JP2010038047A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device using high-cetane fuel as well as low-cetane fuel as fuel, suppressing hydrocarbon emission in comparison with the use of only the low-cetane fuel, and improving fuel consumption. <P>SOLUTION: A fuel injection valve 10 provided to the fuel injection valve 1 has a first seal 15 provided at the end of a nozzle body 11, and a second seal 16 provided on a side nearer to a base end than the first seal 15. A first fuel supply portion 17 is formed between the first seal 15 and the second seal 16. A second fuel supply portion 18 is formed on the side nearer to the base end than the second seal 16. Gas to liquid (GTL) fuel is supplied to the first fuel supply portion 17, and main fuel is supplied to the second fuel supply portion 18. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection device.

Recently, from the viewpoint of energy security, studies and development of alternative fuels that are not derived from crude oil have been actively conducted.
For example, a fuel called Gas To Liquid (GTL) fuel has been developed. GTL fuel is a liquid fuel synthesized from natural gas, and has a feature of having a straight chain saturated hydrocarbon as a main component and a high cetane number. GTL fuel has good ignitability and low HC (hydrocarbon) emissions.

  On the other hand, bioethanol has been put into practical use in gasoline engines, and ethanol and other alternative fuels may be used in diesel engines in the future. When using ethanol or other alternative fuels in a diesel engine, there is a concern about a decrease in ignitability due to a decrease in cetane number. Low cetane number fuel has a longer ignition delay period, and as a result, the amount of fuel injected during the ignition delay period also increases. As a result, the fuel diffuses and reaches a relatively low temperature region such as the periphery of the bore wall of the cylinder, and the ignitability is further deteriorated. If the ignitability of the fuel deteriorates, the risk of the fuel being discharged unburned increases. Moreover, there is a concern about deterioration of fuel consumption.

  Thus, when using low cetane number fuel with low self-ignitability for a diesel engine, forcibly igniting fuel is performed. For example, in a direct injection diesel engine with a combustion chamber recessed at the top of the piston, the injection valve has two systems, a main injection valve and an ignition injection valve, and the former has been proposed to inject prior to the latter Yes. In this proposal, first, injection is performed from a main injection valve, and after a preset period, fuel is injected from an ignition injection valve, and this fuel is forcibly ignited by a glow plug (see Patent Document 1).

JP-A-5-126024

  However, since the low cetane number fuel has a problem in ignitability, there is a possibility that it will not be ignited even if forced ignition by the glow plug is attempted, and there is a possibility that the fuel that has not been ignited will be discharged as unburned HC. Further, if the fuel is not ignited, it is difficult to improve the fuel consumption.

  Therefore, the present invention uses a high cetane number fuel as a fuel together with a low cetane number fuel, and suppresses the emission of HC and improves the fuel consumption as compared with the case where only a low cetane number fuel is used. It is an issue to provide.

  In order to solve such a problem, a fuel injection device of the present invention includes a fuel injection valve having a nozzle body in which a needle valve is housed and a nozzle hole is provided at a tip portion, and low cetane around the nozzle hole. Fuel supply means for supplying a high cetane fuel to the periphery of the nozzle hole prior to the supply of the fuel. Then, at the time of fuel injection, prior to the injection of the low cetane number fuel, the high cetane number fuel is injected from the nozzle hole.

  When attention is paid to the temperature distribution in the cylinder, the vicinity of the cylinder bore wall is cooler than the surroundings. For this reason, when low cetane number fuel is distributed in such a low temperature region, unburned fuel is likely to be generated. Therefore, the fuel is supplied so that the high cetane fuel is injected from the injection hole in the initial stage of injection. If high cetane number fuel is injected at the beginning of injection, the high cetane number fuel concentrates at the tip of the spray. The tip of the spray reaches the vicinity of the cylinder bore wall, but if it is a high cetane fuel, good combustion can be achieved even in the vicinity of the cylinder bore wall, which is cooler than the surroundings, and the ignition delay is also reduced. Can be suppressed. Also, the low cetane number fuel is distributed near the center of the cylinder and can be burned. If the ignition delay is suppressed, it is possible to suppress the low cetane number fuel from diffusing and reaching a relatively low temperature region such as around the bore wall of the cylinder. It can be realized.

