JPH062631A - Fuel injection system of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an internal combustion engine fuel injection system that is able to vary a fuel injection characteristic itself according to driving conditions in an engine in a simple structure. CONSTITUTION:A center hole 3 to be interconnected to a fuel pressure-feed chamber 14 and both first and second leads 4 and 5 to be interconnected to this center hole 3 are all installed in a plunger 1 being supported by a plunger barrel 2 and reciprocating in this barrel 2 in the vertical direction, at each of different positions, a suction exhaust oil pump 6 to be interconnected to the first lead and a subport 7 to be interconnected to the second lead are installed in this plunger barrel 2, and with an up of the plunger 1, the second lead and the subport 7 are interconnected to each other, and then the first lead and the suction-discharge oil port 6 are interconnected to each other as well.

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 an internal combustion engine capable of changing fuel injection characteristics.

[0002]

2. Description of the Related Art In general, a diesel engine that performs compression ignition may cause ignition delay when the injected fuel is in a condition in which injected fuel is relatively difficult to ignite in the combustion stroke, which causes combustion in a cylinder. If it is carried out explosively, as a result, there arises a problem that combustion noise such as diesel knock and increase of NOx are caused. As a means for suppressing such a problem, it is known to pilot-inject a small amount of fuel prior to main fuel injection. Conventionally, when such pilot injection is performed by the same fuel injection device, a first lead is provided on the outer peripheral surface of the plunger, and the first lead and the upper end of the plunger are also provided on the outer peripheral surface of the plunger. A second lead is provided between the two. When the fuel is fed under pressure, the first and second leads are communicated with the oil intake / exhaust holes provided in the plunger barrel, so that pilot injection is performed prior to main injection (for example,
See Japanese Utility Model Laid-Open No. 2-78762).

[0003]

However, in the fuel injection device having the above-described structure, the lead shape and the arrangement are set so that the pilot injection and the main injection are always performed at a predetermined interval, so that the engine is Depending on the operating state of
It is not always possible to obtain efficient combustion conditions. For example, in the high load range and high rotation range, when pilot injection and main injection are performed independently, if the timing of the main injection is relatively late, a large amount of injection will cause a large amount of fuel to be sent into the flame. As a result, the mixture with the air becomes insufficient, which easily causes smoke (black smoke). Therefore, it is desired to variously change the fuel injection characteristics according to the operating state. In the case of the one disclosed in the above publication, the injection characteristics can be changed to some extent depending on the shape of the second lead, but since the two leads are sequentially connected to and cut off from one oil drain hole, Since the arrangement of both leads with respect to the oil drain hole and the diameter of the oil drain hole are restricted, the degree of freedom in design is poor, and it is difficult to adjust the injection characteristics in a wide range.

The present invention has been made to solve the above problems, and provides a fuel injection device for an internal combustion engine, which has a simple structure and can change the fuel injection characteristics according to the operating conditions of the engine. It is a thing.

[0005]

The invention according to claim 1 is
A plunger barrel; a first oil drain hole formed in the plunger barrel; a plunger that reciprocates in the plunger barrel to open and close the first oil drain hole; and a plunger formed on the outer peripheral surface of the plunger. The plunger and the first lead which are capable of communicating with the first oil drain hole, and the communication passage which is formed in the plunger and which always connects the first lead and the pressure chamber of the plunger barrel. In a fuel injection device for an internal combustion engine, which is relatively rotatable with respect to a plunger barrel, a second lead communicating with the pressure chamber is formed on an outer peripheral surface of the plunger, and the plunger barrel is provided with the second lead. A second oil drain hole capable of communicating is provided.

According to a second aspect of the present invention, there is provided a plunger barrel, a plunger which reciprocates in the plunger barrel, a timing sleeve fitted to the plunger, and a first oil drain hole formed in the timing sleeve. And a first suction hole formed on the outer peripheral surface of the plunger for communicating fuel with the first suction hole for communicating with the first drain hole.
And a communication passage formed in the plunger, which always communicates the first lead and the fuel suction hole with the pressure chamber of the plunger barrel, and the timing sleeve is movable up and down with respect to the plunger. Yes, again
In a fuel injection device for an internal combustion engine in which the timing sleeve and the plunger are relatively rotatable, a second lead communicating with the pressure chamber is formed on an outer peripheral surface of the plunger, and the timing sleeve has the second lead. A second oil drain hole that can communicate with the second lead is provided.

