JP4510704B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that is applied to, for example, a diesel engine and controls fuel injection from an injector.

  Conventionally, as a fuel injection control device for a diesel engine, a small amount of fuel is injected before main injection, which is the original fuel injection, in order to prevent deterioration of exhaust gas characteristics due to ignition delay and to reduce combustion noise. One that performs pilot injection is known, and is disclosed, for example, in Patent Document 1.

  The fuel injection control device includes a fuel pump that boosts fuel in a fuel tank, a common rail that stores high-pressure fuel supplied from the fuel pump, and fuel that is supplied from the common rail to each of a plurality of cylinders of the engine. And a plurality of injectors. The fuel injection pressure is controlled by controlling the fuel pump.

  Further, in this fuel injection control device, during transient operation of the engine, for example, during acceleration, the pilot injection amount is corrected to be increased, and is increased compared to during steady operation. Thus, by increasing the pilot injection amount, it is possible to increase the type of fire in the cylinder by pilot injection even when the injection pressure is not immediately increased due to the response delay of the fuel pump. As a result, the main injection is executed before the fire type disappears, thereby avoiding the ignition delay and reducing the combustion noise, thereby maintaining the original effect of the pilot injection.

  However, when the engine is equipped with a supercharger driven by exhaust gas, for example, immediately after the transition from steady operation to acceleration operation, a supercharging delay occurs until the supercharging pressure actually increases. Pressure cannot be obtained. In this case, since the intake amount is insufficient, combustion noise cannot be sufficiently suppressed by simply increasing the pilot injection amount as in the conventional fuel injection control device.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a fuel injection control device for an internal combustion engine that can reduce combustion noise during transient operation of the internal combustion engine. .

JP 2003-262152 A

In order to achieve the above object, the invention according to claim 1 is a fuel injection control device 1 for an internal combustion engine 3 that controls injection of fuel from an injector 7 in order to supply fuel into a cylinder 4. An operating state detecting means (ECU 2 in the embodiment (hereinafter the same in this section) ECU2) for detecting an operating state including the rotational speed NE of the internal combustion engine, and the injector is injected in accordance with the detected operating state of the internal combustion engine. Fuel injection amount calculation means (ECU2) for calculating the fuel injection amount QINJ, and fuel injection pressure setting means (ECU2) for setting the injection pressure PMAP of the fuel injected from the injector according to the detected operating state of the internal combustion engine ) and, accelerating operation state determining means for determining whether the engine is in an acceleration driving state (ECU 2, step 3 in FIG. 2, step 12) in FIG. 4, the internal combustion engine is accelerated When it is determined that the rolling state, set the injection pressure, and lower than at other accelerating operation state and the detected fuel injection pressure reducing means speed is reduced the higher (ECU 2, the high-pressure pump 10 2, step 8 in FIG. 2, and step 17) in FIG.

According to this configuration, the fuel injection amount calculating means calculates the fuel injection amount injected from the injector according to the operating state including the rotational speed of the internal combustion engine, and the fuel injection pressure setting means calculates the fuel injection. Set the pressure. Further, when the internal combustion engine is determined to be in the acceleration operation state by the acceleration operation state determination means, the set fuel injection pressure is reduced as compared to the case other than the acceleration operation state, and the detected rotational speed is The higher the value, the lower the value. For this reason, for example, when an internal combustion engine is equipped with a supercharger driven by exhaust gas, the fuel injection pressure is reduced and fuel atomization is suppressed when shifting to an acceleration operation in which a supercharger delay is likely to occur. By doing so, the combustion can be slowed down, thereby reducing the combustion noise. On the other hand, when the engine is not in the accelerated operation state, by not reducing the fuel injection pressure, the combustion is favorably performed, thereby suppressing the generation of unburned components and maintaining the exhaust gas characteristics favorably.

The invention according to claim 2, in the fuel injection control apparatus for an internal combustion engine according to claim 1, accelerating operating condition parameter indicative of the degree of change in the acceleration operation state (variation average value DerutaAPAVE, the supercharging pressure deviation DerutaPTC) a Accelerated operation state parameter detecting means (ECU2, accelerator opening sensor 32, boost pressure sensor 35) for detecting is further provided, and the fuel injection pressure reducing means reduces the injection pressure in accordance with the detected acceleration operation state parameter. An amount (correction pressure PSUB) is set (step 6 in FIG. 2 and step 15 in FIG. 4).