  Thereby, ignition delay can be suppressed, unburned fuel can be reduced, and generation | occurrence | production of HC can be suppressed. In addition, an improvement in fuel efficiency is expected due to a reduction in unburned fuel. Furthermore, changes in NOx and particulate matter (PM) can be suppressed.

  In order to suppress an increase in the combustion temperature of the diesel engine, the compression ratio of the engine may be swung in the low compression ratio direction. As the compression ratio progresses and the increase in combustion temperature is suppressed, combustion of low cetane number fuel becomes difficult. However, in the fuel injection device according to the present invention, the high cetane number fuel is distributed in the low temperature region in the cylinder, so that the ignition delay of the fuel is suppressed, the unburned fuel is reduced, and hence the generation of HC. Suppression and fuel consumption can be improved.

  According to the present invention, it is possible to suppress ignition delay, reduce unburned fuel, suppress HC emission, and improve fuel efficiency.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram illustrating a schematic configuration of a fuel injection device 1 according to an embodiment. FIG. 2 is a schematic configuration diagram schematically showing the fuel injection valve 10 included in the fuel injection device 1, FIG. 2A shows a state before fuel injection, and FIG. 2B shows fuel injection. FIG. 2 (C) shows a state after fuel injection. In FIG. 2, an A portion that is a tip portion of the fuel injection valve 10 is shown in an enlarged manner.

  The fuel injection device 1 is attached to a four-cylinder diesel engine. The fuel injection device 1 includes a fuel injection valve 10 having a nozzle body 11 in which a needle valve 12 is housed and an injection hole 11a is provided at a tip portion. On the proximal end side of the needle valve 12, a piezo element 13 is laminated and disposed. An electronic drive unit (EDU) 14 is connected to each piezo element 13. The needle valve 12 slides in the nozzle body 11 by controlling the voltage application to the piezo element 13. An electronic control unit (ECU) 50 is connected to the EDU 14. The ECU 50 corresponds to a control unit in the present invention. The fuel injection valve 10 opens and closes according to a command from the ECU 50 to inject fuel.

  Four fuel injection valves 10 are provided for each cylinder, and four fuel injection valves 10 are prepared. One fuel injection valve 10 can inject two types of fuel. The two kinds of fuels are a low cetane number fuel as a main fuel and a GTL fuel having a higher cetane number than the low cetane number fuel.

  As shown in detail in part A of FIG. 2, the fuel injection valve 10 includes a first seal portion 15 provided on the distal end side of the nozzle body 11, and a first seal portion 15 provided on the base end side of the first seal portion 15. 2 seal portions 16. A first fuel supply part 17 is formed between the first seal part 15 and the second seal part 16. A second fuel supply unit 18 is formed on the base end side of the second seal unit 16. The first fuel supply unit 17 is supplied with GTL fuel, and the second fuel supply unit 18 is supplied with main fuel.

  As described above, the fuel injection valve 10 is provided with the first fuel supply unit 17 on the side close to the injection hole 11 a in the nozzle body 1, and more proximal than the first fuel supply unit 17 in the nozzle body 11. A second fuel supply unit 18 is provided on the side. Thereby, GTL fuel can be supplied to the periphery of the nozzle hole 11a prior to the supply of the main fuel to the periphery of the nozzle hole 11a.

  The fuel injection device 1 includes a first fuel line 20 that supplies GTL fuel to the fuel injection valve 10 and a second fuel line 30 that supplies main fuel to the fuel injection valve 10. The first fuel line 20 and the second fuel line 30 together with the first fuel supply unit 17 and the second fuel supply unit 18 constitute fuel supply means in the present invention. The first fuel line 20 and the second fuel line 30 are fuel-injected so that GTL fuel, which is a high cetane fuel, can be supplied around the nozzle holes before the main fuel, which is a low cetane fuel, is supplied to the nozzle holes 11a. Connected to the valve 10.

