JP2000205083A - Fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high pressure injection, improve combustion efficiency, and reduce a fuel consumption rate by providing an oil chamber wherein an upper surface of a needle valve is faced and an operating shaft for pressurizing the needle valve in the closing direction is housed, and arranging pressure regulating means for regulating operating pressure in the oil chamber. SOLUTION: At the time of operation of an engine, low pressure fuel supplied from a fuel pump is led to a feed passage 3d. In this condition, a plunger 1 is lifted up through a tappet 5 by a returning spring 6 to open the feed passage 3d. When a solenoid device 12 is excited and a poppet valve 2 is opened, fuel in the feed passage 3d is led into a plunger chamber 3a. When the poppet 2 is closed and pressure in a fuel reservoir 11c overcomes the sum of oil pressure in the oil chamber 40 and a set load of a needle valve spring 8, the needle valve 10 is opened, and fuel is injected. In this case, oil pressure in the oil chamber 40 is regulated by an opening/closing valve 41 serving a piezoelectric element 42 as a driving source, and injection control is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device capable of adjusting a valve opening pressure of a fuel injection valve, and more particularly to a fuel injection device comprising an electromagnetic unit injector for adjusting a fuel injection timing by a solenoid driven poppet valve. .

[0002]

2. Description of the Related Art FIGS. 4 and 5 show an example of a prior art electromagnetic unit injector for an internal combustion engine. FIG. 4 is a longitudinal sectional view of a main part thereof, and FIG.

In FIG. 4, reference numeral 3 denotes a main body, in which a plunger 1 is fitted slidably in a reciprocating manner, and a tappet 5 is fitted in an upper tappet hole 5a in a slidable manner. I have. The plunger 1 includes a tappet 5
And is reciprocated 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) via a rocker arm (not shown), and the plunger 1 and the tappet 5 reciprocate integrally against the resilience of the return spring 6 by the fuel cam. ing.

[0004] Reference numeral 3a denotes a plunger chamber.
The top surface of the fuel cell faces to pressurize the fuel introduced thereto. Reference numeral 11 denotes a fuel injection nozzle, 9 denotes a spring cage, and 4 denotes a spacer. The nozzle body 11a of the fuel injection nozzle 11, the spring cage 9 and the spacer 4
Is firmly and fluid-tightly fixed to the main body 3 by screwing the nozzle nut 7 into a screw at the bottom of the main body 3.

A poppet valve hole 3f is formed in the main body 3 on the side of the plunger 1 insertion hole 3j, and the poppet valve 2 is fitted in the poppet valve hole 3f so as to be able to reciprocate. . 3g is a lower hole continuously provided below the poppet valve hole 3f. A valve seat 3h of the poppet valve 2 is provided above the poppet valve hole 3f. Reference numeral 3p denotes 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 the lower hole 3g.

Below the poppet valve 2, a lid 18 having a movement restricting function is fixed by bolts. The upper surface of the lid 18 forms the fuel reservoir 3p together with the lower hole 3g as described above. Fuel is supplied to the fuel reservoir 3p from a fuel reservoir 24 at a lower portion 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 a drain passage 3e described later. An oil sump 3c is formed above the valve seat 3h, and a communication passage 3k is opened between the fuel sump 3p and the oil sump 3c so that the pressure between the two sumps is equalized. Has become.

One end of a fuel passage 3b through which fuel enters and exits the plunger chamber 3a is opened a predetermined distance below 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 solenoid-operated poppet valve 2. Reference numeral 3e denotes an oil drain hole, which communicates with the fuel reservoir 3p and the oil reservoir 3c via the communication passage 3k.

The poppet valve 2 has a conical valve face 2.
m, and is formed by a sliding portion 2b and a valve shaft portion 2c extending upward. An annular groove 21 communicating the fuel passage 3b and the oil sump 3c when the poppet valve 2 opens and closes is provided in the main body 3 around the sliding portion 2b. The upper end surface of the valve stem 2c of the poppet valve 2 is provided in the armature chamber 13a.
A rectangular armature 13 is fastened and fixed to the upper end surface, and a plurality of holes 23 are formed in the armature 13 to allow fuel to pass through when the armature 13 moves.

The poppet valve 2 has a shoulder formed above a conical valve face 2m, and a lower spring receiver 2 is formed here.
6 are engaged. A spring 1 urged in a direction to open the poppet valve 2 is provided above the lower spring receiver 26.
5 and an upper spring support 2 for fixing and limiting the spring 15
7 are installed. Reference numeral 12 denotes a solenoid stator, and the solenoid stator 12 is a solenoid spacer 1
It is fastened and fixed to the main body 3 by bolts 22 via the bolts 4.

