JPH0240298Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is designed to prevent an excessive rise in fuel injection pressure in a fuel injection pipe connecting a fuel injection pump and a fuel injection nozzle of an internal combustion engine, especially a diesel engine. This invention relates to improvements in pressure control devices.

Conventionally, diesel engine fuel injection systems have been equipped with a system that suppresses the amount of fuel injected from the fuel injection nozzle during high engine speeds to reduce NOx generation and improve fuel efficiency.
Some fuel injection pipes have a leak valve installed in the middle of the fuel injection pipe to control the internal pressure of the injection pipe.

However, since conventional leak valves use coil springs to bias the valve body, the set load changes depending on the displacement of the valve body due to the spring constant of the coil spring, and the internal pressure of the injection pipe and the coil spring change. The first problem is that the set load is unbalanced.
As shown in the figure, a phenomenon in which the pipe pressure waveform oscillated was observed. As a result, there is a problem that the injection pipe internal pressure becomes unstable near the valve opening set pressure of the leak valve, and combustion becomes unstable.

Therefore, there is an invention disclosed in Japanese Patent Publication No. 47-20422, in which the leak valve is driven by oil pressure instead of the coil spring, and when the rotational speed of the engine exceeds a certain value, the oil pressure is changed to leak fuel. The device of the embodiment described in this publication controls the opening and closing of the leak valve by supplying hydraulic pressure to the bellows, and adjusts the hydraulic pressure applied to the bellows by attaching a hydraulic pressure adjustment device to a camshaft that drives a fuel injection pump. When the rotation of the camshaft exceeds a certain value, oil is leaked from the oil pressure adjustment device, and the oil pressure supplied to the bellows is lowered to leak fuel, thereby reducing the fuel injection pressure.

Therefore, the device described in the above-mentioned publication can eliminate the vibration of fuel injection pressure that occurs when the coil spring is used. However, in an internal combustion engine installed in a vehicle, there is a problem in that, for example, the lubricating oil pump requires a correspondingly larger amount, and if the supplied hydraulic pressure decreases for some reason, there is a risk that the operation of the leak valve will be hindered. Furthermore, since the device is complicated, manufacturing and maintenance costs are high, and there is still a need for improvement.

The present invention was created by focusing on the problems of the conventional leak valve, and has a simpler structure, can be operated without using external energy, and does not cause the fuel injection pressure waveform to oscillate. By suppressing the increase in fuel injection pressure when the engine rotates at high speed,
The object of the present invention is to provide a pipe pressure control device for a fuel injection device that can reduce NOx generation and improve fuel efficiency.

In order to achieve the above object, the structure of the pipe internal pressure control device of the fuel injection device of the present invention is such that the pipe internal pressure exceeds the set pressure in the middle of the fuel injection pipe connecting the fuel injection pump and the fuel injection nozzle of the internal combustion engine. A leak valve is installed that opens to release fuel from the pipe and return it to the fuel tank.
This leak valve is characterized by comprising a valve body that closes the relief pipe and a plurality of disc springs that bias the valve body in the closing direction.

In the disc spring, the amount of deflection increases non-linearly with respect to an increase in load, and the change in the amount of deflection with respect to a change in load can be reduced over a relatively wide range of load changes. Therefore, by setting this region as the region in which the leak valve is opened, it is possible to prevent the leak valve from opening and closing due to slight fluctuations in the fuel injection pressure, thereby preventing the injection pressure change from becoming oscillating.

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

FIG. 2 is an explanatory diagram of the overall configuration of the pipe internal pressure control device of the fuel injection device of this invention.

The fuel injection system for a diesel engine supplies fuel F in a fuel tank 1 to a fuel injection pump 4 via a fuel filter 3 by a feed pump 2, pressurizes the fuel F with the fuel injection pump 4, and then sends fuel F to a fuel injection pipe 5.
The fuel is injected into the cylinder from the fuel injection nozzle 6 through the fuel injection nozzle 6. 7 is a leak-off tube, 8,
9 is an overflow pipe.

