JP2003214279A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device which increases flexibility of the rate of fuel injection, reducing an exhaust gas and improving efficiency. <P>SOLUTION: The fuel injection device is equipped with: a fuel injection valve 7 injecting fuel; a fuel injection pipe 8 introducing the fuel into the fuel injection valve 7; a fuel injection pump 6 feeding the fuel from the fuel tank 1 to the fuel injection pipe 8; fuel return pipes 9, 13 returning fuel from the fuel injection pipe 8 to the fuel tank 1; a solenoid valve 12 intermitting the fuel return pipe 9; and a solenoid valve 16 intermitting the fuel return pipe 13. Fuel flow rate in opening the solenoid valve 12 is set up less than that in opening the solenoid valve 16, and when the fuel is supplied into the fuel injection valve 7, the solenoid valve 12 is precedently closed, the solenoid valve 16 is successively closed, the solenoid valve 12 is opened simultaneously and the solenoid valve 12 is closed subsequently. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for injecting fuel into a combustion chamber from a fuel injection valve of a direct injection diesel engine or the like.

[0002]

2. Description of the Related Art The combustion of a diesel engine is characterized by the history of fuel injection into a combustion chamber, that is, the fuel injection rate. It is desirable to increase the degree of freedom in controlling the injection rate of. However, in an injection device including a cam, a plunger, a fuel injection pipe, and a fuel injection valve (automatic valve), the fuel injection rate is almost determined by the geometrical shape of the cam, and multi-step control is not possible. For this reason, there is a limit to achieving both clean exhaust gas and high efficiency.

As a technique for solving this, for example, a fuel injection valve for injecting fuel, an injection pipe for guiding the fuel to the fuel injection valve, a cam and a plunger for supplying the fuel from the fuel tank to the injection pipe. A fuel injection pump,
A first return pipe for returning fuel from the injection pipe to the fuel tank; a second return pipe for returning fuel from the injection pipe to the fuel tank;
The first valve mechanism (relief valve) for connecting and disconnecting the return pipe of the
A fuel injection device including a second valve mechanism (relief valve) for connecting and disconnecting the return pipe is proposed.

FIG. 10 is a timing chart for explaining how the fuel injection device (comparative example) operates. FIG. 11 is a chart showing changes in the fuel injection rate per intake stroke of the fuel injection device. In this fuel injection device, the intermittent operation of the first and second valve mechanisms can be freely controlled by the control device, the passage areas of the first and second valve mechanisms when opening are different, and the first valve mechanism is different. The passage area of the second valve mechanism is set to be larger than the passage area of. Figure 1
As shown in 0, the plunger first rises with the first and second valve mechanisms opened, the first valve mechanism closes at the time when injection is desired to start, and then the second valve mechanism at an arbitrary time Valve mechanism closes. As a result, as shown in FIG. 11, the fuel injection rate can be controlled in two stages by closing the two valve mechanisms with a time difference, and the initial injection rate of combustion can be reduced.

[0005]

However, in the above-described conventional fuel injection device, the control can be performed only in two stages, and there is a limit to the reduction of exhaust gas and the improvement of efficiency. SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection device capable of increasing the degree of freedom of the fuel injection rate and achieving low exhaust gas and high efficiency.

[0006]

As a means for solving the above problems, a fuel injection device having the following structure is adopted. That is, the present invention according to claim 1 is a fuel injection valve for injecting fuel, an injection pipe for guiding fuel to the fuel injection valve, a fuel delivery means for delivering fuel from a fuel tank to the injection pipe, and the injection. First and second return pipes for returning fuel from the pipes to the fuel tank; a first valve mechanism for connecting and disconnecting the first return pipe; and a second valve mechanism for connecting and disconnecting the second return pipe. In the fuel injection device, the fuel flow rate when the first valve mechanism is opened is set lower than the fuel flow rate when the second valve mechanism is opened. Closing the first valve mechanism in advance, then closing the second valve mechanism at the same time opening the first valve mechanism, and subsequently closing the first valve mechanism. Is characterized by.

In the present invention, since the fuel injection rate can be controlled in three stages, the degree of freedom of the fuel injection rate increases,
It becomes easy to achieve both low exhaust gas and high efficiency. Particularly, in the case of ignitability good fuel early because the NO _X when injecting more fuel increases, realizing a low exhaust gas and high efficiency by controlling the fuel injection rate in three stages can do.

