JPH11107890A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change an injection rate in an injection period so that fuel injection for an internal combustion engine is effected at an optimum timing, for example, in any operation state. SOLUTION: A nozzle hole plate 31 is attached in a manner to cover the nozzle hole 36 of a fuel injection valve 30 and the effective diameter of an nozzle hole 34 drilled therein is changed. Concretely, the nozzle hole plate 31 is formed as a piezoelectric element and by expanding or contracting the nozzle hole plate 31 through application of a voltage between electrodes 32a and 32b arranged thereabove and therebelow, the nozzle hole 34 formed in the nozzle hole plate 31 is expanded and contracted. When occasion demands, the nozzle hole plate 31 is constituted in a manner to be divided into a plurality of sections. By selectively expanding and contracting respective sections, only the nozzle hole 34 formed in the section is expanded and contracted, and the shape (an injection angle) of spray is varied and a plurality of sprays are collided with each other. The nozzle hole plate 31 can be formed as a heat generating element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine (engine), and more particularly, to a fuel injection rate within the injection period, which is arbitrarily determined according to the use state of the internal combustion engine, the load, the number of revolutions, and the like. The present invention relates to a fuel injection device including a fuel injection valve that can be changed to a fuel injection valve.

[0002]

2. Description of the Related Art In a general internal combustion engine, as an example of a system for controlling the timing and period of fuel injection in accordance with the operating condition thereof, the appearance is substantially similar to that of the embodiment of the present invention shown in FIG. A fuel injection control system having a configuration is used. (For example, see Japanese Utility Model Laid-Open Publication No. 1-11367.) The fuel injection control system shown in FIG. 1 performs intake air based on signals output from a crank angle sensor 101, an intake pipe pressure sensor 102, and an intake air temperature sensor 103. The air amount is calculated, the basic injection amount that matches the ideal air-fuel ratio is obtained, and the cooling water temperature sensor 104 and the accelerator opening sensor 1 are calculated.
05, by adding a correction based on a signal output from the residual oxygen concentration sensor 106 or the like, calculating the injection period from the injection rate of the injection valve measured in advance, energizing the fuel injection valve 107 with the injection signal as a voltage pulse, Control the injection volume.

[0003] Since the intake air amount is small at light load and large at high load, the conventional fuel injection control system controls the injection amount by changing the injection period according to the magnitude of the load. I have. In any case, at the upper limit, it is necessary to secure the injection amount at the time of high load at the maximum allowable engine speed, and at the lower limit, it is necessary to adjust the fuel injection amount over a wide range (dynamic range) up to the injection amount at idling. is there.

[0004]

In the above-described conventional apparatus, the injection timing is set to a timing in which the intake air flow velocity is as fast as possible, even though it has a structure substantially similar to that of the embodiment (described later) of the present invention. Even if it is set in accordance with the above, and the fuel mixture is to be formed well, the injection period becomes long at high load, so that the fuel is unavoidably injected even during the period of low intake flow rate. Further, at the time of high rotation and high load in which the injection amount increases, it is not possible to inject the entire required amount of fuel only during the intake period (the period during which the intake valve is open). It is necessary to inject fuel even during the closing of the previous intake valve (exhaust period), thereby increasing the amount of fuel adhering to the intake pipe wall and evaporating fuel due to the fuel adhering to the intake valve. Since the heat cannot be used for cooling the intake air, there is a problem that effects such as improvement of the charging efficiency and the power performance cannot be sufficiently obtained.

The present invention has been made to solve the above-mentioned problems in the prior art.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an internal combustion engine provided with a fuel injection valve having a variable injection rate during an injection period. At a high load, the injection rate is increased in accordance with the magnitude of the load, so that fuel can be injected only at a time when the intake flow velocity is high under all operating conditions of the engine, and a good air-fuel mixture is injected into the cylinder. It is intended to provide a fuel injection control device for an internal combustion engine, which can be formed as follows.

[0007] As a more specific solution, the present invention provides a fuel injection device for an internal combustion engine as set forth in the appended claims.

