JPH0141909Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel supply device for a fuel injection pump of a diesel engine or the like.

[Prior art]

In a bottle-type fuel injection pump 10 with independent cylinders used in a diesel engine as shown in the schematic system diagram of FIG. 1, if the fuel injection amount is small relative to the diameter of the lower plunger 12, fuel injection ends After that, a second fuel inlet joint 14 provided at the fuel inlet of the fuel injection pump
A backflow of fuel as shown in the figure occurs, which becomes a pulsating wave and is transmitted into the fuel intake pipe 17. At this time, a head difference H is generated between the fuel tank 15 and the fuel injection pump 10. However, there are some parts where the pressure is negative, and bubbles 18 are generated, and the bubbles 18 are sucked into the fuel injection pump 10 without disappearing.
There is a problem in that it causes problems such as fluctuations in engine speed.

In FIG. 1, the fuel tank 15 is connected to the fuel suction joint 14 of the fuel injection pump 10 through a fuel communication joint 16 and a fuel suction pipe 17, and the plunger 12 is returned by a fuel cam (not shown). By being pressed against the spring force of the spring 13, pressurized fuel is discharged from the delivery valve holder 11 side.

Therefore, in order to reduce the bubbles 18 generated due to spill and to prevent spill from occurring near the fuel suction port of the fuel injection pump 10, even if a spill occurs, the fuel suction port of the fuel injection pump 10, Or in the middle of the fuel intake pipe 17 connecting the fuel injection pump 10 and the fuel tank 15,
Furthermore, it has been considered to provide a constriction section at the outlet of the fuel tank 15 with a cross-sectional area smaller than the passage cross-sectional area of the fuel suction pipe 17, but even in this case, the The bubbles 18 caused by the spill created resistance at the constriction part and did not escape to the fuel tank 15 side, and there was no means to extract the bubbles accumulated there, so the fuel supply to the fuel intake port of the fuel injection pump was stable. The problem is that it cannot be done.

Conventional pumps generate a large amount of bubbles, but some of the generated bubbles are sucked into the pump again, causing hunting and irregular injection. The remaining air bubbles return to the tank from the open tank.

[The problem that the idea attempts to solve]

The present invention was devised to solve the above-mentioned conventional problems. Under normal operating conditions, the throttle part stabilizes the metering of the fuel injection pump and also removes air bubbles that have accumulated in the fuel intake pipe. The object of the present invention is to provide a fuel supply device for a fuel injection pump having an easy fuel supply.

[Means to solve the problem]

That is, the fuel supply device of the present invention includes, in the fuel suction pipe of the fuel injection pump, a large diameter passage having a passage cross-sectional area large enough to extract air bubbles accumulated near the inlet of the fuel injection pump; A fuel pot is provided with a small-diameter passage with a restrictor having a passage cross-sectional area large enough to relieve pressure reduction due to negative pressure spill fuel flowing back from the inlet of the fuel injection pump, and a handle rotation of the fuel pot is provided. The fuel supply device for a fuel injection pump is characterized in that the large-diameter passage and the small-diameter passage can be selectively communicated with a fuel tank depending on a dynamic operation.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings, and FIG. 3 shows the main parts of the fuel supply device for the fuel injection pump 10 in Embodiment 1 of the present invention.
It has almost the same configuration as the fuel injection pump 10 in the conventional example shown in FIG.
A fuel tank 19 is installed. This fuel tank 19 has a passage 20 having an inner diameter D that is approximately the same as the inner diameter D of the fuel intake pipe 17, that is, a passage cross-sectional area that is approximately the same as the internal cross-sectional area of the pipe, and a passage 20 that has a passage cross-sectional area that is smaller than the internal cross-sectional area of the pipe. A passage 21 with a throttle is provided inside.

That is, this fuel tank 19 can be operated in a state where the engine is stopped, with both the passages 20 and 21 closed, as shown in FIG. In addition, as shown in FIG. 5 and FIG. 6, which is a vertical cross-sectional view in the - direction of FIG. Three types of switching are possible, including a state in which the air bubbles 18 are easily extracted to the fuel tank 15 side.