According to a second aspect of the present invention, a fuel injection valve for injecting fuel, an injection pipe for guiding the fuel to the fuel injection valve,
Fuel delivery means for delivering fuel from a fuel tank to the injection pipe, first and second return pipes for returning fuel from the injection pipe to the fuel tank, and first and second connection pipes for connecting and disconnecting the first return pipe A fuel injection device comprising a valve mechanism and a second valve mechanism for connecting and disconnecting the second return pipe, wherein a fuel flow rate when the first valve mechanism is opened is such that the second valve mechanism is opened. Is set to be smaller than the fuel flow rate at the time, and when supplying fuel to the fuel injection valve, the second valve mechanism is closed first,
Subsequently, the first valve mechanism is closed and at the same time the second valve mechanism is closed.
The valve mechanism is opened, and then the second valve mechanism is closed.

In the present invention, the degree of freedom of the fuel injection rate is increased by controlling the fuel injection rate in three stages, such as when the fuel is poorly ignited or when the engine is started at a low temperature, the exhaust gas is reduced and the efficiency is improved. And can be realized.

According to a third aspect of the present invention, when the fuel supply to the fuel injection valve is terminated, a time difference is provided to provide the first
And, the second valve mechanism is intermittently connected.

According to the present invention, when the injection is finished, the fuel injection rate is controlled in three stages to gradually reduce the pressure in the injection pipe, suppress cavitation in the injection pipe, and prevent corrosion of the pipe. .

The present invention according to claim 4 is characterized in that the fuel delivery means comprises a fuel injection pump for sucking and pressurizing the fuel and supplying the fuel to the injection pipe.

The present invention according to claim 5 is characterized in that the fuel delivery means comprises a pressure accumulator for storing the pressure-boosted fuel.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment of Fuel Injection Device According to the Present Invention
The embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing a schematic configuration of a fuel injection device. FIG. 2 is a timing chart for explaining how the fuel injection device operates. FIG. 3 is a chart showing changes in the fuel injection rate per intake stroke of the fuel injection device. In the figure,
Reference numeral 1 is a fuel tank, 2 is a fuel supply pump (fuel supply means), 3 is a relief valve, 4 is a check valve, 5 is a fuel supply pipe,
6 is a fuel injection pump (fuel delivery means), 7 is a fuel injection valve, 8 is a fuel injection pipe, 9 is a fuel return pipe (first return pipe), 10 is a check valve, 11 is a throttle, and 12 is a solenoid valve. (First
Valve mechanism), 13 is a fuel return pipe (second return pipe), 14
Is a check valve, 15 is a throttle, 16 is a solenoid valve (second valve mechanism)
Is.

The relief valve 3 releases the pressure when the fuel supply pump 2 which is constantly operating supplies the fuel at a pressure higher than a predetermined pressure, and returns the fuel from the fuel supply pipe 5 to the fuel tank 1. The check valve 4 is the plunger 6 of the fuel injection pump 6.
The fuel supply pipe 5 is shut off when b is raised (discharge operation).

The fuel injection pump 6 is a pump that sucks and pressurizes the fuel from the fuel tank 1 and sends it to the fuel injection pipe 8 to supply it. The fuel injection pump 6 includes a plunger chamber 6a connected to the fuel tank 1 through a fuel supply pipe 5, and a cam C that works with a crankshaft of a diesel engine (not shown).
And a plunger 6b which reciprocates up and down in contact with and pressurizes the fuel in the plunger chamber 6a.

Further, the cam C is provided with a profile for lowering the plunger 3b at a constant speed during a certain period in the process of lowering the plunger 3b.
As a result, the intake amount of the fuel injection pump 3 per unit time during this period is constant.

The fuel injection valve 7 is a device for injecting fuel into a combustion chamber (not shown), and the fuel injection pipe 8 is a fuel injection valve 7.
It is a conduit that guides fuel to. The fuel return pipes 9 and 13 are lines for returning fuel from the fuel injection pipe 8 to the fuel tank 1, and the check valves 10 and 14 are the fuel return pipes 9 and 14 when the plunger 6b of the fuel injection pump 6 is lowered (suction operation). Shut off 13. The passage area of the diaphragm 11 is set smaller than the passage area of the diaphragm 15.