According to the first aspect of the present invention, as a characteristic, an electric control command is given from the control means to the fuel injection valve (injector) to change the area or the number of the injection holes, so that the injection period can be reduced. , An injection rate varying means for arbitrarily changing the fuel injection rate per unit time.

Therefore, for example, the injection rate is controlled so that the injection period when the intake air amount is small and the injection period when the intake air amount is large, and the fuel amount corresponding to the intake air amount is injected during the period when the intake air flow speed is high. Thus, a fuel-air mixture can be formed, and fuel adhesion to the wall of the intake pipe can be controlled.

According to the second aspect of the invention, the injection hole plate of the piezoelectric element is attached to the injection port at the tip of the fuel injection valve as the injection rate variable means. By applying a high voltage between the two surfaces of the hole plate and expanding the hole plate, the hole diameter of the injection holes formed in the injection hole plate is reduced, and the injection rate is reduced. At the time of a high load at which a high injection rate is desired, the injection hole plate is contracted by reducing the electric charge applied to the injection hole plate, the hole diameter is increased, and the injection rate is increased. The energization for applying the voltage in this case may be performed in synchronization with the injection timing,
The power may be supplied at all times, and the power may be stopped and discharged only when necessary.

According to the third aspect of the present invention, as the injection rate variable means, the injection hole plate of the heating element is attached to the tip of the injection port of the fuel injection valve, and for example, heat is generated and expanded by energizing at a light load at which a low injection rate is desired. By doing so, the diameter of the injection hole formed in the injection hole plate is reduced, and the injection rate is reduced. In this case, the nozzle plate is heated, so that the fuel spray passing through the nozzle hole is heated, and an additional effect is obtained that the vaporization is promoted. At the time of a high load at which a high injection rate is desired, the amount of electricity is reduced, the injection hole plate is contracted by the cooling effect of the intake air flow and the injected fuel, and the injection hole diameter is increased to increase the injection rate.

According to the fourth aspect of the present invention, the injection hole plate is divided into a plurality of independent portions, such as the outside and the inside of the injection hole plate, or the first half and the other half, and only one portion is selected. Shrink and expand. For example, when divided into a central portion and an outer peripheral portion, the injection hole provided in the central portion has a fixed diameter over the entire area, and the injection hole provided in the outer peripheral portion has a variable diameter, so that when the intake air amount is small. Reduces the injection rate during the injection period by closing the injection hole in the outer peripheral portion, and at the same time, reduces the spray angle, thereby reducing the adhesion of the fuel spray to the intake pipe wall surface. When the intake air amount is large, all the injection holes are opened to increase the injection rate, and the spray is guided into the cylinder by a strong intake flow.

According to the fifth aspect of the present invention, the injection holes are configured such that the fuel spray injected from one of the injection holes of the injection hole plate collides with the fuel spray injected from the other one of the injection holes,
At the time of light load at which a low injection rate is desired, the injection rate is reduced by closing a part of the injection holes. At the time of a high load at which a high injection rate is desired, all injection holes are opened to increase the injection rate and at the same time collide the injected sprays to promote atomization of the sprays and form a good air-fuel mixture.

According to the present invention, for example, in a two-way injection valve for an engine having two intake valves per cylinder, one of the injection holes corresponding to the two intake ports is closed to reduce the injection rate. At the same time, stratification is performed by sucking fuel into the cylinder only from the intake port corresponding to the other injection hole and the intake valve. Further, when all the injection holes are opened at the time of high load and fuel is sucked also from the intake port and the intake valve of the faster intake air flow, a good mixture can be formed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, the present invention is embodied in a four-cylinder gasoline injection type four-stroke engine. The main components of the embodiment are a fuel injection valve that injects fuel into an intake passage of each cylinder, Each cylinder has two intake valves and two exhaust valves, and has an electronic control unit (hereinafter referred to as an ECU) for adjusting the injection amount of the fuel injection valve. In order to make the injection rate variable during the injection period, a special injection hole plate is provided at the tip of the fuel injection valve.

