JP2010048192A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device reducing combustion noise caused by acceleration even if such a forced condition that the injection pressure of a fuel injection valve is forcibly controlled to high pressure is canceled and accelerating operation is ordered in such a high pressure condition that injection pressure is higher than target pressure. <P>SOLUTION: In this fuel injection control device, during such a forced condition that the injection pressure is controlled to the target pressure set higher than normal control or after the forced condition is canceled, if the injection pressure is higher than the target pressure and greater than or equal to an abnormal noise generation determining value (S300:Yes) and the accelerating operation is ordered with respect to an internal combustion engine (S302:Yes), pilot injection is performed before main injection if the pilot injection is not performed in the normal control based on an engine operating condition or the number of injection stages of pilot injection is increased to increase the number of injection stages of the fuel injection valve if the pilot injection is performed in the normal control (S304). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device that controls fuel injection of a fuel injection valve that injects fuel into each cylinder of an internal combustion engine.

  When the deviation amount of the actual injection amount actually injected from the fuel injection valve becomes larger than the target injection amount set based on the engine operating state, problems such as deterioration of emissions occur. Therefore, learning of the correction amount of the drive signal for instructing the fuel injection valve to inject fuel based on the difference between the target injection amount and the actual injection amount, and injection amount learning for matching the actual injection amount with the target injection amount is performed. Yes. In particular, as disclosed in Patent Documents 1 and 2, when performing a very small amount of pilot injection before the main injection that generates the main torque of the internal combustion engine, the minute injection amount can be controlled with high accuracy. Desired.

  By the way, in a common rail type diesel engine, for example, the entire operating pressure range of the common rail that supplies fuel to the fuel injection valve is divided into a plurality of pressure regions between the low pressure side and the high pressure side, and the common rail pressure is controlled to The injection amount learning is performed in the pressure region. At this time, the common rail pressure, that is, the injection pressure of the fuel injection valve, may be controlled to a target pressure that is forcibly set higher than the normal control based on the engine operating state. The normal control based on the engine operating state means that the fuel injection valve injection pressure, the injection amount, the injection timing, the pilot injection before and after the main injection, the post injection based on the engine operating state such as the engine speed, the accelerator opening, and the water temperature. When performing injection etc., it represents performing injection control, such as the number of injection stages of multistage injection.

In addition, in order to reduce smoke in the exhaust gas, the injection pressure may be controlled to a target pressure that is forcibly set higher than the normal control.
JP 2002-276444 A JP 2005-248739 A

  In this way, in the forced state where the injection pressure of the fuel injection valve is controlled to the target pressure set to a higher pressure than the normal control based on the engine operating state, for example, the accelerator is depressed and the internal combustion engine is instructed to perform an acceleration operation. Then, the forced state is canceled and the control of the injection pressure returns to the normal control.

  When returning to the normal control, the target pressure that has been forcibly set high in the forced state is normally set to a value lower than that in the forced state. On the other hand, the injection pressure, which has been controlled to be higher than the normal control following the target pressure, gradually decreases to the target pressure by controlling the pump discharge amount and the like. Therefore, while the forced state is released and the injection pressure is reduced to the target pressure, the injection pressure is in a high pressure state higher than the target pressure.

  When the forced operation is canceled and acceleration operation is performed in a high pressure state where the actual injection pressure is higher than the target pressure, sudden combustion occurs in the cylinder, and abnormal combustion noise may occur during acceleration operation. is there.

  In the above-mentioned Patent Document 1, acceleration or acceleration is achieved by adjusting the pilot injection amount and the injection interval between the pilot injection and the main injection based on the magnitude of deviation of the measured value of the oxygen concentration or oxygen amount from the target value. It describes that combustion noise generated in transient operation such as deceleration is reduced.

However, Patent Document 1 does not describe reduction of combustion noise when the acceleration operation is performed in a high pressure state where the forced state is released and the actual injection pressure is higher than the target pressure.
In order to prevent such abnormal combustion noise during acceleration operation, it is conceivable to stop fuel injection until the injection pressure substantially matches the target pressure. However, if the fuel injection is stopped even though the acceleration operation is instructed, the internal combustion engine does not perform the acceleration operation, which causes a problem that drivability is impaired.

  The present invention has been made to solve the above-described problem, and the forced state in which the injection pressure of the fuel injection valve is forcibly controlled to a high pressure is released, and the injection pressure is higher than the target pressure. An object of the present invention is to provide a fuel injection control device that reduces combustion noise caused by acceleration even when an acceleration operation is commanded.

