JP3716119B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, the fuel injection timing is controlled by a fuel injection device for an internal combustion engine, particularly a solenoid, which can reduce nitrogen oxide (NOx) in exhaust gas by reducing the fuel injection amount during the ignition delay period. The present invention relates to an electromagnetic unit injector.
[0002]
[Prior art]
FIGS. 3 to 4 show an example of the prior art of an electromagnetic unit injector for an internal combustion engine proposed in Japanese Utility Model Application No. 1-54602, FIG. 3 is a longitudinal sectional view of an essential part thereof, and FIG. It is explanatory drawing.
[0003]
In FIG. 3, 3 is a main body, and the plunger 1 is fitted in the plunger hole 3j so as to be slidable in a reciprocating manner, and the tappet 5 is fitted in the upper tappet hole 5a so as to be slidable in a reciprocating manner.
The plunger 1 is engaged with an upper end engaging portion of the tappet 5 so as to reciprocate together with the tappet 5. A return spring 6 is urged to return the plunger 1 and the tappet 5 upward.
The tappet 5 is connected to a fuel cam (not shown) through a rocker arm (not shown), and the plunger 1 and the tappet 5 are reciprocated against the elastic force of the return spring 6 by the fuel cam. ing.
[0004]
Reference numeral 3a denotes a plunger chamber, which faces the top surface of the plunger 1 and pressurizes the fuel introduced therein.
11 is a fuel injection nozzle, 9 is a spring cage, and 4 is a spacer. The nozzle body 11 a of the fuel injection nozzle 11, the spring cage 9 and the spacer 4 are formed by screwing a nozzle nut 7 into a screw at the bottom of the main body 3. 3 is firmly and fluid-tightly fixed.
[0005]
A poppet valve hole 3f is formed in the main body 3 at the side of the hole 3j for inserting the plunger 1, and the poppet valve 2 is fitted in the poppet valve hole 3f so as to be capable of reciprocating.
Reference numeral 3g denotes a lower hole provided continuously below the poppet valve hole 3f. A valve seat 3h for the poppet valve 2 is provided above the poppet valve hole 3f.
3p is a fuel reservoir formed in the lower hole 3g. The fuel reservoir 3p is defined by a lid 18 fixed to the lower surface of the main body 3 by bolts 2b and a lower hole 3g.
[0006]
A lid 18 having a function of restricting the downward movement of the poppet valve 2 is fixed by a bolt. The upper surface of the lid 18 forms the fuel reservoir 3p as described above together with the lower hole 3g. Fuel is supplied to the fuel reservoir 3p from a fuel reservoir 24 at the bottom of the main body 3 through a supply passage 3d in the main body 3. This fuel is discharged to a fuel tank (not shown) through an oil discharge passage 3e described later. A drain oil reservoir 3c is formed at the top of the valve seat 3h. A communication passage 3k is opened between the fuel reservoir 3p and the drain oil reservoir 3c so that the pressure between the reservoirs is equalized. It has become.
[0007]
One end of the fuel passage 3b for fuel flow into and out of the plunger chamber 3a opens below a predetermined distance from the annular conical valve seat 3h of the poppet valve hole 3f. The fuel flow between the oil sump 3c and the fuel passage 3b is controlled by the poppet valve 2 operated by a solenoid.
Reference numeral 3e denotes an oil drain hole which communicates with the fuel reservoir 3p and the drain oil reservoir 3c through the communication passage 3k.
[0008]
The poppet valve 2 has a conical valve face 2m, and is formed by a sliding portion 2b and a valve shaft portion 2c extending upward. Around the sliding portion 2b, an annular groove 21 is provided in the main body 3 for communicating the fuel passage 3b and the oil reservoir 3c when the poppet valve 2 is opened and closed. The poppet valve 2 is hollow for the purpose of weight reduction, and has a hexagonal hole that is used when an armature 13 to be described later is tightened. The upper end surface of the valve shaft portion 2c of the poppet valve 2 is opened to the armature chamber 13a, and a rectangular armature 13 is fastened and fixed to the upper end surface, and fuel is passed through the armature 13 during its movement. Therefore, a plurality of holes 23 are formed.
