the fuel flows from the pilot screw 21 and further from the bypass 21a when the throttle is opened, and then flows through the first divided passage. In addition, since the air flow is blocked by the weir in the lower second divided passage 27, the air-fuel mixture flows only through the upper first divided passage 26, and the exhaust valve direction from the top of the combustion chamber at the opening end of the intake port 11 Toward the combustion chamber 10. Compared to the case where there is no partition, the intake passage cross-sectional area is about ½, so the intake flow velocity is improved about twice. As a result, a vertical tumble flow is formed in the fuel chamber as indicated by an arrow A in the combustion chamber 10. Strong tumble remains in the compression stroke and combustion is improved. As a result, stable combustion is possible even with a lean air-fuel mixture, and fuel efficiency is improved.
[0020]
2 is an inner surface view of the intake passage as seen from the direction II-II in FIG.
As shown in the drawing, a groove 29 is formed in the central portion of the above-mentioned weir 28. Even if the fuel is liquefied on the upstream side of the weir 28, the fuel flows into the downstream side intake passage through the groove 29 and is vaporized by the heat of the intake pipe 14 to be mixed into the combustion chamber. Therefore, it does not collect on the upstream side of the weir. Therefore, the air-fuel ratio supplied to the combustion chamber is stabilized.
[0021]
FIG. 3 is a diagram of the full throttle state of the above embodiment.
As shown in the figure, the partition wall 25 is provided close to the valve shaft 22 of the throttle valve 24 and is offset further to the open side (upper side) than the valve shaft 22 so as to be positioned above the valve body 23 in the fully opened state. Provided. By disposing the partition wall 25 above the valve shaft 22 in this manner, the opening operation of the valve body 23 up to the fully opened position is not hindered, and a high flow rate is secured, so that the output can be maintained. In this way, intake air flows from the first divided passage when the throttle is at a low opening, and also from the second divided passage when the throttle is at a high opening, so that a stronger tumble is obtained in the combustion chamber at a low opening than at a high opening. . That is, a variable tumble according to the throttle opening can be achieved. For this reason, the intake port can be shaped to have a flow coefficient, and high output can be achieved.
[0022]
FIG. 4 shows an example of a cross-sectional shape of the partition wall 11c . In the two-valve engine, the position of the spark plug 30 facing the combustion chamber 10 is offset somewhat to the side from the top. When the load is low, the air-fuel mixture is supplied only through the upper first division passage 26 in the intake passage as described above. Therefore, the air-fuel mixture is supplied also through the intake port 11 only through the first division passage 11a on the upper side of the partition wall 11c. In this case, it is preferable to concentrate the air-fuel mixture on the side of the spark plug 30, particularly in the case of a lean air-fuel mixture, since ignition is ensured and a stable combustion action is obtained. Therefore, in the present embodiment, as shown in the drawing, the wall thickness of the partition wall 11c on the side away from the spark plug 30 (left side in the figure) is increased upward so that the spark plug of the first dividing passage 11a on the upper side of the partition wall 11c. The close passage area is enlarged. As a result, the air-fuel mixture becomes a tumble flow biased toward the spark plug, and the ratio of the air-fuel mixture existing in the vicinity of the spark plug increases, so that the ignitability is improved and a stable combustion action is obtained.
[0023]
FIG. 5 shows another shape example of the intake passage of the intake port portion. In this example, the thickness of the partition wall 11c in the intake port 11 portion is constant, and the shape of the first divided passage 26 on the upper side is formed so that the passage area closer to the spark plug (right side in the figure) becomes wider. As a result, as in the example of FIG. 4, the air-fuel mixture flowing through the first divided passage 26 gathers closer to the spark plug, improving the ignitability and obtaining a stable combustion action.
[0024]
FIG. 6 is a configuration diagram of an engine according to another embodiment of the present invention.
In this embodiment, the present invention is applied to a four-cycle four-valve engine 31.
[0025]
The engine 31 has a cylinder block 32 and a cylinder head 33, and a piston 34 slides in the cylinder block 32. The cylinder head 33 is formed with two intake ports 35 (only one shown) and two exhaust ports 36 (only one shown), to which an intake valve 37 and an exhaust valve 38 are mounted, respectively. Each intake valve 37 and exhaust valve 38 are opened and closed by an intake cam 39 and an exhaust cam 40 connected to a crankshaft (not shown). The two exhaust ports 36 merge and are connected to the exhaust pipe 41. Similarly, the two intake ports 35 merge and are connected to the intake pipe 42. A downdraft type carburetor 43 is connected to the intake pipe 42. An intake passage 51 is formed by communicating each intake port 35, the intake pipe 42 and the carburetor 43. The carburetor 43 has a butterfly throttle valve 44 including a butterfly valve body 50 fixed to the valve shaft 49 in the intake passage 51.
