JPH0942034A - Fuel injector of directly injecting diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve emission and fuel consumption by reducing combustion noise in low speed/low load range of a directly injecting diesel engine without inducing any drop of output and additionally expediting atomization of fuel. SOLUTION: In a two step fuel injection nozzle, for instance, an intermediate lift area is set on the idle side, and in the intermediate lift area, the constant of a spring 39 is set so as to hold the intermediate lift (for instance, 30μ), while the lift of a needle valve 33 can not reach a pre-lift (for instance 60μ). Namely, spring constants are set in such a way that relationship among the valve opening pressure (PN1 ) of a nozzle 31 regulated by the load of a spring before opening of the valve, an injection pressure (PN2 ) equivalent to the load of spring immediately after opening the valve, and a nozzle internal pressure (PN0 ) having correlation to an ejection pressure satisfies PN2 >PN0 >PN1 in an idle range and satisfies PN0 >PN2 >PN1 in order than the idle range.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection device for a direct injection diesel engine.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 22167/1990.
As described in Japanese Patent Publication No. 4, the fuel injection nozzle of the engine is configured to perform a two-stage lift of a pre-lift and a full lift, and in the low speed / low load region, the fuel is injected by the pre-lift mainly for a long injection period to generate combustion noise. It is known to reduce the above.

[0003]

A so-called direct injection diesel engine, which directly injects fuel metered and pressurized by a fuel injection pump into a combustion chamber by a fuel injection nozzle, has excellent output characteristics and good fuel consumption. It is also widely used for vehicles. However, the direct injection diesel engine has a large combustion noise, and when it is used for passenger cars, the combustion noise at idle is a problem, and how to reduce the combustion noise at low speed and low load including idle. It is an issue.

The present invention reduces combustion noise in a low-speed / low-load side idle region of a direct-injection diesel engine without causing a reduction in output, and at the same time promotes atomization of fuel to reduce emissions and fuel consumption. The purpose is to improve.

[0005]

According to the present invention, a fuel injection pump for metering and pressurizing fuel and discharging it at a discharge pressure substantially proportional to an engine speed, and a nozzle internal pressure are defined by a spring load of a spring before valve opening. A fuel injection nozzle having a needle valve that opens and lifts when a predetermined nozzle opening pressure is exceeded, the fuel injection nozzle is connected to a fuel injection pump, and the fuel that is metered and pressurized is discharged into the combustion chamber. It is premised on a fuel injection device for injection. In such a fuel injection device, the nozzle opening pressure (PN ₁ ) defined by the spring load of the spring before valve opening and the injection pressure (PN ₂ ) corresponding to the spring load of the spring immediately after opening the valve are set. , the relationship between the discharge pressure and the nozzle pressure are correlated (PN _o) is the PN _o in the slow and low-load region and PN _OL, the PN _o in high-speed and high-load region when the PN _OH, low speed and In a predetermined area on the low load side, for example, in the idle area, PN ₂ > PN _OL
> PN ₁ , PN _OH > P in high speed / high load range
N ₂ > PN ₁ and PN _OL <PN _OH
The spring constant of the spring is set, and the nozzle internal pressure characteristic is also set. By doing so, the needle valve of the fuel injection nozzle opens, but the lift does not increase in the predetermined region on the low speed / low load side, and the intermediate small lift amount does not reach the normal pre-lift amount. To do. Therefore, the injection period becomes longer, the combustion period becomes longer, and rapid combustion is prevented, so that the combustion noise is reduced and
The injection period is long, and the injection is a high-velocity gap injection in which the sheet gap of the needle valve seat portion, which has a smaller clearance area than the nozzle opening area of the nozzle tip, is used as the throttle portion. Is improved, and emission and fuel efficiency performance are improved. Further, since it is not necessary to change the nozzle opening pressure, it is possible to achieve combustion improvement by atomizing the fuel under high pressure conditions and to achieve high output.

In the present invention, the fuel injection nozzle may be a multi-stage lift type fuel injection nozzle that forms a pre-lift region on the low speed / low load side. When applied to the multi-stage lift type fuel injection nozzle, the relationship between the nozzle opening pressure, the injection pressure and the nozzle internal pressure is PN _{2 in} the pre-lift region.
> PN _OL > PN ₁ is preferable, and by doing so, it is possible to inject a small gap by the intermediate lift position of the pre-lift, and the effect of the multi-stage characteristics is added
The effect of reducing the combustion noise in the low load range is further enhanced.