  The first fuel line 20 includes a first fuel tank 21 and a first supply path 23 that connects the first fuel tank 21 and the first common rail 22. A first pump 24 is disposed in the first supply path 23. The first fuel line 20 has a second supply path 25 that connects the first common rail 22 and each fuel injection valve 10. The second supply path 25 is connected to a first fuel supply unit 17 formed in the fuel injection valve 10. A first valve 54 is disposed in the first fuel supply unit 17, the second supply path 25, and the connection part. The first valve 54 can shut off the supply of fuel to the first fuel supply unit 17 and includes a piezoelectric element. The piezoelectric element is electrically connected to the ECU 50. The ECU 50 performs opening / closing control of the first valve 54. The piezoelectric element contracts when a voltage is applied based on a command from the ECU 50, opens the connection portion, and connects the second supply path 25 and the first fuel supply portion 17. Thereby, the inflow of GTL fuel into the first fuel supply unit 17 is allowed.

  Further, the first fuel line 20 has a return path 26 that connects each fuel injection valve 10 and the first fuel tank 21. The return path 26 is connected to a first fuel supply unit 17 formed in the fuel injection valve 10. A second valve 55 is disposed in the first fuel supply unit 17, the return path 26, and the connection unit. The second valve 55 can block the discharge of fuel from the first fuel supply unit 17 and includes a piezoelectric element. The piezoelectric element is electrically connected to the ECU 50. The ECU 50 performs opening / closing control of the second valve 55. The piezoelectric element contracts when a voltage is applied based on a command from the ECU 50, opens the connecting portion, and connects the return path 26 and the first fuel supply unit 17. Thereby, the GTL fuel is allowed to be discharged from the first fuel supply unit 17.

  The second fuel line 30 includes a second fuel tank 31 and a third supply path 33 that connects the second fuel tank 31 and the second common rail 32. A second pump 34 is disposed in the third supply path 33. The second fuel line 30 has a fourth supply path 35 that connects the second common rail 32 and each fuel injection valve 10. The fourth supply path 35 extends into the fuel injection valve 10 and communicates with the second fuel supply unit 18.

  An in-cylinder pressure sensor 51 corresponding to ignition delay detection means is electrically connected to the ECU 50. The ECU 50 compares the timing of the injection command issued by itself with the information related to the in-cylinder pressure acquired by the in-cylinder pressure sensor 51 to grasp the combustion state in the cylinder. More specifically, it is determined whether or not an ignition delay has occurred in the cylinder. If the increase in the in-cylinder pressure is slow after the injection command is issued, it can be estimated that an ignition delay has occurred.

  The basic operation of the fuel injection valve 10 in the fuel injection device 1 configured as described above will be described with reference to FIG. The fuel injection valve 10 can perform various injections such as pilot injection and main injection, but the same operation can be performed in any case. First, the state before fuel injection will be described. Before fuel injection, the needle valve 12 is seated on the first seal portion 15 and the second seal portion 16 as shown in FIG. In this state, the GTL fuel is stored in the first fuel supply unit 17 by opening the first valve 54 and closing the second valve 55. Further, the main fuel is supplied to the second fuel supply unit 18. Thus, in the state before fuel injection, the GTL fuel, which is a high cetane fuel, is stored on the distal end side of the fuel injection valve 10, and the main fuel, which is a low cetane fuel, is stored on the proximal end side.

  Next, the state at the time of fuel injection will be described. As shown in FIG. 2B, when the needle valve 12 is pulled up to the proximal end side, the seating of the needle valve 12 in the first seal portion 15 is released, and the injection hole 11a is opened. Further, the seating of the needle valve 12 on the second seal portion 16 is released, and the first fuel supply portion 17 and the second fuel supply portion 18 communicate with each other. At this time, both the first valve 54 and the second valve 55 are basically closed.

