JP4146018B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a fuel injection device capable of adjusting a valve opening pressure of a fuel injection valve, and more particularly to a fuel injection device including an electromagnetic unit injector that adjusts fuel injection timing by a solenoid-driven poppet valve.
[0002]
[Prior art]
  4 to 5 show an example of the prior art of an electromagnetic unit injector for an internal combustion engine, FIG. 4 is a longitudinal sectional view of a main part thereof, and FIG.
[0003]
  In FIG. 4, 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 movement limiting function is fixed below the poppet valve 2 with bolts. 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. 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 upper part of the valve seat 3h, and a communication passage 3k is opened between the fuel reservoir 3p and the drain oil reservoir 3c so that the pressure between both 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 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 are installed a spring 15 biased in a direction to open the poppet valve 2 and an upper spring receiver 27 that fixes and restricts the spring 15. 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.
[0010]
  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.
[0011]
  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 that allows the cavity 2p of the poppet valve 2 and the fuel reservoir 3p to communicate with each other when in contact with the poppet valve 2.
[0012]
  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.
[0013]
  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.
[0014]
  FIG. 5A 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. 5B, 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. 5C, when the plunger 1 starts to rise rather than descending, the supply pressure (usually 1 to 6 kgf / cm) is supplied to the plunger chamber 3a through the fuel passage 3b.²) Pressurized fuel flows in and fills, thereby completing one cycle of fuel injection.
[0015]
  FIG. 6 is a block diagram of the poppet valve opening / closing control by the solenoid control device of the conventional electromagnetic unit injector shown in FIGS.
  In FIG. 6, the engine speed, accelerator amount (accelerator stepping amount or fuel rack movement amount), supply air pressure, water temperature, oil temperature, exhaust gas temperature, etc. It is detected by the amount detector 102, the supply air pressure detector 103, the temperature detector 104, etc., and is received by the input device 106 of the solenoid control device 31.
[0016]
  The detection signals are input from the input device 106 to the solenoid control unit 108.
  Reference numeral 107 denotes an injection timing setting unit in which the relationship between the operating state such as the engine speed and the accelerator amount and the fuel injection timing is set.
  The ROM is a read only memory, and the RAM is a read / read memory.
[0017]
  In the solenoid control unit 108, the operation state detection signal and the fuel injection timing set in the injection timing setting unit are matched to obtain a fuel injection timing that matches the detected value of the operation state. The opening / closing timing of the corresponding poppet valve 2 is calculated and output to the solenoid device 12 including the E-shaped core 12a, the coil bobbin 12b, the solenoid coil 12c, and the like.
  The solenoid device 12 controls opening / closing of the poppet valve 2 in accordance with the opening / closing timing input as described above.
[0018]
[Problems to be solved by the invention]
  In the electromagnetic unit injector according to the prior art as shown in FIGS. 4 to 6, the solenoid control device 31 is based on the detection signal of the engine operation state such as the engine speed and the accelerator amount inputted to the solenoid control device 31. The fuel injection timing suitable for the above operating condition is calculated, and the poppet valve 2 is controlled to open and close via the solenoid device 12 so as to reach the injection timing.
[0019]
  On the other hand, in such a conventional technique, the valve opening pressure of the needle valve 10 is uniquely determined by the set load of the needle valve spring 8 and is constant regardless of the operating state of the engine. Further, the fuel injection mode (the change state of the injection pressure) is uniquely determined by the shape of a fuel cam (not shown) that drives the plunger 1.
[0020]
  That is, FIG. 9 shows an operation diagram of the poppet valve 2 and the needle valve 10 of the electromagnetic unit injector (see FIG. 4) according to the prior art, and (A) is a cam of a fuel cam (not shown). (B) is the poppet valve control current in the solenoid stator 12, (C) is the lift of the poppet valve 2, (D) is the injection pressure, and (E) is the lift of the needle valve 10.
[0021]
  T₁Begins to lift poppet valve 2 in the closing direction, t₂Indicates that the poppet valve 2 is closed and the injection pressure P starts to rise, t_ThreeIs the settling time (decrease time) of the solenoid current, t_FourIs the solenoid current cutoff, t_Five
Is the closing of the poppet valve 2, t₆Starts the lift of the needle valve 10 and t₇
Indicates the time of closing the needle valve.
