JPS6332364Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the performance of a fuel injection system for an internal combustion engine.

The configuration of a conventional fuel injection system is shown in FIG. In the figure, 10 is a fuel injection pump main body, 20 is a plunger, 30 is a discharge valve, 31 is a discharge valve spring, 32
4 is a discharge valve chamber, 40 is a fuel injection pipe, 50 is a fuel injection valve main body, and 51 is a nozzle tip portion.

The plunger 20 is operated by an injection cam (not shown).
The compressed fuel pushes up the discharge valve 30 against the spring 31 and enters the discharge valve chamber 32, and further generates a pressure wave within the injection pipe 40, which enters the fuel injection valve 50. An automatic valve (not shown) provided inside is pushed up, and the fuel is injected into the engine combustion chamber from the nozzle or nozzle at the tip of the nozzle tip portion 51.

The main structure of this fuel injection system is schematically shown in FIG. 2, and conventional injection systems generally have injection pipes with a uniform cross-sectional area.

In conventional injection systems, there is a nozzle orifice constrictor at the tip of the nozzle tube with a uniform cross-sectional area, and the pressure wave propagating inside the nozzle increases the pressure at the nozzle hole and is injected. A portion of the wave energy is reflected back to the fuel injection pump, where it is reflected again to generate secondary injection. The size of the reflected wave is as shown in Figure 2.
When A _P is the cross-sectional area of the injection pipe and A _N is the cross-sectional area of the nozzle, the larger A _P /A _N is, the larger the secondary injection is likely to occur. In order to prevent this, a large amount of suction and return action is required at the discharge valve portion on the pump side, but if it is too large, cavitation will occur. To prevent this, reducing A _P to reduce A _P /A _N generally improves the sharpness at the end of injection, but
The pressure on the pump side becomes high, which tends to cause problems in the durability of the cam and pump. Note that A _PL is the plunger cross-sectional area, L _P is the injection pipe length, and P _O is the valve opening pressure.

As described above, in conventional injection systems with uniform cross-section injection pipes, secondary injection or cavitation is likely to occur; if the injection pipe is thin, the pressure drop will increase and the pressure on the pump side will increase, and if the injection pipe is thick, the pressure will increase. The descent is slow and the injection is not sharp.

The purpose of this invention is to focus on the above points, and in the fuel injection system of a diesel engine, the pressure on the fuel injection pump side is lowered and the pressure on the nozzle side of the fuel injection valve is increased, thereby injecting high-pressure fuel and preventing injection cut-off. Our goal is to provide a fuel injection device that can improve the performance of diesel engines at a low cost.The main feature of this system is that the fuel injection pipe has a cross-sectional shape that is closer to the fuel injection valve than the circular shape on the fuel injection pump side. The shape is gradually deformed into an elliptical shape on the nozzle side, and the cross-sectional area is made smaller as it approaches the nozzle side from the fuel injection pump side.

The present invention can be applied to diesel engines, fuel-injected stratified combustion engines, and dual-fuel engines.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic diagram showing one embodiment of the fuel injection system according to the present invention.

In the figure, the ellipse is replaced with a combination of a semicircle and a rectangle to simplify calculations, but since there is no essential difference due to this replacement, the following description will be based on this.

The length corresponding to the injection pipe 11 is L _P , the inner diameter of the pipe end on the fuel injection pump side (this is circular) is D _P , and the shape of the middle is a semicircle with a diameter d and the vertical length d. , and a rectangle with horizontal length l.

In this process of flattening the injection pipe, the peripheral length is kept the same while being gradually deformed, so the cross-sectional area ratio based on the fuel injection pump side pipe end is as follows.

Fuel injection pump side pipe end cross-sectional area: π/4D _P ² pipe cross-sectional area: π/4d ² +d・l Pipe cross-sectional area ratio: A _R =π/4(d ² +d・l)/π/4D _P ^2Here , since the circumferential lengths are the same, πD _P = πd+
2l, therefore l=π/2(D _P -d), substituting l into the formula of A _R , A _R = -{(d/D _P )-1} ² +1 Therefore, the pipe cross-sectional area ratio is as shown in Figure 4.

Here, if an area change equivalent to that of a tapered injection tube is obtained with the injection tube according to the present invention, the tube shape is determined by finding d according to the cross-sectional area ratio of the middle part of the tube from FIG.

As an example, an injection pipe that has the same cross-sectional area change as a tapered pipe with an inner diameter of 2.0 mm at the pump end and a 1.6 mm inner diameter at the nozzle end is shown in FIG.

Figure 5a shows the change in the cross-sectional area of the pipe according to the present invention, where (a) is the end of the pump side pipe, D _P1 = 2.0 mm, (b) is the central part, d ₂ = 1.13 mm, and (h). ) is the nozzle side tube end, d ₃
=0.8mm. The _{corresponding} changes in the pipe cross-sectional area of the tapered injection pipe are shown in _Figure 5b. ) D _P3 = 1.6 mm at the nozzle side tube end.

In this way, the cross-sectional area through which the fuel passes gradually decreases from the pump side to the nozzle side.

The operation in the case of the above configuration will be described.

A fuel injection device having an injection pipe whose cross-sectional area decreases from the fuel injection pump side to the injection nozzle side has the following effects: (1) improvement in average injection pressure; (2)
It is possible to shorten the injection period, (3) improve the sharpness of injection, and (4) prevent secondary injection.

In addition, since the injection tube of the present invention is manufactured by gradually flattening the conventional circular injection tube, it has the advantage of being easy to manufacture.

The above case has the following effects.

As a result of the above actions, the combustion performance of the engine is improved (reduced exhaust smoke, particulate matter, and fuel efficiency).
It has great effects and can be provided at low cost.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing a conventional fuel injection system, Figure 2 is an explanatory diagram showing a conventional fuel injection system.
The figure is a schematic diagram of the fuel injection system in Figure 1, Figure 3 is a schematic diagram of the fuel injection system of one embodiment of the present invention, Figure 4 is a diagram showing changes in the tube cross-sectional area ratio, and Figure 5 a. is an explanatory diagram showing changes in the pipe cross-sectional area of the injection pipe according to the present invention,
FIG. 5b is an explanatory diagram showing changes in the cross-sectional area of the tapered injection pipe. 11...Fuel injection pipe.

Claims (1)

[Scope of utility model registration request] In a fuel injection device having a fuel injection pipe in the fuel injection system, the fuel injection pipe gradually changes its cross-sectional shape from a circular shape on the fuel injection pump side to an elliptical shape on the nozzle side of the fuel injection valve, and also has a cross-sectional shape on the fuel injection pump side. A fuel injection device characterized in that the cross-sectional area becomes smaller as it approaches the nozzle side.