JPH036329B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an internal combustion engine using a carburetor, which is equipped with an intake passage for generating an intake swirl in a combustion chamber. It is related to the device.

(Prior Art) As is well known, there are two types of internal combustion engines: those using a carburetor and those using fuel injection valves without using a carburetor. Any of these types is required to purify exhaust gas and improve fuel efficiency. For this reason, EGR (exhaust gas recirculation) and lean burn are often performed, but in order to satisfy the requirements of both high-volume EGR and lean burn while preventing combustion fluctuations from causing misfires, it is necessary to increase the combustion speed. It has been known. As one means for increasing the combustion speed, it is said to be effective to generate a swirl inside the combustion chamber during combustion. Therefore, as a specific method to generate vortices, the intake passage is divided into a secondary passage that serves as the main intake passage and a primary passage that serves as the auxiliary intake passage, and air is mixed from this primary intake passage into the combustion chamber during intake. There is a technique to eject ki.

JP-A-54-84128 discloses a technology for an internal combustion engine in which an intake passage is divided into a primary side and a secondary side, and a mixture is injected from the primary side intake passage into a combustion chamber. The technique described in this publication uses a fuel injection valve, and this fuel injection valve is provided in the intake passage on the primary side. By installing the fuel injection valve in the intake passage on the primary side, it can be used frequently.
In addition, it maintains good fuel distribution and fuel atomization in the low and medium speed ranges, where combustion conditions have a significant impact on drivability and exhaust performance, and prevents deterioration of full-throttle output in the high speed range, where combustion conditions themselves are good. This is what I did.

(Problems to be Solved by the Invention) The technology described in the above publication uses a fuel injection valve in the internal combustion engine, and by providing the fuel injection valve in the intake passage on the primary side, It is possible to obtain good combustion conditions in both the medium speed range and the high speed range. However, for internal combustion engines that do not use fuel injection valves, the technique described in this publication cannot be applied, so it is necessary to use some other structure to achieve the same effect.

The present invention has been made in view of this point,
In an internal combustion engine that uses a carburetor without a fuel injection valve, the amount of air-fuel mixture that is appropriate for each of the operating conditions of the engine, i.e., idling, low-load operation, medium-load operation, and high-load operation. The problem to be solved is to provide an internal combustion engine that can supply a large amount of EGR and generate strong swirl during low-load operation where it is highly necessary to generate swirl in order to perform a large amount of EGR. It is something to do.

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides an internal combustion engine using a carburetor, in which a two-barrel carburetor 9 is used as the carburetor, and its primary passage 11
A primary throttle valve 24, which is a butterfly valve, is rotatably provided, and partition walls 25, 26, and 27 are provided extending from the rotation shaft 23 of the primary throttle valve 24 to a portion immediately before the main intake valve 15. The downstream side of the primary throttle valve 24 is branched into two, a low load passage 28 and a medium load passage 29, and the medium load passage 29 of the two branched passages 28 and 29 is connected to the main intake valve of the combustion chamber 4. 15
The middle load passage 29
A protrusion 30 is formed in the passage immediately downstream of the primary throttle valve 24, the end of which comes into contact with the primary throttle valve 24 from the time of closing to the opening corresponding to the medium load state of the engine. A sub-intake valve 31 independent from the main intake valve 15 is provided in the middle of the low-load passage 28 divided by the partition wall 27, and at the outlet end of the low-load passage 28 provided with the sub-intake valve 31, The low load passage 2
The structure includes a directing member 33 for directing the intake air from 8 in the direction along the inner wall of the cylinder (in the direction of arrow A).

(Function) With such a configuration, continuous partition walls 10, 13, 14 from the carburetor 9 to the cylinder head 2
and the combustion chamber 4 from the rotation shaft 23 of the primary throttle valve 24.
The medium load passage 29 is clearly defined from other passages by the partition walls 25, 26, 27 leading to it. Therefore, when the internal combustion engine is in an idling state, the least amount of air-fuel mixture suitable for that state is supplied to the combustion chamber, and during low-load operation, a larger amount of air-fuel mixture is supplied to the combustion chamber than when the engine is idling. Furthermore, during medium-load operation, an even larger amount of air-fuel mixture is supplied to the combustion chamber, and during high-load operation, an even larger amount of air-fuel mixture is supplied to the combustion chamber. The directing member 33 makes it possible to generate a strong swirl during low-load operation when it is highly necessary to generate a swirl.

(Example) Hereinafter, an example of the present invention will be described based on FIG. 1. 1 is a cylinder, 2 is a cylinder head, 3 is a piston, and 4 is a combustion chamber.
A main intake port 5, a sub-intake port 6, and an exhaust port 7 formed in the cylinder head 2 are open. The main intake port 5 and the sub-intake port 6 are connected to each other via an intake manifold 8.
Two-barrel carburetor (hereinafter referred to as
(referred to as a vaporizer) 9. In this carburetor 9, the reference numeral 10 is a partition, the part 11 is a primary passage partitioned by the partition 10, and the part 12 is a secondary passage.

