JPH09105368A - Fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a prestroke type fuel injection system that is able to obviate the occurrences of a noise and an injurious ingredient in exhaust gas in time of combustion according to a loaded state, whereas it is compact in size and lighter in weight. SOLUTION: This fuel injection system is provided with a sleeve 3 made up of dividing a part of a plunger barrel 2, and a plunger 1 inserted into this sleeve 3, and this plunger 1 has an axial groove part extending the axial direction, a pilot injection lead 1B extending in the circumferential direction from the lower end, and a main injection fuel metering plunger lead 1A. Likewise, the sleeve 3 has a first fuel spill port 3A connectible to the main injection fuel metering plunger lead 1A, and a second fuel spill port 3B being situated in the lower side of the first fuel spill port 3A connectible to the pilot injection lead 1B, respectively.

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, and more particularly, to a fuel injection device which pumps fuel by a plunger and a sleeve in which the plunger is fitted in a column fuel injection pump of a diesel engine.

[0002]

2. Description of the Related Art In a row type fuel injection pump used in a diesel engine, as a fuel pumping structure, a spill port (fuel escape hole) formed in a plunger barrel of a cylinder constituting a pump element There is a structure in which the period until the inclined plunger leads formed on the plunger sliding in the barrel are opposed to each other is set as the fuel pumping period. In the structure, since the plunger is driven by the cam, the fuel injection pressure does not become constant due to the change in engine speed, and it becomes high pressure at high rotation and low pressure at low rotation. Become. Such phenomena affect the refinement of fuel, and increasing the pressure of fuel injection during high-speed rotation increases the amount of air introduced into the fuel spray, increasing the average excess air ratio of the spray. Although good results can be obtained for promoting the formation of a good air-fuel mixture, on the other hand, good results cannot be obtained at low rotation speed when the injection pressure is low.

Therefore, if the fuel injection pressure in the injection pump is increased in accordance with the oil feed rate at the low rotation speed for the purpose of increasing the oil feed rate of the injection pump at the low rotation speed, it is excessive at the high rotation speed. However, there is a problem in that the above-mentioned idea cannot be blindly followed.

In view of such a problem in the fuel injection pressure, as shown in FIG. 7, the pre-stroke is varied by changing the position of a spill port in a plunger barrel facing a plunger lead formed in the plunger. Has been proposed by the present inventors. FIG.
Is a perspective view showing a main part of the structure, in which a plunger 1 having a plunger lead 1A on its peripheral surface is shown.
A part of the plunger barrel 2 into which is fitted is divided to form a control sleeve 3 so that it can slide on the plunger 1.

A spill port 3A penetrating in the radial direction is formed in the control sleeve 3, and a rotatable control rod 4 having a pin 4A on a peripheral surface engaging with a part of the peripheral surface of the sleeve 3 is rotatable. Solenoid 5
The position of the spill port 3A with respect to the plunger sleeve 3 of the plunger 1 in the stroke up to the end of the fuel pumping shown in FIG.
Is changed in the axial direction to change the pre-stroke until the pressure feeding start time.

In such a structure, as shown in FIG. 9, the plunger speed is increased by increasing the pre-stroke at low rotation to increase the oil feed rate, and at high rotation, the pre-stroke is reduced. By doing so, the conventional oil supply rate is maintained. That is, at the time of high-speed rotation, the timing of the correspondence between the plunger lead 1A and the spill port 3A is advanced to lower the fuel injection pressure and eliminate the adverse effect due to excessive high pressure.

[0007]

However, in a diesel engine equipped with a fuel injection pump having such a structure, since the fuel injection timing is concentrated at one time, ignition delay occurs and noise is generated. May cause.

