JPH01195955A - Automatic starter mechanism of carburetor - Google Patents

Abstract

PURPOSE:To properly maintain the air-to-fuel ratio by mounting both a throttle which communicates a diaphragm chamber with a float chamber and a check valve which permits fuel to flow only from the float chamber into the diaphragm chamber to increase the quantity of fuel supplied at the starting time. CONSTITUTION:A housing 2 is divided by both a partition wall 3 and a diaphragm 4 into a float chamber 2a and primary and secondary diaphragm chambers 2b and 2c. The partition wall 3 has both a throttle pipe 5 having a throttle 5a and a check valve 6 permitting fuel to flow only from the float chamber 2a into the primary diaphragm chamber 2b. Thus the increase in fuel supplied at the starting time may be ensured and the air-to-fuel ratio of mixture be maintained properly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to autostarter mechanisms for carburetors.

Conventionally, as an autostarter mechanism for a carburetor, for example, one based on the public shaft of JP-A-57-198350 has been known. According to this configuration, at the time of starting, the space above the liquid level inside the float chamber is The pressure inside the crank chamber is introduced into the space, but since there is a vent opening in this space,
The introduced pressure in the crank chamber leaks, making it unsuitable for taking advantage of the pulsed pressure increase that occurs when the engine is heated, and requiring an outlet for the crank chamber pressure, which increases cost. Furthermore, the function as a starter has the disadvantage that unnecessary negative pressure is also introduced. Furthermore, in the autostarter mechanism described in Japanese Patent Application Laid-open No. 51-83937, a main jet and an idle fuel supply pipe are arranged in a fuel reservoir that communicates with the float chamber through a passage, and a crankshaft is placed on the fuel surface of the fuel reservoir. The pulsating pressure generated within the case is applied to increase the amount of fuel supplied during acceleration, but in reality, when pulsating pressure is applied, the fuel in the fuel reservoir flows back from the passage to the float chamber. However, when the pulsating pressure supply is stopped after acceleration ends, the surface of the fuel in the fuel reservoir rises to its normal level due to the drop in pressure.
At this time, there was a drawback that the amount of fuel supplied temporarily decreased and the air-fuel ratio became too lean.

In view of the above points, the present invention makes it possible to effectively increase the amount of fuel supplied by using only the positive pressure among the high pressure generated in the crank chamber during the coiling of a 4-cycle engine, and to increase the supply of positive pressure. An object of the present invention is to provide an autostarter mechanism for a carburetor that can maintain an appropriate air-fuel ratio of an air-fuel mixture even when the carburetor stops.

Mutual! The purpose of this is to create a first diaphragm chamber, which is separated from the float chamber by a partition wall and communicates with the main nozzle of the intake cylinder, in a four-cycle engine carburetor, and a first diaphragm chamber and the float chamber, which are disposed on the partition wall. a communicating shear restrictor; a reverse valve disposed on the partition wall that allows fuel to flow only from the float chamber to the first diaphragm chamber; and a second diaphragm chamber separated from the first diaphragm chamber by a diaphragm. This is achieved by an autostarter mechanism of the carburetor, which is characterized by being provided with an air passageway for introducing positive pressure from the freezer in the crank chamber into the second diaphragm chamber.

The present invention will be described in detail with reference to the embodiments shown in the drawings. 1 is an intake cylinder of the carburetor main body, 2 is a partition wall 3 and a diaphragm 4, and from above, a float chamber 2a, a first diaphragm chamber 2b, The housing is divided into three second diaphragm chambers 2c, and the first diaphragm chamber 2b filled with fuel and the second diaphragm chamber 2C into which positive pressure can be introduced constitute a fuel reservoir. The partition wall 3 is provided with a throttle pipe 5 having a throttle 5a and a check valve 6 that only allows fuel to flow from the float chamber 2a to the first diaphragm chamber 2b. 7 is a main nozzle that penetrates the partition wall 3 from the first diaphragm chamber 2b and opens near the venturi portion of the intake body 1; 8 is a check that extracts only the positive pressure from the second diaphragm chamber 2c and the crank chamber of the engine. This air passage communicates with a freezer (not shown) having a valve mechanism, and introduces only the positive pressure generated in the crank chamber into the second diaphragm chamber 2C to displace the diaphragm 4.

