JP2010236492A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve, in a well balanced state, a decrease in torque and an increase in a smoke exhaust amount, due to accumulation of deposits at an injector injection hole. <P>SOLUTION: A fuel injection control device 20 is provided with: an operation state detection means that detects an operation state of an internal combustion engine; a deposit detection means that detects accumulation of deposits at an injection hole 18a of an injector 18; and a control means that makes at least one of a fuel injection period extension control and a fuel injection period retard control, based on results detected by the operation state detection means and the deposit detection means. This configuration suppresses both generation of smoke and decrease in torque and to provide an appropriate fuel injection, even if deposits accumulated at the injection hole 18a cannot be removed sufficiently. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

An internal combustion engine (for example, a diesel engine) provided with an injector for directly injecting fuel into a combustion chamber is known. Here, when deposits are deposited around the injection hole of the injector, a decrease in torque or the like occurs. Then, the technique of removing the deposit adhering to the nozzle hole part of an injector is known (for example, refer patent document 1).
(See Patent Document 1).

JP 2006-2629 A

  It may be difficult to completely remove the deposit at the injector nozzle. An object of this invention is to provide the fuel-injection control apparatus which can implement | achieve appropriate fuel injection, even when the removal of a deposit is not enough.

  The fuel injection control device according to the present invention includes an operating state detecting unit for detecting an operating state of the internal combustion engine, a deposit detecting unit for detecting deposit accumulation in an injection hole portion of the injector, the operating state detecting unit, and the deposit detecting unit. Control means for performing at least one of fuel injection period extension control and fuel injection timing retard control based on the detection result of According to this configuration, the fuel injection period extension control for ensuring the torque and the fuel injection timing delay control for improving the smoke are switched based on the operating state of the internal combustion engine, which is caused by deposit accumulation. And the occurrence of smoke can be suppressed.

  The said structure WHEREIN: The said fuel injection period extension control can be set as the structure performed when the said driving | running state detection means detects a torque shortage.

  In the above configuration, the fuel injection timing retardation control may be performed when the operating state detecting means detects smoke deterioration.

  In the above configuration, the amount of increase in smoke emission is calculated based on the detection result of the deposit detection means, and the amount of retardation in the fuel injection timing retardation control is calculated based on the amount of increase in smoke emission It can be set as the structure further provided with a means. According to this configuration, the amount of retardation required for smoke improvement can be obtained with high accuracy. As a result, a reduction in torque due to retarding the fuel injection timing can be minimized.

  In the above configuration, the calculating means may be configured to increase the retard amount in the fuel injection retard control as the deposit amount detected by the deposit detecting means increases.

  According to the present invention, it is possible to suppress the generation of smoke and the decrease in torque.

FIG. 1 is a diagram illustrating a configuration of a fuel injection device equipped with a fuel injection control device according to a first embodiment. FIG. 2 is a diagram showing the relationship of problems caused by deposit deposition. FIG. 3 is a flowchart illustrating an example of the operation of the fuel injection control apparatus according to the first embodiment. FIG. 4 is a graph showing the relationship between deposit accumulation and fuel consumption. FIG. 5 is a graph showing the relationship between deposit accumulation and smoke emission. FIG. 6 is a graph showing the relationship between the retard amount of the fuel injection timing and the smoke discharge amount. FIGS. 7A and 7B are diagrams for specifically explaining the fuel injection timing retardation control. FIG. 8 is a map showing the relationship between the operating state and the smoke discharge amount. FIG. 9 is a map showing the relationship between the operating state and the control performed by the fuel injection control device.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an overall configuration of a fuel injection device 100 equipped with an ECU 20 as a fuel injection control device according to the first embodiment. The fuel tank 10 stores fuel (for example, light oil) used in the fuel injection device 100. The high-pressure pump 12 pumps fuel from the fuel tank 10 and supplies it to the common rail 14 in a high-pressure state. The common rail 14 stores the fuel supplied from the high-pressure pump 12 in a high-pressure state, and supplies the fuel to the piezo injector 18 through the high-pressure fuel passage 16. A part of the fuel stored in the common rail 14 is returned to the fuel tank 10 through the return passage 19. The piezo injector 18 injects fuel into a combustion chamber (not shown) of the fuel injection device 100 at a predetermined timing for a predetermined period. The uninjected fuel is returned to the fuel tank 10 through a return passage 19 connected to the piezo injector 18.

  The ECU 20 includes a microcomputer, a memory, and the like, detects an operating state based on outputs from various sensors provided in the fuel injection device 100, and performs fuel injection control. Specifically, the ECU 20 controls the fuel injection timing and injection period by transmitting a predetermined drive signal to the piezo injector 18.

  The fuel injection control device (ECU 20) of the present embodiment aims to suppress a decrease in torque and a deterioration in smoke caused by deposit accumulation in the nozzle hole portion 18a of the piezo injector 18 in particular.