Further, the fuel injection nozzle may be a one-stage lift type.

Further, in the fuel injection nozzle, the nozzle opening pressure may be mechanically fixed.

Further, in the case of a multi-cylinder engine, a fuel injection nozzle is arranged for each cylinder. However, if there is variation in the spring constant of the spring of the fuel injection nozzle among the cylinders, etc. in the low speed / low load region, In this case, the injection timing and the injection period vary, which causes variations in combustion, resulting in large angular velocity fluctuations and deterioration of vibration components. Therefore, it is preferable to control the fuel injection pump by a feedback signal so that the injection periods in the predetermined region on the low speed / low load side are evenly spaced.

[0010]

FIG. 1 shows a schematic structure of a two-stage lift type fuel injection nozzle according to an example of the embodiment of the present invention.
In this fuel injection nozzle 1, a needle valve 3 is attached to a nozzle body 2, and a sliding portion 3a of the needle valve 3 is slidable on a nozzle portion 2a at the tip of the nozzle body 2.
The nozzle body 2 has a nozzle 4 at the tip of the sliding portion 3a.
A pintle portion 3b protruding inward is provided, and a conical tapered seat surface 3c is formed between the sliding portion 3a and the pintle portion 3b. A first-step spring receiving portion 2b is provided in the center of the inside of the nozzle body 2, and a first-step spring 5 is mounted between the first-step spring receiving portion 2b and the rear end of the needle valve 3. Further, the intermediate rod 6 is loosely fitted in the nozzle body 2 from the side opposite to the first-step spring 5 so as to be axially movable, passing through the first-step spring receiving portion 2b. The intermediate rod 6 has a flat plate portion 6a which is seated on the surface of the first-stage spring receiving portion 2b opposite to the spring receiving surface, and the flat plate portion 6a.
And a rod portion 6b extending from the center of the nozzle body 2 in the axial direction of the nozzle body 2. The rod portion 6b penetrates the first-stage spring receiving portion 2b and always forms a predetermined gap with the needle valve 3. A second-stage spring receiving portion 2c is provided at the rear end of the nozzle body 2, and the flat plate portion 6a is movable inside the nozzle body 2 toward the second-stage spring receiving portion 2c. A second-stage spring 7 is mounted between the flat plate portion 6a and the second-stage spring receiving portion 2c of the nozzle body 2. Further, in FIG. 1, 8 is a fuel introduction passage, and 9
Is a fuel escape passage. The fuel injection nozzle 1 is provided for each cylinder of the engine, and is arranged so that the injection port 4 is opened at substantially the center of the combustion chamber. Then, it is connected to a fuel injection pump 10 described later via an injection pipe.

In the fuel introduction passage 8 of the fuel injection nozzle 1,
The fuel which is metered and pressurized by the fuel injection pump 10 and discharged is sent. When the pressure of the fuel discharged from the fuel injection pump 10 (discharge pressure) is P _P , the pressure inside the fuel injection nozzle 1 (nozzle internal pressure) PN ₀ is slightly larger than P _P due to the influence of the injection pipe and the like. When the nozzle internal pressure PN ₀ exceeds the nozzle opening pressure PN ₁ , the first stage spring 5 is compressed and the needle valve 2 opens. Here, the nozzle opening pressure PN
_1, the spring load of the first stage spring 5 at the valve opening before ie set when a F _1, a pressure receiving area of the needle valve 3 before opening and A _1, as defined in PN ₁ = F ₁ / A ₁ And F ₁ =
k ₁ × x ₀₁ (where x ₀₁ is the shortened length of the first-stage spring 5 at the time of setting), and PN ₁ = k ₁ × x ₀₁ / A ₁ .

