JPS6115250Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for internal combustion engines, particularly diesel engines.

2. Description of the Related Art Conventional fuel injection devices of this type and fuel injection valves used therein include those shown in FIGS. 1 and 2, for example. In the same figure, 1
is a fuel injection valve, which sends high-pressure fuel pumped from an injection pump 2 through a passage 4 from a fuel inlet 3 to a nozzle 5, and then to an oil reservoir chamber 7 below a needle 6. When the oil pressure in the oil reservoir chamber 7 increases in this way, the force of the nozzle spring 9, which had hitherto brought the needle 6 into contact with the seat surface via the push rod 8 to prevent fuel leakage, is overcome, and the needle 6 is lifted and the nozzle 5
Fuel is injected from the tip. Further, the nozzle 5 is screwed together with a distant piece 12 to a nozzle body 10 by a nozzle holder 11 to prevent fuel leakage.

The fuel leaking from the gap between the needle 6 and the nozzle 5 is transferred from the spring chamber 13 to the return passage 14.
The fuel is then returned from the fuel outlet 15 to the fuel tank 17 via the spill tube 16.

Next, the fuel injection system of the fuel system will be explained in more detail with reference to FIG.

First, from the fuel tank 17 to the fuel supply pipe 1
8, the fuel prepressurized by the fuel pump 19 is sent to the fuel filter 21 through the conduit 20, where the fuel is filtered and excess fuel is discharged through the overflow valve 22 and the conduit 23 to the fuel tank 17. Return to

The filtered fuel is then sent to the injection pump 2 through the conduit 24, and the fuel metered and pressurized is sent to the fuel injection valve 1 through the injection tube 25.

The injection pump 2 also increases the pressure of the fuel pre-pressurized by the fuel pump 19 using a plunger piston (not shown), pushes open a delivery valve (not shown), and sends the fuel to the injection tube 25 at high pressure. act.
Note that, like the check valve, the delivery valve functions to allow fuel from the injection pump 2 to pass through, but not to allow fuel from the injection tube 25 to pass through.

However, in such a conventional fuel injection device, fuel metered and pressurized by the injection pump 2 is passed through a long (for example, 400 to 600 mm) injection tube 25 to the fuel injection valve 1.
Since the fuel was configured to be sent to the injection tube 25, pressure waves generated within the injection tube 25 caused pressure fluctuations in the fuel, which were transmitted to the nozzle 6 and caused subsequent injection, cavitation, etc.
In addition to causing various irregular injections, pressure fluctuations themselves have a large effect on the injection characteristics and injection rate.
This was also an obstacle to increasing the injection pressure.

The present invention has been made by focusing on such conventional problems, and includes an injection pump that pressurizes fuel and supplies it to a fuel injection valve via an injection tube, and a combination of the injection tube and the fuel injection valve. A piston is provided in the passage between the nozzle and the piston and is movable in the axial direction according to the pressurized pressure of the fuel. and another fuel feed pump that supplies fuel at a pressure higher than the pressure when the injection pump is not pressurizing and pumping, and a constant supply pressure is maintained in the passage when the injection pump is stopped. To provide a fuel injection device which eliminates causes of unauthorized fuel injection such as pressure fluctuations due to pressure waves generated within an injection tube 25.

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

FIG. 3 shows the electromagnetic injection valve of the present invention. A needle 31 is fitted into the nozzle 32 and screwed together with a distant piece 33 to a nozzle body 35 by a nozzle holder 34.
The needle 31 is pushed into the seat surface 39 of the nozzle 32 by a nozzle spring 38 in a spring chamber 37 in the nozzle body 35 via a push rod 36.
The fuel is sealed.

This seat force is precisely adjusted by shims 40.

On the other hand, reference numeral 41 denotes a fuel introduction connector connected to a feed pump, which will be described later.A check valve 42 attached to this connector is pushed open against a check valve spring 43, and a fuel passage 44 is connected to an oil reservoir chamber 4.
It is designed to supply fuel to 5. Note that when the pressure in this oil reservoir chamber 45 increases, the needle 3
1 is pushed up and fuel is injected from the nozzle port 46. Further, a portion of the fuel passing through the check valve 42 is sent to a pressure chamber to be described later. A pressure chamber 47 is provided in a passage that intersects with the fuel passage 44 and each passage of the check valve 42, and is formed between a cylinder 48, a piston 49, and a stopper 50, which are connected to a spacer by a pressure introduction connector 51 screwed into the fuel inlet. It is screwed together with 52. Note that 53 and 54 are return passages and fuel outlets for returning fuel leaking between the nozzle 32 and the needle 31 to the fuel tank.

FIG. 4 is a system diagram of the fuel injection device of the present invention. This differs from the one shown in FIG. 1 in that fuel is sent from a conduit 24 downstream of the fuel filter 21 to a fuel introduction connector 41 by a feed pump 55. Note that here, the delivery valve (not shown) provided on the injection pump 2 immediately before the injection tube 25 is unnecessary and is therefore removed.

The feed pump 55 has a fuel pressure of 4 to 50 kg/cm ² , but it is preferable to use an electromagnetic pump for ⁴ to 10 to 20 kg/cm ² and a mechanically driven pump for 10 to 20 to 50 kg/cm 2 .

Next, the action will be described.