[0022]
  As shown in FIG. 9, in this conventional technique, t₂, The poppet valve 2 is closed and the injection pressure begins to rise, and the fuel pressure from the plunger chamber 3a acting on the needle valve 10 becomes the valve opening pressure P.₁The needle valve 10 opens and fuel is injected from the fuel injection nozzle 11 into the combustion chamber (not shown). The valve opening pressure of the needle valve 10 is constant as described above, and the injection pressure mode is Since it is uniquely determined by the fuel cam, only the injection timing by the poppet valve 2 can be controlled, and the injection pressure cannot be controlled. Therefore, it is not possible to increase the injection pressure in accordance with the operating state of the engine. It becomes impossible to obtain an engine with high combustion efficiency and reduced fuel consumption rate due to high pressure injection.
[0023]
  In view of the problems of the prior art, the present invention can easily control the fuel injection timing and the injection pressure in association with each other, thereby realizing high-pressure injection, improving the combustion efficiency, and reducing the fuel consumption rate. It aims at providing the fuel-injection apparatus which can implement | achieve.
[0024]
[Means for Solving the Problems]
  In order to solve this problem, the present invention includes an injection hole for injecting fuel into a cylinder as an invention according to claim 1.Fuel injection nozzleAnd theFuel injection nozzleAnd a needle valve spring that presses the needle valve in the valve closing direction, and a tappet that is linked to the crankshaft. The pressurized fuel is pressurized and sent to the needle valve through the fuel passage.At the bottomIn a fuel injection device comprising a plunger that acts to open the valve,Attach a spring cage that houses the needle valve spring at the lower end of the body,The upper surface of the needle valve faces and pressurizes the needle valve in the valve closing direction.Fuel from the plunger chamberOil chamber that contains hydraulic oilIt is constituted by a chamber in which the needle valve spring is stored., The oil chamberAnd the plunger chamber are connected by a communication passage extending in the plunger axial direction, a discharge passage is provided that branches in the middle of the communication passage and is connected to an oil discharge passage, and the oil chamber, the communication passage, and the discharge passage are connected to the spring. Formed in the cageAnd furtherDischarge passageA pressure adjusting means for adjusting the operating pressure in the oil chamber, comprising an on-off valve for opening and closing the valve and a valve control device for opening and closing the on-off valveIn the spring cageThe needle valve is provided with the needle valveLower end ofWhen the pressure of the fuel acting on the valve becomes greater than the sum of the pressure by the needle valve spring and the hydraulic oil pressure in the oil chamber adjusted by the pressure adjusting means, and the pressure and oil by the needle valve spring The sum of the hydraulic oil pressure in the roomActs on the lower end of the needle valveIt is configured to close when the fuel pressure becomes higherFurther, the valve control device includes a solenoid control unit that outputs an open / close signal to a solenoid device that drives a poppet valve provided between the fuel passage and the oil discharge passage to control fuel injection timing, and the pressure A valve opening pressure control unit that outputs an opening / closing signal to the adjusting means to control the valve opening pressure, and the valve opening pressure control unit changes a time from when the poppet valve is closed to when the opening / closing valve is opened. The valve opening pressure is controlled byA fuel injection device is proposed.
  According to this invention, the solenoid control unit can control the fuel injection timing, and the valve opening pressure control unit can control the valve opening pressure.
  In the valve opening pressure control unit, the opening / closing timing of the opening / closing valve is such that the detected valve operating pressure matches the detected valve operating pressure by matching the detected valve operating pressure with the reference valve opening pressure corresponding to the operating condition. Is output to a pressure adjusting means (for example, a piezoelectric element). In the valve control device, the opening / closing valve is opened and closed at the opening / closing timing.
  Therefore, according to this invention, it becomes possible to control the opening / closing timing of the on-off valve in accordance with the operating state of the engine, and it is possible to obtain a valve opening pressure suitable for the operating state of the engine. High pressure injection can be realized.
  That is, the valve opening pressure control unit can control the fuel injection pressure by adjusting the valve opening pressure by changing the time from the closing of the poppet valve to the opening of the on-off valve.
[0025]
[0026]
[0027]
[0028]
  Also preferably, as in claim 2, thePressure adjustment meansConsists of a piezoelectric element.
[0029]
  According to this invention, pressurized hydraulic oil is introduced into the oil chamber facing the upper surface of the needle valve, and the pressure of this hydraulic oil acts on the upper surface of the needle valve in the valve closing direction, so that the needle The valve opening pressure is the sum of the pressure in the oil chamber and the pressure due to the set load of the needle valve spring, which is higher than that in the prior art.