When the needle valve 3 opens, the spring load of the first stage spring 5 increases. That is, if the spring load when the needle valve 3 is opened and the shortened length of the first-step spring 5 is increased by x _p1 (first-step lift amount) is F ₂ , F ₂ = k ₁ × (x ₀₁ + x _p1 ).
And F ₂ increases as the first stage lift amount x _p1 of the needle valve 3 increases. Further, when the needle valve 3 is opened, the pressure receiving area also changes. When the pressure receiving area after opening the valve is A ₂ , the needle valve 3
Until the nozzle abuts the intermediate rod 6, the first stage lift amount x _p1 increases as long as the nozzle internal pressure PN ₀ is larger than F ₂ / A ₂ . If F ₂ / A ₂ and PN ₀ are in balance, the lift amount is fixed at that position. When the needle valve 3 comes into contact with the intermediate rod 6, in addition to the nozzle internal pressure PN ₀ and the spring load F ₂ of the first-stage spring 5, the second-stage spring 7 is set to the needle valve 3 via the intermediate rod 6. Spring load F ₃ is applied. here,
If the shortened length of the second step spring 7 at the time of setting is x ₀₂ , F ₃
= K ₂ × x ₀₂ . Then, the nozzle internal pressure PN ₀ becomes (F ₂
The needle valve 3 does not move until + F ₃ ) / A ₂ is exceeded, and the pre-lift (for example, 60 μ) is maintained. Also, PN ₀ is (F ₂ +
When F ₃ ) / A is exceeded, the intermediate rod 7 is pushed up and the lift of the needle valve 3 increases again. Then, the increased amount of the lift, that is, the second-stage lift amount is x _p2 , the spring load of the first-stage bar / net 5 at the time of the second-stage lift is F ₄ , and the spring load of the second-stage spring 7 at the time of the second-stage lift. Is F ₅ , F ₄ = k ₁ × (x ₀₁
+ X _p1 + x _p2 ) and F ₅ = k ₂ × (x ₀₂ + x _p2 ). Then, the lift increases until the nozzle internal pressure PN ₀ is balanced with (F ₄ + F ₅ ) / A ₂ or reaches the full lift regulated by a stopper (not shown).

The nozzle internal pressure PN ₀ is defined by the discharge pressure P _P of the fuel injection pump 10. The discharge pressure P _P is determined by the plunger speed of the fuel injection pump 10 as described later, and specifically depends on the rotational speed of the drive shaft of the fuel injection pump 10 and the cam profile. Further, the rotation speed of the drive shaft changes depending on the engine speed, and the cam profile changes according to the injection amount control according to the engine speed, the load, and the like. Therefore, the characteristic of the nozzle internal pressure PN ₀ changes depending on the engine speed and the load. Therefore, as shown in FIG.
In the region diagram of engine speed and load, the low-speed / low-load side is the first-stage lift area only for the first-stage lift,
The high-load side has a two-stage lift area of pre-lift and full lift. Further, in this example, the intermediate lift region is set on the idle side of the first stage lift region, and the lift of the needle valve 3 is pre-lifted (for example, 60
The spring constant of the first stage spring 5 is set so as to maintain an intermediate lift of, for example, 30 μ without reaching (μ). That is, there is a correlation between the nozzle opening pressure (PN ₁ ) defined by the spring load of the spring before opening the valve, the injection pressure (PN ₂ ) corresponding to the spring load of the spring immediately after opening, and the discharge pressure. The relationship with the nozzle internal pressure (PN _o ) is such that PN ₂ > PN _OL > PN ₁ in the above intermediate lift region when PN _o is PN _OL in the low speed / low load region.
In the low-speed, low-load first-stage lift area and the high-speed, high-load two-stage lift area, excluding the intermediate lift area, PN _o
The when the _{PN OH, PN OH> PN 2} > PN 1 and so as the spring constant is set. PN _OL and PN _OH are PN _OL
<There is a PN _OH relationship.

The characteristic of the needle valve lift amount (nozzle lift characteristic) by setting the intermediate lift region, the first stage lift region and the second stage lift region in this way is as shown in FIG. At times, the lift of the needle valve 3 changes to an intermediate lift (for example, 30μ) that does not reach the pre-lift (for example, 60μ). Therefore, the injection period becomes longer,
The combustion period is prolonged, rapid combustion is prevented, combustion noise is reduced, fuel atomization is promoted, combustion is improved, and emission and fuel efficiency performance are improved. In addition, in other operating regions, the normal two-stage lift characteristic is obtained.