The solenoid stator 12 comprises a solenoid case 12d made of, for example, a synthetic resin material, a coil bobbin 12b holding a solenoid coil 12c, and an E-shaped core 12a forming a magnetic circuit. The armature 13 is provided between the solenoid coil 12c and the main body 3. The figure shows a state in which the poppet valve 2 is closed. In this state, the solenoid stator 12
A minimum gap (about 0.05 mm to 0.3 mm) exists between the armature 13 and the opposing working surfaces of the armature 13.

In the open state of the poppet valve 2,
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 with the fuel reservoir 3p when the lid 18 is in contact with the poppet valve 2.

The solenoid coil 12c is connected to a pair of terminals, and these terminals are connected to a solenoid controller 31 (a fuel injection electronic control circuit) and a power supply by electric wiring. The solenoid control device 31 is connected to a detector 32 for detecting an engine speed, an oil temperature, a supply pressure, and the like.

In such a conventional electromagnetic unit injector, during operation of the engine, the fuel from the fuel tank is compared with the fuel from the fuel supply passage in the cylinder head via the fuel pump and the fuel pipe to the fuel reservoir 24 in the lower part of the main body 3 in a predetermined manner. Supplied at very low pressure. The fuel supplied to the fuel reservoir 24 is supplied to the fuel reservoir 3p via a supply passage 3d in the main body 3, and is further discharged to a fuel tank via an oil discharge passage 3e.

FIG. 5A shows a state in which the plunger 1 is lowered. When the poppet valve 2 is closed, the plunger chamber 3a is opened.
The fuel filled in the space is pressurized, and the fuel passage 4
a, the needle valve 10 fitted to the injection nozzle 11 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 that has been pressurized by the plunger 1 is pushed out to the fuel passage 3b, and the fuel injection ends. Further, FIG.
When the plunger 1 changes from descending to ascending, the fuel pressurized to the supply pressure (usually 1 to 6 kgf / cm ² ) flows into the plunger chamber 3a via the fuel passage 3b and is filled. Completes one cycle of fuel injection.

FIG. 6 is a block diagram of the open / close control of the poppet valve by the solenoid control device of the conventional electromagnetic unit injector shown in FIGS. In FIG. 6, the temperature of each part such as the engine speed, the accelerator amount (accelerator depression amount or the fuel rack movement amount is also possible), the supply air pressure, the water temperature, the oil temperature, the exhaust temperature, etc. Amount detector 102, supply pressure detector 1
03, detected by the temperature detector 104 and the like, and received by the input device 106 of the solenoid control device 31.

Each of the above detection signals is input from an input device 106 to a solenoid control unit 108. Reference numeral 107 denotes an injection timing setting unit which sets the relationship between the operating state such as the engine speed and the accelerator amount and the fuel injection timing. ROM is a read-only memory, and RAM is a memory for both reading and reading.

The solenoid control unit 108 compares the detection signal of the operating condition with the fuel injection timing set in the injection timing setting unit to determine a fuel injection timing that matches the detected value of the operating condition. The opening / closing timing of the poppet valve 2 corresponding to the injection timing 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 the opening and closing of the poppet valve 2 in accordance with the opening and closing timing input as described above.

[0018]

In an electromagnetic unit injector according to the prior art as shown in FIGS. 4 to 6, detection of an engine operation state such as an engine speed and an accelerator amount input to a solenoid control device 31 is performed. Based on the signal, the solenoid control device 31 calculates a fuel injection timing suitable for the above-mentioned operation state, and controls the opening and closing of the poppet valve 2 via the solenoid device 12 so as to be at the injection timing.

On the other hand, in the prior art, the needle valve 1
The valve opening pressure of 0 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.

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 FIG. 9A shows a fuel cam (not shown). ) Cam speed, (B) is the solenoid stator 1
2 is a poppet valve control current in FIG.
(D) is the injection pressure, and (E) is the lift of the needle valve 10.

Further, t ₁ starts to lift the poppet valve 2 in the closing direction, t ₂ starts to close the poppet valve 2 and starts to increase the injection pressure P, t ₃ denotes a settling time (decrease time) of the solenoid current,
t ₄ is the solenoid current interruption, t ₅ the poppet valve 2 closes, t ₆ starts lifting the needle valve 10, t ₇ indicates each time the needle valve closure.

As shown in FIG. 9, in the prior art, the poppet valve 2 closes at t _2, the injection pressure starts to rise, and the pressure of the fuel from the plunger chamber 3a acting on the needle valve 10 decreases. When the valve opening pressure P ₁ is reached, the needle valve 10 opens, and fuel is injected from the fuel injection nozzle 11 into a combustion chamber (not shown). The valve opening pressure of the needle valve 10 is constant as described above. Since the injection pressure mode is uniquely determined by the fuel cam, only the injection timing by the poppet valve 2 can be controlled,
Since it is impossible to control the injection pressure, it is impossible to increase the injection pressure in accordance with the operating state of the engine, and to obtain an engine with high combustion efficiency and reduced fuel consumption rate by high-pressure injection. It has become difficult.