[0030]
  The valve opening pressure isFor pressure adjustment meansTherefore, by changing the opening / closing timing of the opening / closing valve, the oil discharge timing of the pressure oil in the oil chamber is changed and adjusted.
[0031]
  Further, if the hydraulic oil in the oil chamber is discharged to release the pressure in the oil chamber, the valve opening pressure can be set only by the set load of the needle valve spring as in the prior art.
[0032]
  As a result, the injection pressure of the fuel injection valve is increased, atomization of the spray is promoted, the combustion efficiency is improved, and the generation of black smoke is reduced.
[0033]
[0034]
[0035]
[0036]
[0037]
[0038]
  Claim3In the described invention, the communication path includes the exhaust passage.OutThe upper communication path is closer to the plunger chamber than the intersection with the passage, and the lower communication path is closer to the oil chamber than the intersection, and the inner diameter of the upper communication path is d₁, The inner diameter of the lower communication path is d₂The exhaustOutThe inner diameter of the passage is d_ThreeWhen
    d₂ ²> D₁ ²
  And
    d_Three ²> (D₁ ²+ D₂ ²)
  It is set to.
[0039]
  Further claims4In the described invention, the communication path includes the exhaust passage.OutAn upper communication path located on the plunger chamber side of the intersection with the passage, and a lower communication path located on the oil chamber side of the intersection,
  The inner diameter of the upper communication path is d₁, Length L₁, The inner diameter of the lower communication path is d₂, Length L₂When
    d₁≒ d₂
  When,
    L₁> L₂
  It is set to.
[0040]
  According to this invention, when the opening / closing valve is opened after increasing the valve opening pressure by supplying the pressure oil into the oil chamber, the diameter d of the upper communication path.₁Or length L₁And the diameter d of the lower communication path₂Or length L₂Therefore, the flow resistance of the upper communication passage is larger than that of the lower communication passage, and the passage area of the discharge passage is larger than that of the upper and lower communication passages. Therefore, the pressure oil in the oil chamber can be discharged smoothly from the discharge passage, and the valve opening pressure can be controlled accurately and with high responsiveness.
[0041]
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, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.
[0042]
  1 is a longitudinal sectional view of an electromagnetic unit injector according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a valve opening pressure adjusting portion of a needle valve, and FIG. 3 is a control block diagram of opening and closing of a poppet valve and valve opening pressure. It is.
[0043]
  1 and 2, reference numeral 3 denotes a main body. A plunger 1 is fitted in the plunger hole 3j so as to be slidable back and forth, and a tappet 5 is fitted in the upper tappet hole 5a so as to be slidable back and forth. Yes. The plunger 1 is reciprocated together with the tappet 5 while being constrained up and down by the engaging groove 5 b of the lower end engaging portion of the tappet 5.
[0044]
  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.
[0045]
  Reference numeral 3a denotes a plunger chamber, which faces the top surface of the plunger 1 and pressurizes the fuel introduced therein.
  A fuel passage 3b is formed in the main body 3 and communicates with the plunger chamber 3a.
  3 d is a fuel supply passage provided in the main body 3, and its opening is opened and closed by the plunger 1.
  A fuel injection nozzle 11 includes a nozzle body 11a and a needle valve 10 fitted in the nozzle body 11a so as to be slidable back and forth.
  A fuel reservoir 11c and a plurality of injection holes 11b for fuel injection are provided at the tip of the nozzle body 11a. 10a is a fuel passage having a lower end opened to the fuel reservoir 11c.
[0046]
  Reference numeral 9 denotes a spring cage, and 4 denotes a spacer. The spring cage 9, the spacer 4 and the nozzle body 11a are screwed to the lower portion of the main body 3 by a nozzle nut 7a, and the joint surfaces 35 and 36 between the members are fluidized. It is in close pressure contact.
[0047]
  A needle valve spring 8 accommodated in the spring cage 9 is interposed between the 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 as described later.
  A fuel passage 10a is 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.
[0048]
  A poppet valve hole 3f is provided on the side of the main body 3 to the plunger hole 3j in which the plunger 1 is fitted, and a hollow valve case 30 is inserted into the poppet valve hole 3f.
  Reference numeral 37 denotes a spring case, which is screwed into a threaded portion at the upper 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.
[0049]
  Reference numeral 2 denotes a poppet valve, which 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 contacted, and is opened when the valve face 2m is separated from the seat portion 3h.