That is, in the diesel engine, the amount of air supplied to the combustion chamber is constant regardless of the load, and the output according to the load is obtained by the amount of fuel. Therefore, when the load is low and the lean combustion is performed, the temperature in the cylinder is low because the explosion itself in the cylinder is small, and the harmful components such as NOx generated in the exhaust gas are small, but at the time when the fuel is blown to some extent. Then, flame is rapidly generated, ignition delay occurs, and noise is significantly generated. Also, at high load, the temperature in the cylinder rises and the ignition delay is reduced,
NOx generated in exhaust gas due to rise in temperature in the cylinder
The amount of harmful components such as is dramatically increased.

Therefore, when fuel is injected, a technique has been considered in which pilot injection is first performed and then main injection is performed to prevent noise and harmful components in exhaust gas from occurring. There is. However, this technique has a problem in that the pilot injection and the main injection are performed, so that the size of the fuel injection pump is increased and the arrangement space is limited.

Therefore, in view of the problems that are likely to occur even in the above-described prestroke variable fuel injection device, the object of the present invention is to be small and lightweight, and to generate noise and exhaust during combustion depending on the load condition. It is to obtain a fuel injection device capable of preventing the generation of harmful components in gas.

Another object of the present invention is to provide a fuel injection device which is small and lightweight, has good fuel cut-off after the injection is completed, and does not adversely affect the setting of the fuel pumping period.

[0012]

According to a first aspect of the present invention, there is provided a fuel pressure-feeding plunger slidably fitted in a plunger barrel and a space formed by dividing a part of the plunger barrel. A sleeve inserted into the plunger and movable in the axial direction of the plunger, a fuel injection for main injection that is recessed on the circumference of the plunger and extends obliquely with respect to an axial groove portion extending in the axial direction of the plunger. And a first fuel escape hole for main injection which is bored in the sleeve and can face the first lead, and a prestroke with respect to the first lead by relative axial displacement of the sleeve and the plunger. In a fuel injection device that changes the amount, a second lead for pilot injection, which is recessed on the circumference of the plunger and extends in the circumferential direction from the axial groove portion, and A second fuel escape hole which is formed in the sleeve so as to be able to face the second lead and whose height in the vertical direction is equal to or lower than the height in the vertical direction of the second lead. The second fuel escape hole is configured such that the first lead is the first fuel escape hole in a state where the first and second leads are blocked in the sleeve in the moving direction of the plunger during fuel pressure feeding. It is characterized in that it is configured to complete the facing with the second lead before arriving at.

According to a second aspect of the present invention, in the fuel injection device according to the first aspect, a plurality of the second fuel escape holes are arranged in parallel with the second lead.

[0014]

According to the present invention, in a fuel injection device having a structure in which the pre-stroke can be changed, pilot injection is performed using a small amount of fuel before main injection.

Further, according to the present invention, after the pilot injection is performed, the fuel escape amount obtained by the corresponding area of the second fuel escape hole with respect to the second lead is maximized to surely stop the fuel pressure feeding. That is, the axial movement time of the plunger from the end of the pilot injection to the main injection becomes long.

[0016]

1 to 6, an embodiment of the present invention will be described.

FIG. 1 is a model view corresponding to FIG. 9 showing a main part of a fuel injection device according to the present invention, and the same components as those shown in FIG. 9 are designated by the same reference numerals.

In the embodiment shown in FIG. 1, a plunger lead 1A is provided as a first lead which is recessed on the circumference of a plunger 1 for setting the main injection period of fuel and extends obliquely with respect to the axial direction of the plunger 1. In addition to the first fuel escape hole 3A (hereinafter referred to as a spill port) formed in the sleeve 3, the plunger lead 1A and the spill port 3A are opposed to each other earlier than the opposing time when the plunger 1 moves. The pilot injection lead 1B as the two leads is provided on the plunger side, and the pilot injection spill port 3B as the second fuel escape hole is provided on the sleeve side, respectively, and the pilot injection lead 1B and the pilot injection spill are provided before the main injection. A pressure feed period is set for performing pilot injection different from the main injection until the port 3B faces. .

