JPH0454830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fuel injection device for a diesel engine, and more specifically, the present invention relates to a fuel injection device for a diesel engine, and more specifically, a fuel injection device for a diesel engine, particularly a large diesel engine for ships, etc., is equipped with a fuel injection pressure increasing device. It is used to improve performance during low output operation.

BACKGROUND ART As is well known, in a diesel engine, fuel oil discharged from a fuel pump passes through a high-pressure pipe, is injected into a cylinder from a fuel valve attached to a cylinder cover, and is combusted. Since the plunger diameter of the fuel pump, the area of the fuel valve nozzle, etc. are constant, the specifications of the fuel injection system cannot be changed during operation.

Problems to be Solved by the Invention As mentioned above, the specifications of the fuel injection system of conventional diesel engines cannot be changed during operation, so the fuel oil injected from the fuel valve nozzle is
The higher the load operation is, the higher the injection pressure is, resulting in better atomization and better combustion.On the other hand, the lower the load operation is, the lower the injection pressure is, resulting in poor atomization and poor combustion. be. In other words, the fuel injection system of a conventional diesel engine is
As the load becomes lower, the atomization condition of the fuel oil injected into the cylinder becomes worse, leading to problems such as poor combustion and generation of black smoke. The present invention attempts to solve these problems. That is, an object of the present invention is to provide a fuel injection device for a diesel engine that is capable of increasing the residual pressure in a fuel high-pressure pipe during low-load operation to improve fuel atomization and combustion by increasing the injection pressure. That is.

Measures to solve the problem A residual pressure adjustment device is installed in parallel with the high pressure pipe to the fuel valve, and the pressure of the pressure adjustment spring of this residual pressure adjustment device can be changed, so that the residual pressure can be freely adjusted externally. This makes it possible to increase the residual pressure during low load operation. That is, the configuration of the present invention includes a residual pressure adjusting device between the fuel pump and a high-pressure pipe connecting the fuel valve of the diesel engine and the discharge side of the fuel pump, and The adjustment device includes a fuel oil communication pipe provided in the residual pressure adjustment device main body and connected to the middle of the high pressure pipe, and a fuel oil communication pipe provided in the main body and connected to the oil passage between the intake valve and the overflow valve of the fuel pump. A fuel oil return pipe that communicates with the main body is incorporated into the main body and operates to allow fuel oil to flow into the main body from the high pressure pipe through the fuel oil communication pipe and to prevent outflow. a pressure regulating spring that is incorporated into the main body and presses the check valve toward the fuel oil communication pipe;
It is characterized by comprising a pressure adjustment eccentric shaft that is incorporated into the main body and allows the pressing force of the pressure adjustment spring to be adjusted from the outside of the main body.

Operation The pressure adjustment eccentric shaft is operated manually or by an appropriate device to raise the residual pressure to an appropriate value during low load operation, thereby increasing the fuel oil injection pressure and reducing the fuel injection pressure even during low load operation. It is possible to improve oil atomization and improve combustion.

Example FIG. 1 shows an embodiment of the invention.

In Fig. 1, 1 is a combustion valve, 2 is a high pressure pipe, and 3 is a combustion valve.
4 is a residual pressure adjusting device, 4 is a fuel pump, and 5 is a cam. Further, 31 is a casing-shaped residual pressure adjusting device main body, 32 is a check valve made of a ball, 33 is a pressure adjustment spring, 34 is a pressure adjustment eccentric shaft, 35 is a fuel oil return pipe, 36 is a fuel oil communication pipe, 41 is a Suction valve, 42
is a discharge valve, 43 is an overflow valve, 44 is a plunger, 4
5 is an overflow valve rod, 46 is an intake valve rod, 47 is a roller, 48 is a plunger chamber, 61 is an arrow indicating the inflow of fuel oil, and 62 is an arrow indicating the return of fuel oil.

That is, as shown in an enlarged view in FIG.
6, a fuel oil return pipe 35 provided in the main body 31 and communicating with the oil passage between the suction valve 41 and the overflow valve 43 of the fuel pump 4, and a fuel oil communication pipe incorporated in the main body 31. A check valve 32 that operates in a direction that allows fuel oil to flow into the main body 31 from the high pressure pipe 2 through the main body 36 and prevents the fuel oil from flowing out; a pressure adjustment spring 33 that presses the fuel oil toward the fuel oil communication pipe 36;
The pressure adjusting eccentric shaft 34 is incorporated into the main body 31 and allows the pressing force of the pressure adjusting spring 33 to be adjusted from the outside of the main body 31.