[0050]
  Reference numeral 15 denotes a spring for returning the poppet valve 2, which is housed in a drain oil reservoir 3 c formed in the spring case 37. Between the support surface of the spring case 37 and the support surface 2 h of the poppet valve 2. The poppet valve 2 is interposed and biased in the direction to open the poppet valve 2.
  2n is a fuel groove formed on the outer periphery of the poppet valve 2, and 30b is a fuel groove connected to the seat portion of the seat portion 3h of the poppet valve 2 and the valve face 2m, between the fuel grooves 2n and 30b. The poppet valve 2 is communicated or blocked by opening and closing.
[0051]
  3b is a fuel passage provided in the main body 3, 30c is a fuel passage provided in the valve case 30 and communicated with the fuel groove 30b, and both fuel passages 30c and 3b communicate with the plunger chamber 3a. Yes.
[0052]
  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.
  An oil reservoir 3c in which the oil drain passages 3e and 30e and the spring 15 are accommodated is communicated with an armature chamber 13a, which will be described later, through a minute passage so that unnecessary residual pressure is not applied to the poppet valve 2.
[0053]
  An armature 13 made of a magnetic material 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 the armature chamber 13a formed in the spacer 14 made of a nonmagnetic material such as aluminum.
[0054]
  A solenoid device 12 is configured as follows. 12a is a solenoid case made of a non-conductive material such as a synthetic resin material, for example, 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 14 denotes a spacer, and 12a denotes an E-shaped core. A coil bobbin 12b for holding a solenoid coil 12c is housed in the E-shaped core 12a to constitute a magnetic circuit.
  FIG. 1 shows a state in which the current of the solenoid coil 12 c is cut off and the poppet valve 2 is opened by the elasticity of the spring 15.
[0055]
  A control signal from the solenoid control unit 108 of the control device 100 shown in FIG. 3 is input to the solenoid coil 12c (details will be described later).
[0056]
  The chamber in which the needle valve spring 8 is housed is an oil chamber 40, and the oil chamber 40 is communicated with the plunger chamber 3 a through a lower communication passage 45 and an upper communication passage 44.
  A discharge passage 46 is branched from a connection portion between the upper communication passage 44 and the lower communication passage 45, and the discharge passage 46 is connected to an oil discharge passage 47 via an on-off valve 41 described later.
[0057]
  As shown in FIG. 2, the diameters of the upper communication passage 44, the lower communication passage 45, and the discharge passage 46 are respectively d.₁, D₂, D_ThreeThen, the relationship between these sizes is set as follows.
    d₂ ²> D₁ ²
  And
    d_Three ²> (D₁ ²+ D₂ ²) (1)
[0058]
  Alternatively, instead of the above equation (1), the length of the upper communication passage 44 is set to L₁The length of the lower communication passage 45 is L₂Then, the above d₁≒ d₂As L₁> L₂You may comprise as follows.
[0059]
  1 and 2, reference numeral 41 denotes an open / close valve composed of a spherical valve that opens and closes the discharge passage 46, 42 denotes a piezoelectric element that opens and closes the open / close valve 41, and 43 denotes a plug for attaching the piezoelectric element 42.
  The piezoelectric element 42 constituting the pressure adjusting means 116 (see FIG. 3), which will be described later, is a well-known member that opens and closes the on-off valve 41 attached thereto by expanding and contracting according to voltage. A control voltage is supplied from the control device 100.
[0060]
  Instead of the piezoelectric element 42, the on-off valve 41 may be opened and closed by the following means.
  The first means is configured to attach the on-off valve 41 to a magnetostrictive element and change the length by changing the magnetic force applied to the magnetostrictive element from the outside to open and close the on-off valve 41.
[0061]
  Further, the second means is configured such that the on-off valve 41 is a valve that can be opened and closed by a solenoid, and the on-off valve is opened and closed by energizing or shutting off the solenoid.
[0062]
  During operation of an engine having an electromagnetic unit injector having such a configuration, a predetermined relatively low pressure (1 to 6 kgf / l) is applied to the fuel reservoir 24 at the bottom of the main body 3 from the fuel supply passage in the cylinder head via the fuel pump and the fuel pipe. cm²The fuel is supplied. The fuel supplied to the fuel reservoir 24 is guided to the supply passage 3 d in the main body 3.