[0009]
The poppet valve 2 forms a shoulder portion above the conical valve face 2m, and a lower spring receiver 26 is engaged therewith. Above the lower spring receiver 26, a spring 15 biased in a direction to open the poppet valve 2 and an upper spring receiver 27 for fixing and restricting the spring 15 are installed. Reference numeral 12 denotes a solenoid stator. The solenoid stator 12 is fastened and fixed to the main body 3 by a bolt 22 via a solenoid spacer 14. The solenoid stator 12 includes a solenoid case 12d made of, for example, a synthetic resin material, a coil bobbin 12b that holds the solenoid coil 12c, and an E-shaped core 12a that forms a magnetic circuit. The armature 13 is installed between the solenoid coil 12 c and the main body 3. The figure shows a state in which the poppet valve 2 is closed. In this state, there is a minimum gap (about 0.05 mm to 0.3 mm) between the operating surfaces of the solenoid stator 12 and the armature 13 facing each other.
[0010]
When the poppet valve 2 is opened, the lower end surface 2 a of the poppet valve 2 is in contact with the upper surface of the lid 18. The lid 18 has a passage (hole or groove) 18c for communicating the cavity 2p of the poppet valve 2 and the fuel reservoir 3p in a contact state with the poppet valve 2.
[0011]
A pair of terminals are connected to the solenoid coil 12c, and the terminals are connected to a solenoid control device 31 (fuel injection electronic control circuit) and a power source by electric wiring. The solenoid control device 31 is connected to a detector 32 that detects engine speed, oil temperature, supply air pressure, and the like.
[0012]
In such a conventional electromagnetic unit injector, during operation of the engine, the fuel from the fuel tank passes through the fuel pump and the fuel pipe and is supplied from the fuel supply passage in the cylinder head to the fuel reservoir 24 at the bottom of the main body 3 at a predetermined relatively low pressure. Supplied in. The fuel supplied to the fuel reservoir 24 is supplied to the fuel reservoir 3p via the supply passage 3d in the main body 3, and is further discharged to the fuel tank via the oil drain passage 3e.
[0013]
FIG. 4A shows a state in which the plunger 1 is lowered. When the poppet valve 2 is closed, the fuel filled in the plunger chamber 3 a is pressurized and passes through the fuel passage 4 a of the spacer 4 to the injection nozzle 11. The fitted needle valve 10 is opened to start fuel injection. Next, as shown in FIG. 4B, when the poppet valve 2 is opened, the fuel in the plunger chamber 3a pressurized by the plunger 1 is pushed out to the fuel passage 3b, and the fuel injection is completed. Further, as shown in FIG. 4 (C), when the plunger 1 starts to rise rather than descend, the fuel pressurized to the supply pressure (usually 1 to 6 kgf / cm ² ) flows into the plunger chamber 3a through the fuel passage 3b. Thus, one fuel injection cycle is completed.
[0014]
[Problems to be solved by the invention]
In the electromagnetic unit injector according to the prior art shown in FIG. 3, as shown in FIG. 5, the poppet valve is closed and the injection pressure starts to rise, and after the needle valve is opened, the injection is started. After the needle valve is once slightly lowered when the needle valve is opened, it rises proportionally as the plunger descends.
[0015]
Accordingly, in such a conventional technique, the injection pressure uniquely increases according to the stroke of the plunger. Therefore, the injection amount particularly during the ignition delay period of the injection timing increases as the injection pressure increases. There is a problem that the rise of combustion after the period becomes abrupt, the pressure in the cylinder rises, and the amount of NOx generated easily increases.
