JP2018105209A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device capable of injecting fuel with different fuel pressure.SOLUTION: A fuel injection device 1 includes: a first common rail and a second common rail having first fuel and second fuel with different pressures; and an injector 10 for injecting the first fuel and the second fuel supplied from the first common rail and the second common rail to a combustion chamber. The injector 10 includes: a nozzle body 100; a first nozzle hole 110 formed at a tip of the nozzle body 100; a first fuel introduction passage 11 for introducing the first fuel to the first nozzle hole 110; a first needle 12 accommodated in the nozzle body 100 to open/close the first nozzle hole 110; a second nozzle hole 210 formed at a tip of the first needle 12; a second fuel introduction passage 21 for introducing the second fuel to the second nozzle hole 210; and a second needle 22 accommodated in the first needle 12 to open/close the second nozzle hole 210.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel injection device including a common rail and an injector.

  Conventionally, as a fuel injection device for a diesel engine, a so-called common rail fuel injection device in which high-pressure fuel (light oil) sent from a fuel pump is stored in a common rail, supplied to the injector from the common rail, and directly injected from the injector into the combustion chamber It has been known. By adopting a common rail, a stable fuel pressure can be maintained and fuel can be injected at a high pressure. By high pressure injection, fuel can be refined and mixing with air can be promoted, or the air-fuel mixture can be distributed in the combustion chamber. In general, an injector includes a nozzle body in which an injection hole is formed at a tip portion, and a needle that is accommodated in the nozzle body and opens and closes the injection hole.

  As an injector of a fuel injection device, for example, in Patent Documents 1 and 2, a double needle in which a first needle (large needle valve) and a second needle (small needle valve) are coaxially housed inside a nozzle body. A fuel injection valve (fuel valve) including a needle valve having a structure is disclosed. In the fuel injection valve of Patent Document 1, only the second needle is opened, and the supplied fuel is injected from the second injection hole through the first injection hole, whereby a spray with a high penetration force can be formed. Is opened, and fuel is injected from the first injection hole to form a spray with a low penetration force. In the fuel valve of Patent Document 2, different types of pilot fuel and main fuel are supplied, the small needle valve is opened, the pilot fuel is injected from the pilot fuel nozzle through the common nozzle, and the large needle valve is opened for common use. Main fuel is injected from the nozzle.

JP 2011-220132 A Japanese Utility Model Publication No. 2-43457

  In a fuel injection device for a diesel engine, multistage injection is performed in which a plurality of fuel injections are performed in one combustion cycle by electronic control. Multi-stage injection includes pilot injection, pre-injection, main injection, after-injection, and post-injection in order. Among these, main injection is fuel injection for generating main combustion in the combustion chamber and generating engine torque. The post-injection performed after the main injection is not intended to burn the fuel in the combustion chamber, but to send the fuel together with the exhaust gas to the exhaust pipe when regenerating the DPF (Diesel Particulate Filter). The timing of post-injection is often slower than the crank angle (° CA) after top dead center (ATDC) 90 ° CA. Therefore, in post-injection, fuel is injected at the position where the piston is lowered, so that fuel adheres to the inner wall surface of the cylinder, and oil dilution may occur in which part of the fuel is mixed into the engine oil. When the fuel pressure of the fuel supplied to the injector is high, the injection pressure of the fuel injected from the injector into the combustion chamber is also high, the amount of fuel adhering to the inner wall surface of the cylinder increases, and the oil dilution by the fuel is promoted.

  Therefore, in order to reduce the amount of fuel adhering to the cylinder inner wall surface by post injection, it is conceivable to lower the fuel pressure and lower the injection pressure, but the fuel pressure cannot be changed in one combustion cycle. Therefore, the injection pressure can only be set to one level. In that case, since the injection pressure at the time of burning the fuel in the combustion chamber is also lowered, there arises a problem that the fuel efficiency is lowered and the engine torque is lowered and the fuel consumption is deteriorated.

  One of the objects of the present invention is to provide a fuel injection device capable of injecting fuels having different fuel pressures.