  FIG. 2 is a diagram showing the relationship between deposit accumulation and problems caused thereby. When deposits are deposited (A), the area of the nozzle hole is reduced and the fuel injection amount is reduced (B), so that the torque is reduced (C). Moreover, spraying deteriorates due to deposit accumulation (D), and smoke discharge increases (E). This is presumably because the deposit does not uniformly adhere to the periphery of the nozzle hole portion, and the shape of the nozzle hole is distorted, thereby preventing atomization of the injected fuel. Moreover, since fuel consumption deteriorates due to deterioration of spray (F), torque decreases (C). In order to compensate for the decrease in torque, it is effective to perform extension control of the fuel injection period in order to increase the amount of fuel actually supplied to the combustion chamber. In order to suppress smoke emission, it is effective to perform retard control of the fuel injection timing. Details of these measures will be described later.

  FIG. 3 is a flowchart showing the operation of the ECU 20. First, the ECU 20 detects deposit accumulation in the injector nozzle hole (step S10). Detection of deposit accumulation (more specifically, acquisition of deposit accumulation amount) can be performed by a conventionally known method. For example, the concentration of metal (Zn, Mn, etc.) in the fuel is measured by a sensor installed in the nozzle hole, and the temperature at the nozzle tip is measured by a temperature sensor or the like to estimate the deposit amount. it can.

  Next, the ECU 20 calculates a reduction amount of the fuel injection amount due to deposit accumulation in the nozzle hole portion (step S12). Assuming that the change amount of the fuel injection amount is ΔQ, the flow coefficient is Co, the cross-sectional area of the injection hole portion 18a is A, the injection pressure is Pinj, the atmospheric pressure is Po, and the fuel density is ρ, a specific calculation formula is as follows. Street.

  The nozzle hole cross-sectional area A can be calculated from the deposit amount detected in step S10.

  Next, the ECU 20 determines whether extension control of the fuel injection period is possible (step S14), and if possible, based on the change amount (ΔQ) of the fuel injection amount calculated in step S12. The amount of deterioration is estimated (step S16). The determination in step S14 will be described later.

  FIG. 4 is a graph showing the relationship between the change in injection amount (ΔQv) caused by deposit accumulation and the net fuel consumption rate (BSFC). As shown in the figure, both are in a substantially linear relationship, and it can be seen that as the deposit amount increases, the BSFC increases and the fuel consumption deteriorates.

  The ECU 20 estimates the fuel consumption deterioration amount based on the graph of FIG. 4 (step S16), and estimates the torque decrease amount based on that (step S18). The ECU 20 calculates the amount of fuel necessary to compensate for the obtained torque reduction amount (step S20), and extends the fuel injection period by the amount necessary for fuel supply (step S22). The extension of the fuel injection period can be realized by extending the command energization period to the piezo injector 18.

  Next, the ECU 20 determines whether extension control of the fuel injection period is possible (step S24), and if possible, smoke discharge based on the change amount (ΔQ) of the fuel injection amount calculated in step S12. The amount of increase is estimated (step S26). The determination in step S24 will be described later.

  FIG. 5 is a graph showing the relationship between the change in injection amount (ΔQv) caused by deposit accumulation and the smoke discharge amount. As shown in the figure, the change in the injection amount (deposit accumulation) and the smoke discharge amount are in a substantially linear relationship, and it can be seen that the smoke discharge amount increases as the deposit accumulation amount increases.

  The ECU 20 estimates the increase amount of the smoke discharge amount based on the graph of FIG. 5 (step S26), and calculates the retard amount of the injection timing necessary for reducing the smoke discharge amount based on the estimated increase amount (step S26). S28). The ECU 20 retards the fuel injection timing by the retard amount obtained in step S28 (step S30).

  FIG. 6 is a graph showing the relationship between the retard amount of the fuel injection timing and the smoke discharge amount. As shown in the figure, the smoke emission amount increases as the fuel injection timing is advanced, and conversely, the smoke emission amount decreases by retarding the fuel injection timing. The ECU 20 can calculate the retard amount of the injection timing for obtaining a desired smoke discharge amount based on the graph of FIG.

  FIGS. 7A and 7B are diagrams showing a specific method for calculating the smoke retard amount. As shown in FIG. 7A, first, it is calculated how many times the smoke emission amount has increased by the change (ΔQ) in the fuel injection amount due to deposit accumulation (the increase amount is multiplied by X times). And). Next, as shown in FIG. 7B, a curve (shown by a dotted line) obtained by multiplying a reference smoke discharge curve (shown by a solid line) by X is drawn to determine how much injection time is required to obtain a desired smoke discharge amount. (ΔT) is calculated. Here, an example is shown in which the same smoke discharge amount as that of the reference amount (1) is obtained by retarding the fuel injection timing.

  As described above, torque reduction can be suppressed by extending the fuel injection period, and smoke deterioration can be suppressed by retarding the fuel injection timing. However, when the spray deteriorates due to deposit accumulation in the injection hole portion of the injector, the smoke discharge amount increases on the contrary to increasing the fuel injection period. On the other hand, when the retard control of the fuel injection timing is performed to improve the smoke, the fuel consumption is reduced and the torque is reduced. Therefore, the fuel injection period extension control and the fuel injection timing retardation control have mutually contradictory effects, and it is necessary to use both in accordance with the situation.