FIG. 4 shows an example of a fuel injection pump 10 for pumping pressurized fuel to the fuel injection nozzle 1. The fuel injection pump 10 shown in FIG. 4 is a so-called distributed injection pump, and includes a drive shaft 11 that is rotationally driven by a crankshaft of an engine, a cam disk 12 that is driven by the rotation of the drive shaft 11, and a cam disk 12. By as many face cams 13 as the number of cylinders provided on the outer periphery of the end surface on the side of the drive shaft 11, a plunger 14 connected to the center of the end surface of the cam disk 12 opposite to the face cam 13, and abutting on the face cam 13,
A roller 15 for lifting the rotating cam disk 12 together with the plunger 14, a plunger spring 16 for urging the plunger 14 in a direction to press the cam disk 12 against the roller 15, and a vane type fuel supply pump 17 driven by the drive shaft 11. , An inlet port 19 for introducing the fuel supplied from the fuel supply pump 17 into the plunger chamber 18, an outlet port 21 for the number of cylinders provided so as to sequentially meet the discharge port 20 of the plunger 14 by the rotation of the plunger 13, and The delivery valve 22 provided at the tip of the outlet port 21, the control sleeve 24 that changes the injection period and the injection amount by adjusting the opening position of the escape port 23 of the plunger 14, and the maximum injection by opening and closing the inlet port 19 Is equipped with a fuel-cut solenoid 25 to regulate the. In addition, the fuel injection port 10 is provided with a governor that is driven through a gear 26 and adjusts the position of the control sleeve 24 according to the engine speed to regulate the maximum speed, and the roller 15 according to the engine speed. A timer is provided for controlling the injection timing by adjusting the phase of the drive shaft 11 with respect to the drive shaft 11.

In the fuel injection pump 10 described above, fuel is sent by the fuel supply pump 17, and the inlet port 1
9 leads to the plunger chamber 18. Then, the drive shaft 11 is driven by the crankshaft of the engine, and the cam disk 12 reciprocates simultaneously with the rotation, so that the fuel in the plunger chamber 18 is pressurized and communicates with the discharge port of the plunger 13 and each outlet port 21. As a result, the fuel is distributed to the fuel injection nozzles 1 of each cylinder via the delivery valve 22. Further, the effective stroke of the plunger 13 is adjusted by the control of the control sleeve 24, and thereby the injection period and the injection amount are controlled. The control sleeve 24 is controlled by a governor, and is feedback-controlled by an ECU (engine control unit) as described later. Further, the roller 15 is moved by the timer in the direction opposite to the rotation of the drive shaft 11 as the engine speed increases, whereby the lift timing of the face cam 13 is advanced. Further, the timer is feedback-controlled by the ECU.

The discharge pressure P _P of the fuel injection pump 10 is determined by the plunger speed, and the plunger speed is determined by the rotational speed of the drive shaft 11 and the cam profile of the face cam 13. And, at the time of low engine speed, the rotation speed of the drive shaft 11 is low,
The plunger speed is low and therefore the discharge pressure P _P is low. Further, as the engine speed increases, the discharge pressure P _P also increases. Further, the nozzle internal pressure PN ₀ is equal to the fuel injection pump 10
The influence of the injection tube or the like connecting the fuel injection nozzle 1, P _P
It is slightly higher, and again rises with engine rotation.

The nozzle lift characteristic is set so as to achieve the intermediate lift at the idle time as described above. However, if the spring constant of the fuel injection nozzle 1 of each cylinder varies, the injection timing and the injection period vary from cylinder to cylinder. In such a case, there is a concern that variations in combustion will occur, the angular velocity fluctuation will increase, and the vibration component of the engine will deteriorate. Therefore, the ECU feedback-controls the control sleeve 24 via the governor,
Further, by performing feedback control of the timer, t ₁ = t ₂ = t ₃ = t ₄ in FIG. 5 and the deterioration of the vibration component due to the inter-cylinder injection variation is suppressed. FIG. 6 is a block diagram of a control system that performs such feedback control.

