JP2004251217A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion engine capable of satisfactorily suppressing deposit on an injector without worsening a combustion condition. <P>SOLUTION: A fuel supply system of this internal combustion engine 10 is provided with two fuel tanks 20A, 20B storing heavy fuel having low volatility and light fuel having high volatility, respectively, and fuel injected from the injector 11 can be switched by a selector valve 26. An electronic controller 30 controls the selector valve 26 to inject light fuel from the injector 11 when tip temperature of the injector 11 is high and high load/high speed rotating operation allowing easy deposit is performed, and to inject heavy fuel from the injector 11 in other case. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to an improvement relating to suppression of deposit accumulation on an injector thereof.
[0002]
[Prior art]
2. Description of the Related Art In recent years, an in-cylinder internal combustion type internal combustion engine in which an injection hole of an injector is arranged to be exposed to a combustion chamber and fuel is directly injected into the combustion chamber has been used. In such a direct injection internal combustion engine, the fuel remaining in the injection hole of the injector after injection is exposed to the high temperature due to combustion in the combustion chamber and becomes soot, and the particulate matter generated by combustion in the combustion chamber (patty). Deposits may accumulate in the injector orifice, for example, when the cured material (curable matter) enters the injector orifice and solidifies as a binder with the fuel remaining in the orifice. Then, as the accumulation of deposits in the injector progresses, the injection rate of fuel from the injector changes, which causes problems such as deterioration in accuracy of fuel injection amount control.
[0003]
Conventionally, the accumulation of deposits on the injector is suppressed by slowing the combustion by retarding the ignition timing, etc., so that the temperature of the injector tip where the injection hole is formed is kept lower than the deposit generation temperature. It has been proposed to do so (Patent Document 1 etc.).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-130022
[Problems to be solved by the invention]
If the combustion becomes slow, the combustion temperature decreases and the temperature at the tip of the injector also decreases, so that the accumulation of deposits can be suppressed. However, if the combustion is slow, the combustion state deteriorates, which leads to problems such as deterioration of fuel efficiency.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection device for an internal combustion engine that can appropriately suppress accumulation of deposits on an injector without deteriorating a combustion state. It is in.
[0007]
[Means for Solving the Problems]
Hereinafter, means for achieving the above-described object and the effects thereof will be described.
According to a first aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, wherein switching means for selectively switching fuel injected from an injector between heavy fuel and light fuel, and deposit deposition on the injector. The gist of the present invention is to include control means for controlling the switching means so as to inject the light fuel when the engine is in an engine operating condition in which the fuel gas is likely to advance, and to inject the heavy fuel otherwise when the engine is operating.
[0008]
According to a second aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, comprising: a switching unit for selectively switching fuel injected from an injector between heavy fuel and light fuel; The gist of the present invention is to include control means for controlling the switching means so as to inject the light fuel, and in other cases, to inject the heavy fuel.
[0009]
According to a third aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, comprising: switching means for selectively switching fuel injected from an injector between heavy fuel and light fuel; The gist of the present invention is to include control means for controlling the switching means so as to inject the light fuel during operation and to inject the heavy fuel otherwise.
[0010]
In the above-described configuration, when the tip temperature of the injector is high and the engine is in an engine operating condition in which deposit accumulation easily proceeds, such as during high-load operation or high-load high-speed operation, highly volatile light fuel is injected from the injector. You. At this time, the fuel remaining in the injection hole of the injector after the injection is rapidly vaporized because of its high volatility. As a result, the amount of fuel remaining in the injection hole for a long period of time so as to form a deposit is reduced, and the accumulation of the deposit is suppressed.
[0011]
In addition, when the engine is operating under conditions where deposit accumulation is difficult to progress, heavy fuel with low volatility is injected. Since the heavy fuel injected at this time has a high viscosity, the deposit accumulated in the injection hole can be washed away and removed according to the injection.
[0012]
Therefore, according to the above configuration, it is possible to appropriately suppress the accumulation of the deposit on the injector. Moreover, since deposit accumulation is suppressed only by switching the fuel to be injected, there is no need to change the setting of the ignition timing or the like, and the combustion state does not deteriorate.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a fuel injection device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS.
[0014]
FIG. 1 shows a schematic structure of a fuel injection device for an internal combustion engine according to the present embodiment. This embodiment is applied to an in-cylinder injection type internal combustion engine 10 that directly injects fuel from an injector 11 into a combustion chamber 12.
[0015]
As shown in FIG. 1, the fuel injection device according to the present embodiment includes two fuel tanks 20A and 20B. One of these fuel tanks 20A stores heavy fuel with reduced volatility, for example, by adding an anti-knock agent that increases the octane number. The other fuel tank 20B stores a highly volatile light fuel.
