JP4123969B2 - Fuel injection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to an improvement related to suppression of deposit accumulation on an injector thereof.
[0002]
[Prior art]
In recent years, an in-cylinder injection type internal combustion engine in which an injection hole of an injector is disposed so as to be exposed to a combustion chamber and fuel is directly injected into the combustion chamber has been put into practical use. In such an in-cylinder internal combustion engine, the fuel remaining in the injector nozzle hole after injection is exposed to high temperatures due to combustion in the combustion chamber and hatched, and particulate matter (patties) generated by combustion in the combustion chamber. A deposit may be deposited in the injector nozzle hole by, for example, solidifying the fuel remaining in the nozzle hole as a binder. If the deposit of the injector progresses, the fuel injection rate from the injector changes, causing problems such as deterioration in the accuracy of fuel injection amount control.
[0003]
Therefore, conventionally, the accumulation of deposits on the injector is suppressed by slowing combustion by retarding the ignition timing so that the temperature at the tip of the injector where the nozzle hole is formed is maintained lower than the deposit generation temperature. It has been proposed (Patent Document 1, etc.).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-130022
[Problems to be solved by the invention]
If the combustion becomes slow, the combustion temperature is lowered and the tip temperature of the injector is also lowered. Therefore, it is possible to surely suppress deposit accumulation. However, if the combustion is slowed down, the combustion state deteriorates, leading to problems such as deterioration in fuel efficiency.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection device for an internal combustion engine that can suitably suppress deposit accumulation on an injector without causing deterioration of the combustion state. There is.
[0007]
[Means for Solving the Problems]
In the following, means for achieving the above-described object and its operational effects are described .
[0008]
The invention described in 請 Motomeko 1 is a fuel injection system for an internal combustion engine, and selectively switching the switching means between the fuel heavy fuel and light fuel injected from the injector, during high-load operation, The gist of the invention is that it comprises control means for controlling the switching means so as to inject the light fuel, and otherwise inject the heavy fuel.
[0009]
According to a second aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, a switching means for selectively switching the fuel injected from the injector between a heavy fuel and a light fuel, a high load, a high rotation speed The gist of the invention is that it comprises 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 configuration, light fuel with high volatility is injected from the injector when the temperature at the tip of the injector is high and the engine is in an operating condition where deposit accumulation is likely to proceed, such as during high load operation or high load high rotation operation. The At this time, the fuel remaining in the injection hole of the injector after the injection is highly volatile, and thus is quickly vaporized. As a result, the fuel remaining in the nozzle hole for a long time enough to be deposited is reduced, and deposit accumulation is suppressed.
[0011]
In addition, when the engine operating conditions are such that deposit accumulation is difficult to proceed, 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 according to the injection.
[0012]
Therefore, according to the said structure, the deposit of the deposit to an injector can be suppressed suitably. In addition, deposit accumulation is suppressed only by switching the fuel to be injected. Therefore, it is not necessary to change the setting of the ignition timing, and the combustion state is not deteriorated.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying a fuel injection device for an internal combustion engine of the present invention will be described in detail with reference to FIGS.
[0014]
In FIG. 1, the schematic structure of the fuel-injection apparatus of the internal combustion engine of this embodiment is shown. The present embodiment is applied to a direct injection 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. In one of these fuel tanks 20A, heavy fuel having reduced volatility is stored, for example, by adding an anti-knock agent that increases the octane number. The other fuel tank 20B stores light fuel with high volatility.
[0016]
Individual fuel supply paths 21A and 21B are connected to the fuel tanks 20A and 20B, respectively. Feed pumps 22A and 22B, high-pressure pumps 23A and 23B, and pressure accumulating pipes 24A and 24B are individually disposed in the fuel supply paths 21A and 21B, respectively.
[0017]
The fuel in the fuel tanks 20A and 20B is sucked by the feed pumps 22A and 22B and sent to the high-pressure pumps 23A and 23B, respectively. 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 is discharged to the pressure accumulating pipes 24A and 24B. The high-pressure fuel thus pressurized is stored in the pressure accumulating pipes 24A and 24B, respectively. Therefore, heavy fuel is accumulated in the pressure accumulation pipe 24A, and light fuel is accumulated in the high pressure state in the pressure accumulation pipe 24B.
[0018]
Distribution pipes 25A and 25B for distributing and supplying fuel to the injector 11 are connected to the pressure accumulating pipes 24A and 24B. The distribution pipes 25 </ b> A and 25 </ b> B of both the pressure accumulating pipes 24 </ b> A and 24 </ b> B are connected to the injector 11 after being joined by the switching valve 26.