A partition wall 13 is also provided within the intake manifold 8 and is connected to a partition wall 10 of the carburetor 9 . Furthermore, a partition wall 14 is also provided within the cylinder head 2 and is connected to the partition wall 13. These bulkheads 1
0, 13, and 14 define a path from the carburetor 9 to the combustion chamber 4 into a primary passage 11 and a secondary passage 12. A main intake valve 15 is disposed within the secondary passage 12 and is driven to open and close by a well-known valve operating mechanism comprising a cam 16, a rocker arm 17, a return spring 18, and the like. A rocker arm 20 for driving the exhaust valve 19 is also in contact with the cam 17 . 21 is a spark plug.

Immediately downstream of the bench lily portion 22 provided in the primary passage 11 in the carburetor 9, a primary throttle valve 24, which is a butterfly valve that rotates about a rotation shaft 23, is provided. And this rotation axis 2
The partition wall 25 in the carburetor 9 extends from the part 3 to the part facing the combustion chamber 4, which is the part immediately before the main intake valve 15.
A partition wall 26 in the intake manifold 8 and a partition wall 27 in the cylinder head 2 are connected to each other, and the partition walls 25, 26, 27 divide the primary passage into a low load passage 28 and a medium load passage 29. , the medium-load passage 29 opens immediately before the main intake valve 15 of the combustion chamber 4.

Next, the features of the present invention will be explained. In the intake device of the present invention, the medium load passage 2 in the carburetor 9
A protrusion 30 that protrudes into the medium load passage 29 is formed immediately downstream of the primary throttle valve 9 .
This protrusion 30 has a size and shape, and is positioned so that the primary throttle valve 24 does not separate from its end from the time of closing to the opening corresponding to the medium load state of the engine. ing. As a result, the opening degree of the medium load passage 29 is regulated. An auxiliary intake valve 31 that is separate from the main intake valve 15 provided in the secondary side passage is installed in the middle part of the low-load passage 28 (the part of the cylinder head 2 and a certain distance from the combustion chamber 4). is provided.

This sub-intake valve 31 is also driven to open and close by the rocker arm 17 at the same time as the main intake valve 15 . 32
is a return spring of the sub-intake valve 31. At the outlet end of the low load passage 28 provided with the auxiliary intake valve 31, intake air from the low load passage 28 is connected to the cylinder 1.
direction along the inner wall of the cylinder (indicated by arrow A in FIG.
A directing member 33 is provided for directing in the direction of This directing member 33 is integrally attached to the lower end of the partition wall 26, and when the air-fuel mixture enters the combustion chamber 4 from the partition wall 26 along the directing member 33, the flow is as indicated by arrow A in FIG. As shown, it has a shape that follows the inner wall of the cylinder 1. In the figure, the reference numeral 34 is a secondary throttle valve, and 35 is its rotation axis.

In the internal combustion engine described above, the exhaust system path and the main intake passage are connected via an EGR valve (not shown), but since the configuration of this EGR part is the same as that of conventional ones, the explanation will be limited to Omitted.

Next, the operation of the intake system for the internal combustion engine configured as described above will be explained in relation to the operating conditions of the engine.

During idling, the secondary throttle valve 34 of the carburetor 9 is fully closed, the primary throttle valve 24 is slightly opened at an opening suitable for idling, and the low-load passage 28 is connected to an idling port (not shown). Fuel for idling and a commensurate amount of air are supplied. These fuel and air become a mixture, and there is a risk that a part of it may leak to the medium load passage 29 side, but the upper end of the partition wall 25 is in contact with the rotation shaft 23 of the primary throttle valve 24; Also, since the protrusion 30 is formed in this medium load passage 29 and is in contact with the end of the primary throttle valve 24, there is almost no leakage and the water is supplied only to the low load passage 28 side. and auxiliary intake valve 3
1 opens, high intake negative pressure during idling acts on the air-fuel mixture, which is directed by the directing member 33 in the direction along the inner wall of the cylinder 1 (in the direction of arrow A in FIG. 2). It is sucked into the combustion chamber 4.

In this way, most of the air-fuel mixture flows into the combustion chamber 4 from the low-load passageway 28 having a small effective opening area.
Since the fuel is inhaled into the combustion chamber 4, it is sufficiently directed in a certain direction (the direction of arrow A in FIG. 2) by the directing member 33, forming a swirl shape within the combustion chamber 4, and stable combustion is performed. The secondary throttle valve 31 is the same Rocker arm 17 as the primary throttle valve 15
By being driven by the main intake valve 15, the injection timing of the air-fuel mixture matches the opening/closing timing of the main intake valve 15.

