JPH03182684A - Fuel feeding device for engine - Google Patents

Abstract

PURPOSE:To improve stability of the feed of fuel by increasing a spring load of one of the two springs arranged in two negative pressure chambers and pressing the diaphragm of a measuring needle, and rapidly moving the measuring needle from a position during idling to a position during the stop of an engine. CONSTITUTION:A press spring 40 arranged in a first negative pressure chamber 35 for causing operation of a diaphragm 31 in the direction in which the effective area of a nozzle 26 of a measuring needle 27 is decreased and a balance spring 41 equipped in a second negative pressure chamber 39 for causing operation of the diaphragm 31 in the direction in which the effective area of the nozzle 26 is increase are provided. The spring load of the balance spring 41 is increased to a value higher than that of the other. Thus, the diaphragm 31 is moved further toward the negative pressure chamber 35 during the stop of an engine than during idling, the spring loads of the springs 40 and 41 are kept in a balancing position, and the effective area of the main nozzle 26 is increased during the stop of an engine than during idling. This constitution restores lowering of a rotation speed during idle running.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for supplying fuel (gasoline) to a small displacement engine.

[Prior Art] Among the carburetors that are widely used as a means of supplying fuel to relatively small displacement engines that drive small vehicles, industrial machinery, generators, etc., fixed venturi carburetors are used for low-speed fuel and Because the main fuel is supplied through a separate passage, the fuel connection tends to be unstable and the passage configuration is complicated.Variable venturi carburetors have many parts that require extremely high machining precision, such as the venturi piston and its guide. I have a problem. In addition, float-type fuel adjustment means cannot cope with large inclinations, and belly-type ones can cope with various postures, but the fuel control accuracy is poor.

On the other hand, in contrast to the above-mentioned carburetor that sucks fuel into the intake passage using a venturi negative pressure, there is a so-called injection carburetor that was put into practical use during World War II as a countermeasure against freezing in aircraft engine carburetors. This vaporizer is made by Pendix.
The Nberg type carburetor is widely known, and includes a fuel pressure control valve driven by the differential pressure between venturi inlet dynamic pressure and venturi negative pressure, a fuel flow control valve linked to a throttle valve, and a fuel driven by venturi negative pressure. Fuel is injected into the intake passage through an injection valve at positive pressure.

Although such a so-called injection carburetor has the advantage of high fuel control accuracy in various postures, the three valves mentioned above are arranged in series in the fuel passage, and there is also a Japanese Patent Laid-Open No. 1-3203 discloses a fuel supply device having a structure in which only a fuel pressure regulating means is disposed in the fuel passage, which improves the drawback that the fuel system is extremely complicated because the fuel supply means is provided separately.
It is disclosed in Publication No. 1.

The technology disclosed in the above-mentioned publication was provided by the inventor and patent applicant of the present invention, and is a fuel pressure regulator that adjusts fuel to a substantially constant positive pressure and sends it to a main nozzle that opens into an intake passage. and a fuel flow regulator that operates a metering needle that changes the effective area of the main nozzle in response to the differential pressure between the venturi negative pressure and the intake manifold negative pressure to increase or decrease the effective area in accordance with the engine intake air amount.

However, in such a fuel supply system, if the metering needle position when the engine is stopped is set to the same position as when idling, similar to the metering needle position in SU carburetors and Amar carburetors, when the engine rotation speed decreases, the main nozzle becomes effective. Since the metering needle is moved in the direction that minimizes the area, the mixture becomes too lean and the rotational speed cannot be recovered. Starting when cold is difficult. Acceleration response is poor.
This causes the same problem as the above-mentioned type of carburetor, and it is difficult to appropriately set the metering needle position when the engine is stopped so as not to impair engine drivability.

[Problems to be Solved by the Invention] The present invention attempts to solve the above-mentioned problem that it is difficult to appropriately set the position of the metering needle when the engine is stopped, and the engine operability is likely to be impaired. It is an object of the present invention to provide a fuel supply device for an engine that is easy to maintain rotational speed in a rotational range, easy to start when cold, and has excellent acceleration response.