The solenoid valve 12 is a valve mechanism for connecting and disconnecting the fuel return pipe 9, and the solenoid valve 16 is a valve mechanism for connecting and disconnecting the fuel return pipe 13. The solenoid valves 12 and 16 are of a normal open type that is normally opened and closed by energization. The solenoid valves 12 and 16 have different fuel flow rates when opened due to the functions of the throttles 11 and 15, and the fuel flow rate when the solenoid valve 12 is opened is smaller than the fuel flow rate when the solenoid valve 16 is opened.
The operation of the solenoid valves 12 and 16 is controlled by the control device 17.

The manner of operation of each part of the fuel injection device having the above-described structure is divided into an intake stroke and a discharge stroke, and FIG.
Will be described together with the timing chart of FIG. [A. Intake stroke] Initially, the solenoid valves 12 and 16 are opened, and the fuel in the fuel tank 1 is supplied to the plunger chamber in the fuel injection pump 6 via the fuel supply pipe 5 by the downward movement of the fuel supply pump 2 and the plunger 6b. 6a is inhaled.

[B. Discharge stroke] When the fuel in the plunger chamber 6a is pressurized by the upward movement of the plunger 6b, the internal pressure of the plunger chamber 6a increases, and the pressurized fuel is discharged from the plunger chamber 6a and injected into the fuel injection pipe 8.
At this time, since the solenoid valves 12 and 16 are open, a part of the fuel injected into the fuel injection pipe 8 returns to the fuel tank 1 through the fuel return pipes 9 and 13, and the remaining fuel remains in the fuel injection pipe 8.
Is supplied to the fuel injection valve 7 via.

When the solenoid valve 12 is closed at time T1 when the plunger 6b is rising, the fuel tank 1 is supplied through the fuel return pipe 9.
The amount of fuel supplied to the fuel injection valve 7 through the fuel injection pipe 8 increases by the amount of the fuel that returns to the.

When the plunger 6b further rises and the solenoid valve 12 is opened at the same time as the solenoid valve 12 is opened at a time T2 after an arbitrary time from the time T1, the fuel tank 1 is supplied to the fuel tank 1 via the fuel return pipe 13. The fuel supplied to the fuel injection valve 7 via the fuel injection pipe 8 increases by the amount of the returning fuel. Here, the fuel flow rate when the solenoid valve 12 is opened is set smaller than the fuel flow rate when the solenoid valve 16 is opened. Therefore, from time T2 to T3, time T1 to
The fuel flow rate returning to the fuel tank 1 becomes smaller than that at T2.
As a result, at times T2 to T3, more fuel than at times T1 to T2 is supplied to the fuel injection valve 7 via the fuel injection pipe 8.

Then, when the plunger 6b further rises and the solenoid valve 12 is closed again at time T3 after an arbitrary time from time T2, the fuel returning to the fuel tank 1 via the fuel return pipes 9 and 13 is released. The fuel supplied to the fuel injection valve 7 via the fuel injection pipe 8 becomes maximum. And
After a lapse of a predetermined time, the solenoid valves 12 and 16 are opened, the plunger 6b is turned downward, and the fuel is pumped from the fuel tank 1 into the plunger chamber 6a by the lowering operation of the fuel supply pump 2 and the plunger 6b.

In the fuel injection device of this embodiment, the fuel injection rate can be controlled in three stages as shown in FIG. 3 by repeating each of the above steps. Therefore, the degree of freedom of the fuel injection rate increases, and it becomes easy to achieve both low exhaust gas and high efficiency. In particular, in the case of fuel with good ignitability, if a large amount of fuel is injected early, the amount of NO _x will increase. Therefore, by controlling the fuel injection rate in three stages, low exhaust gas and high efficiency are realized. be able to.

Next, a second embodiment of the fuel injection device according to the present invention will be described with reference to FIGS. 4 and 5. The second
The embodiment has the same configuration as the fuel injection device of the first embodiment. In the following, the manner of operation of each part in the fuel injection device according to the second embodiment will be described only for the discharge stroke.

When the solenoid valve 16 is closed at time T1 during which the plunger 6b is rising, the amount of fuel returning to the fuel tank 1 via the fuel return pipe 13 is exhausted, and the fuel injection valve 7 is supplied via the fuel injection pipe 8. The fuel supplied is increased.