  According to the first to third aspects of the invention, the forcible determination means that the pressure control means is forcibly higher than the normal control based on the operating state of the internal combustion engine and the pressure control means sets the target pressure to control the injection pressure. When the pressure determination means determines that the injection pressure is higher than the target pressure and the acceleration determination means determines that the acceleration operation is commanded to the internal combustion engine, the injection control means Then, it is determined that the forced state has been released, and while the injection pressure is in a high pressure state and the acceleration operation is commanded to the internal combustion engine, the number of injection stages of the fuel injection valve is increased as compared with the normal control.

  Thus, by increasing the number of injection stages in the acceleration operation that is performed in a high pressure state where the injection pressure is higher than the target pressure, the injection pressure is estimated to be released from the forced state and generate abnormal combustion noise during acceleration. In the high pressure state, the injection amount can be dispersed without injecting fuel at a time. Thereby, rapid combustion in the cylinder can be suppressed, so that combustion noise can be reduced when the acceleration operation is performed in a high pressure state where the injection pressure is higher than the target pressure.

According to the second aspect of the present invention, when increasing the number of injection stages, the injection control means performs pilot injection before the main injection or increases the number of injection stages of pilot injection.
As a result, fuel premixing is promoted in the cylinder before the main injection for generating the main torque of the internal combustion engine is performed, so that the combustion by the main injection becomes premixed combustion. As a result, rapid combustion can be suppressed.

  According to the third aspect of the invention, when the injection control means determines that the forced state is released, the injection control means sets the number of injection stages as compared with the normal control while the injection pressure is in a high pressure state and the acceleration operation is commanded to the internal combustion engine. In addition to increasing, the injection timing of the fuel injection valve is retarded compared to the normal control.

  Thus, by delaying the injection timing in addition to the increase in the number of injection stages, the fuel combustion timing can be delayed. Thereby, rapid combustion in the cylinder can be further suppressed, so that combustion noise during acceleration can be further reduced.

  According to the fourth aspect of the present invention, when the forced determination means determines that it is in the forced state, the pressure determination means determines that the injection pressure is higher than the target pressure, and the internal combustion engine is accelerated. When the acceleration determining means determines that the operation is commanded, the injection control means determines that the forced state has been released, and the normal control is performed while the injection pressure is in a high pressure state and the internal combustion engine is commanded to perform the acceleration operation. Also retards the injection timing of the fuel injection valve.

  Thus, the fuel combustion timing can be delayed by retarding the injection timing of the fuel injection valve in the acceleration operation that is performed in a high pressure state where the injection pressure is higher than the target pressure. Thereby, since the rapid combustion in a cylinder can be suppressed, the combustion sound during acceleration can be reduced.

According to the invention described in claim 5, the injection control means retards the main injection when retarding the injection timing.
By retarding the injection timing of the main injection that generates the main torque of the internal combustion engine in one combustion cycle, rapid combustion in the cylinder can be effectively suppressed.

According to the invention described in claim 6, the pressure determination means determines whether or not the injection pressure of the fuel injection valve is higher than the target pressure and is equal to or higher than a predetermined pressure.
In other words, the pressure determination means increases the pressure when the injection pressure is higher than the target pressure and the injection pressure is equal to or higher than the predetermined pressure, and sudden combustion is likely to occur in the cylinder during acceleration and abnormal noise is likely to occur. State. Thus, in a high pressure state where abnormal noise is likely to occur, it is effective for the injection control means to reduce the abnormal noise by implementing at least one of increasing the number of injection stages or retarding the injection timing. is there.

According to the invention described in claim 7, the pressure determination means determines whether or not the injection pressure of the fuel injection valve is in a high pressure state higher than a predetermined differential pressure with respect to the target pressure.
In other words, the pressure determination means has an injection pressure higher than the target pressure, and the injection pressure is higher than the target pressure by a predetermined differential pressure, and sudden combustion is likely to occur in the cylinder during acceleration. When it is likely to occur, it is in a high pressure state. Thus, in a high pressure state where abnormal noise is likely to occur, it is effective for the injection control means to reduce the abnormal noise by implementing at least one of increasing the number of injection stages or retarding the injection timing. is there.

