JPH027256Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pressure booster plunger type fuel injection device, and particularly to an improved metering device for this device.

A conventional pressure booster plunger type fuel injection device operates a servo piston using a servo valve, drives a plunger pump connected to this piston by a connecting rod at high speed, and injects fuel into the fuel injection nozzle depending on the amount of movement of the plunger. The system is configured to control the amount of fuel supplied to the fuel tank.

After all, in the fuel injection device, the amount of fuel supplied to the fuel injection nozzle is measured by the amount of movement of the servo piston, that is, the amount of movement of the plunger during fuel injection, so the amount of movement of the servo piston cannot be accurately measured. I needed control.

Specifically, when the servo piston moves, the fluid pushed out by the piston acts on the metering piston, and the movement of the piston is stopped when the metering piston hits a stopper. be. In other words, this type of fuel injection device controls the amount of fuel injected by controlling the movement of a servo piston during fuel injection.

However, this type of fuel injection device has the disadvantage that the amount of fuel injected is different from the amount of movement of the metering piston.

Specifically, since there is resistance in the pipe connecting the servo piston and the metering piston, the pressure inside the metering tube increases momentarily, and the increased pressure causes the metering piston to actuate. A leak-off valve for controlling the amount of fuel to be injected in conjunction with the metering piston opens to relieve the pressure in the metering pipe and reduce the pressure in the high-pressure fuel transport pipe connecting the plunger pump and the fuel injection nozzle. A phenomenon occurred in which the fuel injection stopped when the engine was pulled out. This phenomenon makes the amount of fuel supplied to the injection nozzle inaccurate,
Normally, it operates in such a way that the amount of fuel decreases as the engine speed increases.

Considering the above phenomenon in more detail, the time during which fuel is injected into the cylinder is 1/1000 to 3/1000.
Since the time is about seconds, the pressure rises in the pipe before the liquid discharged from the servo piston sufficiently flows to the metering piston side, resulting in the disadvantage of malfunctioning as described above.

On the other hand, considering the time required to suck the fuel into the plunger pump, the time required to suck the fuel into the plunger pump is 30/1000 to 40/1000 seconds based on the rotation angle of the crank. The time required to draw fuel into the plunger pump is much longer than the time required to supply fuel to the fuel injection nozzle.

In other words, in the metering system of conventional pressure booster plunger fuel injection devices, the metering piston must act instantaneously to stop the servo piston, but the metering piston and servo piston must be connected before the piston operates. The pressure rises rapidly due to the resistance of the pipe connecting the piping, and before the metering piston can be stopped by the stopper, the leak-off valve to release pressure from the plunger pump is activated, and the amount of fuel injected is not accurate. It was difficult to measure the

When supplying fuel to a plunger pump, devices for measuring the fuel to be injected in the next stroke have been proposed, for example, in Japanese Unexamined Patent Publication No. 55-49571 and Japanese Utility Model Application No. 58-12671.

These have a metering section connected to a pipe that connects the fuel injection nozzle and a plunger driven by a servo piston. The amount of fuel supplied into the plunger chamber is measured by this solenoid valve.

By the way, solenoid valves have large measurement errors unless the opening and closing times are determined accurately. On the other hand, the electrical resistance of a solenoid valve changes greatly depending on the temperature of the coil, and the current flowing through the coil changes accordingly.As a result, the attraction force of the coil changes, and the valve opening period changes accordingly. Change.

That is, when the temperature is low, the resistance of the coil is small and a large current flows, so that the current required to open the plunger of the solenoid valve is quickly reached. However, when the temperature is high, the resistance of the coil is large and the current decreases overall, so it takes a long time to reach the current.
Therefore, even if the coil of the solenoid valve is energized for the same amount of time, the actual opening period of the plunger of the solenoid valve will vary depending on the temperature, and will vary by about 10% at most. There is a drawback that measurement errors occur.

As mentioned above, solenoid valves are greatly affected by temperature, so in order to take this into account and perform accurate fuel injection,
A circuit that detects the temperature of the coil and finely controls the energization time is required, and extremely complicated additional functions are required. Further, there is a problem in that there are variations in temperature between each cylinder of the engine, and correction thereof is required in order to produce accurate output between each cylinder.

The object of the present invention is to overcome the drawbacks of devices that directly measure the amount of fuel supplied to a plunger using a solenoid valve, such as the pressure booster plunger type fuel injection device.

The configuration of the present invention to achieve the above object includes: a servo piston that drives a plunger that supplies fuel to a fuel injection nozzle; a servo valve that opens and closes a high-pressure fuel circuit that is supplied to the servo piston; It consists of a metering piston connected via a servo valve, and the metering piston is pressed at the back by a return spring and is locked by a stopper whose stop position is adjusted according to the output of the engine. This is a metering device in a pressure booster plunger type fuel injection device configured as follows.

In other words, in the process of the servo piston moving to suck fuel into the plunger pump, the moving position of the servo piston is controlled by the metering piston fluidly interlocked with the movement of the piston.