  FIG. 8 is a map in which the engine rotation speed is taken on the horizontal axis and the fuel injection amount is taken on the vertical axis, and the smoke discharge amount corresponding to the operating state (load) is drawn. A region surrounded by an ellipse in the graph is a region where the smoke discharge amount is large, and a darker portion indicates a larger discharge amount. Smoke emissions are highest near the center of the map and tend to draw an ellipse that rises to the right with the area as the center.

  FIG. 9 is a map in which regions for performing the fuel injection period extension control and the fuel injection timing retardation control are determined based on FIG. A region indicated by A1 in the drawing is a region in which the fuel injection period extension control is possible. When the operating state is in this region, YES is determined in step S14 of FIG. A region indicated by A2 in the drawing is a region in which the fuel injection timing retardation control is possible, and when the operating state is in this range, it is determined YES in step S24 of FIG.

  In a region where the user can increase the fuel injection amount by an accelerator operation or the like, it is not necessary to compensate for the decrease in torque by the fuel injection period extension control. Therefore, it is preferable to limit the region in which the fuel injection period extension control is possible to a predetermined region (A1) near the limit of the fuel injection amount with respect to the engine speed. Even in the vicinity of the limit of the fuel injection amount, it is preferable not to perform the control to increase the fuel injection amount (the hatched area in the figure) because there is a risk of surge while the engine speed is small.

  With regard to smoke improvement, based on the smoke emission map in FIG. 8, the retarding control of the fuel injection timing can be controlled particularly in the region (A2) where the smoke emission amount is large, and in other regions, the retardation is retarded. It is preferable to prioritize improvement of fuel consumption (ensure torque) by not performing control. In the region where the engine speed is high and close to the full load (region where A1 and A2 overlap), it is preferable to perform both the fuel injection period extension control and the fuel injection timing retard control.

  According to the fuel injection control device of the present embodiment, the ECU 20 detects the operation state and the deposit state based on input signals from various sensors, and based on the detection result, the fuel injection period extension control and the fuel injection timing delay. At least one of corner control is performed. As shown in FIG. 9, the fuel injection period extension control is performed in the region (A1) where the ECU 20 has detected a shortage of torque, and the fuel injection timing retardation control is performed in the region (A2) where the ECU 20 has detected the deterioration of smoke. Thereby, since fuel injection control suitable for the driving state can be performed, it is possible to achieve both the securing of torque and the reduction of smoke discharge in a balanced manner.

  As described with reference to FIGS. 3 to 7, the smoke increase amount is calculated from the deposit accumulation detected by the ECU 20, and the necessary retardation amount is calculated based on the smoke increase amount. As a result, it is possible to accurately calculate the required retard amount and to suppress the deterioration in fuel consumption due to the fuel injection timing retard control. As a result, torque reduction is also suppressed to a minimum, and it becomes easier to reduce smoke while ensuring the necessary torque.

  In the present embodiment, the piezo injector 18 has been described as an example of the injector for fuel injection. However, other injectors (for example, conventionally known hydraulic pressures) can be used as long as the injector is capable of the fuel injection period and injection timing. An injector (of the formula) may be used.

  Further, in this embodiment, the example in which the delay control of the fuel injection timing (steps S24 to S30 in FIG. 3) is performed following the extension control of the fuel injection period (steps S14 to S22 in FIG. 3). The order of performing may be reversed, or the two controls may be performed in parallel.

  Note that, as described above, the ECU 20 of the present embodiment includes an operating state detecting unit that detects the operating state of the internal combustion engine, a deposit detecting unit that detects deposit accumulation in the injection hole portion of the injector, and a fuel injection based on the detection result. The control means for performing at least one of the period extension control and the fuel injection timing retard control, and the amount of increase in the smoke emission amount is calculated based on the detection result of the deposit detection means, and the fuel is calculated based on the amount of increase in the smoke emission amount. This corresponds to a calculating means for calculating a retard amount in the injection timing retard control.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Fuel tank 12 High pressure pump 14 Common rail 18 Piezo injector 20 ECU

Claims (4)

An operating state detecting means for detecting an operating state of the internal combustion engine;
Deposit detection means for detecting deposit accumulation in the injection hole of the injector;
Control means for performing at least one of fuel injection period extension control and fuel injection timing delay control based on detection results of the operating state detection means and the deposit detection means;
A fuel injection control device comprising:   The fuel injection control device according to claim 1, wherein the fuel injection period extension control is performed when the operating state detection unit detects a shortage of torque.   3. The fuel injection control device according to claim 1, wherein the fuel injection timing retardation control is performed when the operating state detection unit detects smoke deterioration.   Calculation means for calculating an increase amount of the smoke discharge amount based on the detection result of the deposit detection means and calculating a retard amount in the fuel injection timing delay control based on the increase amount of the smoke discharge amount is further provided. The fuel-injection control apparatus according to any one of claims 1 to 3.

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