JPS6337251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a four-stroke or two-stroke internal combustion engine for automobiles having a carburetor with a built-in throttle valve.

PRIOR ART In general, in spark ignition internal combustion engines, the valve opening required for the intake stroke is set to be large to increase the charging efficiency by drawing out the intake inertia effect, thereby increasing the output. On the other hand, however, in a low-speed rotation range where the intake inertia effect is small, the valve opening required for the intake stroke is relatively large, so air-fuel mixture blowback occurs and the filling efficiency decreases.

In order to prevent this air-fuel mixture from blowing back, spark ignition internal combustion engines have been developed in which a reed valve is provided in the intake passage leading from the carburetor to the combustion chamber, which has a throttle valve.

Problems to be Solved by the Invention Now, in this main conventional spark ignition internal combustion engine with a reed valve, there are systems other than the main fuel system that communicates from the fuel tank of the carburetor to the intake passage, such as a slow fuel system, a bypass starter system, etc. Because the is located near the throttle valve, it is not possible to operate under conditions where the intake air velocity is low or the difference in intake negative pressure relative to atmospheric pressure is small, such as when the accelerator is opened suddenly or when the engine speed is low despite the accelerator opening being large. , it was difficult for the fuel to be sucked out from the fuel tank of the carburetor, resulting in a thin air-fuel mixture, making it difficult to obtain smooth accelerator response and good engine combustion conditions.

Means and Effects for Solving the Problems The present invention relates to an improvement of an intake system for an internal combustion engine that eliminates such problems, and includes a reed valve in the downstream side of the carburetor of the intake passage leading from the carburetor to the combustion chamber. In the provided internal combustion engine, a bypass passage is formed that communicates from the upstream intake passage portion of the carburetor to the downstream intake passage portion of the carburetor, bypassing the intake passage of the carburetor, and the downstream end of the bypass passage is The present invention is characterized in that a branch passage that is opened at a reed valve seat portion that the tip of the reed valve abuts and that branches off from the bypass passage communicates with the carburetor fuel tank.

In the present invention, a bypass passage is formed from the upstream intake passage of the carburetor to the downstream intake passage of the carburetor by bypassing the intake passage of the carburetor, and the downstream side of the bypass passage is connected to the reed valve. Since the branch passage that opens at the reed valve seat portion that the tip comes into contact with and that branches from the bypass passage communicates with the carburetor fuel tank, when the opening degree of the reed valve is small, the bypass passage on the upstream side of the carburetor The pressure difference between the negative pressure due to the high-speed intake flow flowing near the downstream end opening of the bypass passage increases with respect to the pressure at the upstream end opening, and the bypass airflow flowing through the bypass passage becomes faster, and the air is removed from the carburetor fuel tank. Fuel is drawn into the bypass passage through the branch passage, and a rich air-fuel mixture is supplied to the intake passage from the downstream end opening of the bypass passage.

Therefore, in the present invention, when the intake airflow is slow and the intake negative pressure difference with respect to atmospheric pressure is small, such as when starting the engine with a small intake flow rate or when the full throttle is suddenly opened from a low speed range, the carburetor Even if the air-fuel mixture is lean, the amount of rich air-fuel mixture supplied to the bypass passage increases due to the increase in the flow rate in the bypass passage due to the small opening of the reed valve, so the amount of rich mixture supplied to the internal combustion engine increases. The concentration of the mixture is maintained at an appropriate level.

EXAMPLE Prior to describing an embodiment of the present invention illustrated in FIGS. 3 to 5 below, FIGS. The installation locations are shown with ○ marks when the method is applied.

Reference numeral 1 denotes a variable bench lily type carburetor with an air cleaner 4 connected to the suction side, and the discharge side of the carburetor 1 is airtightly connected to the valve body 7 of a reed valve 6 via a heat insulating material 5 made of resin, asbestos, or the like. The valve body 7 is airtightly connected to an intake passage (not shown) of a cylinder head 16 via an intake pipe 9.

Further, in the reed valve 6, the reed 10 and the stopper 11 are stacked in this order on the valve seat base end 8a of the valve body 7, and the base ends of the reed 10 and the stopper 11 are fixed together with a screw 13 via a washer 12. When there is no pressure difference between the intake passage 14a on the side of the valve body 7 and the intake passage 14b on the side of the intake pipe 9, the elasticity of the reed 10 brings the reed 10 into close contact with the valve seat of the valve body 7, and the supply The air passage 14 is designed to be blocked.

Furthermore, one end of a bypass passage 15 is opened toward the upstream side of the intake passage 14c on the upstream side of the carburetor 1, and the other end of the bypass passage 15 is opened at the valve seat tip 8b of the valve body. A branch passage 2 branched from 15 communicates with a fuel tank 3 of the carburetor 1.

Therefore, the carburetor side 15 of the bypass passage 15
a is arranged biased to one side directly below the intake passage 14, and is located on the valve seat tip side 15b of the bypass passage 15.
is deflected with respect to the center line of the intake passage 14 so as to be located directly below the intake passage 14 on the other side.