By the way, when the combustion noise during acceleration is blocked by the running sound or the engine sound, it is not necessary to control the number of injection stages or the injection timing to reduce the combustion noise.
Therefore, according to the eighth aspect of the invention, the injection control means determines that the forced state has been released, and even if the injection pressure is in a high pressure state and the acceleration operation is commanded to the internal combustion engine, the combustion generated by the acceleration When the traveling sound determining means determines that the sound is blocked by the traveling sound, the number of fuel injection valves and the injection timing are controlled by normal control.

  According to the ninth aspect of the present invention, the injection control means determines that the forced state has been released, and even if the injection pressure is in a high pressure state and an acceleration operation is commanded to the internal combustion engine, the combustion generated by the acceleration When the engine sound determining means determines that the engine sound is blocked, the number of fuel injection valves and the injection timing are controlled by normal control.

  Thereby, in order to reduce the combustion noise generated by acceleration in a high pressure state, it is possible to prevent switching to the injection control different from the normal control and controlling the injection stage number or the injection timing. As a result, the number of times of switching the injection control can be reduced, and the processing load of the injection control can be reduced.

  According to the invention of claim 10, after the forced state is released, the injection control means determines that the pressure determination means is not in a high pressure state, or if the acceleration operation is not commanded to the internal combustion engine, the acceleration determination means Is determined, the number of injection stages and the injection timing of the fuel injection valve are controlled by normal control until the forced state determination means determines that the forced state is next.

  As a result, during the normal control from the end of the increase control of the number of injection stages to reduce the combustion noise during acceleration or the delay control of the injection timing until the next forced state starts, In order to reduce the combustion noise, it is not necessary to carry out a determination process for determining whether to increase the number of injection stages or to retard the injection timing. As a result, the processing load in normal control can be reduced.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

Embodiments of the present invention will be described below with reference to the drawings.
A fuel injection system according to an embodiment of the present invention is shown in FIG.
(Fuel injection system 10)
The fuel injection system 10 of this embodiment is for supplying fuel to, for example, a four-cylinder diesel engine (hereinafter also simply referred to as “engine”) 2 for automobiles. A high-pressure pump 12 for pressurization, a common rail 20 for storing high-pressure fuel, a fuel injection valve 30 for injecting high-pressure fuel supplied from the common rail 20 into each cylinder of the engine 2, and an electronic control unit (ECU: Electronic) for controlling this system Control Unit) 40. The high-pressure pump 12 incorporates a feed pump that pumps fuel from the fuel tank.

  The high-pressure pump 12 as a fuel supply pump is a known pump that pressurizes the fuel sucked into the pressurizing chamber from the feed pump by reciprocating the plunger as the cam of the camshaft rotates. The intake amount that the high-pressure pump 12 draws fuel from the fuel tank is controlled by a metering valve installed on the suction side of the high-pressure pump 12. The metering valve regulates the amount of fuel sucked by the high-pressure pump 12 during the suction stroke by current control. The fuel discharge amount of the high-pressure pump 12 is adjusted by adjusting the fuel intake amount.

  The fuel pressure (common rail pressure) inside the common rail 20 is determined by the balance between the amount of fuel supplied from the high-pressure pump 12 and the amount of fuel injected from the fuel injection valve 30. A pressure sensor 22 for detecting a common rail pressure is installed on the common rail 20.

  The engine 2 is provided with a crank sensor 24 that detects the rotation angle of the crank angle as a sensor that detects the operating state. Further, as other sensors for detecting the driving state, an accelerator sensor 26 for detecting an accelerator opening which is an operation amount of an accelerator pedal, a temperature for detecting the temperature of intake air (intake air temperature), and the temperature of coolant (water temperature). Sensors and the like are provided in the fuel injection system 10.

  The fuel injection valve 30 is, for example, a known injection valve that controls the lift of the nozzle needle that opens and closes the injection hole with the pressure in the control chamber. The high-pressure fuel supplied from the common rail to the control chamber of the fuel injection valve 30 applies pressure to the nozzle needle in a direction that closes the injection hole and blocks fuel injection. Then, the low pressure passage connecting the control chamber and the low pressure side is opened and closed by a solenoid valve or the like. When the low pressure passage is closed and the control chamber is at a high pressure, the nozzle needle closes the injection hole, so that fuel injection is blocked. When the low pressure passage is opened and the pressure in the control chamber is lowered, the nozzle needle is lifted and the nozzle hole is opened, so that fuel is injected from the nozzle hole.

