JPS6246698B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-cylinder internal combustion engine, and particularly to the structure of a carburetor and an intake pipe that supplies a mixture to each cylinder from the carburetor.

[Conventional technology and problems]

If the intake passage is long in an internal combustion engine with a carburetor,
Preheating of the inhaled air-fuel mixture is strengthened to improve fuel atomization, and there are also zones where the effects of inertial supercharging and pulsation become stronger, which can improve output. When the load is high, problems such as a decrease in output due to a decrease in charging efficiency and a decrease in responsiveness due to the long time it takes for the air-fuel mixture to reach the combustion chamber from the carburetor are caused.

As a prior art, there is Japanese Patent Application Laid-open No. 141811/1983.

The present invention was made in view of these circumstances, and in the low load range of engine operating conditions, the intake passage is lengthened to improve fuel atomization through preheating.
The object of the present invention is to provide a multi-cylinder internal combustion engine in which the intake passage is widened and shortened in a high load range to improve responsiveness and charging efficiency.

[Means for solving problems]

In order to achieve the above object, the present invention has two dual carburetors, a long intake passage from the primary side of the first carburetor and a short intake passage from the secondary side of the second carburetor. A short intake passage from the secondary side of the first carburetor and a long intake passage from the primary side of the second carburetor are connected to the intake port of the first combustion chamber. A cooling water passage is provided to communicate with the intake port of the combustion chamber and to preheat only the long intake passage.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. 1 and 2 show an example in which the present invention is applied to a horizontally opposed internal combustion engine, in which cylinder heads 2, 2' are installed on the left and right sides of the engine body 1,
The combustion chamber 3 of these cylinder heads 2, 2'
3', an intake port 4 bent in an L-shape from above,
4' are formed to communicate with each other, and an intake valve 5 is provided here to open and close. Two double carburetors 6 and 6' are provided above the engine body 1, and the left carburetor 6 is located right next to the right intake port 4' and near the left cylinder head 2, and the right carburetor 6 is located near the left cylinder head 2, The carburetor 6' is located directly beside the left-hand intake port 4 and near the right-hand cylinder head 2'.

By the way, the carburetor 6 has throttle valves 9, 10 and acceleration pump nozzles 11, 12 in the primary cylinder 7 and secondary cylinder 8, respectively, and the primary cylinder 7 is connected to the right intake port by a long intake passage 13. 4', and the secondary cylinder 8 communicates with the intake port 4 near the left side through a short intake passage 14, and these intake passages 1
3 and 14 communicate with each other through a bypass hole 15 immediately below the carburetor 6. Further, the other carburetor 6' is constructed in exactly the same manner, and in the same way, the primary cylinder 7' communicates with the left intake port 4 through a long intake passage 13', and the secondary cylinder 8' communicates with the left intake port 4 through a short intake passage 13'. ' communicates with the right intake port 4',
and has a similar bypass hole. The two long intake passages 13, 13' arranged in parallel in this way have a narrow passage diameter, and are designed to increase the flow velocity of the air-fuel mixture flowing therethrough and prevent the atomized fuel from adhering to the walls of the intake passage. The other intake passages 14, 14' are thicker to improve filling efficiency.

Furthermore, a bypass passage 22 is provided between the two intake passages 13, 13' for correcting the imbalance in each intake passage 13, 13' when air is taken in by the two carburetors 6, 6'. An EGR valve 16 is provided in the middle of this bypass passage 22.
The EGR passage 17 communicates with the exhaust gas to evenly distribute and supply the recirculating exhaust gas to each cylinder. A cooling water passage 18 for preheating is provided at the bottom of the two intake passages 13, 13' which are arranged in parallel in close proximity to each other, as shown in detail in FIG. One side communicates with the cooling water passage 19' of the cylinder head 2', and the other side communicates with the radiator via a thermostat 20 and a hose 21.

