JP2000329016A - Intake passage structure for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intake passage structure for an engine equipped with a butterfly type throttle valve, for stably opening/closing one side divided passage by simple structure without using a movable mechanism, by halving an intake passage by a partitioning wall. SOLUTION: In an intake passage structure for an engine 1, equipped with a butterfly type throttle valve 24 in an intake passage 16 communicated with an intake port 11 facing a combustion chamber 10; the passage 16 on the downstream side of the valve 24 is halved by a partitioning wall 25 in parallel to the valve shaft 22 of the valve 24, to form two first and second divided passages 26 and 27, and the passages 26 and 27 are formed so as to face the port 11 on the central or edge part side of the chamber 10 respectively, to provide a weir 28 for restricting intake air protruded from the wall surface of the passage 27, along the end part of a valve element 23 on the low opening side of the valve 24 on the passage 27 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intake passage structure for an engine, and more particularly to an intake passage structure for generating a tumble flow suitable for lean combustion.

[0002]

2. Description of the Related Art An intake passage communicating with an intake port facing a combustion chamber is partitioned by a partition, and one passage is communicated with an intake port at a central portion of the combustion chamber, and the other passage is communicated with an edge of the combustion chamber. At low load, the intake air is introduced into the combustion chamber from the side of the passage that communicates with the intake port at the center, increasing the intake flow velocity and causing a vertical tumble flow in the combustion chamber to stratify the lean mixture and stabilize it. An intake passage structure for performing lean combustion has been developed and proposed.

[0003] Such an intake passage structure divided into two by a partition wall uses a sliding-type throttle valve to correspond to the slide opening of the throttle valve according to the load. When the mixture is allowed to flow from only the other passage while the passage is kept closed, and the mixture is caused to flow from both passages when the slide opening is increased, the intake air flow rate can be increased at a low opening to generate a tumble flow.

[0004]

However, in the conventionally proposed two-partitioned intake passage structure, when a sliding throttle valve is used, one of the divided passages is closed according to the load. However, it cannot be directly applied to an intake passage provided with a butterfly type throttle valve. This is because intake air flows from around the throttle valve, so it is difficult to flow intake air only through one of the divided passages.

When a butterfly type throttle valve is used in a divided intake passage structure, a movable mechanism such as a control valve for opening and closing one of the passages must be used together.

However, if a movable mechanism is provided in the intake passage, the structure becomes complicated, adjustment is troublesome, and there is a possibility that the throttle valve may be out of synchronization due to long-term use, and stable intake control is difficult.

The present invention has been made in consideration of the above-mentioned prior art, and has a simple structure without dividing the intake passage into two by a partition in the intake passage equipped with a butterfly type throttle valve, and without using a movable mechanism. It is an object of the present invention to provide an engine intake passage structure that can open and close one of the divided passages stably.

[0008]

In order to achieve the above object, according to the present invention, there is provided an engine intake passage structure having a butterfly type throttle valve in an intake passage communicating with an intake port facing a combustion chamber. The intake passage on the downstream side of the throttle valve is divided into two by a partition wall parallel to the valve axis of the throttle valve to form first and second divided passages, and the first divided passage is located at the center 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 throttle valve end on the low opening side of the throttle valve on the second divided passage side is formed. , An intake-restriction weir that protrudes from the wall surface of the second divided passage is provided.

According to this structure, the intake passage is divided into two by the partition, and the weir is provided in the second divided passage which 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. This allows
During low load operation, the air-fuel mixture is taken in from the center of the combustion chamber of the intake valve toward the exhaust valve, and a tumble flow can be generated in the combustion chamber. As a result, the tumble flow forming function can be reliably obtained with a simple structure without using a movable mechanism, no troublesome adjustment work is required, and even after long-term use, there is no loss of synchronization with the throttle valve and reliability. High function is stably maintained.

In a preferred embodiment, a fuel escape groove is formed at the center of the weir.

According to this configuration, the fuel liquefied in the vicinity of the throttle valve does not accumulate in the weir but flows downstream through the groove provided in the weir and is vaporized by the heat of the intake pipe.

In a further preferred configuration example, the partition wall comprises:
It is provided near the valve shaft, and in the vicinity of the valve shaft, it is provided further offset from the valve element at the fully open position to the open side.

According to this configuration, since the partition wall is close to the valve shaft, there is no occurrence of leakage or backflow of intake air between the upstream end portion of the partition wall and the valve shaft. Further, since the partition wall close to the valve shaft is further offset toward the open side than the valve element at the fully open position, the operation of the throttle valve up to the fully open position is not hindered.