  When the nozzle hole 11a is opened, fuel is injected. At this time, since GTL fuel is stored in a position near the injection hole 11a, GTL fuel is injected prior to the main fuel. Then, following the GTL fuel, the main fuel passes through the first fuel supply unit 17 and is injected. FIG. 3 is an explanatory view schematically showing the state of spraying of the fuel injected into the cylinder. The fuel distribution in the spray is a distribution in which the concentration of the GTL fuel is high at the spray tip portion indicated by reference numeral B in FIG. The spray tip approaches a cylinder bore wall whose temperature is lower than that of the surroundings, but since the GTL fuel, which is a high cetane fuel, is distributed at the spray tip, the ignition delay can be suppressed.

  Next, the state after fuel injection will be described. As shown in FIG. 2C, the needle valve 12 is seated on the first seal portion 15 and the second seal portion 16. The first valve 54 and the second valve 55 immediately after injection are both opened. This is a measure for discharging the main fuel that has entered the first fuel supply unit 17 during fuel injection. That is, the GTL fuel is introduced into the first fuel supply unit 17 by opening the first valve 54, and the main fuel that has entered the first fuel supply unit 17 by opening the second valve 55 is opened. The fuel can be pushed out and discharged by the introduced GTL fuel. If the second valve 55 is closed after the desired amount of main fuel is discharged from the first fuel supply unit 17, the state before fuel injection shown in FIG.

  The above is the basic operation of the fuel injection valve 10 in the fuel injection device 1. Next, an example of control of the fuel injection device 1 will be described with reference to the chart shown in FIG.

  First, the control policy will be described. Although the main fuel and the GTL fuel of the present embodiment are used, the main fuel and the GTL fuel do not always have a constant cetane number, and the cetane number is assumed to be different for each refueling. The Therefore, even if the cetane number changes, the ignition delay is suppressed to keep the ignition timing substantially constant. As a result, changes in PM and NOx are suppressed as much as possible, and HC emissions are kept substantially constant.

  The in-cylinder pressure changes under the influence of the ignition delay in the cylinder. In addition, the ignition delay is affected by the cetane number of the fuel. Therefore, the opening / closing control of the first valve 54 and the second valve 55 is performed based on the information acquired by the in-cylinder pressure sensor 51 serving as the ignition delay detection means, thereby controlling the fuel distribution in the spray.

  First, the opening / closing control of the first valve 54 and the second valve 55 in the standard state set in advance will be described. The standard state is a state predetermined as a state in which ignition can be performed within an appropriate period. If the cetane number of the main fuel or GTL fuel is different, it will deviate from this standard state.

  Before fuel injection in the standard state, the first valve 54 is opened, while the second valve 55 is closed. At the time of injection, the first valve 54 is closed in accordance with the opening of the needle valve 12. At this time, the second valve 55 maintains the closed state. Thereby, the GTL fuel in the 1st fuel supply part 17 is injected from the injection hole 11a, and the main fuel is injected in the form which follows this. After injection, both the first valve 54 and the second valve 55 are opened according to the closing of the needle valve 12. As a result, the main fuel is discharged from the first fuel supply unit 17 and the GTL fuel is filled into the first fuel supply unit 17 as described above. Here, the valve opening time of the second valve 55 is set to a time during which the main fuel can be discharged from the first fuel supply unit 17.

  When it is determined from the information acquired by the in-cylinder pressure sensor 51 that there is no ignition delay and fuel having a higher cetane number than the standard state is used, the second valve 55 after fuel injection Shorten the valve opening time. The opening time of the second valve 55 after fuel injection can be made shorter as the ignition delay becomes smaller. When the opening time of the second valve 55 is short, the amount of main fuel discharged from the first fuel supply unit 17 is reduced. As a result, the amount of GTL fuel injected is also reduced. When the cetane number of the main fuel is high or the cetane number of the GTL fuel is high, even if the injection amount of the GTL fuel is decreased, a good ignition state can be realized without causing an ignition delay. it can.

  On the other hand, when it is determined from the information acquired by the in-cylinder pressure sensor 51 that an ignition delay has occurred and fuel having a lower cetane number than that in the standard state is used, the opening time of the first valve 54 is lengthened. Time. The valve opening time of the first valve 54 can be made longer as the degree of ignition delay increases. That is, even after the needle valve 12 is opened, the first valve 54 is kept open, and the supply of GTL fuel is continued. Thereby, the ratio of GTL fuel with a high cetane number can be increased, and ignition delay can be suppressed.

