JPS6143260A - Variable venturi type carburetor - Google Patents

Abstract

PURPOSE:To supply the mixed gas having the optimum air fuel ratio by forming a plurality of throttles in parallel into an air bleed passage for controlling the flow rate according to the temperature of a variable venturi carburetor and selecting the throttle according to the engine operation state. CONSTITUTION:A needle valve 4 is fixed at the edge surface of a slidable piston 3 installed onto the upstream side of a throttle valve 6. The amount of fuel supply is controlled by controlling the opening area of a jet 21. The bleed air is supplied into the jet part 21 from a hole 24. Said bleed air is supplied from a passage 32 having a throttle 42 installed in parallel to a passage 31 having a throttle 44, through a valve 30 whose opening area is varied by a wax 33 which expands and contracts according to the cooling-water temperature. A negative- pressure reacting valve 41 is installed into the passage 32, and since the intake negative-pressure reduces during acceleration, the valve 41 is closed to reduce the amount of bleed air, and dense mixed gas is supplied, while during deceleration, the valve 41 is opened by a high negative pressure, and the mixed gas is made thin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable venturi carburetor for an internal combustion engine, and more particularly to a variable venturi carburetor that controls the air-fuel ratio by air bleed.

In the conventional technology variable venturi type carburetor, the amount of fuel according to the engine load is measured by the cooperation of the needle attached to the shoulder piston and the meter i-jet installed in the fuel passage into which the needle enters. It has become. In internal combustion engines, it is common practice to increase the amount of fuel to enrich the air-fuel ratio when starting, at low temperatures, or at high output, but this is controlled by a variable venturi carburetor using air bleed. is described, for example, in JP-A-58-106158. Furthermore, when driving in urban areas, the air bleed amount can be increased to reduce the air-fuel ratio.

Problems to be Solved by the Invention In internal combustion engines, it is important to change the air-fuel ratio according to the temperature, and for this purpose, a flow control valve using wax is used. It is designed to change the amount of air bleed (in an analog way). Other air bleed mechanisms, such as the output increase control valve 101 shown in Figure M4, do not use such a flow rate control valve. Even if a temperature-sensitive valve is used, it is an on-off valve that turns on and off at a constant temperature. In reality, there is a demand for the use of flow control valves that continuously change the flow rate in response to temperature in other air bleed mechanisms, but such flow control valves are expensive, so it is necessary to use multiple flow control valves. It doesn't make any sense. An object of the present invention is to enable a single flow control valve to control a plurality of air bleed mechanisms.

Means for Solving the Problems In order to achieve the above object, in the present invention, a flow rate control valve that can continuously control the flow rate according to the temperature is disposed in the air bleed passage, and the flow rate control valve is disposed in the air bleed passage. A #1 characteristic is that a plurality of air bleed control passages are connected in parallel upstream or downstream of the valve.

Embodiment Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically downward V, 3 is a suction piston that moves back and forth in the horizontal direction within the intake passage 2, and 4 is a tip end surface of the suction piston 3. 5 is the inner wall surface of the intake passage 2 formed opposite to the tip surface of the piston 3, 6 is a throttle valve provided in the intake passage 2 downstream of the piston 3, and 7 is a needle attached to the piston 3. The carburetor flow 1 is shown, and a bench portion (FIG. 4) is formed between the tip end surface of the succinic piston 3 and the inner wall surface 5.

A hollow cylindrical casing 10 that encloses the rear end side of the succinic piston 3 is fixed to the carburetor main body 1, and a guide sleeve 11 that extends in the axial direction of the casing IO inside the casing 10 is attached. A bearing 12 is inserted into the guide sleeve 10, and the outer end of the guide sleeve 10 is closed by a blind cover 13. On the other hand, a guide port 14 is fixed to the succinct piston 3, and the guide rod 14 is inserted into the bearing 12 so as to be movable in the axial direction of the guide rod 14. Since the suction piston 3 is thus supported by the casing 9 via the bearing 12, the suction piston 3 can move smoothly in its axial direction. The interior of the casing 9 is divided into a negative pressure chamber 15 and an atmospheric pressure chamber 16 by the Saxicon piston 3.
The negative pressure chamber 15 includes a suction piston 3.
A compression spring 17 that constantly presses toward the venturi portion 8
is inserted. Negative pressure chamber 15d Sakushi! The atmospheric pressure chamber 16 is connected to the venturi section 8 through the suction hole 18 formed in the carburetor body 1, and the atmospheric pressure chamber 16 is connected to the intake passage upstream of the suction piston 3 through the air hole 19t formed in the carburetor body 1. 2.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided within this fuel passage 20. The fuel passage 20 upstream of the metering jet 21 is connected to the float chamber 7 via a fuel nozzle 22 extending downward, and the fuel in the float chamber 7 is pumped into the fuel passage 20 via this fuel pipe 22. . Furthermore, a hollow cylindrical nozzle 2 is disposed coaxially with the fuel passage 20 on the inner wall surface 5.
3 is fixed. This nozzle 23 protrudes from the inner wall surface 5 into the venturi portion 8, and further protrudes from the upper half of the tip of the nozzle 23 toward the piston 3. The needle 4 extends through the nozzle 23 as well as the metering jet 21, and the fuel is metered by the annular gap formed between the needle 4 and the metering jet 21 before being transferred to the nozzle 23.
The air is supplied into the intake passage 2 from the air. The needle 4 is provided with a notch for starting and increasing the amount, and when the venturi is fully closed as shown in FIG. 1, the notch and the metering jet 21 come to corresponding positions and the annular area between them increases. The metering jet 21 is provided with a plurality of through holes, and air is bleed from the annular passage around the outer periphery of the metering jet 21 and the air bleed passage 24 to the fuel passage 20 of the metering jet 21. In this air bleed passage 24, Air supplied via the low temperature fuel increase mechanism and the output increase mechanism are combined and introduced. In the conventional volume increasing mechanism, each mechanism is formed independently from each other, as shown in FIG. 4, and only controlled air is combined and introduced. In the present invention, as shown in FIG.
2 are connected in parallel, and then the air bleed passage 24
will be rejoined and connected. Therefore, one air bleed passage is formed from the air intake, including the passages 31 and 32 and the air bleed passage 24t formed in the carburetor body 1. In the embodiment shown in FIG. 1, the flow control valve 30 is located upstream, and the passages 31, 32 are connected in parallel downstream thereof.