FIG. 1 is a system configuration diagram schematically showing a cross section of an engine and an engine control system in this embodiment. As shown in FIG. 1, a cylindrical cylinder 2a is formed in a cylinder block 2 of an engine 1, and a piston 3 is arranged in the cylinder 2a so as to be able to reciprocate in the vertical direction in the figure. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. An intake port 8 and an exhaust port 9 communicating with the combustion chamber 6 above the piston 3 are formed in the cylinder head 7. Like the fuel injection valve 107 in the related art, the intake port 8 has an electromagnetically driven type. Fuel injection valve (injector)
10 are provided. The injector 10 is an ECU 50
The fuel is injected into the intake port 8 based on the injection control signal from the engine.

Further, the cylinder head 7 is provided with two intake valves 11 and two exhaust valves 12, respectively. The opening and closing operations of these valves 11, 12 allow the combustion chamber 6 and the ports 8, 9 to communicate with each other. The space is communicated or closed. The combustion chamber 6 is closed when both the intake valve 11 and the exhaust valve 12 are closed.
The two intake valves 11 and two exhaust valves 1
The intake port 8 and the exhaust port 9 correspond to branch passages, respectively. In the case of the intake port 8, the intake port 8 and the exhaust port 9 are branched into two at the downstream side of the injector 10. Further, an ignition plug 13 that discharges based on an ignition control signal output from the ECU 50 is provided in the combustion chamber 6. In addition,
Reference numeral 14 denotes a starter.

The ECU 50 mainly includes a CPU for executing various control programs and a well-known microcomputer having a memory for storing control data, maps, and the like. Crank angle and rotation speed signal (Ne), the intake pipe pressure signal (PM) detected by the intake pipe pressure sensor 102, the intake temperature signal (Tin) detected by the intake air temperature sensor 103, and the cooling water temperature sensor 10.
4, the accelerator opening signal Ac detected by the accelerator opening sensor 105, the oxygen concentration signal O ₂ in the exhaust gas detected by the residual oxygen concentration sensor 106 provided in the exhaust passage, and the like. I do. Then, based on these input signals, the injector 10
Control of fuel injection and ignition control by the spark plug 13 are executed.

Further, in the embodiment of the present invention, E
The CU 50 corresponds to a valve operation control unit for outputting a control command to the injection rate variable mechanism 20 shown in FIG. 3 and the like, and is operated by a solenoid 39 based on a part or all of the various signals and other data. In addition to controlling the start and stop of the injection by driving the needle 35, the injection rate variable mechanism 2
The injection hole diameter or the number of injection holes at 0 is controlled.

Next, the structure of the injection rate variable mechanism 20 and its peripheral parts will be described with reference to FIGS. The nozzle 37 at the tip of the injector 30 (specific embodiment of the injector 10 described above) shown in FIG. 3 has a nozzle hole in a form to close a nozzle port 36 opened and closed by a needle 35 as shown in an enlarged view in FIG. A plate 31 is attached, and a small injection hole 3 is provided at a position corresponding to the injection hole 36 on the injection hole pool 31.
4 are provided in a predetermined number. In addition, injection hole plate 3
The electrodes 32a, 32b for controlling the diameter of the injection hole or the number of the injection holes, and the electrodes 32a, 32b
An insulator 33 that covers the upper and lower sides of b and the outer periphery of the injection hole plate 31 is provided.

A predetermined voltage is applied to the electrodes 32a and 32b via a driver 51 based on a control command from the ECU 50. 38 is the lead wire. On the other hand, the insulator 33 supports the injection hole plate 31 at the tip of the nozzle 37, serves as an electrical and fluid seal, and also serves to restrict the outer periphery of the injection hole plate 31. That is, the insulator 33 is formed by the injection hole plate 31 having the electrodes 32a and 32b.
When the voltage is applied to the plate, the expansion in the radial direction is suppressed when expanding in the radial direction, so that the expansion is concentrated on the central portion of the injection hole plate 31 and the injection holes 34 are reduced. In addition, since a large reaction force is generated in the insulator 33 by the action of fitting the injection hole plate 31 to the backlash, the outer peripheral portion may be reinforced with metal or the like.

