JPH0220461Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pressure booster plunger type fuel injection device.

[Conventional example]

FIG. 1 shows a conventional general pressure booster plunger type fuel injection device.

Reference numeral 1 designates a fuel pump that pumps fuel oil from a fuel tank 2 to a fuel chamber 4 and a cylinder chamber 7 of a pressure booster plunger 3, and an accumulator 13 and a regulator 14 for keeping the fuel oil pressure constant are provided in the oil feeding path. is provided. Further, a spool valve 5, which is a switching valve, is provided between the fuel pump 1 and the cylinder chamber 7. This spool valve 5
The spool 11 is moved by the action of the solenoid 10, and the cylinder chamber 7 of the pressure booster plunger 3 is connected to the fuel pump 1 during the injection stroke, and the cylinder chamber 7 of the pressure booster plunger 3 is connected to the reflux pipe 8 during the metering stroke. It is connected to. and reflux pipe 8
A solenoid valve 9 is provided in the middle of the pipe to measure the amount of fuel oil flowing through this pipe.

In the metering stroke, the plunger 6 of the pressure booster plunger 3 is raised by the fuel oil sent from the fuel pump 1 to the fuel chamber 4 via the check valve 15, and spools the fuel oil in the cylinder chamber 7 of the pressure booster plunger 3. A reflux pipe 8 provided with a metering solenoid valve 9 via a valve 5
The fuel is then returned to fuel tank 2. Then, by shutting off the electromagnetic valve 9 after a set time determined by the engine output, the amount of fuel oil flowing through the return pipe 8, that is, the amount of fuel oil supplied to the fuel chamber 4 is measured. ing.

In the injection stroke after completion of metering, the spool 11 is switched by the action of the solenoid 10, and the fuel oil from the fuel pump 1 is introduced into the cylinder chamber 7 of the pressure booster plunger 3 and acts on the large diameter plunger 6a. Fuel in the fuel chamber 4, which has been made highly pressurized by the small-diameter plunger 6b, is injected from the fuel injection nozzle 12.

In such a fuel injection device that utilizes hydraulic pressure (fuel pressure), control of the fuel injection amount, that is, control of the amount of fuel oil entering the fuel chamber 4 of the pressure booster plunger, is an important factor.

However, in a device like the fuel injection device shown in FIG. 1, in which the amount of fuel oil is controlled by the opening time of the metering solenoid valve 9 installed in the recirculation pipe 8,
There is a problem in that the amount of fuel cannot be accurately measured due to fuel leakage in the spool valve 5.

In order to solve this problem, a metering solenoid valve 9 is installed in the pipeline between the spool valve 5 and the pressure booster plunger 3.
However, since this conduit is brought to high pressure by the pressure booster plunger 3, a high-speed, high-pressure solenoid valve 9 must be used, which is difficult to manufacture. , it was not feasible.

[Purpose of invention]

The purpose of this invention is to solve the problems of the metering device of the conventional pressure booster plunger type fuel injection system, so that there is no leakage of fuel from the spool valve during metering, and high fuel pressure is not applied to the metering solenoid valve during injection. An object of the present invention is to provide an excellent pressure boosting plunger type fuel injection device.

[Structure of the idea]

In order to achieve the above object, the pressure booster plunger type fuel injection device of the present invention has an inverted fuel oil supply pipe 16 connecting the switching spool valve 5 connected to the fuel pump 1 and the cylinder chamber 7 of the pressure booster plunger 3. Stop valve 1
7, and a spill port 3b for communicating the cylinder chamber 7 with the fuel tank 2 when the large diameter plunger 6a of the pressure booster plunger 3 reaches the bottom dead center is provided on the side of the cylinder chamber 7, In the middle of the fuel oil discharge pipe 18 connecting with the fuel tank 2,
The present invention is characterized in that a normally closed electromagnetic on-off valve 20 is provided which opens the current when the large diameter plunger 6a reaches the bottom dead center.

〔Example〕

Hereinafter, an embodiment of the pressure booster plunger type fuel injection system of the present invention will be described with reference to the drawings, and the same components as those of the conventional example shown in FIG. 1 will be given the same reference numerals.

FIG. 2 is a schematic configuration diagram of an embodiment of the pressure booster plunger type fuel injection device of the present invention, and shows a state in which the injection stroke of the device has been completed. In the present invention, fuel is measured using the reflux pipe 8 and the metering solenoid valve 9 shown in FIG.
However, the fuel oil discharged from the cylinder chamber 7 of the pressure booster plunger 3 is prevented from passing through the switching spool valve 5 by the check valve 17.

