JP2539668Y2 - Fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fuel injection device for a diesel engine.

[Conventional technology]

5 and 6 show an example of a conventional electronic control injection system of the accumulator control valve type, wherein 01 is a fuel tank, 02 is a high-pressure pump, 03 is an accumulator pipe, 04 is an accumulator, and 05 is a timing. A valve, 06 is a hydraulic drive piston, 07 is a metering valve, 08 is a refueling pump, 09 is a controller, 010 is an injection pipe, and 011 is a fuel valve.

 Next, the operation of the conventional example will be described.

In FIG. 5, oil discharged from a fuel tank 01 through a high-pressure pump 02 (oil stored in a pressure accumulator is a fuel valve 011).
The fluid is not limited to the fuel oil injected from the fuel tank, but may be another fluid such as hydraulic oil. ) Is stored in the accumulator 04. When the timing valve 05 is opened according to an instruction from the controller 09, the oil stored in the pressure accumulator 04 acts on the large-diameter side of the hydraulic drive piston 06, and the piston starts to move.
At this time, fuel oil that has been sent in advance from the oil supply pump 08 and that has been metered in accordance with the valve opening time of the metering valve 07 is supplied to the small diameter side of the hydraulic drive piston 06. Compressed to a high pressure.

The pressure wave of the high-pressure fuel propagates through the injection pipe 010 and reaches the fuel valve 011, and the pressure in an oil reservoir (not shown) in the fuel valve also becomes high. When the pressure in the oil reservoir reaches or exceeds a preset valve opening pressure of the fuel valve 011, fuel oil is injected from the fuel valve 011 into a combustion chamber (not shown) of the engine.

The features of this conventional injection system are as follows: (1) The injection timing is defined by the opening timing of the timing valve 05, and the opening timing can be freely set by the controller 09.

(2) The fuel injection amount is defined by the valve opening period of the metering valve 07, and the valve opening period can be freely set by the controller 09.

(3) The injection pressure is basically defined by the pressure of the accumulator 04 and the ratio of the large diameter area to the small diameter area of the hydraulic drive piston 06,
In practice, the injection pressure can be freely set by controlling the pressure of the accumulator, and high-pressure injection is possible.

[Problems to be solved by the invention]

To improve the performance of the engine, it is necessary to increase the fuel injection pressure and shorten the injection period. To achieve this, in the above-described injection system of the pressure-accumulation control valve system, if the injection port area of the fuel valve is increased and the pressure of the accumulator is increased, the high-pressure high injection rate and the rectangular injection as the characteristics of the injection system are considered. Since the mode is set, injection with a high average injection pressure can be realized.

FIG. 6 schematically shows the fuel injection pressure in this case. As a result, although the engine performance is improved, the high-pressure injection increases the fuel amount during the ignition delay period to generate diesel knock, so that the combustion is not performed smoothly and the noise increases. In particular, when a low cetane number fuel is used, the above-mentioned problem occurs remarkably.

An object of the present invention is to solve the problems of the conventional device, inject fuel at a high pressure and a high injection rate, and realize a high-performance and low-noise fuel with less diesel knock even when using a low cetane number fuel. It is to provide a fuel injection device.

[Means for solving the problem]

The fuel injection device of the present invention stores fuel oil pumped by a high-pressure pump in a pressure accumulator, and controls a timing of fuel injection in a fuel injection line between the pressure accumulator and the fuel valve. In a fuel injection device having a hydraulically driven piston that increases the pressure of metered fuel oil and sends it to the fuel valve by the pressure of the operating oil that has passed through the timing valve,
A fuel oil branch passage that bypasses the hydraulic drive piston from the pressure accumulator outlet and reaches the fuel valve via a check valve, and a normally closed electromagnetic that is provided in series in the branch passage and opens and closes the branch passage A valve and a normally open solenoid valve, and a controller that controls the opening of both solenoid valves to control the injection of fuel oil from the fuel valve through the branch passage.

[Action]

The operations of the two solenoid valves are controlled by a controller.
That is, (I) the injection start timing of the pilot injection can be set by the operation start timing of the normally closed solenoid valve.

(II) The pilot fuel injection amount can be set by the time from when the normally closed solenoid valve starts operating until when the normally open solenoid valve starts operating. In this case, since the pressure and the passage area are fixed, the injection amount is determined only by the valve opening time.

In the present invention, the pilot injection is not controlled by one solenoid valve, but is provided with two solenoid valves because the injection period is extremely short and it is difficult to regulate the opening and closing by one solenoid valve. That's why.

Next, the valve opening pressure and the injection pressure during the main injection and the pilot injection will be described.