In the above embodiment, when a piezoelectric element such as ceramic or quartz is used as the material of the injection hole pool 31 as shown in FIG. 5, the voltage applied between the upper and lower electrodes 32a and 32b by the driver 51 is reduced. 6A and 6B in each cycle.
The effective diameter of the injection hole per unit time during the injection period is set such that the effective diameter of the injection hole is small when the load is light, and some of the injection holes are closed when the load is light. That is, the injection rate can be varied, and control can be performed to change the injection hole diameter or the actual number of injection holes simultaneously with or before injection.

As an embodiment other than the one using a piezoelectric element, a heating element made of a ceramic, an alloy, or the like is used for the injection hole plate 31 so that the thermal expansion corresponding to the supplied electric energy is reduced. And control to change the diameter of the injection hole or the number of injection holes can be performed. Further, the injection hole 3 due to the expansion and contraction of the injection hole plate 31.
In addition to the expansion and contraction of the opening area of the nozzle hole 4, as can be understood from FIG. 4, as the nozzle hole plate 31 expands and contracts in the radial direction, a part of the nozzle hole 34 is effectively covered by the insulator 33. The opening area and the numerical aperture of the injection hole 34 may be changed.

In these embodiments, not only can the injection rate be made variable, but also the control for simultaneously changing the spray form depending on the arrangement and shape of the injection holes 34 in the injection hole plate 31 can be performed. Is also possible.

For example, as shown in FIG. 7, the central portion 31a and the outer peripheral portion 31b of the injection hole plate 31 are configured to be separately controllable.
The injection hole 34b of only 1b can be expanded and contracted according to the magnitude of the load. Of course, depending on the conditions, the central part 3
The enlargement / reduction of only the injection hole 31a of 1a or the simultaneous enlargement / reduction of both are possible.

In this example, in a light load state where the injection rate is low, a voltage is applied between the upper and lower electrodes of the outer peripheral portion 31b of the injection hole plate 31 to expand the outer injection hole plate 31b in the radial direction. And compressed vertically.
As shown in (a), the diameter of the injection hole 34b of only the outer peripheral portion 31b is reduced, or the number of the injection holes is reduced by setting the injection hole 34b to a fully closed state, so that the outer peripheral portion 31 of the injection hole plate is reduced.
By narrowing the effective injection hole to the injection hole 34a of the central portion 31a by reducing the injection rate of b, the spray angle is made narrow.

As shown in FIGS. 8B and 8D,
When the load is high, the injection hole 34a in the central portion 31a and the outer peripheral portion 31b
When atomization is performed by colliding the sprays respectively injected from the injection holes 34b of the nozzle holes 34b, the injection holes 3 that are formed in an oblique direction are used.
Only 4b is contracted and expanded. Specifically, similarly to the above-described embodiment, at the time of a low injection rate with a light load, a voltage is applied to an electrode (not shown) of the outer peripheral portion 31b of the injection hole plate, as shown in FIGS. 8 (a) and 8 (c). In addition, the injection rate is reduced by reducing or closing the injection hole 34b in the outer peripheral portion, and the spray angle is made narrow by preventing collision with the spray injected from the injection hole 34a in the central portion. At the time of high load and high injection rate, the charge applied to the electrode of the outer peripheral portion 31 of the injection hole plate is released,
At the same time as improving the injection rate, the inner and outer injection holes 34a, 34
The fuel spray injected from b is caused to collide with each other to promote atomization.

