JPS62223455A - Fuel supply device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to maintain a high pressure over a wide load range, by connecting a closed container disposed therein a relief valve which opens a fuel pressure exceeding a predetermined value, to a fuel supply pipe through a branch pipe. CONSTITUTION:A fuel from a fuel tank 8 is pressurized by a fuel pump 2, and is then fed into a fuel injection valve 9 through a fuel supply pipe 3 with a given timing before the fuel is injected into a combustion chamber 1. At this time a part of the fuel in the fuel supply pipe is fed into a relief valve 6 disposed in a closed container 5 through a branch pipe 4. Fuel discharged from the relief valve 6 is all trapped in the closed chamber 5 and is then returned into a fuel supply tank 8 through a return pipe 7. Therefore, during normal load operation which is used for the most occasions, the pressure of fuel injection may be made to approach an allowable highest pressure as possible as it can, and therefore, it is possible to obtain a satisfactory cycle efficiency and combustion efficiency.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel supply device for an internal combustion engine.

[Conventional technology]

In an internal combustion engine having a fuel pump, it is necessary to supply fuel oil in an amount corresponding to the load of one engine to the combustion chamber via a fuel supply pipe.

Generally, the fuel injection valve installed in the cylinder cover is used with the surface of the injection hole constant, so when the fuel pump pumps the increased amount of fuel as the load increases, the fuel injection valve The pressure of fuel oil in the area shows a tendency to increase as the load increases.

An internal combustion engine with such a fuel supply system is usually used at a predetermined normal load for most of the period, but in emergencies, it is used at a higher load, for example at the maximum allowable load. There are things that I do.

FIG. 4 shows an example of a conventional fuel supply system for a diesel engine. In the figure, 1 is a combustion chamber, 2 is a fuel pump, 3 is a fuel supply pipe, and 8 is a fuel tank.

9 is a fuel injection valve, 10 is a cylinder cover, and 11 is a piston.

[Problems to be solved by the invention]

However, as mentioned above, when the engine is used at a load higher than the normal load, the following problems occur.

That is, in Fig. 5, which shows the relationship between engine load and fuel pressure in a conventional fuel supply system as shown in factor 4, if the usage point of the regular load is indicated by A, then the Fuel pressure is designated PA. Also, if the usage point of the highest allowable load, which is used less frequently, is indicated by "tB", the fuel pressure at this point will increase.

Therefore, in an engine that may be used at point B even if only with limited frequency, the fuel pressure pBi.

Fuel pump 2. Fuel supply pipe 3. It is necessary to keep the pressure within the maximum allowable pressure in the design of the fuel supply device including the fuel injection valve 9 and the like. Therefore, A at regular load
At this point, it is necessary to use the fuel pressure PA which is lower than the above-mentioned PB by ΔP.

Generally, in a fuel supply system for an internal combustion engine, the higher the pressure at the time of fuel injection, the faster the fuel can be injected into the required sound cylinder, and the particles of the injected fuel can also be made smaller. There is a tendency for the cycle efficiency and combustion efficiency of one engine to be good, contributing to a reduction in fuel consumption rate.

Therefore, in an engine that is used as described above, even if it is used at point A, which is a regular load that is used most of the time, it is necessary to set point A in preparation for use at point B, which is a high load that is infrequently used. In this case, a problem arises in that the fuel injection pressure is one level lower than the level allowed in the design, and the fuel supply system has to be used at a non-optimal injection pressure.

The present invention solves the above-mentioned problems, brings the fuel injection pressure as close as possible to the highest pressure allowed by the fuel supply system even under normal load, which is used for the longest period of time, and achieves good cycle efficiency and combustion efficiency. An object of the present invention is to provide an internal combustion engine in which the fuel consumption rate is completely reduced by obtaining a fuel pump. A branch pipe is installed in the middle of the fuel pipe that supplies all of the fuel oil into the cylinder, leading the fuel into a sealed container, and a relief valve that opens when the fuel oil pressure exceeds the required set pressure is installed inside this container. It is characterized by what it did. In such a fuel supply system, by setting the opening pressure of the relief valve to the highest pressure allowed by the entire system or a pressure slightly lower than this, high fuel injection can be achieved even under normal load. It can be used under pressure.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3. 2 is a combustion chamber, 2 is a fuel pump, 3 is a fuel supply pipe, 8 is a fuel tank 110 is a cylinder cover, 9 is a fuel tank 110, and 9 is a cylinder cover.
are two fuel injection valves provided on the cylinder cover 10,
11 is a piston, 1 and 4 are branch pipes branched from the middle of the fuel supply pipe 3, and a closed container 5 is provided on the downstream side of the branch pipe 4.

A relief valve 6 that opens at a predetermined set pressure or higher is provided inside the container 5, and the branch pipe 4 is connected to the relief valve 5P6. A return pipe 7 connects the hermetic container 5 and the fuel tank 8.

In the fuel supply device equipped with the above-mentioned component parts, the fuel tank 8
The fuel oil is pressurized by a fuel pump 2 and sent to a fuel injection valve 9 via a fuel supply pipe 3 at a required injection timing, and is injected from the injection valve 9 into a combustion chamber 1.

At this time, a part of the fuel oil in the fuel supply pipe 3 is sent to the relief valve 6 via the branch pipe 4.

All of the fuel oil discharged from the relief valve 6 is captured in a closed container 5 and sent to a fuel tank 8 via a return pipe 7.

According to the present invention, as shown in FIG. 2 or 3, even if the output is increased from the normal load point A to the high load point B, the relief valve 6 opens from point 6A, and the fuel injection pressure is However, it does not increase further (Figure 2).

Alternatively, only a slight increase (Fig. 3) is required, and a higher pressure can be used at point A by this amount. or.

According to the present invention, the fuel pressure from point A to point B in FIG. 3 can be maintained at a constant pressure as shown in FIG. 2 by fully controlling the opening surface of the relief valve 6. becomes.

For example, the opening area of the relief valve 6 may be increased or decreased depending on the load, or the opening pressure of each relief valve 6 may be changed little by little by installing multiple sets of members from the branch pipe 4 to the return pipe 7. It is also possible to do so.

〔Effect of the invention〕

The present invention is constructed as described above, and the present invention has the following effects.

Under a load that is temporarily higher than when used under normal load.

By installing the fuel supply system according to the present invention in an internal combustion engine, it is possible to maintain a high fuel pressure over a wide load range from normal use to the maximum allowable load. This makes it possible to reduce the fuel consumption rate of the engine, making it possible to obtain a highly economical internal combustion engine.

[Brief explanation of drawings]

Figures 1I to 3 show one embodiment of the present invention.
The figure is a system diagram of the fuel supply system, Figures 2 and 3 are line diagrams for explaining the operation, Figure 4 is the response diagram of Figure 1 showing the conventional example, and Figure 5 is a line diagram for explaining the operation. It is. 2. Fuel pump, 3. Fuel supply pipe, 1. Branch pipe, 5. Sealing, 6. Relief valve, 7. Return pipe.
To 9... Φ Chang □ High school 2nd plate low load □ High school 3rd group 4th member - Brown J! Figure 5 (1) Page 8, line 2, ``Response'' is amended to ``Response J. Procedural amendment (voluntary) August 12, 1986

Claims (1)

[Claims] In an internal combustion engine having a fuel pump, a branch pipe branched from a fuel supply pipe connecting the fuel pump and the fuel injection valve, and a relief valve connected to the branch pipe and opened at a fuel pressure equal to or higher than a set pressure; A fuel supply device for an internal combustion engine, comprising: a closed container that accommodates the relief valve and collects fuel discharged from the relief valve.