[0063]
  Then, the elasticity of the return spring 6 of the tappet 5 raises the plunger 1 through the tappet 5, the lower edge of the plunger 1 opens the supply passage 3 d, and the solenoid device 12, as will be described later. When the poppet valve 2 is opened by the cooperation with the armature 13, the fuel in the supply passage 3d is introduced into the plunger chamber 3a.
[0064]
  Next, the operation of the solenoid device 12 and the poppet valve 2 driven by the solenoid device 12 will be described with reference to FIGS. 1 to 4. When the solenoid coil 12c is energized by a control signal from the control device 100 described later. , Voltage V₁As a result, a magnetic flux is generated in the solenoid magnetic circuit, and an electromagnetic attractive force Fc is generated between the solenoid device 12 and the armature 13, but the armature 13 must be larger than the set load of the spring 15 of the poppet valve 2. The combination of the poppet valve 2 does not move upward.
[0065]
  Time t₂When the electromagnetic attracting force Fc becomes larger than the set load of the spring 15, the armature 13 is attracted by the attracting force Fc on the solenoid device 12 side as shown in FIG. 5C, and the poppet valve 2 is lifted. Time t_ThreeThen, it sits on the valve seat 3h of the poppet valve 2 and the valve opening is closed.
  Thereafter, as shown in FIG. 5A, the drive voltage of the solenoid coil 12c is a voltage V required to keep the poppet valve 2 closed.₂Is lowered.
[0066]
  On the other hand, the plunger 1 is lowered through the tappet 5, and the lower end surface 3 a of the plunger 1.₁Closes the supply passage 3d, and when the solenoid coil 12c is energized as described above 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 passage 3b leading to the plunger chamber 3a, 30c, 10a, the fuel reservoir 11c, etc. are sealed and the pressure rises.
  When the pressure, that is, the pressure in the fuel reservoir 11c overcomes the sum of the hydraulic pressure in the oil chamber 40 and the pressure due to the set load of the needle valve spring 8 as will be described later, the needle valve 10 opens, The fuel led from the plunger chamber 3a through the fuel passage 10a to the fuel reservoir 11c is injected into the combustion chamber (not shown) of the engine from the injection hole 11b.
[0067]
  Next, opening / closing control of the poppet valve 2 and control of the valve opening pressure of the needle valve 10 in the electromagnetic unit injector according to this embodiment will be described with reference to a control block diagram shown in FIG.
  In FIG. 3, the engine speed, accelerator amount (accelerator depression amount or fuel rack movement amount), supply air pressure, water temperature, oil temperature, exhaust gas temperature, and other temperature components are the engine speed detector 101 and the accelerator. It is detected by the quantity detector 102, the supply air pressure detector 103, the temperature detector 104, etc., and is received by the input device 106 of the control device 100.
[0068]
  The detection signals are input from the input device 106 to the solenoid control unit 108 and the valve opening pressure control unit 114.
  Reference numeral 107 denotes an injection timing setting unit in which the relationship between the operating state such as the engine speed and the accelerator amount and the fuel injection timing is set.
  The ROM is a read only memory, and the RAM is a read / read memory.
[0069]
  In the solenoid control unit 108, as in the prior art shown in FIG. 6, the fuel that matches the detection value of the operation state by matching the detection signal of the operation state with the fuel injection timing set in the injection timing setting unit. The injection timing is obtained, the opening / closing timing of the poppet valve 2 corresponding to the injection timing is calculated, and output to the solenoid device 12 comprising the E-shaped core 12a, the coil bobbin 12b, the solenoid coil 12c and the like.
  The solenoid device 12 controls opening / closing of the poppet valve 2 in accordance with the opening / closing timing input as described above.
[0070]
  On the other hand, reference numeral 115 denotes a valve opening pressure setting unit in which the relationship between the engine operating state such as the engine speed and the accelerator amount and the valve opening pressure of the needle valve 10 is set.
  In the valve opening pressure control unit 114, the operation state detection signal input through the input device 106 is matched with the reference valve opening pressure corresponding to the operation state set in the valve opening pressure setting unit 115. Then, the opening / closing timing of the opening / closing valve 41 is determined so that the valve opening pressure conforms to the detected value of the operating state, and is input to the pressure adjusting means 116 as the voltage of the piezoelectric element 42.
[0071]
  In the pressure adjusting means 116, the voltage value input thereto is given to the piezoelectric element 42. The piezoelectric element 42 expands and contracts according to the voltage value to change the opening degree of the on-off valve 41.