In the diesel engine fuel injection system configured as shown in FIG. 1, when the roller 47 of the fuel pump 4 is on the base circle of the cam 5,
Plunger 44 is at bottom dead center and overflow valve 43 is closed. Conversely, since the suction valve 41 is at the top dead center and open, fuel oil is flowing into the plunger chamber 48 through the suction valve 41, as shown by arrow 61. Then, as the cam 5 rotates (rotates counterclockwise in FIG. 1), the plunger 44 begins to rise. Also, the overflow valve rod 45 starts to rise at the same time, but the suction valve rod 46 goes down, and the suction valve 41 closes at point A shown in FIG. When the fuel oil is compressed and the pressure becomes higher than the pressure inside the high pressure pipe 2, the discharge valve 42 is pushed up to send the fuel oil to the fuel valve 1 and inject it. On the other hand, plunger 4
As the plunger chamber 4 rises, the overflow valve rod 45 rises, and the overflow valve 43 opens at point B in FIG.
Since the high pressure fuel oil of 8 flows out as shown by arrow 62, the discharge valve 42 closes and the injection of fuel oil ends.

In the above, while the fuel oil is being injected, the high-pressure oil in the plunger chamber 48 is applied equally to the front and back (left and right in FIG. 1) of the check valve 32 of the residual pressure adjustment device 3, so The stop valve 32 has a pressure adjustment spring 33
It remains closed due to the pressing force (force pressing leftward in Fig. 1). However, the third
The overflow valve 43 opens at point B in the figure, and the plunger chamber 48
When the oil pressure decreases, the discharge valve 42 immediately closes, so that a high pressure lower than the opening pressure of the fuel valve 1 remains in the high pressure pipe 2. When this residual pressure is higher than the pressing force of the pressure adjustment spring 33 of the check valve 32, the check valve 32 opens to adjust the residual pressure. Therefore, if the pressure adjustment eccentric shaft 34 is rotated manually or by an appropriate device, the residual pressure will be proportional to the compression length of the pressure adjustment spring 33 (generally called spring tension). and change. That is, the eccentric shaft 3
4 and adjust the compression length of the pressure adjustment spring 33, the residual pressure can be adjusted. Adjust with 34.

FIG. 4 shows the pressure of the fuel oil at the inlet of the fuel valve 1, that is, the pressure waveform of the fuel oil in the high-pressure pipe 2. Conventionally, the residual pressure was shown as a solid line, but
According to the apparatus shown in FIG. 1, the residual pressure can be increased as shown by the dotted line, and the residual pressure is increased accordingly during low load operation, so that good combustion is maintained even during low load operation.

Effects of the Invention The present invention includes a residual pressure adjustment device between the fuel pump and a high-pressure pipe connecting the fuel valve of the diesel engine and the discharge side of the fuel pump, so that The residual pressure can be adjusted accordingly, and therefore the combustion state during low load operation can be improved without impairing the fuel injection state and engine performance during high load operation. In other words, even at low loads, lower fuel costs, less smoke, and less fouling of the combustion chamber can be expected. In addition, the residual pressure adjustment device incorporates a pressure adjustment eccentric rod that can externally adjust the pressing force of the pressure adjustment spring that presses the check valve. There is no need to stop the engine, and the residual pressure can be adjusted externally to the optimal level according to the load during operation. Therefore, automatic operation using the engine load, etc. as an input signal is possible. ,
Optimal control of the fuel injection system is also possible.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the residual pressure adjusting device shown in Fig. 1, and Fig. 3 is a stroke and suction of the plunger shown in Fig. 1. An explanatory diagram showing the relationship between the lift of the valve and the overflow valve,
FIG. 4 is an explanatory diagram showing the relationship between the residual pressure when the residual pressure is increased by the device shown in FIG. 1 and the conventional residual pressure. 1...Fuel valve, 2...High pressure pipe, 3...Residual pressure adjustment device, 4...Fuel pump, 5...Cam, 31...
Residual pressure adjustment device body, 32... Check valve, 33... Pressure adjustment spring, 34... Pressure adjustment eccentric shaft, 35...
Fuel oil return pipe, 36...Fuel oil communication pipe, 41...
Suction valve, 42...discharge valve, 43...overflow valve.

Claims (1)

[Claims] 1. A residual pressure adjustment device is provided between the fuel pump and a high-pressure pipe connecting the fuel valve of the diesel engine and the discharge side of the fuel pump, and this residual pressure adjustment device has a residual pressure A fuel oil communication pipe provided in the regulator body and connected to the middle of the high pressure pipe; and a fuel oil return pipe provided in the main body and communicated with an oil passage between the intake valve and the overflow valve of the fuel pump. a check valve that is incorporated into the main body and operates in a direction to allow fuel oil to flow into the main body from the high pressure pipe through the fuel oil communication pipe and to prevent the fuel oil from flowing out; a pressure regulating spring that is incorporated into the main body and presses the check valve toward the fuel oil communication pipe;
A fuel injection device for a diesel engine, comprising: a pressure adjustment eccentric shaft that is incorporated into the main body so that the pressing force of the pressure adjustment spring can be adjusted from outside the main body.