First, at the end of fuel injection, the pressure sent from the injection pump 2 to the pressure introduction connector 51 via the injection tube 25 decreases, and the pumping pressure of the fuel pump 19 (2Kg/cm ²
degree). At this time, the piston 49 moves so as to approach or come into contact with the stopper 50, and the volume of the pressure chamber 47 decreases.

On the other hand, after fuel injection, the feed pump 55 has a higher pressure than that pumped by the fuel pump 19.
Since more pressure-fed fuel (approximately 4 to 50 kg/cm ² pressure) is sent from the fuel introduction connector 41 to the fuel passage 44, the piston 49 gradually moves inside the cylinder 48 toward the pressure introduction connector 51. However, immediately before the next injection, the state returns to approximately the state shown in FIG. 3.

Next, high-pressure fuel is pumped from the injection pump 2, and when it reaches the fuel introduction connector 51, high pressure (100 to 200 Kg/cm ² or more) is applied from the pressure introduction path 56 to the pressure receiving end 57 of the piston 49. As a result, the piston 49 moves within the cylinder 48 and reduces the volume of the pressure chamber 47. The fuel in the pressure chamber 47 is thereby compressed and sent to the fuel passage 44 at a high pressure substantially equal to the pressure of the fuel supplied from the injection pump 2. Therefore, the check valve 42 is closed, and high-pressure fuel reaches the oil reservoir chamber 45, pushes up the needle 31, and is injected from the injection port 46.

In such a system, the fuel from the pressure chamber 47 is injected through the extremely short fuel passage 44, so although pressure fluctuations occur in the fuel passage 44 due to pressure reflection, these fluctuations are at a very high frequency and do not affect the injection characteristics. It has almost no effect. That is, the inertia of the piston 49, needle 31, and fuel cancel out high-frequency pressure fluctuations.

This reduces the occurrence of fuel injection and cavitation. In addition, pressure fluctuations at the end of injection are absorbed by the piston 49 if the pressure becomes high, and if the pressure drops too much, the check valve 42 opens and fuel is supplied, further suppressing the occurrence of post-injection or cavitation. .

Furthermore, the fuel flowing from the injection pump 2 through the injection tube 25 and from the pressure introduction path 56 to the pressure receiving end 57 of the piston 49 is also subject to pressure fluctuations due to pressure reflection.
9 and the movement inertia of the piston 49, the influence on the pressure in the pressure chamber 47 is reduced.

In addition, if there is a piston 49, the pressure drop from the ignition tube 25 will also be caused by fuel (light oil).
Due to the incompressibility of the piston 49, the piston 49 only needs to move slightly toward the injection tube 25, so there is no need to suddenly bring the gauge pressure close to 0 kg/ ^cm2. Because of its small volume, it can be lowered relatively slowly, and the occurrence of cavitation etc. can be alleviated.

Note that normally, the fuel in the injection tube 25 is not replaced by the above action, so the temperature becomes high if the fuel is compressed many times. Therefore, the fuel is exchanged by allowing the fuel to leak from the pressure chamber 47 to the injection tube 25 through the fitting gap between the piston 49 and the cylinder 48.

FIG. 5 shows another embodiment of the fuel injection valve.

This differs from the one shown in FIG. 3 in that a leak passage 62 having an orifice 61 in the axial direction is formed in the center of the piston 60. The diameter of the orifice 61 of this leak passage 62 is desirably 1/4 or less of the pressure introduction passage 56, for example, 0.4 to 0.5 mmφ or less, so that the fuel in the injection tube 25 can be replaced smoothly.

Furthermore, even if pressure fluctuations in the injection tube 25 or the fuel passage cannot be sufficiently absorbed due to the inertia of the piston 70, the reaction force fluctuations can be absorbed by releasing a small amount of pressure to the pressure side of the piston 70 through the orifice 61. It can be done effectively.

As explained above, according to the present invention, the pistons 49, 60 are provided on the injection tube 25 side of the fuel injection valve.
By connecting a fuel feed pump between the injection pressure and the nozzle that supplies a pressure lower than the injection pressure and higher than the pressure when the injection pump 2 is not pumping fuel at high pressure, the injection tube 25 and the fuel passage It suppresses pressure fluctuations that occur during injection, eliminates after-injection, cavitation, and other causes of injection irregularities, improves fuel efficiency, purifies exhaust gas such as smoke, and achieves high-pressure and high-speed injection.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional fuel injection device, Fig. 2 is a sectional view of the fuel injection valve thereof, Fig. 3 is a sectional view of the fuel injection valve of the present invention, and Fig. 4 is a diagram of the fuel injection device of the present invention. The system diagram, FIG. 5, is a sectional view showing another embodiment of the fuel injection valve. 2...Injection pump, 19...Fuel pump, 21...Fuel filter, 2
5... Injection tube, 31... Needle, 32... Nozzle, 42... Valve, 44...
...Fuel passage, 45...Oil sump, 46...Nozzle, 4
7...Pressure chamber, 49...Piston, 55...Feed pump.

Claims (1)

[Scope of utility model registration request] The injection pump pressurizes the fuel from the fuel pump and supplies it to the fuel injection valve via the injection tube, and the fuel injection pump is provided in a passage between the injection tube and the nozzle of the fuel injection valve. A piston that is movable in the axial direction in accordance with the pressurizing force of A fuel injection device for an internal combustion engine, characterized in that it supplies fuel and maintains a constant supply pressure within the passage.