JPH11280584A - Fuel supplying device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregular rotation of an engine on an operation by providing two fuel tanks connected in series, and a reflux passage for gaseous component in a fuel passage formed between a fuel pump and a fuel tank, and exhibiting strong suction force by a fuel pump of two steps. SOLUTION: In a fuel passage of a marine engine, fuel pumps 1, 2 are connected to an engine main body in series, an intake port 3 of the fuel pump 1 is connected to a fuel tank by a fuel pipe, and a delivery port 4 of the fuel pump 2 is connected to a fuel injection valve through a pressure regulator and the like. Namely, a hollow separator 6 is screwed around a delivery port 5 of the fuel pump 1, and a right end opening of the separator 6 is closed by a cover having a short pipe shaped nipple. One end of a connecting pipe 15 is connected to the nipple of the separator 6 through a rubber pipe 16 and the like, and the other end of the connecting pipe 15 is connected to the intake port 18 of the fuel pump 2 through a rubber pipe 17 and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine (engine), and more particularly to a so-called marine engine used as an outboard motor for a small boat, which is an improved system for supplying fuel from a fuel tank to the engine. About.

[0002]

2. Description of the Related Art In recent years, marine engines have been subject to emission control as well as automobile engines. The use of EFI (Electronically Controlled Fuel Injection Device) in engines has been increasing. Since the fuel pump installed in the carburetor does not need to compress the fuel, even if the fuel passage from the fuel tank to the carburetor is long, the volume transfer by the fuel pump is easy,
Normally, fuel can be sucked up and supplied to the engine without problems, so in the past it was not much of a problem,
In the case of EFI in a car engine, fuel at atmospheric pressure in a fuel tank is sucked and pressurized to a predetermined pressure,
Since the fuel pump provided for feeding the fuel to the fuel injection valve (injector) is usually provided on the fuel tank side instead of the engine side, no problem occurs. However, when the EFI is used for the marine engine, the fuel passage is long. If a volatile fuel such as gasoline in the fuel passage is heated and a vapor lock occurs due to air bubbles at the time of dead soak (engine stop immediately after high-load operation), the fuel pump draws fuel from the tank. And the engine cannot be started (or restarted), or the engine may temporarily stop during operation to cause a so-called "breath".

In the United States Coast Guard regulations, a fuel pump that draws fuel, such as gasoline, from a tank and supplies it to the engine is 12 inches (3 inches) from the engine.
It is stipulated that the fuel pump must be installed within 0.5 cm), and it is required that the fuel pump be installed as close to the engine as possible. Also, in the case of marine engines, the engine is usually handled as a single product, so the fuel pump is attached to the engine body instead of the fuel tank as a part attached to the engine, so the fuel tank and the fuel pump In many cases, the fuel passage between them becomes longer. Further, the fuel passage is provided with a low-pressure filter for removing dust and moisture contained in the fuel, and the low-pressure filter increases the flow resistance in the fuel passage. Therefore, any of these may hinder fuel pumping of the fuel pump in the marine engine and cause irregular rotation problems such as inability to start the engine and breathing during operation.

As one of the prior arts for solving this problem, a water-cooled engine disclosed in Japanese Patent Application Laid-Open No. Hei 6-280709 discloses a method of diverting a part of engine cooling water to supply it around a fuel pump. By forcibly cooling the fuel pump, it is intended to prevent vapor lock caused by fuel bubbles generated inside the fuel pump. However, even if such measures prevent the heating of the fuel in the fuel pump, if the fuel passage from the fuel tank to the fuel pump is long, it is not possible to prevent the vapor lock in the fuel passage except for the fuel pump itself. Since it is impossible, the above-mentioned problem cannot be completely solved.

[0005]

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned problems in the prior art and solves the above problem even when the fuel passage from the fuel tank to the fuel pump is long, such as in a marine engine. An improved internal combustion engine fuel supply that reliably prevents fuel vapor lock, improves engine startability, and eliminates irregular running of the engine during operation. It is intended to provide a device.

[0006]

According to the present invention, there is provided a fuel supply device for an internal combustion engine as described in the claims as means for solving the above-mentioned problems.

The fuel supply device according to the first aspect includes two fuel pumps connected in series, and a recirculation passage for a gas component in a fuel passage between the fuel pump and the fuel tank. Therefore, a strong suction force is exerted by the two-stage fuel pump, and even if there are many bubbles in the fuel passage, the fuel can be sucked and pressurized.
In addition, since gas components such as bubbles discharged from the first fuel pump are recirculated to the fuel tank, the fuel supplied to the internal combustion engine contains no gas components. Therefore, there is no possibility that the engine will have problems such as inability to start or irregular rotation.