For this reason, in the pressure booster plunger type fuel injection device of the present invention, a check valve 17 is provided in the middle of the fuel oil supply pipe 16 that connects the spool valve 5 and the cylinder chamber 7. A discharge port 3a is provided at the top 7a of the cylinder chamber 7.
is a normally closed electromagnetic on-off valve 20 at the fuel oil discharge pipe 18.
It is connected to the fuel tank 2 via a metering solenoid valve.

The electromagnetic on-off valve 20 of this embodiment is provided with a fuel reservoir 24 within its casing 21, and the fuel reservoir 24 is connected to the fuel oil discharge pipe 18 through an inlet 22 and an outlet 23, respectively.

A valve body 25 biased by a spring 28 is inserted into the fuel reservoir 24 from the inlet 22 side to the outlet 22 side.
It is provided so as to seal the 3 side, and the inlet 2
2 to the outlet 23 is blocked.

Furthermore, the electromagnetic on-off valve 20 is provided with the valve body 2 through the casing 21 and from the outlet 23 side.
A push rod 26 is provided which abuts the push rod 5, and a plunger 29 is integrally provided at the end of the push rod 26 outside the casing 21. A solenoid 27 is disposed on the casing 21 so as to surround the push rod 26 and plunger 29. When energized, this solenoid 27 acts to suck the plunger 29 and sink the push rod 26 into the casing 21, and has at least enough suction force to overcome the biasing force of the spring 28. . 30 is solenoid 2
7 and a cover for the plunger 29.

Further, in the pressure booster plunger type fuel injection device of this invention, when the large diameter plunger 6a sliding in the cylinder chamber 7 reaches the bottom dead center, the pressure booster plunger A spill port 3b is provided which opens when the fuel tank 3 completes the injection stroke and communicates with the fuel tank 2.

In the pressure booster plunger type fuel injection system of this embodiment configured as described above, during the injection stroke, the plunger 6 of the pressure booster plunger 3 adjusts the hydraulic pressure of the fuel oil sent from the fuel pump 1 via the spool valve 5. lowers the fuel oil in the fuel chamber 4 to the injection nozzle 12.
When the injection is finished, the spill port 3b provided on the side 7b of the cylinder chamber opens.

Then, the cylinder chamber 7 is opened to the atmosphere, the hydraulic pressure of the fuel oil inside it drops rapidly, and at the end of injection, the spool valve 5 is switched to stop the supply of fuel to the cylinder chamber 7. if,
The hydraulic pressure becomes zero.

When the hydraulic pressure in the cylinder chamber 7 becomes 0, the electromagnetic on-off valve 2 communicates with the cylinder chamber 7 through a fuel oil discharge pipe 18.
The hydraulic pressure in the fuel reservoir 24 at 0 also becomes 0.

From the above, when the injection stroke ends, the plunger 6 of the pressure booster plunger 3 reaches the bottom dead center, and the spool valve 5 switches to enter the metering stroke, the flow of the valve body 25 of the electromagnetic on-off valve 20 The hydraulic pressures on the inlet 22 and outlet 23 sides become 0 and become the same pressure. Therefore, at this point, the solenoid 2 of the electromagnetic on-off valve 20
7 is energized, the solenoid 27 attracts the plunger 29 to immerse the push rod 26 into the casing 21, and the push rod 26 moves the valve body 25 against the spring 28, opening the electromagnetic on-off valve 20. let

Therefore, the solenoid 27 only needs to have suction force sufficient to overcome the biasing force of the spring 28, and the solenoid 27 can be downsized without being made larger than necessary.

When the spool valve 5 is switched in this way and the electromagnetic on-off valve 20 is opened to move from the injection process to the metering process, fuel oil is introduced from the fuel pump 1 through the check valve 15 into the fuel chamber 4 of the pressure booster plunger. be done. This fuel oil causes the plunger 6 to rise and close the spill port 3b, and the fuel oil in the cylinder chamber 7 is discharged from the exhaust port 3a → the exhaust pipe 18 → the inlet 22 of the electromagnetic on-off valve 20 → the fuel reservoir 24 → the outlet 23 → The fuel is returned to the fuel tank via the discharge pipe 18→fuel tank 2 route.