[Means for Solving the Problems] The present invention includes an intake passage having a fixed venturi and a throttle valve, a main nozzle which opens into the intake passage and whose effective area is variable by a metering needle, and which adjusts the pressure of fuel to a substantially constant pressure. and a fuel flow regulator that operates the metering needle to change the effective area of the main nozzle in accordance with the engine intake amount, and the fuel flow regulator is configured to adjust the fuel flow rate. The device includes a diaphragm to which the metering needle is attached, a negative positive chamber formed by sandwiching the diaphragm into which a venturi negative pressure is introduced, and an intake negative pressure on the side of the throttle valve or downstream thereof. In order to solve the above-mentioned problem of an engine fuel supply system having a second negative and positive chamber, the following measures were taken.

That is, a pressure spring that presses the diaphragm and a balance spring were inserted into the first negative pressure chamber and the second negative pressure chamber. This balance spring has a spring load greater than that of the pressure spring, and the metering needle is positioned at a position where the effective area of the main nozzle is larger when the engine is stopped than when it is idling.

It is preferable that the position of the metering needle when the engine is stopped is approximately the same as the position when the engine is running at high speed with no load.

[Function] When the engine is started, the effective area of the main nozzle is larger than when the engine is idling, so even when the engine is cold, sufficient starting fuel is supplied and the engine can be started easily.

Furthermore, when the rotational speed decreases during idle rotation, the intake negative pressure decreases, so the balance spring operates the metering needle toward the engine stop position to increase the fuel flow rate and restore the rotational speed.

Furthermore, even during acceleration, the decrease in intake negative pressure and the spring force of the balance spring work together to quickly move the metering needle from the idle position to the engine stop position, so acceleration fuel is supplied in a responsive manner. It will be done.

[Example] Embodiments of the present invention will be described based on the drawings.

A fixed venturi 3 and a throttle valve 4 are installed in a single intake passage 2 extending in the vertical direction of the main body 1, and a fuel pressure regulator 10 and a fuel flow regulator 30 are installed on opposing outer sides of the main body 1. is provided.

The fuel pressure regulator lO is a regulator body 1 fixed to the body 1.
1, a pressure regulating valve 12, and a pressure regulating chamber 15, and a fuel conduit 9 having a fuel pump 7 that is driven when the engine is operating, and an electromagnetically driven on-off valve 8 that is opened when the engine is operating. Through the fuel introduction passage 1 of the regulator body 11
3 with positive pressure, and the pressure is generally between 0.1 and 0.
．． The regulator body 11 is fixed to the main body 1 with a diaphragm 14 in between, and the regulator body 11 side of the diaphragm 14 forms a pressure regulating chamber 15, and the main body I side forms an atmospheric chamber 16. A pressure regulating spring 17 inserted between the main body 1 and the diaphragm 14 is built into the atmospheric chamber 16.

The pressure regulating valve 12 has a valve chamber 18 to which the fuel introduction passage 13 is connected.
The valve has a valve body 19 inserted into a valve chamber 18, a valve spring 20, and a valve seat 21, and a valve rod 23 protruding from the valve body 19 communicates the valve chamber 18 and the pressure regulating chamber 15. It loosely passes through the seat opening 22 and contacts the center of the diaphragm 14. Therefore,
The valve body 19 opens and closes the valve seat port 22 according to the position of the diaphragm I4, which is determined by the fuel pressure in the pressure regulation chamber 15 and the loads of the valve spring 20 and the pressure regulation spring 17. When the pressure increases, the valve closes, and when the pressure decreases, the valve opens, and the fuel in the pressure regulating chamber 15 is generally 0.05 to 0.2 kg/c.
Adjust to a positive pressure of about 200 m.

The fuel in the pressure regulating chamber 15 passes through the fuel passage 25 of the regulator body 11 and main body 1, and is injected with positive pressure from the tip of the main nozzle (or needle jet) 26 that protrudes toward the narrowest part of the fixed venturi 3. It is mixed with intake air and supplied to the engine.