[0016]
Individual fuel supply paths 21A and 21B are connected to the two fuel tanks 20A and 20B, respectively. Feed pumps 22A and 22B, high-pressure pumps 23A and 23B, and accumulator pipes 24A and 24B are individually provided in the fuel supply paths 21A and 21B, respectively.
[0017]
The fuel in the fuel tanks 20A, 20B is sucked by the feed pumps 22A, 22B and sent out to the high-pressure pumps 23A, 23B. The fuel sent from the feed pumps 22A and 22B is pressurized to a required pressure by the high-pressure pumps 23A and 23B, and discharged to the pressure accumulation pipes 24A and 24B. The high-pressure fuel thus pressurized is stored in the pressure accumulation pipes 24A and 24B, respectively. Accordingly, heavy fuel is stored in the pressure accumulating pipe 24A and light fuel is stored in the pressure accumulating pipe 24B in a high pressure state.
[0018]
Distribution pipes 25A and 25B for distributing and supplying fuel to the injector 11 are connected to the pressure accumulation pipes 24A and 24B. The distribution pipes 25A and 25B of the two pressure accumulation pipes 24A and 24B are connected to the injector 11 after being joined by the switching valve 26.
[0019]
The switching valve 26 selectively connects one of the pressure accumulation pipe 24 </ b> A in which heavy fuel is accumulated and the pressure accumulation pipe 24 </ b> B in which light fuel is accumulated to the injector 11. Here, an electromagnetically driven switching valve is employed as the switching valve 26.
[0020]
In this fuel injection device, the operation of the switching valve 26 allows the fuel injected from the injector 11 to be selectively switched between heavy fuel and light fuel. The switching of the connection by the switching valve 26 is performed based on a command from the electronic control device 30 that controls various controls of the internal combustion engine 10. Various sensors for detecting an engine operation state, such as an NE sensor 31 for detecting an engine rotation speed and an accelerator sensor 32 for detecting an accelerator operation amount, are connected to the electronic control unit 30. The electronic control unit 30 performs engine control such as control of the fuel injection amount and the fuel injection timing from the injector 11 and control of the ignition timing based on the engine operation state detected by the sensors. In the present embodiment, as a part of the engine control, the “injection fuel switching control” by the operation control of the switching valve 26 is performed by the electronic control unit 30.
[0021]
FIG. 2 shows a flowchart of the “injection fuel switching control” of the present embodiment. The process of FIG. 9 is periodically executed by the electronic control unit 30 as a periodic interrupt process.
[0022]
When the process of this control is started, first, in step S100, a deposit is deposited on the injector 11 based on the engine speed NE detected by the NE sensor 31 and the engine load KL grasped from the detection result of the accelerator sensor 32. It is determined whether or not the area is in an area where deposition is easy.
[0023]
FIG. 3 shows an example of a map of the engine speed NE and the engine load KL used for the determination here. Here, in this map, when the current engine operating condition grasped based on the engine speed NE and the engine load KL is in the area indicated by hatching, it is determined that the deposit is in the area where deposits are easily deposited on the injector 11. I have to. The area where such deposits are easily deposited is set as follows.
[0024]
When the fuel injection amount increases, the amount of heat generated by combustion increases, and the temperature at the tip of the injector 11 tends to increase. Therefore, in the above map, the high load operation region where the fuel injection amount is large is set as the region where deposits are easily deposited on the injector 11. When the engine speed NE increases, the interval of combustion in real time becomes shorter, and the cooling performance at the tip of the injector 11 decreases, so that deposits tend to be deposited on the injector 11. Therefore, in the above map, the load region where it is determined that deposits are more likely to be deposited on the injector 11 during the high-speed operation than in the low-speed operation is expanded. That is, as the engine speed NE increases, it is determined that deposits are more likely to be deposited on the injector 11 at a lower engine load KL.
[0025]
Here, if it is determined that the deposit is in the region where the deposit is likely to be deposited (S100: YES), the switching valve 26 is controlled so that the pressure accumulation pipe 24B in which the light fuel is accumulated is connected to the injector 11 (S110). On the other hand, when it is determined that this is not the case, that is, when it is determined that the deposit is in an area where deposition is difficult (S100: NO), the switching valve is connected so that the pressure accumulation pipe 24A in which heavy fuel is accumulated is connected to the injector 11. 26 is controlled (S120).
[0026]
In this embodiment, when the tip temperature of the injector 11 is high and deposits are likely to be deposited, such as during high-rotation / high-load operation, light fuel is injected from the injector 11. When the tip temperature of the injector 11 is low and deposits are difficult to deposit, heavy fuel is injected from the same injector 11.