According to a third aspect of the present invention, in the fuel injection device according to the first or second aspect, the amount of pressure relief from the pressure chamber during the communication period between the second lead and the second oil drain hole. However, it is set so as to decrease as the engine speed increases.

According to a fourth aspect of the present invention, in the fuel injection device according to the first or second aspect, the plunger is rotationally displaced according to the load of the engine, and the second lead is the load increase of the engine. With the rotational displacement of the plunger according to the above, the communication period with the second oil drain hole becomes shorter.

[0009]

According to the first aspect of the present invention, pilot injection is performed as the plunger rises, and the pilot injection ends when the second lead and the second oil drain hole communicate with each other. When the injection is started and the first lead and the first oil drain hole communicate with each other, the main injection ends. Then, by appropriately designing the shapes of the leads and the oil drain holes in advance, the injection characteristics are variously changed according to the rotational displacement of the plunger and the like.

According to the second aspect of the invention, the injection timing of the pilot injection can be changed while the main injection start timing is kept constant.

According to the third aspect of the present invention, the amount of oil escaping from the second reed to the second drain hole is reduced due to the increase in the engine speed, and the pilot injection and the main injection are not independent. , Performed continuously.

According to the fourth aspect of the present invention, the plunger is rotationally displaced according to the load of the engine, and when the load is high, the opening area of the second lead with respect to the second oil drain hole is reduced, and the second lead is discharged. The communication time between the lead and the second oil drain hole is shortened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A series fuel injection system according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a sectional perspective view showing the fuel injection pump.

A cam shaft 8 shown in the lower portion of the fuel injection pump P in FIG. 1 is driven by a gear or a chain from the crank shaft of the engine. The cam shaft 8 is provided with a cam 9 for driving the plunger 1 described later. ing. The plunger 1 is supported in the plunger barrel 2 so as to be movable in the axial direction thereof, and a tappet 10 which is in sliding contact with the cam 9 is provided at the lower end of the plunger 1, and the plunger 1 is attached downward by a spring 11. It is energized. Therefore, the plunger 1 is attached to the camshaft 8
Also, as the cam 9 rotates, it is pushed by the convex portion of the cam 9 and reciprocates vertically in the plunger barrel 2 with a constant stroke.

As shown in FIG. 1, a center hole (communication hole) 3 is formed at the center of the plunger 1, and the center hole 3
Communicate with a fuel pumping chamber (pressure chamber) 14 formed above the plunger barrel 2. A first lead 4 and a second lead 5 communicating with the center hole 3 are formed on the outer peripheral surface of the plunger 1. The first lead 4 is formed with an appropriate lead angle over a certain range in the circumferential direction of the plunger 1, and the second lead 5 is located at a position different from the first lead (for example, on the axis of the plunger 1). It is formed in a shape which will be described in detail later in the circumferential direction at symmetrical positions).

On the other hand, the plunger barrel 2 has the above-mentioned first
Suction / discharge oil port 6 (first oil discharge hole) corresponding to the lead 4 of
And the sub-port 7 (the second port) corresponding to the second lead.
Oil drain hole) is provided. The intake / exhaust oil port 6 is
The diameter is relatively large so that the oil can be quickly drained after the end of fuel injection, while the sub port 7 has a smaller diameter than the intake / exhaust oil port 6.

A control sleeve 12 is fitted around the plunger barrel 2 from the outside, and a pinion gear 13 is fitted on the outer peripheral surface of the control sleeve 12. The pinion gear 13 meshes with the control rack 15, and the horizontal movement of the control rack 15 causes the pinion gear 13, the control sleeve 12, and the plunger 1 to rotate integrally, so that the plunger 1 is relatively moved with respect to the plunger barrel 2. It is rotatable.

Further, a delivery valve 16, a spring 17, a delivery valve holder 18 and the like are provided above the plunger 1, and the delivery valve holder 18 has a fuel delivery port 19 communicating with the fuel pressure delivery chamber 14. It is provided.