Next, the fuel flow regulator 30 has a diaphragm 31 attached to the main body 1.
The diaphragm 31 has a cover unit 32 fixedly sandwiched therebetween, and the cover unit 32 side of the diaphragm 31 has a first negative pressure chamber 35 that communicates with the narrowest part of the fixed venturi 3 through a first negative pressure path 34 having a throttle 33. form.

The main body 1 side forms a second negative pressure chamber 39 that communicates with the side of the throttle valve 4 in the idle position by a second negative pressure path 37 having a throttle 36, and the first negative pressure chamber 35 and the second negative pressure Room 3
A pressure spring 40 for pushing the diaphragm 31 and a balance spring 41 are inserted into the spring 9, respectively. Second negative pressure path 3
7 opens into the intake passage 2 with a plurality of boats 38 to alleviate sudden changes in negative pressure caused by sudden opening and closing of the throttle valve 4, but as disclosed in JP-A-1-32031, There is no problem even if the throttle valve 4 is opened downstream of the throttle valve 4.

A metering needle 27 is fixed in the center of the diaphragm 31, which crosses the second negative pressure chamber 39 and passes through the guide 28 of the main body l in a gas-tight manner to the main body located on the opposite side of the fixed venturi 3. It is inserted into the nozzle 26. This metering needle 27 is connected to the venturi negative pressure, the intake negative pressure on the side of the throttle valve 4, the pressure spring 40, and the balance spring 41.
The main nozzle 26 reciprocates linearly according to the position of the diaphragm 31, which is determined by the load, and changes the effective area of the main nozzle 26 to adjust the flow rate of fuel supplied to the engine.

That is, when the throttle valve 4 is in the idle position or at a small opening, the venturi negative pressure is low and the intake negative pressure generated in the port 38 is high, so the diaphragm 31 moves largely toward the second negative pressure chamber 39 and the main nozzle 26 is closed. Reduce effective area. Furthermore, as the opening degree of the throttle valve 4 increases, the difference between the venturi negative pressure and the intake negative pressure becomes smaller, and above the opening degree, the venturi negative pressure becomes higher.
5 to increase the effective area of the main nozzle 26. By such movement of the diaphragm 31, the amount of intake air and the flow rate of fuel can be made basically proportional, and the air-fuel ratio can be kept constant.

In the present invention, the main nozzle 26 is charged into the first negative pressure chamber 35.
a pressure spring 40 that acts on the diaphragm 31 in a direction that reduces the effective area of the main nozzle 26; and a balance spring 41 that is inserted into the second negative pressure chamber 39 and acts on the diaphragm 31 in a direction that increases the effective area of the main nozzle 26. The spring load of the balance spring 41 is increased. Therefore, when the engine is stopped, the diaphragm 31 is more open to the first negative pressure chamber 3 than when the engine is idling.
5 so that the spring loads of the two springs 40, 41 are balanced, and the effective area of the main nozzle 26 is larger when the engine is stopped than when the engine is idle.

FIG. 2 is a diagram showing the positional relationship between the main nozzle 26 and the metering needle 27 when the engine is stopped and when the engine is idling. When the engine is stopped, part A of the metering needle 27 defines the effective area of the main nozzle 26 by the spring force of the balance spring 41, but when the engine is idling, the high intake negative pressure introduced into the second negative pressure chamber 39 measures the area. Part B of the needle 27 is the main nozzle 2
Define the effective area of 6.

If the position of the metering needle 27 when the engine is stopped is set to be almost the same as the position when the engine is running at high speed with no load, the metering needle will always be metered in a direction that increases the effective area of the main nozzle 26 when the intake negative pressure decreases between AB. The needle 27 will be moved.

Next, the state when the engine is started will be explained.

Relatively small displacement engines that drive small vehicles, industrial machinery, generators, etc. have governors, and the throttle valves are half open or fully open when the engine is stopped. Then, the engine starts with the throttle valve open and rapidly rotates at high speed, but when the set rotation speed is reached, the governor operates and closes the throttle valve to the idle position. is the required opening degree.