[0016]
In view of the problems of the prior art, the present invention obtains an injection amount corresponding to engine performance by suppressing an increase in injection pressure during an ignition delay period in the initial stage of injection and an increase in injection rate (injection amount) associated therewith. Accordingly, an object of the present invention is to provide a fuel injection device in which a gentle and stable combustion is performed, a combustion temperature is lowered, and a generation amount of NOx is reduced.
[0017]
[Means for Solving the Problems]
The present invention is order to achieve the foregoing object, an injection valve having a nozzle hole for injecting fuel into the cylinder, a needle valve that mated for reciprocal sliding in the injection valve, a needle valve closed A needle valve spring that presses in the valve direction;
Fuel injection provided with a plunger that is reciprocally slid in the main body by a tappet that is linked to a crankshaft, pressurizes fuel supplied into the plunger chamber, and acts on the needle valve to open the needle valve In the device
In the axial direction, the plunger is divided into a first plunger located on the tappet side and a second plunger that faces the plunger chamber and is movable relative to the first plunger.
The gist is provided with a retracting means for retracting the second plunger toward the non-plunger chamber for a predetermined period after the needle valve is opened.
[0018]
The present invention relates to a specific configuration of the saving means, invention of claim 1 wherein, prior Symbol retracting means, the first plunger and is interposed between the second plunger, the set load the needle It consists of a spring set larger than the valve opening load of the valve spring.
[0019]
Therefore, in this invention, as set forth in claim 2, when the set load of the spring of the retracting means is Sp ₁ and the opening load of the needle valve is Sp ₂ , the relationship between the two is
Sp ₁ / A ₁ > Sp ₂ / A ₂
However, A ₁ (cross-sectional area of the second ^{_{plunger) = π (D 1) 2}} /4
A ₂ (effective sectional area of needle valve) = π (D ₂ ² −d ² ) / 4
D ₁ = diameter of the second plunger
D ₂ = Diameter of the large diameter part of the needle valve
d = the diameter of the small diameter part of the needle valve.
[0020]
The invention of claim 3, wherein the pre-Symbol retracting means comprises an oil chamber formed between the first plunger and the second plunger, and an adjustment to pressure regulator the pressure of the oil chamber Become.
[0021]
According to a fourth aspect of the present invention, in any one of the first to third aspects, an adjusting means for adjusting a retracting period of the second plunger is provided between the first plunger and the second plunger.
[0022]
According to a fifth aspect of the present invention, in any one of the first or third aspects, a control valve is provided that controls an injection timing by opening and closing between the plunger chamber and the oil discharge passage.
[0023]
Further, preferably as claimed in claim 6, consists of a poppet valve, wherein the control valve is driven by a solenoid.
[0024]
According to this invention, while the first plunger and the second plunger are integrally lowered, the second plunger closes the fuel supply passage, and then the control valve closes the oil discharge passage to increase the fuel pressure in the plunger chamber. When the pressure acts on the needle valve and reaches the valve opening pressure of the needle valve spring, the needle valve opens and fuel injection starts.
After the start of injection, the injection pressure is slightly reduced by opening the needle valve, and then the injection pressure is increased by lowering the two plungers. However, when the injection pressure exceeds the set pressure of the spring on the plunger side, the spring is bent. The second plunger starts to be displaced relative to the first plunger, the injection pressure is maintained at the set pressure for a certain period, and the increase is suppressed.
[0025]
Therefore, according to this invention, the increase in the injection pressure within the initial ignition delay period from the start of the increase in the injection pressure is suppressed, and therefore the injection amount is smaller than that of the prior art, and after the ignition delay period. Rapid rise of combustion is suppressed.
As a result, the initial combustion becomes gentle and stable combustion, the combustion temperature is lowered, and the amount of NOx generated is reduced.
[0026]
According to the invention of claim 6, wherein the control valve, the high-precision one big in response to engine operating conditions can be freely controlled to open and close to reduce the reduced vital NOx generation amount of the fuel consumption rate The resulting fuel injection mode can be obtained.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Only.