Spill bubbles occur because fuel pressurized to a high pressure for injection is rapidly depressurized when it is released from the plunger lead to the pump suction pipe (atmospheric pressure) at the end of injection. Therefore, if a throttle is provided in the fuel suction pipe, the reduced pressure caused by spill in the vicinity of the pump will be alleviated, and the generation of bubbles will be reduced. When a diaphragm is provided, the amount of bubbles is greatly reduced compared to one without a diaphragm, but it cannot be completely eliminated.

In addition, under normal operating conditions, the throttled passage 21 increases the pressure of the fuel injection pump 10 during metering and stabilizes metering, thereby stabilizing the rotational speed of the diesel engine.

In FIG. 3, 22 is a fuel filter, and other parts that are the same as those in the conventional example shown in FIG. 1 are designated by the same part numbers.

Next, FIG. 7, FIG. 8, and FIG. 9 show a fuel pot 19 used in the fuel supply device in Embodiment 2 of the present invention, which has almost the same configuration and function as Embodiment 1. However, as shown in FIG. 7, a passage 20 installed inside the fuel pot 19 and formed with a passage cross-sectional area larger than the internal cross-sectional area of the fuel suction pipe 17 prevents air bubbles 18 from forming when the fuel pot 19 is closed. This becomes an air reservoir, and if the engine is left in the closed state shown in FIG. 7 after the engine has stopped, air bubbles 18 separated from the fuel will rise and become air, which will accumulate in this air reservoir.

Next, when the fuel tank 19 is switched from FIG. 7 to FIG. 9 during engine operation, the air in the bubbles 18 escapes to the fuel tank 15 side as shown in FIG. Normal operation can be carried out in which fuel is sent to the fuel injection pump 10 from the passage 21 with a restriction while the cock 19 is open.

That is, during the rotation of the fuel pot 19 between closing and opening,
Since the air bleed state is provided, air bubbles 18 can be surely and automatically bleed by opening and closing the fuel pot 19 when the engine is in use, without having to be particularly conscious of air bleed.

[Effect of idea]

Therefore, by applying the fuel supply device of the present invention, under normal operating conditions of the diesel engine, the pressure at the time of metering of the fuel injection pump increases due to the throttle passage provided in the fuel tank, and metering is prevented. This has the effect of stabilizing the engine rotation speed, and it also allows the air bubbles that have accumulated in the fuel intake pipe to be directed to the fuel tank, making it easier to rotate the fuel handle even when the engine is running. Accordingly, by selectively communicating the large-diameter passage and the small-diameter passage with the fuel tank, it is possible to facilitate extraction.

Note that the present invention can be effectively applied mainly as a fuel supply device for a diesel engine.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional schematic system diagram of a conventional diesel engine fuel supply system, Fig. 2 is a vertical sectional view of the main part of the fuel intake pipe in Fig. 1, and Fig. 3 is a first embodiment of the present invention. A partial cross-sectional side view of the fuel supply device in
Figures 4 and 5 are longitudinal cross-sectional views of the main parts of the fuel tank shown in Figure 3 in each switching state, and Figure 6 is the - of Figure 5.
7, 8, and 9 are longitudinal sectional views of essential parts of the fuel supply device in each switching state of the fuel supply device according to the second embodiment of the present invention. DESCRIPTION OF SYMBOLS 10...Fuel injection pump, 15...Fuel tank, 17...Fuel suction pipe, 19...Fuel tank, 20...Passage, 21...Passage (with throttle).

Claims (1)

[Scope of utility model registration request] The fuel suction pipe of the fuel injection pump has a large diameter passage having a passage cross-sectional area large enough to remove air bubbles accumulated near the inlet of the fuel injection pump, and a negative passage that flows backward from the inlet of the fuel injection pump. A fuel pot is provided with a small diameter passage with a restriction having a passage cross-sectional area large enough to alleviate the decompression caused by the pressure spill fuel, and the large diameter passage and A fuel supply device for a fuel injection pump, characterized in that each of the small-diameter passages can be selectively communicated with a fuel tank.