The valve opening pressure of the fuel valve 11 is a pressure that determines the opening of the fuel valve, which is an automatic valve, and is a pressure value different from the fuel injection pressure. The valve opening pressure is generally a pressure as low as the pressure value in the accumulator. If this value is high, reliable injection at a low load where a small amount of injection is required becomes impossible.

Normally, the opening area of the nozzle of the fuel injection valve is reduced to about 1/10 of the cross-sectional area of the injection pipe 10, so at high load with a large injection amount, according to the pressure generated by the hydraulic drive piston,
After the valve is opened, the injection pressure rises above the valve opening pressure.

Therefore, in the present invention, since the valve opening pressure is set to a pressure that can reliably inject a small injection amount even at a low load, pilot fuel injection can also be reliably performed. Also,
Normally closed solenoid valve after completion of pilot fuel injection
Since the valve 12 is closed, the fuel valve 11 is in the closed state, and the check valve 17 is operating, a normal hydraulic path without the solenoid valves 12, 13 and the injection pipes 14, 15 is formed. As described above, since the valve opening pressure is about the pressure in the pressure accumulator, the main injection after the pilot injection can realize a high injection rate at a high pressure.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

1 to 3 are system diagrams of the first embodiment, showing a case where the oil of the pilot fuel injection system and the oil of the main injection system are the same.

In FIG. 1, 1 is a fuel tank, 2 is a high-pressure pump,
3 is an accumulator pipe, 4 is an accumulator, 5 is a timing valve, 6
Is a hydraulic drive piston, 7 is a metering valve, 8 is a refueling pump, 9 is a controller, 10 is an injection pipe, and 11 is a fuel valve, and their configurations are the same as those of the conventional one.

Reference numeral 14 denotes a branch passage branched from the fuel line 31 between the outlet of the pressure accumulator 4 and the inlet of the timing valve 5, and reference numerals 12 and 13 denote the branch passages.
A normally closed solenoid valve and a normally open solenoid valve arranged in series in 14, a pilot pipe 15 for connecting the fuel outlet of the normally open solenoid valve 13 and the injection pipe 10, and 17 a pipe 15 It is a check valve interposed inside. The control signals from the controller 9 are input to the two solenoid valves 12 and 13 so that the two solenoid valves 12 and 13 are opened and closed.

 Next, the operation of the above embodiment will be described.

 First, the operation of the main injection system will be described.

Oil (fuel oil) pumped from the fuel tank 1 by the high-pressure pump 2 is stored in the accumulator 4 at a high pressure. When the timing valve 5 opens according to an instruction from the controller 9, the accumulated oil acts on the large-diameter side of the hydraulic drive piston 6, and the piston 6 starts to move. At this time, fuel oil which is supplied in advance from a refueling pump 8 and metered by a metering valve 7 controlled by a controller 9 is supplied to the small diameter side of the hydraulic drive piston 6. The pressure wave of the pressurized fuel is compressed by the movement of the drive piston 6 and reaches the fuel valve 11 via the injection pump 10 to be a pressure in an oil reservoir (not shown) in the fuel valve 11.
When the pressure in the oil reservoir rises and becomes equal to or higher than a valve opening pressure set in advance to about the pressure of the accumulator 4 so that a small injection amount can be reliably injected, the fuel valve 11 opens. Fuel valve 11
Is usually reduced to about 1/10 of the cross-sectional area of the injection pipe 10, so that the injection pressure of the fuel valve 11 is reduced according to the pressure generated by the hydraulic drive piston 6. The pressure becomes much higher than the valve opening pressure, and fuel oil is injected from the fuel valve 11 into a fuel chamber (not shown). In the above-mentioned injection system, the injection timing is freely set via the controller 9 by the timing valve 5 and the fuel injection amount is set by the metering valve 7. Further, the injection pressure is controlled by the hydraulic drive piston 6.
Can be freely set by controlling the ratio between the large-diameter side area and the small-diameter side area and the pressure in the pressure accumulator 4, thereby enabling high-pressure injection.

Next, the pilot injection system which is a main part of the present invention will be described.

The oil discharged from the high-pressure pump 2 is stored in the pressure accumulator 4. Before the timing valve 5 is opened by the instruction of the controller 9 and the main fuel injection is started, the normally closed solenoid valve 12 is energized by the instruction of the controller 9 as shown in FIG. The valve is opened. Next, since the other solenoid valve 13 arranged in series is of a normally open type and is opened when power is not supplied, the fuel oil stored in the pressure accumulator 4 flows from the branch passage 14 to the pilot injection pipe 15 through the branch passage 14. And further pushes up check valve 17 to inject the injection pipe
The fuel valve 11 passes through 10. When the pressure of the fuel oil becomes equal to or higher than the valve opening pressure of the fuel valve, the fuel oil is injected into the combustion chamber. However, at this time, the pressure of the accumulator 4 needs to be higher than the valve opening pressure of the fuel valve.