[0028]
FIG. 1 is a cross-sectional view of an electromagnetic unit injector according to an embodiment of the present invention.
In FIG. 1, reference numeral 3 denotes a main body. A first plunger 1a and a second plunger 1b, which will be described later, are slidably fitted in the plunger hole 3f, and the tappet 5 is reciprocally slid in the upper tappet hole 5a. Fits freely.
The first plunger 1 a is engaged with the engaging groove 5 b of the upper end engaging portion of the tappet 5 so as to reciprocate together with the tappet 5. A return spring 6 is urged to return the plunger 1 and the tappet 5 upward.
The tappet 5 is connected to a fuel cam (not shown) through a rocker arm (not shown), and the plunger 1 and the tappet 5 are reciprocated against the elastic force of the return spring 6 by the fuel cam. ing.
[0029]
Reference numeral 3a denotes a plunger chamber, which faces the top surface of the second plunger 1b and pressurizes the fuel introduced therein.
A fuel supply passage 3b is formed in the main body 3 and is opened and closed by the poppet valve.
Between the first plunger 1a and the second plunger 1b, a spring 32 made of a coil spring is interposed in a spring chamber 32a formed between the plungers 1a and 1b, and extends from the first plunger 1a. by changing the tightening amount of the second plunger 1b nut 1c screwed to an end portion of the support portion 1a ₁ which is, a set load (mounting load) of the spring 32, i.e. the second plunger 1b is the The spring 32 is compressed, and the load that starts to be displaced relative to the first plunger 1a is changed.
[0030]
Further, the in the middle of the support portion 1a ₁ of the first plunger 1a, upper portion 1d and can contact the step portion 1c of the second plunger 1b is formed, displaced relative to the first plunger 1a of the second plunger 1b That is, the stroke S of the second plunger 1b is regulated. The spring 32 may be a disc spring.
41 is a leakage groove for leaked oil, which is carved in the middle of the portion of the main body 3 where the first plunger 1a of the plunger hole 3j is fitted, and is connected to the supply passage 3d by a small-diameter relief hole 42. Yes.
[0031]
A fuel injection nozzle 11 includes a nozzle body 11a, a needle valve 10 fitted in the nozzle body 11a so as to be freely slidable and a nozzle nut 7b for tightening the nozzle body 11a.
A fuel reservoir 11c and a plurality of injection holes 11b for fuel injection are provided at the tip of the nozzle body 11a. A fuel passage 10a has a lower end opened to the fuel reservoir 11c.
[0032]
Reference numeral 9 denotes a spring cage, and 7a denotes a nozzle nut. The spring cage 9 is screwed to the lower portion of the main body 3 by the nozzle nut 7a and presses the joint surface 35 of the both members in a fluid-tight manner.
Further, the nozzle body 11a is screwed to the lower portion of the spring cage 9 by the nozzle nut 7b to press-contact the joint surface 36 of both of them in a fluid-tight manner.
[0033]
A needle valve spring 8 accommodated in the spring cage 9 is interposed between a lower surface of the main body 3 and a spring receiver 8a that is in contact with the head of the needle valve 10, and has a predetermined set load ( Mounting load), that is, with a set load corresponding to the valve opening pressure of the needle valve 10.
Reference numeral 10a denotes a fuel passage formed in the spring cage 9. The lower end communicates with the fuel passage 10a in the nozzle body 11a, and the upper end communicates with the plunger chamber 3a.
[0034]
A poppet valve hole 3f is provided on a side of the plunger hole 3j into which the first and second plungers 1a and 1b are fitted, and a hollow valve case 30 is inserted into the poppet valve hole 3f. Has been.
Reference numeral 37 denotes a spring case, which is screwed into the upper threaded portion of the poppet valve hole 3f of the main body 3 and pushes the valve case 30 so as to be fluid tight at the upper and lower joint surfaces 39 and 38.
