JPS6125914A - Intake-air device in four-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to uniformly feed intake-air from a plurality of intake- air ports to enhance the efficiency of air-intake, by communicating a primary intake- air passage with a secondary intake-air passage through a communication passage, and by forming the opening position of the communication passage with respect to the secondary intake-air passage at a position just before the intake ports. CONSTITUTION:Upon low and middle load operation a vacuum responding type piston valve 22 opens a passage 21. Accordingly, mixture created in a forcedly opening and closing type carburettor 11 alone is fed into a combustion chamber 4 through a primary intake-air passage 9 and one of intake-air ports 5. Further, when a piston valve 15 in the carburettor 11 approaches its full-close position, the piston valve 22 and a throttle valve 23 in a vacuum responding type carburettor 12 are started to be opened. In this case, even if the vacuum in a secondary intake-air passage 10 is high as just before opening of the piston valve 22, the vacuum in the opening port 30b part of a communication passage 30 between the primary and secondary intake-air passages 9, 10 with respect to the secondary intake-air passage 9, may be held to be low. Accordingly, intake-air may be uniformly fed from a plurality of intake-air ports.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a combustion chamber with a plurality of intake passages connected to a single combustion chamber.
The present invention relates to a cycle internal combustion engine, and particularly to the structure of its intake passage.

[Technical background of the invention and its problems]

As this type of intake device, for example, Japanese Patent Application Laid-Open No. 56-2074
As shown in Publication No. 7, a forced opening/closing type carburetor linked to the throttle is provided in the primary intake passage connected to the combustion chamber, and a forced opening/closing type carburetor linked to the throttle is provided in the other secondary intake passage. A negative pressure response type carburetor is installed, and only the forced open/close type carburetor is operated during low to medium load operation with little throttle opening, and in response to the increase in suction negative pressure accompanying the transition to high load operation, A device in which the other negative pressure responsive vaporizer is also operated is known.

By the way, in this device, during the transition period from low to medium load operation to high load operation, that is, just before the negative pressure responsive carburetor is opened, the intake air flows only through the primary intake passage, so the flow rate of the intake air is Although it was expensive, there was still room for improvement in increasing inhalation efficiency. Therefore, as an improvement measure, the above-mentioned intake passages are communicated between each carburetor and the intake port opening into the combustion chamber, and through this communication passage, a part of the intake air flowing in the primary side intake passage is transferred to the secondary side intake. It has been considered to supply the above-mentioned intake air to the combustion chamber from both intake passages by guiding it into the passage.

However, in this case, until the negative pressure responsive carburetor opens,
Since the flow velocity of the intake air in the secondary intake passage is slow, the negative pressure is correspondingly high. Therefore, simply connecting both intake passages will not allow the intake air in the primary intake passage to flow into the secondary intake passage. It becomes difficult to enter. Therefore, since most of the intake air still flows only through the primary intake passage, this has not been an effective improvement measure for increasing intake efficiency.

[Purpose of the invention]

The present invention was made based on these circumstances,
An object of the present invention is to provide an intake position a for a four-stroke internal combustion engine that can supply intake air approximately equally from both intake ports during the transition period when a negative pressure responsive carburetor is opened, thereby increasing intake efficiency. purpose.

[Summary of the invention]

That is, in order to achieve the above object, the present invention communicates the primary side intake passage and the secondary side intake passage with each other between the respective carburetors and the intake port opening into the combustion chamber, and at least two of the communication passages communicate with each other. The present invention is characterized in that the opening position for the next-side intake passage is provided immediately before the intake port.

(Embodiment of the Invention) The present invention will be described below based on an embodiment shown in the drawings.

In Figure 1, 1 is the cylinder block, 2 is the cylinder head,
3 indicates a piston, and the cylinder head 2 has a piston 3.
A combustion chamber 4 is formed correspondingly. Combustion chamber 4 has 2
intake ports 5.5 and exhaust ports 6.6 are opened, and these intake ports 5, 5 and exhaust ports 6.6 are opened at predetermined timings by an intake valve 7.7 and an exhaust valve 8.8. It is designed to be opened and closed.