[0072]
  Here, as described above, fuel is introduced into the oil chamber 40 from the plunger chamber 3a via the upper communication path 44 and the lower communication path 45, and the poppet valve 2 is closed while the plunger 1 is lowered as described above. Further, when the on-off valve 41 is closed, the high-pressure fuel in the plunger chamber 3a is introduced through the upper and lower communication passages 44 and 45, acts on the upper surface of the needle valve 10, and presses the needle valve 10 in the valve closing direction.
  That is, when both the poppet valve 2 and the on-off valve 41 are closed, the oil chamber 40 has a minimum diameter (d₁<D₂) Area of the upper communication passage 44 = (πd₁ ²) / 4 hydraulic pressure P₁Occurs and this hydraulic pressure P₁And the valve opening pressure P of the needle valve spring 8 becomes the valve opening pressure of the needle valve 10, and a high injection pressure is obtained.
[0073]
  Further, when the voltage based on the valve opening pressure control signal from the valve opening pressure control unit 115 decreases, the piezoelectric element 42 is contracted by the pressure adjusting means 116, and the on-off valve 41 is opened, the upper communication path 44, Since the relationship between the areas of the lower communication passage 45 and the discharge passage 46 is set as shown in the above equation (1), the pressure oil in the oil chamber 40 enters the discharge passage 46 from the lower communication passage 45 and opens the on-off valve 41. The oil is smoothly discharged to the oil discharge passage 47 through the passage.
  As a result, the valve opening pressure of the needle valve 10 is lowered to the valve opening pressure (the valve opening pressure similar to the prior art) due to the set load of the needle valve spring 8.
[0074]
  Next, in the time charts shown in FIGS. 7 to 8, (A) is the speed of the fuel cam (not shown), (B) is the solenoid control current output by the solenoid device 12, and (C) is the poppet valve 2. Lift, (D) shows the displacement of the piezoelectric actuator comprising the piezoelectric element 42, (E) shows the injection pressure, and (F) shows the change over time of the needle valve lift.
[0075]
  In FIG. 7, when the poppet valve 2 is open and the on-off valve 41 is closed, the time t₁The solenoid device 12 is energized by the control signal from the solenoid control unit 108 to suck the armature 13 and the poppet valve 2 starts to move upward in the valve closing direction. At this time, the voltage supplied to the solenoid device 12 is V₁It becomes. And time t₂, The poppet valve 2 is closed, the plunger chamber 3a side is sealed, and the increase in the injection pressure shown in FIG.
[0076]
  At this time, the on-off valve 41 is closed by the extension of the piezoelectric actuator composed of the piezoelectric element 42 by the control signal from the valve opening pressure control unit 114, and the fuel pressure (injection pressure P) increases as the plunger 1 descends. At the same time, the pressure oil in the plunger chamber 3a is supplied into the oil chamber 40 through the upper communication passage 44 and the lower communication passage 45 into the oil chamber 40 sealed by the closing of the on-off valve 41, The pressure in the chamber 40 also increases as the plunger 1 descends.
[0077]
  At this time, the fuel in the plunger chamber 3a has a passage area of the upper communication passage 44 smaller than that of the lower communication passage 45 as described above.₁ ²<D₂ ²Therefore, the oil chamber 40 is supplied with a flow rate and a pressure determined by the orifice effect of the upper communication passage 44.
[0078]
  The oil pressure in the oil chamber 40 is applied to the upper surface of the needle valve 10.CloseActing in the valve direction, the valve opening pressure P of the needle valve 10 is changed to the pressure P by the set load of the needle valve spring 8.₁And the hydraulic pressure P in the oil chamber 40₂With: P = P₁+ P₂In the case of needle valve spring 8 only (P₁) And the injection pressure rises.
[0079]
  Next, the period t after the poppet valve 2 is closed₀After t₆The valve opening pressure control unit 114 outputs an opening signal of the opening / closing valve 41 to the pressure adjusting means 116, and the pressure adjusting means 116 contracts the piezoelectric actuator composed of the piezoelectric element 42 shown in FIG. When the valve is opened, the needle valve 10 shown in (F) starts to open, the needle valve lift increases, and the fuel in the fuel reservoir 11c is injected into the combustion chamber (not shown).