Instead of the fuel injection valve that controls the lift of the nozzle needle with the pressure in the control chamber, a direct-acting fuel injection valve using a piezo actuator or the like may be used.
The ECU 40 as a fuel injection control device is constituted by a microcomputer 50 having a CPU 52, an FPU 54, a RAM 56, a ROM 58, an input / output interface 60, and the like. The ECU 40 A / D converts and takes in the output signals of various sensors including the pressure sensor 22, the crank sensor 24, the accelerator sensor 26, and a vehicle speed sensor (not shown) to control the engine operating state. The ECU 40 detects the rotational angle position of the crankshaft based on the output signal of the crank sensor 24, and detects the engine speed from the rotational angle of the crankshaft per unit time.

  Based on the output signals of various sensors, the ECU 40 performs multi-stage injection when performing pilot injection, post injection, etc. before and after the main injection, the discharge amount of the high pressure pump 12, the fuel injection amount of the fuel injection valve 30, the fuel injection timing, and the fuel injection timing. Control the pattern. The ECU 40 controls the injection amount of the fuel injection valve 30 based on the pulse width of the injection pulse signal that instructs the fuel injection valve 30 to inject fuel, and controls the injection timing of the fuel injection valve 30 based on the rising timing of the pulse of the injection pulse signal. .

Next, each means of the ECU 40 that functions by a control program stored in a storage device such as a ROM or a flash memory of the ECU 40 will be described.
(Pressure control means)
The ECU 40 calculates a target pressure of the common rail pressure that is the injection pressure of the fuel injection valve 30 based on the engine operating state. Then, the ECU 40 controls the discharge amount of the high-pressure pump 12 while detecting the common rail pressure with the pressure sensor 22, thereby reducing the common rail pressure in the operating pressure range that is the pressure range of the fuel that the common rail 20 supplies to the fuel injection valve 30. Control to target pressure.

(Small injection amount learning means)
For example, when a learning condition for learning a small injection amount is satisfied at every predetermined travel distance of the vehicle, the ECU 40 performs a small amount of learning injection corresponding to, for example, a pilot injection amount. The learning condition for the minute injection amount learning is, for example, when the accelerator is turned off and the deceleration no-injection operation is performed as shown in FIG. Then, the ECU 40 turns on the learning execution flag and, based on the difference between the command injection amount for learning injection and the actual injection amount, causes the fuel injection valve 30 to inject fuel into the fuel injection valve 30 so that the actual injection amount matches the command injection amount. A correction amount for correcting the pulse width of the injection pulse signal for instructing is learned. The ECU 40 calculates the generated torque from the fluctuation amount of the engine speed when the learning injection is performed, and calculates the actual injection amount actually injected by the fuel injection valve 30 from the calculated generated torque.

  The ECU 40 divides the entire operating pressure range of the common rail pressure into a plurality of pressure regions between the low pressure side and the high pressure side, adjusts the common rail pressure, and performs minute injection amount learning in each pressure region.

(Forced state determination means)
In normal control, the ECU 40 controls the injection pressure of the fuel injection valve 30 by controlling the common rail pressure to the target pressure set based on the engine operating state.

  On the other hand, when the minute injection amount learning is performed on the high pressure side of the operating pressure range of the common rail pressure, the ECU 40 performs the target pressure 200 (than the normal control based on the deceleration no-injection operation state which is the minute injection amount learning condition. (See the alternate long and short dash line in FIG. 2), and the common rail pressure, which is the injection pressure, may be forcibly controlled to be high.

Further, the ECU 40 may forcibly control the common rail pressure higher than the normal control based on the engine operating state in order to reduce smoke in the exhaust gas.
The ECU 40 determines that it is in the forced state when the common rail pressure is controlled to be higher than the normal control based on the engine operating state.

(Acceleration judgment means)
Based on the output signal of the accelerator sensor 26, the ECU 40 calculates the rate of change per unit time of the accelerator opening when the accelerator is depressed. Thus, when the accelerator opening is depressed more than a predetermined rate of change, the ECU 40 determines that the engine 2 is instructed to perform an acceleration operation.

  Further, the ECU 40 detects the torque generated by the engine 2 using a torque sensor or the like (not shown), and when the rate of change of the generated torque per unit time is equal to or greater than a predetermined rate of change, the ECU 40 is instructed to perform an acceleration operation to the engine 2. Is determined.