Since the present invention is configured in this manner, warm cooling water is always supplied to the cooling water passage 18 during engine operation.
By flowing through the two long intake passages 13, 1
3' is heated. Therefore, when there is no load or low load, the throttle valve 9 on the primary side of the carburetor 6, 6'
When the air-fuel mixture is supplied from the primary cylinders 7, 7' with the opening of It flows at high speed, is introduced into the intake ports 4', 4, and is supplied to the combustion chambers 3', 3.
In the process of flowing through the intake passages 13, 13' in this manner, the air-fuel mixture is preheated by the cooling water in the cooling water passage 18 located below. In addition, at this time, an unbalance due to a pressure difference between the air-fuel mixtures between the intake passages 13 and 13' due to the air-fuel mixture being supplied separately by the two carburetors 6 and 6' causes the air-fuel mixture to flow through the bypass passage 22 into the intake passage 13. , 13'.
A part of the air-fuel mixture 13' flows into the short intake passages 14, 14' through the bypass hole 15, and is quickly introduced to the opposite intake ports 4, 4' to ensure a certain degree of responsiveness. It will be destroyed.

Then, at medium or high loads, the throttle valves 9, 10 on the primary and secondary sides of the carburetors 6, 6' open and the air-fuel mixture is supplied from the primary and secondary cylinders 7, 7' and 8, 8'. Then, the mixture from the primary cylinders 7, 7' is the same as above, and the air-fuel mixture from the secondary cylinders 8, 8' immediately flows to the intake port 4 without being preheated by the short intake passages 14, 14'. , 4'. On the other hand, when the EGR valve 16 opens at this time, part of the exhaust gas uniformly flows into the intake passages 13 and 13' via the EGR passage 17 and the bypass passage 22, where it mixes with the air-fuel mixture and flows into the combustion chamber. Supplied.

Furthermore, during acceleration, fuel is ejected from the primary and secondary accelerator pump nozzles 11 and 12 of the carburetors 6 and 6', and fuel is ejected from the secondary accelerator pump nozzle 12 through the short intake passage. 14, 14' are quickly supplied. In addition, in the medium acceleration range using only the primary acceleration pump nozzle 11, the air-fuel mixture is supplied through both the intake passages 13 and 13' and the intake passages 14 and 14' formed by the bypass hole 15, ensuring a predetermined response. Ru.

Although the description has been made regarding a horizontally opposed type internal combustion engine, the present invention can be similarly applied to an in-line type or a V-type internal combustion engine.

〔Effect of the invention〕

As described above, according to the present invention, when the load is low, the air-fuel mixture is preheated in the long intake passages 13, 13', thereby improving fuel atomization and improving distribution to each cylinder and combustion efficiency. Also, at high loads,
Even with the short intake passages 14 and 14', the air-fuel mixture is quickly supplied, resulting in good responsiveness, and the large passage diameter and no preheating improve filling efficiency, resulting in increased output. . Since the diameter and length of each intake passage can be selected relatively freely, it is possible to make the optimal settings for each engine, and the EGR system is also simplified. Furthermore, intake passage 1
By integrally casting 3, 13', 14, 14', the cooling water passage 18, etc., it is possible to make it compact.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of an internal combustion engine according to the present invention, FIG. 2 is a partially sectional front view, and FIG. 3 is a cross-sectional view taken from FIG. 2. 1... Engine body, 4, 4'... Intake port,
6, 6'... Carburizer, 7, 7'... Primary cylinder, 8, 8'...
Secondary cylinder, 13, 13'...Long intake passage, 14, 1
4'...Short intake passage, 18...Cooling water passage.

Claims (1)

[Claims] 1 Has two double carburetors, with a long intake passage from the primary side of the first carburetor and a short intake passage from the secondary side of the second carburetor connected to the first combustion chamber. The short intake passage from the secondary side of the first carburetor and the long intake passage from the primary side of the second carburetor are connected to the intake port of the second combustion chamber, and the above-mentioned A multi-cylinder internal combustion engine characterized by having a cooling water passage attached only to the long intake passage for preheating.