The present invention can also be applied to the case where the fuel injection nozzle is of the one-stage lift type. FIG. 7 shows an example of a single stage lift type fuel injection nozzle to which the present invention is applied. In this fuel injection nozzle 31, a needle valve 33 is attached to a nozzle body 32, and the nozzle body 32 is fixed to a holder body 35 by a taining nut 34. The needle valve 33 includes a sliding portion 33a and a needle portion 33b, and a conical taper seat surface 33c is formed on the needle portion 33b so as to face the injection hole 36 of the nozzle body 32. The lift of the needle valve 33 is restricted by the end surface of the holder body 35. Further, a pressure pin 37 is provided so as to penetrate the end surface of the holder body 35, and the tip of the pressure pin 37 is in contact with the head of the needle valve 33. Then, an adjusting screw 38 is attached to the holder body 35, and a spring 39 is provided between the pressure pin 37 and the adjusting screw 38.
Is installed. And, in the nozzle body 34,
An oil reservoir 40 is formed at a position surrounding a connecting portion between the sliding portion 33a of the needle valve 33 and the needle portion 33b, and a fuel passage 41 for introducing fuel into the oil reservoir 40 is formed. An escape passage 42 is provided so as to penetrate the adjusting screw 38. Fuel injection nozzle 3
No. 1 is provided for each cylinder of the engine, and the injection holes 36 are arranged so as to open at substantially the center of the combustion chamber.

The fuel injection nozzle 31 is also connected to, for example, the fuel injection pump 10 shown in FIG. 4, and the fuel which is metered and pressurized and discharged is fed into the fuel passage 42. Then, when the nozzle internal pressure PN ₀ exceeds the nozzle opening pressure PN ₁ , the spring 39 is compressed and the needle valve 32 opens. Here, the spring constant of the spring 39 is the nozzle internal pressure PN ₀ , the nozzle opening pressure PN ₁ corresponding to the spring load before valve opening, and the injection pressure PN ₂ corresponding to the spring load of the spring 39 after valve opening. The relationship of PN ₂ > PN _O > PN ₁ when idle
Outside idle sets PN _O> PN _2> PN ₁ and becomes like. By making such settings, the nozzle lift characteristic becomes as shown in FIG.
Is changed to an intermediate lift (for example, 30 μ) that does not reach the full lift (for example, 60 μ), and the injection period is lengthened. As a result, combustion noise during idling is reduced, atomization of fuel is promoted, and emission and fuel efficiency performance are improved. In other driving ranges, the normal one-step lift characteristic is obtained.

The present invention can also be applied to a central plunger type fuel injection nozzle as shown in FIG. In this fuel injection nozzle 51, a needle valve 53 is attached to a nozzle body 52. The needle valve 53 includes a sliding portion 53a and a needle portion 53b,
The needle portion 53b has a nozzle hole 54 of the nozzle body 52.
A seat surface 53c having a conical taper shape is formed to face, and a pintle portion 53d is formed at the tip thereof. Further, a pressure pin 56 is arranged at an end portion on the needle valve 53 side in a spring chamber 55 formed inside the nozzle body 52, and a spring 57 is mounted between the pressure pin 56 and the other end of the spring chamber 55. ing. Further, a fuel pressure chamber 58 is formed at the other end of the spring chamber 55 so as to face the pressure pin 56, and a fuel pressure rod 59 whose one end fits into a cylinder is provided at the other end of the rod 59. Are arranged to face the pressure pin 56 with a predetermined gap at the time of setting. Then, the passage 60 for supplying the fuel pressure to the fuel pressure chamber 58 and the spring chamber 5
5 is provided with a passage 61 for supplying fuel pressure, these two passages 60, 61 are connected to one fuel pressure supply passage 62, and a duty control solenoid valve 63 is provided at the connecting portion. The solenoid valve 63 performs duty control according to the engine load and rotation speed,
Thereby, the fuel pressure balance between the fuel pressure chamber 58 and the spring chamber 55 is changed, and the substantial spring constant is changed. Further, in the nozzle body 52, an oil reservoir 64 is formed at a position surrounding a connecting portion of the sliding portion 53a of the needle valve 53 and the needle portion 53b, and a fuel passage 65 for introducing fuel into the oil reservoir 64 is formed. Has been done.