The ECU 40 may determine whether or not an acceleration operation is instructed to the engine 2 based on the output signals of both the accelerator sensor 26 and the torque sensor.
(Pressure judgment means)
Based on the output signal of the pressure sensor 22, the ECU 40 determines whether the common rail pressure is higher than the target pressure and higher than a predetermined pressure as the absolute pressure of the common rail pressure.

  Further, the ECU 40 determines whether or not the common rail pressure is higher than a predetermined differential pressure with respect to the target pressure as a relative pressure of the common rail pressure based on the output signal of the pressure sensor 22.

(Injection control means)
When the common rail pressure is controlled to the forced state as described above, such as learning the small injection amount or reducing the smoke in the exhaust gas, when the accelerator is depressed and the engine 2 is commanded to accelerate, the forced state is released and the fuel is controlled by normal control. The injection amount of the injection valve 30, the injection timing, the number of injection stages, and the discharge amount of the high-pressure pump 12 are controlled. For example, when the minute injection amount learning is stopped and the normal control is started, the ECU 40 calculates a pressure lower than that in the forced state by the normal control and sets it as the target pressure 200 of the common rail pressure as shown in FIG. .

  Even if the target pressure 200 decreases, the common rail pressure controlled so as to follow the target pressure by controlling the discharge amount of the high-pressure pump 12 decreases only slowly. Then, while the common rail pressure decreases to the target pressure, the injection pressure of the fuel injection valve 30 is higher than the target pressure and is equal to or higher than the predetermined pressure, or the high pressure that is higher than the predetermined differential pressure with respect to the target pressure. There will be a period of state.

  As described above, when fuel is injected from the fuel injection valve 30 in a high pressure state where the injection pressure is higher than the target pressure, sudden combustion occurs in the cylinder, and thus abnormal combustion noise may occur during acceleration operation. is there.

  Therefore, in the present embodiment, the ECU 40 suppresses rapid combustion in the cylinder and reduces combustion noise by injection control of at least one of the increase in the number of injection stages and the retard of the injection timing described below.

(1) Increase in the number of injection stages As shown in FIG. 3, the ECU 40 does not change the injection amount of the pilot injection that is performed before the main injection, and increases the number of injection stages compared to that during normal control. The pilot injection is performed so that air and a small amount of fuel are mixed in advance before ignition by the main injection. The ECU 40 does not change the injection amount and the injection timing of the main injection.

When pilot injection is not performed in normal control, the number of injection stages is increased by performing pilot injection.
By increasing the number of pilot injection stages, fuel and air premixing is promoted before the main injection, so that when the main injection is performed, the combustion in the cylinder becomes premixed combustion. As a result, sudden combustion in the cylinder is suppressed even when the main injection is performed, so that the forced state is released and the combustion noise generated when the engine 2 is accelerating in a high injection pressure state is reduced. it can.

(2) Delay of injection timing As shown in FIG. 4, the ECU 40 retards the injection timing from the normal control without changing the injection amount of the main injection. In FIG. 4, the ECU 40 does not change the injection amount and the injection timing of the pilot injection. By retarding the injection timing relative to the normal control, the fuel combustion timing can be delayed. As a result, rapid combustion in the cylinder can be suppressed, so that combustion noise during acceleration can be reduced. When retarding the injection timing, it may be retarded from the compression top dead center to suppress rapid combustion in the cylinder.

In addition, as shown in FIG. 5, you may implement simultaneously the increase in the injection stage number of pilot injection, and the retardation of the injection timing of main injection.
By the way, when either of the traveling sound determination means or the engine sound determination means described below determines that the forced state is released and the combustion sound during acceleration is blocked by the traveling sound or engine sound, The combustion noise during acceleration operation can hardly be heard due to the engine sound.

  In this case, the ECU 40 does not carry out both control of the increase in the number of pilot injection stages and the retard of the injection timing of the main injection, but performs the normal control based on the engine operating state and the number of pilot injection stages and the main injection. Control injection timing. Thereby, it is not necessary to switch to the injection control different from the normal control and increase the number of pilot injection stages or retard the injection timing of the main injection. As a result, the processing load of injection control can be reduced.

(Running sound judgment means)
Based on the output signal of the vehicle speed sensor, the ECU 40 estimates the loudness of the traveling noise such as wind noise and road noise generated by traveling the vehicle, and the combustion noise generated when the forced state is released and the acceleration operation is performed is the traveling noise. It is determined whether or not it is blocked by.