When the plunger 6b is further raised and the solenoid valve 16 is opened at the same time as the solenoid valve 16 is opened at a time T2 after an arbitrary time from the time T1, the fuel tank 1 is supplied to the fuel tank 1 through the fuel return pipe 9. There is no fuel to return. Here, the fuel flow rate when the solenoid valve 12 is opened is set smaller than the fuel flow rate when the solenoid valve 16 is opened. Therefore, at times T2 to T3, the fuel flow rate returning to the fuel tank 1 becomes larger than at times T1 to T2. As a result, time T2
At to T3, less fuel than at times T1 to T2 is supplied to the fuel injection valve 7 via the fuel injection pipe 8.

Then, when the plunger 6b further rises and the solenoid valve 16 is closed again at time T3 after an arbitrary time from time T2, the fuel returning to the fuel tank 1 via the fuel return pipes 9 and 13 is released. The fuel supplied to the fuel injection valve 7 via the fuel injection pipe 8 becomes maximum. And
After a lapse of a predetermined time, the solenoid valves 12 and 16 are opened, the plunger 6b is turned downward, and the fuel is pumped from the fuel tank 1 into the plunger chamber 6a by the lowering operation of the fuel supply pump 2 and the plunger 6b.

In the fuel injection system of this embodiment, the fuel injection rate can be controlled in three stages as shown in FIG. 5 by repeating each of the above steps. Therefore, the degree of freedom of the fuel injection rate is increased, especially when the fuel is poorly ignited or when the engine is started at a low temperature, and it is possible to realize low exhaust gas and high efficiency.

Next, a third embodiment of the fuel injection device according to the present invention will be described with reference to FIGS. 6 and 7. The third
The embodiment has the same configuration as the fuel injection device of the first embodiment. In the following, the manner of operation of each part in the fuel injection device according to the second embodiment will be described only for the discharge stroke. From time T1 to T4, the same operation method as in the first embodiment is performed, and from time T4 to T5, the solenoid valves 12, 1 are operated.
When 6 is opened, the pattern is the same as the change in the fuel injection rate at times T2 to T3. When the solenoid valve 12 is closed at time T5 and the solenoid valve 12 is opened again at time T6, time T5 to time T6
Then, the pattern is the same as the change in the fuel injection rate at times T1 and T2.

In the fuel injection system of the present embodiment, as shown in FIGS. 6 and 7, the fuel injection rate is set to three stages by intermittently operating the solenoid valves 12 and 16 with a time difference when the injection is finished. Can be controlled. As a result, the pressure in the fuel injection pipe 8 is gradually reduced, so that cavitation in the fuel injection pipe 8 is suppressed and corrosion of the pipe can be prevented.

Next, a fourth embodiment of the fuel injection device according to the present invention will be described with reference to FIG. The components already described in the fuel injection device of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the fourth embodiment, the fuel supply pump 2, the relief valve 3 shown in FIG.
The check valve 4, the fuel supply pipe 5, and the check valves 10 and 11 are omitted. In the fourth embodiment, the solenoid valves 12 and 16 are open during the suction operation, and the fuel in the fuel tank 1 is transferred to the solenoid valve 1 as the plunger 6b descends (suction operation).
Plunger chamber 6 passing through Nos. 2 and 16 and diaphragms 11 and 15
Inhaled into a. Also in the fourth embodiment, the fuel injection rate can be controlled in three stages by controlling the intermittent operation of the solenoid valves 12 and 16.

Next, a fifth embodiment of the fuel injection device according to the present invention will be described with reference to FIG. The components already described in the fuel injection device of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the fifth embodiment, the fuel injection pump 6 shown in FIG. 8 is replaced with a pressure accumulator 18. The fuel accumulator 18 has a fuel supply pump 2
The fuel whose pressure is increased by the action of is always stored, and the fuel stored in this pressure accumulator 18 is injected from the fuel injection valve 7. Also in this fifth embodiment, the solenoid valve 12,
The fuel injection rate can be controlled in three stages by controlling the intermittent operation of 16.

[0035]

As described above, according to the fuel injection device of the first aspect of the present invention, since the fuel injection rate can be controlled in three stages, the degree of freedom of the fuel injection rate increases. It becomes easy to achieve both low exhaust gas and high efficiency. Particularly, in the case of ignitability good fuels, because the NO _X when injecting more fuel increases early, by controlling the fuel injection rate in three stages, and a low exhaust gas and high efficiency Can be realized.

According to the fuel injection device of the second aspect, it is possible to realize low exhaust gas and high efficiency, especially when the fuel is poorly ignited or is started at a low temperature.