[0035]
Reference numeral 2 denotes a poppet valve that is reciprocally fitted to the inner periphery of the valve case 30 and includes a conical valve face 2m. The valve face 2m and the seat portion 3h of the valve case 30 are in contact with each other. The valve is closed when the valve face 2m and the seat 3h are separated from each other.
The inner periphery of the poppet valve 2 is formed hollow, and its lower space 3p communicates with an armature chamber 13a described later via a micro passage so that unnecessary fuel pressure is not applied to the poppet valve 2.
[0036]
Reference numeral 15 denotes a spring for returning the poppet valve 2, which is housed in the spring case 37 and interposed between the support surface of the spring case 37 and the support surface 2 h of the poppet valve 2. Is biased in the direction to open the valve.
Reference numeral 30b denotes a fuel groove formed facing the seat portion 3h on the inner periphery of the valve case 30. The fuel groove 30b passes through a fuel passage 30c in the valve case 30 and a fuel passage 3b in the main body 3. The plunger chamber 3a communicates with the plunger chamber 3a.
[0037]
A plurality of oil discharge passages 30e are provided in the valve case 30 along the circumferential direction. The oil discharge passages 30e communicate with an oil discharge passage (oil discharge outlet) 3e provided in the main body 3. Yes.
[0038]
An armature 13 made of a conductor is fixed to the upper end portion of the valve shaft portion 2c extending above the poppet valve 2 by a nut 2q.
The armature 13 is accommodated in an armature chamber 13a formed in a spacer 14 made of a nonconductive material such as a synthetic resin material.
[0039]
A solenoid stator 12 is configured as follows.
12a is a solenoid case made of a non-conductive material such as a rigid resin material, and is fixed to the upper surface of the main body 3 together with the spacer 14 by a plurality of bolts (not shown).
Reference numeral 12a denotes an E-shaped core in which a coil bobbin 12b for holding a solenoid coil 12c is housed to constitute a magnetic circuit.
FIG. 1 shows a state where the armature 13 is attracted to the solenoid coil 12c side and the poppet valve 2 is closed.
[0040]
The solenoid coil 12c is connected to a solenoid control device 31 that controls the current to the solenoid coil 12c, and is detected by a detector 32 in the solenoid control device 31 as in the prior art shown in FIG. The engine operating state is input from a detector 32 that detects the rotational speed of the engine, the oil temperature, the supply air pressure, and the like.
[0041]
During operation of an engine having an electromagnetic unit injector having such a configuration, a predetermined relatively low pressure (1 to 2) is applied to the fuel reservoir 24 in the lower portion of the main body 3 from the fuel supply passage in the cylinder head via the fuel pump and the fuel pipe. The fuel is supplied at about 6 kgf / cm ² . The fuel supplied to the fuel reservoir 24 is guided to the supply passage 3 d in the main body 3.
[0042]
Then, the elasticity of the return spring 6 of the tappet 5 raises the first plunger 1a and the second plunger 1b through the tappet 5, the second plunger 1b opens the supply passage 3d, and a solenoid as will be described later. When the poppet valve 2 is opened by the cooperation of the stator 12 and the armature 13, the fuel in the supply passage 3d is introduced into the plunger chamber 3a.
[0043]
Next, the solenoid stator 12 by the solenoid control device 31, to explain the operation of the armature 13 and the poppet valve 2, as shown in FIG. 5 (a), when the solenoid coil 12c to the time t ₁ is energized solenoid magnetic Magnetic flux is generated in the circuit, and an electromagnetic attractive force Fc is generated between the solenoid stator 12 and the armature 13, and the armature 13 and the poppet need to be larger than the set load of the spring 15 of the poppet valve 2. The combination of the valve 2 does not move upward.