A fuel injection device according to an aspect of the present invention includes:
A first common rail and a second common rail for storing a first fuel and a second fuel having different fuel pressures;
An injector for injecting the first fuel and the second fuel supplied from the first common rail and the second common rail into a combustion chamber,
The injector is
A nozzle body;
A first injection hole formed at the tip of the nozzle body;
A first fuel introduction path for introducing the first fuel into the first injection hole;
A first needle which is accommodated in the nozzle body so as to be movable in the axial direction and opens and closes the first injection hole;
A second injection hole formed at the tip of the first needle and formed to be able to communicate with the first injection hole;
A second fuel introduction path for introducing the second fuel into the second injection hole;
And a second needle that is slidably accommodated in the first needle and opens and closes the second injection hole.

  The fuel injection device can individually inject the first fuel and the second fuel having different fuel pressures from one injector into the combustion chamber, and can control the injection pressure when injecting the fuel. For example, when the first fuel is at a high pressure and the second fuel is at a low pressure, the injection pressure can be increased by opening the first injection hole with the first needle and injecting the high-pressure first fuel from the first injection hole. High-pressure fuel injection is possible. On the other hand, by opening the second injection hole with the second needle and injecting the low-pressure second fuel from the second injection hole through the first injection hole, the injection pressure can be lowered and low-pressure fuel injection is possible. Conversely, when the first fuel is at a low pressure and the second fuel is at a high pressure, similarly, by switching the fuel to be injected by opening and closing the first injection hole or the second injection hole with the first needle or the second needle, Fuel injection with different injection pressures is possible. That is, according to the fuel injection device, two fuels having different fuel pressures can be switched and injected from a single injector, and the injection pressure can be controlled as necessary. For example, during main injection, it is possible to increase combustion efficiency by high-pressure fuel injection, and during post-injection, it is possible to reduce fuel adhesion to the cylinder inner wall surface by low-pressure fuel injection, without deteriorating combustion efficiency, It is possible to suppress oil dilution.

It is the schematic which shows the structure of the fuel-injection apparatus which concerns on Embodiment 1. FIG. It is a schematic sectional drawing which shows the structure of the injector with which the fuel injection apparatus which concerns on Embodiment 1 is equipped. It is a schematic sectional drawing which shows the state which the 1st needle of the injector shown in FIG. 2 opened. It is a schematic sectional drawing which shows the state which the 2nd needle of the injector shown in FIG. 2 opened.

  A specific example of a fuel injection device according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals in the figure indicate the same names.

[Embodiment 1]
With reference to FIGS. 1-4, the fuel-injection apparatus 1 which concerns on Embodiment 1 is demonstrated. The fuel injection device 1 is used in a diesel engine, and as shown in FIG. 1, a first common rail 51 and a second common rail 52 that store a first fuel and a second fuel having different fuel pressures, and a first common rail 51 and a second common rail. And an injector 10 to which a first fuel and a second fuel are supplied from a common rail 52. As shown in FIG. 2, the injector 10 includes a nozzle body 100, a first needle 12 that is accommodated in the nozzle body 100, and opens and closes a first injection hole 110 formed at the tip of the nozzle body 100, The second needle 22 is accommodated in the first needle 12 and opens and closes the second injection hole 210 formed at the tip of the first needle 12. First, the overall configuration of the fuel injection device 1 will be described with reference to FIG. 1, and then the configuration of the injector 10 will be described in detail with reference mainly to FIGS.

<First common rail and second common rail>
As shown in FIG. 1, the first common rail 51 and the second common rail 52 include fuel pumps 61 and 62, respectively, and store the fuel sent by the fuel pumps 61 and 62. The fuel pumps 61 and 62 set the fuel in the fuel tank 70 to a predetermined pressure and pump it to the first common rail 51 and the second common rail 52, respectively. In this example, the pressure applied to the fuel in each of the fuel pumps 61 and 62 is different, and the first fuel stored in the first common rail 51 and the second fuel stored in the second common rail 52 are different in fuel pressure. The fuel pressure of the second fuel of the second common rail 52 is set lower than that of the first fuel of the common rail 51 (first fuel: high pressure, second fuel: low pressure).