At this time, the fuel oil in the cylinder chamber 7 is removed by the check valve 17.
Due to this function, the fuel oil does not flow back into the fuel oil supply pipe 16, and therefore does not flow into the spool valve 5. Further, since the spill port 3b provided on the side 7b of the cylinder chamber 7 is also blocked by its large diameter portion 6a at the same time as the plunger 6 rises, the leakage is almost negligible, and the fuel in the cylinder chamber 7 is It can be said that the entire amount of oil is returned to the fuel tank 2 without leaking.

Therefore, by adjusting the opening time of the electromagnetic on-off valve 20 (metering electromagnetic valve) (the time during which the solenoid 27 is energized), the amount of fuel oil discharged from the cylinder chamber 7,
That is, the amount of fuel oil introduced into the fuel chamber 4 can be accurately measured.

When the fuel oil in the fuel chamber 4 reaches the required amount, the electromagnetic on-off valve 20 is de-energized, and at the same time the spool valve 5 is energized and switched, thereby transitioning from the metering stroke to the injection stroke.

During the injection stroke, fuel oil from the fuel pump 1 flows into the cylinder chamber 7 via the spool valve 5 → fuel oil supply pipe 16 → check valve 17, and its hydraulic pressure acts on the plunger 6 to increase the pressure inside the fuel chamber 4. Fuel oil is pressurized and injected from the fuel injection nozzle 12.

The hydraulic pressure of the fuel oil in the cylinder chamber 7 during the injection stroke is also applied to the fuel reservoir 24 of the electromagnetic on-off valve 20 through the discharge pipe 18.
Since the fuel oil is returned to the fuel tank 2, no hydraulic pressure is applied to the outlet 23 side of the fuel tank 5. Then,
The valve body 25 is opened to the outlet 2 by the hydraulic pressure in the fuel reservoir 24.
3 is tightly sealed, and there is no leakage of fuel oil from this route.

In this way, in the plunger type fuel injection device of this embodiment, there is no leakage of fuel oil either during metering or injection, so that accurate fuel injection can be performed at all times.

[Effect of idea]

As explained above, the pressure booster plunger type fuel injection device of the present invention provides a check valve in the middle of the fuel oil supply pipe connecting the switching spool valve connected to the fuel pump and the cylinder chamber of the pressure booster plunger. A spill port that communicates the cylinder chamber with the fuel tank when the large diameter plunger of the pressure booster plunger reaches the bottom dead center is provided on the side of the cylinder chamber, and a spill port is provided in the middle of a fuel oil discharge pipe connecting the cylinder chamber and the fuel tank. ,
The large-diameter plunger is characterized in that it is provided with a normally closed electromagnetic on-off valve that is energized and opened when the large-diameter plunger reaches the bottom dead center.

Therefore, at the time of metering, the inflow of fuel from the cylinder chamber is blocked, so there is no leakage of fuel from the switching spool valve, and metering can be performed accurately. Furthermore, since high pressure fuel oil pressure is not applied to the metering solenoid valve during fuel injection, there is no need to use a high-speed, high-pressure solenoid valve.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional pressure booster plunger type fuel injection device, and FIG. 2 is a schematic configuration diagram showing an embodiment of the fuel injection device of the present invention in a state where the injection stroke of the device is completed. . 1...Fuel pump, 2...Fuel tank, 3...
Pressure booster plunger, 3a...Discharge port, 3b...Spill port, 4...Fuel chamber, 5...Spool valve, 6
... Plunger, 7 ... Cylinder chamber, 8 ... Return pipe, 9 ... Metering solenoid valve, 12 ... Fuel injection nozzle, 16 ... Supply pipe, 18 ... Discharge pipe, 20 ...
Electromagnetic on-off valve, 22...inflow port, 23...outflow port,
24... Fuel reservoir, 25... Valve body, 27... Solenoid, 29... Plunger.

Claims (1)

[Scope of utility model registration request] A check valve is provided in the middle of the fuel oil supply pipe connecting the switching spool valve connected to the fuel pump and the cylinder chamber of the pressure booster plunger, and when the large diameter plunger of the pressure booster plunger reaches the bottom dead center, the cylinder chamber A spill port communicating with the fuel tank is provided on the side of the cylinder chamber, and a normally closed spill port is provided in the middle of a fuel oil discharge pipe connecting the cylinder chamber and the fuel tank, and is opened when the large diameter plunger reaches bottom dead center. A pressure booster plunger type fuel injection device equipped with a type electromagnetic on-off valve.