The fuel injection nozzle 51 is provided for each cylinder of the engine, and is arranged so that the injection hole 54 opens in the approximate center of the combustion chamber. Also, for example, it is connected to the fuel injection pump 10 shown in FIG. Then, the fuel that has been metered and pressurized and discharged is fed into the fuel passage 42. Then, when the nozzle internal pressure PN ₀ exceeds the nozzle opening pressure PN ₁ , the spring 57 is compressed and the needle valve 53 opens. Here, the substantial spring constant added with the fuel pressure adjusted by the solenoid valve 61 is the nozzle internal pressure PN ₀ , the nozzle opening pressure PN ₁ corresponding to the spring load before valve opening, and the spring 57 spring after valve opening. relationship between the injection pressure PN ₂ corresponding to the load is, during _{idling, PN 2> PN O> PN} 1 , and the outside idle sets PN _O> PN _2> PN ₁ and becomes like. In this case, the nozzle lift characteristic can be set in either FIG. 3 or FIG.

Next, experimental data of various characteristics according to the present invention will be described by taking the embodiments of FIGS. 1 to 6 as examples.

FIG. 10 is a needle valve lift sensor waveform showing the nozzle lift during idling. The data is 200kgf when the nozzle opening pressure is 230kgf / cm ^2.
/ Cm ² and 180 kgf / cm ² are shown. The pre-lift is 60μ and the engine speed is 700 rpm. As can be seen from this data, the nozzle opening pressure is 230 kgf / cm.
^An intermediate lift can be obtained by setting the value to ² .

FIG. 11 shows that the engine speed is 700 rpm and the static injection timing is TDC when the engine is idling.
It is a wave form diagram of cylinder pressure when it is set (top dead center). The data shows that the first set pressure (nozzle opening pressure) is 230 kg.
and if the set pressure of the second stage at f / cm ² is 260kgf / cm ^2, and if the set pressure of the first stage is set pressure of the second stage at 200 kgf / cm ² is 260kgf / cm ^2, a set of first stage pressure is if the set pressure of the second stage at 180 kgf / cm ² is 260kgf / cm ^2. As can be seen from this data, the rapid combustion can be suppressed by setting the nozzle opening pressure to 230 kgf / cm ² .

FIG. 12 shows NOx (nitrogen oxide) and PM.
1500 indicating the concentration of (fine particles), Pe = 3 (engine speed 1500 rpm, average effective pressure 3 kgf / cm ² ).
The data at the time of normal operation and the data at the time of IDLE (idle), circles are 230/260 (the first stage is 230
If the second stage in kgf / cm ² is 260kgf / cm ^2), triangles 140/260 (one stage 140kgf /
If the second stage in cm ² is 260kgf / cm ^2), square marks indicate the case of the 200/230 (second stage the first stage is at 200 kgf / cm ² is 230 kgf / cm ^2), respectively. Note that the scale is changed for 1500 and Pe = 3 and IDLE. As can be seen from this data, NOx and PM during idling can be reduced by setting the nozzle opening pressure to 230 kgf / cm ^2, and
PM during normal operation can be reduced.

FIG. 13 is data showing changes in the maximum injection pressure Pmax due to the static injection timing during idling, and FIG. 14 is the maximum increase rate dp / dθ ma of the injection pressure.
It is data showing x. Further, FIG. 15 similarly shows the combustion sound level (SPL) at the static injection timing during idling.
Is the data indicating All of these data show that the nozzle opening pressure is 230 kgf / cm ² , 200 kgf / cm ² , 1
This is for 80 kgf / cm ² . As can be seen from these data, the nozzle opening pressure was set to 230 kgf / cm ²
By setting Pmax and dp /
Noise can be reduced by reducing dθ max.

FIG. 16 is data showing changes in fuel consumption due to static injection timing during idling. The data shows that the nozzle opening pressure is 230 kgf / cm ² and 200 kgf / c.
It is for m ² and 180 kgf / cm ² . As can be seen from this data, the nozzle opening pressure is 230 kgf / c.
When m ² is set, as long as the injection timing is set in a normal range centered on TDC, the fuel economy at idle becomes better than at least when the nozzle opening pressure is 200 kgf / cm ² .