[0014]

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. This engine 1 has a cylinder 2 and a cylinder head 3 mounted on an upper part thereof, and a piston 4 slides in the cylinder 2. The engine 1 is a four-cycle two-valve engine, and includes a camshaft 5 connected to a crankshaft (not shown) at the center of a cylinder head 3. An intake-side rocker arm 6 and an exhaust-side rocker arm 7 that follow the cams 5a and 5b of the camshaft 5 in sliding contact therewith are provided. The rocker arms 6 and 7 open and close the intake valve 8 and the exhaust valve 9 in synchronization with the crank rotation. 8a and 9a are valve springs, respectively.

A combustion chamber 10 is formed above the cylinder 2 on the upper surface of the piston 4. An ignition plug (not shown) is mounted on the cylinder head 3 side facing the combustion chamber 10. The engine 1 of this example is a two-valve engine in which an intake valve 8 and an exhaust valve 9 are arranged close to each other at the center of the top of the combustion chamber 10, so that the spark plug is provided offset from the top of the combustion chamber 10. I have.

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 openably and closably mounted on the opening ends of the intake port 11 and the exhaust port 12 on the combustion chamber side.
The exhaust port 12 is connected to the exhaust pipe 13 and the intake port 1
1 is connected to the intake pipe 14. A carburetor 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.

The carburetor 15 drives the jet needle 18 attached to the free piston by the balance between the atmospheric pressure in the diaphragm chamber 17 and the intake negative pressure, and causes the venturi section 20 to suck the fuel through the main nozzle 19. A pilot screw 21 for adjusting fuel during idling and a bypass 21 a serving as a fuel outlet at low opening are provided downstream of the diaphragm chamber 17. A butterfly type throttle valve 24 in which a butterfly type valve element 23 is fixed to a valve shaft 22 is mounted in the intake passage 16 of the carburetor 15.

The intake passage 16 on the downstream side of the throttle valve 24
Is divided into upper and lower parts by a partition 25 parallel to the valve shaft 22. The partition 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 split passage 26 faces the intake port 11a at the center of the combustion chamber 10, and the lower second split passage 2
7 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 upper (central side) intake port (first split passage) 11a and a lower (edge side) intake port (first side) by a partition wall 11c integrally formed with the cylinder head 3. 2b).

In this embodiment, the throttle valve 24
Along the end of the valve body 23 on the low opening side, a weir 28 projecting from the passage wall surface of the second divided passage 27 is provided. Due to such a weir 28, when the throttle opening is small and the load is small, the air passing through the upper opening of the throttle valve shown in FIG. A fuel-air mixture is formed by the fuel from the bypass 21a,
Flow through the split passage. In addition, since the lower second divided passage 27 blocks the air flow by the weir, the air-fuel mixture flows into the upper first divided passage 27.
The fuel flows only through the split passage 26, and the combustion chamber 1 extends from the top of the combustion chamber at the open end of the intake port 11 toward the exhaust valve.
It flows into 0. Since the cross-sectional area of the intake passage is reduced to about 比 べ as compared with the case where there is no partition wall, the intake flow velocity is improved about twice. As a result, a vertical tumble flow in the fuel chamber as shown by an arrow A in the combustion chamber 10 is formed. Strong tumble leaves flow even during the compression stroke and improves combustion. As a result, stable combustion is possible even with a lean air-fuel mixture, thereby improving fuel efficiency.

FIG. 2 is an inner view of the intake passage viewed from the direction II-II in FIG. As shown, the aforementioned weir 28
A groove 29 is formed at the center of the groove. Even if fuel is liquefied on the upstream side of the weir 28, the fuel is supplied to the groove 29.
Flows into the downstream side intake passage, and is vaporized by the heat of the intake pipe 14 to be a mixture, and is sucked into the combustion chamber, so that it does not accumulate on the upstream side of the weir. Therefore, the air-fuel ratio supplied to the combustion chamber is stabilized.

FIG. 3 is a diagram of the above embodiment in a full throttle state. As shown in the drawing, 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 located above the valve body 23 in the fully opened state. Provided. By arranging the partition wall 25 above the valve shaft 22, the opening operation of the valve body 23 to the fully open position is not hindered, and a high flow rate is secured, so that the output can be maintained. As described above, the intake air flows from the first split passage at the time of the throttle low opening and from the second split passage at the time of the throttle high opening, so that a tumble stronger than that at the time of the high opening is obtained in the combustion chamber at the time of the low opening. . That is, a variable tumble according to the throttle opening can be obtained. For this reason, the intake port can be formed in a shape aimed at the flow coefficient, and high output can be achieved.

FIG. 4 shows an example of the sectional shape of the partition 25.
In a two-valve engine, the position of the spark plug 30 facing the combustion chamber 10 is offset somewhat laterally from the top. When the load is low, the air-fuel mixture is supplied only through the upper first split passage 26 in the intake passage as described above. Therefore, even in the intake port 11, the air-fuel mixture is supplied only through the first divided passage 11a above the partition wall 11c. In this case, it is preferable to concentrate the air-fuel mixture on the ignition plug 30 side, especially in the case of a lean air-fuel mixture, since ignition is ensured and a stable combustion action can be obtained. For this reason, in the present embodiment, as shown in the figure, the wall thickness of the partition wall 11c on the side remote from the ignition plug 30 (left side in the figure) is increased to the upper side, and the ignition plug of the first divided passage 11a on the upper side of the partition wall 11c is increased. The area of the nearby passage is enlarged. As a result, the air-fuel mixture becomes a tumble flow biased toward the ignition plug, and the proportion of the air-fuel mixture present near the ignition plug increases, so that the ignitability is improved and a stable combustion action is obtained.