In view of the problems of the prior art, the present invention makes it possible to easily control the fuel injection timing and the injection pressure in relation to each other, thereby realizing high-pressure injection, improving combustion efficiency, and improving fuel consumption. It is an object of the present invention to provide a fuel injection device capable of realizing a reduction in the rate.

[0024]

According to the present invention, there is provided an injection valve having an injection hole for injecting fuel into a cylinder, and a reciprocating slide provided on the injection valve. A needle valve fitted so as to be fit, a needle valve spring for pressing the needle valve in the valve closing direction, and a fuel supplied to the plunger chamber by being reciprocated in the main body by a tappet linked to a crankshaft. Pressurized, sent to the needle valve through the fuel passage, and acted on the needle valve, and a plunger that opens the valve, the upper surface of the needle valve faces,
A fuel injection device is provided, wherein an oil chamber accommodating an operating shaft for pressurizing the needle valve in a valve closing direction is provided, and pressure adjusting means for adjusting an operating pressure in the oil chamber is provided.

According to a second aspect of the present invention, in the first aspect, the needle valve is configured such that the pressure of the fuel acting on the needle valve is adjusted by the pressure of the needle valve spring and the pressure adjusting means. The valve is configured to open when it becomes larger than the sum of the hydraulic oil pressure and the hydraulic oil pressure.

According to a third aspect of the present invention, in the first aspect, the needle valve closes when the sum of the pressure by the needle valve spring and the hydraulic oil pressure in the oil chamber becomes larger than the fuel pressure. It is constituted as follows.

According to a fourth aspect of the present invention, in the first aspect, an oil discharge passage communicating with the oil chamber is provided.
An on-off valve for opening and closing the oil drain passage by the pressure adjusting means,
A valve control device for controlling the opening and closing of the on-off valve.

Preferably, the valve control device comprises a piezoelectric element.

According to this invention, the pressurized hydraulic oil is introduced into the oil chamber facing the upper surface of the needle valve, and the pressure of the hydraulic oil acts on the upper surface of the needle valve in the valve closing direction of the needle valve. Accordingly, the valve opening pressure of the needle valve becomes the sum of the pressure in the oil chamber and the pressure due to the set load of the needle valve spring, and the valve opening pressure becomes higher than that of the prior art.

The valve opening pressure is adjusted by changing the opening / closing timing of the on-off valve by the valve control device of the pressure adjusting means, thereby changing the timing of discharging the pressure oil in the oil chamber.

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.

As a result, the injection pressure of the fuel injection valve rises, atomization of the spray is promoted, the combustion efficiency is improved, and the generation of black smoke is reduced.

The invention according to claim 6 relates to specific control means of the valve control device according to claim 4, and in addition to claim 4,
A detection signal of an engine operation state such as an engine speed and an accelerator amount is input, and a valve opening pressure control unit that calculates an opening / closing timing of the oil discharge passage based on the detection signals and outputs the calculated timing to the valve control device. Become.

According to this invention, the valve opening pressure control section compares the detected value of the engine operating state with the reference valve opening pressure corresponding to the operating state, and adjusts the valve opening pressure suitable for the detected value of the operating state. The opening / closing timing of the opening / closing valve is calculated and output to a valve control device including a piezoelectric element. In the valve control device, the on-off valve is opened and closed at the opening and closing timing.

Therefore, according to the present invention, it is 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 in a high output range can be realized.

According to a seventh aspect of the present invention, in addition to the sixth aspect, the fuel injection timing is controlled by connecting or shutting off the fuel passage and the oil discharge passage provided between the fuel passage and the oil discharge passage. A poppet valve to be driven, a solenoid device for driving the poppet valve, and a detection signal of an engine operating state such as an engine speed, an accelerator amount, and the like. Based on these detection signals, the open / close timing of the poppet valve is calculated to calculate the open / close timing of the poppet valve. A solenoid control unit for outputting to a solenoid device is provided, and the opening and closing control of a poppet valve in the related art and the invention of claim 6 are combined.

According to an eighth aspect of the invention, in addition to any one of the first to seventh aspects, the plunger chamber and the oil chamber are connected to each other, and a small-diameter communication passage intersecting the oil drain passage in the middle is provided. Provided.