[0027]
At the time of light fuel injection, the fuel remaining in the injection hole of the injector 11 after injection has a high volatility and is quickly vaporized. Therefore, the amount of fuel remaining in the injection hole for a long period of time that the deposit is formed is reduced, and the deposit is less likely to be deposited on the injector 11 even under the engine operating condition in which the deposit is easily deposited.
[0028]
When the heavy fuel is injected, the fuel has low volatility, so that the fuel easily remains in the injection hole of the injector 11, but the tip temperature of the injector 11 at that time is low, and it is difficult to generate a new deposit. In addition, since the heavy fuel has a high viscosity, the deposit accumulated in the injection hole is effectively swept away in response to the injection, and the deposited deposit is removed.
[0029]
Therefore, according to the fuel injection device for an internal combustion engine of the present embodiment, the accumulation of deposits on the injector 11 can be suitably suppressed. Moreover, since deposit accumulation is suppressed only by switching the fuel to be injected, there is no need to change the setting of the ignition timing and the like, and the combustion state is not deteriorated.
[0030]
By the way, in the heavy fuel generated by the addition of the anti-knock agent as described above, the advancement limit of the ignition timing is expanded due to the improvement of the knock resistance, and the fuel economy is improved. No. 11 deposit is likely to proceed. In this regard, in this embodiment, the use of heavy fuel is allowed as long as the deposit accumulation on the injector 11 can be suppressed, so that both the suppression of the deposit accumulation and the improvement of fuel efficiency can be achieved.
[0031]
Incidentally, in this embodiment, the switching valve 26 has a configuration corresponding to the above-mentioned "switching means". An electronic control unit 30 for switching the fuel injected from the injector 11 based on the operation control of the switching valve 26 has a configuration corresponding to the above-mentioned "control means".
[0032]
Note that the switching of the injected fuel as described above can also be performed in an internal combustion engine having a fuel supply system configured as follows. Even in an internal combustion engine having such a fuel supply system, if the switching of the injected fuel is performed in a manner according to the above-described "switching control of the injected fuel", the same effect as the above embodiment can be obtained.
[0033]
(Modification 1)
The fuel supply system of the internal combustion engine shown in FIG. 4 includes a fuel tank 50 in which light fuel is stored, a fuel supply path 51 that supplies light fuel in the fuel tank 50 to the injector 11, and a fuel such as the anti-knock agent. Is provided with an additive tank 53 in which an additive for making the fuel heavy is stored. The additive tank 53 is connected to the fuel supply path 51 via a switching valve 54, and the operation of the switching valve 54 allows the additive to be selectively introduced into the fuel in the fuel supply path 51. ing.
[0034]
Here, when the additive in the additive tank 53 is introduced by the switching valve 54 to make the fuel in the fuel supply path 51 heavier, the fuel injected from the injector 11 can be made heavy. If the introduction of the additive into the fuel is stopped by the switching valve 54, the fuel injected from the injector 11 becomes light fuel. Therefore, the same switching of the injection fuel as in the above embodiment can be performed.
[0035]
(Modification 2)
In the fuel supply system of the internal combustion engine shown in FIG. 5, the inside of the fuel tank 60 is divided into two fuel chambers 60A and 60B by a semi-permeable membrane 61 that allows only light components in the fuel to permeate. A fuel port 62 is provided in the fuel chamber 60 </ b> A, and fuel is introduced through the fuel port 62. The individual fuel supply passages 63A and 63B are connected to the fuel chamber 60A and the fuel chamber 60B, respectively. The fuel supply passages 63A and 63B are connected to the injector 11 after being merged by the switching valve 64. .
[0036]
When fuel is introduced into the fuel chamber 60A of the fuel tank 60, only light components of the fuel move to the fuel chamber 60B via the semi-permeable membrane 61 due to osmotic pressure. As a result, the heavy component and the light component in the fuel are separated, and a heavy fuel containing a large amount of the heavy component is contained in the fuel chamber 60A, and a light fuel containing only the light component is contained in the fuel chamber 60B. It will be stored. Therefore, by switching the fuel injected from the injector 11 by the switching valve 64 between the fuel in the fuel chamber 60A and the fuel in the fuel chamber 60B, the same switching of the injected fuel as in the above embodiment can be performed. .
[0037]
(Other changes)
The above-described embodiment and the first and second modifications can be modified as follows.
[0038]
The deposit accumulation amount of the injector 11 may be estimated, and the mode of selecting the injected fuel may be switched according to the estimation result.
For example, in the determination map shown in FIG. 6, when the estimated deposit accumulation amount is small, the operation region in which heavy fuel is injected is expanded, and when the estimated deposit accumulation amount is large, heavy fuel is injected. The operating area has been reduced. With this setting, if the current amount of deposits is sufficiently small, some deposits can be tolerated, so the operation range for injecting heavy fuel is expanded, and the heavy fuel Injection is made more aggressive. In addition, when the current deposit amount is larger than a certain amount, the operating range in which light fuel is injected is expanded in order to more reliably suppress further deposit accumulation.