The structure for setting the pressure feeding period for performing the pilot injection described above is composed of the pilot injection spill port 3B and the pilot injection lead 1B provided on the opposite side of the pilot injection spill port 3B. It

The spill port 3B for pilot injection has a plunger 1 as shown in FIG. 2 which is a development view of this portion.
Are located upstream of the main injection spill port 3A in the direction in which the fuel injection pump moves (upward in the figure), and have a different phase on the side opposite to the main injection spill port 3A. The pilot injection spill port 3B is formed of a round hole, and its diameter is set to a size corresponding to the width of the pilot injection lead 1B described later.

On the other hand, the pilot injection lead 1B, as shown in FIG. 1, is a so-called circumferential opening of the fuel escape portion 1a formed in the plunger 1 when the plunger 1 moves for pressure-feeding the fuel, so-called. , The position parallel to the radial direction of the plunger 1 at a position where the fuel pumping period can be set from the time when the lower edge of the suction port 1a1 reaches above the lower end of the sleeve 3 until it reaches the pilot injection spill port 3B. Is formed.

The operation of this embodiment will be described with reference to FIGS. FIG. 4 is a development view of the portion shown in FIG.

3 (A) and 4 (A) show a state in which fuel is not pressure-fed. In this state, only the suction port 1a1 on the plunger 1 side communicates with the fuel chamber, and the fuel pressure-feeding is performed. No pressure is being generated for.

Next, when the plunger 1 starts to rise due to the rotational driving of the cam (not shown) and the pressure bias for the fuel pressure feeding is started, it is shown in FIGS. 3 (B) and 4 (B). As described above, the suction port 1a1 enters the lower end of the sleeve 3 and blocks the escape portion of the pressure, whereby the pressure feeding of the fuel is started. At this point, FIG.
And as shown in FIG. 4C, the pumping pressure is equal to or higher than the valve opening pressure of the injection nozzle (not shown) until the pilot injection spill port 3B and the pilot injection lead 1B in the sleeve 3 face each other. The first stage injection, so-called in FIG. 5, reference numerals (B), (C)
Pilot injection is performed within the range indicated by, and this injection starts ignition in the combustion chamber.

In this pilot injection, as shown in FIGS. 3 (C) and 4 (C), the pressure sharply decreases when the pilot injection spill port 3B and the pilot injection lead 1B face each other. 3D and FIG. 4 when the plunger 1 is further raised after the end.
As shown in (D), pilot injection spill port 3
As shown in FIGS. 3 (E) and 4 (E), the pumping of the main injection fuel is started from the time when the facing relationship between B and the pilot injection lead 1B is released. ),
As shown in (E), the main injection is started when the pressure reaches or exceeds the valve opening pressure of the injection nozzle. This pumping period is shown in FIG.
(F), as shown in FIG. 4 (F), the spill port 3A and the plunger lead 1A start to face each other until the pressure decreases, and when the spill port 3B and the plunger lead 1B face each other, The fuel pressure feeding for injection is completed.

Therefore, in the combustion chamber, ignition of the main injection is continuously started following ignition of the fuel by the pilot injection.

According to this embodiment, even when the prestroke for the main injection is changed, the positional relationship between the spill port for main injection and the spill port for pilot injection is constant, so the prestroke Even when the value is changed, the temporal relationship from the pilot injection to the main injection can be made constant, and even if the prestroke is changed, the continuous ignitability in the combustion chamber is not impaired.

In order to improve the fuel shortage when terminating the pilot injection and to perform the pressurizing action leading to the pressure feeding for the next main injection, the diameter of the pilot injection spill port is set to the pilot injection. It is conceivable to increase the width of the fuel injection lead to discharge the fuel in the pilot injection lead at one time.With such a structure, during the process from the end of pilot injection to the main injection. Therefore, the range occupied by the pilot injection spill port in the mechanical dimension becomes large, and as a result, the pressure feeding period for performing the main injection becomes short.