The ninth aspect of the present invention is the invention according to the eighth aspect.
Therefore, the communication passage is more than the intersection with the oil drain passage.
The upper communication passage on the plunger chamber side and the front of the intersection
It consists of a lower communication passage on the oil storage chamber side,
Inside diameter is d₁, The inner diameter of the lower communication passage_Two, The oil drain passage
The inner diameter of d_ThreeAnd d_Two ^Two> D₁ ^Two  And d_Three ^Two> (D₁ ^Two+ D_Two ^Two).

The invention according to claim 10 is the invention according to claim 8
, The communication passage is formed by a crossing portion with the oil drain passage.
The upper communication passage on the plunger chamber side and the intersection
And a lower communication passage on the oil chamber side.
Let the inner diameter of the passage be d₁, Length L₁, The inner diameter of the lower communication passage
d_Two, When the length is L2, d₁≒ d_Two When, L₁> L_Two  Is set to.

According to this invention, after the valve opening pressure is increased by supplying the pressure oil into the oil chamber and the on-off valve is opened, the diameter d ₁ or the length L _{1 of the} upper communication passage is reduced to the lower part. Since the relationship between the diameter d _{2 and the} length L ₂ of the communication path is set as described above, the flow path resistance of the upper communication path becomes larger than that of the lower communication path, and the passage area of the discharge passage becomes larger. Since it is configured to be larger than that of the lower communication passage, the pressure oil in the oil chamber can be smoothly discharged from the discharge passage, and the valve opening pressure can be controlled accurately and with high responsiveness. it can.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now 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.

FIG. 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. It is a control block diagram.

In FIGS. 1 and 2, reference numeral 3 denotes a main body, in which a plunger 1 is reciprocally slidably fitted in a plunger hole 3j, and a tappet 5 is reciprocally slidably fitted in an upper tappet hole 5a. Have been combined. The plunger 1 is vertically constrained by an engagement groove 5b of a lower end engagement portion of the tappet 5, and reciprocates with the tappet 5.

Reference numeral 6 denotes a return spring, and the plunger 1
And the tappet 5 is urged to return upward. The tappet 5 is connected to a fuel cam (not shown) via a rocker arm (not shown), and the plunger 1 and the tappet 5 reciprocate integrally against the resilience of the return spring 6 by the fuel cam. ing.

Reference numeral 3a denotes a plunger chamber.
The top surface of the fuel cell faces to pressurize the fuel introduced thereto. Reference numeral 3b denotes a fuel passage formed in the main body 3 and communicates with the plunger chamber 3a. Reference numeral 3 d denotes a fuel supply passage provided in the main body 3, the opening of which is opened and closed by the plunger 1.
Reference numeral 11 denotes a fuel injection nozzle, which is a nozzle body 11a and a needle valve 10 which is reciprocally slidably fitted in the nozzle body 11a.
Consists of A fuel reservoir 11c and a plurality of injection holes 11b for fuel injection are provided at the tip of the nozzle body 11a. Reference numeral 10a denotes a fuel passage whose lower end is opened to the fuel reservoir 11c.

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 a lower portion of the main body 3 by a nozzle nut 7a, so that a joining surface 35 between the respective members is formed. 36 are pressed against each other in a fluid-tight manner.

Numeral 8 denotes a needle valve spring housed in the spring cage 9 and a lower surface of the main body 3 and the needle valve 10.
And is mounted with a predetermined set load (mounting load), that is, a set load corresponding to the valve opening pressure of the needle valve 10 as described later. Have been. Reference numeral 10a denotes a fuel passage formed in the spring cage 9. The lower end of the fuel passage 10a communicates with the fuel passage 10a of the nozzle body 11a, and the upper end communicates with the plunger chamber 3a.

A poppet valve hole 3f is provided in the main body 3 on the side of 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 above the poppet valve hole 3f of the main body 3 and pushes the valve case 30 at its upper and lower joint surfaces 39 and 38 so as to be fluid-tight.

Reference numeral 2 denotes a poppet valve, which is reciprocally slidably fitted on the inner periphery of the valve case 30 and has a conical valve face 2m.
When the valve face 2m is in contact with the seat portion 3h, the valve is closed, and when the valve face 2m is separated from the seat portion 3h, the valve is opened.

Reference numeral 15 denotes a spring for returning the poppet valve 2, which is housed in an oil sump 3c formed in the spring case 37, and has a support surface of the spring case 37 and a support surface 2h of the poppet valve 2. And is urged in a direction to open the poppet valve 2. 2n is a fuel groove formed on the outer periphery of the poppet valve 2, 30b is a fuel groove connected to the seat portion of the seat portion 3h and the valve face 2m of the poppet valve 2, and is provided between the fuel grooves 2n and 30b. The opening or closing of the poppet valve 2 enables or disables communication.