Therefore, when the engine starts, there is almost no difference between the venturi negative pressure and the intake negative pressure, so the metering needle 27 is placed at the same position as when the engine is stopped, as shown in FIG. 2(A).
To ensure reliable starting by supplying sufficient starting fuel even in a cold state. When the amount of intake air increases due to an increase in engine speed after startup, the negative pressure acting on the main nozzle 26 becomes higher, which increases the fuel flow rate, so the air-fuel ratio remains almost constant even if the metering needle 27 does not move. When the throttle valve 4 closes to the idle position, the intake negative pressure introduced into the second negative pressure chamber 39 increases and the venturi negative pressure introduced into the first negative pressure chamber 35 decreases, so that the spring load of the balance spring 41 is reduced. Regardless of the size, the metering needle 27 is
Move to the position shown in B) to reduce the fuel flow rate.

When the engine speed decreases below the idle speed for some reason, the intake negative pressure introduced into the second negative pressure chamber 39 decreases, so the balance spring 41 moves the metering needle 27 toward the position when the engine is stopped. The fuel flow rate is increased to prevent the engine from stopping due to an overly lean mixture, and the rotational speed is restored to enable stable idling.

When the throttle valve 4 opens from the idle position and the engine accelerates, the intake negative pressure introduced into the second negative pressure chamber 39 decreases rapidly, and in cooperation with the spring force of the balance spring 41, the metering needle 27 The main nozzle 26 is quickly moved from the idle position to the engine stop position, and the effective area of the main nozzle 26 is rapidly increased to supply accelerating fuel in a responsive manner.

In this case, since the engine stop position of the metering needle 27 is approximately the same as the position at which the required fuel flow rate at high speed with no load is obtained, the fuel necessary for normal acceleration operation can be supplied without shortage.

In this embodiment, the first correction passage 44 opens into the intake passage 2 with the boat 45 on the opposite side of the boat 38 across the throttle valve 4 in the idle position, and the first correction passage 44 opens into the intake passage 2 on the upstream side of the fixed venturi 3. A second correction passage 46 is connected to the first negative pressure chamber 35. Further, a correction passage 47 that opens into the inside of an air cleaner (not shown) and introduces the atmosphere is connected to the second negative pressure chamber 39. These prevent the diaphragm 31 from being moved impulsively and causing the metering needle 27 to overstroke due to sudden changes in the venturi negative pressure or intake negative pressure.

[Effects of the Invention] According to the present invention, metering at idle and when the engine is stopped is achieved by simply setting the spring load relationship between two springs that are inserted into two negative pressure chambers and push the diaphragm of the metering needle. By setting the needle position to each appropriate position, stability in the 5 idle rotation range, startability when cold,
Fuel can be supplied with excellent acceleration response.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view showing an embodiment of the present invention, Fig. 2 (A)
, (B) is a diagram showing the positional relationship between the main nozzle and the metering needle.

Claims (1)

[Scope of Claims] 1. An intake passage having a fixed venturi and a throttle valve, a main nozzle that opens into the intake passage and whose effective area is variable with a metering needle, and a main nozzle that adjusts fuel to a substantially constant positive pressure. a fuel pressure regulator for feeding the fuel to the nozzle; and a fuel flow regulator for operating the metering needle to vary the effective area of the main nozzle substantially in response to engine intake air flow. A diaphragm to which the metering needle is attached, a first negative pressure chamber formed across the diaphragm into which the venturi negative pressure is introduced, and a second negative pressure chamber on the side of the throttle valve or downstream thereof into which the intake negative pressure is introduced. In an engine fuel supply system having a pressure chamber;
A pressure spring and a balance spring that push the diaphragm are inserted into the first negative pressure chamber and the second negative pressure chamber, and the balance spring has a spring load larger than that of the pressure spring, and when the engine is stopped, the main nozzle A fuel supply device characterized in that the metering needle is located at a position where the effective area of the metering needle is larger than when the metering needle is idle. 2. The fuel supply system for an engine according to claim 1, wherein the position of the metering needle when the engine is stopped is set to be substantially the same as the position when the metering needle is at high speed with no load.