Next, the operation of the fuel injection pump P having the above structure will be described.

The injection fuel is pressure-fed by rotating the cam shaft 8 and vertically moving the plunger 1 by the cam 9. First, when the plunger 1 descends and the upper end of the plunger 1 falls below the intake / exhaust oil port 6 of the plunger barrel 2, fuel is sucked into the plunger barrel 2. Then, when the plunger 1 rises from the bottom dead center and the peripheral surface of the upper end portion of the plunger 1 completely closes the oil intake / exhaust oil port 6, the fuel filled in the fuel pumping chamber 14 is shut off from the outside, and the fuel rises as the plunger 1 rises. Outlet 19
Will be pressure-fed to the engine (not shown) through (start of pilot injection).

When the plunger 1 is further raised and the second lead 5 reaches the sub-port 7 of the plunger barrel 2, the two are brought into communication with each other, and the fuel in the fuel pumping chamber 14 has the fuel in the center hole 3 of the plunger 1 and the second lead. 5 and the sub-port 6 are released to the outside, whereby the fuel pressure feeding is interrupted (end of pilot injection).

When the plunger 1 is further raised and the second lead 5 is displaced from the sub port 7, the fuel pressure feeding chamber 14 is shut off from the outside, and the fuel pressure feeding is started again (the main injection is started).

Then, the plunger 1 is further raised,
The first lead 4 is the intake / exhaust oil port 6 of the plunger barrel 2.
And the two communicate with each other, the fuel will be sent back to the intake / exhaust oil port 6 through the center hole 3 of the plunger 1.
The fuel pressure feeding is stopped again (end of main injection).

Therefore, one cycle of the fuel injection pump P,
That is, the pilot injection and the main injection are performed by one upward movement of the plunger 1.

The plunger 1 can be rotated by the horizontal movement of the control rack 15, and the first lead 4 and the second lead 5 of the plunger 1 are formed in a required shape so that the respective leads 4 can be rotated. It is possible to control the injection characteristics of the fuel by changing the opening area and the communication timing of the intake / exhaust oil port 6 and the sub-port 7 of the plunger barrel 2 of Nos.

Here, a specific example will be described with reference to the drawings.

FIG. 3 is a developed schematic view of one plunger applied to the fuel injection pump P of this embodiment.

In the figure, the first lead 4 is formed with an appropriate lead angle, and the second lead 5 has its upper edge portion horizontal and its lower edge portion different from the first lead 4 described above. It is formed so that an inclination in the opposite direction is provided. Further, a to c of FIG. 3 show three types of communication states of the first lead 4 and the second lead 5 with respect to the oil intake / exhaust oil port 6 and the sub port 7 during one cycle of the fuel injection pump P by three types of rotational displacement of the plunger 1. The positional relationship of is shown.

First, when the plunger 1 is rotated and the relative positional relationship between the leads 4 and 5 and the ports 6 and 7 is controlled as shown in FIG. 3b, the pilot is operated similarly to the description of the operation of the fuel injection pump P. After performing the injection, the main injection is performed and the one cycle is completed ((B) in FIG. 4).

Next, when the plunger 1 is controlled so as to have the relative positional relationship shown in FIG. 3A, the fuel injection pump P is supplied with fuel from the intake / exhaust oil port 6 into the plunger barrel 2 and the plunger 1 rises. Although pressure feeding is started, the first lead 4 and the suction / exhaust oil port 6 communicate with each other without the second lead 5 and the sub-port 7 communicating with each other.
That is, when the plunger 1 is controlled to a in FIG. 3, the fuel injection pump P performs only the main injection without performing the pilot injection and ends the one cycle ((A) in FIG. 4).

When the plunger 1 is controlled so that the relative positional relationship shown in FIG. 3c is obtained and the fuel injection pump P is operated, pilot injection is performed and then main injection is performed. Since the opening area for the sub-port 6 is narrower than that when the plunger 1 is controlled to b in FIG. 3, the pressure drop during this period is small and the start timing of the main injection is accelerated, so that the pilot injection and the main injection are continuously performed. As shown in FIG. 4 (C), the pilot injection exhibits injection characteristics that are not independent of the main injection.