[0029]

According to the present invention, in a fuel injection device for a direct injection diesel engine, a nozzle lift in a region such as idle on a low speed / low load side can be made a minute lift, and the fuel can be lifted by the minute lift. It is possible to achieve the atomization of No. 1 and the reduction of combustion noise, and the improvement of the output by the normal lift in the output required region under the high injection pressure condition.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a two-stage lift type fuel injection nozzle according to the present invention.

FIG. 2 is a lift region diagram of the fuel injection nozzle of FIG.

FIG. 3 is a lift characteristic diagram of the fuel injection nozzle of FIG.

FIG. 4 is a structural diagram of a distributed fuel injection pump according to the present invention.

FIG. 5 is a time chart showing a fuel injection timing and an injection period of each cylinder in the present invention.

FIG. 6 is a block diagram of a pump feedback control system according to the present invention.

FIG. 7 is a structural diagram of a one-stage lift type fuel injection nozzle according to the present invention.

FIG. 8 is a lift characteristic diagram of the fuel injection nozzle of FIG.

FIG. 9 is a schematic structural diagram of a central plunger type fuel injection nozzle according to the present invention.

FIG. 10 is a sensor waveform diagram showing a nozzle lift during idling.

FIG. 11 is a waveform diagram of cylinder pressure during idling.

FIG. 12 is a graph of NOx and PM concentration.

FIG. 13 is a graph of the maximum injection pressure during idling.

FIG. 14 is a graph of the maximum increase rate of injection pressure during idling.

FIG. 15 is a graph of combustion sound level during idling.

FIG. 16 is a graph of fuel consumption during idling.

[Explanation of symbols]

 1 Fuel injection nozzle (two-stage lift type) 3 Needle valve 5 First stage spring 6 Intermediate rod 7 Second stage spring 10 Fuel injection pump 14 Plunger 24 Control sleeve 31 Fuel injection nozzle (one stage lift type) 33 Needle valve 39 Spring 51 Fuel Injection nozzle (central plunger type) 53 Needle valve 57 Spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Yamauchi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (5)

[Claims] 1. A fuel injection pump for measuring and pressurizing fuel to discharge at a discharge pressure substantially proportional to an engine speed, and a nozzle internal pressure exceeding a predetermined nozzle opening pressure defined by a spring load of a spring before valve opening. Fuel for a direct injection diesel engine, which includes a needle valve that opens and lifts when opened, and a fuel injection nozzle that is connected to the fuel injection pump and injects the fuel metered and pressurized by the fuel injection pump into the combustion chamber. In the injection device, the relationship between the nozzle opening pressure, the injection pressure corresponding to the spring load of the spring immediately after the valve opening, and the nozzle internal pressure is such that the nozzle opening pressure is PN ₁ , the injection pressure is PN ₂ , the nozzle internal pressure and PN _o, also, low-speed,
PN _o the PN _OL in the low load region, the PN _o when the PN _OH in high-speed and high-load _{region, PN 2> PN OL> PN} 1 becomes in a predetermined area of the low-speed, low-load, high-speed,
Fuel for a direct injection diesel engine, characterized in that the spring constant of the spring and the nozzle internal pressure characteristic are set so that PN _OH > PN ₂ > PN ₁ and PN _OL <PN _OH in the high load range. Injection device. 2. The fuel injection nozzle is a multi-stage lift type fuel injection nozzle that forms a pre-lift region on the low speed / low load side, and the relationship between the nozzle opening pressure, the injection pressure, and the nozzle internal pressure is: PN ₂ > P in the pre-lift area
The fuel injection device for a direct injection diesel engine according to claim ₁ , wherein N _OL > PN ₁ . 3. The fuel injection device for a direct injection diesel engine according to claim 1, wherein the fuel injection nozzle is a one-stage lift type. 4. The fuel injection device for a direct injection diesel engine according to claim 1, wherein the nozzle opening pressure is mechanically fixed. 5. The means for controlling the fuel injection pump by a feedback signal so that the engine is a multi-cylinder engine and the injection periods in the predetermined region on the low speed / low load side are equidistant. , 3 or 4, a fuel injection device for a direct injection diesel engine.