[0019]
The switching valve 26 selectively connects either the pressure accumulation pipe 24 </ b> A in which heavy fuel is accumulated or 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 such a 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. Switching of the connection by the switching valve 26 is performed based on a command from the electronic control unit 30 that controls various controls of the internal combustion engine 10. The electronic control unit 30 is connected with various sensors for detecting engine operating conditions such as an NE sensor 31 for detecting the engine rotation speed and an accelerator sensor 32 for detecting an accelerator operation amount. The electronic control unit 30 performs engine control such as control of the fuel injection amount from the injector 11, fuel injection timing, and ignition timing based on the engine operation status detected by these sensors. In this embodiment, as part of such engine control, the “injected 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 “injected fuel switching control” of the present embodiment. The processing in FIG. 7 is periodically performed by the electronic control unit 30 as a scheduled interruption 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 rotational 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 region is easy to deposit.
[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 on the basis of the engine speed NE and the engine load KL is in a region indicated by hatching, it is determined that the deposit is likely to be deposited on the injector 11. I have to. The area where such deposits are easily deposited is set as follows.
[0024]
As 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 a region where deposits are likely to accumulate on the injector 11. Further, when the engine rotational speed NE is increased, the combustion interval in real time is shortened, and the cooling performance at the tip of the injector 11 is lowered, so that deposits are easily deposited on the injector 11. Therefore, in the map, the load region in which it is determined that deposits are likely to be deposited on the injector 11 is widened during high-speed operation as compared to during low-speed operation. That is, as the engine rotational 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]
If it is determined here that the deposit is likely to be deposited (S100: YES), the switching valve 26 is controlled so as to connect the pressure accumulating pipe 24B accumulating light fuel 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 it is difficult to deposit (S100: NO), the switching valve is connected so as to connect the pressure accumulating pipe 24A accumulating heavy fuel to the injector 11. 26 is controlled (S120).
[0026]
In this embodiment, light fuel is injected from the injector 11 when the tip temperature of the injector 11 is high and deposits are likely to accumulate, such as during high-speed / high-load operation. 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]
When light fuel is injected, the fuel remaining in the injection hole of the injector 11 after the injection is highly volatile, and thus is quickly vaporized. For this reason, the fuel remaining in the nozzle hole for a long period of time as depositing is reduced, and deposits are difficult to be deposited on the injector 11 even under engine operating conditions where deposits are likely to be deposited.
[0028]
At the time of heavy fuel injection, since the volatility of the fuel is low, the fuel tends to remain in the injection hole of the injector 11, but the tip temperature of the injector 11 at that time is low, and a new deposit is difficult to be generated. In addition, since the heavy fuel has a high viscosity, the deposit accumulated in the nozzle hole is effectively swept away according to the injection, and the deposit already deposited is removed.
[0029]
Therefore, according to the fuel injection device for an internal combustion engine of the present embodiment, deposit accumulation on the injector 11 can be suitably suppressed. In addition, since deposit accumulation is suppressed only by switching the fuel to be injected, it is not necessary to change the setting of the ignition timing or the like, and the combustion state is not deteriorated.
[0030]
By the way, with heavy fuel produced by adding anti-knock agents as described above, the advance limit of the ignition timing is expanded by improving the knock resistance, and the fuel efficiency is improved. 11 deposits are likely to proceed. In this respect, in the present embodiment, the use of heavy fuel is allowed as long as the deposit accumulation of the injector 11 can be suppressed. Therefore, it is possible to achieve both the suppression of deposit accumulation and the improvement of fuel consumption.
[0031]
Incidentally, in this embodiment, the switching valve 26 corresponds to the “switching means”. The electronic control device 30 that switches the fuel injected from the injector 11 based on the operation control of the switching valve 26 has a configuration corresponding to the “control means”.
[0032]
The switching of the injected fuel as described above can also be performed in an internal combustion engine having a fuel supply system as follows. Even in an internal combustion engine having such a fuel supply system, effects similar to those of the above-described embodiment can be obtained by switching the injected fuel in a manner in accordance with the “injected fuel switching control”.
[0033]
(Modification 1)
The fuel supply system of the internal combustion engine shown in FIG. 4 includes a fuel tank 50 that stores light fuel, a fuel supply passage 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 additives for increasing the weight of the additive are stored. The additive tank 53 is connected to the fuel supply path 51 via the switching valve 54, and the additive is selectively introduced into the fuel in the fuel supply path 51 by the operation of the switching valve 54. ing.
[0034]
Here, if the additive in the additive tank 53 is introduced by the switching valve 54 and the fuel in the fuel supply path 51 is made heavy, the fuel injected from the injector 11 can be made heavy fuel. Further, if the introduction of the additive into the fuel is stopped by the switching valve 54, the fuel injected from the injector 11 becomes a light fuel. Therefore, it is possible to switch the injected fuel as in the above embodiment.