(Engine sound judgment means)
The ECU 40 detects the engine speed from the output signal of the crank sensor 24, and estimates the loudness of the engine sound generated by the engine 2 itself from the engine speed. Then, it is determined whether or not the combustion sound generated when the forced state is canceled and the acceleration operation is performed is blocked by the engine sound.

  It should be noted that the value of the predetermined pressure or the differential pressure when determining whether or not the pressure determination means is in a high pressure state is a pressure limit at which the combustion noise during acceleration increases to such an extent that the running noise or engine noise is not blocked. It may be set to a value. In this case, the predetermined pressure or the differential pressure includes the determination of the traveling sound determination means or the engine sound determination means. The value of the predetermined pressure or the differential pressure is desirably set variably based on the vehicle speed or the engine speed.

(Combustion noise reduction control)
Next, the combustion noise reduction routine shown in FIGS. 6 to 9, “S” represents a step. The combustion noise reduction routines shown in FIGS. 6 to 9 are executed in the forced state or after the forced operation is canceled by the accelerator depression or the like and the forced state is released, or the accelerated operation is almost equal to the target pressure. It is carried out until it stops. In other words, when the forced state is canceled and the injection pressure substantially matches the target pressure or the acceleration operation is stopped, the combustion noise reduction routine shown in FIGS. Not implemented. Thereby, the processing load in normal control can be reduced.

  Note that the abnormal sound occurrence determination values shown in FIGS. 6 to 9 are variable based on the vehicle speed or the engine speed so that the combustion noise during acceleration increases to the extent that the running sound or engine sound is not blocked. Is set.

(Combustion noise reduction routine 1)
In S300 of FIG. 6, the ECU 40 determines whether the injection pressure is higher than the target pressure and equal to or greater than a predetermined abnormal noise generation determination value.

If the injection pressure is equal to or greater than a predetermined abnormal noise occurrence determination value (S300: Yes), in S302, the ECU 40 determines whether or not an acceleration operation is commanded to the engine 2.
When the acceleration operation is commanded to the engine 2 (S302: Yes), in S304, the ECU 40 determines that the forced state is released and is in a high pressure state, and as described in the item of the injection control means, Pilot injection is performed before or the number of injection stages of pilot injection is increased to increase the number of injection stages of the fuel injection valve 30. Thereby, the combustion by main injection becomes premixed combustion, and rapid combustion in the cylinder can be suppressed, so that the combustion noise during acceleration is reduced.

  If the injection pressure is less than a predetermined abnormal noise occurrence determination value (S300: No) or if the engine 2 is not instructed to perform an acceleration operation (S302: No), the ECU 40 determines that the combustion noise is low, and fuel injection is performed in S306. The number of injection stages of the valve 30 is controlled to the original number of injection stages.

  Here, controlling to the original number of injection stages means that in a forced state such as learning of a small injection amount or smoke reduction, the engine is controlled to a number of injection stages suitable for a forced state that is not normal control, and when the forced state is released, the engine It represents that the number of injection stages is controlled by normal control based on the operating state.

  Here, as described above, the abnormal sound occurrence determination value determined in S300 is based on the vehicle speed or the engine speed, and the pressure value at which the combustion noise during acceleration increases to the extent that the running sound or engine sound is not blocked. Variable. As a result, when the acceleration operation is commanded to the engine 2 to cancel the forced state and normal control is performed, the frequency of switching to the increase control of the number of injection stages or the retard control of the injection timing is reduced and the number of injection stages is increased. It is possible to return to normal control as soon as possible from control or retard control of injection timing.

(Combustion noise reduction routine 2)
The processes in S310 and S312 of FIG. 7 are substantially the same as the processes in S300 and S302 of FIG.

  When the injection pressure is equal to or higher than a predetermined abnormal noise occurrence determination value (S310: Yes) and the acceleration operation is commanded to the engine 2 (S312: Yes), in S314, the ECU 40 is in a high pressure state in which the forced state is released. It is judged that there is, and as explained in the item of the injection control means, the injection timing of the main injection of the fuel injection valve 30 is retarded. Thereby, since the combustion timing of fuel can be delayed, rapid combustion in the cylinder can be suppressed. As a result, combustion noise during acceleration can be reduced.