[0039]
In this way, by variably setting the engine operation region in which the heavy / light fuel injection is performed in accordance with the estimation result of the deposit amount, it is possible to more efficiently switch the injected fuel. When the estimated deposit amount is sufficiently small, heavy fuel may be injected under all engine operating conditions.
[0040]
Incidentally, the deposit amount of the injector 11 can be estimated, for example, as follows. When the deposit amount increases, the injection rate (fuel injection amount per unit time) of the injector 11 decreases. Here, if the air-fuel ratio feedback control is performed, the air-fuel ratio feedback correction value and the air-fuel ratio learning value change to compensate for the shortage of the fuel injection amount due to the decrease in the injection rate. Therefore, the deposit amount can be estimated from changes in the air-fuel ratio feedback correction value and the air-fuel ratio learning value.
[0041]
Further, when the deposit amount increases, the combustion state deteriorates due to the change in the injection rate or the fuel spray shape, and the torque fluctuation of the internal combustion engine increases. Therefore, the deposit amount can be estimated based on the torque fluctuation amount.
[0042]
In the above-described embodiment, whether or not the engine 11 is in an engine operating condition in which deposits are likely to be deposited on the injector 11 is determined based on the engine speed NE and the engine load KL. However, the determination is made based on only the engine load KL. The determination may be made. That is, even when the fuel injection is switched so as to inject the light fuel during the high load operation and to inject the heavy fuel otherwise, based on only the engine load KL, the sufficient deposit accumulation suppressing effect can be obtained. Can be played.
[0043]
Further, if it is possible to determine whether or not the engine is operating under conditions in which deposits are likely to accumulate on the injector 11, the determination may be made using control parameters other than the engine load KL and the engine speed NE. . In such a case as well, when the engine is operated under conditions where deposits are likely to accumulate, light fuel is injected. Otherwise, heavy fuel is injected to switch the injected fuel so that deposit accumulation can be suppressed.
[0044]
In the above embodiment, as an example of the heavy fuel, a fuel to which an anti-knock agent is added, and as an example of the light fuel, a fuel to which such an anti-knock agent is not added, are mentioned. If the more volatile fuel is used as the light fuel and the less volatile fuel is used as the heavy fuel among the two different fuels, the same effects as those in the above-described embodiment or effects similar thereto can be obtained.
[0045]
Next, technical ideas grasped from the embodiments of the present invention described above are listed below.
(B) The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the light fuel is a fuel having a higher volatility than the heavy fuel.
[0046]
(B) The control device for an internal combustion engine according to any one of (1) to (3) and (A), wherein the injector is disposed such that a tip thereof is exposed to a combustion chamber.
(C) The control device for an internal combustion engine according to any one of (1) to (3) and (A), wherein the internal combustion engine is a direct injection internal combustion engine.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the overall structure of an embodiment of the present invention.
FIG. 2 is a flowchart of injection fuel switching control according to the embodiment;
FIG. 3 is a graph showing a setting example of a determination map used for the switching control.
FIG. 4 is a schematic diagram showing a configuration of a fuel supply system according to a first modification.
FIG. 5 is a schematic diagram showing a configuration of a fuel supply system according to a second modification.
FIG. 6 is a graph showing a modified example of the determination map of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Injector, 12 ... Combustion chamber, 20A, 20B, 50, 60 ... Fuel tank, 21A, 21B, 51, 63A, 63B ... Fuel supply path, 22A, 22B ... Feed pump, 23A, 23B ... High-pressure pumps, 24A, 24B ... pressure accumulating pipes, 25A, 25B ... distribution pipes, 26, 54, 64 ... switching valves, 53 ... additive tanks, 61 ... semi-permeable membranes, 62 ... oil supply ports, 30 ... electronic control devices, 31 ... NE sensor, 32 ... accelerator sensor.

Claims (3)

Switching means for selectively switching fuel injected from the injector between heavy fuel and light fuel;
Control means for controlling the switching means to inject the light fuel when the engine is in a predetermined engine operating condition in which deposit accumulation on the injector is apt to proceed, and to inject the heavy fuel otherwise. A fuel injection device for an internal combustion engine. Switching means for selectively switching fuel injected from the injector between heavy fuel and light fuel;
A fuel injection device for an internal combustion engine, comprising: control means for controlling the switching means so as to inject the light fuel during high load operation and to inject the heavy fuel otherwise. Switching means for selectively switching fuel injected from the injector between heavy fuel and light fuel;
A fuel injection device for an internal combustion engine, comprising: control means for controlling the switching means so as to inject the light fuel during a high-load high-speed operation and to inject the heavy fuel otherwise.

Images