[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 partitioned into two fuel chambers 60A and 60B by a semipermeable membrane 61 that allows only light components in the fuel to pass through. The fuel chamber 60 </ b> A is provided with a fuel filler port 62, and fuel is introduced through the fuel filler port 62. Individual fuel supply paths 63A and 63B are connected to the fuel chamber 60A and the fuel chamber 60B, respectively. The fuel supply paths 63A and 63B are joined by the switching valve 64 and then connected to the injector 11. .
[0036]
When fuel is introduced into the fuel chamber 60 </ b> A of the fuel tank 60, only light components of the fuel move to the fuel chamber 60 </ b> B through the semipermeable membrane 61 due to osmotic pressure. Thereby, the heavy component and the light component in the fuel are separated, the heavy fuel containing a lot of heavy components in the fuel chamber 60A, and the light fuel containing only the light components in the fuel chamber 60B, respectively. It will be accumulated. 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, it is possible to switch the injected fuel as in the above embodiment. .
[0037]
(Other changes)
In addition, the said embodiment and its modification examples 1 and 2 can also be changed as follows.
[0038]
The deposit amount of the injector 11 may be estimated, and the selection mode of 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 for injecting heavy fuel 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 deposit amount is sufficiently small, some deposit accumulation is acceptable, so the operating range for injecting heavy fuel can be expanded to increase the fuel efficiency and other effects. The spray is made more aggressive. In addition, when the current amount of deposit deposition is larger than a certain amount, the operating range for injecting light fuel is expanded in order to more reliably suppress further deposit deposition.
[0039]
As described above, by variably setting the engine operation region in which the heavy / light fuel injection is performed according to the estimation result of the deposit accumulation amount, it is possible to switch the injected fuel more efficiently. When the estimated deposit amount is sufficiently small, heavy fuel may be injected under all engine operating conditions.
[0040]
Incidentally, the estimation of the deposit accumulation amount of the injector 11 can be performed as follows, for example. When the deposit accumulation amount increases, the injection rate (fuel injection amount per unit time) of the injector 11 decreases. Here, if air-fuel ratio feedback control is being performed, the air-fuel ratio feedback correction value and the air-fuel ratio learning value change in order 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 the transition of the air-fuel ratio feedback correction value and the air-fuel ratio learning value.
[0041]
Further, when the deposit accumulation amount increases, the combustion state deteriorates due to the change in the injection rate and the fuel spray shape, and the torque fluctuation of the internal combustion engine increases. Therefore, the deposit accumulation amount can be estimated based on the torque fluctuation amount.
[0042]
In the above embodiment, it is determined whether or not the engine 11 is in an operating condition where deposits are likely to be deposited on the injector 11 based on the engine rotational speed NE and the engine load KL, but only based on the engine load KL The determination may be performed. That is, based on only the engine load KL, even if the injection fuel switching control is performed such that light fuel is injected during high-load operation and heavy fuel is injected otherwise, a sufficient deposit accumulation suppressing effect is achieved. Can be played.
[0043]
Further, if it is possible to determine whether or not engine operating conditions are likely to cause deposits to be deposited on the injector 11, the determination may be performed using control parameters other than the engine load KL and the engine rotational speed NE. . Even in this case, deposit accumulation can be suppressed by switching the injected fuel so that light fuel is injected when the engine operating conditions are likely to cause deposits, and heavy fuel is injected otherwise.
[0044]
In the above embodiment, as an example of a heavy fuel, a fuel to which an anti-knock agent is added is cited, and as an example of a light fuel, a fuel to which such an anti-knock agent is not added is cited. Of the two different types of fuels, if a fuel with higher volatility is used as a light fuel and a fuel with lower volatility is used as a heavy fuel, an effect similar to or similar to the above embodiment can be achieved.
[0045]
Next, the technical ideas grasped from the embodiments of the present invention described above are listed below.
(B) said light fuel, the control apparatus for an internal combustion engine according to claim 1 or 2 which is fuel highly volatile than the heavy fuel.
[0046]
(B) The control device for an internal combustion engine according to any one of claims 1 and 2 , and (i), wherein the injector is disposed such that a tip thereof is exposed to the combustion chamber.
(C) the internal combustion engine, according to claim 1, 2 is an internal combustion engine of cylinder injection type, and a control device for an internal combustion engine according to any one of the above (i).
[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 illustrating 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 of a second modification.
6 is a graph showing a modification 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 pump, 24A, 24B ... Pressure accumulating pipe, 25A, 25B ... Distribution pipe, 26, 54, 64 ... Switching valve, 53 ... Additive tank, 61 ... Semipermeable membrane, 62 ... Filling port, 30 ... Electronic control unit, 31 ... NE sensor, 32 ... Accelerator sensor.

Claims (2)

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 during high-load operation, 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;
  Control means for controlling the switching means to inject the light fuel during a high-load high-speed operation, and to inject the heavy fuel otherwise.
A fuel injection device for an internal combustion engine.

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