As described above, by rotating the plunger 2, the opening area of the second lead 5 with respect to the sub-port 7 can be changed while changing the communication timing of the first lead 4 with respect to the oil suction / discharge port 6. Thus, the fuel injection characteristic of the fuel injection pump P can be changed to perform fuel injection adapted to the load condition of the engine. For example,
When the engine is in the light load operation state, the plunger 1 is controlled to a of FIG. 3 to perform the fuel saving operation (fuel injection characteristic shown in FIG. 4A), and conversely the high load operation state is achieved. In this case, the plunger 1 is controlled as shown in FIG. 3 to prevent ignition delay, and at the same time, a large amount of fuel is injected to prevent smoke (black smoke) due to the main injection start timing delay (see FIG. 4). (Fuel injection characteristics shown in (C)). Further, during medium load operation with a high usage rate, by controlling the plunger 1 to b in FIG. 3 and performing the required pilot injection and main injection (fuel injection characteristics shown in FIG. 4B), the efficiency of the engine can be improved. You can drive.

Further, for example, in the case of the relative positional relationship shown in FIG. 3b, the injection characteristic changes as shown in FIG. 5 according to the engine speed. That is, as the subport 7 has a relatively small diameter and the rotational speed increases, the communication time between the second lead and the subport 7 decreases, so that the pressure drop between the pilot injection and the main injection decreases as the rotational speed increases. It decreases and both injections become continuous. Therefore, the output demand corresponding to the increase in the rotation speed is also met.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a main part configuration diagram showing a fuel injection pump P of the second embodiment.

In the figure, a plunger 20 movably supported in a vertical direction in a plunger barrel 21 has a central hole 3, a first lead 4 and a second lead 5, and further, a first lead 4 A suction hole 23, which communicates with the center hole 3 and is used for sucking fuel, is provided below.
The plunger 20 can be rotated by the movement of the control rack as in the case of the first embodiment.
The timing sleeve 22 is fitted from the outside to 0, and the timing sleeve 22 is movable in the axial direction with respect to the plunger 20 by an operating means (not shown) (Y in FIG. 6 is a top dead center, X is a top dead center). Indicates bottom dead center). That is, the timing sleeve 22 moves vertically with respect to the plunger 20, while the plunger 20 is rotatable relative to the timing sleeve 22.

The timing sleeve 22 is provided with a spill port 24 corresponding to the first lead 4 and a subport 25 corresponding to the second lead 5.

Further, an oil reservoir chamber 26 is formed between the timing sleeve 22 and the plunger barrel 21, and fuel for constant injection is supplied to the oil reservoir chamber 26 from the outside of the plunger barrel 21. The area around 22 is always filled with fuel.

The structure of the fuel injection pump P in the second embodiment other than the above is the same as that of the first embodiment, and hereinafter, those having the same function will be described using the same reference numerals.

Next, the operation of the fuel injection pump P having the above structure will be described.

The injection fuel is sent under pressure by moving the plunger 20 up and down by the cam 9 as in the first embodiment. First, when the plunger 20 descends and the suction hole 23 of the plunger 20 is lower than the lower end portion of the timing sleeve 22, the fuel in the oil reservoir 26 passes through the suction hole 23 in the plunger 20 and the center hole 3 Pumping room 14
Inhaled into. Then, when the plunger 20 rises from the bottom dead center and the suction hole 23 of the plunger 20 is completely blocked by the timing sleeve 22, the fuel filling the fuel pumping chamber 14 is shut off from the outside, and the plunger 20 rises to cause the fuel to flow. It will be pressure-fed to the engine (not shown) through the delivery port 19 (start of pilot injection).

When the plunger 20 is further raised and the second lead 5 reaches the sub-port 25 of the timing sleeve 22, the two are brought into communication with each other, and the fuel in the fuel pumping chamber 14 is filled with the fuel in the center hole 3 of the plunger 20 and the second lead. 5 and the sub port 25 to escape to the oil sump chamber 26, whereby the pressure feeding of fuel is interrupted (end of pilot injection).