Since the embodiments shown in FIGS. 3 to 5 are configured as described above, in the operating state of the internal combustion engine in the medium to high speed range, the negative energy generated in the intake passage of the cylinder head 16 during the intake stroke The reed 10 moves away from the valve seat 8 and the reed valve 6 opens, and the air-fuel mixture generated in the carburetor 1 flows into the intake passage of the cylinder head 16 via the reed valve 6 and enters the combustion chamber ( (not shown). Even after the intake stroke ends, the air-fuel mixture is supplied to the downstream intake passage 14b of the reed valve 6 and the intake passage in the cylinder head 16 due to the intake inertia of the air-fuel mixture.
Reed valve 6 caused by air-fuel mixture intake inertia
intake passages 14a and 14b on the upstream and downstream sides of
When the pressure difference between the two cylinders is balanced, the reed 10 comes into close contact with the valve seat 8 and the reed valve 6 is closed, so the air-fuel mixture in the intake passage 14b downstream of the reed valve 6 and the intake passage in the cylinder head 16 is The air-fuel mixture is pressurized to a high pressure, for example, above atmospheric pressure, and the air-fuel mixture is smoothly supplied into the combustion chamber at the beginning of the next intake stroke, thereby achieving improvement in charging efficiency.

In addition, in the low speed rotation range, the intake passage 14 is connected to the lead 1 except during the intake stroke and the period immediately after it.
Since it is shut off at 0, blowing back of the air-fuel mixture is prevented.

Moreover, even when the engine is started or the throttle is suddenly opened from a low rotational speed range, the opening of the reed valve 6 is relatively small and the end of the bypass passage 15 is abruptly opened due to the separation of the reed 10. A large negative pressure is created at the end of the bypass passage 15 due to the synergistic effect of the opening and the high-speed mixture flow due to the narrow cross-sectional area of the mixture flow path between the valve seat tip 8b and the tip of the lead 10 near the end of the bypass passage 15. occurs, and a relatively large amount of fuel is supplied from the bypass passage 15 to the intake passage 14b on the downstream side of the reed valve 6, and as a result, the insufficient fuel supply due to the small intake air-fuel mixture flow rate is sufficiently compensated for.

Therefore, according to the embodiment described above, the startability of the engine can be greatly improved, and the accelerator response when the throttle is suddenly opened from a low speed rotation range can be significantly improved.

Furthermore, under normal operating conditions where the intake flow rate is high and its fluctuations are small, the intake passage 1 with the lead 10 narrowed
4a and 14b is small, and the pressure difference between the intake passages 14a and 14c sandwiching the carburetor 1 is also small, so the pressure difference between the upstream end opening of the bypass passage 15 and its downstream end opening is also small. 1
Bypass flow velocity and flow rate through 5 are reduced;
Excessive fuel supply is suppressed.

In this way, in the embodiment, without impairing the advantages of providing the lead valve 6,
Startability and accelerator response can be improved.

Furthermore, the bypass passage 15b on the side of the intake pipe 9
is deflected with respect to the center line in the intake passage 14, so the fuel injected from the bypass passage 15 forms a vortex and mixes with the air-fuel mixture flowing in the intake passage 14, so that the two are evenly mixed. , combustion within the combustion chamber is properly performed.

Effects of the Invention As described above, in the present invention, even if the intake flow rate to the internal combustion engine is small, the intake negative pressure difference with respect to atmospheric pressure is small, and the air-fuel mixture in the carburetor is thin, the reed valve opening is small. By increasing the flow rate in the bypass passage, the amount of rich air-fuel mixture supplied in the bypass passage increases, so starting performance and accelerator response are greatly improved.

In addition, in the present invention, when the air-fuel mixture in the carburetor is lean, the concentration of the air-fuel mixture to the internal combustion engine is maintained at an appropriate level by supplying the rich air-fuel mixture discharged from the bypass passage, and the intake air flow rate is further reduced. On the other hand, under normal operating conditions, the supply of rich mixture from the bypass passage is suppressed, maintaining the supply of mixture at an appropriate concentration to the internal combustion engine, and thus ensuring proper combustion in the engine. Fuel efficiency improves.

Further, since the present invention is constituted by a bypass passage and a branch passage communicating with the fuel tank, the structure is extremely simple and advantageous in terms of cost.

[Brief explanation of the drawing]

1 and 2 are side views of a 4-cycle or 2-cycle electrically ignited internal combustion engine to which the intake system for an internal combustion engine according to the present invention is applied, and FIG. 3 is a side view of an intake system for an internal combustion engine according to the present invention. FIG. 4 is a longitudinal sectional side view of a main part showing one embodiment, FIG. 4 is a view taken along the - arrow in FIG. 3, and FIG. 5 is an exploded perspective view thereof. 1... Carburetor, 2... Branch passage, 3... Fuel tank, 6... Reed valve, 7... Valve body,
8... Valve seat, 9... Intake pipe, 10... Lead, 1
1... stopper, 12... washer, 13... screw,
14...Intake passage, 15...Bypass passage.

Claims (1)

[Claims] 1. In an internal combustion engine in which a reed valve is disposed in a downstream portion of the intake passage leading from the carburetor to the combustion chamber, the intake passage bypasses the intake passage of the carburetor from the upstream intake passage portion of the carburetor to the downstream side of the carburetor. A bypass passage communicating with the side intake passage is formed, the downstream end of the bypass passage is opened at the reed valve seat portion that the reed valve tip comes into contact with, and a branch passage branching from the bypass passage is connected to the carburetor fuel. An intake passage for an internal combustion engine, characterized in that it communicates with a tank.