3b is a fuel passage provided in the main body 3,
30c is provided in the valve case 30, and the fuel groove 30c
b, the two fuel passages 30c, 30c
b communicates with the plunger chamber 3a.

A plurality of oil passages 30e are provided in the valve case 30 along the circumferential direction.
Is connected to an oil drain (oil drain) 3e provided in the main body 3. Oil drain passages 3e, 30e and spring 15
The oil sump 3c in which is stored is communicated through a minute passage to an armature chamber 13a, which will be described later, so that unnecessary residual pressure is not applied to the poppet valve 2.

A valve shaft 2 extending above the poppet valve 2
An armature 13 made of a magnetic material is fixed to an upper end portion of c by a nut 2q. The armature 13
Is a spacer 14 made of a nonmagnetic material such as aluminum.
Is housed in the armature chamber 13a.

Reference numeral 12 denotes a solenoid device which is constructed as follows. Reference numeral 12a denotes a solenoid case made of a non-conductive material such as a synthetic 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 14 denotes a spacer, and 12a denotes an E-shaped core. A coil bobbin 12b holding a solenoid coil 12c is housed inside the E-shaped core 12a to form a magnetic circuit. FIG. 1 shows the solenoid coil 12.
The state where the current of c is cut off and the poppet valve 2 is opened by the elasticity of the spring 15 is shown.

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).

The chamber in which the needle valve spring 8 is housed is an oil chamber 40, and the oil chamber 40 is
5 and the upper communication passage 44 communicate with the plunger chamber 3a. 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.

As shown in FIG. 2, the upper communication passage 44,
The diameters of the lower communication passage 45 and the discharge passage 46 are respectively d₁,
d_Two, D_ThreeThen, the relationship between these sizes is as follows
Is set. d_Two ^Two> D₁ ^Two  And d_Three ^Two> (D₁ ^Two+ D_Two ^Two) …… (1)

Alternatively, instead of the above equation (1), the length of the upper communication passage 44 is L ₁ and the length of the lower communication passage 45 is L _2.
Then, it may be configured such that L ₁ > L ₂ where d ₁ ≒ d ₂ .

1 and 2, reference numeral 41 denotes an on-off valve comprising a spherical valve for opening and closing the discharge passage 46; 42, a piezoelectric element for driving the on-off valve 41 for opening and closing; and 43, a plug for mounting the piezoelectric element 42. It is. Pressure adjusting means 1 to be described later
16 (see FIG. 3) is a well-known member, which opens and closes the on-off valve 41 attached to it by expanding and contracting according to a voltage. A control voltage is supplied.

The on-off valve 41 may be opened and closed by the following means instead of the piezoelectric element 42.
The first means is such that the on-off valve 41 is attached to the magnetostrictive element, and the length of the on-off valve 41 is changed by changing the magnetic force applied to the magnetostrictive element from the outside to open and close the on-off valve 41.

In the second means, the on-off valve 41 is configured as a valve which can be opened and closed by a solenoid, and the on-off valve is opened and closed by energizing or shutting off the solenoid.

During operation of the engine having the electromagnetic unit injector having such a configuration, a predetermined relatively low pressure (1) is supplied from the fuel supply passage in the cylinder head to the fuel reservoir 24 below the main body 3 through the fuel pump and the fuel pipe.
(About 6 kgf / cm ² ). The fuel supplied to the fuel reservoir 24 is guided to a supply passage 3 d in the main body 3.

The plunger 1 rises via the tappet 5 by the elasticity of the return spring 6 of the tappet 5, and the lower end edge of the plunger 1 is moved to the supply passage 3d.
When the poppet valve 2 is opened by the cooperation of the solenoid device 12 and the armature 13 as described later, the fuel in the supply passage 3d is introduced into the plunger chamber 3a.

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. The solenoid coil 12c is energized by a control signal from a control device 100 described later. Then, a magnetic flux is generated in the solenoid magnetic circuit by the voltage V _1, and an electromagnetic attraction force Fc is generated between the solenoid device 12 and the armature 13. The electromagnetic attraction force Fc is set by the set load of the spring 15 of the poppet valve 2. Otherwise, the combined body of the armature 13 and the poppet valve 2 does not start moving upward.

When the electromagnetic attraction force Fc becomes larger than the set load of the spring 15 at time t ₂ , the armature 13 is attracted by the attraction force Fc of the solenoid device 12 as shown in FIG. rose (lift), 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.