[0026]
In the engine 31 having such a configuration, the intake passage 51 on the downstream side of the throttle valve 44 is divided into two by the partition wall 46, and the first divided passage 47 and the second divided passage 48 are divided as in the embodiment of FIG. Form. In addition, the partition wall 46 is provided, and a weir 45 for closing the second divided passage 48 on the low throttle opening side is provided along the end of the valve body 50 of the throttle valve 44 in the same manner as the embodiment of FIG. Provide. The partition wall 46 also extends into the intake port 35 after being divided into two. The configurations and operational effects of the weir 45 and the partition wall 46 are the same as those in the above-described embodiment.
[0027]
The present invention is not limited to an engine provided with a carburetor, and can also be applied to an engine in which fuel is injected by a fuel injection valve and the intake air amount is controlled by a butterfly throttle valve.
[0028]
In the case of a four-valve combustion chamber, the spark plug is at the center of the combustion chamber, and the intake air may flow into the two intake ports after branching in the same manner.
[0029]
【The invention's effect】
As described above, in the present invention, the intake passage is divided into two parts by dividing the intake passage, and the weir is provided in the second divided passage that communicates with the edge of the combustion chamber. At this time, the second divided passage is closed and intake air is introduced into the combustion chamber only from the first divided passage. As a result, a tumble flow can be generated in which the air-fuel mixture is sucked from the combustion chamber center side toward the exhaust valve side during the low load operation and becomes a vertical flow. As a result, a tumble flow forming function can be obtained with a simple structure without using a movable mechanism, and there is no need for troublesome adjustment work. High functionality is stably maintained.
[0030]
As a result, lean combustion particularly at low loads is performed efficiently and stably, and fuel efficiency and exhaust emission are improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an engine according to an embodiment of the present invention.
FIG. 2 is an inner surface view of an intake passage taken along a line II-II in FIG.
FIG. 3 is a diagram showing a full throttle state according to the embodiment of FIG. 1;
FIG. 4 is a diagram showing an example of a cross-sectional shape of a partition wall.
FIG. 5 is a diagram showing another example of the cross-sectional shape of the partition wall.
FIG. 6 is a configuration diagram of an engine according to another embodiment of the present invention.
[Explanation of symbols]
1: engine, 2: cylinder, 3: cylinder head, 4: piston,
5: camshaft, 6, 7: rocker arm, 8: intake valve, 9: exhaust valve,
10: combustion chamber, 11: intake port, 12: exhaust port, 13: exhaust pipe,
14: intake pipe, 15: carburetor, 16: intake passage, 17: diaphragm chamber,
18: Jet needle, 19: Main jet, 20: Venturi section,
21: Pilot screw, 22: Valve shaft, 23: Valve body,
24: throttle valve, 25: partition, 26: first divided passage,
27: second divided passage, 28: weir, 29: groove, 30: spark plug,
31: Engine, 32: Cylinder block, 33: Cylinder head,
34: piston, 35: intake port, 36: exhaust port, 37: intake valve,
38: exhaust valve, 39: intake cam, 40: exhaust cam, 41: exhaust pipe,
42: intake pipe, 43: carburetor, 44: throttle valve, 45: weir, 46: partition,
47: first divided passage, 48: second divided passage, 49: valve stem, 50 valve body.

Claims (3)

In the intake passage structure of the engine provided with a butterfly type throttle valve in the intake passage communicating with the intake port facing the combustion chamber,
The intake passage on the downstream side of the throttle valve is divided into two by a partition parallel to the valve shaft of the throttle valve to form first and second divided passages,
The first divided passage is formed so as to face the intake port on the center side of the combustion chamber,
The second divided passage is formed so as to face the intake port on the edge side of the combustion chamber,
Along the valve body end of the lower opening side of the second divided passage side of the throttle valve, provided with a weir for the intake restriction projecting toward the center side of the intake passage from the wall surface of the second divided path Become
The engine intake passage structure according to claim 1, wherein the weir has a shape along a locus of a rotation end of the valve body of the throttle valve, and is provided on the downstream side of the valve shaft .   2. An intake passage structure for an engine according to claim 1, wherein a groove for fuel escape is formed in a central portion of the weir.   3. The engine according to claim 1, wherein the partition wall is provided in the vicinity of the valve shaft, and is provided in the vicinity of the valve shaft so as to be offset further to the open side than the valve body in the fully open position. Intake passage structure.

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