However, according to the invention, the passages 31, 32 are placed upstream and the flow control valve 30 is placed downstream of them.
It is also possible to connect so that 1.32 are connected in parallel.

The flow control valve 30 is a valve driven by wax 33;
It has a sherrod 34, and a conical valve body 35 is integrally formed on the sherrod 34. A port 36 is formed in connection with the conical surface of the valve body 35, and the air intake de-)
37 is always open regardless of the position of the valve body 35. Port for passing engine cooling water near wax 33) 38
．． There are 39. The wax 33 contracts when the temperature is low and the valve body 3
5, the opening area of the port 36 is narrowed, and as the temperature rises, it expands and pushes the valve body 35 to the right, gradually opening the opening area of the port 36. This is well known, and the flow rate control valve 30 continuously controls the flow rate depending on the temperature. The air whose flow rate is controlled in this manner flows into parallel passages 31 and 32. One aisle 31
A restrictor 40 is disposed at , and the flow rate of air passing therethrough is made smaller than the maximum flow rate of the flow rate control valve 30 . A negative pressure control valve 41 is disposed in the other passage 32, and a restrictor 42 is provided at its outlet.The negative pressure control valve 41 has ports 43 and 44 forming part of the passage 32, A shaped valve body 45 is capable of closing the port 44. The valve body 45 is biased by a compression spring 46 from behind, and negative intake pressure is applied from a port 47 . The intake negative pressure becomes extremely small when the throttle valve 6 is under high load and close to fully open. Therefore, when the load is low, the valve body 41 opens the port 44 and allows the passage 32 to pass through.
When the load is high, the port 44 is closed to block the passage 32.

When the passage 32 is shut off, the amount of air to be aerosoled is controlled by either the restrictor 40 or the flow rate control valve 30. Therefore, when the temperature is relatively low, the amount of air bleed at the time of output is also controlled by the flow rate control valve 30.

This is the negative pressure control valve 1 for output control as shown in Fig. 4.
This was not the case in the conventional case where the valve 01 was configured independently from the flow control valve 100.

FIG. 2 shows a generalized version of the air bleed control mechanism shown in FIG. do not have. Also, the air bleed control line TNraX is connected in parallel.

32 are each provided with some kind of flow control means, and in the embodiment, one passage 31 is provided with a restrictor 40, and the other passage 32 is provided with a negative pressure control valve 41 for increasing output and a restrictor 42. . The flow rate when the flow control valve 30 is fully open is greater than the flow rate given by the sum of the restrictors 40 and 42.

Referring to FIG. 3, the broken line X indicates the flow rate control valve 10 in FIG.
0 and the control valve 101 are both open, and the broken line Y shows the characteristic when the control valve 101 is closed and the amount of fuel is increased during high load. These characteristics are always in a parallel relationship regardless of temperature, and the air-fuel ratio changes between these two characteristics as the control valve ioi opens and closes. Since it is undesirable to switch suddenly from rich to lean at low temperatures, the control valve 101 can be locked until a certain temperature, in which case the normal air-fuel ratio changes from the low temperature side to y, z, x. It will change like this.

On the other hand, the characteristics shown by the solid line are examples of the characteristics according to the present invention. As shown by the solid line A, when the temperature is relatively low, the flow rate control valve 30 shares! The lead amount, that is, the air-fuel ratio is regulated, and it does not affect the opening and closing of the control valve 41 (because the throttle valve 40 has a larger diameter than the flow control valve 30).As the temperature rises, the flow control valve 300 diameter and If the aperture of the diaphragm 40 is equal, the characteristics are divided into characteristic B and characteristic C thereafter.

Characteristic B is when the control valve 41 is open.
Characteristic C is when the control valve 41 is closed. As is clear from FIG. 3, the widths of characteristics B and C can be made smaller at high temperatures.

If the width of the conventional characteristics X and Y is made smaller, the output increase at low temperatures will be insufficient.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention allows a single flow control valve to control the characteristics of multiple air bleed passages.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a variable pressure/chillifier vaporizer according to the present invention, FIG. 2 is a generalized view of the air bleed mechanism shown in FIG. 1,
FIG. 3 is a diagram illustrating flow characteristics, and FIG. 4 is a diagram illustrating a conventional air bleed mechanism. l...Carburetor body, 3...Sakushi W piston, 4
...Needle, 20...Fuel passage, 21...Measuring die? ), 24... Air bleed passage, 30... Flow rate control valve, 31.32... Passage, 40.42... Throttle, 41... Negative pressure control valve.

Claims (1)

[Claims] A suction piston that changes the venturi area in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter, and a fuel passage inside the fuel passage. a variable venturi type carburetor comprising a metering jet provided and cooperating with the needle, and further comprising an air bleed passage for supplying air into the fuel passage, the air bleed passage having a continuous, temperature-dependent metering jet; A variable venturi type carburetor, characterized in that a flow control valve capable of controlling the flow rate is disposed at the flow rate control valve, and a plurality of air bleed control passages are connected in parallel upstream or downstream of the flow control valve. .