[0044]
Wherein the time t ₂ when the electromagnetic attractive force Fc is greater than the set load of the spring 15 as shown in FIG. 5 (c), the armature 13 is attracted by the suction force Fc of the solenoid stator 12 side, the poppet valve 2 is increased (lift ) and, at time t ₃ seated on the valve seat 3h of the poppet valve 2, the valve opening is closed.
Then, the drive voltage of the solenoid coil 12c, as shown in FIG. 5 (a), is caused to drop to the voltage V ₂ necessary to close hold poppet valve 2.
[0045]
Meanwhile, the first plunger 1a and the second plunger. 1b, has been moved down through the tappet 5, the lower end portion 1b ₁ of the second plunger 1b closes the supply passage 3d, further the solenoid stator as When the armature 13 is energized and the armature 13 is sucked into the E-shaped core 12a and the poppet valve 2 is closed, the plunger chamber 3a and the fuel passages 3b, 30c, 30b, 10a, 11c, etc. communicating therewith are sealed and the pressure rises. .
When the pressure, that is, the pressure in the fuel reservoir 11c overcomes the set load of the needle valve spring 8, that is, the valve opening pressure, the needle valve 10 opens and is guided from the plunger chamber 3a through the fuel passage 10a to the fuel reservoir 11c. The fuel that has been injected is injected into the combustion chamber (not shown) of the engine from the injection hole 11b.
[0046]
FIG. 2 shows changes over time in injection pressure (injection pressure) and injection rate during such fuel injection, FIG. 2 (A) shows an embodiment of the present invention, and FIG. 2 (B) shows a related art as shown in FIG. Each case is shown.
[0047]
In FIG. 2A, the injection pressure P starts to rise from the point A where the poppet valve 2 is closed. When the point B is reached and the valve opening pressure P ₁ is reached as described above, the needle valve 10 is opened. The rise in the injection pressure P temporarily stops and starts to fall, but the injection pressure P rises again from the point C by the lowering of the first plunger 1a and the second plunger 1b.
[0048]
When the injection pressure reaches a set load (mounting load) corresponding pressure P ₂ of the spring 32 interposed between the first plunger 1a and the second plunger 1b, the spring 32 starts bending, the first even plunger 1a is lowered by the deflection of the spring 32, the injection pressure P is balanced with a set load corresponding pressure P ₂ of the spring 32, shown in D~E shown in FIG. 2 (a) as described below The set load equivalent pressure P ₂ is maintained for a certain period.
[0049]
That is, the relationship of force when the spring 32 starts to bend and the second plunger 1b starts to move relative to the first plunger 1a is expressed by the following equation (1).
P ₂ = Sp ₁ / A ₁ > Sp ₂ / A ₂ (1)
Here, Sp ₁ = Set load of spring 32
A ₁ (cross-sectional area of the second plunger _{1b) = π (D 1)} 2/4
D ₁ = diameter of the second plunger
Sp ₂ = spring force of needle valve 10
A ₂ (Fuel hydraulic pressure working area of needle valve 10) = π (D ₂ ² −d ² ) / 4
D ₂ = diameter of the large diameter portion of the needle valve 10
d = diameter of the small diameter portion of the needle valve 10
And the said spring 32 bends satisfying said (1) Formula, and the bending amount of this spring 32 becomes S of FIG. 1, and the upper-end part 1d of the 2nd plunger 1b and the level | step-difference part 1c of the 1st plunger 1a are. When contacted (point E in FIG. 2A), the second plunger 1b descends in synchronism with the first plunger 1a while the bending of the spring 32 is held at this maximum bending, and the injection pressure P is To rise.
[0051]
When the solenoid drive current is cut off at time t ₆ in FIG. 5, the armature 13 and this poppet valve 2 which is fixed to the be moved down by the elastic force of the spring 15, the valve face 2m valve casing 30 of the poppet valve 2 The poppet valve 2 is opened away from the seat portion 30h.