FIG. 5 shows another example of the shape of the intake passage at the intake port. In this example, the partition 2 at the intake port 11 is used.
5, the thickness of the first divided passage 26 on the upper side is formed so that the passage area near the spark plug (right side in the figure) is increased. Thus, similarly to the example of FIG. 4, the air-fuel mixture flowing through the first split passage 26 is gathered near the spark plug, the ignitability is improved, and a stable combustion action is obtained.

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 an engine 31 of a four-cycle four-valve type.

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 has 2
One intake port 35 (only one is shown) and two exhaust ports 36 (only one is shown) are formed.
7 and the exhaust valve 38 are mounted. Each intake valve 37 and exhaust valve 38 are driven to open and close by an intake cam 39 and an exhaust cam 40 connected to a crankshaft (not shown). The two exhaust ports 36 join 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. Each intake port 35, intake pipe 42
In addition, an intake passage 51 is formed to communicate with the carburetor 43. The carburetor 43 has a butterfly type throttle valve 44 including a butterfly type valve body 50 fixed to a valve shaft 49 in the intake passage 51.

In the engine 31 having such a configuration,
As in the embodiment of FIG. 1 described above, the intake passage 51 on the downstream side of the throttle valve 44 is divided into two by a partition wall 46 to form a first divided passage 47 and a second divided passage 48. In addition to providing the partition wall 46, the weir 45 for closing the second divided passage 48 on the throttle low opening degree side is provided along the end of the valve body 50 of the throttle valve 44 similarly to the embodiment of FIG. Provide. The partition 46 is the intake port 35 after being divided into two.
It also extends inside. The configuration, operation, and effect of the weir 45 and the partition 46 are the same as those of the above-described embodiment.

The present invention is not limited to an engine having a carburetor, but is also applicable to an engine in which fuel is injected by a fuel injection valve and the amount of intake air is controlled by a butterfly throttle valve.

In the case of a four-valve combustion chamber, the ignition plug is located at the center of the combustion chamber, and the intake air may similarly flow into the two intake ports after branching.

[0029]

As described above, in the present invention, the intake passage is divided into two by the partition, and the weir is provided in the second divided passage communicating with the edge of the combustion chamber. When the throttle valve is at a low opening, the second divided passage is closed, and intake air is introduced into the combustion chamber only from the first divided passage. Thus, during the low load operation, the air-fuel mixture is sucked from the center of the combustion chamber toward the exhaust valve, and a tumble flow that forms a vertical flow can be generated. As a result, the tumble flow forming function can be reliably obtained with a simple structure without using a movable mechanism, no troublesome adjustment work is required, and even after long-term use, there is no loss of synchronization with the throttle valve and reliability. High function is stably maintained.

As a result, lean combustion particularly at a low load is performed efficiently and stably, thereby improving fuel efficiency and exhaust emission.

[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 view of an intake passage taken along a line II-II in FIG. 1;

FIG. 3 is a diagram showing a full throttle state of the embodiment of FIG. 1;

FIG. 4 is a diagram showing an example of a cross-sectional shape of a partition.

FIG. 5 is a diagram showing another example of the cross-sectional shape of the partition.

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, 21: Pilot Screw, 22: Valve Shaft, 23: Valve, 24: Throttle Valve, 2
5: partition wall, 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, 4
0: exhaust cam, 41: exhaust pipe, 42: intake pipe, 43: carburetor, 44: throttle valve, 45: weir, 46: partition, 4
7: first divided passage, 48: second divided passage, 49: valve shaft,
50 valve bodies.

Claims (3)

[Claims] 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 connected to a valve of the throttle valve. The first and second divided passages are formed by dividing into two by a partition wall parallel to the axis, the first divided passage is formed so as to face an intake port on the central portion side of the combustion chamber, and the second divided passage is formed. An intake port formed so as to face an intake port on the edge side of the combustion chamber, and protruding from a wall surface of the second split passage along an end of the throttle valve on the side of the second split passage on the low opening side. An intake passage structure for an engine, wherein a restriction weir is provided. 2. The intake passage structure for an engine according to claim 1, wherein a fuel escape groove is formed in a center portion of the weir. 3. The valve according to claim 1, wherein the partition wall is provided close to the valve shaft, and is provided near the valve shaft so as to be further offset to the open side than the valve body at the fully open position. An intake passage structure for an engine according to Claim 1.