According to this configuration, the acceleration operating condition parameter-detecting means detects the acceleration operation state parameter representing the degree of change in the acceleration operation state of the internal combustion engine, when the internal combustion engine is in an acceleration driving state is detected acceleration operation state parameter The amount of fuel injection pressure reduction is set accordingly. Thus, according to the degree of change in the acceleration operation state, setting the amount of reduction in fuel injection pressure, for example, when the degree of change in the acceleration operation state is large, by increasing the amount of reduction in fuel injection pressure, fuel By making the injection pressure smaller, the combustion noise can be appropriately reduced according to the degree of change in the actual acceleration operation state.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows an internal combustion engine (hereinafter referred to as “engine”) 3 to which a fuel injection control device 1 according to an embodiment of the present invention is applied, an ECU 2 that controls the internal combustion engine, and the like.

  The engine 3 is, for example, a 4-cylinder diesel engine mounted on a vehicle (not shown). A combustion chamber (not shown) is formed between the piston of each cylinder 4 of the engine 3 and a cylinder head (both not shown), and an intake pipe 5 and an exhaust pipe 6 are respectively provided in the cylinder head. It is connected. Each cylinder 4 is provided with an injector 7 (only one is shown) so as to face the combustion chamber, and each injector 7 is connected to a common rail 8.

  The common rail 8 extends in the direction in which the four cylinders 4 are arranged, and is connected to a fuel tank 9. A high-pressure pump 10 (fuel injection pressure reduction means) is provided between the both 8 and 9. The high pressure pump 10 pressurizes the fuel in the fuel tank 9 and supplies it to the common rail 8. The high-pressure fuel stored in the common rail 8 is supplied to the injector 7 and injected from the injector 7 into the combustion chamber. The pressure of the fuel in the common rail 8, that is, the injection pressure of fuel injected from the injector 7 (hereinafter referred to as “fuel injection pressure”) PINJ is controlled by controlling the high-pressure pump 10 with a drive signal from the ECU 2.

  The common rail 8 is provided with a relief valve 11. The relief valve 11 is appropriately opened by the control of the ECU 2 so that the fuel pressure in the common rail 8 does not become excessive, and causes the fuel to circulate from the common rail 8 to the fuel tank 9.

  Further, the fuel injection amount QINJ and the injection timing of the injector 7 are set by the ECU 2, and the set fuel injection amount QINJ and the injection timing are obtained by the drive signal from the ECU 2 as the valve opening time and valve opening timing of the injector 7. To be controlled. Note that the above injection timing is set to be divided into pilot injection and main injection twice, and further injection may be executed during both injections or after the main injection. The set fuel injection amount QINJ is , And is appropriately distributed to each injection.

  A supercharger 21 is provided between the intake pipe 5 and the exhaust pipe 6. The supercharger 21 includes a compressor 22 and a turbine 23 provided in the intake pipe 5 and the exhaust pipe 6, respectively. The compressor wheel 22a and the turbine wheel 23a are integrally connected to each other via a shaft 24. ing. In the supercharger 21, as the turbine wheel 23 a is rotationally driven by the exhaust gas flowing in the exhaust pipe 6, the compressor wheel 22 a integrated therewith is rotationally driven, whereby the air flowing into the intake pipe 5 is driven. Is pressurized and supplied to each cylinder 4 of the engine 3.

  Further, the turbine 23 is provided with a plurality of variable vanes 23b (only two are shown) and actuators (not shown) for driving them. This actuator is controlled by a drive signal from the ECU 2 to control the opening degree of the variable vane 23b, thereby controlling the supercharging pressure PTC. In other words, the flow rate of the exhaust gas blown to the turbine wheel 23a changes depending on the opening degree of the variable vane 23b, so that the rotational speed of the turbine wheel 23a changes, and accordingly, the rotational speed of the compressor wheel 22a changes. Thus, the boost pressure PTC is controlled by the ECU 2 controlling the opening degree of the variable vane 23b.

  The engine 3 is provided with an EGR device 25 having an EGR pipe 25a and an EGR control valve 25b. The EGR pipe 25 a is connected so as to connect the downstream side of the intake pipe 5 with respect to the compressor 22 and the upstream side of the exhaust pipe 6 with respect to the turbine 23. Through this EGR pipe 25a, a part of the exhaust gas of the engine 3 circulates as EGR gas in the intake pipe 5, thereby reducing the combustion temperature in the combustion chamber, thereby reducing NOx in the exhaust gas.