According to the third aspect of the fuel injection device, the electromagnetic valves 12, 16 are intermittently operated with a time difference to gradually reduce the pressure in the fuel injection pipe 8 and cause cavitation in the fuel injection pipe 8. Can be suppressed to prevent corrosion of the pipe.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a fuel injection device according to the present invention.

FIG. 2 is a timing chart for explaining a method of operating the first embodiment of the fuel injection device according to the present invention.

FIG. 3 is a chart showing changes in the fuel injection rate per intake stroke of the first embodiment of the fuel injection device according to the present invention.

FIG. 4 is a timing chart for explaining an operating method of the second embodiment of the fuel injection device according to the present invention.

FIG. 5 is a chart showing changes in the fuel injection rate per intake stroke of the second embodiment of the fuel injection device according to the present invention.

FIG. 6 is a timing chart for explaining an operating method of a third embodiment of the fuel injection device according to the present invention.

FIG. 7 is a chart showing changes in the fuel injection rate per intake stroke of the third embodiment of the fuel injection device according to the present invention.

FIG. 8 is a schematic configuration diagram showing a second embodiment of the fuel injection device according to the present invention.

FIG. 9 is a schematic configuration diagram showing a third embodiment of the fuel injection device according to the present invention.

FIG. 10 is a timing chart for explaining how the fuel injection device (comparative example) operates.

FIG. 11 is a chart showing changes in the fuel injection rate per intake stroke of the fuel injection device (comparative example).

[Explanation of symbols]

1 fuel tank 2 Fuel supply pump 3 relief valve 4 Check valve 5 Fuel supply pipe 6 Fuel injection pump (fuel delivery means) 6a Plunger room 6b Plunger 7 Fuel injection valve 8 Fuel injection pipe 9 Fuel return pipe (first return pipe) 13 Fuel return pipe (second return pipe) 10,14 Check valve 11,15 aperture 12 Solenoid valve (first valve mechanism) 16 Solenoid valve (second valve mechanism) 17 Control device (control means) 18 Pressure accumulator (fuel delivery means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 59/36 F02M 59/36 59/46 59/46 Y F term (reference) 3G060 BC04 CA03 FA07 3G066 AA07 AB02 BA25 BA38 CB07U CB09 CC06T 3G301 HA02 JA25 LB11 LC01

Claims (5)

[Claims] 1. A fuel injection valve for injecting fuel, an injection pipe for guiding fuel to the fuel injection valve, fuel delivery means for delivering fuel from a fuel tank to the injection pipe, and the fuel tank for the fuel pipe. First and second return pipes for returning fuel to
A first valve mechanism for connecting and disconnecting the first return pipe;
And a second valve mechanism for connecting and disconnecting the return pipe of the first valve mechanism, wherein the fuel flow rate when the first valve mechanism is opened is smaller than the fuel flow rate when the second valve mechanism is opened. The first valve mechanism is closed prior to the supply of fuel to the fuel injection valve, and subsequently the second valve mechanism is closed and at the same time the first valve mechanism is opened. Subsequently, the fuel injection device characterized in that the first valve mechanism is closed. 2. A fuel injection valve for injecting fuel, an injection pipe for guiding the fuel to the fuel injection valve, fuel delivery means for delivering fuel from a fuel tank to the injection pipe, and the fuel pipe for the fuel tank. First and second return pipes for returning fuel to
A first valve mechanism for connecting and disconnecting the first return pipe;
And a second valve mechanism for connecting and disconnecting the return pipe of the first valve mechanism, wherein the fuel flow rate when the first valve mechanism is opened is smaller than the fuel flow rate when the second valve mechanism is opened. The second valve mechanism is closed prior to the supply of fuel to the fuel injection valve, and then the first valve mechanism is closed and the second valve mechanism is opened simultaneously. Subsequently, the fuel injection device, characterized in that the second valve mechanism is closed. 3. The fuel injection according to claim 1, wherein when the fuel supply to the fuel injection valve is terminated, a time difference is provided to connect and disconnect the first and second valve mechanisms. apparatus. 4. The fuel injection device according to claim 1, wherein the fuel delivery means includes a fuel injection pump that sucks and pressurizes the fuel and supplies the fuel to the injection pipe. 5. The fuel injection device according to claim 1, wherein the fuel delivery means includes a pressure accumulator that stores the fuel whose pressure has been increased.