In this way, the pilot injection starts when the normally closed solenoid valve 12 is energized. Thereafter, when the normally open solenoid valve 13 is energized by an instruction from the controller 9, the solenoid valve 13 closes. Therefore, the flow of the oil stored in the pressure accumulator 4 to the fuel valve 11 is interrupted, and the pilot fuel injection ends.

After that, when a specific time elapses, the timing valve 5 opens according to an instruction from the controller 9, and main injection is started.

In the main injection after the pilot injection, the normally closed solenoid valve 12 is closed, the fuel valve 11 is closed, and the check valve 17 is further moved from the injection pipe 10 side to the pilot injection pipe 15 side. Is stopped, a fuel oil path without a bypass line from the branch passage 14 to the junction with the injection pipe 10 via the solenoid valves 12 and 13 is formed. Can be realized.

Thus, the main injection after the pilot fuel injection can realize a high pressure and a high injection rate.

FIG. 2 shows a normally closed solenoid valve 12, a normally open solenoid valve 13, and a timing valve 5 by the controller 9.
5 shows a pattern of a drive signal of the metering valve 7.
FIG. 3 schematically shows the injection pressures of the pilot injection and the main injection at this time.

In this case, the interval between the pilot injection and the main injection is appropriately adjusted via a controller according to the ignitability of the fuel, the rotation speed of the engine, and the like. A design that can achieve the injection characteristics required for combustion can be realized. That is, diesel knock is reduced by a small amount of pilot injection, and high-performance injection can be realized by setting the main injection to a high pressure and a short injection period.

The reason why the pilot injection is not controlled by one solenoid valve but two solenoid valves are provided in the present invention is as follows.

That is, when a pilot injection of a high-speed diesel engine is considered, assuming that the period of the pilot injection at the engine speed N _R = 2000 rpm is θ _fp = 5 ° crank angle, this time is a very short time such as about 0.42 msec. This is because it is difficult to specify the opening and closing of one solenoid valve.

The arrangement order of the normally closed solenoid valve 12 and the normally open solenoid valve 13 used for pilot injection is as follows.
It does not matter which one is first, and it is sufficient that they are connected in series.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, the pilot injection system uses a high cetane number fuel such as light oil, and the main injection system is a separate system so as to use an economical low cetane number fuel. Its operation is the same as that of the first embodiment, but requires two oil tanks. 4 is different from the embodiment of FIG. 1 in that a high cetane number fuel oil tank 1 and a low cetane number fuel oil tank 18 are provided in FIG. However, diesel knock can be reduced more reliably.

[Effect of the invention]

The fuel injection device of the present invention uses a pilot injection of a small amount of fuel as an ignition source for main injection even in the case of using low cetane number fuel with poor ignitability in an electronically controlled injection system of the accumulator control valve system. In addition, diesel knock can be prevented, smooth combustion can be realized, and main injection can be performed at a high pressure and high injection rate, so that a high-performance and low-noise diesel engine can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 relate to the present invention, FIG. 1 is a block diagram of an injection system, FIG. 2 is a signal diagram of a controller, FIG. 4 is a diagram corresponding to FIG. 1 of the second embodiment, FIGS. 5 and 6 are conventional examples, FIG. 5 is a diagram corresponding to FIG. 1, and FIG. 6 is a diagram corresponding to FIG. 1 ... fuel tank, 2 ... high pressure pump, 4 ... accumulator,
5 ... Timing valve, 6 ... Hydraulic drive piston, 7 ...
Metering valve, 9 ... Controller, 11 ... Fuel valve,
12 Normally closed solenoid valve, 13 Normally open solenoid valve, 14 Branch passage.

Claims (1)

(57) [Scope of request for utility model registration] A fuel valve pumped by a high-pressure pump is stored in an accumulator, and a timing valve for controlling fuel injection timing in a fuel injection pipe between the accumulator and the fuel valve is provided. In a fuel injection device having a hydraulically driven piston that increases the pressure of metered fuel oil and sends it to a fuel valve by the pressure of operating oil that has passed, the hydraulically driven piston is bypassed from the pressure accumulator outlet, and a check valve is provided. A normally closed solenoid valve and a normally open solenoid valve which are provided in series in the branch passage to open and close the branch passage, and the degree of opening of the two solenoid valves. And a controller for controlling the injection of the fuel oil from the fuel valve through the branch passage by adjusting the pressure.