Further, as shown in FIG.
1 is divided into two parts 31c and 31d on the left and right sides, and the injection directions of the injection holes 34c and 34d are made different from each other so as to perform injection in two directions such as two intake ports. Only the hole 34c can be expanded and contracted so that the fuel is injected from the injection hole 34d only to one intake port (for example, a swirl port) at a low injection rate with a light load. Thereby, at the same time as reducing the injection rate, it is also possible to cause the fuel to be sucked in from only one of the intake valves and perform stratified combustion in the combustion chamber 6.

Further, the fuel injection device of the present invention may be applied to an in-cylinder direct fuel injection type engine. In this case, the fuel injection device of the present invention has a spray form such as an injection rate and an injection direction. As a variable mechanism, an air-fuel mixture formation promoting effect is obtained.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram schematically showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining a problem of the related art.

FIG. 3 is a vertical sectional front view illustrating the fuel injection valve of the present invention.

FIG. 4 is an enlarged view of a main part of FIG. 3;

FIG. 5 is a perspective view showing a part of a main part shown in FIG.

6 (a) and 6 (b) are cross-sectional views of the part shown in FIG. 5 in a case where operating conditions are different.

FIG. 7 shows another embodiment of the injection hole plate.
(A) And (b) is a perspective view which shows the case where operating conditions differ.

FIG. 8 shows another embodiment of an injection hole plate.
(A), (c), (b), and (d) are a perspective view and a sectional view showing a case where operating conditions are different.

FIG. 9 shows another embodiment of the injection hole plate.
(A) And (b) is a perspective view which shows the case where operating conditions differ.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine (engine) 8 ... Intake port 10, 30, 107 ... Fuel injection valve (Injector) 20 ... Injection rate variable mechanism 31, 31a, 31b, 31c, 31d ... Injection hole plate 32a, 32b ... Electrode 33 ... Insulation Body 34, 34a, 34b, 34c, 34d ... Injection hole 36 ... Injection hole of nozzle

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 51/06 F02M 51/06 Q 51/08 51/08 J 53/04 53/04 N 69/00 360 69 69/00 360G 69/04 69 / 04 L (72) Inventor: Kimitaka Saito 14 Iwatani, Shimowasakumachi, Nishio, Aichi Prefecture Inside the Japan Automobile Parts Research Institute (72) Inventor Tokio Obama 14th, Iwatani, Shimowasukamachi, Nishio, Aichi Prefecture Japan Automobile Co., Ltd. (72) Inventor Yukio Sawada 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. Denso Corporation

Claims (6)

[Claims] 1. A fuel injection device for an internal combustion engine having a fuel injection valve whose valve opening operation for starting fuel injection and valve closing operation for stopping injection are electrically controlled by valve operation control means. In the internal combustion engine, there is provided an injection rate variable means for arbitrarily changing an injection rate which is a fuel injection amount per unit time during an injection period from opening to closing of the fuel injection valve. Fuel injector. 2. A fuel injection device for an internal combustion engine according to claim 1, wherein a piezoelectric element is used as said injection rate variable means in an injection hole plate attached to an injection port of said fuel injection valve. 3. The fuel injection device for an internal combustion engine according to claim 1, wherein a heating element is used for an injection hole plate attached to an injection port of the fuel injection valve as the injection rate variable means. 4. The injection hole plate used in the injection rate variable means is composed of a plurality of portions, and the injection holes formed in each of the portions are controlled so as to expand and contract independently for each portion. The fuel injection device for an internal combustion engine according to claim 2 or 3, wherein 5. The injection rate variable means increases the injection rate of the fuel injection valve during an injection period when the internal combustion engine is under a high load, and simultaneously collides fuel injected from a plurality of injection holes with each other. The fuel injection device for an internal combustion engine according to any one of claims 1 to 4, wherein atomization is promoted by causing the atomization. 6. A multi-directional injection valve provided for each cylinder of an internal combustion engine having a plurality of intake valves per cylinder and a plurality of intake ports corresponding to the plurality of intake valves, wherein the injection rate variable means includes the plurality of intake valves. The fuel injection device for an internal combustion engine according to any one of claims 1 to 5, wherein fuel injection to a part of the intake port is stopped to reduce the injection rate.