On the other hand, the plunger 1 is lowered via the tappet 5, and the lower end face 3a of the plunger 1 is
₁ closes the supply passage 3d, and the solenoid coil 12c is energized as described above to
Is drawn into the E-shaped core 12a and the poppet valve 2 closes, the plunger chamber 3a and the fuel passages 3b,
The pressures of the fuel tanks 30c, 10a, the fuel reservoir 11c, and the like are increased by being hermetically sealed. When the pressure, that is, the pressure in the fuel reservoir 11c overcomes the sum of the oil pressure in the oil chamber 40 and the pressure due to the set load of the needle valve spring 8 as described later, the needle valve 10 opens, Fuel passage 1 from inside plunger chamber 3a
0a through the fuel reservoir 11c
b into the combustion chamber (not shown) of the engine.

Next, control of the opening and closing 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, the accelerator amount (accelerator depression amount or the fuel rack movement amount is also possible), the supply air pressure, the water temperature, the oil temperature, the exhaust temperature, and the like are respectively indicated by the engine speed detector 101 and the accelerator speed. It is detected by the amount detector 102, the supply pressure detector 103, the temperature detector 104, and the like, and is received by the input device 106 of the control device 100.

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,
The relationship between the operation state such as the accelerator amount and the fuel injection timing is set. ROM is a read-only memory, and RAM is a memory for both reading and reading.

In the solenoid control unit 108,
Similar to the prior art shown in FIG. 6, the detection signal of the operating state is compared with the fuel injection timing set in the injection timing setting unit to determine a fuel injection timing that matches the detected value of the operating state. The open / close timing of the poppet valve 2 corresponding to the above 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 the opening / closing of the poppet valve 2 according to the opening / closing timing input as described above.

On the other hand, reference numeral 115 denotes a valve opening pressure setting unit which controls the engine operating state such as the engine speed and the accelerator amount and the needle valve 1.
A relationship with zero valve opening pressure is set. In the valve opening pressure control unit 114, the detection signal of the operation state input via the input device 106 is compared with a 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 on-off valve 41 to obtain the valve opening pressure suitable for the detected value of the operating state is obtained, and is input to the pressure adjusting means 116 as the voltage of the piezoelectric element 42.

In the pressure adjusting means 116, the voltage value inputted thereto is given to the piezoelectric element 42. The piezoelectric element 4
2 changes the opening degree of the on-off valve 41 by expanding and contracting according to the voltage value.

Here, as described above, fuel is introduced into the oil chamber 40 from the plunger chamber 3a through the upper communication passage 44 and the lower communication passage 45, and as described above, the poppet valve 2 while the plunger 1 is descending. Is closed, and 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 area of the upper communication passage 44 having a minimum diameter (d ₁ <d ₂ ) having an orifice function in the oil chamber 40 = (πd ₁ ² ) /. Oil pressure P ₁ determined by 4
Is generated, the hydraulic pressure P ₁ and the valve opening pressure P of the needle valve spring 8 are increased.
Is the valve opening pressure of the needle valve 10, and a high injection pressure is obtained.

Further, the voltage based on the valve opening pressure control signal from the valve opening pressure control section 115 decreases,
6, the piezoelectric element 42 is contracted, and the on-off valve 41
Is opened, the relationship between the areas of the upper communication passage 44, the lower communication passage 45, and the discharge passage 46 is set as in the above equation (1), so that the pressure oil in the oil chamber 40 flows from the lower communication passage 45 through the lower communication passage 45. After entering the discharge passage 46, the oil is smoothly discharged to the oil discharge passage 47 through the on-off valve 41. As a result, the valve opening pressure of the needle valve 10 is reduced to the valve opening pressure due to the set load of the needle valve spring 8 (the same valve opening pressure as in the related art).

Next, in the time charts shown in FIGS. 7 and 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. (D) shows the displacement of the piezoelectric actuator composed of the piezoelectric element 42, (E) shows the injection pressure, and (F) shows the time change of the needle valve lift.

In FIG. 7, from the state in which the poppet valve 2 is open and the on-off valve 41 is closed, at time t _{1, the} solenoid device 12 is energized by the control signal from the solenoid control unit 108 to suck the armature 13. The poppet valve 2 starts to move upward in the valve closing direction. Voltage supplied to the solenoid unit 12 this time is V _1. At time t _2,
The poppet valve 2 is closed, the plunger chamber 3a side is closed, and the injection pressure shown in FIG.

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) is lowered as the plunger 1 descends. Rises and the oil chamber 40 closed by closing the on-off valve 41 is closed.
The pressure oil in the plunger chamber 3a is supplied into the oil chamber 40 through the upper communication path 44 and the lower communication path 45, and the pressure in the oil chamber 40 also increases as the plunger 1 descends.

[0077] In this case, fuel in the plunger chamber 3a, as described above, the passage area of the upper communicating passage 44 is smaller than the passage area of the lower communication passage 45, i.e., d _{1 ²} <d ^{2 2}
Therefore, the oil is supplied into the oil chamber 40 at a flow rate and a pressure determined by the orifice effect of the upper communication passage 44.