In this invention, a leak valve 10 is provided in the middle of the fuel injection pipe 5, which opens when the set pressure is exceeded, and the excess fuel is returned to the fuel tank 1 from the relief pipe 11 to regulate the upper limit of the internal pressure of the fuel injection pipe 5. ing. The specific structure of this leak valve 10 is as shown in FIG.

The leak valve 10 of this invention has a cylinder 13 inside the main body casing 12 connected to the fuel injection pipe 5.
A valve body 14 for opening and closing a fuel relief passage 19 communicating between the fuel injection pipe 5 and the cylinder 13 is installed inside the cylinder 13. And this valve body 1
4 is a disc spring 2 attached to a valve shaft 16 protruding from the valve body 14.
A plurality of 0's are fitted and biased from the cylinder 13 side so that the fuel escape passage 19 is normally closed. 15 is a valve seat, 21 is a spring holder, 17 is a pressure adjustment screw that changes the opening pressure of the valve body 14 by changing the mounting load of the disc spring 20, 18 is a lock nut of the pressure adjustment screw 17, and 22 is a pressure adjustment screw. The screw attachment member 23 is a joint.

FIG. 4 is a perspective view and a longitudinal sectional view showing the shape of the disc spring 20. FIG. 5 is a diagram showing the amount of deflection and load physical properties of the disc spring 20.
0 is non-linear compared to the same characteristic of a coil spring (indicated by a broken line), and there is a portion where the load is constant with respect to changes in the amount of deflection, as indicated by arrow a.
In this invention, the pressure adjusting screw 17 causes the disc spring 20 to
Adjust so that it can be used in the area indicated by arrow a.

As a result, the leak valve 10 of this invention has a valve body 15
Since the load hardly changes with respect to the lift amount, resonance does not occur, and the control performance of the internal pressure of the fuel injection pipe 5 is high.

As explained above, the pipe internal pressure control device of the fuel injection device of this invention is provided with a leak valve whose valve body is biased by a disc spring in the middle of the fuel injection pipe connecting the fuel injection pump and the fuel injection nozzle. This eliminates vibrations in the pipe pressure waveform and provides stable fuel injection, resulting in stable combustion and reduced NOx in the exhaust gas.
The effect of reducing the amount of fuel and improving fuel efficiency becomes even greater. In addition, the injection pressure can be easily adjusted by appropriately changing the spring constant of the disc spring and the number of overlapping disc springs, and the structure is simple.Moreover, no external energy is required to operate the leak valve, so it requires less manufacturing and maintenance costs. Cost can be reduced.

The leak valve of the pipe pressure control device of the fuel injection device of this invention can be applied not only to pipe pressure control but also to other general pressure control valves.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the crank angle and the pipe pressure of a conventional fuel injection device pressure control device;
The figure is an explanatory diagram showing the overall configuration of the pipe internal pressure control device of the fuel injection device of this invention, Figure 3 is a sectional view showing the structure of the leak valve in Figure 2, and Figures 4A and B are the plates in Figure 3. A perspective view and a sectional view showing the shape of the spring, and FIG. 5 are diagrams showing the deflection-load characteristics of the disc spring. 1...Fuel tank, 4...Fuel injection pump, 5
...Fuel injection pipe, 6...Fuel injection nozzle, 10...
... Leak valve, 11 ... Relief pipe, 13 ... Cylinder, 14 ... Valve body, 16 ... Valve stem, 17 ... Pressure adjustment screw, 20 ... Belleville spring.

Claims (1)

[Scope of utility model registration request] A leak valve is provided in the middle of the fuel injection pipe that connects the fuel injection pump and the fuel injection nozzle of the internal combustion engine, and is opened when the pipe internal pressure exceeds a set pressure to release the fuel and return it to the fuel tank from the pipe. A pipe internal pressure control device for a fuel injection device that is comprised of a valve body that closes a pipe and a plurality of disc springs that bias the valve body in the closing direction.