  The EGR control valve 25b is composed of a linear electromagnetic valve attached to the EGR pipe 25a, and the EGR gas amount is controlled by controlling the valve lift amount linearly by a drive signal from the ECU 2.

  In addition, a magnet rotor is attached to the crankshaft of the engine 3, and a crank angle sensor 31 is configured by this magnet rotor and an MRE pickup (both not shown). The crank angle sensor 31 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston of each cylinder 4 is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke. In this example of the four-cylinder type, every 180 ° of crank angle. Is output.

The ECU 2 further receives from the vehicle speed sensor 33 a detection signal representing an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) from an accelerator opening sensor 32 ( acceleration operation state parameter detecting means). Detection signals representing vehicle speed (hereinafter referred to as “vehicle speed”) VP are output.

The common rail 8 is provided with a fuel pressure sensor 34. The fuel pressure sensor 34 detects the fuel pressure in the common rail 8, that is, the fuel injection pressure PINJ, and outputs a detection signal to the ECU 2. Further, the intake pipe 5 is provided with a supercharging pressure sensor 35 ( accelerated operation state parameter detecting means) on the downstream side of the compressor 22 of the supercharger 21. The supercharging pressure sensor 35 detects the supercharging pressure PTC in the intake pipe 5 and outputs a detection signal to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The detection signals from the various sensors 31 to 35 described above are input to the CPU after A / D conversion and shaping by the I / O interface.

In accordance with these input signals, the CPU determines the operating state of the engine 3 according to a control program stored in the ROM and the like, and in accordance with the determined operating state, the fuel injection of the injector 7, specifically, the fuel The injection amount QINJ, fuel injection pressure PINJ, and injection timing are controlled. In the present embodiment, the ECU 2 constitutes an operation state detection means, a fuel injection amount calculation means, a fuel injection pressure setting means, an acceleration operation state determination means, a fuel injection pressure reduction means, and an acceleration operation state parameter detection means. Yes.

Next, the fuel injection pressure calculation process according to the first embodiment executed by the ECU 2 will be described with reference to FIG. This process is executed in synchronization with the input of the TDC signal. First, in step 1 (illustrated as “S1”, the same applies hereinafter), the accelerator opening change ΔAP is calculated by subtracting the previous value AP _n−1 from the current value AP _n of the accelerator opening.

Next, an average value of the accelerator opening change amount ΔAP (hereinafter referred to as “change amount average value”) ΔAPAVE is calculated (step 2). Specifically, the change amount average value ΔAPAVE is calculated by the following equation (1) using the accelerator opening change amount ΔAP calculated in step 1 and the change amount average value ΔAPAVE until the previous time.
ΔAPAVE = A · ΔAP + (1−A) · ΔAPAVE (1)
Here, A is a weighting coefficient for weighting ΔAP and ΔAPAVE, and is set in a range of 0 <A <1.

  Next, it is determined whether or not the change amount average value ΔAPAVE calculated in step 2 is larger than a predetermined threshold value ΔAPREF (step 3). When the answer is YES, it is assumed that the accelerator pedal opening AP is increasing, the amount of change is large, and the acceleration operation is being performed, and the correction pressure basic value shown in FIG. 3 according to the engine speed NE and the fuel injection amount QINJ. By searching the map, the correction pressure basic value PL is calculated (step 4). This correction pressure basic value map is obtained by experimentally determining the fuel injection pressure to be reduced with respect to the unit change amount of the accelerator pedal opening AP during acceleration operation, and the result is determined according to the engine speed NE and the fuel injection amount QINJ. It is a map. The fuel injection amount QINJ is calculated by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  As shown in FIG. 3, the correction pressure basic value map is composed of four maps corresponding to different fuel injection amounts QINJ, and the correction pressure basic value PL increases as the fuel injection amount QINJ increases. In addition, the inclination with respect to the engine speed NE is set to be larger. Further, in each map, the correction pressure basic value PL is set linearly so as to increase as the engine speed NE increases. As described above, the correction pressure basic value PL is set to a larger value as the engine speed NE is higher and the fuel injection amount QINJ is larger. The larger the values NE and QINJ are, the higher the combustion pressure is. This is because it is likely to rise rapidly and a large combustion noise is likely to occur. When the fuel injection amount QINJ does not coincide with the four fuel injection pressures for which the map is set, the correction pressure basic value PL is calculated by interpolation calculation.

  On the other hand, if the answer to step 3 is NO and ΔAPAVE ≦ ΔAPREF, the correction pressure basic value PL is set to a value 0, assuming that the increase amount of the accelerator pedal opening AP is small and acceleration operation is not being performed (step 5).