Therefore, in this embodiment, as shown in FIG. 6, the diameter of the pilot injection spill port 3B on the sleeve 3 side shown in FIG. 1 is larger than the width W of the pilot injection lead 1B on the plunger 1 side. The size is reduced and a plurality of the pilot injection leads 1B on the plunger 1 side are arranged in parallel in the longitudinal direction.

Therefore, according to this structure, almost all the fuel returning from the plunger 1 side into the fuel chamber is secured as the escape passage by the area of the pilot injection spill port 3B. It is possible to prevent the fuel from remaining and improve the fuel shortage.

[0031]

According to the present invention, the first lead is provided on the plunger side, and the second lead for setting the pilot injection pressure feeding period is provided in the lower end portion of the first lead in the circumferential direction. In the second fuel injection hole for the pilot injection described above before the main fuel injection with a phase different from that of the first fuel relief hole.
Since the second fuel relief hole for setting the pilot injection pressure feeding period in cooperation with the reed is provided, the vertical length of the sleeve is shortened, and the size and weight of the device can be reduced and the engine can be mounted. There are no restrictions on placement, it becomes practical,
Since the pilot injection before the main injection can be performed, continuous combustion can be made possible and noise generated by concentrated combustion and generation of harmful components in exhaust gas can be suppressed.

Further, when performing the pilot injection, a structure is provided that allows the discharge of all the combustion when this injection is completed, so that the fuel can be cut off and the pressure feeding period for the main injection can be set reliably. It can be done. Furthermore, the axial movement period of the plunger from the end of the pilot injection to the main injection is shortened, the size and weight of the device can be reduced, and there is no restriction on the placement on the engine.
Be practical.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a fuel injection device showing one embodiment of the present invention.

FIG. 2 is a development view of a main part shown in FIG.

FIG. 3 is a cross-sectional view for explaining an operation of the fuel injection device shown in FIG.

FIG. 4 is a development view of the fuel injection device shown in FIG.

FIG. 5 is a diagram showing characteristics according to a main configuration shown in FIG. 1;

FIG. 6 is a development view of a main part of a fuel injection device showing a modification of the embodiment of the present invention.

FIG. 7 is a perspective view of a main part showing an example of a conventional fuel injection device.

8 is a cross-sectional view for explaining the operation of the fuel injection device shown in FIG.

FIG. 9 is a diagram showing characteristics of the fuel injection device shown in FIG. 7;

[Explanation of symbols]

 1 Plunger 1A 1st lead 1B 2nd lead 2 Plunger barrel 3 Sleeve 3A 1st fuel escape hole 3B 2nd fuel escape hole

Claims (2)

[Claims] 1. A plunger for pressure-feeding a fuel, which is slidably fitted in a plunger barrel, and is fitted in the plunger in a space formed by dividing a part of the plunger barrel, and an axial direction of the plunger. Movable sleeve, a first lead for fuel metering for main injection, which is recessed on the circumference of the plunger and extends obliquely with respect to an axial groove portion extending in the axial direction of the plunger, and a hole provided in the sleeve. And a first fuel escape hole for main injection capable of facing the first lead, wherein the prestroke amount relative to the first lead is changed by relative axial displacement of the sleeve and the plunger. A second lead for pilot injection that is recessed on the circumference of the sleeve and extends in the circumferential direction from the axial groove portion, and faces the second lead on the sleeve. The second hole which is pierced as much as possible and whose height in the vertical direction is equal to or lower than the height in the vertical direction of the second lead.
A second fuel relief hole, wherein the second fuel relief hole is provided with the first lead and the first lead in a state where the first and second leads are blocked in the sleeve in a moving direction of the plunger during fuel pressure feeding. A fuel injection device, characterized in that it is configured to complete the facing with the second lead before reaching the fuel escape hole. 2. The fuel injection device according to claim 1, wherein a plurality of the second fuel escape holes are arranged in parallel with the second lead.