The oil pressure in the oil chamber 40 is controlled by the needle valve 1
0 acts on the upper surface of the needle valve 10 so that the needle valve 10
The valve opening pressure P is the sum of the hydraulic P ₂ of the fluid chamber 40 and the pressure P ₁ by the set load of the needle valve spring 8: P = P ₁ + P _2, and when only the needle valve spring 8 (P ₁₎ And the injection pressure rises.

Next, a period t ₀ after the poppet valve 2 is closed.
At time t ₆ which has undergone, and outputting an open signal of the on-off valve 41 in the valve-opening pressure controller 114 the pressure adjusting means 116, pressure adjustment means 116 is a piezoelectric actuator comprising a piezoelectric element 42 shown in (D) shrinkage At the very least, when the on-off valve 4 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 released from the combustion chamber (not shown).
Injected into.

When the on-off valve 41 is opened, 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, as described above.
^{_{That, d 3 2> (d 1}} 2 + d 2 2) is, and the lower communicating passage 4
5 passage area is larger than that of the upper communication passage 44, i.e. d ₂ ^2> is d ₁ ^2, or the relationship between the length L ₂ of the length L ₁ and the lower communication passage of the upper communicating passage 44 L ₁ > L ₂ (d
₁ ≒ d ₂ ), the flow resistance of the upper communication passage 44 becomes larger than that of the lower communication passage 45, so that the pressure oil in the oil chamber 40 passes through the lower communication passage 44 and passes through the discharge passage 46.
The plunger chamber 3a.
The side does not become the flow resistance of the pressure oil.

As described above, when the open / close valve 41 is opened and the pressure oil in the oil chamber 40 is discharged to the oil discharge passage 47, the oil pressure in the oil chamber 40 does not act on the needle valve 10. , The needle valve 10
Is opened and closed by the set load of the needle valve spring 8 as in the prior art.

At time t ₃ , the solenoid control unit 108 changes the control voltage to the solenoid device 12 to V ₂
And the poppet valve 2 is maintained in the closed state.

Further, when the current of the solenoid device 12 is cut off at time t ₄ , the poppet valve 2 moves down together with the armature 13 by the elasticity of the spring 15 and is fully opened at time t ₅ . At time t ₇ further off valve 41 and a piezoelectric actuator (piezoelectric element 42) is stretched is closed, also the injection pressure is reduced by the opening the poppet valve 2, at time t _8, the needle valve 10 is closed The valve is terminated to terminate the injection.

Therefore, according to this embodiment, after the poppet valve 2 is closed by the valve opening pressure control unit 114, the on-off valve 4
By varying the period t ₀ to 1 is opened, it becomes possible to change the valve opening pressure.

As shown in FIG. 7 and FIG.
After the valve is opened, at time t ₀ , the piezoelectric actuator is extended to close the on-off valve 41, and the valve is opened at time t ₁₁ after the elapse of the period t ₁₂ , as shown in FIG. t
After closing at _13, enables two-stage injection that opens at t _14, the injection pressure is higher than the case of the 1-stage injection as Ps ₂ of Ps ₁ and 8 in FIG. 7 that Can be.

That is, FIG. 8 shows a period t from when the poppet valve 2 is closed: t ₂ to when the on-off valve 41 is opened (= when the needle valve 10 is opened) t ₆ compared to the case of FIG. ₀ occupies a small case. As is clear from both figures, when the period t ₀ is increased as shown in FIG. 7, the pressure rise in the oil chamber 40 after the poppet valve 2 is closed increases. The valve opening pressure rises,
When the period t ₀ is reduced as shown in FIG. 8, the opening timing of the on-off valve 41 is advanced, so that the valve opening pressure becomes smaller than in the case of FIG.

[0087]

As described above, according to the present invention, the hydraulic oil pressurized into the oil chamber is introduced, and the pressure of the hydraulic oil is applied to the needle valve, thereby reducing the valve opening pressure of the needle valve. The pressure due to the set load of the spring can be increased to the pressure obtained by adding the pressure of the hydraulic oil, the valve opening pressure can be increased, and the fuel can be injected at a high injection pressure. Is promoted, the generation of black smoke is prevented, and the combustion can be improved.

Further, according to the present invention, the time difference between the closing timing of the poppet valve and the opening / closing timing of the on-off valve for opening and closing the oil chamber is changed to change the valve opening pressure. Adjustment is possible, and a valve opening pressure suitable for the operating state of the engine 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.

FIG. 2 is an enlarged sectional view of a valve opening pressure adjusting section of the needle valve in the embodiment.