In Step 6 following Step 4 or 5, the change amount average value ΔAPAVE calculated in Step 2 is multiplied by the correction pressure basic value PL set in Step 4 or 5 by the following equation (2). Then, the correction pressure PSUB (reduction amount) is calculated.
PSUB = ΔAPAVE · PL (2)

  Next, the normal injection pressure PMAP is calculated by searching a map (not shown) according to the engine speed NE and the fuel injection amount QINJ (step 7). This map is obtained by experimenting the fuel injection pressure suitable for steady operation and mapping the result according to the engine speed NE and the fuel injection amount QINJ.

  Next, the target fuel injection pressure PCMD is calculated by subtracting the correction pressure PSUB calculated in step 6 from the steady-state injection pressure PMAP calculated in step 7 (step 8), and this process ends.

  The target fuel injection pressure PCMD calculated as described above is a target of the fuel injection pressure PINJ, and the high pressure pump 10 is controlled by the ECU 2 so that the actual fuel injection pressure PINJ becomes the target fuel injection pressure PCMD. Feedback controlled.

  As described above, according to the first embodiment, when the engine 3 is accelerating, the target fuel injection pressure PCMD is reduced by the correction by the correction pressure PSUB, so that the normal injection pressure PMAP is reduced. At the time of shifting to the acceleration operation where the supercharging delay is likely to occur, the fuel injection pressure PINJ is reduced to suppress the atomization of the fuel, so that the combustion in the combustion chamber can be slowed down, thereby reducing the combustion noise. Can be reduced. Further, as the change amount average value ΔAPAVE of the accelerator opening is larger, the correction pressure PSUB is set to a larger value and the target fuel injection pressure PCMD is set to a smaller value. Therefore, depending on the degree of change in the acceleration operation state And combustion noise can be reduced appropriately. On the other hand, during steady operation other than acceleration operation, the target fuel injection pressure PCMD is set to the steady injection pressure PMAP by setting the correction pressure basic value PL to the value 0. Generation | occurrence | production of a fuel component can be suppressed and an exhaust gas characteristic can be maintained favorable.

  Next, the fuel injection pressure calculation process according to the second embodiment will be described with reference to FIG. First, in step 11, the supercharging pressure deviation ΔPTC is calculated by subtracting the supercharging pressure PTC detected by the supercharging pressure sensor 34 from the target supercharging pressure PTCCMD. The target boost pressure PTCCMD is calculated by searching a map (not shown) according to the engine speed NE and the fuel injection amount QINJ.

  Next, it is determined whether or not the supercharging pressure deviation ΔPTC calculated in step 11 is larger than a predetermined threshold value ΔPTCREF (for example, 10 kPa) (step 12). When this answer is YES, it is assumed that the supercharging pressure deviation ΔPTC is large and the supercharging delay of the supercharger 21 occurs due to the acceleration operation or the like, so that the figure depends on the engine speed NE and the fuel injection amount QINJ. The correction coefficient K is calculated by searching the correction coefficient map shown in FIG. 5 (step 13).

  As shown in FIG. 5, this correction coefficient map is composed of four maps corresponding to different fuel injection amounts QINJ, like the correction pressure basic value map of FIG. Further, for the same reason as described regarding the correction pressure basic value map of FIG. 3, the correction coefficient K is set to a larger value as the engine speed NE is larger, and as the fuel injection amount QINJ is larger. The inclination is set to a large value and the inclination with respect to the engine speed NE is further increased. If the fuel injection amount QINJ does not match the four fuel injection amounts set on the map, the correction coefficient K is calculated by interpolation calculation.

  On the other hand, when the answer to step 12 is NO and ΔPTC ≦ ΔPTCREF, the correction factor K is set to a value of 0 assuming that the supercharging pressure deviation ΔPTC is small and the supercharging delay of the supercharger 21 has not occurred (step 0). 14).

  In step 15 following step 13 or 14, the correction pressure PSUB is calculated by multiplying the boost pressure deviation ΔPTC calculated in step 11 by the correction coefficient K set in step 13 or 14.

  Next, in a manner similar to Steps 7 and 8 in FIG. 2 described above, the steady-state injection pressure PMAP is calculated (Step 16), and the target fuel injection pressure PCMD is subtracted from the correction pressure PSUB from the steady-state injection pressure PMAP. Is calculated (step 17), and this process is terminated.