[0080]
  When the on-off valve 41 is opened, as described above, the passage area of the discharge passage 46 is larger than the sum of the passage area of the upper communication passage 44 and the passage area of the lower communication passage 45, that is, d._Three ²> (D₁ ²+ D₂ ²) And the area of the lower communication path 45 is larger than that of the upper communication path 44, that is, d₂ ²> D₁ ²Or the length L of the upper communication passage 44₁And the length L of the lower communication path₂Relationship with L₁> L₂(D₁≒ d₂Therefore, the flow resistance of the upper communication passage 44 is larger than that of the lower communication passage 45, so that the pressure oil in the oil chamber 40 flows smoothly to the discharge passage 46 through the lower communication passage 44. The plunger chamber 3a side does not become the flow resistance of the pressure oil.
[0081]
  As described above, when the on-off valve 41 is opened and the pressure oil in the oil chamber 40 is discharged to the oil discharge passage 47 side, the oil pressure in the oil chamber 40 does not act on the needle valve 10, and the needle The valve 10 is opened and closed by the set load of the needle valve spring 8 as in the prior art.
[0082]
  Also, time t_ThreeThen, the solenoid control unit 108 sets the control voltage to the solenoid device 12 to V.₂And the poppet valve 2 is kept closed.
[0083]
  Furthermore, time t_FourWhen the current of the solenoid device 12 is cut off, the poppet valve 2 is moved down by the elasticity of the spring 15 together with the armature 13, and the time t_FiveIs fully open.
  Furthermore, time t₇, The piezoelectric actuator (piezoelectric element 42) expands to close the on-off valve 41, and the injection pressure decreases by opening the poppet valve 2, and the time t₈, The needle valve 10 closes and the injection ends.
[0084]
  Therefore, according to this embodiment, the valve opening pressure control unit 114 causes the period t from when the poppet valve 2 is closed to when the on-off valve 41 is opened.₀By changing the valve opening pressure, it becomes possible to change the valve opening pressure.
[0085]
  Also, as shown in FIG. 7 to FIG.t ₁₀ The piezoelectric actuator is extended to close the on-off valve 41, and the period t₁₂Time t after elapse₁₁When the valve is opened, the needle valve 10 is t as shown in (F).₁₃After closing at t₁₄The two-stage injection of opening the valve at this time becomes possible, and the injection pressure is Ps in FIG.₁And Ps in FIG.₂Thus, it can be made higher than in the case of the one-stage injection.
[0086]
  That is, FIG. 8 is compared with the case of FIG. 7 when the poppet valve 2 is closed: t₂To the on-off valve 41 when the valve is opened (= when the needle valve 10 is opened) t₆Period t₀Is small, but as can be seen from both figures, the period t₀Is increased as shown in FIG. 7, the pressure increase in the oil chamber 40 after the poppet valve 2 is closed increases to increase the valve opening pressure. Further, as shown in FIG.₀Since the opening timing of the on-off valve 41 is earlier when the value is made smaller, the valve opening pressure becomes smaller than in the case of FIG.
[0087]
【The invention's effect】
  As described above, according to the present invention, the pressurized hydraulic fluid is introduced into the oil chamber, and the pressure of the hydraulic fluid is applied to the needle valve, so that the valve opening pressure of the needle valve depends on the set load of the needle valve spring. The pressure of the hydraulic oil can be increased to the pressure to increase the valve opening pressure, and fuel injection at a high injection pressure can be performed. Smoke generation is prevented and combustion can be improved.
[0088]
  Further, according to the present invention, it is possible to adjust the valve opening pressure by changing the time difference between the closing timing of the poppet valve and the opening / closing timing of the opening / closing valve for opening / closing the oil chamber, which is adapted to the operating state of the engine. A valve opening pressure can be obtained.
  That is, the valve opening pressure control unit can control the fuel injection pressure by adjusting the valve opening pressure by changing the time from the closing of the poppet valve to the opening of the on-off valve.
[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.
FIG. 2 is an enlarged cross-sectional view of a valve opening pressure adjusting portion of the needle valve in the embodiment.
FIG. 3 is a control block diagram of the opening / closing timing and valve opening pressure of the poppet valve in the embodiment.
FIG. 4 is a longitudinal sectional view of an electromagnetic unit injector according to the prior art.
FIG. 5 is an operation explanatory diagram of a poppet valve in the prior art.
FIG. 6 is a block diagram of opening / closing control of a poppet valve of an electromagnetic unit injector according to the prior art.
FIG. 7 is a fuel injection characteristic diagram (part 1) in the embodiment of the present invention.
FIG. 8 is a fuel injection characteristic diagram (part 2) in the embodiment of the present invention.
