JPH0558866U - Variable venturi vaporizer - Google Patents

Abstract

(57) [Summary] [Purpose] The engine in the idling speed range is prevented while preventing the internal combustion engine from generating run-on by adhering to the intake pipe wall when the air-fuel mixture ejected from the bypass port passes through the throttle valve. Prevents unstable rotation speed. [Constitution] Downdraft variable venturi type carburetor 1
Has a bypass port 7 upstream of the throttle valve 2 and a slow port 8 downstream thereof. The bypass longitudinal passage 10 is provided with a throttle 9 immediately upstream of the bypass port 7,
The relationship between the diameter A of the bypass port 7, the diameter B of the throttle 9 and the diameter C of the slow port 8 is defined as C <B << A.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an improvement of a variable venturi type vaporizer.

[0002]

[Prior Art]

 The conventional downdraft variable venturi type carburetor is provided with a bypass port that opens into the bore between the main nozzle and the throttle valve as a slow system port (for example, see Japanese Utility Model Publication No. 63-46662). And a slow port that opens in the bore downstream of the throttle valve (see, for example, Japanese Utility Model Laid-Open No. 55-12 1949).

[0003]

[Problems to be solved by the device]

 In the former of the above-mentioned conventional techniques, when the slow system air-fuel mixture ejected from the bypass port passes through the throttle valve, fuel is likely to adhere to the wall surface of the intake pipe. For this reason, it took a long time for the adhered fuel to enter the combustion chamber after the engine key was turned off, resulting in run-on.

In the latter of the above-mentioned conventional techniques, the slow port is provided so that the fuel of the slow system is directly ejected to the intake pipe, so that the wall flow disappears and the time to enter the combustion chamber of the engine is eliminated. Is less and no run-on occurs. However, regardless of load or no load, in the idling speed range, the engine intake pulsation affects the carburetor internal passage pressure from the slow port, and the mixture injection condition fluctuates, resulting in an unsatisfactory engine speed. There was a problem of becoming stable.

This is because in the variable venturi type carburetor, the negative pressure of the main system is small in the variable venturi type carburetor as compared with the general carburetor, so that it is more susceptible to the influence of intake pulsation. .. Therefore, an object of the present invention is to provide a down-draft variable venturi-type carburetor which prevents lions and stabilizes the jetting of a slow mixture to solve the above problems.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the variable venturi type carburetor of the present invention is a variable venturi type carburetor having a bypass port (7) and a slow port (8). A throttle (9) is provided in the position (10) just upstream of the bypass port (7), and the diameter A of the bypass port (7), the diameter B of the throttle (9), and the diameter C of the slow port (8). Is defined as C <B << A.

[0007]

[Action]

 Since the throttle (9) reduces the pulsating flow in the bypass vertical passage (10), the jet state of the slow system air-fuel mixture in the idling speed range is stabilized. In addition, the slow fuel is mainly ejected from the slow port (8), and run-on due to the fuel adhering to the wall surface is avoided.

[0008]

【Example】

 In FIG. 1, 1 is a variable venturi type carburetor, 2 is a throttle valve, 3 is a suction piston, 4 is a metering needle, 5 is a main jet, 6 is a main nozzle, 7 is an intermediate position between the main nozzle 6 and the throttle valve 2. By-pass port opening in the bore, 8 is a slow port opening in the bore downstream of the throttle valve 2, 9 is a throttle (jet), and is provided in the bypass vertical passage 10 just above the upper end of the bypass port 7.

In this embodiment, for example, the diameter A of the bypass port 7 is φ3.7, the diameter B of the throttle 9 is φ1.5, and the diameter C of the slow port 8 is φ1.2. When the engine is not loaded, the engine intake pulsation pressure is propagated from the small-diameter slow port 8 opened in the bore on the downstream side of the throttle valve 2 to the upstream part of the internal passage of the carburetor (for all main system and slow system), and the main nozzle 6 and the metering needle 4, the main jet 5 and the metering needle 4, and the main nozzle 6 The bypass vertical passage 10 downstream has a pulsating flow of the air-fuel mixture, but the presence of the throttle 9 As a result, the pulsating pressure is less likely to propagate upstream and is attenuated. FIG. 2 shows the pressure in the bypass vertical passage 10. In the prior art, the amplitude of the pulsation is large like the curve a, but in the embodiment of the present invention it is small like the curve b.

Therefore, the air-fuel mixture ejected from the slow port 8 is stabilized, and as a result, the engine speed in the idling speed range is stabilized. Although the throttle 4 is provided upstream of the bypass port 7 in the above embodiment, it may be provided in the slow passage 11 between the bypass port 7 and the slow port 8 or in the slow port 8.

[0011]

[Effect of the device]

 Since the variable venturi type carburetor of the present invention is configured as described above, it is possible to improve the stability of the engine speed under no load while preventing run-on of the internal combustion engine.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is a diagram showing the pressure in the bypass vertical passage.

[Explanation of symbols]

 2 Throttle valve 7 Bypass port 8 Slow port 9 Throttle 10 Bypass vertical passage

Claims (1)

[Scope of utility model registration request] 1. A downdraft variable venturi type carburetor comprising a bypass port (7) and a slow port (8) in a bypass vertical passage (10) immediately upstream of the bypass port (7). A diaphragm (9) is provided at the position, the diameter A of the bypass port (7) and the diameter B of the diaphragm (9).
And a diameter C of the slow port (8) is defined as C <B << A, a variable venturi-type vaporizer.