FIG. 3 is a control block diagram of an opening / closing timing and a valve opening pressure of a poppet valve in the embodiment.

FIG. 4 is a longitudinal sectional view of an electromagnetic unit injector according to the related art.

FIG. 5 is an explanatory diagram of an operation of a poppet valve in the related art.

FIG. 6 is a block diagram of an open / close control of a poppet valve of an electromagnetic unit injector according to the related art.

FIG. 7 is a fuel injection characteristic diagram (part 1) according to the embodiment of the present invention.

FIG. 8 is a fuel injection characteristic diagram (part 2) according to the embodiment of the present invention.

FIG. 9 is a diagram corresponding to FIGS. 7 and 8 in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plunger 2 Poppet valve 3 Main body 3a Plunger chamber 3b Fuel passage 3c Oil drain 3e Oil drain 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 Reference Signs List 11a Nozzle body 11b Injection 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 Spring passage 32 spring Fuel passage 32 spring Oil chamber 41 Open / close valve 42 Piezoelectric element 43 Plug 44 Upper communication path 45 Lower communication path 46 Drain path 47 Oil discharge path 100 Control device 101 Engine rotation speed detection circuit 102 accelerator amount detector 103 supply air pressure detector 104 temperature detectors 108 solenoid control unit 114 opening pressure controller 116 pressure regulating means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 61/10 F02M 61/10 F 61/20 61/20 N

Claims (10)

[Claims] 1. An injection valve having an injection hole for injecting fuel into a cylinder, a needle valve fitted reciprocally slidably to the injection valve, and a needle valve for pressing the needle valve in a valve closing direction. A spring and a tappet interlocked with a crankshaft are slid back and forth in the main body to pressurize the fuel supplied into the plunger chamber, send the fuel to the needle valve via a fuel passage, and act on the needle valve to open it. In a fuel injection device comprising a plunger for valve operation, an oil chamber in which an upper surface of the needle valve faces, and an operation shaft for pressing the needle valve in a valve closing direction is provided, and an operating pressure in the oil chamber is adjusted A fuel injection device comprising: a pressure adjusting unit that performs pressure adjustment. 2. The needle valve according to claim 1, wherein a pressure of the fuel acting on the needle valve is larger than a sum of a pressure of the needle valve spring and a hydraulic oil pressure in an oil chamber adjusted by the pressure adjusting means. The fuel injection device according to claim 1, wherein the fuel injection device is configured to open. 3. The needle valve is configured to close when a sum of a pressure of the needle valve spring and a hydraulic oil pressure in an oil chamber becomes larger than a fuel pressure.
The fuel injection device according to claim 1. 4. An oil discharge passage communicating with the oil chamber is provided, and the pressure adjusting means includes an open / close valve for opening and closing the oil discharge passage, and a valve control device for controlling the opening and closing of the open / close valve. The fuel injection device according to claim 1. 5. The fuel injection device according to claim 4, wherein said valve control device comprises a piezoelectric element. 6. A valve opening pressure which receives a detection signal of an engine operation state such as an engine speed, an accelerator amount and the like, calculates an opening / closing timing of the oil discharge passage based on the detection signal, and outputs the timing to the valve control device. The fuel injection device according to claim 4, further comprising a control unit. 7. A poppet valve provided between the fuel passage and the oil drain passage to control fuel injection timing by communicating or blocking the fuel passage and the oil drain passage, and a solenoid device for driving the poppet valve And a solenoid control unit which receives detection signals of an engine operation state such as an engine speed and an accelerator amount, calculates opening / closing timing of the poppet valve based on these detection signals, and outputs the calculated timing to the solenoid device. The fuel injection device according to claim 6. 8. The fuel injection device according to claim 1, wherein the plunger chamber and the oil chamber are connected, and a small-diameter communication passage intersecting with the oil discharge passage is provided on the way. 9. An intersection between the communication passage and the oil drain passage.
An upper communication passage closer to the plunger chamber than the
And a lower communication passage closer to the oil chamber than the upper portion.₁, The inner diameter of the lower communication passage
d_Two, The inner diameter of the oil drain passage_ThreeAnd d_Two ^Two> D₁ ^Two  And d_Three ^Two> (D₁ ^Two+ D_Two ^Two9. The fuel injection device according to claim 8, wherein: 10. The communication path includes an upper communication path on the plunger chamber side with respect to the intersection with the oil drain passage, and a lower communication path on the oil chamber side with respect to the intersection. When the inner diameter of the communication passage is d ₁ , the length is L ₁ , the inner diameter of the lower communication passage is d ₂ , and the length is L ₂ , when d ₁ ≒ d ₂ , L ₁ > L _2. 9. The fuel injection device according to claim 8, wherein