Further, in the fuel supply device according to the second aspect of the present invention, since the throttle portion is provided in the return passage, the gas component can easily pass through the throttle portion and return to the fuel tank. Since the fuel is unlikely to pass through the throttle, it flows exclusively toward the second fuel pump, thereby further reducing the possibility of supplying a gaseous component to the internal combustion engine.

In the fuel supply device according to the third aspect, the portion composed of the first fuel pump, the second fuel pump, and the gas-liquid separation means is located closer to the internal combustion engine body than the fuel tank side. Since it is located near, the fuel pump etc. can be configured as a part of the engine body, resulting in safety suitable for configuring the engine as a marine engine like an outboard motor for small boats Will be high. In this case, the fuel passage from the fuel tank to the first fuel pump becomes long, and vapor lock occurs due to the generation of air bubbles in the fuel passage. However, the present invention prevents such a problem.

[0010] In the fuel supply device according to the fourth aspect, two fuel pumps having substantially the same performance in discharge capacity and the like are used. Using two identical fuel pumps is also advantageous in terms of cost,
Since the total suction force is increased by connecting them in series, it is possible to reduce the size of each fuel pump.

[0011]

FIG. 1 illustrates the configuration of an engine fuel supply device according to an embodiment of the present invention. In accordance with the features of the present invention, a fuel passage (not shown) of a marine engine includes: The two fuel pumps 1 and 2, that is, a first fuel pump 1 and a second fuel pump 2, are basically provided in series on the engine main body side, not on the fuel tank side. The fuel pumps 1 and 2 have approximately the same performance in terms of discharge capacity and the like, and the pump type may be any type as long as it is a positive displacement type. And a vane type pump integrated with the pump. The suction port 3 of the first fuel pump 1 is connected to the fuel tank by a long fuel pipe. A low-pressure filter may be provided on the way. The discharge port 4 of the second fuel pump 2 is connected to a fuel injection valve of a marine engine (not shown) via a pressure regulator and the like.

Discharge port 5 of first fuel pump 1
Is screwed with a hollow separator 6 having a structure as shown in an enlarged manner in FIG. The right end opening of the separator 6 is closed by an annular lid 8 having a short tubular nipple 7, and a gap 11 is formed between the right end surface of the inner wall 10 having the female screw hole 9 and the left end of the nipple 7. Is formed,
An annular space 12 communicating with the female screw hole 9 through the gap 11 is formed inside the separator 6 so as to surround the outer periphery thereof. The annular space 12 communicates with a reflux port 14 shown in FIG. 1 through a small-diameter throttle hole 13 drilled in a part of the separator 6, and the reflux port 14 is connected to a fuel tank via a reflux pipe (not shown). Is connected to the upper gas phase.

The nipple 7 of the separator 6 is connected to one end of a connection pipe 15 bent in a U-shape by a flexible rubber pipe 16.
The other end of the U-shaped connection pipe 15 is connected to the suction port 18 of the second fuel pump 2 via another rubber pipe 17 or the like.

In FIG. 1, reference numeral 19 denotes a bracket having a band-shaped portion for mounting the fuel pumps 1 and 2 to a substrate which is a part of an engine body (not shown), 20 denotes a bolt mounting hole for fixing the same, Reference numeral 21 denotes a metal band for fixing the rubber pipes 16 and 18 to the connection pipe 15 or the like in a mounted state, 22 denotes a bolt for connecting both ends of the metal band, and 23 and 24 denote driving power to the fuel pumps 1 and 2. Shows the wires to supply.

Since the embodiment of the present invention is configured as described above, when the two fuel pumps 1 and 2 are supplied with electric power and driven at the same time, the two fuel pumps 1 and 2 are driven.
Are connected in series, and the first fuel pump 1 is connected to the fuel tank via the parts 6 and 14, so that the volume easily moves from the upstream side to the downstream side of the fuel pump 1 and the fuel Aspirate. If there is only one fuel pump, the fuel in the fuel passage to the fuel tank on the upstream side of the fuel pump must compress the vaporized gas or air and send the fuel to the fuel tank unless it is sent downstream. If the volume of vaporized gas or air exceeds the air compression capacity of the fuel pump because the fuel passage on the suction side is long and a low-pressure filter is installed, the vaporized gas on the upstream side Because the fuel pump cannot send fuel to the engine because the air cannot be compressed and sent to the downstream side, the engine does not operate normally.