  As described above, according to the second embodiment, when the deviation ΔPTC between the target supercharging pressure PTCCMD and the actual supercharging pressure PTC is large, that is, during the acceleration operation, the supercharging delay of the supercharger 21 is actually increased. Since the target fuel injection pressure PCMD is reduced below the steady-state injection pressure PMAP by the correction by the correction pressure PSUB, the combustion noise at this time can be effectively reduced. Further, as the supercharging pressure deviation ΔPTC is larger, the correction pressure PSUB is set to a larger value and the target fuel injection pressure PCMD is set to a smaller value, so that the combustion noise is appropriately set according to the degree of the supercharging delay. Can be reduced. On the other hand, during steady operation where no supercharging delay occurs, the target fuel injection pressure PCMD is set to the steady-state injection pressure PMAP as in the first embodiment, so that the exhaust gas characteristics can be maintained well.

In addition, this invention can be implemented in various aspects, without being limited to both described embodiment. For example, in the embodiment, the engine 3 is in the acceleration operation state when the average change amount ΔAPAVE of the accelerator opening exceeds the threshold value ΔAPREF or when the supercharging pressure deviation ΔPTC exceeds the threshold value ΔPTCREF. However, instead of these, when the increase amount of the fuel injection amount QINJ, the increase amount of the vehicle speed VP, or the increase amount of the engine speed NE exceeds a predetermined threshold value corresponding thereto, The fuel injection pressure may be reduced by determining that the vehicle is in the accelerated operation state. Further, each increase amount may be set as an acceleration operation state parameter, and the correction pressure PSUB may be calculated according to the parameter.

  Further, the present invention can be applied not only to a diesel engine mounted on a vehicle but also to a gasoline engine or the like. In addition, the present invention can be applied to various industrial internal combustion engines including a marine vessel propulsion engine such as an outboard motor having a crankshaft arranged in a vertical direction. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 is a diagram showing a schematic configuration of an internal combustion engine to which a fuel injection control device according to an embodiment of the present invention is applied. It is a flowchart which shows the calculation process of the fuel injection pressure by 1st Embodiment. It is an example of the correction pressure basic value map used in the calculation process of FIG. It is a flowchart which shows the calculation process of the fuel injection pressure by 2nd Embodiment. 5 is an example of a correction coefficient map used in the calculation process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection control apparatus 2 ECU (Operating state detection means, fuel injection amount calculation means, fuel injection pressure setting means,
Acceleration operation state determination means, fuel injection pressure reduction means,
Acceleration operation state parameter detection means)
3 Internal combustion engine 4 Cylinder 7 Injector 10 High pressure pump (fuel injection pressure reducing means)
21 Supercharger 31 Crank angle sensor 32 Accelerator opening sensor ( acceleration operation state parameter detection means)
35 Supercharging pressure sensor ( acceleration operation state parameter detection means)
NE engine speed
AP Accelerator opening ΔAP Accelerator opening change ΔAPAVE Accelerator opening average value ΔAPREF Threshold QINJ Fuel injection amount PINJ Fuel injection pressure
PL correction pressure basic value PSUB correction pressure (reduction amount of fuel injection pressure)
PCMD Target fuel injection pressure PTC Supercharging pressure ΔPTC Supercharging pressure deviation PTCCMD Target supercharging pressure ΔPTCREF Threshold
K correction factor

Claims (2)

A fuel injection control device for an internal combustion engine that controls injection of fuel from an injector to supply fuel into a cylinder,
An operating state detecting means for detecting an operating state including the rotational speed of the internal combustion engine;
Fuel injection amount calculating means for calculating an injection amount of fuel injected from the injector according to the detected operating state of the internal combustion engine;
Fuel injection pressure setting means for setting an injection pressure of fuel injected from the injector according to the detected operating state of the internal combustion engine;
Accelerating operation state determination means for determining whether or not the internal combustion engine is in an acceleration operation state;
Fuel injection that reduces the set injection pressure when the internal combustion engine is determined to be in the accelerated operation state as compared to when the internal combustion engine is not in the accelerated operation state and decreases as the detected rotational speed is higher Pressure reducing means;
A fuel injection control device for an internal combustion engine, comprising: The acceleration operating condition parameter detecting means for detecting an acceleration operating state parameter indicative of the degree of change in the acceleration operation state, further comprising,
2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection pressure reduction unit sets a reduction amount of the injection pressure in accordance with the detected acceleration operation state parameter.

Images