A primary intake passage 9 and a secondary intake passage 10 are connected to the intake ports 5 and 5 separately, and both intake passages 9
．． 10 are communicated with the combustion chamber 4 independently from each other. A forced open/close type carburetor 11 set for low and medium speeds is connected to the upstream end of the primary side intake passage 9, and a forced open/close type carburetor 11 set for high speeds is connected to the upstream end of the secondary side intake passage 10. A negative pressure-responsive carburetor 12 is connected thereto. As shown in FIG. 3, the forced opening/closing type carburetor 11 has a passage 14 connected to the primary intake passage 9 in the carburetor main body 13, and a piston valve 15 that changes the venturi diameter in this passage 14. is connected to a throttle through a throttle lever 16 and a throttle wire (not shown), and is forcibly opened and closed in conjunction with the throttle operation. And this piston valve 15
A needle valve 17 is suspended from the main nozzle 19, and the needle valve 17 is inserted into a main nozzle 19 that opens below the oil level in the float chamber 18.

Further, as shown in FIG. 1, the negative pressure responsive carburetor 12 has a passage 21 connected to the secondary intake passage 10 in the carburetor main body 20, and there is a passage 21 in the upstream side of the intake passage 21. Negative pressure responsive piston valve 22 that changes the venturi diameter from the side
and a butterfly-type throttle valve 23 are provided in this order. The throttle valve 23 is controlled to open and close in conjunction with throttle operation, and is opened when the piston valve 15 of the forced opening/closing type carburetor 11 reaches a high opening range where it is opened more than a certain opening degree. It is now possible to do so. By opening and closing this piston valve 15, the passage 2
The opening area of No. 1 is adjusted to increase or decrease, thereby controlling the amount of intake air. On the other hand, the negative pressure responsive piston valve 22 is
The inside of the diaphragm case 24 is divided into an atmospheric pressure chamber 25 and a negative pressure chamber 26.
This atmospheric pressure chamber 25 is connected to the upstream side of the negative pressure responsive piston valve 22, and the negative pressure of a portion of the venturi is introduced into the negative pressure chamber 26. It has become. Therefore, the negative pressure responsive piston valve 22 is opened and closed based on the pressure difference between the atmospheric pressure chamber 25 and the negative pressure chamber 26, regardless of the throttle operation. The needle valve 32 hanging down from the negative pressure responsive piston valve 22 is inserted into the main nozzle 28, and the main nozzle 28 is connected to the fuel supply path 29.
It communicates with the float chamber 18 of the forced opening/closing type vaporizer 11 through the above.

The primary side intake passage 9 and the secondary side intake passage 10, to which the carburetors 11 and 12 of different types are connected, are communicated between the intake ports 5, 5 and the carburetors 11 and 12, respectively. The communication passage 30 of this embodiment is provided in the cylinder block 2, and the openings 30a and 30b for both intake passages 9, 10 are located immediately in front of the intake ports 5, 5.

Note that the reference numeral 31 in the figure is an exhaust passage connected to the exhaust port 6.6.

Next, the operation of the above configuration will be explained.

During low to medium load operation with a small throttle opening, the negative pressure in a portion of the venturi and the pressure on the upstream side of the negative pressure responsive piston valve 22 are balanced, so the piston valve 22 closes the passage 21. No mixture is formed. Therefore, only the air-fuel mixture (intake air) generated by the forced opening/closing type carburetor 11 is supplied into the combustion chamber 4 through the primary side intake passage 9 and one intake port 5. When the piston valve 15 of this carburetor 11 approaches the fully open position, the negative pressure responsive carburetor 1
As the throttle valve 23 of No. 2 begins to open, the negative pressure in a part of its venturi also decreases in accordance with the increase in intake flow rate due to the increase in engine speed, and as a result, the pressure in the negative pressure chamber 26 decreases. , the negative pressure responsive piston 22 is operated to open.

Therefore, in addition to the forced opening/closing type carburetor 11, the air-fuel mixture generated by the negative pressure responsive type carburetor 12 is supplied into the combustion chamber 4 through the secondary side intake passage 10 and the other intake port 5. More air-fuel mixture is supplied to the combustion chamber 4, improving intake efficiency.