When the vaporized gas or air discharged from the first fuel pump 1 passes through the parts 6 and 15 and is sucked into the second fuel pump 2, it exceeds the air compression capacity of the pump 2. Thus, the pump 2 does not cause a volume shift to the downstream side, and cannot inhale the vaporized gas or air on the upstream side. However, in the embodiment of the present invention, the vaporized gas discharged from the first fuel pump 1 The air passes through the throttle hole 13 of the component 6 and returns to the upper space of the fuel tank through the return port 14 and the return pipe (not shown) connected thereto.

On the other hand, since the inertia force of the flow acting on the liquid fuel is larger than that of the vaporized fuel gas or air bubbles, the liquid fuel suddenly changes its flow direction inside the separator 6. On the other hand, it is difficult to flow into the annular space 12 and a large viscous resistance acts when the liquid fuel passes through the throttle hole 13. To the nipple 7 as shown by the arrow F, and the connecting pipe 1
5 and is sucked into the second fuel pump 2. Therefore, since the fuel pumped by the second fuel pump 2 contains substantially no air bubbles, the engine supplied with the air-free fuel does not cause troubles such as inability to start or irregular rotation. .

The separator 6 downstream of the first fuel pump 1 is not limited to the type shown in the illustrated embodiment, but may be another type such as a cyclone type. It is possible.

FIG. 3 is a diagram showing the effect of the present invention.
FIG. 3A shows the time of the discharge pressure of the second fuel pump 2 when the fuel supply device for an engine of the present invention is used under the condition that the fuel passage to the fuel tank is at a high temperature due to dead soak. It shows the result of measurement of a typical change. Since the two fuel pumps 1 and 2 are provided in series, the rise of the discharge pressure is slightly delayed, and the fuel initially sucked into the first fuel pump 1 contains many bubbles. Therefore, the flow of the liquid fuel reaching the suction port 18 of the second fuel pump 2 is changed by the air bubbles being returned to the fuel tank in the separator 6. Although the fluctuation is observed, the discharge pressure of the second fuel pump 2 is stabilized in a high state when all the fuel including the bubbles in the fuel passage has passed. The change in the discharge pressure that is slightly observed after the steady state is caused by the action of adjusting the fuel pressure to the set pressure in the pressure regulator provided on the downstream side of the second fuel pump 2.

On the other hand, FIG. 3 (b) shows a case where a conventional single-stage fuel pump is used under the condition that the temperature of the fuel passage to the fuel tank is high as in the case described above. FIG. 4 is a diagram showing a result of measuring a temporal change of a discharge pressure of a fuel pump. Even when the engine is stopped, it is normal that a small amount of fuel remains in the fuel pump, and the remaining fuel is discharged simultaneously with the start of the fuel pump. Therefore, in the case of FIG. Although the discharge pressure rises temporarily at the same time as the start-up, if there are many bubbles in the fuel passage upstream of the fuel pump, when the fuel remaining in the fuel pump is discharged, the remaining The liquid fuel is only sucked, and the liquid fuel cannot be sucked only by the weak suction force of the one-stage fuel pump. As a result, the discharge pressure is substantially constant at a relatively low value due to compression of a gas such as air bubbles, and substantially no liquid fuel can be discharged. Therefore, the engine cannot be started under such conditions.

[Brief description of the drawings]

FIG. 1 is a front view showing a fuel supply device for an internal combustion engine according to the present invention.

FIG. 2 is a longitudinal sectional front view showing a main part in FIG. 1 in an enlarged manner.

FIGS. 3A and 3B are diagrams showing the effect of the present invention, wherein FIG. 3A is based on the apparatus of the present invention, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st fuel pump 2 ... 2nd fuel pump 3 ... suction port 4 ... discharge port 5 ... discharge port of 1st fuel pump 6 ... separator 11 ... gap 12 ... annular space 13 ... throttle hole 14 ... reflux Port 18: suction port of the second fuel pump

Claims (4)

[Claims] 1. A fuel tank containing a volatile fuel, a first fuel pump for guiding the fuel from the fuel tank by a fuel passage and pressurizing the fuel tank, and a fuel tank downstream of the first fuel pump in series. A second fuel pump that is connected to pressurize the fuel discharged by the first fuel pump and supplies the fuel to the internal combustion engine main body; and a connection portion between the first fuel pump and the second fuel pump. A recirculation passage for recirculating a gas component to the fuel tank. 2. The fuel supply device according to claim 1, wherein a throttle portion is provided in the return passage. 3. A part comprising the first fuel pump, the second fuel pump, and the gas-liquid separation means is provided at a position closer to the internal combustion engine body side than the fuel tank side. And the internal combustion engine is
3. A marine engine.
A fuel supply device described in the above. 4. The fuel supply device according to claim 1, wherein the first fuel pump and the second fuel pump have substantially the same performance.