Therefore, the amount of suction into the plunger pump is controlled by the retraction distance of the servo piston.
Compared to a device that operates a solenoid valve to control the delicate amount of fuel supplied to the plunger pump, the intake amount of fuel is much more accurate.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the main parts of a pressure booster plunger type fuel injection device according to the present invention.

In the figure, 1 is a servo piston, and a piston 3 housed in a cylinder 2 operates a plunger 5 of a plunger pump 4 to pressurize fuel in a cylinder 6 and supply it to a fuel injection nozzle 7. Inject into cylinders not shown.

A servo valve 8 is connected to the servo piston 1, and the servo valve 8 is configured to be controlled by a four-way solenoid valve 9. Further, a metering piston 10 is connected to the servo valve 8.

The servo valve 8 has three consecutive pistons 8b, 8c, and 8d housed in a cylinder 8a, and these pistons are pressed to the right in the figure by a spring 8e.

The four-way solenoid valve 9 has a valve body 9 pressed by a spring 9a.
b, and the fuel tank 1 is opened by this valve body 9b.
1. The pump 12 is configured to switch the pipe line between the reflux pipe 13 and the cylinder 8a of the servo valve 8.

The cylinder 6 of the plunger pump 4 is connected via a check valve 14 to a pipe 16 connecting a high pressure pump 15 and a servo valve 8. Also, this servo valve 8
A communication port 8g provided in the cylinder 8a and the fuel tank 11 are connected by a reflux pipe 20.

The metering piston 10 is composed of a cylinder 10a, a piston 10b, a stopper 10c, and a spring 10d. The piston 10b moves to the right by the pressure in the pipe 21 connecting the servo valve 8 and the metering piston 10, and comes into contact with the stopper 10c. When the pressure in the cylinder 10a drops, the spring 10d moves to the left and returns to the original position.

The stopper 10c is a member that changes its stop position according to the output of the engine, and is driven by, for example, an Arcel pedal or the like.

The metering device in the pressure booster plunger type fuel injection device according to the present invention has an important significance in that the metering of fuel starts from the movement start point of the servo piston.

In other words, it is unique in that it is configured to accurately measure the amount of fuel using a long stroke in which fuel is sucked into the plunger, rather than a short fuel injection stroke.

Next, details of the operation of the device according to the present invention will be explained.

(1) Measuring fuel Measuring start position, that is, plunger pump 4
In the initial position when fuel is drawn into the engine, the plunger 5 of the plunger pump 4 and the piston 3 of the servo piston 1 that drives the plunger 5 are at the lowest position as shown in FIG.

The series of pistons of the servo valve 8 are pushed by the spring 8e and are moving to the right end side as shown in FIGS. 1 and 2. On the other hand, the high pressure pump 15 that supplies fuel into the plunger pump 4 and the cylinder 8a of the servo valve 8
A pipe 16 connecting the pistons 8b and 8c is closed by the piston 8b, and a pipe 21 connecting the cylinder 2 of the servo piston 1 and the metering piston 10 is communicated with the pistons 8b and 8c through a gap. Therefore, when the piston 3 rises, the metering piston 10 is ready to operate due to the pressure in the tube 21.

The fuel in the fuel tank 11 is pressurized by the high-pressure pump 15 and supplied to the plunger pump 4 via the check valve 14, causing the plunger 5 to move in the direction of arrow B.
raise it like this. Then, the fuel filled in the upper part of the piston 3 is transferred to the piston 8b of the servo valve 8.
and 8c, and is supplied into the metering piston 10 via the pipe 21 and moves the piston 10b along the arrow C.
Move it to the right against the spring 10d as shown.

As described above, when the piston 10b moves to the right against the spring 10d, it comes into contact with the stopper 10c and stops. When the piston 10b stops in this way, the pressure in the tube 21 increases momentarily, and the force acting on the end face of the plunger 5 and the force acting on the piston 3 are finally balanced, and the piston 3 and the plunger 5 Stop.

This state is the completion of metering, and the piston 3 rises from the lowest position until the piston 10b of the metering piston 10 is stopped by the stopper 10c, and the next injection is made into the cylinder 6 of the plunger pump 4. It inhales the required amount of fuel.

As described above, the time required for the plunger pump 4 to suck fuel into the cylinder 6 is much longer than the time required for fuel injection.

Therefore, the servo piston 1 and the metering piston 10
Since the fuel is measured with almost no resistance in the pipe 21 connecting the
0 does not operate sufficiently, the supply of fuel to the plunger pump 4 will not be stopped, and an accurate amount of fuel will be supplied to the metering pump 10.

(2) Fuel injection stroke Next, when the solenoid valve 9 is energized and the valve body 9b moves in the direction of arrow A (downward) in FIG. The piston 8d is supplied into the cylinder 8a as shown by arrow D, and moves the piston 8d to the left against the spring 8e.

FIG. 3 shows a state in which this operation has been completed, in which the piston 8d moves to the left against the spring 8b and the high pressure pump 15 discharges through the gap between the pistons 8b and 8c. fuel pipe 16
is supplied into the cylinder 2 through the piston 3 to lower the piston 3.