By opening the poppet valve 2, the fuel in the plunger chamber 3a and the fuel passages 3b, 30c, 10a and the fuel reservoir 11c connected to the plunger chamber 3a passes through the fuel groove 30b and the poppet valve 2, passes through the oil discharge passages 30e and 3e, It is discharged to the fuel tank (not shown) side.
[0052]
When the poppet valve 2 is opened, the injection pressure P drops from the point F in FIG. 2A, and when the pressure becomes lower than the valve opening pressure P _{1 of the} needle valve 10, the needle valve 10 is closed and fuel injection is performed. Ends. Further, the oil draining is continued during the opening period of the poppet valve 2.
The first plunger 1a and the second plunger 1b starts to rise, the lower end surface 1b ₁ of the second plunger 1b opens the supply passage 3d, the fuel is supplied to the plunger chamber 3a, to end the cycle.
[0053]
As described above, according to this embodiment, in the prior art, as shown in FIG. 2 (B), the poppet valve 2 is closed while the plunger 1 (see FIG. 1) is lowered, and the injection pressure P is increased. When the valve opening pressure P ₁ of the needle valve 10 is reached at the point B, the needle valve 10 is opened, and after the injection pressure P is lowered to the point C, the injection pressure P is increased as the plunger 1 is lowered. In this embodiment, as shown in FIG. 2A, after the injection pressure P is lowered to the point C by opening the needle valve 10, the spring 32 bends in a state satisfying the expression (1). As a result, the second plunger 1b is displaced relative to the first plunger 1a, whereby the injection pressure is held at the pressure P ₂ for a certain period (between D and E in FIG. 2A). Rise is suppressed.
[0054]
Therefore, according to the embodiment of the present invention, the fuel injection rate Q in the ignition delay period from the beginning of the increase in the injection pressure (point A in FIG. 2A) is the conventional value as indicated by Q _{2 in} FIG. It becomes smaller than Q _{1 of the} technology, that is, the fuel injection amount is suppressed.
As a result, the sudden rise of the combustion after the ignition delay period is suppressed, and the combustion temperature is lowered and the combustion temperature is lowered, so that the generation amount of NOx is reduced.
[0055]
In the above embodiment, as shown in FIG. 1, the spring 32 is interposed between the first plunger 1a and the second plunger 1b, but the second embodiment is configured as follows.
That is, in FIG. 1, the spring 32 is removed and pressure oil pressurized to a predetermined pressure is introduced into the spring chamber 32a to form a hydraulic chamber, and the pressure in the hydraulic chamber is adjusted by a pressure regulating valve.
[0056]
Therefore, according to the second embodiment, the hydraulic pressure in the hydraulic chamber is set to the spring set load equivalent pressure P ₂ in the equation (1), and the pressure change in the hydraulic chamber is set to the spring 32 in the first embodiment. Set in the same way as the load characteristics (spring constant).
Thereby, according to this 2nd Embodiment, the injection rate fall characteristic in the ignition delay period similar to the characteristic of the injection pressure and injection rate shown by FIG. 2 is obtained like the said 1st Embodiment.
[0057]
【The invention's effect】
As described above, according to the present invention, the needle valve opens from the beginning of the increase of the injection pressure and the injection starts, and when the injection pressure further increases, the spring of the second plunger bends and the second plunger becomes the first plunger. On the other hand, the relative displacement suppresses the increase in the injection pressure for a certain period. As a result, the increase in the injection pressure during the ignition delay period at the initial stage of injection is suppressed, the injection amount is reduced, and the rapid rise of combustion is suppressed.
[0058]
Therefore, according to the present invention, the initial combustion becomes a gradual and stable combustion, the combustion temperature is lowered as compared with the prior art, and the generation of NOx can be reduced.
[0059]
According to the sixth aspect of the invention, the electronic timing of the injection timing can be freely controlled with high accuracy and flexibility corresponding to the operating conditions of the engine, and the optimal fuel consumption rate and NOx reduction can be achieved at the same time. An injection mode can be obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electromagnetic unit injector according to a first embodiment of the present invention.