Since the present embodiment is configured as described above, when the engine is started, the period of the pressure pulse in the crank chamber changes greatly due to the low rotation speed when the engine is coiled.
Among them, only the positive pressure via the check valve mechanism is introduced from the freezer into the second diaphragm chamber 2c of the fuel reservoir through the air passage 8, and the diaphragm 4 is displaced upward, causing the pressure to flow into the first diaphragm chamber 2b. The fuel in the throttle tube 5
Since the check valve 6 prevents the air from returning to the float chamber a, the air is supplied into the intake shell 1 through the main nozzle 7. It should be noted that when the diaphragm 4 is not displaced, fuel introduced from the float chamber 2a into the first diaphragm chamber 2b via the throttle pipe 5 and check valve 6 is supplied from the main nozzle 7 as is known. Therefore, when the diaphragm 4 is displaced upward, an increased amount of fuel will be supplied to make it suitable for starting. When the engine completes combustion, the pressure fluctuations in the crank chamber become smaller and the pressure introduced into the second diaphragm chamber 2C through the air passage 8 decreases, so that the diaphragm 4 (as shown in the drawing) The main nozzle 7 returns to the position shown in FIG. When the diaphragm 4 is displaced downward, the fuel pressure in the first diaphragm chamber 2b decreases, but according to the displacement of the diaphragm 4, fuel flows from the float chamber 2a into the first diaphragm chamber 2b via the check valve 6. Since the drop in fuel pressure in the room is suppressed, the normal amount of fuel is supplied from the main nozzle 7 when the introduction of positive pressure from the freezer is finished, and - The fuel ratio is never too lean and is always maintained at an appropriate level. Incidentally, the freezer in the crank chamber is opened to the atmosphere after the engine completes t3.

Furthermore, if a means is provided in the air passage 8 to terminate the introduction of positive pressure from the freezer when the engine temperature reaches a predetermined temperature or higher, air-fuel mixture is not necessary when starting the engine at high temperature. It can prevent over-concentration. like that"
As a means, for example, when a predetermined temperature is exceeded, the inverted bimetal is inverted to block the air passage 8.
(Bimetal Vacuum Switching
A pressure leak valve that prevents pressure from the freezer from acting on the second diaphragm chamber 2C above a certain temperature may be used.

1 As described above, according to the present invention, a first diaphragm chamber is provided which communicates with the float chamber of the carburetor via the throttle and the check valve, and the fuel in the first diaphragm chamber is supplied to the freezer of the engine crank chamber. Since the positive pressure from the engine is applied through the diaphragm and the fuel in the first diaphragm chamber is supplied into the intake cylinder without flowing back into the float chamber, it is possible to reliably increase the amount of fuel supplied at the time of starting. , an autostarter mechanism with a simple structure and low manufacturing cost has been achieved, and furthermore, since the pressure change in the first diaphragm chamber can be suppressed when the introduction of positive pressure from the freezer is stopped, the air-fuel mixture is This has the effect that the air-fuel ratio is always maintained at an appropriate level without becoming temporarily too lean.

[Brief explanation of the drawing]

The accompanying drawing is a schematic sectional view showing an embodiment of an autostarter mechanism for a carburetor according to the present invention. 1... Intake cylinder, 2a... Float chamber, 2b...
...first diaphragm chamber, 2c...second diaphragm chamber, 3...partition wall, 4...diaphragm,
5a... Throttle, 6... Check valve, 7... Main nozzle, 8... Air passage.

Claims (1)

[Claims] In a carburetor for a four-stroke engine, a first diaphragm chamber is separated from a float chamber by a partition and communicates with a main nozzle of an intake cylinder, a throttle communicates the first diaphragm chamber with the float chamber, and the float chamber. a second diaphragm chamber that is separated from the first diaphragm chamber by a diaphragm; An autostarter mechanism for a carburetor, characterized in that an air passage is provided to introduce air into a second diaphragm chamber.