The piston 3 and plunger 5 are continuous, and the plunger 5 momentarily supplies high-pressure fuel in the cylinder 6 to a fuel injection nozzle 7, which injects the fuel into the combustion chamber in the cylinder. do.

In the process of the plunger 5 rising, the plunger 5
The pressure of the pump 15 is acting on the tip surface of the
When injecting fuel as described above, the pressure of the pump 15 acts on the surface of the servo piston 3, so the fuel in the plunger pump 4 is pressurized and injected in proportion to the ratio of the areas of both pistons. That will happen.

This fuel injection continues until the piston 3 of the servo piston 1 moves to the lowest position, which is the starting point of metering, and ends when the piston 3 stops at the lowest position.

On the other hand, since the return pipe 20 and the pipe 21 connected to the metering piston 10 are connected to each other by the gap between the pistons 8c and 8d, the pipe 21, the metering piston 10, and the servo valve 8 are filled. The fuel flows back into the fuel tank 11 via the pipe 22 and the four-way solenoid valve 9 as indicated by arrow E. In this process, the piston 10b of the metering piston 10 is
d and moves to the left in preparation for the next weighing.

(3) Return operation of servo valve As shown in FIG. When moved to the lowest position, the state shown in FIG. 2 is again achieved.

In this state, when the electromagnetic valve 9 is de-energized, the valve body 9b is pushed by the spring 9a and rises in the direction opposite to the arrow A, resulting in the state shown in FIG.

In this state, as shown in FIG.
1. On the other hand, the pipe 16 of the high-pressure pump 15 is closed, and the pipe on the check valve 14 side is opened, so that high-pressure fuel discharged from the high-pressure pump 15 is supplied into the cylinder 6 of the plunger pump 4. As a result, the plunger 5 will rise.

During the rising process of the plunger 5, the piston 3 integrated with the plunger 5 rises, and the pipe 2
1, fuel is supplied into the cylinder 10a of the metering piston 10, and when the piston 10b of this comes into contact with the stopper 10c and the pressure in the pipe 21 increases, the piston 3, that is, the plunger 5 stops rising. This completes the metering of the next fuel to be injected.

As described above, the metering device in the pressure booster plunger type fuel injection device according to the present invention opens and closes the servo piston that drives the plunger that supplies fuel to the fuel injection nozzle, and the high-pressure fuel circuit that is supplied to the servo piston. It consists of a servo valve for the engine and a metering piston connected via the servo valve. It is configured so that it can be locked by twisting it.

That is, the metering device in the pressure booster plunger type fuel injection device according to the present invention does not measure fuel by the operating time of a solenoid valve as in conventional devices, but instead uses a metering piston and a servo piston (plunger). A major feature is that the servo piston is fluidly connected and the movement of the servo piston is determined fluidly and mechanically.This feature completely eliminates the influence of temperature-related variations in fuel metering, that is, the influence of fuel injection amount. There is a major feature in the exclusion.

More specifically, the present invention can achieve the following effects.

Next, the amount of fuel to be injected is determined by raising the plunger 5 or the servo piston 2 from the lowest position and moving the piston 10b of the metering piston 10 to the stopper 10c.
This is done during the stroke of sucking fuel into the plunger pump 4 until it stops, so the time required for this fuel suction stroke is 20 to 40 times longer than the time required for the injection stroke. It is possible to draw fuel into the pump 4 and inject it into the cylinder.

Furthermore, since the fuel pressure from the high-pressure pump 15 is used to meter the fuel supplied to the plunger pump 4, the operation of the metering piston is reliable, and the position where the piston 10b is stopped by the stopper 10c is accurate. Therefore, the amount of fuel injected as described above becomes accurate.

Another effect is that by connecting the metering piston and the servo piston (plunger) with fuel piping, the metering pistons of each cylinder can be gathered in one place with piping, which greatly increases the flexibility in terms of layout. improve.

[Brief explanation of the drawing]

Fig. 1 is a pipe diagram showing the main parts of the fuel injection device according to the present invention, Fig. 2 is a sectional view showing the relationship between the servo piston and the servo valve in the metering state, and Fig. 3 is the servo piston in the injection stroke. It is a figure showing the operating state of a piston etc. 1...Servo piston, 2...Cylinder, 3...
... Piston, 4 ... Plunger pump, 5 ... Plunger, 6 ... Cylinder, 8 ... Servo valve, 9
... Four-way solenoid valve, 10 ... Metering piston, 14 ...
...Check valve, 15...High pressure fuel pump.

Claims (1)

[Scope of utility model registration request] It consists of a servo piston that drives a plunger that supplies fuel to a fuel injection nozzle, a servo valve that opens and closes a high-pressure fuel circuit that is supplied to the servo piston, and a metering piston that is connected via the servo valve. In the pressure booster plunger type fuel injection device, the metering piston is configured such that its back surface is pressed by a return spring and is locked by a stopper whose stopping position is adjusted according to the output of the engine. Weighing device.