When the plunger 20 is further raised and the second lead 5 is displaced from the sub port 25, the fuel pressure feeding chamber 1
No. 4 is shut off from the outside, and the pressure feeding of fuel is started again (start of main injection).

Then, the plunger 20 is further raised, the first lead 4 reaches the spill port 24 of the timing sleeve 22, and when the two communicate with each other, the fuel is fed to the center hole 3 of the plunger 20, the first lead 4 and the spill. It will be sent back to the oil reservoir 26 through the port 24, and again
The pumping of fuel is stopped (end of main injection).

Therefore, one cycle of the fuel injection pump P,
That is, the pilot injection and the main injection are performed by one upward movement of the plunger 20.

Since the plunger 1 can be rotated by the horizontal movement of the control rack 15 and the timing sleeve 22 can be moved in the axial direction of the plunger 20, the first lead 4 and the second lead 4 of the plunger 1 can be moved. By forming the lead 5 into a required shape, it is possible to change the opening area and the communication timing of the timing sleeve 22 of each of the leads 4 and 5 with respect to the spill port 24 and the subport 25, and control the fuel injection characteristics. ing.

Here, a specific example will be described with reference to the drawings.

FIG. 7 is a developed schematic view of one plunger applied to the fuel injection pump P of this embodiment.

In the figure, the first lead 4 is formed with an appropriate lead angle, and the second lead 5 has its upper edge part horizontal and its lower edge part the same as the first lead 4 described above. It is formed so that an angled slope is provided. Further, e and d in the same figure show two types of communication states of the first lead 4 and the second lead 5 with respect to the spill port 24 and the sub port 25 during one cycle of the fuel injection pump P by two types of rotational displacement of the plunger 20. The positional relationship is shown.

First, the plunger 20 is rotated and the relative positional relationship between the leads 4 and 5 and the ports 24 and 25 is shown in FIG.
6 and the timing sleeve 22 is controlled to X in FIG. When the fuel injection pump P is operated in this state, the fuel injection pump P starts pilot injection from the θ ₁ point (solid line 30 in FIG. 8) and then performs main injection from the θ ₂ point (solid line in FIG. 8). 31) The one cycle is ended (first injection example).

Next, the plunger 20 is controlled according to the relative positional relationship shown in FIG.
When the fuel injection pump P is operated with the same position as that in the first injection example, the pilot injection is performed from the point θ ₁ (solid line 30 in FIG. 8) and the second lead Although the sub-port 25 communicates and ends the pilot injection, the opening area of the second lead 5 with respect to the sub-port 25 is narrower than in the case of the first injection example described above, so the start timing of the main injection becomes earlier and θ ₄ point Then, the main injection is performed (dashed-dotted line 32 in FIG. 8) to end the one cycle (second injection example).

Further, the plunger 20 is controlled in the same manner as in the second injection example described above, and the timing sleeve 22 is set to Y in FIG.
When the fuel injection pump P is operated by controlling the fuel injection pump P, the timing of communication between the leads 4 and 5 of the plunger 20 and the ports 24 and 25 is delayed as the timing sleeve 22 moves up. The start timing of the main injection will be delayed. That is, the pilot injection is performed from the θ ₃ point (broken line 33 in FIG. 8), and the main injection is performed from the θ ₂ point (solid line 31 in FIG. 8) to complete the one cycle (third injection example).

That is, as shown in the first to third injection examples, the plunger 20 is rotationally driven to move the plunger 20.
The second lead 5 and the opening area of the timing sleeve 22 with respect to the sub-port 25 are changed, and the communication timing of each lead 4, 5 with respect to each port 24, 25 is changed by the vertical movement of the timing sleeve 22 with respect to the plunger 20. By doing so, the start timing of the pilot injection can be delayed while keeping the start timing of the main injection constant.

The positions and shapes of the first and second leads in the first and second embodiments may be appropriately set according to each device. Similarly, the position and shape of each corresponding port may be appropriately set.