  As described above, according to the present invention, a high cetane fuel can be used together with a low cetane fuel as a fuel, and the ignition delay can be suppressed as compared with the case where only a low cetane fuel is used. HC emissions can be suppressed and fuel consumption can be improved.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope. For example, in the above embodiment, GTL fuel is used as the high cetane fuel, but other fuels can be used.

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a fuel injection device according to an embodiment. 2 is a schematic configuration diagram schematically showing the fuel injection valve. FIG. 2 (A) shows a state before fuel injection, FIG. 2 (B) shows a state at the time of fuel injection, and FIG. (C) is a figure which shows the state after fuel injection. FIG. 3 is an explanatory view schematically showing the state of spraying of the fuel injected into the cylinder. FIG. 4 is a chart showing an example of control of the fuel injection device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel injection apparatus 10 ... Fuel injection valve 11 ... Nozzle body 11a ... Injection hole 12 ... Needle valve 13 ... Piezo element 14 ... EDU 15 ... 1st valve 16 ... 2nd valve 17 ... 1st fuel supply part 18 ... 2nd Fuel supply unit 20 ... first fuel line 21 ... first fuel tank 22 ... first common rail 24 ... first pump 30 ... second fuel line 31 ... second fuel tank 32 ... second common rail 34 ... second pump 50 ... ECU
51 ... In-cylinder pressure sensor 54 ... First valve 55 ... Second valve

Claims (8)

A fuel injection valve having a nozzle body in which a needle valve is housed and a nozzle hole is provided at the tip;
Fuel supply means for supplying high cetane fuel to the periphery of the nozzle hole prior to the supply of low cetane fuel to the periphery of the nozzle hole;
With
A fuel injection device for injecting high cetane number fuel from the nozzle hole prior to injection of low cetane number fuel during fuel injection. The fuel supply means includes
A first fuel supply unit that is provided on the side of the nozzle body close to the nozzle hole and that is supplied with high cetane fuel;
A second fuel supply unit provided at a base end side of the first fuel supply unit in the nozzle body and supplied with a low cetane number fuel;
The fuel injection device according to claim 1, comprising: The fuel supply means includes
A first fuel supply unit that is provided on the side of the nozzle body close to the nozzle hole and that is supplied with high cetane fuel;
A second fuel supply unit provided at a base end side of the first fuel supply unit in the nozzle body and supplied with a low cetane number fuel;
A first valve that shuts off fuel supply to the first fuel supply unit;
A second valve for shutting off fuel discharge from the first fuel supply unit;
A control unit that performs open / close control of the first valve and open / close control of the second valve;
The fuel injection device according to claim 1, further comprising: The fuel injection valve includes a first seal portion provided on a distal end side of the nozzle body, and a second seal portion provided on a proximal end side with respect to the first seal portion,
3. The space between the first seal portion and the second seal portion is the first fuel supply portion, and the base end side of the second seal portion is the second fuel supply portion. Or the fuel-injection apparatus of 3. Equipped with ignition delay detection means for detecting the ignition delay in the cylinder;
4. The fuel injection device according to claim 3, wherein the control unit controls opening and closing of the first valve and opening and closing of the second valve based on information acquired by the ignition delay detection means. Equipped with ignition delay detection means for detecting the ignition delay in the cylinder;
The control unit controls the opening and closing of the first valve and the opening and closing of the second valve based on the information acquired by the ignition delay detecting means, and the valve opening time of the second valve becomes smaller as the degree of the ignition delay becomes smaller. 4. The fuel injection device according to claim 3, wherein a short time is set. Equipped with ignition delay detection means for detecting the ignition delay in the cylinder;
The control unit controls the opening and closing of the first valve and the opening and closing of the second valve based on information acquired by the ignition delay detection means, and the valve opening time of the first valve increases as the degree of ignition delay increases. The fuel injection device according to claim 3, wherein   The fuel injection device according to any one of claims 3 to 7, wherein the first valve and the second valve have piezoelectric elements.

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