FIG. 9 is a diagram corresponding to FIGS. 7 to 8 in the prior art.
[Explanation of symbols]
  1 Plunger
  2 Poppet valve
  3 Body
  3a Plunger chamber
  3b Fuel passage
  3c Oil sump
  3e Oil drainage channel
  3f Poppet valve hole
  5 Tappet
  6 Return spring
  7a Nozzle nut
  8 Needle valve spring
  9 Spring cage
  10 Needle valve
  10a Fuel passage
  11 Fuel injection nozzle
  11a Nozzle body
  11b nozzle hole
  11c Fuel reservoir
  12 Solenoid device
  12a E-shaped core
  12b Coil bobbin
  12c solenoid coil
  12d solenoid case
  13 Armature
  13a Armature room
  14 Spacer
  15 Spring
  30 Valve case
  30b Fuel groove
  30c Fuel passage
  32 Spring
  32a Spring chamber
  37 Spring case
  40 Oil chamber
  41 On-off valve
  42 Piezoelectric elements
  43 plug
  44 Upper passage
  45 Lower communication passage
  46 Discharge passage
  47 Oil drain
  100 Control device
  101 Engine speed detection circuit
  102 Axel amount detector
  103 Supply air pressure detector
  104 Temperature detector
  108 Solenoid controller
  114 Valve opening pressure control unit
  116 Pressure adjusting means

Claims (4)

A fuel injection nozzle having a nozzle hole for injecting fuel into the cylinder, a needle valve that is fitted for reciprocal sliding in the fuel injection nozzle, a needle valve spring for pressing the needle valve in the closing direction, The fuel supplied to the plunger chamber is pressurized by reciprocatingly sliding inside the main body with a tappet linked to the crankshaft, sent to the needle valve through the fuel passage, and acting on the lower end of the needle valve to open it. In a fuel injection device comprising a plunger to be valved,
A spring cage in which the needle valve spring is accommodated is attached to the lower end portion of the main body, and hydraulic oil as fuel from the plunger chamber that accommodates the upper surface of the needle valve and pressurizes the needle valve in the valve closing direction is accommodated. An oil chamber is constituted by a chamber in which the needle valve spring is accommodated , the oil chamber and the plunger chamber are connected by a communication path extending in the plunger axial direction, and branched in the middle of the communication path and connected to an oil discharge path is a discharge passage is provided by the oil chamber, a communication passage and a discharge passage formed in the spring cage, further comprising a valve control device which controls the opening and closing of the closing valve and the on-off valve for opening and closing the discharge passage oil provided pressure adjusting means for adjusting the working pressure in the chamber to the spring cage, the needle valve is regulated by the pressure and the pressure adjusting means by pressure the needle valve spring of the fuel acting on the lower end of the needle valve Is the opened when it becomes greater than the sum of the hydraulic fluid pressure in the oil chamber, and the pressure of the fuel sum of the hydraulic fluid pressure in the pressure oil chamber by the needle valve spring acts on the lower end portion of the needle valve The valve control device outputs an open / close signal to a solenoid device that drives a poppet valve provided between the fuel passage and the oil discharge passage. A solenoid control unit for controlling the fuel injection timing; and a valve opening pressure control unit for controlling the valve opening pressure by outputting an opening / closing signal to the pressure adjusting means. The valve opening pressure control unit is configured to close the poppet valve. The fuel injection device is configured to control the valve opening pressure by changing a time from when the valve opens until the on-off valve opens . The fuel injection device according to claim 1, wherein the pressure adjusting means comprises a piezoelectric element. The communication path is composed of an upper communication path that is closer to the plunger chamber than the intersection with the discharge path, and a lower communication path that is closer to the oil chamber than the intersection.
When the inner diameter of the upper communication path is d ₁ , the inner diameter of the lower communication path is d ₂ , and the inner diameter of the discharge path is d ₃ ,
d ₂ ² > d ₁ ²
And
d ₃ ² > (d ₁ ² + d ₂ ² )
It becomes sets to claim 1 Injector according. The communication path is composed of an upper communication path that is closer to the plunger chamber than the intersection with the discharge path, and a lower communication path that is closer to the oil chamber than the intersection.
When the inner diameter of the upper communication path is d ₁ , the length is L ₁ , the inner diameter of the lower communication path is d ₂ , and the length is L ₂ ,
d ₁ ≒ d ₂
When,
L ₁ > L ₂
It becomes sets to claim 1 Injector according.

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