During low load operation, the primary side throttle valve 24 begins to open clockwise in the figure, and its opening becomes somewhat larger than during idling. As a result, the medium load passage 29 also begins to open slightly, but most of the air-fuel mixture flows into the low load passage 28 due to the influence of the protrusion 30, from where it is supplied to the combustion chamber 4, and the air-fuel mixture is supplied to the combustion chamber 4 with a larger flow rate than during idling. , generating a strong swirl within the combustion chamber 4.

During medium load operation, the secondary throttle valve 34 remains closed, but the opening degree of the primary throttle valve 24 increases, so the primary throttle valve 24 gradually separates from the protrusion 30, thereby causing The air-fuel mixture flows into both the low-load passage 28 and medium-load passage 29 that are branched from the primary passage 11. Therefore, the air-fuel mixture that has passed through both of these passages 28 and 29 is sucked into the combustion chamber 4. At this time as well, the air-fuel mixture that has passed through the low-load passage 28 is directed in a certain direction by the directing member 33 and is inhaled, resulting in a swirl. Since the swirl is restricted by the air-fuel mixture from the medium load passage 29 that is injected into the combustion chamber 4 from between the shoulder of the engine and the shoulder, the swirl is somewhat weakened.

During high-load operation, both the primary throttle valve 24 and the secondary throttle valve 34 open forward. As a result, the protrusion 30 does not affect the low load passage 28, so
The air-fuel mixture flows through the low-load passage 28 of the primary passage 11;
It is supplied to the combustion chamber 4 through all of the medium load passage 29 and the secondary passage 12.
The air-fuel mixture is also supplied to the combustion chamber 4 from the low-load passage 28 during this high-load operation and during the above-mentioned medium-load operation, but the low-load passage 28 has a small effective opening area and a large intake resistance. Therefore, most of the mixture is in the medium load passage 29 and the secondary passage 1.
2, and for the reasons explained above during medium load operation, the occurrence of swirl becomes weaker. During high-load operation, there is little residual gas in the combustion chamber 4, and the air-fuel ratio of the air-fuel mixture becomes low (rich).

(Effects of the Invention) Since the present invention is constructed and operates as described above, in an internal combustion engine of the type that uses a carburetor without using a fuel injection valve, the fuel is transferred from the carburetor 9 to the cylinder head 2. Continuous partition wall 10, 1
3, 14 and partition walls 25, 26, 27 extending from the rotating shaft 23 of the primary throttle valve 24 to the combustion chamber 4, the medium load passage 29 is clearly defined from other passages. That will happen. Therefore, when the internal combustion engine is in an idling state, the least amount of air-fuel mixture suitable for that state is supplied to the combustion chamber, and during low-load operation, a larger amount of air-fuel mixture is supplied to the combustion chamber than when the engine is idling. Furthermore, during medium-load operation, an even larger amount of air-fuel mixture is supplied to the combustion chamber, and during high-load operation, an even larger amount of air-fuel mixture is supplied to the combustion chamber. In these cases, the air-fuel mixture will be influenced by the directing member during low-load operation when the need to generate swirl is high.
At this time, there is an effect that a strong swirl can be generated.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is an explanatory view of the cylinder head side viewed from the piston side at the - line part in FIG. 1 to explain the flow direction of the air-fuel mixture. 1...Cylinder, 2...Cylinder head, 4...
...Combustion chamber, 9...Carburizer, 10, 13, 14, 2
5, 26, 27... Bulkhead, 11... Primary side passage,
12...Secondary side passage, 15...Main intake valve, 23...
...Rotation shaft, 24...Primary side throttle valve, 28...Low load passage, 29...Medium load passage, 30...Protrusion, 3
1...Sub-intake valve, 33...Directing member, 34...Secondary side throttle valve.

Claims (1)

[Claims] 1. In an internal combustion engine using a carburetor, a two-barrel carburetor is used as the carburetor, and a primary throttle valve, which is a butterfly valve, is rotatably provided in the primary passage of the carburetor, and the primary throttle valve is rotatable. A partition wall is provided from the shaft portion to the part immediately before the main intake valve, and the downstream side of the primary throttle valve is branched into two, a low load passage and a medium load passage, and the medium load passage of both the branched passages is divided into two. The combustion chamber is opened immediately before the main intake valve, and the medium load passage is located in the passage immediately downstream of the primary throttle valve, and corresponds to the medium load condition of the engine from the time the primary throttle valve is closed. A sub-intake valve separate from the main intake valve is provided in the middle of the low-load passage partitioned by the partition, and the sub-intake valve is connected to the main intake valve. An intake system for an internal combustion engine, characterized in that a directing member for directing intake air from the low load passage in a direction along an inner wall of a cylinder is provided at the outlet end of the low load passage.