2A and 2B are injection characteristic diagrams in the first embodiment, where FIG. 2A shows the case of the present invention, and FIG. 2B shows the case of the prior art.
FIG. 3 is a longitudinal sectional view of an electromagnetic unit injector according to the prior art.
FIG. 4 is an operation explanatory diagram of a poppet valve in the prior art.
FIG. 5 is a graph showing operation and injection characteristics of a poppet valve in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a 1st plunger 1b 2nd plunger 2 Poppet valve 3 Main body 3a Plunger chamber 3b Fuel passage 3c Oil drainage reservoir 3e Oil drainage passage 3f Poppet valve hole 5 Tappet 6 Return spring 7a, 7b Nozzle nut 8 Needle valve spring 9 Spring cage 10 Needle Valve 10a Fuel passage 11 Fuel injection nozzle 11a Nozzle body 11b Injection hole 11c Fuel reservoir 12 Solenoid stator 12a E-shaped core 12b Coil bobbin 12c Solenoid coil 12d Solenoid case 13 Armature 13a Armature chamber 14 Spacer 15 Spring 30 Valve case 30c Fuel groove 30 Spring 32a Spring chamber 37 Spring case

Claims (6)

An injection valve having an injection hole for injecting fuel into the cylinder, a needle valve that is slidably fitted to the injection valve, and a needle valve spring that presses the needle valve in the valve closing direction;
Fuel injection provided with a plunger that is reciprocally slid within the main body by a tappet that is linked to a crankshaft, pressurizes fuel supplied into the plunger chamber, and acts on the needle valve to open the needle valve In the device
In the axial direction, the plunger is divided into a first plunger located on the tappet side and a second plunger that faces the plunger chamber and is movable relative to the first plunger.
A retracting means for retracting the second plunger to the side opposite to the plunger chamber for a predetermined period after the needle valve is opened, the retracting means being interposed between the first plunger and the second plunger; A fuel injection device comprising a spring whose load is set larger than a valve opening load of the needle valve spring . When the set load of the spring of the retracting means is Sp ₁ and the opening load of the needle valve is Sp ₂ , the relationship between them is
Sp ₁ / A ₁ > Sp ₂ / A ₂
However, A ₁ (cross-sectional area of the second ^{_{plunger) = π (D 1) 2}} /4
A ₂ (effective sectional area of needle valve) = π (D ₂ ² −d ² ) / 4
D ₁ = diameter of the second plunger
D ₂ = Diameter of the large diameter part of the needle valve
d = set comprising Claim 1 Injector according to become the diameter of the small diameter portion of the needle valve. An injection valve having an injection hole for injecting fuel into the cylinder, a needle valve that is slidably fitted to the injection valve, and a needle valve spring that presses the needle valve in the valve closing direction;
Fuel injection provided with a plunger that is reciprocally slid within the main body by a tappet that is linked to a crankshaft, pressurizes fuel supplied into the plunger chamber, and acts on the needle valve to open the needle valve In the device
In the axial direction, the plunger is divided into a first plunger located on the tappet side and a second plunger that faces the plunger chamber and is movable relative to the first plunger.
An oil chamber formed between the first plunger and the second plunger, wherein the second plunger is retracted to the opposite plunger chamber side for a predetermined period after the needle valve is opened ; When the fuel injection device according to claim Rukoto such and a pressure regulator for adjusting the pressure of the oil chamber. Wherein between the first plunger and the second plunger, the fuel injection device according to any one of claims 1 to 3 comprising an adjusting means for adjusting the storage period of the second plunger. The fuel injection device according to claim 1 or 3, further comprising a control valve that controls an injection timing by opening and closing between the plunger chamber and the oil discharge passage. 6. The fuel injection device according to claim 5, wherein the control valve is a poppet valve driven by a solenoid.

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