  In this example, the case where the fuel pressures are made different by the two fuel pumps 61 and 62 and the fuels having different fuel pressures are respectively sent from the fuel pumps 61 and 62 to the first common rail 51 and the second common rail 52 has been described. There may be one pump. In that case, high-pressure fuel is sent to both the first common rail 51 and the second common rail 52 by one fuel pump. Then, for example, by providing a pressure adjusting valve for reducing the fuel pressure on the second common rail 52 on the side where the fuel pressure is reduced, the fuel pressure of the second common rail 52 is made lower than that of the first common rail 51. It is done.

<Injector>
The injector 10 is provided in each cylinder of an engine (not shown), and is attached so that the tip of the nozzle body 100 is located in the combustion chamber, and injects fuel (in-cylinder injection) into the combustion chamber. As shown in FIG. 1, the first fuel and the second fuel stored in the first common rail 51 and the second common rail 52 are supplied to the injector 10 from the first common rail 51 and the second common rail 52. As shown in FIG. 2, the injector 10 includes a nozzle body 100, a first injection hole 110 and a second injection hole 210, a first fuel introduction path 11 and a second fuel introduction path 21, a first needle 12 and a first injection hole. 2 needles 22.

(First injection hole / First fuel introduction path)
As shown in FIG. 2, the first injection hole 110 is a hole that is formed at the tip of the nozzle body 100 and injects the first fuel. The number of the 1st injection holes 110 should just be at least one, and there may be two or more. The nozzle body 100 is provided with a first fuel introduction path 11 for introducing the first fuel supplied from the first common rail 51 shown in FIG. 1 into the first injection hole 110. In this example, an inlet 111 of the first fuel introduction path 11 is provided at the rear end of the nozzle body 100, and the first common rail 51 is connected to the inlet 111. A first fuel chamber 112 communicating with the first injection hole 110 is formed between the tip of the nozzle body 100 and the tip of the first needle 12, and the first fuel introduction path 11 is formed in the first fuel chamber 112. The first fuel is introduced into the first fuel chamber 112.

(First needle)
As shown in FIG. 2, the first needle 12 is a valve that is accommodated in the nozzle body 100 so as to be movable in the axial direction, and opens and closes the first injection hole 110. In this example, the first needle 12 is urged toward the distal end side (downward) of the nozzle body 100 by a spring 13, and the first control chamber 14 and the actuator that control the operation of the first needle 12 within the nozzle body 100. 15 are provided. The first control chamber 14 is formed on the rear end side of the first needle 12, and the rear end surface of the first needle 12 faces the first control chamber 14. An inlet orifice 141 and an outlet orifice 142 are provided in the first control chamber 14, and the first fuel is introduced from the first fuel introduction path 11 through the inlet orifice 141. A check valve (not shown) may be provided on the inlet orifice 141 side so that the first fuel in the first control chamber 14 does not flow back into the first fuel introduction path 11. The actuator 15 drives the valve 151 to open and close the outlet orifice 142 of the first control chamber 14. The actuator 15 is electrically controlled by an electronic control unit (ECU) 80 shown in FIG. 1 and is operated by an electric signal from the ECU 80. When energization of the actuator 15 is OFF, the valve 151 is pushed down and the outlet orifice 142 is closed. On the other hand, when the energization of the actuator 15 is ON, the valve 151 is raised and the outlet orifice 142 is opened, and the first fuel in the first control chamber 14 is discharged to the first fuel discharge path 16 through the outlet orifice 142. As the actuator 15, a solenoid or a piezo element can be used. The operation of the first needle 12 when injecting the first fuel will be described later.

(Second injection hole / second fuel introduction path)
As shown in FIG. 2, the second injection hole 210 is formed at the tip of the first needle 12 and is formed so as to communicate with the first injection hole 110, and is a hole for injecting the second fuel. The second injection holes 210 are provided at positions facing the first injection holes 110. When there are a plurality of first injection holes 110, the number of the second injection holes 210 is the same as or less than that of the first injection holes 110. May be. The nozzle body 100 is provided with a second fuel introduction path 21 for introducing the second fuel supplied from the second common rail 52 shown in FIG. 1 into the second injection hole 210. In this example, an inlet 211 of the second fuel introduction path 21 is provided at the rear end of the nozzle body 100, and the second common rail 52 is connected to the inlet 211. In addition, a second fuel chamber 212 communicating with the second injection hole 210 is formed between the distal end portion of the first needle 12 and the distal end portion of the second needle 22, and the through hole formed in the first needle 12 is interposed. The second fuel introduction path 21 is connected to the second fuel chamber 212, and the second fuel is introduced into the second fuel chamber 212.