By the way, in the above configuration, the primary side intake passage 9 and the secondary side intake passage 10 are connected to the intake ports 5, 5 and the carburetor 11.
12, and the opening 30b of this communication passage 30 to the secondary intake passage 10 is located just before the intake port 5, so that the secondary side Even when the negative pressure in the side intake passage 10 is high, the negative pressure at the opening of the communication passage 30 to the secondary intake passage 10 is kept low. That is, when the intake valve 7 opens, the closer to the intake port 5 the faster the flow rate of intake air is, so the force negative pressure is lower, and therefore, even during the transition period when the negative pressure responsive piston valve 22 is opened, the primary The air-fuel mixture flowing in the side intake passage 9 can more easily flow into the communication passage 30. As a result, the air-fuel mixture generated in the forced opening/closing type carburetor 11 is distributed almost equally to the two intake ports 5, 5,
When the intake valve 7.7 opens, the air is drawn into the combustion chamber 4 through these two intake ports 5.5, so that the intake efficiency is significantly improved and high output is obtained.

In addition, according to this configuration, since it is sufficient to simply connect both intake passages 9 and 10 with the communication passage 30, there is no need for a complicated movement mechanism, and therefore there are advantages such as low cost and high durability. be.

In addition, in the above-mentioned embodiment, the openings of the communication passages for both intake passages were both located near the intake port;
For example, as shown by the imaginary line in FIG. 2, the position of the opening 30a relative to the primary intake passage 9 in the communication passage 30 is shifted to the side of the carburetor 11 upstream from just before the intake port 5, and both intake passages 9.1 The inner circumferential surface of the communication passage 30 may be formed into a tapered surface that tapers toward the secondary intake passage 10.

Furthermore, the internal combustion engine according to the present invention is not limited to a so-called 4-valve engine with two intake valves and two exhaust valves, but can be similarly implemented in a 3-valve engine with one exhaust valve.

〔Effect of the invention〕

According to the present invention described in detail above, even when the negative pressure in the secondary intake passage is high, such as immediately before the negative pressure responsive carburetor opens,
Since the opening of the communication passage to the secondary intake passage is located just before the intake port where the intake air flow rate is high, the negative pressure in the opening is kept low, and therefore the negative pressure responsive carburetor is not opened. Even during the transitional period of operation, the air-fuel mixture flowing in the primary side intake passage tends to flow into the communication passage. As a result, the air-fuel mixture generated by the forced opening/closing carburetor is distributed almost equally to the two intake ports, and when the intake valve opens, it is drawn into the combustion chamber from these two intake ports, resulting in improved intake efficiency. This has the advantage of significantly improving fuel efficiency, producing high output, and contributing to improved fuel consumption.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a sectional view of the entire intake system, FIG. 2 is a partially sectional plan view of the cylinder head, FIG. 3 is a sectional view of a forced opening/closing carburetor, and FIG. FIG. 4 is a partially sectional front view of both carburetors. 4... Combustion chamber, 5... Intake port, 9... Primary side intake passage, 10... Secondary side intake passage, 11... Forced opening/closing type carburetor, 12... Negative pressure response Type vaporizer, 30...
・Communication path, 30a. 30b...Opening.

Claims (1)

[Claims] A forced opening/closing system in which a primary side intake passage and a secondary side intake passage are communicated with each other independently in a single combustion chamber, and the primary side intake passage is forcibly opened/closed in conjunction with throttle operation. In addition to installing a type carburetor in the other secondary side intake passage, when the opening degree of the forced opening/closing type carburetor reaches a higher opening range than expected,
In a four-stroke internal combustion engine equipped with a negative pressure responsive carburetor that is opened in response to intake negative pressure, the primary intake passage and the secondary intake passage are mutually opened to the respective carburetors and the combustion chamber. An intake system for a four-stroke internal combustion engine, characterized in that the communication passage communicates with an intake port, and an opening position of the communication passage with respect to at least the secondary intake passage is provided immediately before the intake port.