  If the injection pressure is less than a predetermined abnormal noise occurrence determination value (S310: No) or if the engine 2 is not instructed to perform an acceleration operation (S312: No), it is determined that the combustion noise is low, and in S316, the ECU 40 performs fuel injection. The injection timing of the valve 30 is controlled to the original injection timing.

  Here, “control to the original injection timing” means that in a forced state such as learning of a small injection amount or smoke reduction, control is performed to an injection timing suitable for a forced state that is not normal control, and when the forced state is released, engine operation is performed. It represents that the injection timing is controlled by the normal control based on the state.

(Combustion noise reduction routine 3)
In S320 of FIG. 8, the ECU 40 determines whether the injection pressure is higher than the target pressure and whether the differential pressure between the injection pressure and the target pressure is greater than or equal to a predetermined abnormal noise generation determination value.

  When the differential pressure between the injection pressure and the target pressure is equal to or greater than a predetermined abnormal noise generation determination value (S320: Yes) and the engine 2 is instructed to perform an acceleration operation (S322: Yes), the ECU 40 performs the main injection in S324. The pilot injection is performed before or the number of injection stages of the pilot injection is increased to increase the number of injection stages of the fuel injection valve 30.

  When the differential pressure between the injection pressure and the target pressure is less than a predetermined abnormal noise generation determination value (S320: No), or when the engine 2 is not instructed to perform an acceleration operation (S322: No), in S326, the ECU 40 The number of injection stages of the injection valve 30 is controlled to the original number of injection stages.

(Combustion noise reduction routine 4)
In S330 of FIG. 9, the ECU 40 determines whether the injection pressure is higher than the target pressure and the differential pressure between the injection pressure and the target pressure is greater than or equal to a predetermined abnormal noise occurrence determination value.

  When the differential pressure between the injection pressure and the target pressure is equal to or greater than a predetermined abnormal noise occurrence determination value (S330: Yes), and the acceleration operation is commanded to the engine 2 (S332: Yes), in S334, the ECU 40 performs fuel injection. The injection timing of the main injection of the valve 30 is retarded.

  If the differential pressure between the injection pressure and the target pressure is less than a predetermined abnormal noise generation determination value (S330: No), or if the acceleration operation is not commanded to the engine 2 (S332: No), the ECU 40 in S336 is the fuel injection valve 30. Is controlled to the original injection timing.

  In the present embodiment described above, the forced state in which the target pressure is forcibly set higher than the normal control and the injection pressure is controlled is released, and an abnormal combustion noise is generated during acceleration when the injection pressure is higher than the target pressure. Then, in the estimated high pressure state, the number of injection stages is increased or the injection timing is retarded. Thereby, rapid combustion in the cylinder can be suppressed, so that combustion noise can be reduced when the acceleration operation is performed in a high pressure state where the injection pressure is higher than the target pressure.

[Other Embodiments]
In the above embodiment, the abnormal sound generation determination values shown in FIGS. 6 to 9 are set based on the pressure value at which the combustion noise during acceleration increases to the extent that the running sound or engine sound is not blocked, based on the vehicle speed or the engine speed. Set to variable. On the other hand, you may set a fixed value to the abnormal sound generation determination value shown in FIGS.

  In the above embodiment, the functions of the pressure control means, forced state determination means, pressure determination means, acceleration determination means, injection control means, travel sound determination means, engine sound determination means, and minute injection amount control means are specified by the control program. The ECU 40 is realized. On the other hand, at least a part of the functions of the above means may be realized by hardware whose function is specified by the circuit configuration itself.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The block diagram which shows the fuel-injection system by this embodiment. The time chart which shows the pressure change after a forced state cancellation | release. The time chart explaining the increase in the number of injection stages. The time chart explaining the retard of injection timing. The time chart explaining the increase in the number of injection stages, and the retard of injection timing. The flowchart which shows the combustion noise reduction routine 1. The flowchart which shows the combustion noise reduction routine 2. 7 is a flowchart showing a combustion noise reduction routine 3. 7 is a flowchart showing a combustion noise reduction routine 4.