(Second needle)
As shown in FIG. 2, the second needle 22 is a valve that is accommodated in the first needle 12 so as to be movable in the axial direction, and opens and closes the second injection hole 210. The first needle 12 and the second needle 22 are disposed on a concentric shaft. In this example, the second needle 22 is biased toward the distal end side (downward) of the first needle 12 by a spring 23, and a second control chamber 24 that controls the operation of the second needle 22 in the nozzle body 100, An actuator 25 is provided. The second control chamber 24 is formed on the rear end side of the second needle 22, and the rear end surface of the second needle 22 faces the second control chamber 24. In this example, the second control chamber 24 is located on the rear end side of the first control chamber 14, and the rear end portion of the second needle 22 extends through the first control chamber 14 to the second control chamber 24. An inlet orifice 241 and an outlet orifice 242 are provided in the second control chamber 24, and the second fuel is introduced from the second fuel introduction path 21 through the inlet orifice 241. A check valve (not shown) may be provided on the inlet orifice 241 side so that the second fuel in the second control chamber 24 does not flow back into the second fuel introduction path 21. The actuator 25 drives the valve 251 to open and close the outlet orifice 242 of the second control chamber 24. The actuator 25 is electrically controlled by the ECU 80 shown in FIG. 1 and is operated by an electric signal from the ECU 80. When the actuator 25 is turned off, the valve 251 is pushed down and the outlet orifice 242 is closed. On the other hand, when the energization of the actuator 25 is ON, the valve 251 is pulled up, the outlet orifice 242 is opened, and the second fuel in the second control chamber 24 is discharged to the second fuel discharge passage 26 through the outlet orifice 242. As the actuator 25, a solenoid or a piezo element can be used. The operation of the second needle 22 when injecting the second fuel will be described later.

{Operation of the first needle and the second needle}
The operation of the first needle 12 will be described with reference to FIGS. The first fuel supplied from the first common rail 51 is introduced into the first fuel chamber 112 and the first control chamber 14 through the first fuel introduction path 11. As shown in FIG. 2, in a state where the actuator 15 is turned off (initial state), the pressure of the first fuel chamber 112 that pushes up the first needle 12 due to the fuel pressure and the first needle 12 are pushed down. The pressure in the first control chamber 14 is the same. Therefore, since the first needle 12 is pressed against the tip end side of the nozzle body 100 by the force in the downward direction by the spring 13, the first injection hole 110 is closed by the first needle 12, and the first fuel is discharged from the first injection hole 110. Is not jetted. On the other hand, as shown in FIG. 3, when the energization of the actuator 15 is turned ON, the actuator 15 is actuated to lift the valve 151, the first fuel in the first control chamber 14 flows out through the outlet orifice 142, The pressure in the first control chamber 14 decreases. Therefore, the force in the push-down direction due to the pressure in the first control chamber 14 is smaller than the force in the push-up direction due to the pressure in the first fuel chamber 112. When the force in the push-up direction becomes larger than the force in the push-down direction acting on the first needle 12, the first needle 12 is pushed up to open the first injection hole 110, and the first fuel is discharged from the first injection hole 110. Be injected.

  The operation of the second needle 22 will be described with reference to FIGS. The second fuel supplied from the second common rail 52 is introduced into the second fuel chamber 212 and the second control chamber 24 through the second fuel introduction path 21. As shown in FIG. 2, in a state where the actuator 15 is turned off (initial state), the pressure of the second fuel chamber 212 that tries to push up the second needle 22 by the fuel pressure and the second needle 22 are pushed down. The pressure in the second control chamber 24 is the same. For this reason, the second needle 22 is pressed against the distal end side of the first needle 12 by the force in the pressing-down direction by the spring 23, so that the second injection hole 210 is closed by the second needle 22 and the second injection hole 210 passes through the second injection hole 210. Fuel is not injected. On the other hand, as shown in FIG. 4, when the energization of the actuator 25 is turned ON, the actuator 25 is operated to lift the valve 251, and the second fuel in the second control chamber 24 flows out through the outlet orifice 242. The pressure in the second control chamber 24 decreases. Therefore, the force in the push-down direction due to the pressure in the second control chamber 24 is smaller than the force in the push-up direction due to the pressure in the second fuel chamber 212. When the force in the push-up direction becomes larger than the force in the push-down direction acting on the second needle 22, the second needle 22 is pushed up to open the second injection hole 210 and the second injection hole 210 to the first injection hole. The second fuel is injected through 110.