[0056]

As described above, the present invention provides the plunger barrel and the first barrel formed on the plunger barrel.
Of the first oil by reciprocating between the oil drain hole of the
A first lead that is formed on the outer peripheral surface of the plunger and can communicate with the first oil drain hole; and a plunger that is formed on the plunger and that connects the first lead and the first oil drain hole. A fuel injection device for an internal combustion engine, comprising: a communication passage that always communicates with a pressure chamber of a plunger barrel, wherein the plunger and the plunger barrel are relatively rotatable, and an outer peripheral surface of the plunger is in communication with the pressure chamber. A second oil discharge hole capable of communicating with the second lead is provided in the plunger barrel, so that the plunger is rotated to rotate the first lead and the first oil discharge. By changing the communication timing of the holes and changing the opening area for the second lead and the second oil drain hole, the timing of pilot injection and the timing of main injection can be changed. And, the injection amount of the fuel freely varied, it is possible to control the injection characteristics of the fuel injection device itself. In particular, the second oil drain hole communicating with the second lead is formed in the first
Since it is provided separately from the oil drain hole of, the size of each oil drain hole,
By selecting the arrangement or the like, the degree of freedom in design for adjusting the injection characteristics according to the operating state of the engine is increased, and it is possible to perform the optimum fuel injection for the operating state of the engine with a relatively simple configuration.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the essential parts of a fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is a sectional perspective view showing a fuel injection pump of a first embodiment of the present invention.

FIG. 3 is a developed schematic view of one plunger applied to the fuel injection pump of the first embodiment of the present invention.

FIG. 4 is a fuel injection characteristic diagram of the first embodiment of the present invention.

FIG. 5 is a fuel injection characteristic diagram of the fuel injection device according to the present invention as the engine speed increases.

FIG. 6 is a cross-sectional view of the essential parts of a fuel injection pump according to a second embodiment of the present invention.

FIG. 7 is a developed schematic view of one plunger applied to the fuel injection pump of the second embodiment of the present invention.

FIG. 8 is a fuel injection characteristic diagram of the second embodiment of the present invention.

[Explanation of symbols]

 1 Plunger 2 Plunger Barrel 3 Center Hole 4 First Lead 5 Second Lead 6 Intake / Discharge Oil Port 7 Sub Port 14 Fuel Pumping Chamber

Claims (4)

[Claims] 1. A plunger barrel, a first oil drain hole formed in the plunger barrel, a plunger that reciprocates in the plunger barrel to open and close the first oil drain hole, and an outer peripheral surface of the plunger. A first lead formed in the plunger and capable of communicating with the first oil drain hole, and a communication passage formed in the plunger to constantly communicate the first lead with the pressure chamber of the plunger barrel. A fuel injection device for an internal combustion engine in which the plunger and the plunger barrel are rotatable relative to each other, a second lead communicating with the pressure chamber is formed on an outer peripheral surface of the plunger, and the plunger barrel is provided with the second lead. A fuel injection device for an internal combustion engine, comprising: a second oil drain hole that can communicate with a second lead. 2. A plunger barrel, a plunger reciprocating in the plunger barrel, a timing sleeve fitted to the plunger, a first oil drain hole formed in the timing sleeve, and an outer circumference of the plunger. A fuel suction hole for sucking fuel, a first lead that can communicate with the first oil drain hole, and the plunger, the first lead and the fuel suction hole, and the plunger. A fuel passage for the internal combustion engine, the timing sleeve being vertically movable with respect to the plunger; and the timing sleeve and the plunger being rotatable relative to each other. In the injection device, a second lead communicating with the pressure chamber is formed on the outer peripheral surface of the plunger, and the timing sleeve is provided. A fuel injection device for an internal combustion engine, characterized in that a second oil drain hole that is capable of communicating with the second lead is provided. 3. The pressure relief amount from the pressure chamber during the communication period between the second reed and the second oil drain hole is set to decrease as the engine speed increases. The fuel injection device for an internal combustion engine according to claim 1 or 2. 4. The plunger is rotationally displaced according to the load of the engine, and the second lead has a shorter communication period with the second oil drain hole as the plunger is rotationally displaced according to the increase of the load of the engine. The fuel injection device for an internal combustion engine according to claim 1, wherein the fuel injection device has the following shape.