Explanation of symbols

2: diesel engine (internal combustion engine), 10: fuel injection system, 20: common rail, 30: fuel injection valve, 40: ECU (fuel injection control device, pressure control means, forced state determination means, pressure determination means, acceleration determination means) Injection control means, running sound determination means, engine sound determination means, minute injection amount control means)

Claims (10)

In a fuel injection control device that controls fuel injection of a fuel injection valve that injects fuel into each cylinder of an internal combustion engine,
Pressure control means for controlling the injection pressure of the fuel injection valve to a target pressure;
Forced state determination means for determining whether or not the pressure control means is forcibly higher than normal control based on the operating state of the internal combustion engine to set the target pressure and control the injection pressure;
Pressure determining means for determining whether or not the injection pressure of the fuel injection valve is in a high pressure state higher than a target pressure;
Acceleration determining means for determining whether or not an acceleration operation is commanded to the internal combustion engine;
When the compulsory determination means determines that the engine is in the forced state, the pressure determination means determines that the pressure is in the high pressure state, and the acceleration determination means determines that an acceleration operation is commanded to the internal combustion engine. Then, it is determined that the forced state is released, and the injection pressure increases the number of injection stages of the fuel injection valve as compared with the normal control while the injection pressure is in the high pressure state and the internal combustion engine is commanded to perform the acceleration operation. Control means;
A fuel injection control device comprising:   2. The fuel injection control device according to claim 1, wherein when the number of injection stages is increased, the injection control unit performs pilot injection before main injection or increases the number of injection stages of the pilot injection. 3.   When the injection control means determines that the forced state is released, while the injection pressure is in the high pressure state and the acceleration operation is commanded to the internal combustion engine, the injection of the fuel injection valve is further performed than the normal control. 3. The fuel injection control device according to claim 1, wherein the timing is retarded. In a fuel injection control device that controls fuel injection of a fuel injection valve that injects fuel into each cylinder of an internal combustion engine,
Pressure control means for controlling the injection pressure of the fuel injection valve to a target pressure;
Forced state determination means for determining whether or not the pressure control means is forcibly higher than normal control based on the operating state of the internal combustion engine to set the target pressure and control the injection pressure;
Pressure determining means for determining whether or not the injection pressure of the fuel injection valve is in a high pressure state higher than a target pressure;
Acceleration determining means for determining whether or not an acceleration operation is commanded to the internal combustion engine;
When the compulsory determination means determines that the engine is in the forced state, the pressure determination means determines that the pressure is in the high pressure state, and the acceleration determination means determines that an acceleration operation is commanded to the internal combustion engine. Then, it is determined that the forced state has been released, and while the injection pressure is in the high pressure state and the acceleration operation is commanded to the internal combustion engine, the injection timing of the fuel injection valve is retarded relative to the normal control. Injection control means;
A fuel injection control device comprising:   The fuel injection control device according to claim 3 or 4, wherein the injection control means retards main injection when retarding the injection timing.   The said pressure determination means determines whether the injection pressure of the said fuel injection valve is a high pressure state higher than a target pressure and more than predetermined pressure, It is any one of Claim 1 to 5 characterized by the above-mentioned. Fuel injection control device.   6. The pressure determination unit according to claim 1, wherein the pressure determination unit determines whether or not an injection pressure of the fuel injection valve is in a high pressure state higher than a predetermined differential pressure with respect to a target pressure. The fuel injection control device according to item. The vehicle further includes a traveling sound determination means for determining whether the traveling sound of the vehicle blocks the combustion sound generated by acceleration,
The injection control means determines that the forced state has been released, and the traveling sound causes the combustion sound generated by acceleration even when the injection pressure is in the high pressure state and the internal combustion engine is commanded to perform acceleration operation. The fuel injection control device according to any one of claims 1 to 7, wherein when the running sound determination means determines that it is blocked, the number of injection stages and the injection timing of the fuel injection valve are controlled by the normal control. . Engine sound determining means for determining whether engine sound generated by the internal combustion engine itself blocks combustion sound generated by acceleration;
The injection control means determines that the forced state has been released, and the engine sound is detected as the combustion sound generated by acceleration even when the injection pressure is in the high pressure state and the internal combustion engine is commanded to perform acceleration operation. The fuel injection control device according to any one of claims 1 to 8, wherein when the engine sound determination means determines that it is blocked, the number of injection stages and the injection timing of the fuel injection valve are controlled by the normal control. .   The injection control means, after the forced state is released, when the pressure determination means determines that it is not in the high pressure state, or when the acceleration determination means determines that the acceleration operation is not commanded to the internal combustion engine, The number of injection stages and the injection timing of the fuel injection valve are controlled by the normal control until the forced state determination unit determines that the forced state is in the forced state. A fuel injection control device according to claim 1.

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