  Since the first needle 12 and the second needle 22 can operate independently, and the opening and closing of the first injection hole 110 and the second injection hole 210 can be individually controlled, the first fuel and the second fuel are supplied. Can be injected individually.

  Note that the first needle 12 also receives a force in the push-down direction that acts on the second needle 22. In this example, when injecting the first fuel, only the actuator 15 is operated, and the second needle 22 is pressed against the distal end side of the first needle 12 by the force in the pushing-up direction due to the pressure in the first fuel chamber 112. In this state, the second needle 22 is pushed up together with the first needle 12. Of course, both the actuator 15 and the actuator 25 are operated to control the first needle 12 and the second needle 22 to be pushed up at the same time while keeping the second needle 22 pressed against the distal end side of the first needle 12. May be. Further, when injecting the second fuel, only the actuator 25 is operated and only the second needle 22 is pushed up, and the first needle 12 is controlled to be kept pressed against the distal end side of the nozzle body 100.

[Function and effect]
The fuel injection device 1 according to Embodiment 1 described above has the following effects.

  The first fuel and the second fuel having different fuel pressures can be individually injected from one injector 10 into the combustion chamber, and fuel injection having different injection pressures is possible. As in this example, when the first fuel is at a high pressure and the second fuel is at a low pressure, when high-pressure fuel injection is performed, the first injection hole 110 is opened by the first needle 12, and the high pressure from the first injection hole 110. The first fuel is injected. On the other hand, when low-pressure fuel injection is performed, the second injection hole 210 is opened by the second needle 22, and low-pressure second fuel is injected from the second injection hole 210 through the first injection hole 110. Therefore, the injection pressure at the time of fuel injection can be controlled as necessary. It is possible to reduce oil adhesion and suppress oil dilution.

  In addition, by varying the injection pressure according to the load state of the engine, or by varying the injection pressure of the main injection and each of the other injections (eg, pilot, pre, after injection, etc.) in multi-stage injection, Improvement in combustion efficiency can be expected, such as enabling injection control for more effectively using the air in the combustion chamber.

  The present invention is not limited to these exemplifications, is shown by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. For example, in the first embodiment described above, the first fuel is set to high pressure and the second fuel is set to low pressure. However, the first fuel can be set to low pressure and the second fuel can be set to high pressure.

  The fuel injection device of the present invention can be suitably used for an automobile diesel engine.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 10 Injector 100 Nozzle body 110 1st injection hole 11 1st fuel introduction path 111 Introduction port 112 1st fuel chamber 12 1st needle 13 Spring 14 1st control chamber 141 Inlet orifice 142 Outlet orifice 15 Actuator 151 Valve 16 First fuel discharge passage 210 Second injection hole 21 Second fuel introduction passage 211 Inlet 212 Second fuel chamber 22 Second needle 23 Spring 24 Second control chamber 241 Inlet orifice 242 Outlet orifice 25 Actuator 251 Valve 26 Second fuel discharge Road 51 First common rail 52 Second common rail 61, 62 Fuel pump 70 Fuel tank 80 Electronic control unit (ECU)

Claims (1)

A first common rail and a second common rail for storing a first fuel and a second fuel having different fuel pressures;
An injector for injecting the first fuel and the second fuel supplied from the first common rail and the second common rail into a combustion chamber,
The injector is
A nozzle body;
A first injection hole formed at the tip of the nozzle body;
A first fuel introduction path for introducing the first fuel into the first injection hole;
A first needle which is accommodated in the nozzle body so as to be movable in the axial direction and opens and closes the first injection hole;
A second injection hole formed at the tip of the first needle and formed to be able to communicate with the first injection hole;
A second fuel introduction path for introducing the second fuel into the second injection hole;
A fuel injection device comprising: a second needle that is slidably accommodated in the first needle and opens and closes the second injection hole.

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